0001628280-24-007824 | 10-K | XBRL Viewer

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NexoBrid License and Supply Agreements (Details) - USD ($) $ in Thousands		1 Months Ended		12 Months Ended
	May 09, 2023	Feb. 28, 2023	May 31, 2019	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Purchases of intangible assets				$ 7,500	$ 0	$ 0
MediWound Ltd
Related Party Transaction [Line Items]
Consideration payment for license			$ 17,500
Contingent consideration			7,500		7,500
Milestone payments, assumed intangible assets					$ 7,500
Purchases of intangible assets		$ 7,500
Maximum contingent consideration			125,000
Sales threshold for first milestone			$ 75,000
Term of supply agreement			5 years
Renewal term of supply agreement			24 months
Supply agreement additional term			10 years
Additional funding	$ 3,000

Investments (Tables)

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Schedule of fair value of securities, not including cash

The following tables summarize the gross unrealized gains and losses of the Company’s marketable securities:


	December 31, 2023
			Gross Unrealized
(In thousands)	Amortized Cost		Gains		Losses		Credit Losses		Estimated Fair Value
Commercial paper	$	3,638	$	1	$	—	$	—	$	3,639
Corporate notes	47,228		—		(69)		—		47,159
U.S. government securities	983		—		—		—		983
U.S. government agency bonds	14,003		—		(32)		—		13,971
	$	65,852	$	1	$	(101)	$	—	$	65,752
Classified as:
Short-term investments									$	40,469
Long-term investments									25,283
									$	65,752


	December 31, 2022
			Gross Unrealized
(In thousands)	Amortized Cost		Gains		Losses		Credit Losses		Estimated Fair Value
Commercial paper	$	15,707	$	—	$	(101)	$	—	$	15,606
Corporate notes	52,159		—		(831)		—		51,328
U.S. government agency bonds	21,545		—		(46)		—		21,499
	$	89,411	$	—	$	(978)	$	—	$	88,433
Classified as:
Short-term investments									$	68,471
Long-term investments									19,962
									$	88,433

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
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-Name Accounting Standards Codification
-Section 50
-Paragraph 3
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

+ Details

Revenue

12 Months Ended

Dec. 31, 2023

Revenue from Contract with Customer [Abstract]

Revenue

Revenue Recognition and Product Sales, Net

As disclosed in Note 2, the Company recognizes product revenue from sales of MACI biopsy kits, MACI implants, Epicel grafts, and NexoBrid following the five-step model in Accounting Standards Codification 606, Revenue Recognition.

MACI Biopsy Kits

MACI biopsy kits are sold directly to hospitals and ambulatory surgical centers based on contracted rates in an approved contract or sales order. The Company recognizes MACI kit revenue upon delivery of the biopsy kit, at which time the customer (the facility) is in control of the kit. The kit is used by the doctor to provide a sample of cartilage tissue to the Company, which can later be used to manufacture a MACI implant. The ordering of the kit does not obligate the Company to manufacture an implant nor does the receipt of the cartilage tissue by the Company from the customer following biopsy. The customer’s order of an implant is separate from the process of ordering the biopsy kit. Therefore, the sale of the biopsy kit and any subsequent sale of an implant are distinct contracts and are accounted for separately.

MACI Implants

The Company contracts with two specialty pharmacies, Orsini Pharmaceutical Services, Inc. (“Orsini”) and AllCare Plus Pharmacy, Inc. (“AllCare”) to distribute MACI in a manner in which the Company retains the credit and collection risk from the end customer. The Company pays each specialty pharmacy a fee in each instance when it dispenses MACI for use in treating a patient. Both Orsini and AllCare perform collection activities to collect payment from customers. In addition, the Company sells MACI directly to hospitals pursuant to an agreed upon purchase order and to a distributor, DMS Pharmaceutical Group, Inc. (“DMS”) at a contracted rate for the treatment of patients at military facilities throughout the U.S. The Company engages a third party to provide services in connection with a patient support program to manage patient cases and to ensure that complete and correct billing information is provided to the insurers and hospitals.

Prior authorization and confirmation of coverage level by the patient’s private insurance plan, hospital or government payer is a prerequisite to the shipment of product to a patient. The Company recognizes product revenue from sales of all MACI implants upon delivery at which time the customer obtains control of the implant and the claim is billable. The total consideration that the Company expects to collect in exchange for MACI implants (the “Transaction Price”) may be fixed or

variable. Direct sales to hospitals or distributors are recorded at a contracted price, and there are typically no forms of variable consideration.

When the Company sells MACI through its specialty pharmacies, the Company is typically reimbursed by a third-party insurer or government payer, subject to a patient co-pay amount. Reimbursements from third-party insurers and government payers vary by patient and payer and are based on either contracted rates, publicly available rates, fee schedules or past payer precedents. Net product revenue is recognized net of estimated contractual allowances, which considers historical collection experience from both the payer and patient, denial rates and the terms of the Company’s contractual arrangements. The Company estimates expected collections for these transactions using the portfolio approach. The Company records a reduction to revenue at the time of sale for its estimate of the amount of consideration that will not be collected. In addition, potential credit risk exposure has been evaluated for the Company’s accounts receivable in accordance with ASC 326, Financial Instruments - Credit Losses. The Company assesses risk and determines a loss percentage by pooling accounts receivable based on similar risk characteristics. The loss percentage is calculated through the use of forecasts that are based on current and historical economic and financial information. This loss percentage was applied to the accounts receivables as of December 31, 2023. The total allowance for uncollectible consideration was $5.6 million and $6.1 million as of December 31, 2023, and 2022, respectively. Changes to the estimate of the amount of consideration that will not be collected could have a material impact on the revenue recognized. A 50 basis points change to the estimated uncollectible percentage could result in an approximately $0.4 million decrease or increase in the revenue recognized for the year ended December 31, 2023.

Changes in estimates of the Transaction Price are recorded through revenue in the period in which such change occurs. Changes in estimates related to prior periods are shown in the Revenue by Product and Customer table below and relate primarily to changes in the initial expected reimbursement or collection expectation upon completion of the billing claims process for MACI implants that occurred in a prior year.

Epicel

The Company sells Epicel directly to hospitals and burn centers based on contracted rates stated in an approved contract or purchase order. Similar to MACI, there is no obligation to manufacture Epicel grafts upon receipt of a skin biopsy, and Vericel has no contractual right to receive payment until the product is delivered to the hospital. The Company recognizes product revenue from sales of Epicel upon delivery to the hospital, at which time the customer is in control of the Epicel grafts and the claim is billable to the hospital.

NexoBrid

The Company entered into exclusive license and supply agreements with MediWound in May 2019, pursuant to which MediWound will manufacture and supply NexoBrid on a unit price basis, which may be increased pursuant to the terms of the agreements. Additionally, beginning in 2020 the U.S. Biomedical Advanced Research and Development Authority (“BARDA”) procured quantities of NexoBrid from MediWound, for use as a medical countermeasure in the event of a mass casualty emergency in the U.S. involving thermal burns. The initial, quarterly, procurement of NexoBrid by BARDA under its agreement with MediWound completed during the third quarter of 2022. The Company recognized revenue based on a percentage of gross profits for sales of NexoBrid to BARDA upon delivery, at which time BARDA was in control of the product. As of December 31, 2023, the Company did not hold a direct contract or distribution agreement with BARDA, or take title to the product procured by BARDA.

On May 9, 2023, MediWound announced BARDA’s award of additional funding under the parties’ existing agreement, $3.0 million of which will support the replacement of NexoBrid, previously procured for emergency response preparedness, which has since expired. Pursuant to the terms of the Company’s license agreement with MediWound, the Company would recognize revenue based on a percentage of gross profits, minus a percentage of net sales, on any sales of NexoBrid directly to BARDA upon delivery, pursuant to this additional award.

Additionally, on December 28, 2022, the FDA approved a BLA for NexoBrid, granting a license for commercial use in the U.S. NexoBrid is a topically-administered biological orphan product containing proteolytic enzymes, which is indicated for the removal of eschar in adults with deep partial-thickness and/or full thickness thermal burns. In September 2023, the Company announced the U.S. commercial availability of NexoBrid and subsequently commenced commercial sales of the product.

The Company sells NexoBrid to specialty distributors. These customers subsequently resell NexoBrid to hospitals and burn centers. Product revenue is recorded net of reserves for specialty distributor fees, prompt payment discounts and allowances for returns, as applicable. The Company recognizes product revenue from sales of NexoBrid when the specialty distributors take

control of the product, which typically occurs upon delivery to the specialty distributors.

Revenue by Product and Customer

The following table and descriptions below show the products from which the Company generated its revenue for the periods indicated:


	Year Ended December 31,
Revenue by product (in thousands)	2023		2022		2021
MACI implants and kits
Implants based on contracted rate sold through a specialty pharmacy (a)	$	105,948	$	81,388	$	71,969
Implants subject to third party reimbursement sold through a specialty pharmacy (b)	22,203		18,695		16,000
Implants sold direct based on contracted rates (c)	27,484		24,261		18,714
Implants sold direct subject to third-party reimbursement (d)	4,921		3,499		2,821
Biopsy kits - direct bill	2,087		2,090		2,194
Change in estimates related to prior periods (e)	2,157		2,034		(144)
Total MACI implants and kits	164,800		131,967		111,554
Epicel
Direct bill (hospital)	31,574		31,731		41,521

NexoBrid revenue (f)	1,142		667		3,109
Total revenue	$	197,516	$	164,365	$	156,184

(a) Represents implants sold through Orsini and AllCare whereby such specialty pharmacies have a direct contract with the underlying insurance provider. The amount of reimbursement is based on contracted rates at the time of sale supported by the pharmacy’s direct contracts.

(b) Represents implants sold through Orsini and AllCare whereby such specialty pharmacy does not have a direct contract with the underlying payer and are subject to third-party reimbursement. The amount of reimbursement is established based on publicly available rates, fee schedules or past payer precedents.

(c) Represents implants sold directly from the Company to the facility based on a contract and known price agreed upon prior to the surgery date. Also represents direct sales under a contract to specialty distributor DMS.

(d) Represents implants sold directly from the Company to the facility based on a contract and known price agreed upon prior to the surgery date. The payment terms are subject to third-party reimbursement from an underlying insurance provider.

(e) Primarily represents changes in estimates related to implants sold through Orsini or AllCare and relate to changes to the initial expected reimbursement or collection expectations upon completion of the billing claims process. The change in estimates is a result of additional information, changes in collection expectations or actual cash collections received in the current period.

(f) Represents commercial revenue for the year ended December 31, 2023. In the years ended December 31, 2022 and 2021, represents revenue based on a percentage of gross profits for sales of NexoBrid to BARDA, pursuant to the license agreement between the Company and MediWound (see note 14).

Concentration of Credit Risk

The Company’s total revenue and accounts receivable concentrations from a single customer consisted of the following:


For the year ended and as of	Revenue		Accounts Receivable
December 31, 2022	12	%	10	%
December 31, 2023	11	%	13	%

Income Taxes - Components of Income (Loss) Before Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
U.S.	$ (2,381)	$ (15,912)	$ (7,367)
Foreign	13	(76)	(104)
Loss before income taxes	$ (2,368)	$ (15,988)	$ (7,471)

Cover - USD ($)

12 Months Ended

Dec. 31, 2023

Feb. 21, 2024

Jun. 30, 2023

Cover [Abstract]

Document Type

10-K

Document Annual Report

true

Document Period End Date

Dec. 31, 2023

Current Fiscal Year End Date

--12-31

Document Transition Report

false

Entity File Number

001-35280

Entity Registrant Name

VERICEL CORPORATION

Entity Incorporation, State or Country Code

Entity Tax Identification Number

94-3096597

Entity Address, Address Line One

64 Sidney Street

Entity Address, City or Town

Cambridge

Entity Address, State or Province

Entity Address, Postal Zip Code

02139

City Area Code

617

Local Phone Number

588-5555

Title of 12(b) Security

Common Stock (No par value)

Trading Symbol

VCEL

Security Exchange Name

NASDAQ

Entity Well-known Seasoned Issuer

Yes

Entity Voluntary Filers

Entity Current Reporting Status

Yes

Entity Interactive Data Current

Yes

Entity Filer Category

Large Accelerated Filer

Entity Small Business

false

Entity Emerging Growth Company

false

ICFR Auditor Attestation Flag

true

Document Financial Statement Error Correction

false

Entity Shell Company

false

Entity Public Float

$ 1,774,578,732

Entity Common Stock, Shares Outstanding

48,290,164

Documents Incorporated by Reference


Document						Form 10-K Reference
Proxy Statement for the Annual Meeting of Shareholders for the fiscal year ended December 31, 2023, scheduled for May 1, 2024						Items 10, 11, 12, 13 and 14 of Part III

Entity Central Index Key

0000887359

Document Fiscal Year Focus

2023

Document Fiscal Period Focus

Amendment Flag

false

Selected Balance Sheet Components -Schedule of finite-lived intangible assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment
Total	$ 6,875	$ 7,500
Licensing Agreements
Property, Plant and Equipment
Useful Life (in years)	12 years	12 years
Cost	$ 7,500	$ 7,500
Accumulated Amortization	(625)	0
Total	$ 6,875	$ 7,500

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	$ 65,752	$ 88,433
Corporate notes
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	47,159	51,328
U.S. government agency bonds
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	13,971	21,499
U.S. government securities
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	983
Recurring
Liabilities that are measured at fair value on a recurring basis
Assets, fair value	125,552	96,172
Recurring \| Level 1
Liabilities that are measured at fair value on a recurring basis
Assets, fair value	34,672	1,262
Recurring \| Level 2
Liabilities that are measured at fair value on a recurring basis
Assets, fair value	90,880	94,910
Recurring \| Level 3
Liabilities that are measured at fair value on a recurring basis
Assets, fair value	0	0
Recurring \| Commercial Paper
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	4,876	15,606
Recurring \| Commercial Paper \| Cash and Cash Equivalents
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	1,200	8,000
Recurring \| Commercial Paper \| Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Recurring \| Commercial Paper \| Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	4,876	15,606
Recurring \| Commercial Paper \| Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Recurring \| Corporate notes
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	47,159	51,328
Recurring \| Corporate notes \| Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Recurring \| Corporate notes \| Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	47,159	51,328
Recurring \| Corporate notes \| Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Recurring \| U.S. government agency bonds
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	13,971	27,976
Recurring \| U.S. government agency bonds \| Cash and Cash Equivalents
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value		6,500
Recurring \| U.S. government agency bonds \| Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Recurring \| U.S. government agency bonds \| Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	13,971	27,976
Recurring \| U.S. government agency bonds \| Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Recurring \| U.S. government securities
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	24,874	0
Recurring \| U.S. government securities \| Cash and Cash Equivalents
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	23,900
Recurring \| U.S. government securities \| Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Recurring \| U.S. government securities \| Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	24,874	0
Recurring \| U.S. government securities \| Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Recurring \| Money market funds
Liabilities that are measured at fair value on a recurring basis
Money market funds	34,672	1,262
Recurring \| Money market funds \| Level 1
Liabilities that are measured at fair value on a recurring basis
Money market funds	34,672	1,262
Recurring \| Money market funds \| Level 2
Liabilities that are measured at fair value on a recurring basis
Money market funds	0	0
Recurring \| Money market funds \| Level 3
Liabilities that are measured at fair value on a recurring basis
Money market funds	$ 0	$ 0

Commitments and Contingencies - Narrative (Details) $ in Thousands, € in Millions	Jul. 01, 2023	Dec. 31, 2023 USD ($)	Jul. 31, 2023 EUR (€)
Commitments and Contingencies Disclosure [Abstract]
Purchase obligation, renewal option, term	3 years
Purchase obligation, automatic renewal, term	3 years
Purchase obligation, annual commitment		$ 8,271	€ 12.5
Supply agreement, term	8 years

Selected Balance Sheet Components - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment
Depreciation and amortization expense	$ 4,000,000	$ 4,000,000	$ 3,000,000
Licensing Agreements
Property, Plant and Equipment
Intangible assets	7,500,000	7,500,000
Amortization of intangible assets	$ 600,000	$ 0

Leases

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Leases

The Company leases facilities in Ann Arbor, Michigan, Cambridge, Massachusetts and Burlington, Massachusetts. The Ann Arbor facility includes office space, and the Cambridge facilities include clean rooms, laboratories for MACI and Epicel manufacturing and office space. The Company also leases offsite warehouse space and other computer-related equipment.

With respect to the Ann Arbor facility, during 2023, the Company entered into an amendment to that lease extending its term until April 30, 2025. Monthly contractual payments range from $17,000 to $18,000.

On January 28, 2022, the Company entered into a lease agreement (the “Burlington Lease”) to lease approximately 126,000 square feet of manufacturing, laboratory and office space in Burlington, Massachusetts (the “Premises”), which is currently being constructed. Once constructed, the Premises will serve as the Company’s new corporate headquarters and primary manufacturing facility.

In April 2023, in connection with the Burlington Lease, the Company entered into a construction escrow agreement (the “Construction Escrow Agreement”) with the facility’s landlord and an escrow agent. Pursuant to the terms of the Construction Escrow Agreement, in April 2023, the Company began funding, into an escrow account maintained by the escrow agent, a portion of its share of tenant improvement construction costs at the facility, which are designated as restricted cash. At the same time, the facility’s landlord began funding a portion of its tenant improvement allowance through a separate escrow account. To date, the Company has transferred into its escrow account 50% of its required cost amount, or approximately $28.3 million. The Company anticipates funding the remaining 50% of its required cost amount in early 2024.

The term of the Burlington Lease began on June 1, 2023, (the “Commencement Date”), when the Company gained control of and commenced tenant improvement work at the Premises. The Company’s obligation to pay rent for the Premises will begin on the earlier of: 13 months from the Commencement Date; or the date on which the Company first occupies the Premises to conduct operations (the “Rent Commencement Date”). The initial term of the Lease is 144 months following the Rent Commencement Date. The Company has a one-time option to extend the term of the Lease for an additional 10 years, exercisable under certain conditions and at a market rate determined in accordance with the Burlington Lease.

The annual base rent of the Burlington Lease is initially $57 per square foot per year, subject to annual increases of 2.5%. Monthly contractual payments are expected to range from $0.6 million to $0.8 million. Additionally, the Company is responsible for reimbursing the landlord for the Company’s share of the Premises’ property taxes and certain other operating expenses. The Burlington Lease also provides for a tenant improvement allowance from the landlord in an amount equal to $200 per square foot of the Premises, or approximately $24.4 million. The tenant improvement allowance will be used towards the design and construction of the tenant improvements made to the Premises, subject to the terms set forth in the Burlington Lease.

The Company was not involved in the initial construction of the core and shell of the building. On June 1, 2023, the Company gained control of the Premises to begin construction of its tenant improvements. As such, the corresponding right-of-use asset and lease liability of $35.5 million was recorded on the Company’s consolidated balance sheet. As there was not an implicit rate within the lease available, the Company estimated the incremental borrowing rate of 7.7%, based on the rate of interest the Company would have to pay to borrow a similar amount on a collateralized basis over a similar term. The lease term of 13.1 years does not include the lease extension option, as the Company is not reasonably certain to exercise that option. The Company has determined that certain improvements to the Premises are landlord-owned improvements and costs incurred for these improvements are accounted for as a variable lease payment. In the year ended December 31, 2023, the Company recorded a right-of-use asset related to landlord-owned improvements incurred of approximately $2.0 million.

In January 2022, in connection with the execution of the Burlington Lease, the Company issued a letter of credit collateralized by cash deposits of approximately $6.0 million. Subsequent to the execution of the Revolving Credit Agreement on July 29, 2022 (see Note 8, “Revolving Credit Agreement” for further details), the letter of credit is issued under the sub-facility limit of the Revolving Credit Agreement. Such letter of credit shall be reduced to approximately $4.2 million and $1.8 million at the conclusion of the third and sixth lease years, respectively, provided certain conditions set forth in the Burlington Lease are satisfied.

For the year ended December 31, 2023, 2022 and 2021, lease expense of less than $0.1 million was recorded related to short-term leases. For the years ended December 31, 2023, 2022 and 2021, the Company recognized $10.3 million, $6.9 million and $7.3 million, respectively, of operating lease expense. For the years ended December 31, 2023, 2022 and 2021, the Company recognized less than $0.1 million of financing lease expense.

Operating and finance lease assets and liabilities are as follows:


		December 31,
(In thousands)	Classification	2023		2022
Assets
Operating	Right-of-use assets	$	73,462	$	41,535
Finance	Property and equipment, net	—		37
Total leased assets		$	73,462	$	41,572
Liabilities
Current
Operating	Current portion of operating lease liabilities	$	6,187	$	4,302
Finance	Other current liabilities	—		41

Non-current
Operating	Operating lease liabilities	81,856		43,268

Total leased liabilities		$	88,043	$	47,611

Cash paid for amounts included in the measurement of the Company’s operating lease liabilities was $1.7 million, $5.3 million, and $6.0 million for the years ended December 31, 2023, 2022, and 2021, respectively.

Future minimum lease payments under non-cancellable leases as of December 31, 2023 are as follows:


(In thousands)	Total
2024	$	11,890
2025	13,677
2026	13,969
2027	14,351
2028	14,743
Thereafter	88,486
Total lease payments	$	157,116
Less: tenant improvement allowances	(20,721)
Less: interest	(48,352)
Present value of lease liabilities	$	88,043

Lease terms and discount rates are as follows:


	December 31,
	2023	2022
Weighted-average remaining lease term (years)
Operating leases	10.0	8.9
Finance leases	—	0.5
Weighted-average discount rate
Operating leases	6.8%	5.4%
Finance leases	—%	5.0%

Leases

Operating and finance lease assets and liabilities are as follows:


		December 31,
(In thousands)	Classification	2023		2022
Assets
Operating	Right-of-use assets	$	73,462	$	41,535
Finance	Property and equipment, net	—		37
Total leased assets		$	73,462	$	41,572
Liabilities
Current
Operating	Current portion of operating lease liabilities	$	6,187	$	4,302
Finance	Other current liabilities	—		41

Non-current
Operating	Operating lease liabilities	81,856		43,268

Total leased liabilities		$	88,043	$	47,611

Future minimum lease payments under non-cancellable leases as of December 31, 2023 are as follows:


(In thousands)	Total
2024	$	11,890
2025	13,677
2026	13,969
2027	14,351
2028	14,743
Thereafter	88,486
Total lease payments	$	157,116
Less: tenant improvement allowances	(20,721)
Less: interest	(48,352)
Present value of lease liabilities	$	88,043

Lease terms and discount rates are as follows:


	December 31,
	2023	2022
Weighted-average remaining lease term (years)
Operating leases	10.0	8.9
Finance leases	—	0.5
Weighted-average discount rate
Operating leases	6.8%	5.4%
Finance leases	—%	5.0%

Revolving Credit Agreement	12 Months Ended
Revolving Credit Agreement	Dec. 31, 2023
Debt Disclosure [Abstract]
Revolving Credit Agreement	Revolving Credit Agreement On July 29, 2022, the Company, as borrower, entered into a $150.0 million five-year senior secured revolving credit agreement by and among the Company, the other loan parties thereto, the lenders party thereto, and JPMorgan Chase Bank, N.A., as the administrative agent (the “Revolving Credit Agreement”). The Revolving Credit Agreement includes a $15.0 million sub-facility for the issuance of letters of credit, of which the Company is utilizing approximately $6.2 million. Amounts available under the Revolving Credit Agreement are for the working capital needs and other general corporate purposes of the Company. The Company incurred and capitalized approximately $1.1 million of debt issuance costs related to the Revolving Credit Agreement. Outstanding borrowings under the Revolving Credit Agreement bear interest, with pricing based from time to time at the Company’s election at (i) the Secured Overnight Financing Rate (“SOFR”) plus 0.10% plus a spread ranging from 1.25% to 2.50% as determined by the Company’s Total Net Leverage Ratio (as defined in the Revolving Credit Agreement) or (ii) the alternative base rate (as defined in the Revolving Credit Agreement) plus a spread ranging from 0.25% to 1.50% as determined by the Company’s Total Net Leverage Ratio. The Revolving Credit Agreement also includes a commitment fee, which ranges from 0.20% to 0.25% as determined by the Company’s Total Net Leverage Ratio. The Company is permitted to voluntarily prepay borrowings under the Revolving Credit Agreement, in whole or in part, without premium or penalty. On any business day on which the total amount of outstanding Revolving Loans (as defined in the Revolving Credit Agreement) and letters of credit exceeds the total Revolving Commitments (as defined in the Revolving Credit Agreement), the Company must prepay the Revolving Loans in an amount equal to such excess. As of December 31, 2023, there are no outstanding borrowings under the Revolving Credit Agreement. The Revolving Credit Agreement contains a number of affirmative, negative, reporting and financial covenants, in each case subject to certain exceptions and materiality thresholds. The Revolving Credit Agreement requires the Company to be in quarterly compliance, measured on a trailing four quarter basis, with a financial covenant. The maximum Total Net Leverage Ratio (as defined in the Revolving Credit Agreement is 3.50 to 1.00. The Company may elect to increase the maximum Total Net Leverage Ratio to 4.00 to 1.00 for a period of four consecutive quarters in connection with a Permitted Acquisition (as defined in the Revolving Credit Agreement). The Revolving Credit Agreement contains usual and customary restrictions on the ability of the Company and its subsidiaries to: (i) incur additional indebtedness (ii) create liens; (iii) consolidate, merge, sell or otherwise dispose of all, or substantially all, of its assets; (iv) sell certain assets; (v) pay dividends on, repurchase or make distributions in respect of capital stock or make other restricted payments; (vi) make certain investments; (vii) repay subordinated indebtedness prior to stated maturity; and (viii) enter into certain transactions with its affiliates. Obligations under the Revolving Credit Agreement are secured by first priority liens over substantially all of the assets of Vericel Corporation, excluding certain subsidiaries (subject to customary exclusions set forth in the Revolving Credit Agreement and the other transaction documents).

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//470/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements have been prepared in accordance with U.S. GAAP. The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and accounts have been eliminated in consolidation. Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. The more significant estimates reflected in the Company’s consolidated financial statements include, but are not limited to, certain judgments regarding revenue recognition, inventory valuation, stock option valuation, lease valuation, deferred tax assets and liabilities and accrued expenses. The Company is not aware of any specific event or circumstance that would require an update to its estimates or judgments reflected in these consolidated financial statements or a revision of the carrying value of its assets or liabilities as of the issuance of these consolidated financial statements. These estimates may change as new events occur and additional information is obtained. Actual results could materially differ from those estimates. Cash Equivalents Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less from the date of purchase and consist primarily of demand deposits, money market funds, U.S. government securities, U.S. government agency bonds and commercial paper. Restricted Cash Restricted cash as of December 31, 2023, represents amounts in a construction escrow account. See Note 5, “Leases” for further discussion. Investments Investments classified as short-term have maturities of less than one year. Investments classified as long-term are those that: (i) have a maturity of greater than one year, and (ii) the Company does not intend to liquidate within the next twelve months, although these funds are available for use and, therefore, are classified as available-for-sale. The Company’s investment strategy is to buy short-duration marketable securities with a high credit rating. As of December 31, 2023 and 2022, all marketable securities held by the Company had remaining contractual maturities of three years or less. Unrealized gains are included as a component of accumulated other comprehensive income in the consolidated balance sheets and consolidated statements of shareholders’ equity and a component of total comprehensive (loss) income in the consolidated statements of comprehensive (loss) income, until realized. Unrealized losses are evaluated for impairment under ASC 326, Financial Instruments - Credit Losses (“ASC 326”), to determine if the impairment is credit-related or non-credit-related. Credit-related impairment is recognized as an allowance on the balance sheet with a corresponding adjustment to earnings, and non-credit-related impairment is recognized in other comprehensive (loss) income, net of taxes. Leases The Company determines if an arrangement is a lease at inception, in accordance with ASC Topic 842, Leases. All operating lease commitments with a lease term greater than 12 months are recognized as right-of-use assets and liabilities, on a discounted basis on the balance sheet. Leases with an initial term of 12 months or less are not recorded on the balance sheet. Certain of the Company’s lease agreements include lease payments that are adjusted periodically for an index or rate. The leases are initially measured using the present value of the projected payments adjusted for the index or rate in effect at the commencement date. In addition to rent, the leases may require the Company to pay additional amounts for taxes, insurance, maintenance and other expenses, which do not transfer a good or service to the Company and are generally referred to as non-lease components. Variable non-lease components are not measured as part of the right-of-use asset and liability. Only when lease components and their associated non-lease components are fixed are they accounted for as a single lease component and are recognized as part of a right-of-use asset and liability. The Company’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. The Company has options to renew lease terms for facilities and other assets. Some leases contain clauses for renewal at the Company’s option with renewal terms that generally extend the lease term from 1 to 10 years. The exercise of lease renewal options is generally at the Company’s sole discretion. The Company evaluates renewal and termination options at the lease commencement date to determine if it is reasonably certain to exercise the option on the basis of economic factors. Certain lease agreements contain options to terminate the lease. A portfolio approach is applied to certain lease contracts with similar characteristics. The Company uses a discount rate to calculate the present value of lease payments in order to determine lease classification and measurement of the lease asset and liability. In the absence of a rate of interest that is readily determinable in the contract, the Company estimates the incremental borrowing rate (“IBR”) for each lease based on the information available at commencement. The IBR reflects the rate of interest that the Company would pay on the lease commencement date to borrow an amount equal to the lease payments on a collateralized basis over a similar term in similar economic environments. Inventory Inventories are measured at the lower of cost or net realizable value. Cost is calculated based upon standard-cost which approximates costs determined on the first-in, first-out method. The Company periodically reviews its inventories for excess or obsolescence and writes down obsolete or other unmarketable inventory to its estimated net realizable value. If the actual net realizable value is less than that estimated by the Company, or if it is determined that inventory utilization will further diminish based on estimates of demand, additional inventory write-downs may be required. In all cases, product inventory is carried at the lower of cost or its estimated net realizable value. Amounts written down are charged to cost of product sales. Accounts Receivable Accounts receivable are initially recorded at the contractual amount owed by the customer or based on expected payments from the insurance provider, hospital or patient. Allowances for doubtful accounts are established when the facts and circumstances indicate that a receivable may not be collectible. Potential credit risk exposure has been evaluated for the Company’s accounts receivable in accordance with ASC 326. The Company assesses risk and determines a loss percentage by pooling accounts receivable based on similar risk characteristics. The loss percentage is calculated through the use of forecasts that are based on current and historical economic and financial information. Property and Equipment, net Property and equipment are initially measured and recognized at acquisition cost, including any directly attributable cost of preparing the asset for its intended use. After initial measurement, property and equipment are carried at cost less accumulated depreciation. Repair and maintenance costs of property and equipment are expensed as incurred. The depreciable value of property and equipment is depreciated on a straight-line basis over the useful life of the asset. The useful life of an asset is usually equivalent to its economic life. The useful lives of property and equipment are as follows: •Machinery and equipment: 3 to 10 years •Furniture, fixtures and office equipment: 5 years •Computer equipment and software: 3 years •Leasehold improvements: shorter of the remaining life of the lease or 15 years The costs of assets retired or otherwise disposed of and the accumulated depreciation thereon are removed from the accounts, with any gain or loss realized upon sale or disposal credited or charged to operations. Intangible Assets, net The Company amortizes its intangible assets on a straight-line basis over their estimated economic lives, unless another amortization method is deemed to be more appropriate. In determining the useful lives of intangible assets, the Company considers the expected use of the assets and the effects of obsolescence, demand, competition, anticipated technological advances, market influence and other economic factors. Long-Lived Assets The Company evaluates long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be fully recoverable. No impairment was identified or recorded during the years ended December 31, 2023, 2022 and 2021. Revenue Recognition The Company recognizes product revenue from sales to a customer following the five step model in Accounting Standards Codification 606, Revenue Recognition (“ASC 606”): (i) identify contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenues when (or as) the Company satisfies the performance obligation. Under this revenue standard, the Company recognizes revenue when its customer obtains control of the promised goods, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods. There are no contractual rights of returns, refunds or similar obligations related to MACI, MACI biopsy kits or Epicel; however, in certain limited cases the Company will accept a product return if a surgery is canceled. Revenue is not recognized in certain canceled cases. There are limited contractual rights of returns, refunds, or similar obligations related to NexoBrid. For MACI, MACI biopsy kits, Epicel and NexoBrid, there are no variable pricing arrangements related to warranties or rebates offered to customers. The majority of orders are due within 30 to 90 days of delivery. Shipping and handling fees are included as a component of revenue. The Company recognizes any commission fees as an expense when incurred. These fees are included in selling, general, and administrative expenses. See Note 3, “Revenue” for further discussion on revenues. Research and Development Expense Research and development expenses are expensed as incurred. These expenditures relate to the development of new products, improvement of existing products, technical support of products and compliance with governmental regulations for the protection of consumers and patients. Stock-Based Compensation The Company’s accounting for stock-based compensation requires it to determine the fair value of common stock issued in the form of stock option awards and restricted stock units. The fair value of restricted stock units held by employees and non-employee directors is determined based on the fair value of the Company’s common stock on the date of the grant. Compensation expense is recorded for restricted stock units that are expected to vest over the expected vesting period. The fair value of stock options held by employees and non-employee directors is determined using a Black-Scholes option valuation method. Key assumptions in determining fair value include volatility, risk-free interest rate, dividend yield and expected term. The assumptions used in calculating the fair value of stock options represent the Company’s best estimates; however, these estimates involve inherent uncertainties and the application of management’s judgment. As a result, if factors change and different assumptions are used, the stock-based compensation expense could be materially different in the future. In addition, the Company estimates the expected forfeiture rate and only recognizes expense for those stock options expected to vest over the service period. The estimated forfeiture rate considers the historical experience of the Company’s stock-based awards. If the actual forfeiture rate is different from the estimate, expense is adjusted accordingly. The Company records the expense for stock options and restricted stock units using a graded-vesting attribution method. The Company also has an Employee Stock Purchase Plan (“ESPP”) which is a compensatory plan. Compensation expense is recorded based on the fair value of the purchased options at the grant date, which corresponds to the first day of each purchase period, and is amortized over the purchase period. Comprehensive (Loss) Income Comprehensive (loss) income is the change in shareholders’ equity during a period arising from unrealized gains or losses related to the Company’s investments. Income Taxes Deferred tax assets are recognized for deductible temporary differences and tax credit carryforwards and deferred tax liabilities are recognized for taxable temporary differences. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion or all of the deferred tax assets will not be realized based on the weight of available evidence. When evaluating the realizability of the deferred tax assets, all evidence, both positive and negative, is considered. Items considered when evaluating the need for a valuation allowance include the ability to carry back losses, future reversals of existing temporary differences, tax planning strategies, and expectations of future earnings. The Company records uncertain tax positions in the consolidated financial statements only if it is more likely than not that the uncertain tax position will be sustained upon examination by the taxing authorities. The Company records interest and penalties related to uncertain tax positions in income tax expense. Net (Loss) Income Per Common Share Basic earnings per common share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period. Diluted earnings per common share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period, plus the potential dilutive effect of other securities if those securities were converted or exercised. During periods in which the Company incurs net losses, both basic and diluted loss per common share is calculated by dividing the net loss by the weighted-average shares of common stock outstanding and potentially dilutive securities are excluded from the calculation because their effect would be antidilutive. Financial Instruments The Company’s financial instruments include accounts receivables, accounts payable and accrued expenses for which the current carrying amounts approximate market value, based upon their short-term nature and marketable debt securities which are classified as available-for-sale and carried at fair value on a settlement date basis. Recent Accounting Pronouncements No new accounting standards were adopted during the year ended December 31, 2023. The Company considers the applicability and impact of any recent Accounting Standards Updates (“ASUs”) issued by the Financial Accounting Standards Board (“FASB”), as noted below. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, to improve reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. The disclosure requirements must be applied retrospectively to all prior periods presented in the financial statements. The effective date for the standard is for fiscal years beginning after December 15, 2023 and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the effects adoption of this guidance will have on the consolidated financial statements. In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures, to provide more detailed income tax disclosure requirements. The guidance requires entities to disclose disaggregated information about their effective tax rate reconciliation as well as information on income taxes paid. The disclosure requirements will be applied on a prospective basis, with the option to apply it retrospectively. The effective date for the standard is for fiscal years beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the effects adoption of this guidance will have on the consolidated financial statements.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Legal Proceedings

From time-to-time, the Company could be a party to various legal proceedings arising in the ordinary course of business. The costs and outcome of litigation, regulatory, investigatory or other proceedings cannot be predicted with certainty, and some lawsuits, claims, actions or proceedings may be disposed of unfavorably to the Company and could have a material adverse effect on the Company’s results of operations or financial condition. In addition, intellectual property disputes often have a risk of injunctive relief which, if imposed against the Company, could materially and adversely affect its financial condition or results of operations. If a matter is both probable to result in material liability and the amount of loss can be reasonably estimated, the Company estimates and discloses the possible material loss or range of loss. If such loss is not probable or cannot be reasonably estimated, a liability is not recorded in its consolidated financial statements.

As of December 31, 2023, the Company had no material ongoing litigation in which the Company was a party or any material ongoing regulatory or other proceedings and had no knowledge of any investigations by government or regulatory authorities in which the Company is a target that could have a material adverse effect on its current business.

Manufacturing and Supply Agreements

Matricel — On July 1, 2023, the Company renewed its long-term supply agreement with Matricel GmbH (“Matricel”) for the supply of ACI-Maix collagen membranes used in the manufacture of MACI (the “Matricel Supply Agreement”). In the event Matricel is unable to supply the membranes, the Company may license the technology and procure the membranes from another source. The Matricel Supply Agreement provides that Matricel shall supply the ACI-Maix membranes exclusively to the Company during the term of the agreement. The Matricel Supply Agreement is effective until December 31, 2030, with an option to extend its term for three additional years to December 31, 2033. Thereafter, the Matricel Supply Agreement may be renewed for additional three-year periods. Under the terms of the Matricel Supply Agreement, the Company has committed to annual minimum purchase values totaling approximately €12.5 million over the eight-year term.

Manufacture, Supply and Other Agreements — The Company has entered into various agreements relating to the manufacture of its products and the supply of certain components. If the manufacturing or supply agreements expire or are

otherwise terminated, the Company may not be able to identify and obtain ancillary materials that are necessary to develop its products and such expiration and termination could have a material effect on the Company’s business.

The Company’s purchase commitments consist of minimum purchase amounts of raw materials and finished goods used in the Company’s cell manufacturing process to manufacture its marketed cell therapy products. In addition, the Company also pays for usage of offsite warehouse space.

Future minimum purchase commitments related to the Company’s contractual obligations are as follows:


			Payments Due by Period
Contractual Obligations (In thousands)	Total		2024		2025		2026		2027		2028		More than 5 Years
Purchase commitments	$	19,329	$	8,271	$	1,512	$	1,611	$	1,909	$	2,009	$	4,017
Warehouse operating agreement	3,795		1,850		746		788		411		—		—
Total	$	23,124	$	10,121	$	2,258	$	2,399	$	2,320	$	2,009	$	4,017

Stock-Based Compensation - Schedule of restricted stock awards activity (Details) - Restricted stock units - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Number of Restricted Stock Units
Outstanding at beginning of period (in shares)	648,174
Granted (in shares)	564,449
Vested (in shares)	(224,142)
Forfeited (in shares)	(57,545)
Unvested at end of period (in shares)	930,936	648,174
Weighted-Average Grant Date Fair Value
Unvested at beginning of period (in USD per share)	$ 34.86
Granted (in USD per share)	30.36	$ 33.71	$ 52.07
Vested (in USD per share)	32.34
Forfeited (in USD per share)	33.01
Unvested at end of period (in USD per share)	$ 32.85	$ 34.86

Selected Balance Sheet Components - Schedule of inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Inventory:
Raw materials	$ 11,348	$ 15,101
Work-in-process	1,210	832
Finished goods	529	53
Total inventory	$ 13,087	$ 15,986

Employee Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
Employee Savings Plan (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Contributions made under 401(k) savings plan	$ 1.2	$ 1.1	$ 1.0

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Statement [Abstract]
Revenue, Product and Service [Extensible List]	Product [Member]	Product [Member]	Product [Member]
Product sales, net	$ 197,516	$ 163,698	$ 153,075
Other revenue	0	667	3,109
Total revenue	$ 197,516	$ 164,365	$ 156,184
Cost, Product and Service [Extensible List]	Product [Member]	Product [Member]	Product [Member]
Cost of product sales	$ 61,940	$ 54,577	$ 50,159
Gross profit	135,576	109,788	106,025
Research and development	21,042	19,943	16,287
Selling, general and administrative	120,998	106,903	97,592
Total operating expenses	142,040	126,846	113,879
Loss from operations	(6,464)	(17,058)	(7,854)
Other income (expense):
Interest income	4,632	1,341	224
Interest expense	(600)	(366)	(4)
Other income	64	95	52
Total other income	4,096	1,070	272
Loss before income taxes	(2,368)	(15,988)	(7,582)
Income tax expense (benefit)	814	721	(111)
Net loss	$ (3,182)	$ (16,709)	$ (7,471)
Net loss per common share:
Basic (in USD per share)	$ (0.07)	$ (0.35)	$ (0.16)
Diluted (in USD per share)	$ (0.07)	$ (0.35)	$ (0.16)
Weighted-average common shares outstanding:
Basic (in shares)	47,590	47,130	46,472
Diluted (in shares)	47,590	47,130	46,472

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Summary of components of (loss) income before income taxes

The components of loss before income taxes are summarized as follows:


	Year Ended December 31,
(In thousands)	2023		2022		2021
U.S.	$	(2,381)	$	(15,912)	$	(7,367)
Foreign	13		(76)		(104)
Loss before income taxes	$	(2,368)	$	(15,988)	$	(7,471)

Schedule of reconciliation of income taxes computed using the federal statutory rate to the taxes reported in consolidated statements of operations

A reconciliation of income taxes computed using the U.S. federal statutory rate to the taxes reported in the consolidated statements of operations is as follows:


	Year Ended December 31,
(In thousands)	2023			2022			2021
Loss before income taxes	$	(2,368)		$	(15,988)		$	(7,471)
Federal statutory rate	21		%	21		%	21		%
Taxes computed at federal statutory rate	(497)			(3,357)			(1,569)
State and local income taxes	(389)			(630)			(345)
Nondeductible stock-based compensation	(586)			1,168			(4,311)
Federal and state rate change	(704)			574			47
Research and orphan drug credits	362			(644)			(413)
Other	162			267			(87)
Change in valuation allowance	2,466			3,343			6,567
Reported income taxes	$	814		$	721		$	(111)

Schedule of deferred tax assets and liabilities

Deferred tax assets (liabilities) consist of the following:


	Year Ended December 31,
(In thousands)	2023		2022
Deferred tax assets:
Net operating loss carryforwards	$	4,505	$	7,020
Employee benefits and stock-based compensation	24,812		18,028
Research and development costs	5,176		7,530
Intangible assets	962		1,770
Operating lease liabilities	20,849		11,846
Inventory reserve	3,570		2,780
Tax credit carryforward	10,781		11,143
Other, net	12		12
Total deferred tax assets	70,667		60,129
Less: valuation allowance	(49,755)		(47,290)
Total net deferred tax assets	20,912		12,839
Deferred tax liabilities:
Right-of-use assets	(19,296)		(10,891)
Property and equipment, net	(1,616)		(1,948)
Total net deferred tax liabilities	(20,912)		(12,839)
Net deferred tax assets and liabilities	$	—	$	—

Selected Balance Sheet Components - Schedule of property and equipment, net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property and equipment, net:
Financing right-of-use lease	$ 0	$ 37
Total property and equipment, gross	63,841	34,139
Less accumulated depreciation	(22,206)	(18,302)
Total property and equipment, net	41,635	15,837
Machinery and equipment
Property and equipment, net:
Total property and equipment, gross	5,562	5,041
Furniture, fixtures and office equipment
Property and equipment, net:
Total property and equipment, gross	1,731	1,710
Computer equipment and software
Property and equipment, net:
Total property and equipment, gross	9,116	8,224
Leasehold improvements
Property and equipment, net:
Total property and equipment, gross	14,901	13,689
Construction in process
Property and equipment, net:
Total property and equipment, gross	$ 32,531	$ 5,438

Leases - Lease Term and Discount Rate (Details)	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Weighted-average remaining lease term - Operating lease term	10 years	8 years 10 months 24 days
Weighted-average remaining lease term - Finance lease term	0 years	6 months
Weighted-average discount rate - Operating lease discount rate	6.80%	5.40%
Weighted-average discount rate - Finance lease discount rate	0.00%	5.00%

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities:
Net loss	$ (3,182)	$ (16,709)	$ (7,471)
Adjustments to reconcile net loss to net cash flows from operating activities:
Depreciation and amortization expense	4,632	3,981	2,965
Stock-based compensation expense	32,325	37,183	34,322
Amortization of premiums and discounts on marketable securities	(824)	107	949
Amortization of debt issuance costs	215	90	0
Non-cash lease costs	6,070	4,222	4,422
Other	39	22	7
Changes in operating assets and liabilities:
Inventory	2,899	(2,605)	(4,025)
Accounts receivable	(11,817)	(9,102)	(2,933)
Other current assets	(1,733)	(557)	(353)
Accounts payable	3,049	1,437	1,491
Accrued expenses	1,025	2,145	2,752
Operating lease liabilities	2,513	(2,527)	(3,086)
Other non-current assets and liabilities, net	100	0	0
Net cash provided by operating activities	35,311	17,687	29,040
Investing activities:
Purchases of investments	(55,225)	(69,554)	(60,021)
Sales and maturities of investments	79,608	40,944	64,435
Expenditures for property and equipment	(20,013)	(7,596)	(7,915)
Purchases of intangible assets	(7,500)	0	0
Net cash used in investing activities	(3,130)	(36,206)	(3,501)
Financing activities:
Net proceeds from common stock issuance	6,000	3,652	11,184
Debt issuance costs	0	(1,076)	0
Payments on employee's behalf for taxes related to vesting of restricted stock unit awards	(2,341)	(1,492)	(1,665)
Other	(41)	(39)	(348)
Net cash provided by financing activities	3,618	1,045	9,171
Net increase (decrease) in cash, cash equivalents, and restricted cash	35,799	(17,474)	34,710
Cash, cash equivalents, and restricted cash at beginning of period	51,067	68,541	33,831
Cash, cash equivalents, and restricted cash at end of period	86,866	51,067	68,541
Supplemental disclosure of cash flow information:
Right-of-use asset and lease liability recognized	37,960	137	192
Additions to property and equipment and intangible assets included in accounts payable	10,152	7,824	1,373
Restricted stock held for employee tax remittance included in accounts payable	0	0	46
Interest paid	383	109	4
Taxes paid	1,166	0	379
Reconciliation of amounts within the consolidated balance sheets:
Cash and cash equivalents	69,088	51,067	68,330
Restricted cash	17,778	0	211
Total cash, cash equivalents, and restricted cash at end of period	$ 86,866	$ 51,067	$ 68,541

Stock-Based Compensation - Schedule of activity for service-based stock options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Options
Outstanding at the beginning of the period (in shares)	6,609,147
Granted (in shares)	607,947
Exercised (in shares)	(377,597)
Expired (in shares)	(41,004)
Forfeited (in shares)	(81,807)
Outstanding at the end of the period (in shares)	6,716,686	6,609,147
Exercisable at the end of the period (in shares)	4,967,797
Weighted Average Exercise Price
Outstanding at the beginning of the period (in USD per share)	$ 24.89
Granted (in USD per share)	30.90
Exercised (in USD per share)	12.55
Expired (in USD per share)	45.21
Forfeited (in USD per share)	37.96
Outstanding at the end of the period (in USD per share)	25.85	$ 24.89
Exercisable at the end of the period (in USD per share)	$ 22.16
Weighted Average Remaining Contractual Term
Outstanding	6 years 1 month 28 days	6 years 9 months 18 days
Exercisable at end of period	5 years 5 months 12 days
Aggregate Intrinsic Value
Outstanding	$ 88,387	$ 56,708
Exercisable at end of period	$ 82,288

Shareholder's Equity	12 Months Ended
Shareholder's Equity	Dec. 31, 2023
Stockholders' Equity Note [Abstract]
Shareholder's Equity	Shareholder’s Equity At-the-Market Offering On August 27, 2021, the Company entered into a Sales Agreement with Leerink Partners (f/k/a SVB Leerink LLC), as sales agent, pursuant to which it may offer and sell up to $200.0 million of shares of the Company’s common stock, no par value per share (“ATM Shares”). The ATM Shares to be offered and sold under the Sales Agreement will be issued and sold pursuant to an automatically effective shelf registration statement on Form S-3ASR (File No. 333-259119) filed by the Company on August 27, 2021, which expires three years from the filing date. The Company also filed a prospectus supplement relating to the offering and sale of the ATM Shares on August 27, 2021. The Company is not obligated to make any sales of ATM Shares, and Leerink Partners is not required to sell any specific number or dollar amount of the ATM Shares under the Sales Agreement. The Company capitalized certain legal, professional accounting and other third-party fees that were directly associated with in-process stock financings as deferred offering costs until such financings are consummated. As of December 31, 2023, the Company has sold no shares pursuant to the Sales Agreement.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481004/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-16

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

+ Details

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 43	$ 47
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	47,829,000	47,253,000
Common stock, shares outstanding (in shares)	47,829,000	47,253,000

Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment
Impairment of long-lived asset	$ 0	$ 0	$ 0
Furniture, fixtures and office equipment
Property, Plant and Equipment
Useful lives (in years)	5 years
Computer equipment and software
Property, Plant and Equipment
Useful lives (in years)	3 years
Leasehold improvements
Property, Plant and Equipment
Useful lives (in years)	15 years
Minimum
Property, Plant and Equipment
Duration of lease renewal terms	1 year
Minimum \| Machinery and equipment
Property, Plant and Equipment
Useful lives (in years)	3 years
Maximum
Property, Plant and Equipment
Duration of lease renewal terms	10 years
Maximum \| Machinery and equipment
Property, Plant and Equipment
Useful lives (in years)	10 years

Investments

12 Months Ended

Dec. 31, 2023

Investments, Debt and Equity Securities [Abstract]

Investments

Marketable debt securities held by the Company are classified as available-for-sale pursuant to ASC 320, Investments – Debt and Equity Securities, and carried at fair value in the accompanying consolidated balance sheets on a settlement date basis. The following tables summarize the gross unrealized gains and losses of the Company’s marketable securities:


	December 31, 2023
			Gross Unrealized
(In thousands)	Amortized Cost		Gains		Losses		Credit Losses		Estimated Fair Value
Commercial paper	$	3,638	$	1	$	—	$	—	$	3,639
Corporate notes	47,228		—		(69)		—		47,159
U.S. government securities	983		—		—		—		983
U.S. government agency bonds	14,003		—		(32)		—		13,971
	$	65,852	$	1	$	(101)	$	—	$	65,752
Classified as:
Short-term investments									$	40,469
Long-term investments									25,283
									$	65,752


	December 31, 2022
			Gross Unrealized
(In thousands)	Amortized Cost		Gains		Losses		Credit Losses		Estimated Fair Value
Commercial paper	$	15,707	$	—	$	(101)	$	—	$	15,606
Corporate notes	52,159		—		(831)		—		51,328
U.S. government agency bonds	21,545		—		(46)		—		21,499
	$	89,411	$	—	$	(978)	$	—	$	88,433
Classified as:
Short-term investments									$	68,471
Long-term investments									19,962
									$	88,433

There have been no impairments of the Company’s assets measured and carried at fair value during the years ended December 31, 2023 or 2022.

Net Loss Per Common Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss Per Common Share

A summary of net loss per common share is presented below:


	Year Ended December 31,
(Amounts in thousands, except per share amounts)	2023		2022		2021
Net loss	$	(3,182)	$	(16,709)	$	(7,471)

Basic weighted-average common shares outstanding	47,590		47,130		46,472
Effect of dilutive stock options and restricted stock units	—		—		—
Diluted weighted-average common shares outstanding	47,590		47,130		46,472

Basic loss per common share	$	(0.07)	$	(0.35)	$	(0.16)
Diluted loss per common share	$	(0.07)	$	(0.35)	$	(0.16)

Anti-dilutive shares excluded from diluted net loss per common share:
Stock options	6,717		6,609		5,670
Restricted stock units	931		648		399

Net Loss Per Common Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Schedule of net loss attributable to common shareholders and share data used in the basic and diluted earnings per share computations using the two class method

A summary of net loss per common share is presented below:


	Year Ended December 31,
(Amounts in thousands, except per share amounts)	2023		2022		2021
Net loss	$	(3,182)	$	(16,709)	$	(7,471)

Basic weighted-average common shares outstanding	47,590		47,130		46,472
Effect of dilutive stock options and restricted stock units	—		—		—
Diluted weighted-average common shares outstanding	47,590		47,130		46,472

Basic loss per common share	$	(0.07)	$	(0.35)	$	(0.16)
Diluted loss per common share	$	(0.07)	$	(0.35)	$	(0.16)

Anti-dilutive shares excluded from diluted net loss per common share:
Stock options	6,717		6,609		5,670
Restricted stock units	931		648		399

Revenue (Tables)

12 Months Ended

Dec. 31, 2023

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

The following table and descriptions below show the products from which the Company generated its revenue for the periods indicated:


	Year Ended December 31,
Revenue by product (in thousands)	2023		2022		2021
MACI implants and kits
Implants based on contracted rate sold through a specialty pharmacy (a)	$	105,948	$	81,388	$	71,969
Implants subject to third party reimbursement sold through a specialty pharmacy (b)	22,203		18,695		16,000
Implants sold direct based on contracted rates (c)	27,484		24,261		18,714
Implants sold direct subject to third-party reimbursement (d)	4,921		3,499		2,821
Biopsy kits - direct bill	2,087		2,090		2,194
Change in estimates related to prior periods (e)	2,157		2,034		(144)
Total MACI implants and kits	164,800		131,967		111,554
Epicel
Direct bill (hospital)	31,574		31,731		41,521

NexoBrid revenue (f)	1,142		667		3,109
Total revenue	$	197,516	$	164,365	$	156,184

(a) Represents implants sold through Orsini and AllCare whereby such specialty pharmacies have a direct contract with the underlying insurance provider. The amount of reimbursement is based on contracted rates at the time of sale supported by the pharmacy’s direct contracts.

(b) Represents implants sold through Orsini and AllCare whereby such specialty pharmacy does not have a direct contract with the underlying payer and are subject to third-party reimbursement. The amount of reimbursement is established based on publicly available rates, fee schedules or past payer precedents.

(c) Represents implants sold directly from the Company to the facility based on a contract and known price agreed upon prior to the surgery date. Also represents direct sales under a contract to specialty distributor DMS.

(d) Represents implants sold directly from the Company to the facility based on a contract and known price agreed upon prior to the surgery date. The payment terms are subject to third-party reimbursement from an underlying insurance provider.

(e) Primarily represents changes in estimates related to implants sold through Orsini or AllCare and relate to changes to the initial expected reimbursement or collection expectations upon completion of the billing claims process. The change in estimates is a result of additional information, changes in collection expectations or actual cash collections received in the current period.

(f) Represents commercial revenue for the year ended December 31, 2023. In the years ended December 31, 2022 and 2021, represents revenue based on a percentage of gross profits for sales of NexoBrid to BARDA, pursuant to the license agreement between the Company and MediWound (see note 14).

Schedules of Concentration of Credit Risk

The Company’s total revenue and accounts receivable concentrations from a single customer consisted of the following:


For the year ended and as of	Revenue		Accounts Receivable
December 31, 2022	12	%	10	%
December 31, 2023	11	%	13	%

Stock-Based Compensation - Schedule of non-cash stock-based compensation expense (Details) - Employee stock purchase plan and service-based stock options - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total non-cash stock-based compensation expense	$ 32,325	$ 37,183	$ 34,322
Cost of product sales
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total non-cash stock-based compensation expense	2,970	3,630	3,681
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total non-cash stock-based compensation expense	3,705	5,261	4,120
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total non-cash stock-based compensation expense	$ 25,650	$ 28,292	$ 26,521

Selected Balance Sheet Components - Intangible assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
2024	$ 625
2025	625
2026	625
2027	625
2028	625
Thereafter	3,750
Total	$ 6,875	$ 7,500

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Product sales, net	$ 197,516	$ 163,698	$ 153,075
Other revenue	0	667	3,109
Total revenue	197,516	164,365	156,184
Accounting Standards Update 2014-09 \| Change in estimates related to prior periods
Disaggregation of Revenue [Line Items]
Product sales, net	2,157	2,034	(144)
Total MACI implants and kits
Disaggregation of Revenue [Line Items]
Product sales, net	164,800	131,967	111,554
Through Intermediary \| MACI implants and kits \| Contract rate
Disaggregation of Revenue [Line Items]
Product sales, net	105,948	81,388	71,969
Through Intermediary \| MACI implants and kits \| Time-and-materials contract
Disaggregation of Revenue [Line Items]
Product sales, net	22,203	18,695	16,000
Time-and-materials contract \| MACI implants and kits \| Time-and-materials contract
Disaggregation of Revenue [Line Items]
Product sales, net	4,921	3,499	2,821
Provider or Facility \| MACI implants and kits \| Contract rate
Disaggregation of Revenue [Line Items]
Product sales, net	27,484	24,261	18,714
Provider or Facility \| NexoBrid
Disaggregation of Revenue [Line Items]
Other revenue	1,142	667	3,109
Directly to consumer \| Biopsy kits - direct bill
Disaggregation of Revenue [Line Items]
Product sales, net	2,087	2,090	2,194
Directly to consumer \| Epicel
Disaggregation of Revenue [Line Items]
Product sales, net	$ 31,574	$ 31,731	$ 41,521

Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended			108 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2023
Stock-Based Compensation
Awards available for future grant under the Plan (in shares)	2,572,326			2,572,326
Expected to vest (in shares)	6,525,103			6,525,103
Total unrecognized compensation cost	$ 20.4			$ 20.4
Intrinsic value of stock options exercised	$ 7.5	$ 5.4	$ 39.5
Stock options
Stock-Based Compensation
Expiration period	10 years
Vesting period	4 years
Weighted average period over which unrecognized compensation is expected to be recognized	2 years 2 months 12 days
Restricted stock units
Stock-Based Compensation
Granted (in USD per share)	$ 30.36	$ 33.71	$ 52.07
Unrecognized compensation cost	$ 17.2			$ 17.2
Weighted average period over which unrecognized compensation is expected to be recognized	2 years 7 months 6 days
Fair value of vested awards	$ 6.8	$ 4.6
Restricted stock units \| Awarded annually \| Nonemployee directors
Stock-Based Compensation
Vesting period	1 year
Restricted stock units \| Awarded upon initial appointment to the BOD \| Nonemployee directors
Stock-Based Compensation
Vesting period	3 years
Employee Stock Purchase Plan
Stock-Based Compensation
Common stock available for issuance (in shares)	1,000,000			1,000,000
Shares of common stock issued (in shares)				848,470

Selected Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Schedule of inventory

Inventory consisted of the following:


	December 31,
(In thousands)	2023		2022
Raw materials	$	11,348	$	15,101
Work-in-process	1,210		832
Finished goods	529		53
Total inventory	$	13,087	$	15,986

Schedule of property and equipment, net

Property and Equipment, net consisted of the following:


	December 31,
(In thousands)	2023		2022
Machinery and equipment	$	5,562	$	5,041
Furniture, fixtures and office equipment	1,731		1,710
Computer equipment and software	9,116		8,224
Leasehold improvements	14,901		13,689
Construction in process	32,531		5,438
Financing right-of-use lease	—		37
Total property and equipment, gross	63,841		34,139
Less accumulated depreciation	(22,206)		(18,302)
Total property and equipment, net	$	41,635	$	15,837

Schedule of finite-lived intangible assets


			December 31, 2023						December 31, 2022
(In thousands)	Useful Life (in years)	Amortization Method	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
NexoBrid license	12	Straight-line	$	7,500	$	(625)	$	6,875	$	7,500	$	—	$	7,500

Schedule of finite-lived intangible assets, future amortization expense

Future amortization expense of intangible assets as of December 31, 2023 is estimated to be as follows:


(In thousands)	Amount
2024	$	625
2025	625
2026	625
2027	625
2028	625
Thereafter	3,750
Total	$	6,875

Schedule of accrued expenses

Accrued Expenses consisted of the following:


	December 31,
(In thousands)	2023		2022
Bonus related compensation	$	9,757	$	7,132
Employee related accruals	3,503		3,101
Insurance reimbursement-related liabilities	3,591		5,030
Other accrued expenses	364		927
Total accrued expenses	$	17,215	$	16,190

Investments - Schedule of Fair Value of Securities, Not Including Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Marketable Securities [Line Items]
Amortized Cost	$ 65,852	$ 89,411
Gains	1	0
Losses	(101)	(978)
Credit Losses	0	0
Estimated Fair Value	65,752	88,433
Short-term investments
Marketable Securities [Line Items]
Estimated Fair Value	40,469	68,471
Long-term investments
Marketable Securities [Line Items]
Estimated Fair Value	25,283	19,962
Commercial paper
Marketable Securities [Line Items]
Amortized Cost	3,638	15,707
Gains	1	0
Losses	0	(101)
Credit Losses	0	0
Estimated Fair Value	3,639	15,606
Corporate notes
Marketable Securities [Line Items]
Amortized Cost	47,228	52,159
Gains	0	0
Losses	(69)	(831)
Credit Losses	0	0
Estimated Fair Value	47,159	51,328
U.S. government securities
Marketable Securities [Line Items]
Amortized Cost	983
Gains	0
Losses	0
Credit Losses	0
Estimated Fair Value	983
U.S. government agency bonds
Marketable Securities [Line Items]
Amortized Cost	14,003	21,545
Gains	0	0
Losses	(32)	(46)
Credit Losses	0	0
Estimated Fair Value	$ 13,971	$ 21,499

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of non-cash stock-based compensation expense

Non-cash stock-based compensation expense (service-based stock options, restricted stock units and employee stock purchase plan) is summarized in the following table:


	Years Ended December 31,
(in thousands)	2023		2022		2021
Cost of product sales	$	2,970	$	3,630	$	3,681
Research and development	3,705		5,261		4,120
Selling, general and administrative	25,650		28,292		26,521
Total non-cash stock-based compensation expense	$	32,325	$	37,183	$	34,322

Schedule of fair value assumptions

The fair value of each service-based stock option grant for the reported periods is estimated on the date of the grant using the Black-Scholes option-pricing model using the assumptions noted in the following table:


	Year Ended December 31,
Service-Based Stock Options	2023	2022	2021
Expected dividend rate	—%	—%	—%
Expected stock price volatility	62.5 - 66.7%	63.8 - 75.3%	71.5 - 76.7%
Risk-free interest rate	3.4 - 4.7%	1.5 - 4.4%	0.53 -1.5%
Expected life (years)	5.5	5.3 - 6.3	5.3 - 6.3
Weighted-average grant date fair value	$18.85	$19.83	$32.96

Summary of activity for service-based stock options

The following table summarizes the activity for service-based stock options for the indicated periods:


Service-Based Stock Options	Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (Thousands)
Outstanding at December 31, 2022	6,609,147	$	24.89	6.8	$	56,708
Granted	607,947	30.90
Exercised	(377,597)	12.55
Expired	(41,004)	45.21
Forfeited	(81,807)	37.96
Outstanding at December 31, 2023	6,716,686	$	25.85	6.16	$	88,387
Exercisable at December 31, 2023	4,967,797	$	22.16	5.45	$	82,288

Summary of activity for restricted stock awards

The following table summarizes the activity for restricted stock units for the indicated periods:


Restricted Stock Units	Number of Restricted Stock Units	Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2022	648,174	$	34.86
Granted	564,449	30.36
Vested	(224,142)	32.34
Forfeited	(57,545)	33.01
Unvested at December 31, 2023	930,936	$	32.85

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating Loss Carryforwards [Line Items]
Projected annual limitation on the use of the net operating losses that existed prior to September 17, 2014	$ 800
General business tax credit carryforward	10,781	$ 11,143
Increase (decrease) in valuation allowance	2,500	$ 3,300
Federal \| Internal Revenue Service
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	11,700
Net operating loss carryforwards which begin to expire in 2033	8,300
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 16,600

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Schedule of future minimum purchase commitments related to contractual obligations

Future minimum purchase commitments related to the Company’s contractual obligations are as follows:


			Payments Due by Period
Contractual Obligations (In thousands)	Total		2024		2025		2026		2027		2028		More than 5 Years
Purchase commitments	$	19,329	$	8,271	$	1,512	$	1,611	$	1,909	$	2,009	$	4,017
Warehouse operating agreement	3,795		1,850		746		788		411		—		—
Total	$	23,124	$	10,121	$	2,258	$	2,399	$	2,320	$	2,009	$	4,017

Leases (Tables)

12 Months Ended

Dec. 31, 2023

Leases [Abstract]

Assets and liabilities

Operating and finance lease assets and liabilities are as follows:


		December 31,
(In thousands)	Classification	2023		2022
Assets
Operating	Right-of-use assets	$	73,462	$	41,535
Finance	Property and equipment, net	—		37
Total leased assets		$	73,462	$	41,572
Liabilities
Current
Operating	Current portion of operating lease liabilities	$	6,187	$	4,302
Finance	Other current liabilities	—		41

Non-current
Operating	Operating lease liabilities	81,856		43,268

Total leased liabilities		$	88,043	$	47,611

Maturity of lease liabilities

Future minimum lease payments under non-cancellable leases as of December 31, 2023 are as follows:


(In thousands)	Total
2024	$	11,890
2025	13,677
2026	13,969
2027	14,351
2028	14,743
Thereafter	88,486
Total lease payments	$	157,116
Less: tenant improvement allowances	(20,721)
Less: interest	(48,352)
Present value of lease liabilities	$	88,043

Maturity of lease liabilities

Future minimum lease payments under non-cancellable leases as of December 31, 2023 are as follows:


(In thousands)	Total
2024	$	11,890
2025	13,677
2026	13,969
2027	14,351
2028	14,743
Thereafter	88,486
Total lease payments	$	157,116
Less: tenant improvement allowances	(20,721)
Less: interest	(48,352)
Present value of lease liabilities	$	88,043

Lease term and discount rate

Lease terms and discount rates are as follows:


	December 31,
	2023	2022
Weighted-average remaining lease term (years)
Operating leases	10.0	8.9
Finance leases	—	0.5
Weighted-average discount rate
Operating leases	6.8%	5.4%
Finance leases	—%	5.0%

Nexobrid License and Supply Agreements	12 Months Ended
Nexobrid License and Supply Agreements	Dec. 31, 2023
Related Party Transactions [Abstract]
NexoBrid License and Supply Agreements	NexoBrid License and Supply Agreements On May 6, 2019, the Company entered into exclusive license and supply agreements with MediWound to commercialize NexoBrid in North America. The FDA subsequently approved a BLA for the product on December 28, 2022. NexoBrid is a topically-administered biological orphan product, which contains proteolytic enzymes and is indicated for the removal of eschar in adults with deep partial-thickness and/or full thickness thermal burns. Pursuant to the terms of the license agreement, following the FDA approval of NexoBrid, MediWound transferred the BLA to Vericel effective February 20, 2023. Both MediWound and Vericel, under the supervision of a Central Steering Committee comprised of members of both companies will continue to guide the development of NexoBrid in North America (the “Central Steering Committee”). NexoBrid is approved in the European Union (“EU”) and other international markets and has been designated as an orphan biologic in the U.S., EU and other international markets. In May 2019, the Company paid MediWound $17.5 million in consideration for the license, which was recorded as research and development expense during 2019. In December 2022, the FDA approved the BLA for NexoBrid, which resulted in the achievement of a $7.5 million regulatory milestone payment pursuant to the terms of the license agreement. The Company recorded the $7.5 million milestone for the licensing rights to commercially sell NexoBrid in the U.S. as an intangible asset as of December 31, 2022 (see Note 4, “Selected Balance Sheet Components” for further details). The $7.5 million milestone payment was paid to MediWound in February of 2023. The Company commenced commercial sales of NexoBrid in the U.S. in September 2023. The Company is obligated to pay MediWound up to $125.0 million, which is contingent upon meeting certain sales milestones. The first sales milestone payment of $7.5 million would be triggered when annual net sales of NexoBrid or improvements to it in North America exceed $75.0 million. As of December 31, 2023, the sales milestone payments are not yet probable and therefore, not recorded as a liability. The Company also will pay MediWound tiered royalties on net sales ranging from mid-high single-digit to mid-teen percentages, subject to customary reductions. Pursuant to the terms of the Company’s supply agreement with MediWound, MediWound is manufacturing and will continue to manufacture NexoBrid for the Company on a unit price basis, which may be increased pursuant to the terms of the supply agreement. MediWound is obligated to supply the Company with NexoBrid for sale in North America on an exclusive basis for the first five years of the term of the supply agreement. Under the supply agreement, the Company possesses the option to extend the initial term of the agreement by an additional 24 months, which it did in May 2022. After the initial term, the Company may extend the supply agreement on an annual basis for up to 10 additional years, at its sole discretion. Under the supply agreement, the Company is permitted to establish an alternate source of supply in certain circumstances, including the event of a supply failure. Additionally, beginning in 2020 BARDA procured quantities of NexoBrid from MediWound for use as a medical countermeasure in the event of a mass casualty emergency in the U.S. involving thermal burns. The initial, quarterly, procurement of NexoBrid by BARDA under its agreement with MediWound completed during the third quarter of 2022. As a part of BARDA’s commitment to procure NexoBrid, the Company has received a percentage of gross profit for sales directly to BARDA. As of December 31, 2023, the Company did not hold a direct contract or distribution agreement with BARDA, or take title to the product procured by BARDA. On May 9, 2023, MediWound announced BARDA’s award of additional funding under the parties’ existing agreement, $3.0 million of which will support the replacement of NexoBrid, previously procured for emergency response preparedness, which has since expired. Pursuant to the terms of the Company’s license agreement with MediWound, the Company will recognize revenue based on a percentage of gross profits, minus a percentage of net sales, on any sales of NexoBrid directly to BARDA, upon delivery, pursuant to this additional award.

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2023
Accounting Policies [Abstract]
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents and investments in marketable debt securities. The Company may maintain deposits in financial institutions in excess of the insurance coverage offered by the Federal Deposit Insurance Corporation, the loss of which could have a negative effect on its operations and liquidity. The Company believes that it is not exposed to significant credit risk as its deposits, including cash and cash equivalents, are held at multiple high credit quality financial institutions. The Company has not experienced any losses on these deposits; however no assurances can be provided that there will not be losses experienced in the future. The Company believes that the market risk arising from its holdings of these financial instruments is mitigated based on the fact that many of these securities are either government-backed or of high credit rating.
Principles of Consolidation	The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and accounts have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenues and expenses during the reporting period. The more significant estimates reflected in the Company’s consolidated financial statements include, but are not limited to, certain judgments regarding revenue recognition, inventory valuation, stock option valuation, lease valuation, deferred tax assets and liabilities and accrued expenses. The Company is not aware of any specific event or circumstance that would require an update to its estimates or judgments reflected in these consolidated financial statements or a revision of the carrying value of its assets or liabilities as of the issuance of these consolidated financial statements. These estimates may change as new events occur and additional information is obtained. Actual results could materially differ from those estimates.
Cash Equivalents	Cash Equivalents Cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less from the date of purchase and consist primarily of demand deposits, money market funds, U.S. government securities, U.S. government agency bonds and commercial paper.
Restricted Cash	Restricted Cash Restricted cash as of December 31, 2023, represents amounts in a construction escrow account. See Note 5, “Leases” for further discussion.
Investments	Investments Investments classified as short-term have maturities of less than one year. Investments classified as long-term are those that: (i) have a maturity of greater than one year, and (ii) the Company does not intend to liquidate within the next twelve months, although these funds are available for use and, therefore, are classified as available-for-sale. The Company’s investment strategy is to buy short-duration marketable securities with a high credit rating. As of December 31, 2023 and 2022, all marketable securities held by the Company had remaining contractual maturities of three years or less. Unrealized gains are included as a component of accumulated other comprehensive income in the consolidated balance sheets and consolidated statements of shareholders’ equity and a component of total comprehensive (loss) income in the consolidated statements of comprehensive (loss) income, until realized. Unrealized losses are evaluated for impairment under ASC 326, Financial Instruments - Credit Losses (“ASC 326”), to determine if the impairment is credit-related or non-credit-related. Credit-related impairment is recognized as an allowance on the balance sheet with a corresponding adjustment to earnings, and non-credit-related impairment is recognized in other comprehensive (loss) income, net of taxes.
Leases	Leases The Company determines if an arrangement is a lease at inception, in accordance with ASC Topic 842, Leases. All operating lease commitments with a lease term greater than 12 months are recognized as right-of-use assets and liabilities, on a discounted basis on the balance sheet. Leases with an initial term of 12 months or less are not recorded on the balance sheet. Certain of the Company’s lease agreements include lease payments that are adjusted periodically for an index or rate. The leases are initially measured using the present value of the projected payments adjusted for the index or rate in effect at the commencement date. In addition to rent, the leases may require the Company to pay additional amounts for taxes, insurance, maintenance and other expenses, which do not transfer a good or service to the Company and are generally referred to as non-lease components. Variable non-lease components are not measured as part of the right-of-use asset and liability. Only when lease components and their associated non-lease components are fixed are they accounted for as a single lease component and are recognized as part of a right-of-use asset and liability. The Company’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. The Company has options to renew lease terms for facilities and other assets. Some leases contain clauses for renewal at the Company’s option with renewal terms that generally extend the lease term from 1 to 10 years. The exercise of lease renewal options is generally at the Company’s sole discretion. The Company evaluates renewal and termination options at the lease commencement date to determine if it is reasonably certain to exercise the option on the basis of economic factors. Certain lease agreements contain options to terminate the lease. A portfolio approach is applied to certain lease contracts with similar characteristics. The Company uses a discount rate to calculate the present value of lease payments in order to determine lease classification and measurement of the lease asset and liability. In the absence of a rate of interest that is readily determinable in the contract, the Company estimates the incremental borrowing rate (“IBR”) for each lease based on the information available at commencement. The IBR reflects the rate of interest that the Company would pay on the lease commencement date to borrow an amount equal to the lease payments on a collateralized basis over a similar term in similar economic environments.
Inventory	Inventory Inventories are measured at the lower of cost or net realizable value. Cost is calculated based upon standard-cost which approximates costs determined on the first-in, first-out method. The Company periodically reviews its inventories for excess or obsolescence and writes down obsolete or other unmarketable inventory to its estimated net realizable value. If the actual net realizable value is less than that estimated by the Company, or if it is determined that inventory utilization will further diminish based on estimates of demand, additional inventory write-downs may be required. In all cases, product inventory is carried at the lower of cost or its estimated net realizable value. Amounts written down are charged to cost of product sales.
Accounts Receivable	Accounts Receivable Accounts receivable are initially recorded at the contractual amount owed by the customer or based on expected payments from the insurance provider, hospital or patient. Allowances for doubtful accounts are established when the facts and circumstances indicate that a receivable may not be collectible. Potential credit risk exposure has been evaluated for the Company’s accounts receivable in accordance with ASC 326. The Company assesses risk and determines a loss percentage by pooling accounts receivable based on similar risk characteristics. The loss percentage is calculated through the use of forecasts that are based on current and historical economic and financial information.
Property and Equipment, net	Property and Equipment, net Property and equipment are initially measured and recognized at acquisition cost, including any directly attributable cost of preparing the asset for its intended use. After initial measurement, property and equipment are carried at cost less accumulated depreciation. Repair and maintenance costs of property and equipment are expensed as incurred. The depreciable value of property and equipment is depreciated on a straight-line basis over the useful life of the asset. The useful life of an asset is usually equivalent to its economic life. The useful lives of property and equipment are as follows: •Machinery and equipment: 3 to 10 years •Furniture, fixtures and office equipment: 5 years •Computer equipment and software: 3 years •Leasehold improvements: shorter of the remaining life of the lease or 15 years The costs of assets retired or otherwise disposed of and the accumulated depreciation thereon are removed from the accounts, with any gain or loss realized upon sale or disposal credited or charged to operations.
Intangible Assets, net	Intangible Assets, net The Company amortizes its intangible assets on a straight-line basis over their estimated economic lives, unless another amortization method is deemed to be more appropriate. In determining the useful lives of intangible assets, the Company considers the expected use of the assets and the effects of obsolescence, demand, competition, anticipated technological advances, market influence and other economic factors.
Long-Lived Assets	Long-Lived Assets The Company evaluates long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be fully recoverable.
Revenue Recognition	Revenue Recognition The Company recognizes product revenue from sales to a customer following the five step model in Accounting Standards Codification 606, Revenue Recognition (“ASC 606”): (i) identify contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenues when (or as) the Company satisfies the performance obligation. Under this revenue standard, the Company recognizes revenue when its customer obtains control of the promised goods, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods. There are no contractual rights of returns, refunds or similar obligations related to MACI, MACI biopsy kits or Epicel; however, in certain limited cases the Company will accept a product return if a surgery is canceled. Revenue is not recognized in certain canceled cases. There are limited contractual rights of returns, refunds, or similar obligations related to NexoBrid. For MACI, MACI biopsy kits, Epicel and NexoBrid, there are no variable pricing arrangements related to warranties or rebates offered to customers. The majority of orders are due within 30 to 90 days of delivery. Shipping and handling fees are included as a component of revenue. The Company recognizes any commission fees as an expense when incurred. These fees are included in selling, general, and administrative expenses.
Research and Development Expense	Research and Development Expense Research and development expenses are expensed as incurred. These expenditures relate to the development of new products, improvement of existing products, technical support of products and compliance with governmental regulations for the protection of consumers and patients.
Stock-Based Compensation	Stock-Based Compensation The Company’s accounting for stock-based compensation requires it to determine the fair value of common stock issued in the form of stock option awards and restricted stock units. The fair value of restricted stock units held by employees and non-employee directors is determined based on the fair value of the Company’s common stock on the date of the grant. Compensation expense is recorded for restricted stock units that are expected to vest over the expected vesting period. The fair value of stock options held by employees and non-employee directors is determined using a Black-Scholes option valuation method. Key assumptions in determining fair value include volatility, risk-free interest rate, dividend yield and expected term. The assumptions used in calculating the fair value of stock options represent the Company’s best estimates; however, these estimates involve inherent uncertainties and the application of management’s judgment. As a result, if factors change and different assumptions are used, the stock-based compensation expense could be materially different in the future. In addition, the Company estimates the expected forfeiture rate and only recognizes expense for those stock options expected to vest over the service period. The estimated forfeiture rate considers the historical experience of the Company’s stock-based awards. If the actual forfeiture rate is different from the estimate, expense is adjusted accordingly. The Company records the expense for stock options and restricted stock units using a graded-vesting attribution method. The Company also has an Employee Stock Purchase Plan (“ESPP”) which is a compensatory plan. Compensation expense is recorded based on the fair value of the purchased options at the grant date, which corresponds to the first day of each purchase period, and is amortized over the purchase period.
Comprehensive (Loss) Income	Comprehensive (Loss) Income Comprehensive (loss) income is the change in shareholders’ equity during a period arising from unrealized gains or losses related to the Company’s investments.
Income Taxes	Income Taxes Deferred tax assets are recognized for deductible temporary differences and tax credit carryforwards and deferred tax liabilities are recognized for taxable temporary differences. Deferred tax assets are reduced by a valuation allowance when, in the opinion of management, it is more likely than not that some portion or all of the deferred tax assets will not be realized based on the weight of available evidence. When evaluating the realizability of the deferred tax assets, all evidence, both positive and negative, is considered. Items considered when evaluating the need for a valuation allowance include the ability to carry back losses, future reversals of existing temporary differences, tax planning strategies, and expectations of future earnings. The Company records uncertain tax positions in the consolidated financial statements only if it is more likely than not that the uncertain tax position will be sustained upon examination by the taxing authorities. The Company records interest and penalties related to uncertain tax positions in income tax expense.
Net (Loss) Income Per Common Share	Net (Loss) Income Per Common Share Basic earnings per common share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period. Diluted earnings per common share is computed by dividing net income by the weighted-average number of shares of common stock outstanding during the period, plus the potential dilutive effect of other securities if those securities were converted or exercised. During periods in which the Company incurs net losses, both basic and diluted loss per common share is calculated by dividing the net loss by the weighted-average shares of common stock outstanding and potentially dilutive securities are excluded from the calculation because their effect would be antidilutive.
Financial Instruments	Financial Instruments The Company’s financial instruments include accounts receivables, accounts payable and accrued expenses for which the current carrying amounts approximate market value, based upon their short-term nature and marketable debt securities which are classified as available-for-sale and carried at fair value on a settlement date basis.
Recent Accounting Pronouncements	Recent Accounting Pronouncements No new accounting standards were adopted during the year ended December 31, 2023. The Company considers the applicability and impact of any recent Accounting Standards Updates (“ASUs”) issued by the Financial Accounting Standards Board (“FASB”), as noted below. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, to improve reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. The disclosure requirements must be applied retrospectively to all prior periods presented in the financial statements. The effective date for the standard is for fiscal years beginning after December 15, 2023 and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the effects adoption of this guidance will have on the consolidated financial statements. In December 2023, the FASB issued ASU 2023-09, Improvements to Income Tax Disclosures, to provide more detailed income tax disclosure requirements. The guidance requires entities to disclose disaggregated information about their effective tax rate reconciliation as well as information on income taxes paid. The disclosure requirements will be applied on a prospective basis, with the option to apply it retrospectively. The effective date for the standard is for fiscal years beginning after December 15, 2024, with early adoption permitted. The Company is currently evaluating the effects adoption of this guidance will have on the consolidated financial statements.

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (3,182)	$ (16,709)	$ (7,471)
Other comprehensive income (loss):
Unrealized gain (loss) on investments	878	(824)	(168)
Comprehensive loss	$ (2,304)	$ (17,533)	$ (7,639)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481687/323-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482907/825-10-50-28

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482765/220-10-50-6

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-3

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480175/815-40-65-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-8

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483443/250-10-50-9

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
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-Paragraph 11
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+ Details

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 69,088	$ 51,067
Restricted cash	17,778	0
Short-term investments	40,469	68,471
Accounts receivable (net of allowance for doubtful accounts of $43 and $47, respectively)	58,356	46,539
Inventory	13,087	15,986
Other current assets	6,853	4,803
Total current assets	205,631	186,866
Property and equipment, net	41,635	15,837
Intangible assets, net	6,875	7,500
Right-of-use assets	73,462	41,535
Long-term investments	25,283	19,962
Other long-term assets	771	1,303
Total assets	353,657	273,003
Current liabilities:
Accounts payable	22,347	16,930
Accrued expenses	17,215	16,190
Current portion of operating lease liabilities	6,187	4,302
Other current liabilities	0	41
Total current liabilities	45,749	37,463
Operating lease liabilities	81,856	43,268
Other long-term liabilities	100	0
Total liabilities	127,705	80,731
COMMITMENTS AND CONTINGENCIES (Note 15)
Shareholders’ equity:
Common stock, no par value; shares authorized — 75,000; shares issued and outstanding — 47,829 and 47,253, respectively	629,229	593,245
Accumulated other comprehensive loss	(100)	(978)
Accumulated deficit	(403,177)	(399,995)
Total shareholders’ equity	225,952	192,272
Total liabilities and shareholders’ equity	$ 353,657	$ 273,003

Fair Value Measurements

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurements

The Company’s fair value measurements are classified and disclosed in one of the following three categories:

•Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;

•Level 2: Quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability;

•Level 3: Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity).

Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The commercial paper, corporate notes, U.S. government securities, and U.S. government agency bonds are classified as Level 2 as they were valued based upon quoted market prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. There were no transfers into or out of Level 3 from December 31, 2021 to December 31, 2023.

The following table summarizes the valuation of the Company’s financial instruments that are measured at fair value on a recurring basis:


	December 31, 2023								December 31, 2022
			Fair value measurement category								Fair value measurement category
(In thousands)	Total		Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	34,672	$	34,672	$	—	$	—	$	1,262	$	1,262	$	—	$	—
Commercial paper (a)	4,876		—		4,876		—		15,606		—		15,606		—
Corporate notes	47,159		—		47,159		—		51,328		—		51,328		—
U.S. government agency bonds (a)	13,971		—		13,971		—		27,976		—		27,976		—
U.S. government securities (a)	24,874		—		24,874		—		$	—	$	—	$	—	$	—
	$	125,552	$	34,672	$	90,880	$	—	$	96,172	$	1,262	$	94,910	$	—

(a) Approximately $23.9 million of U.S. government securities and $1.2 million of commercial paper had an original maturity of 90 days or less and is recorded as a cash equivalent as of December 31, 2023. Approximately $6.5 million of U.S. government agency bonds and $8.0 million of commercial paper had an original maturity of 90 days or less and is recorded as a cash equivalent as of December 31, 2022.

The fair values of the cash equivalents and marketable securities are based on observable market prices. The Company’s accounts receivables, accounts payable and accrued expenses are valued at cost which approximates fair value.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Stock-Based Compensation

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

Stock Option, Restricted Stock Units and Equity Incentive Plans

The Company has historically had various stock incentive plans and agreements that provide for the issuance of non-qualified and incentive stock options and restricted stock units as well as other equity awards. Such awards may be granted by the Company’s Board of Directors to certain of the Company’s employees, directors and consultants.

Options granted to employees and non-employees under these plans expire no later than ten years from the date of grant. Options and restricted stock units generally become exercisable or vest over a four year period (other than options and restricted stock units awarded annually to non-employee directors, which generally vest over one year, and options and restricted stock units awarded to non-employee directors upon initial appointment to the Vericel Board of Directors, which generally vest over a three year period), under a graded-vesting methodology for stock options and annually on the anniversary grant date for restricted stock units, following the date of grant. The Company generally issues new shares upon the exercise of stock options or vesting of restricted stock units.

The Vericel Corporation 2022 Omnibus Incentive Plan (“2022 Plan”) was approved on April 27, 2022, and provides incentives through the grant of stock options, stock appreciation rights, restricted stock awards and restricted stock units. The exercise price of stock options granted under the 2022 Plan shall not be less than the fair market value of the Company’s common stock on the date of grant. The 2022 Plan replaced the 1992 Stock Option Plan, the 2001 Stock Option Plan, the Amended and Restated 2004 Equity Incentive Plan, the 2009 Second Amended and Restated Omnibus Incentive Plan, the 2017 Omnibus Incentive Plan, and the Amended and Restated 2019 Omnibus Incentive Plan (collectively the “Prior Plans”), and no new grants have been granted under the Prior Plans after approval of the 2022 Plan. However, the expiration or forfeiture of options previously granted under the Prior Plans will increase the number of shares available for issuance under the 2022 Plan.

As of December 31, 2023, there were 2,572,326 shares available for future grant under the 2022 Plan.

Stock Compensation Expense

Non-cash stock-based compensation expense (service-based stock options, restricted stock units and employee stock purchase plan) is summarized in the following table:


	Years Ended December 31,
(in thousands)	2023		2022		2021
Cost of product sales	$	2,970	$	3,630	$	3,681
Research and development	3,705		5,261		4,120
Selling, general and administrative	25,650		28,292		26,521
Total non-cash stock-based compensation expense	$	32,325	$	37,183	$	34,322

Service-Based Stock Options


	Year Ended December 31,
Service-Based Stock Options	2023	2022	2021
Expected dividend rate	—%	—%	—%
Expected stock price volatility	62.5 - 66.7%	63.8 - 75.3%	71.5 - 76.7%
Risk-free interest rate	3.4 - 4.7%	1.5 - 4.4%	0.53 -1.5%
Expected life (years)	5.5	5.3 - 6.3	5.3 - 6.3
Weighted-average grant date fair value	$18.85	$19.83	$32.96

The following table summarizes the activity for service-based stock options for the indicated periods:


Service-Based Stock Options	Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value (Thousands)
Outstanding at December 31, 2022	6,609,147	$	24.89	6.8	$	56,708
Granted	607,947	30.90
Exercised	(377,597)	12.55
Expired	(41,004)	45.21
Forfeited	(81,807)	37.96
Outstanding at December 31, 2023	6,716,686	$	25.85	6.16	$	88,387
Exercisable at December 31, 2023	4,967,797	$	22.16	5.45	$	82,288

As of December 31, 2023, 6,525,103 shares are vested and expected to vest. As of December 31, 2023, there was approximately $20.4 million of total unrecognized compensation cost related to non-vested service-based stock options granted under the 2022 Plan and the Prior Plans. That cost is expected to be recognized over a weighted-average period of 2.2 years.

The total intrinsic value of stock options exercised for the years ended December 31, 2023, 2022, and 2021 was $7.5 million, $5.4 million and $39.5 million, respectively.

Restricted Stock Units

The following table summarizes the activity for restricted stock units for the indicated periods:


Restricted Stock Units	Number of Restricted Stock Units	Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2022	648,174	$	34.86
Granted	564,449	30.36
Vested	(224,142)	32.34
Forfeited	(57,545)	33.01
Unvested at December 31, 2023	930,936	$	32.85

The weighted-average grant-date fair value of restricted stock units granted during the years ended December 31, 2023, 2022, and 2021 was $30.36, $33.71 and $52.07, respectively.

At December 31, 2023 the total unrecognized compensation cost related to the restricted stock units was $17.2 million, and the weighted-average period over which that cost is expected to be recognized was 2.6 years. The total fair value of restricted stock units vested in the years ended December 31, 2023 and 2022 was $6.8 million and $4.6 million respectively.

Employee Stock Purchase Plan

Employees are able to purchase stock under the ESPP. The ESPP allows for the issuance of an aggregate of 1.0 million shares of common stock of which 848,470 have been issued since the inception of the benefit in 2015. Participation in this plan is available to substantially all employees. The ESPP is a compensatory plan accounted for under the expense recognition provisions of the share-based payment accounting standards. Compensation expense is recorded based on the fair market value of the purchase options at the grant date, which corresponds to the first day of each purchase period and is amortized over the purchase period.

Audit Information	12 Months Ended
Audit Information	Dec. 31, 2023
Audit Information [Abstract]
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Boston, Massachusetts

Investments - Narrative (Details) - USD ($)	12 Months Ended
Investments - Narrative (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Asset impairment charges	$ 0	$ 0

Revolving Credit Agreement (Details) - Line of Credit	Jul. 29, 2022 USD ($)	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
Issuance of letters of credit	$ 6,200,000
Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 150,000,000
Debt instrument, term	5 years
Debt issuance costs, net	$ 1,100,000
Outstanding borrowings		$ 0
Leverage ratio	3.50
Increase option for leverage ratio	4.00
Revolving Credit Facility \| Minimum
Debt Instrument [Line Items]
Line of credit facility, commitment fee (in percent)	0.20%
Revolving Credit Facility \| Maximum
Debt Instrument [Line Items]
Line of credit facility, commitment fee (in percent)	0.25%
Revolving Credit Facility \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	0.10%
Revolving Credit Facility \| Secured Overnight Financing Rate (SOFR) \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	1.25%
Revolving Credit Facility \| Secured Overnight Financing Rate (SOFR) \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	2.50%
Revolving Credit Facility \| Base Rate \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	0.25%
Revolving Credit Facility \| Base Rate \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate (in percent)	1.50%
Letter of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 15,000,000

Leases - Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Assets
Operating	$ 73,462	$ 41,535
Finance	0	37
Total leased assets	73,462	41,572
Current
Operating	6,187	4,302
Finance	0	41
Non-current
Operating	81,856	43,268
Present value of lease liabilities	$ 88,043	$ 47,611
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property and equipment, net	Property and equipment, net
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other current liabilities	Other current liabilities

Selected Balance Sheet Components

12 Months Ended

Dec. 31, 2023

Balance Sheet Related Disclosures [Abstract]

Selected Balance Sheet Components

Inventory

Inventory consisted of the following:


	December 31,
(In thousands)	2023		2022
Raw materials	$	11,348	$	15,101
Work-in-process	1,210		832
Finished goods	529		53
Total inventory	$	13,087	$	15,986

Property and Equipment

Property and Equipment, net consisted of the following:


	December 31,
(In thousands)	2023		2022
Machinery and equipment	$	5,562	$	5,041
Furniture, fixtures and office equipment	1,731		1,710
Computer equipment and software	9,116		8,224
Leasehold improvements	14,901		13,689
Construction in process	32,531		5,438
Financing right-of-use lease	—		37
Total property and equipment, gross	63,841		34,139
Less accumulated depreciation	(22,206)		(18,302)
Total property and equipment, net	$	41,635	$	15,837

Depreciation expense for the years ended December 31, 2023, 2022 and 2021 was $4.0 million, $4.0 million and $3.0 million, respectively.

Intangible Assets

The Company’s intangible assets of $7.5 million is comprised of a license for NexoBrid, as a result of regulatory approval received on December 28, 2022. The intangible asset is amortized to cost of product sales.


			December 31, 2023						December 31, 2022
(In thousands)	Useful Life (in years)	Amortization Method	Cost		Accumulated Amortization		Net		Cost		Accumulated Amortization		Net
NexoBrid license	12	Straight-line	$	7,500	$	(625)	$	6,875	$	7,500	$	—	$	7,500

Amortization expense for the year ended December 31, 2023 was $0.6 million. There was no amortization expense recognized during the year ended December 31, 2022.

Future amortization expense of intangible assets as of December 31, 2023 is estimated to be as follows:


(In thousands)	Amount
2024	$	625
2025	625
2026	625
2027	625
2028	625
Thereafter	3,750
Total	$	6,875

Accrued Expenses

Accrued Expenses consisted of the following:


	December 31,
(In thousands)	2023		2022
Bonus related compensation	$	9,757	$	7,132
Employee related accruals	3,503		3,101
Insurance reimbursement-related liabilities	3,591		5,030
Other accrued expenses	364		927
Total accrued expenses	$	17,215	$	16,190

Organization	12 Months Ended
Organization	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Vericel Corporation, a Michigan corporation (together with its consolidated subsidiaries referred to herein as the Company, or Vericel), was incorporated in March 1989 and began employee-based operations in 1991. The Company is a fully-integrated, commercial-stage biopharmaceutical company and is a leading provider of advanced therapies for the sports medicine and severe burn care markets. Vericel currently markets three commercial-stage products in the U.S., MACI®, Epicel® and NexoBrid®. MACI (autologous cultured chondrocytes on porcine collagen membrane) is an autologous cellularized scaffold product indicated for the repair of symptomatic, single or multiple full-thickness cartilage defects of the knee with or without bone involvement in adults. Epicel (cultured epidermal autografts) is a permanent skin replacement for the treatment of adult and pediatric patients with deep-dermal or full-thickness burns comprising greater than or equal to 30 percent of total body surface area (“TBSA”). The Company also holds an exclusive license from MediWound Ltd. (“MediWound”) for North American rights to NexoBrid (anacaulase-bcdb), a topically administered biological orphan product containing proteolytic enzymes, which is indicated for the removal of eschar in adults with deep partial-thickness and/or full thickness thermal burns. Following the FDA’s approval of a Biologics License Application for NexoBrid on December 28, 2022, the Company began commercial sales of NexoBrid in the U.S. during the third quarter of 2023. The Company operates its business primarily in the U.S. in one reportable segment - the research, product development, manufacture and distribution of cellular therapies and specialty biologics for use in the treatment of specific conditions. The Company is subject to risks common to companies in the life sciences industry including, but not limited to, development by the Company or its competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, commercialization of existing and new products, and compliance with FDA regulations and approval requirements, as well as the ability to grow the Company’s business through appropriate commercial strategies. COVID-19 On May 11, 2023, the U.S. Department of Health and Human Services announced the expiration of the federal Public Health Emergency for COVID-19. At this juncture, the pandemic’s effects on the Company’s business and results of operations have largely moderated and it has seen a return to more normal operations. Should a resurgence of COVID-19 occur, or new virus variants emerge, it could result in additional disruptions that could impact the Company’s business and operations in the future, including U.S. hospital or surgical center staffing shortages, periodic cancellation or delay of elective MACI surgical procedures, intermittent restrictions on the ability of Company personnel to travel and access customers for selling, marketing, training, case support and product development feedback, delays in approvals by regulatory bodies, delays in product development efforts, and additional government requirements or other incremental mitigation efforts that may further impact the Company’s capacity to manufacture, sell and support the use of its products. The War in Ukraine The ongoing war between Russia and Ukraine and the related sanctions and other penalties imposed by countries across the globe against Russia are continuing to create substantial uncertainty in the global economy and have contributed to heightened inflation and supply chain disruptions. While the Company does not have operations in Russia or Ukraine and does not have exposure to distributors, or third-party service providers in Russia or Ukraine, it is unable to predict the ultimate impact that these actions will have on the global economy or on its financial condition, results of operations, and cash flows as of the date of these consolidated financial statements. The War in Israel and Gaza In May 2019, the Company entered into exclusive license and supply agreements with MediWound, under which MediWound manufactures and supplies NexoBrid to the U.S. market on a unit price basis. MediWound develops and manufactures NexoBrid, in part, at its facilities in Yavne, Israel. The Company continues to monitor the ongoing conflict in Israel and is in close communication with MediWound leadership. MediWound’s NexoBrid manufacturing operations are continuing and, as of the date of this disclosure, MediWound does not anticipate a disruption to its ongoing supply of commercial NexoBrid to the United States. To the extent the war between Israel and Hamas intensifies or expands to include additional countries or militant groups in the region and MediWound’s facilities in Israel are damaged or destroyed, travel to and from Israel is halted or inhibited, or significant key MediWound operational personnel are called to military service, MediWound’s ability to continue to supply NexoBrid to the U.S. market could be disrupted. Liquidity The accompanying consolidated financial statements have been prepared on a basis which assumes that the Company will continue as a going concern and contemplates the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. As of December 31, 2023, the Company had an accumulated deficit of $403.2 million and had a net loss of $3.2 million for the year ended December 31, 2023. The Company had cash and cash equivalents of $69.1 million and investments of $65.8 million as of December 31, 2023. The Company expects that cash from the sales of its products and existing cash, cash equivalents, investments, and available borrowing capacity will be sufficient to support the Company’s current operations through at least 12 months from the issuance of these consolidated financial statements. If revenues decline for a sustained period, the Company may need to access additional capital; however, the Company may not be able to obtain additional financing on acceptable terms or at all. The terms of any additional financing may adversely affect the holdings or the rights of the Company’s shareholders. Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents and investments in marketable debt securities. The Company may maintain deposits in financial institutions in excess of the insurance coverage offered by the Federal Deposit Insurance Corporation, the loss of which could have a negative effect on its operations and liquidity. The Company believes that it is not exposed to significant credit risk as its deposits, including cash and cash equivalents, are held at multiple high credit quality financial institutions. The Company has not experienced any losses on these deposits; however no assurances can be provided that there will not be losses experienced in the future. The Company believes that the market risk arising from its holdings of these financial instruments is mitigated based on the fact that many of these securities are either government-backed or of high credit rating.

Employee Savings Plan	12 Months Ended
Employee Savings Plan	Dec. 31, 2023
Retirement Benefits [Abstract]
Employee Savings Plan	Employee Savings Plan The Company has a 401(k) savings plan that allows participating employees to contribute a portion of their salary, subject to annual limits and minimum qualifications. The Board may, at its sole discretion, approve Company matching contributions to the plan. The Company made contributions of $1.2 million, $1.1 million and $1.0 million for the years ended December 31, 2023, 2022 and 2021, respectively.

- Definition

The entire disclosure for retirement benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 70
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480266/715-60-50-3

+ Details

Selected Balance Sheet Components - Schedule of accrued expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accrued expenses
Bonus related compensation	$ 9,757	$ 7,132
Employee related accruals	3,503	3,101
Insurance reimbursement-related liabilities	3,591	5,030
Other accrued expenses	364	927
Total accrued expenses	$ 17,215	$ 16,190

Leases - Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Lessee, Lease, Description [Line Items]
2024	$ 11,890
2025	13,677
2026	13,969
2027	14,351
2028	14,743
Thereafter	88,486
Total lease payments	157,116
Less: tenant improvement allowances	(20,721)
Less: interest	(48,352)
Present value of lease liabilities	$ 88,043	$ 47,611

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Accumulated Other Comprehensive Gain (loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2020		45,804,000
Beginning balance at Dec. 31, 2020	$ 134,260	$ 510,061	$ 14	$ (375,815)
Increase (Decrease) in Shareholders' Equity
Net loss	(7,471)			(7,471)
Stock-based compensation expense	34,322	$ 34,322
Stock option exercises (in shares)		968,000
Stock option exercises	9,928	$ 9,928
Shares issued under the Employee Stock Purchase Plan (in shares)		43,000
Shares issued under the Employee Stock Purchase Plan	1,256	$ 1,256
Issuance of stock for restricted stock unit vesting (shares)		96,000
Restricted stock withheld for employee tax remittance (in shares)		(31,000)
Restricted stock withheld for employee tax remittance	(1,665)	$ (1,665)
Unrealized gain (loss) on investments	(168)		(168)
Ending balance (in shares) at Dec. 31, 2021		46,880,000
Ending balance at Dec. 31, 2021	170,462	$ 553,902	(154)	(383,286)
Increase (Decrease) in Shareholders' Equity
Net loss	(16,709)			(16,709)
Stock-based compensation expense	37,183	$ 37,183
Stock option exercises (in shares)		234,000
Stock option exercises	2,401	$ 2,401
Shares issued under the Employee Stock Purchase Plan (in shares)		49,000
Shares issued under the Employee Stock Purchase Plan	1,251	$ 1,251
Issuance of stock for restricted stock unit vesting (shares)		134,000
Restricted stock withheld for employee tax remittance (in shares)		(44,000)
Restricted stock withheld for employee tax remittance	(1,492)	$ (1,492)
Unrealized gain (loss) on investments	$ (824)		(824)
Ending balance (in shares) at Dec. 31, 2022	47,253,000	47,253,000
Ending balance at Dec. 31, 2022	$ 192,272	$ 593,245	(978)	(399,995)
Increase (Decrease) in Shareholders' Equity
Net loss	(3,182)			(3,182)
Stock-based compensation expense	$ 32,325	$ 32,325
Stock option exercises (in shares)	377,597	378,000
Stock option exercises	$ 4,737	$ 4,737
Shares issued under the Employee Stock Purchase Plan (in shares)		54,000
Shares issued under the Employee Stock Purchase Plan	1,263	$ 1,263
Issuance of stock for restricted stock unit vesting (shares)		224,000
Restricted stock withheld for employee tax remittance (in shares)		(80,000)
Restricted stock withheld for employee tax remittance	(2,341)	$ (2,341)
Unrealized gain (loss) on investments	$ 878		878
Ending balance (in shares) at Dec. 31, 2023	47,829,000	47,829,000
Ending balance at Dec. 31, 2023	$ 225,952	$ 629,229	$ (100)	$ (403,177)

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Summary of valuation of the Company's investments and financial instruments that are measured at fair value on a recurring basis

The following table summarizes the valuation of the Company’s financial instruments that are measured at fair value on a recurring basis:


	December 31, 2023								December 31, 2022
			Fair value measurement category								Fair value measurement category
(In thousands)	Total		Level 1		Level 2		Level 3		Total		Level 1		Level 2		Level 3
Assets:
Money market funds	$	34,672	$	34,672	$	—	$	—	$	1,262	$	1,262	$	—	$	—
Commercial paper (a)	4,876		—		4,876		—		15,606		—		15,606		—
Corporate notes	47,159		—		47,159		—		51,328		—		51,328		—
U.S. government agency bonds (a)	13,971		—		13,971		—		27,976		—		27,976		—
U.S. government securities (a)	24,874		—		24,874		—		$	—	$	—	$	—	$	—
	$	125,552	$	34,672	$	90,880	$	—	$	96,172	$	1,262	$	94,910	$	—

Income Taxes - Summary of Reconciliation of Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of income taxes computed using the federal statutory rate to the taxes reported in consolidated statements of operations
Loss before income taxes	$ (2,368)	$ (15,988)	$ (7,471)
Federal statutory rate	21.00%	21.00%	21.00%
Taxes computed at federal statutory rate	$ (497)	$ (3,357)	$ (1,569)
State and local income taxes	(389)	(630)	(345)
Nondeductible stock-based compensation	(586)	1,168	(4,311)
Federal and state rate change	(704)	574	47
Research and orphan drug credits	362
Research and orphan drug credits		(644)	(413)
Other	162	267	(87)
Change in valuation allowance	2,466	3,343	6,567
Reported income taxes	$ 814	$ 721	$ (111)

Shareholder's Equity - Narrative (Details) $ in Millions	Aug. 27, 2021 USD ($)
Shareholders' Equity
At the market offering, sales agreement, expiration period	3 years
At The Market
Shareholders' Equity
Sale of stock authorized value	$ 200.0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

The components of loss before income taxes are summarized as follows:


	Year Ended December 31,
(In thousands)	2023		2022		2021
U.S.	$	(2,381)	$	(15,912)	$	(7,367)
Foreign	13		(76)		(104)
Loss before income taxes	$	(2,368)	$	(15,988)	$	(7,471)

A reconciliation of income taxes computed using the U.S. federal statutory rate to the taxes reported in the consolidated statements of operations is as follows:


	Year Ended December 31,
(In thousands)	2023			2022			2021
Loss before income taxes	$	(2,368)		$	(15,988)		$	(7,471)
Federal statutory rate	21		%	21		%	21		%
Taxes computed at federal statutory rate	(497)			(3,357)			(1,569)
State and local income taxes	(389)			(630)			(345)
Nondeductible stock-based compensation	(586)			1,168			(4,311)
Federal and state rate change	(704)			574			47
Research and orphan drug credits	362			(644)			(413)
Other	162			267			(87)
Change in valuation allowance	2,466			3,343			6,567
Reported income taxes	$	814		$	721		$	(111)

Deferred tax assets (liabilities) consist of the following:


	Year Ended December 31,
(In thousands)	2023		2022
Deferred tax assets:
Net operating loss carryforwards	$	4,505	$	7,020
Employee benefits and stock-based compensation	24,812		18,028
Research and development costs	5,176		7,530
Intangible assets	962		1,770
Operating lease liabilities	20,849		11,846
Inventory reserve	3,570		2,780
Tax credit carryforward	10,781		11,143
Other, net	12		12
Total deferred tax assets	70,667		60,129
Less: valuation allowance	(49,755)		(47,290)
Total net deferred tax assets	20,912		12,839
Deferred tax liabilities:
Right-of-use assets	(19,296)		(10,891)
Property and equipment, net	(1,616)		(1,948)
Total net deferred tax liabilities	(20,912)		(12,839)
Net deferred tax assets and liabilities	$	—	$	—

As of December 31, 2023, the Company had U.S. federal net operating loss carryforwards of $11.7 million, of which $8.3 million begin to expire in 2033 and the remainder do not expire but are subject to 80% limitation. As of December 31, 2023, the Company had state net operating loss carryforwards of $16.6 million that begin to expire in 2034. The projected annual limitation on the use of the net operating losses that existed prior to September 17, 2014 resulting from the Company’s change in control in 2014 per Section 382 of the Internal Revenue Code is $0.8 million. As a result, a significant portion of the net operating losses and tax credit carryforwards will expire prior to their utilization, regardless of the level of future profitability. As of December 31, 2023, the Company’s U.S. federal tax credit carryforwards available to offset future profits are $10.8 million. These credit carryforwards expire between 2034 and 2043.

In accordance with the accounting guidance for income taxes, the Company estimates whether recoverability of its deferred tax assets is “more likely than not”, based on forecasts of taxable income in the related tax jurisdictions. In this estimate, the Company uses historical results, projected future operating results based upon approved business plans, eligible carry forward periods, tax planning opportunities and other relevant considerations. Based on these factors, including historical losses incurred by the Company, a full valuation allowance for the deferred tax assets, including the deferred tax assets for the aforementioned net operating losses and credits has been provided, since they are not more likely than not to be realized. If sufficient positive evidence exists in future periods to support a release of some or all of the valuation allowance, such a release would likely have a material impact on the Company’s results of operations. The change in the valuation allowance was an increase of $2.5 million and $3.3 million for the years ended December 31, 2023 and 2022, respectively.

The Company assesses uncertain tax positions in accordance with the guidance for accounting for uncertain tax positions. This pronouncement prescribes a recognition threshold and measurement methodology for recording within the consolidated financial statements uncertain tax positions taken, or expected to be taken, in the Company’s income tax returns. To the extent the uncertain tax positions do not meet the “more likely than not” threshold, the Company derecognizes such positions. To the extent the uncertain tax positions meet the “more likely than not” threshold, the Company measures and records the highest probable benefit, and establishes appropriate reserves for benefits that exceed the amount likely to be sustained upon examination. The Company currently has not recorded any uncertain tax positions and does not anticipate that unrecognized tax benefits will significantly increase or decrease within the next twelve months.

The Company files U.S. federal and state income tax returns with varying statute of limitations. During the year-ended December 31, 2020, examinations by U.S. tax authorities were completed for 2017 and 2018. Due to the Company’s net operating loss carryforwards, federal income tax returns from incorporation are still subject to examination. The Company files in several state tax jurisdictions and is subject to examination in years ranging from incorporation to 2023.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Income (Loss) Attributable to Parent [Abstract]
Net loss	$ (3,182)	$ (16,709)	$ (7,471)
Basic weighted-average common shares outstanding (in shares)	47,590	47,130	46,472
Effect of dilutive stock options and restricted stock units (in shares)	0	0	0
Diluted weighted-average common shares outstanding (in shares)	47,590	47,130	46,472
Basic loss per common share (in USD per share)	$ (0.07)	$ (0.35)	$ (0.16)
Diluted loss per common share (in USD per share)	$ (0.07)	$ (0.35)	$ (0.16)
Stock options
Anti-dilutive shares excluded from diluted net loss per common share:
Anti-dilutive shares excluded from the calculation of diluted earnings per share (in shares)	6,717	6,609	5,670
Restricted stock units
Anti-dilutive shares excluded from diluted net loss per common share:
Anti-dilutive shares excluded from the calculation of diluted earnings per share (in shares)	931	648	399

Revenue - Schedule Of Concentration Of Credit Risk (Details) - Customer One - Customer concentration	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Revenue Concentration
Disaggregation of Revenue [Line Items]
Concentration risk (as a percent)	11.00%	12.00%
Accounts Receivable Concentration
Disaggregation of Revenue [Line Items]
Concentration risk (as a percent)	13.00%	10.00%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Income Taxes - Deferred Tax Assets (Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 4,505	$ 7,020
Employee benefits and stock-based compensation	24,812	18,028
Research and development costs	5,176	7,530
Intangible assets	962	1,770
Operating lease liabilities	20,849	11,846
Inventory reserve	3,570	2,780
Tax credit carryforward	10,781	11,143
Other, net	12	12
Total deferred tax assets	70,667	60,129
Less: valuation allowance	(49,755)	(47,290)
Total net deferred tax assets	20,912	12,839
Deferred tax liabilities:
Right-of-use assets	(19,296)	(10,891)
Property and equipment, net	(1,616)	(1,948)
Total net deferred tax liabilities	(20,912)	(12,839)
Net deferred tax assets and liabilities	$ 0	$ 0

Commitments and Contingencies - Future Minimum Payments (Details) $ in Thousands, € in Millions	Dec. 31, 2023 USD ($)	Jul. 31, 2023 EUR (€)
Purchase commitments
Total	$ 19,329
2024	8,271	€ 12.5
2025	1,512
2026	1,611
2027	1,909
2028	2,009
More than 5 Years	4,017
Warehouse operating agreement
Total	3,795
2024	1,850
2025	746
2026	788
2027	411
2028	0
More than 5 Years	0
Contractual Obligation, Fiscal Year Maturity [Abstract]
Total	23,124
2024	10,121
2025	2,258
2026	2,399
2027	2,320
2028	2,009
More than 5 Years	$ 4,017

Revenue - Narrative (Details) $ in Millions		12 Months Ended
Revenue - Narrative (Details) $ in Millions	May 09, 2023 USD ($)	Dec. 31, 2023 USD ($) pharmacy	Dec. 31, 2022 USD ($)
Disaggregation of Revenue [Line Items]
Number of specialty pharmacies \| pharmacy		2
Allowance for doubtful accounts		$ 5.6	$ 6.1
Change in estimate of uncollectible (percent)		0.50%
Change in revenue recognized due to 0.5% change in uncollectible percentage		$ 0.4
MediWound Ltd
Disaggregation of Revenue [Line Items]
Additional funding	$ 3.0
Additional funding	$ 3.0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

Stock-Based Compensation - Schedule of fair value assumptions (Details) - Stock options - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stock-Based Compensation
Expected dividend rate	0.00%	0.00%	0.00%
Expected stock price volatility, minimum	62.50%	63.80%	71.50%
Expected stock price volatility, maximum	66.70%	75.30%	76.70%
Risk-free interest rate, minimum	3.40%	1.50%	0.53%
Risk-free interest rate, maximum	4.70%	4.40%	1.50%
Expected life (years)	5 years 6 months
Weighted average grant-date fair value (in USD per share)	$ 18.85	$ 19.83	$ 32.96
Minimum
Stock-Based Compensation
Expected life (years)		5 years 3 months 18 days	5 years 3 months 18 days
Maximum
Stock-Based Compensation
Expected life (years)		6 years 3 months 18 days	6 years 3 months 18 days

Organization (Details) $ in Thousands	12 Months Ended
Organization (Details) $ in Thousands	Dec. 31, 2023 USD ($) product segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of commercial-stage products \| product	3
Number of reportable segments \| segment	1
Accumulated deficit	$ 403,177	$ 399,995
Net loss	3,182	16,709	$ 7,471
Cash and cash equivalents	69,088	$ 51,067	$ 68,330
Short term investments	$ 65,800

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

- Definition

Amount of accumulated undistributed earnings (deficit).

+ References + Details

Leases - Narrative (Details) ft² in Thousands, $ in Thousands			1 Months Ended	12 Months Ended
	Jun. 01, 2023 USD ($) renewal_option $ / ft²	Jul. 29, 2022 USD ($)	Jan. 31, 2022 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Apr. 30, 2023 USD ($)	Jan. 28, 2022 ft²
Lessee, Lease, Description [Line Items]
Right-of-use assets				$ 73,462	$ 41,535
Short-term lease costs (less than)				100	100	$ 100
Operating lease expense				10,300	6,900	7,300
Finance lease expense (less than)				100	100	100
Measurement of lease liability				1,700	$ 5,300	$ 6,000
Ann Arbor, Michigan \| Minimum
Lessee, Lease, Description [Line Items]
Monthly contractual lease payments				17
Ann Arbor, Michigan \| Maximum
Lessee, Lease, Description [Line Items]
Monthly contractual lease payments				18
25 Network Drive, Burlington, Massachusetts
Lessee, Lease, Description [Line Items]
Area of real estate property \| ft²								126
Percent contributed to escrow account							50.00%
Escrow deposit amount							$ 28,300
Remaining percent to be contributed to escrow account							50.00%
Rent start date, term	13 months
Term of contract	144 months
Number of renewal options \| renewal_option	1
Lease option to extend term	10 years
Annual lease per square foot \| $ / ft²	57
Annual lease base rent square subject to increase percentage	2.50%
Tenant improvement allowance per square foot \| $ / ft²	200
Tenant improvement allowance	$ 24,400
Right-of-use assets	35,500			$ 2,000
Present value of lease liabilities	$ 35,500
Estimated incremental borrowing rate	0.077
Term of contract	13 years 1 month 6 days
Letter of credit cash deposit			$ 6,000
Letter of credit cash deposit lease year three		$ 4,200
Letter of credit cash deposit lease year six		$ 1,800
25 Network Drive, Burlington, Massachusetts \| Minimum
Lessee, Lease, Description [Line Items]
Monthly contractual lease payments	$ 600
25 Network Drive, Burlington, Massachusetts \| Maximum
Lessee, Lease, Description [Line Items]
Monthly contractual lease payments	$ 800