Vericel (VCEL) 10-K 25 Feb 20 2019 FY Annual report Financial data

Cover Page

Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 21, 2020	Jun. 30, 2019
Cover page.
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-35280
Entity Registrant Name	VERICEL CORPORATION
Entity Incorporation, State or Country Code	MI
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	MA
Entity Address, Postal Zip Code	02139
City Area Code	800
Local Phone Number	556-0311
Title of 12(b) Security	Common Stock (No par value)
Trading Symbol	VCEL
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Public Float			$ 827,617,275
Entity Common Stock, Shares Outstanding		44,945,133
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Document Form 10-K Reference Proxy Statement for the Annual Meeting of Shareholders scheduled for April 29, 2020 Items 10, 11, 12, 13 and 14 of Part III
Entity Central Index Key	0000887359
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Small Business	false
Entity Emerging Growth Company	false

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 26,889	$ 18,286
Short term investments	42,829	64,638
Accounts receivable (net of allowance for doubtful accounts of $306 and $514, respectively)	32,168	23,454
Inventory	6,816	3,558
Other current assets	2,953	2,847
Total current assets	111,655	112,783
Property and equipment, net	7,144
Property and equipment, net		5,906
Restricted cash	89	0
Right-of-use assets	25,103
Long term investments	9,247	0
Total assets	153,238	118,689
Current liabilities:
Accounts payable	6,345	7,108
Accrued expenses	7,948	6,930
Current portion of operating lease liabilities	5,461
Other liabilities	41	754
Total current liabilities	19,795	14,792
Operating lease liabilities	22,242
Other long-term liabilities	110	1,666
Total liabilities	42,147	16,458
COMMITMENTS AND CONTINGENCIES
Shareholders’ equity:
Common stock, no par value; shares authorized — 75,000; shares issued and outstanding — 44,864 and 43,578, respectively	489,749	471,180
Other comprehensive gain (loss)	21	(39)
Warrants	0	104
Accumulated deficit	(378,679)	(369,014)
Total shareholders’ equity	111,091	102,231
Total liabilities and shareholders’ equity	$ 153,238	$ 118,689

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 306	$ 514
Common stock, shares authorized (in shares)	75,000,000	75,000,000
Common stock, shares issued (in shares)	44,864,000	43,578,000
Common stock, shares outstanding (in shares)	44,864,000	43,578,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Product sales, net	$ 117,850	$ 90,857	$ 62,760
Other revenue	0	0	1,164
Total revenue	117,850	90,857	63,924
Cost of product sales	37,571	32,160	30,354
Gross profit	80,279	58,697	33,570
Research and development	30,391	13,599	12,944
Selling, general and administrative	61,139	49,007	35,610
Total operating expenses	91,530	62,606	48,554
Loss from operations	(11,251)	(3,909)	(14,984)
Other income (expense):
Increase in fair value of warrants	0	(2,524)	(257)
Loss on extinguishment of debt	0	(838)	(860)
Interest income	1,614	897	14
Interest expense	(8)	(1,732)	(1,107)
Other expense	(20)	(31)	(92)
Total other income (expense)	1,586	(4,228)	(2,302)
Net loss	$ (9,665)	$ (8,137)	$ (17,286)
Net loss per share attributable to common shareholders (Basic and Diluted) (in dollars per share)	$ (0.22)	$ (0.20)	$ (0.52)
Weighted average number of common shares outstanding (Basic and Diluted) (in shares)	44,180	40,242	33,355

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (9,665)	$ (8,137)	$ (17,286)
Other comprehensive income (loss):
Unrealized gain (loss) on investments	60	(39)	0
Comprehensive loss	$ (9,605)	$ (8,176)	$ (17,286)

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Treasury Stock	Warrants	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2016		12,000	31,595,000	0
Beginning balance at Dec. 31, 2016	$ 24,708	$ 38,389	$ 329,720	$ 0	$ 190	$ 0	$ (343,591)
Increase (Decrease) in Shareholders' Equity
Net loss	(17,286)						(17,286)
Conversion of Series B-1 or B-2 preferred stock for common stock (in shares)		(12,000)	1,094,000
Conversion of Series B-1 or B-2 preferred stock for common stock	0	$ (38,389)	$ 38,389
Compensation expense related to stock options granted, net of forfeitures	2,680		$ 2,680
Issuance of common stock, net of issuance costs (in shares)			1,983,000
Issuance of common stock, net of issuance costs	7,188		$ 7,188
Stock option exercises (in shares)			199,000
Stock option exercises	608		$ 608
Shares issued under the Employee Stock Purchase Plan (in shares)			173,000
Shares issued under the Employee Stock Purchase Plan	425		$ 425
Issuance of warrants	207				207
Exercise of warrants resulting in issuance of common stock (Note 11) (in shares)			817,000
Exercise of warrants resulting in issuance of common stock	4,010		$ 4,010
Net change in unrealized (gain) loss on investments	0
Ending balance (in shares) at Dec. 31, 2017		0	35,861,000	0
Ending balance at Dec. 31, 2017	22,540	$ 0	$ 383,020	$ 0	397	0	(360,877)
Increase (Decrease) in Shareholders' Equity
Net loss	(8,137)						(8,137)
Compensation expense related to stock options granted, net of forfeitures	7,223		$ 7,223
Issuance of common stock, net of issuance costs (in shares)			5,750,000
Issuance of common stock, net of issuance costs	70,028		$ 70,028
Stock option exercises (in shares)			1,180,000
Stock option exercises	3,705		$ 3,705
Shares issued under the Employee Stock Purchase Plan (in shares)			106,000
Shares issued under the Employee Stock Purchase Plan	656		$ 656
Exercise of warrants resulting in issuance of common stock (Note 11) (in shares)			681,000
Exercise of warrants resulting in issuance of common stock	6,255		$ 6,548		(293)
Net change in unrealized (gain) loss on investments	(39)					(39)
Ending balance (in shares) at Dec. 31, 2018		0	43,578,000	0
Ending balance at Dec. 31, 2018	102,231	$ 0	$ 471,180	$ 0	104	(39)	(369,014)
Increase (Decrease) in Shareholders' Equity
Net loss	(9,665)						(9,665)
Compensation expense related to stock options granted, net of forfeitures	$ 13,179		$ 13,179
Stock option exercises (in shares)	1,197,016		1,197,000
Stock option exercises	$ 4,354		$ 4,354
Shares issued under the Employee Stock Purchase Plan (in shares)			69,000
Shares issued under the Employee Stock Purchase Plan	932		$ 932
Exercise of warrants resulting in issuance of common stock (Note 11) (in shares)			20,000
Exercise of warrants resulting in issuance of common stock	0		$ 104		(104)
Net change in unrealized (gain) loss on investments	60					60
Ending balance (in shares) at Dec. 31, 2019		0	44,864,000
Ending balance at Dec. 31, 2019	$ 111,091		$ 489,749		$ 0	$ 21	$ (378,679)

CONSOLIDATED STATEMENTS OF SH_2

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement of Stockholders' Equity [Abstract]
Issuance of stock, issuance cost	$ 4,700	$ 311,000

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities:
Net loss	$ (9,665)	$ (8,137)	$ (17,286)
Adjustments to reconcile net loss to net cash used for operating activities:
Depreciation and amortization	1,744	1,426	1,612
Stock compensation expense	13,179	7,223	2,680
Change in fair value of warrants	0	2,524	257
Loss on extinguishment of debt	0	838	860
Foreign currency translation loss	42	51	37
Gain (loss) on sale of fixed assets	0	22	(115)
Amortization of premiums and discounts on marketable securities	(610)	(327)	0
Non-cash lease cost	2,787	0	0
Changes in operating assets and liabilities:
Inventory	(3,258)	235	(305)
Accounts receivable	(8,714)	(5,184)	(1,177)
Prepaid and other current assets	(106)	(1,267)	(261)
Accounts payable	(1,024)	899	(1,361)
Accrued expenses	1,018	1,493	1,050
Operating lease liabilities	(2,512)
Other non-current assets and liabilities, net	(64)	(208)	826
Net cash used for operating activities	(7,183)	(412)	(13,183)
Investing activities:
Purchases of short term investments	(63,092)	(66,549)	0
Maturities of short term investments	85,577	2,200	0
Purchases of long term investments	(9,254)	0	0
Expenditures for property, plant and equipment	(2,616)	(2,678)	(1,510)
Net cash provided by (used for) investing activities	10,615	(67,027)	(1,510)
Financing activities:
Net proceeds from equity offering	0	70,028	0
Net proceeds from common stock issuance due to stock option exercises	5,286	4,361	8,220
Deferred financing costs	0	0	(30)
Proceeds from exercise of warrants	0	2,716	4,010
Borrowings under revolving and term loan credit agreements	0	0	14,793
Warrants issued in connection with debt arrangement	0	0	207
Payments on term loan credit agreement	0	0	(889)
Payments on long-term debt	0	(17,532)	(7,151)
Fee on long-term debt	0	(710)	(583)
Other	(26)	0	0
Net cash provided by financing activities	5,260	58,863	18,577
Net increase (decrease) in cash, cash equivalents, and restricted cash	8,692	(8,576)	3,884
Cash, cash equivalents, and restricted cash at beginning of period	18,286	26,862	22,978
Cash, cash equivalents, and restricted cash at end of period	$ 26,978	$ 18,286	$ 26,862

Organization

Organization	12 Months Ended
	Dec. 31, 2019
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, Vericel, we, us or our), was incorporated in March 1989 and began employee-based operations in 1991. On May 30, 2014, Vericel completed the acquisition of certain assets and assumed certain liabilities of Sanofi, a French société anonyme (Sanofi), including all of the outstanding equity interests of Genzyme Biosurgery ApS (Genzyme Denmark or the Danish subsidiary) (now known as Vericel Denmark ApS), a wholly-owned subsidiary of Sanofi, and a portfolio of patents and patent applications of Sanofi and certain of its subsidiaries for purposes of acquiring the portion of the cell therapy and regenerative medicine business (the CTRM Business), related to the MACI ® , Carticel ® and Epicel ® products. The Company is a fully integrated, commercial-stage biopharmaceutical company and currently markets MACI ® and Epicel ® in the U.S. and holds exclusive rights to commercialize NexoBrid ® in all countries of North America. The Company is a leader in advanced cell therapies for the sports medicine and severe burn care markets. 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 that was approved by the FDA on December 13, 2016. The first shipment and implantation of MACI occurred on January 31, 2017. At the end of the second quarter of 2017, the Company removed Carticel ® (autologous cultured chondrocytes), an earlier generation ACI product, from the market. The Company also markets Epicel ® (cultured epidermal autografts), a permanent skin replacement Humanitarian Use Device (HUD) 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 operates its business primarily in the U.S. in one reportable segment — the research, product development, manufacture and distribution of cellular therapies for use in the treatment of specific diseases. 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 satisfaction of liabilities and commitments in the normal course of business. As of December 31, 2019 , the Company has an accumulated deficit of $378.7 million and had a net loss of $9.7 million during 2019. The Company had cash and cash equivalents of $26.9 million and investments of $52.1 million as of December 31, 2019 . The Company expects that existing cash, cash equivalents and investments will be sufficient to support the Company’s current operations through at least 12 months from the issuance of these financial statements. If revenues decline for a sustained period, we may need to access additional capital; however, the Company may not be able to obtain financing on acceptable terms or at all. The terms of any financing may adversely affect the holdings or the rights of the Company’s shareholders.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Principles of Consolidation The consolidated financial statements include the accounts of Vericel and its wholly-owned subsidiaries, Vericel Denmark ApS, in Kastrup, Demark and Vericel Security Corporation (collectively, the Company). All inter-company transactions and accounts have been eliminated in consolidation. Vericel Denmark ApS ceased operations in 2015. Use of Estimates The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reported period. Actual results could differ from those estimates. Consolidated Statement of Cash Flows The following table presents certain supplementary cash flows information for the years ended December 31, 2019 , 2018 and 2017 : Year Ended December 31, (In thousands) 2019 2018 2017 Supplementary Cash Flows information: Non-cash information: Warrants exercised for common stock $ 104 $ 3,538 $ — Right-of-use asset and lease liability recognized 2,599 — — Additions to equipment in process included in accounts payable 217 606 341 Shares exchanged between common and preferred stock — — (38,389 ) Cash information: Interest paid (net of interest capitalized) $ — $ 2,230 $ 931 Income tax withholding paid — — 100 Total cash, cash equivalents, and restricted cash of $27.0 million shown in the statement of cash flows is comprised of cash and cash equivalents of $26.9 million and restricted cash of $0.1 million which is included in other long term assets on the consolidated balance sheet. 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, overnight repurchase agreements and short duration agency bonds and commercial paper. Restricted cash Amounts included in restricted cash represent those required to be set aside to meet contractual terms of a lease agreement held by the Company. Investments Short-term investments consist of debt securities classified as available-for-sale and have maturities greater than 90 days, but less than one year as of the balance sheet date. Long-term investments consist of debt securities classified as available-for-sale and have maturities greater than one year as of the balance sheet date. All investments are carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • 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). Unrealized gains and losses on available-for-sale securities are excluded from earnings and are reported as a component of accumulated other comprehensive loss. The cost of available-for-sale securities sold is based on the specific-identification method. Realized gains and losses are included in earnings, and are derived for specific-identification method for determining the costs of investments sold. If a decline in the fair value is considered other-than-temporary, based on available evidence, the unrealized loss is reclassified from accumulated other comprehensive income (loss) to the statements of operations. Realized gains and losses are determined on the specific identification method and are included in investment and other income, net. 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 write-down obsolete or other unmarketable inventory to its estimated net realizable value. If the actual net realizable value is less than that estimated by us, 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 sales. Leases The Company adopted the new leasing standards using the modified retrospective transition approach, as of January 1, 2019, with no restatement of prior periods. Upon adoption all operating lease commitments with a lease term greater than 12 months that were previously assessed under the prior lease guidance, were recognized as right to 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. Adoption of ASU 2016-02 resulted in the recording of additional right-of-use assets and lease liabilities of approximately $25.6 million and $27.8 million, respectively, as of January 1, 2019. Certain lease agreements include rental payments that are adjusted periodically for inflation or other variables. The leases are initially measured using 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 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. Some leases contain clauses for renewal at the Company’s option with renewal terms that generally extend the lease term from 1 to 5 years . Certain lease agreements contain options to purchase the leased property and options to terminate the lease. Payments to be made in option periods are recognized as part of the right-of-use lease assets and lease liabilities when it is reasonably certain that the option to extend the lease will be exercised or the option to terminate the lease will not be exercised, or is not at the Company’s option. The Company determines whether the reasonably certain threshold is met by considering contract-, asset-, market-, and entity-based factors. A portfolio approach is applied to certain lease contracts with similar characteristics. The Company’s lease agreements do not contain any significant residual value guarantees or material restrictive covenants imposed by the leases. 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. Property, Plant and Equipment Property, plant and equipment are initially measured and recognized at acquisition cost, including any directly attributable cost of preparing the asset for its intended use or, in the case of assets acquired in a business combination, at fair value as at the date of the combination. After initial measurement, property, plant and equipment are carried at cost less accumulated depreciation and impairment. Repair and maintenance costs of property, plant and equipment are expensed as incurred. The depreciable value of property, plant and equipment, net of any residual value, 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, plant and equipment are as follows: • Equipment and computers: 3 to 5 years • Furniture and fixtures: 5 years • Building improvements and leasehold improvements: Shorter of the remaining life of the lease or 10 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. Revenue Recognition and Net Product Sales The new revenue standard became effective for the Company on January 1, 2018, and was adopted using the modified retrospective method. Based on the Company’s evaluation of all of its product revenue contracts under the new revenue standard there was no cumulative adjustment recorded in the financial statements upon adoption of Accounting Standards Codification 606, Revenue Recognition, (ASC 606) on January 1, 2018. For the year ended December 31, 2018 , the timing and amount of revenue recognized under ASC 606 was not materially different from that under the previous guidance. The Company recognizes product revenue from sales to a customer (distributor or hospital) following the five step model in 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, kits, or Epicel as of December 31, 2019 ; 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. Currently, for MACI, MACI kits and Epicel there are no variable pricing arrangements related to warranties or rebates offered to customers. The majority of orders are due within 60 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 activities represent a significant part of the Company’s business. 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. Research and development expenses are expensed as incurred. 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 Company uses the value of its common stock at the date of the grant in the calculation of the fair value of its share-based awards. The fair value of restricted stock units held by the employees is determined based on the fair value of the Company's common stock on the date of the grant. The fair value of stock options held by the employees is determined using a Black-Scholes option valuation method, which is a valuation technique that is acceptable for share-based payment accounting. 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 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 recognize 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. For certain non-employee consultants, stock option awards continue to vest post-termination. 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 purchase options at the grant date, which corresponds to the first day of each purchase period, and is amortized over the purchase period. Comprehensive Loss Comprehensive loss is the change in stockholders’ equity during a period arising from any gain or loss unrealized 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, that a portion or all of the deferred tax assets will not be realized. 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 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 Earnings (Loss) Per Share Attributable to Common Shareholders Basic and diluted earnings (loss) per share is calculated using the two-class method. Basic earnings (loss) per share which is based on an earnings allocation formula that determines earnings (loss) per share for the holders of the Company’s common shares. There were no undeclared dividends for the year ended December 31, 2019 or 2018 . Diluted earnings (loss) per share includes convertible securities or common equivalent share (stock options and warrants) in addition to the Company’s common shares. Common equivalent shares and treasury stock are not included in the diluted per share calculation where the effect of their inclusion would be anti-dilutive. Financial Instruments The Company’s financial instruments include receivables 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. Warrants Warrants that could be cash settled or have anti-dilution price protection provisions are recorded as liabilities at their estimated fair value at the date of issuance, with subsequent changes in estimated fair value recorded in other income (expense) in our statement of operations in each subsequent period. Warrants that meet the requirements for equity classification are recorded at fair value with no subsequent remeasurement. In general, warrants are measured using the Black-Scholes valuation model. The methodology is based, in part, upon inputs for which there is little or no observable market data, requiring the Company to develop its own assumptions. The assumptions used in calculating the estimated fair value of the warrants represent our best estimates; however, these estimates involve inherent uncertainties and the application of management judgment. As a result, if factors change and different assumptions are used, the change in estimated fair value of the warrant liability for those warrants that could be cash settled or have anti-dilution price protection provisions, could be materially different. As of December 31, 2019, there were no outstanding warrants.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2019
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting for Leases The Financial Accounting Standards Board (FASB) issued guidance to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. In accordance with the updated guidance, lessees are required to recognize the assets and liabilities arising from operating leases on the balance sheet. The guidance is effective for annual reporting periods beginning after December 15, 2018. The Accounting Standard Update 2016-02, Leases (Topic 842) , became effective for the Company on January 1, 2019 and was adopted using the modified retrospective method. See note 7 for further discussion. Measuring Credit Losses on Financial Instruments The FASB issued updated guidance on measuring credit losses on financial instruments. The guidance removes the thresholds that companies apply to measure credit losses on financial instruments measured at amortized cost, such as loans, receivables, and held-to-maturity debt securities. Prior to the updated guidance, credit losses are recognized when it is probable that the loss has been incurred. The revised guidance removes all recognition thresholds and requires companies to recognize an allowance for credit losses for the difference between the amortized cost basis of a financial instrument and the amount of amortized cost that a company expected to collect over the instrument’s contractual life. This guidance will be issued through Accounting Standard Update 2016-13, Financial Instruments-Credit Losses (Topic 326), which will be effective for the Company January 1, 2020. The Company is currently in the process of evaluating the impact to its consolidated financial statements. Fair Value Measurement Disclosure The FASB issued updated guidance through ASU 2018-13, Fair Value Measurement (Topic 820) Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement. The revised guidance is intended to develop a more consistent disclosure framework that will increase clarity, remove, modify and add certain fair value disclosures to improve the effectiveness of the Company’s disclosures in the notes of the financial statements. This guidance will be effective for the Company January 1, 2020. The Company is currently in the process of evaluating the impact to its consolidated financial statements. Simplifying the Accounting for Income Taxes In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (ASC 740). The ASU enhances and simplifies various aspects of the income tax accounting guidance in ASC 740, including requirements related to hybrid tax regimes, the tax basis step-up in goodwill obtained in a transaction that is not a business combination, separate financial statements of entities not subject to tax, the intra-period tax allocation exception to the incremental approach, ownership changes in investments, changes from a subsidiary to an equity method investment, interim-period accounting for enacted changes in tax law, and the year-to-date loss limitation in interim-period tax accounting. This guidance is effective for the Company for annual and interim periods beginning after December 31, 2020; however, early adoption is permitted. The Company is currently in the process of evaluating the impact to its consolidated financial statements.

Revenue

Revenue	12 Months Ended
	Dec. 31, 2019
Risks and Uncertainties [Abstract]
Revenue	Revenue Revenue Recognition and Net Product Sales As disclosed in note 2, the Company recognizes product revenue from sales of MACI Kits, MACI implants and Epicel grafts following the five-step model in Accounting Standards Codification 606, Revenue Recognition, (ASC 606). MACI Kits MACI kits are sold directly to hospitals based on contracted rates in the 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 provides the doctor the ability to biopsy a sampling of cells to provide to the Company that can be used later to manufacture the implant. The ordering of the kit does not obligate the Company to manufacture an implant nor does the receipt of the cell tissue. The customer’s order of an implant is separate from the process of ordering the kit. Therefore, the sale of the kit and any subsequent sale of an implant are distinct contracts and are accounted for separately. MACI Implants From July 1, 2017 until June 15, 2018 the Company sold MACI primarily to distributors and directly to hospitals or patients at contracted rates. Beginning on June 16, 2018, the Company contracted with a specialty pharmacy, Orsini Pharmaceutical Services, Inc. (Orsini) to distribute its MACI product in arrangements whereby the Company retains the credit and collection risk from the end customer. Since July 26, 2018, the Company has also contracted with AllCare Plus Pharmacy, Inc. (AllCare), a specialty pharmacy, in arrangements whereby the Company retains the credit and collection risk from the end customer. The Company pays both specialty pharmacies a fee for each patient to whom MACI is dispensed. Both Orsini and AllCare perform collection activities to receive payment from customers. The Company has engaged a third-party to provide services in connection with a patient support program to manage patient cases and to ensure complete and correct billing information is provided to the insurers and hospitals. In addition, the Company also sells MACI directly to DMS Pharmaceutical (DMS) for all military implants in 2019 and 2018. The Company sold MACI directly to UsBio Services (UsBio) for all military implants in 2017. The sales directly to DMS and UsBio are sold at a contracted rate. 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 revenues 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 which 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 other than customary prompt pay discounts, there are typically no forms of variable consideration. When the Company sells MACI the patient is responsible for payment, however, 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, government fee schedules or past payer precedents. Net product revenue is recognized net of contractual allowances, which considers historical collection experience from both the payer and patient and the terms of the Company’s contractual arrangements. The Company estimates the amount of consideration it expects to receive for these transactions using the portfolio approach. These estimates include the impact of 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 records a reduction to revenue at the time of sale for its estimate of the amount of consideration that will not be collected. The allowance for uncollectible consideration was $3.9 million and $2.0 million as of December 31, 2019 , and 2018 , respectively. Changes to the estimate of the amount of consideration that will not be collected could have a material impact to the revenue recognized. A 0.5% change to the estimated uncollectible percentage could result in approximately a $0.5 million decrease or increase in the revenue recognized for the year ended December 31, 2019 . 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 period sales resulted in an increase to revenue of $0.7 million and decrease of $0.2 million and $0.4 million for the years ended December 31, 2019 , 2018 , and 2017 respectively. Epicel The Company sells Epicel directly to hospitals based on contracted rates stated in the approved contract or purchase order. Similar to MACI, there is no obligation to manufacture skin 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 revenues from sales of Epicel upon delivery to the hospital at which time the customer is in control of the skin grafts and the claim is billable to the hospital. Other Revenue The Company recognizes other revenue from contracts with customers related to license grants, milestone related payments and royalty-based payments by following the five-step model described in note 2. On May 10, 2017, the Company announced that it entered into a License Agreement (License Agreement) with Innovative Cellular Therapeutics CO., LTD. (ICT), a leading cell therapy company and developer of CAR-T cell therapy for cancer treatment, for the development, manufacturing and commercialization of the Company’s product portfolio in Greater China, South Korea, Singapore, and other countries in Asia. ICT acquired an exclusive license to certain patent rights, know-how and intellectual property relating to Carticel, MACI, ixmyelocel-T, and Epicel for the purpose of developing, manufacturing and commercializing the Company's products in the territory described above. The initiation of the technology transfer, the license grants in the License Agreement and the warrant purchase were contingent upon the Company’s receipt of the upfront payment. ICT will be responsible for funding the development of the programs and manufacturing of the products for commercialization in China and the rest of the territory. On December 21, 2017, the Company received $5.2 million (gross of withholding tax), of which $4.0 million was allocated to the warrant based on the fair value on the date of grant as described in note 12 and the remaining $1.2 million was recognized as described below. The license was delivered in December 2017, and revenue of $1.2 million was recorded in 2017 under the then applicable revenue accounting standard ASC 605. Based upon the Company’s evaluation under ASC 606 there was no change in amount or timing of revenue recognized for the agreement, and therefore no cumulative change adjustment was recorded upon adoption of the new revenue standard on January 1, 2018. The Company has no significant performance obligations remaining under the agreement. The License Agreement provides for future milestone payments due to the Company upon the achievement of certain developmental and commercial events. The Company evaluates these milestones under the new revenue recognition standard at contract inception and at each reporting period date. Based on the Company’s evaluations to date, the Company has not included any of the future milestones in its determination of the transaction price because the criteria for including these variable payments have not yet been met. This evaluation was based on 1) the pace and eventual achievement of the milestones are largely dependent on ICT’s performance of its contractual obligations and the Company has no prior experience to determine the likelihood of ICT performing those obligations, and 2) the transfer of the funds for each of the milestone payments by ICT to the Company, if achieved, is subject to approval by the State Administration of Foreign Exchange of the People’s Republic of China. The License Agreement contains future sales-based royalties to the Company in the low-to-mid double digits. These royalties meet the exception for sales-based or usage-based royalties because they predominantly relate to the license and will be recognized when and if the subsequent sales occur. As of December 31, 2019, we have not received any payments under the License Agreement. Revenue by Product and Customer The following table and description below shows the products from which the Company generated its revenue: Year Ended December 31, Revenue by product (in thousands) 2019 2018 2017 MACI and Carticel implants and kits Implants based on contracted rate sold through a specialty pharmacy (a) $ 56,185 $ 42,926 $ 37,796 Implants subject to third party reimbursement sold through a specialty pharmacy (b) 17,076 8,621 1,299 Implants sold direct based on contracted rates (c) 13,933 12,122 3,393 Implants sold direct subject to third party reimbursement (d) 1,529 2,257 — Biopsy kits - direct bill 2,243 1,997 1,764 Change in estimates related to prior periods 654 (182 ) (350 ) Epicel Direct bill (hospital) 26,230 23,116 18,858 Other revenue — — 1,164 Total revenue $ 117,850 $ 90,857 $ 63,924 (a) Represents implants sold through Orsini and AllCare in both 2019 and 2018 and Dohmen Life Science Services, LLC (DLSS) and Vital Care, Inc (Vital Care) in 2017 in which such specialty pharmacies have entered into 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. Also represents sales with DMS and UsBio, based on direct contracts the Company holds with the facilities. The Company sold implants through DLSS and Vital Care through June 2017 and began selling directly to Orsini based on a fixed transfer price under a distribution model until June 2018. (b) Represents implants sold through Orsini, AllCare or DLSS in which such specialty pharmacy does not have a direct contract with the underlying payer. The amount of reimbursement is established based on a payer or state fee schedule and/or payer history. (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. (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. Concentration of Credit Risk From July 2016 through June 2017, the Company utilized a direct sales model and contracted with Dohmen Life Science Services, LLC (DLSS) to also provide administrative services associated with case management and reimbursement support and to provide billing and collection services for MACI. The Company also utilized Vital Care, Inc. (Vital Care) to provide similar billing and collection services for a subset of insurance payers and patients. In the second quarter of 2017, the Company and DLSS mutually terminated their agreement effective June 30, 2017. On May 15, 2017, the Company entered into a distribution agreement with Orsini Pharmaceutical Services, Inc. as a specialty pharmacy distributor of MACI and has engaged a third party services provider to provide the patient support program previously provided by DLSS and to manage patient cases for MACI. The Company’s receivables risk and credit risk became more concentrated from June 30, 2017 through June 15, 2018 due to the shift from DLSS to Orsini. Beginning June 16, 2018, the concentration of risk decreased because the Company retains the credit and collection risk from the end customer on implants after June 15, 2018. The Company sells Epicel directly to hospitals and not through a distributor. The Company’s total revenue and accounts receivable balances were comprised of the following concentrations from its largest customer of MACI and Epicel based on customers whose revenue or accounts receivable concentration is greater than 10% of total revenue or total accounts receivable in any of the periods disclosed below and are as follows: Revenue Concentration Accounts Receivable Concentration Year Ended December 31, December 31, 2019 2018 2017 2019 2018 MACI (a) 8 % 16 % 35 % 8 % 2 % Epicel 7 % 7 % 10 % 2 % 4 % (a) For MACI net revenue, the concentration of credit risk in 2018 and 2017 represents sales directly to Orsini. The comparable concentration in 2019 represents a different end customer under the sales model where the Company retains the credit and collection risk from the end customer.

Selected Balance Sheet Componen

Selected Balance Sheet Components	12 Months Ended
	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Components	Selected Balance Sheet Components Inventory Inventory as of December 31, 2019 and 2018 : (In thousands) 2019 2018 Raw materials $ 6,085 $ 2,872 Work-in-process 541 638 Finished goods 190 48 Inventory $ 6,816 $ 3,558 Property and Equipment Property and Equipment, net as of December 31, 2019 and 2018 : (In thousands) 2019 2018 Machinery and equipment $ 3,152 $ 1,536 Furniture, fixtures and office equipment 775 775 Computer equipment and software 6,174 3,712 Leasehold improvements 5,256 4,587 Construction in process 859 2,801 Financing right-of-use lease 148 — Total property and equipment, gross 16,364 13,411 Less accumulated depreciation (9,220 ) (7,505 ) $ 7,144 $ 5,906 Depreciation expense for the years ended December 31, 2019 , 2018 and 2017 were $1.7 million , $1.4 million and $1.6 million , respectively. Accrued Expenses Accrued Expenses as of December 31, 2019 and 2018 : (In thousands) 2019 2018 Bonus related compensation $ 5,116 $ 5,161 Employee related accruals 1,785 1,559 Other accrued expenses 1,047 210 Accrued expenses $ 7,948 $ 6,930

Debt

Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Debt	Debt On December 19, 2018, the Company prepaid in full all outstanding indebtedness under, and terminated, the Loan and Security Agreement dated as of September 9, 2016, by and between the Company, Silicon Valley Bank as Agent and Silicon Valley Bank, MidCap Financial Trust, MidCap Funding III Trust and other lenders listed therein as lenders (SVB Loan Agreement), as amended December 30, 2016, May 9, 2017 and December 6, 2017, which termination was effective December 19, 2018. Warrants were issued to SVB and MidCap in conjunction with the modified debt agreement as discussed in note 13. On the date of termination, the Company paid in full $17.1 million in outstanding borrowings at the time of termination. In connection with the termination of the SVB Loan Agreement, the Company paid an additional prepayment premium of 1.5% in the amount of $0.2 million and a final payment of 3.6% in the amount of $0.5 million . The prepayment of the debt in 2018 and the debt modification in 2017 were accounted for as debt extinguishments. The Company considered whether creditors remained the same or changed and whether the changes in debt terms were substantial. After performing the assessment in accordance with accounting guidance for the modification of debt arrangements, the term loan portion was determined to be accounted for as a debt extinguishment under the modified terms in 2017 and the repayment of both the term loans and revolving credit agreement in 2018 was also accounted for as a debt extinguishment. As a result, the unamortized deferred financing costs, prepayment penalty and the accelerated payment of the final payment was recognized as a loss on extinguishment of debt of $0.8 million for the year ended December 31, 2018 . The unamortized deferred financing costs, lender fees and warrant issuance costs allocated to the term loan under the modified terms were recognized as a loss on extinguishment of debt of $0.9 million for the year-ended December 31, 2017

Leases (Notes)

Leases (Notes)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	Leases The Company leases facilities in Ann Arbor, Michigan and Cambridge, Massachusetts. The Ann Arbor facility supports office space, and the Cambridge facility includes clean rooms, laboratories for MACI and Epicel manufacturing and office space. The Company also leases offsite warehouse space, vehicles and computer equipment. The Company adopted the new leasing standards using the modified retrospective transition approach, as of January 1, 2019, with no restatement of prior periods. As a result of adoption, no cumulative adjustment to retained earnings occurred. In addition, the Company elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed the Company to carry forward prior conclusions related to whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases and initial direct costs for existing leases. 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 projected payments adjusted for the index or rate in effect at the commencement date. The Company’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. Upon adoption all operating lease commitments with a lease term greater than 12 months that were previously assessed under previous lease guidance, were recognized as right to 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 and for the year ended December 31, 2019 , lease expense of less than $.1 million was recorded related to short-term leases. Adoption of ASU 2016-02 resulted in the recording of additional right-of-use assets and lease liabilities of approximately $25.6 million and $27.8 million, respectively, as of January 1, 2019. There was an immaterial impact on the Company’s consolidated net earnings and cash flows upon adoption. The contribution toward the cost of tenant improvements is recorded as a reduction of the operating lease assets and reclassed from deferred rent to lease operating assets. For the year ended December 31, 2019 , the Company recognized $5.4 million of operating lease expense and less than $0.1 million of financing lease expense. For the year ended December 31, 2018 (as reported under the prior leasing guidance) the Company recognized $5.2 million of operating lease expense and less than $0.1 million of financing lease expense, respectively. The Company’s leases contain non-lease components and activities that do not transfer a good or service to the Company. The Company elected not to combine lease and non-lease components and therefore non-lease costs were not included in the net lease assets or lease liabilities. Total leased assets and liabilities as reassessed under the updated guidance and classified on the balance sheet, as of December 31, 2019 are as follows: (In thousands) Classification December 31, 2019 Assets Operating Right-of-use assets $ 25,103 Finance Property and equipment, net 148 $ 25,251 Liabilities Current Operating Current portion of operating lease liabilities $ 5,461 Finance Other liabilities 41 $ 5,502 Non-current Operating Operating lease liabilities $ 22,242 Finance Other long-term liabilities 110 $ 22,352 Cash paid for amounts affecting the measurement of the Company’s operating lease liabilities was $5.0 million for the year ended December 31, 2019 . Maturity of lease liabilities as of December 31, 2019 are as follows: (In thousands) Operating Leases Finance Leases Total 2020 5,461 41 5,502 2021 5,358 41 5,399 2022 5,316 41 5,357 2023 5,294 41 5,335 2024 5,302 — 5,302 more than 5 years 11,270 — 11,270 Total lease payments $ 38,001 $ 164 $ 38,165 Less: Interest (10,298 ) (13 ) (10,311 ) Present value of lease liabilities $ 27,703 $ 151 $ 27,854 Total minimum future lease payments of approximately $2.1 million for a lease that has not commenced as of December 31, 2019 is not included in the consolidated financial statements, as the Company does not yet have control of the underlying asset. The lease is expected to commence in July 2020 with a lease term of 4.3 years . An explicit rate is not provided in some of the Company’s leases, therefore the Company uses a mix of incremental borrowing rate based on the information available at commencement date, as well as implicit and explicit rates in determining the present value of lease payments. The Company has options to renew lease terms for facilities and other assets. 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. For certain leases, the Company's exercise of the renewal option was determined to be probable and the renewal period was accordingly included in the lease term and related calculations. Lease terms and discount rates as of December 31, 2019 are as follows: December 31, 2019 Weighted average remaining lease term (years) Operating leases 6.8 Finance leases 3.5 Weighted average discount rate Operating leases 9.44 % Finance leases 5.00 % Future minimum payments related to operating and capital leases, as reflected under the prior guidance, for the fiscal year ended December 31, 2018 , are as follows with no changes from prior disclosure: (in thousands) Total 2019 2020 2021 2022 2023 More than 5 Years Operating leases $ 15,386 $ 4,879 $ 4,719 $ 4,754 $ 966 $ 68 $ — Capital leases 205 41 41 41 41 41 — Total $ 15,591 $ 4,920 $ 4,760 $ 4,795 $ 1,007 $ 109 $ — Rent expense, as reflected under the prior guidance, for the years ended December 31, 2018 and 2017 was $5.5 million and $5.6 million , respectively.
Leases	Leases The Company leases facilities in Ann Arbor, Michigan and Cambridge, Massachusetts. The Ann Arbor facility supports office space, and the Cambridge facility includes clean rooms, laboratories for MACI and Epicel manufacturing and office space. The Company also leases offsite warehouse space, vehicles and computer equipment. The Company adopted the new leasing standards using the modified retrospective transition approach, as of January 1, 2019, with no restatement of prior periods. As a result of adoption, no cumulative adjustment to retained earnings occurred. In addition, the Company elected the package of practical expedients permitted under the transition guidance within the new standard, which among other things, allowed the Company to carry forward prior conclusions related to whether any expired or existing contracts are or contain leases, the lease classification for any expired or existing leases and initial direct costs for existing leases. 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 projected payments adjusted for the index or rate in effect at the commencement date. The Company’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. Upon adoption all operating lease commitments with a lease term greater than 12 months that were previously assessed under previous lease guidance, were recognized as right to 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 and for the year ended December 31, 2019 , lease expense of less than $.1 million was recorded related to short-term leases. Adoption of ASU 2016-02 resulted in the recording of additional right-of-use assets and lease liabilities of approximately $25.6 million and $27.8 million, respectively, as of January 1, 2019. There was an immaterial impact on the Company’s consolidated net earnings and cash flows upon adoption. The contribution toward the cost of tenant improvements is recorded as a reduction of the operating lease assets and reclassed from deferred rent to lease operating assets. For the year ended December 31, 2019 , the Company recognized $5.4 million of operating lease expense and less than $0.1 million of financing lease expense. For the year ended December 31, 2018 (as reported under the prior leasing guidance) the Company recognized $5.2 million of operating lease expense and less than $0.1 million of financing lease expense, respectively. The Company’s leases contain non-lease components and activities that do not transfer a good or service to the Company. The Company elected not to combine lease and non-lease components and therefore non-lease costs were not included in the net lease assets or lease liabilities. Total leased assets and liabilities as reassessed under the updated guidance and classified on the balance sheet, as of December 31, 2019 are as follows: (In thousands) Classification December 31, 2019 Assets Operating Right-of-use assets $ 25,103 Finance Property and equipment, net 148 $ 25,251 Liabilities Current Operating Current portion of operating lease liabilities $ 5,461 Finance Other liabilities 41 $ 5,502 Non-current Operating Operating lease liabilities $ 22,242 Finance Other long-term liabilities 110 $ 22,352 Cash paid for amounts affecting the measurement of the Company’s operating lease liabilities was $5.0 million for the year ended December 31, 2019 . Maturity of lease liabilities as of December 31, 2019 are as follows: (In thousands) Operating Leases Finance Leases Total 2020 5,461 41 5,502 2021 5,358 41 5,399 2022 5,316 41 5,357 2023 5,294 41 5,335 2024 5,302 — 5,302 more than 5 years 11,270 — 11,270 Total lease payments $ 38,001 $ 164 $ 38,165 Less: Interest (10,298 ) (13 ) (10,311 ) Present value of lease liabilities $ 27,703 $ 151 $ 27,854 Total minimum future lease payments of approximately $2.1 million for a lease that has not commenced as of December 31, 2019 is not included in the consolidated financial statements, as the Company does not yet have control of the underlying asset. The lease is expected to commence in July 2020 with a lease term of 4.3 years . An explicit rate is not provided in some of the Company’s leases, therefore the Company uses a mix of incremental borrowing rate based on the information available at commencement date, as well as implicit and explicit rates in determining the present value of lease payments. The Company has options to renew lease terms for facilities and other assets. 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. For certain leases, the Company's exercise of the renewal option was determined to be probable and the renewal period was accordingly included in the lease term and related calculations. Lease terms and discount rates as of December 31, 2019 are as follows: December 31, 2019 Weighted average remaining lease term (years) Operating leases 6.8 Finance leases 3.5 Weighted average discount rate Operating leases 9.44 % Finance leases 5.00 % Future minimum payments related to operating and capital leases, as reflected under the prior guidance, for the fiscal year ended December 31, 2018 , are as follows with no changes from prior disclosure: (in thousands) Total 2019 2020 2021 2022 2023 More than 5 Years Operating leases $ 15,386 $ 4,879 $ 4,719 $ 4,754 $ 966 $ 68 $ — Capital leases 205 41 41 41 41 41 — Total $ 15,591 $ 4,920 $ 4,760 $ 4,795 $ 1,007 $ 109 $ — Rent expense, as reflected under the prior guidance, for the years ended December 31, 2018 and 2017 was $5.5 million and $5.6 million , respectively.

Cash Equivalents and Investment

Cash Equivalents and Investments	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Cash Equivalents and Investments	Cash Equivalents and Investments During the years ended December 31, 2019 and 2018, the Company purchased marketable debt securities, which are classified as available-for-sale 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 as of December 31, 2019 and December 31, 2018 : December 31, 2019 Gross Unrealized Amortized Cost Gains Losses Estimated Fair Value Money market funds $ 5,381 $ — $ — $ 5,381 Commercial paper 11,892 — — 11,892 Corporate notes 18,369 11 — 18,380 U.S. government securities 11,291 4 — 11,295 U.S. asset-backed securities 10,503 6 — 10,509 $ 57,436 $ 21 $ — $ 57,457 Classified as: Cash equivalents $ 5,381 Short term investments 42,829 Long term investments 9,247 $ 57,457 December 31, 2018 Gross Unrealized (In thousands) Amortized Cost Gains Losses Fair Value Money market funds $ 5,838 $ — $ — $ 5,838 Repurchase agreements 5,000 — — 5,000 Commercial paper 30,710 — — 30,710 Corporate notes 13,168 — (24 ) 13,144 U.S. government securities 10,167 — (1 ) 10,166 U.S. asset-backed securities 10,632 — (14 ) 10,618 $ 75,515 $ — $ (39 ) $ 75,476 Classified as: Cash equivalents $ 10,838 Short-term investments 64,638 $ 75,476 As of the year ended December 31, 2018 , the Company invested $5.0 million in overnight repurchase agreement securities classified as cash equivalents on the balance sheet. There were no marketable securities that the Company considers to be other-than-temporarily impaired as of December 31, 2019 . The Company's investment strategy is to buy short-duration marketable securities with a high credit rating. As of December 31, 2019 , all marketable securities held by the Company had remaining contractual maturities of three years or less. If any adjustment to fair value reflects a decline in the value of the investment, the Company considers all available evidence to evaluate the extent to which the decline is “other than temporary,” including the Company’s intention to sell and, if so, mark the investment to market through a charge to our consolidated statement of operations. There have been no impairments of the Company’s assets measured and carried at fair value for the year ended December 31, 2019 .

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	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 nonqualified 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 and restricted stock units granted to employees and non-employees under these plans expire no later than ten years from the date of grant and generally become exercisable over a four 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 2019 Omnibus Incentive Plan (2019 Plan) was approved on May 1, 2019 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 2019 Plan shall not be less than the fair market value of the Company’s common stock on the date of grant. The 2019 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 and the 2017 Omnibus Incentive Plan (Prior Plans), and no new grants have been granted under the Prior Plans after approval. However, the expiration or forfeiture of options previously granted under the Prior Plans will increase the number of shares available for issuance under the 2019 Plan. As of December 31, 2019 , there were 3,344,242 shares available for future grant under the 2019 Plan. Employee Stock Purchase Plan Employees are able to purchase stock under the Vericel Corporation Employee Stock Purchase Plan (ESPP). The ESPP allows for the issuance of an aggregate of 1,000,000 shares of common stock of which 595,799 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. In January 2020, employees purchased 19,076 shares resulting in proceeds from the sale of common stock of $0.2 million under the ESPP for the fourth quarter of 2019. The total share-based compensation expense for the ESPP for the years ended December 31, 2019 , 2018 , and 2017 was approximately $0.3 million , $0.3 million , and $0.2 million , respectively. Service-Based Stock Options During the year ended December 31, 2019 , the Company granted 2,033,760 service-based options to purchase common stock. The exercise price of the options is the fair market value per share of common stock on the grant date, generally vest over four years (other than 78,750 non-employee director options which vest over one year ) and have a term of ten years . The Company issues new shares upon the exercise of stock options. The weighted average grant-date fair value of service-based options granted during the years ended December 31, 2019 , 2018 , and 2017 was $12.62 , $6.96 and $1.99 , respectively. The net compensation costs recorded for the service-based stock options related to employees and directors (including the impact of forfeitures) for the years ended December 31, 2019 , 2018 , and 2017 were $11.8 million , $6.9 million and $2.5 million , respectively. 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 weighted average assumptions noted in the following table. Year Ended December 31, Service-Based Stock Options 2019 2018 2017 Expected dividend rate —% —% —% Expected stock price volatility 77.9-85.5% 82.3 – 88.3% 79.7 – 88.2% Risk-free interest rate 1.4-2.7% 2.4 – 3.1% 1.39 – 2.3% Expected life (years) 5.3 - 6.3 5.3 - 6.3 5.5 - 6.3 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, 2018 4,790,683 $ 5.85 7.7 $ 11,407 Granted 2,033,760 $ 17.51 Exercised (1,197,016 ) $ 3.64 Expired (36,561 ) $ 26.16 Forfeited (537,916 ) $ 11.26 Outstanding at December 31, 2019 5,052,950 $ 10.35 7.7 $ 37,974 Exercisable at December 31, 2019 2,385,824 $ 7.49 6.5 $ 25,113 As of December 31, 2019, 4,700,318 shares are vested and expected to vest. As of December 31, 2019 , there was approximately $16.6 million , of total unrecognized compensation cost related to non-vested service-based stock options granted under the 2019 Plan and the Prior Plans. That cost is expected to be recognized over a weighted-average period of 3.2 years. The total intrinsic value of stock options vested for the years ended December 31, 2019 , 2018 , and 2017 was $12.4 million , $10.3 million and $0.7 million , respectively. Restricted Stock Units The restricted stock units vest annually over four years in equal installments commencing on the first anniversary of the grant date (other than non-employee director options which vest over one year from the grant date). The Company issues new shares upon the vesting of restricted stock units. Restricted stock awards are recorded at fair value at the date of grant, which is based on the closing share price on the grant date. Compensation expense is recorded for restricted stock units that are expected to vest based on their fair value at grant date and is amortized over the expected vesting period. The following table summarizes the activity for restricted stock awards for the indicated periods: Restricted Stock Units Number of Restricted Stock Awards Weighted Average Grant Date Fair Value Weighted Average Term Aggregate Intrinsic Value Outstanding at December 31, 2018 — Granted 186,922 $ 17.71 $ 3,310 Vested — Forfeited (29,892 ) $ 17.24 Unvested at December 31, 2019 157,030 $ 17.80 1.6 $ 2,732 The total grant-date fair value of restricted stock units granted in the year ended December 31, 2019 was $3.3 million. No restricted stock units were granted in 2018. The net compensation costs recorded for the service-based restricted stock units related to employees and directors (including the impact of forfeitures) for the year ended December 31, 2019 was $1.0 million. At December 31, 2019 , the total unrecognized compensation cost related to the restricted stock awards was $1.8 million and the weighted average period over which that cost is expected to be recognized was 3.1 years . Stock Compensation Expense Non-cash stock-based compensation expense (employee stock purchase plan, service-based stock options and restricted stock units) included in cost of goods sold, research and development expenses and selling, general and administrative expenses is summarized in the following table: Years Ended December 31, (in thousands) 2019 2018 2017 Cost of goods sold $ 2,029 $ 1,015 $ 428 Research and development 2,428 1,672 506 General, selling and administrative 8,722 4,536 1,746 Total non-cash stock-based compensation expense $ 13,179 $ 7,223 $ 2,680

Shareholders' Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2019
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Shareholders’ Equity Public Equity Offering In June 2018, the Company sold 5,750,000 shares of its common stock in an underwritten public offering at a price of $13.00 per share. The Company received proceeds of $70.1 million , net of $4.7 million of underwriters’ discount and issuance costs consisting primarily of legal and accounting fees. The Company recorded these proceeds as a common stock issuance. Dividends No cash dividends have been declared or paid by the Company since its inception.

Net Loss Per Common Share

Net Loss Per Common Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Common Share	Net Loss Per Common Share The following reflects the net loss attributable to common shareholders and share data used in the basic and diluted earnings per share computations using the two class method: Year Ended December 31, (Amounts in thousands, except per share amounts) 2019 2018 2017 Numerator: Net loss $ (9,665 ) $ (8,137 ) $ (17,286 ) Denominator: Denominator for basic and diluted EPS: weighted-average common shares outstanding 44,180 40,242 33,355 Net loss per share attributable to common shareholders (basic and diluted) $ (0.22 ) $ (0.20 ) $ (0.52 ) Anti-dilutive shares excluded from the calculation of diluted earnings per share (a) (amounts in millions): Stock options 5.1 4.8 4.6 Restricted stock unit awards 0.2 — — Warrants — — 0.9 (a) Common equivalent shares are not included in the diluted per share calculation where the effect of their inclusion would be anti-dilutive.

Stock Purchase Warrants

Stock Purchase Warrants	12 Months Ended
	Dec. 31, 2019
Warrants and Rights Note Disclosure [Abstract]
Stock Purchase Warrants	Stock Purchase Warrants The Company has historically issued warrants to purchase shares of the Company’s common stock in connection with certain of its common stock offerings. The fair value of the warrants described in the table above is measured using the Black-Scholes valuation model. Inherent in the Black-Scholes valuation model are assumptions related to expected stock-price volatility, expected life, risk-free interest rate and dividend yield. The Company estimates the volatility of its common stock based on historical volatility that matches the expected remaining life of the warrants. The risk-free interest rate is based on the U.S. Treasury zero-coupon yield curve on the grant date for a maturity similar to the expected remaining life of the warrants. The expected life of the warrants is assumed to be equivalent to their remaining contractual term. The dividend rate is based on the historical rate, which the Company anticipates will remain at zero . During the year ended December 31, 2019 , the Company issued 19,808 shares of common stock upon the exercise warrants with an exercise price of 4.27 . There are no warrants outstanding as of December 31, 2019 . ICT Warrants On December 21, 2017, the Company received $5.2 million (gross of withholding tax) from Innovative Cellular Therapeutics CO., LTD. (ICT), of which $4.0 million was allocated to the purchase of a warrant for 818,424 shares of the Company's common stock based on the fair value on the date of grant and the remaining $1.2 million was allocated as consideration for the license agreement described in note 4. The fair value of the warrant was based on the closing price as of December 6, 2017 of $4.90 at an exercise price of $0.01 per share. On December 27, 2017, ICT exercised the warrant via a cashless exercise in exchange for 816,850 shares of the Company’s common stock. There were no

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	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). There was no movement between Level 1 and Level 2 or between Level 2 and Level 3. 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, government securities and asset-backed securities 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. The following table summarizes the valuation of the Company’s financial instruments that are measured at fair value on a recurring basis: December 31, 2019 December 31, 2018 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 $ 5,381 $ 5,381 $ — $ — $ 5,838 $ 5,838 $ — $ — Repurchase agreements — — — — 5,000 — 5,000 — Commercial paper 11,892 — 11,892 — 30,710 — 30,710 — Corporate notes 18,380 — 18,380 — 13,144 — 13,144 — U.S. government securities 11,295 — 11,295 — 10,166 — 10,166 — U.S. asset-backed securities 10,509 — 10,509 — 10,618 — 10,618 — $ 57,457 $ 5,381 $ 52,076 $ — $ 75,476 $ 5,838 $ 69,638 $ —

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Loss before income taxes for U.S and non-U.S operations was as follows: Year Ended December 31, 2019 2018 2017 U.S. loss $ (9,632 ) $ (8,056 ) $ (17,066 ) Non U.S. loss (33 ) (81 ) (220 ) $ (9,665 ) $ (8,137 ) $ (17,286 ) A reconciliation of income taxes computed using the federal statutory rate to the taxes reported in the consolidated statements of operations is as follows: Year Ended December 31, (In thousands) 2019 2018 2017 Loss before income taxes $ (9,665 ) $ (8,137 ) $ (17,286 ) Federal statutory rate 21 % 21 % 34 % Taxes computed at federal statutory rate (2,030 ) (1,709 ) (5,877 ) State taxes (484 ) (385 ) (1,106 ) Stock compensation (1,329 ) (605 ) 563 Federal and State Rate Change (164 ) 839 11,749 Other (49 ) 172 116 Change in valuation allowance 4,056 1,688 (5,445 ) Reported income taxes $ — $ — $ — Deferred tax assets (liabilities) consist of the following: Year Ended December 31, (In thousands) 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 10,542 $ 10,969 Employee benefits and stock compensation 4,329 2,798 Research and development costs 7,851 9,067 Fixed assets — 418 Intangible assets 4,350 — Operating lease liability 102 — Inventory reserve 3,303 2,339 Other, net 119 345 Total deferred tax assets 30,596 25,936 Less: valuation allowance (29,991 ) (25,936 ) Total net deferred tax assets 605 — Deferred tax liabilities: Fixed assets (605 ) — Total net deferred tax liabilities (605 ) — Net deferred tax assets and liabilities $ — $ — As of December 31, 2019, the Company’s U.S. federal and state tax net operating loss carryforwards available to offset future profits, after considering the annual Section 382 limit described below, are $42.2 million and $24.5 million , respectively. These net operating loss carryforwards will expire between 2020 and 2039 with the exception of the federal net operating loss generated in 2018. The federal net operating loss of $ 1.5 million generated in 2018 can be carried forward indefinitely. The projected annual limitation on the use of the net operating losses that existed prior to September 17, 2014 as a result of our 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. In accordance with the accounting guidance for income taxes, the Company estimated 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 the Company achieves profitability, these deferred tax assets may be available to offset future income taxes. The change in the valuation allowance was an increase of $4.1 million and $1.7 million for the years ended December 31, 2019 and 2018, 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 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 has derecognized such positions. To the extent the uncertain tax positions meet the “more likely than not” threshold, the Company has measured and recorded the highest probable benefit, and have established 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 the 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. Due to the Company’s net operating loss carryforwards, federal income tax returns from incorporation are still subject to examination. Michigan tax returns for the year ended December 31, 2013 and forward are subject to examination. Massachusetts tax returns for the year ended December 31, 2015 and forward are subject to examination. On December 22, 2017 the Tax Cuts and Jobs Act (Tax Act) was enacted. The Tax Act contains significant changes to corporate taxation, including the reduction of the corporate tax rate from 35 percent to 21 percent, increased deductions for capital spending, limitations on interest expense deductions, implementation of a territorial tax system, and imposition of a tax on deemed repatriated earnings of foreign subsidiaries. The Company remeasured the deferred taxes based on the enacted rate of 21 percent which resulted in an increase to tax expense of $11.7 million , which was recorded in 2017. The increase to tax expense was offset by the reversal of the valuation allowance. Our final determination of the Tax Act impact and the remeasurement of our deferred assets and liabilities was completed prior to the deadline of one year from enactment of the Tax Act. For the year ended December 31, 2018, there were no material changes to our analysis originally performed as of December 31, 2017.

Employee Savings Plan

Employee Savings Plan	12 Months Ended
	Dec. 31, 2019
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 $0.7 million , $0.6 million and $0.6 million for the years ended December 31, 2019 , 2018 and 2017 , respectively.

Nexobrid License and Supply Agr

Nexobrid License and Supply Agreements	12 Months Ended
	Dec. 31, 2019
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 Ltd. (MediWound) to commercialize NexoBrid ® and any improvements to Nexobrid in all countries of North America. NexoBrid is a topically-administered biological product that enzymatically removes nonviable burn tissue, or eschar, in patients with deep partial and full-thickness thermal burns. NexoBrid is currently in clinical development in North America, and pursuant to the terms of the license agreement, MediWound will continue to conduct all clinical activities described in the development plan to support the BLA filing with the United States Food and Drug Administration under the supervision of a Central Steering Committee comprised of members of each party. In May 2019, the Company paid MediWound $17.5 million in consideration of the license. The $17.5 million upfront payment was recorded to research and development expense in the year ended December 31, 2019 as the license is considered in process research and development. The Company is also obligated to pay MediWound $7.5 million upon U.S. regulatory approval of the BLA for NexoBrid and up to $125 million contingent upon meeting certain sales milestones. The first sales milestone of $7.5 million would be triggered when annual net sales of NexoBrid or improvements to it in North America exceed $75 million . 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. The U.S. Biomedical Advanced Research and Development Authority (BARDA) has committed to procure NexoBrid, and the Company will pay a percentage of gross profits to MediWound on initial committed amounts and a royalty on any additional BARDA purchases of NexoBrid beyond the initial committed amount. The Company also entered into a supply agreement with MediWound under which MediWound will manufacture NexoBrid for the Company on a unit price basis which may be increased based on a published index. 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. After the exclusivity period or upon supply failure, the Company will be permitted to establish an alternate source of supply. As of December 31, 2019, the milestone payments are not yet probable and therefore, not considered a commitment.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Manufacturing and Supply Agreements Matricel — In October 2015, the Company signed a long-term supply agreement with Matricel GmbH for the ACI-Maix collagen membrane used in the manufacture of MACI. Matricel supplied ACI-Maix membranes used in the production of MACI when it was previously marketed outside the U.S. by Genzyme Corporation, a Sanofi company. The Company and Matricel amended the agreement on March 17, 2018. Under the agreement, the Company has committed to purchase annually approximately $0.6 million per year, the Company has fulfilled this commitment for the years ended December 31, 2019 , 2018 and 2017 , respectively. The agreement is effective until December 31, 2022 and contains a 5 -year renewal option by the Company and an additional 5 -year automatic renewal, unless otherwise terminated. 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 materials used in the Company's cell manufacturing process to manufacture its marketed cell therapy products. Future minimum purchase commitments related to our contractual obligations are as follows: Payments Due by Period (in thousands) Total 2020 2021 2022 2023 2024 More than 5 Years Purchase commitments $ 1,821 $ 607 $ 607 $ 607 $ — $ — $ —

Supplementary Quarterly Financi

Supplementary Quarterly Financial Information (unaudited)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Supplementary Quarterly Financial Information (unaudited)	Supplementary Quarterly Financial Information (unaudited) Quarterly earnings per share amounts may not sum to the totals for each of the years, since quarterly computations are based on weighted average common shares outstanding during each quarter. In thousands, except per share data First Quarter Second Quarter Third Quarter Fourth Quarter Year 2019 Revenues $ 21,810 $ 26,151 $ 30,499 $ 39,390 $ 117,850 Gross profit 13,170 17,129 21,175 28,805 80,279 Income (loss) from operations (3,358 ) (20,200 ) 3,097 9,210 (11,251 ) Net (loss) income (2,844 ) (19,792 ) 3,470 9,501 (9,665 ) Net (loss) income per share (Basic) (0.07 ) (0.45 ) 0.08 0.21 (0.22 ) Net (loss) income per share (Diluted) (0.07 ) (0.45 ) 0.07 0.20 (0.22 ) 2018 Revenues $ 18,027 $ 19,011 $ 22,484 $ 31,335 $ 90,857 Gross profit 10,361 11,284 14,346 22,706 58,697 Income (loss) from operations (4,322 ) (4,246 ) (1,336 ) 5,995 (3,909 ) Net (loss) income (7,659 ) (4,651 ) (1,069 ) 5,242 (8,137 ) Net (loss) income per share (Basic) (0.21 ) (0.12 ) (0.02 ) 0.12 (0.20 ) Net (loss) income per share (Diluted) (0.21 ) (0.12 ) (0.02 ) 0.11 (0.20 )

Summary of Significant Accoun_2

Summary of Significant Accounting Policies - (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of Vericel and its wholly-owned subsidiaries, Vericel Denmark ApS, in Kastrup, Demark and Vericel Security Corporation (collectively, the Company). All inter-company transactions and accounts have been eliminated in consolidation. Vericel Denmark ApS ceased operations in 2015.
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reported period. Actual results could 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, overnight repurchase agreements and short duration agency bonds and commercial paper.
Restricted cash	Restricted cash Amounts included in restricted cash represent those required to be set aside to meet contractual terms of a lease agreement held by the Company.
Investments	Investments Short-term investments consist of debt securities classified as available-for-sale and have maturities greater than 90 days, but less than one year as of the balance sheet date. Long-term investments consist of debt securities classified as available-for-sale and have maturities greater than one year as of the balance sheet date. All investments are carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • 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). Unrealized gains and losses on available-for-sale securities are excluded from earnings and are reported as a component of accumulated other comprehensive loss. The cost of available-for-sale securities sold is based on the specific-identification method. Realized gains and losses are included in earnings, and are derived for specific-identification method for determining the costs of investments sold. If a decline in the fair value is considered other-than-temporary, based on available evidence, the unrealized loss is reclassified from accumulated other comprehensive income (loss) to the statements of operations. Realized gains and losses are determined on the specific identification method and are included in investment and other income, net.
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 write-down obsolete or other unmarketable inventory to its estimated net realizable value. If the actual net realizable value is less than that estimated by us, 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 sales.
Leases	Leases The Company adopted the new leasing standards using the modified retrospective transition approach, as of January 1, 2019, with no restatement of prior periods. Upon adoption all operating lease commitments with a lease term greater than 12 months that were previously assessed under the prior lease guidance, were recognized as right to 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. Adoption of ASU 2016-02 resulted in the recording of additional right-of-use assets and lease liabilities of approximately $25.6 million and $27.8 million, respectively, as of January 1, 2019. Certain lease agreements include rental payments that are adjusted periodically for inflation or other variables. The leases are initially measured using 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 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. Some leases contain clauses for renewal at the Company’s option with renewal terms that generally extend the lease term from 1 to 5 years . Certain lease agreements contain options to purchase the leased property and options to terminate the lease. Payments to be made in option periods are recognized as part of the right-of-use lease assets and lease liabilities when it is reasonably certain that the option to extend the lease will be exercised or the option to terminate the lease will not be exercised, or is not at the Company’s option. The Company determines whether the reasonably certain threshold is met by considering contract-, asset-, market-, and entity-based factors. A portfolio approach is applied to certain lease contracts with similar characteristics. The Company’s lease agreements do not contain any significant residual value guarantees or material restrictive covenants imposed by the leases.
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.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are initially measured and recognized at acquisition cost, including any directly attributable cost of preparing the asset for its intended use or, in the case of assets acquired in a business combination, at fair value as at the date of the combination. After initial measurement, property, plant and equipment are carried at cost less accumulated depreciation and impairment. Repair and maintenance costs of property, plant and equipment are expensed as incurred. The depreciable value of property, plant and equipment, net of any residual value, 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, plant and equipment are as follows: • Equipment and computers: 3 to 5 years • Furniture and fixtures: 5 years • Building improvements and leasehold improvements: Shorter of the remaining life of the lease or 10 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.
Revenue Recognition and Net Product Sales	Revenue Recognition and Net Product Sales The new revenue standard became effective for the Company on January 1, 2018, and was adopted using the modified retrospective method. Based on the Company’s evaluation of all of its product revenue contracts under the new revenue standard there was no cumulative adjustment recorded in the financial statements upon adoption of Accounting Standards Codification 606, Revenue Recognition, (ASC 606) on January 1, 2018. For the year ended December 31, 2018 , the timing and amount of revenue recognized under ASC 606 was not materially different from that under the previous guidance. The Company recognizes product revenue from sales to a customer (distributor or hospital) following the five step model in 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, kits, or Epicel as of December 31, 2019 ; 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. Currently, for MACI, MACI kits and Epicel there are no variable pricing arrangements related to warranties or rebates offered to customers. The majority of orders are due within 60 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 activities represent a significant part of the Company’s business. 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. Research and development expenses are expensed as incurred.
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 Company uses the value of its common stock at the date of the grant in the calculation of the fair value of its share-based awards. The fair value of restricted stock units held by the employees is determined based on the fair value of the Company's common stock on the date of the grant. The fair value of stock options held by the employees is determined using a Black-Scholes option valuation method, which is a valuation technique that is acceptable for share-based payment accounting. 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 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 recognize 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. For certain non-employee consultants, stock option awards continue to vest post-termination. 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 purchase options at the grant date, which corresponds to the first day of each purchase period, and is amortized over the purchase period.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is the change in stockholders’ equity during a period arising from any gain or loss unrealized 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, that a portion or all of the deferred tax assets will not be realized. 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 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 Earnings (Loss) Per Share Attributable to Common Shareholders	Net Earnings (Loss) Per Share Attributable to Common Shareholders Basic and diluted earnings (loss) per share is calculated using the two-class method. Basic earnings (loss) per share which is based on an earnings allocation formula that determines earnings (loss) per share for the holders of the Company’s common shares. There were no undeclared dividends for the year ended December 31, 2019 or 2018 . Diluted earnings (loss) per share includes
Financial Instruments	Financial Instruments
Warrants	Warrants
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting for Leases The Financial Accounting Standards Board (FASB) issued guidance to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. In accordance with the updated guidance, lessees are required to recognize the assets and liabilities arising from operating leases on the balance sheet. The guidance is effective for annual reporting periods beginning after December 15, 2018. The Accounting Standard Update 2016-02, Leases (Topic 842) , became effective for the Company on January 1, 2019 and was adopted using the modified retrospective method. See note 7 for further discussion. Measuring Credit Losses on Financial Instruments The FASB issued updated guidance on measuring credit losses on financial instruments. The guidance removes the thresholds that companies apply to measure credit losses on financial instruments measured at amortized cost, such as loans, receivables, and held-to-maturity debt securities. Prior to the updated guidance, credit losses are recognized when it is probable that the loss has been incurred. The revised guidance removes all recognition thresholds and requires companies to recognize an allowance for credit losses for the difference between the amortized cost basis of a financial instrument and the amount of amortized cost that a company expected to collect over the instrument’s contractual life. This guidance will be issued through Accounting Standard Update 2016-13, Financial Instruments-Credit Losses (Topic 326), which will be effective for the Company January 1, 2020. The Company is currently in the process of evaluating the impact to its consolidated financial statements. Fair Value Measurement Disclosure The FASB issued updated guidance through ASU 2018-13, Fair Value Measurement (Topic 820) Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement. The revised guidance is intended to develop a more consistent disclosure framework that will increase clarity, remove, modify and add certain fair value disclosures to improve the effectiveness of the Company’s disclosures in the notes of the financial statements. This guidance will be effective for the Company January 1, 2020. The Company is currently in the process of evaluating the impact to its consolidated financial statements. Simplifying the Accounting for Income Taxes In December 2019, the FASB issued ASU 2019-12, Simplifying the Accounting for Income Taxes (ASC 740). The ASU enhances and simplifies various aspects of the income tax accounting guidance in ASC 740, including requirements related to hybrid tax regimes, the tax basis step-up in goodwill obtained in a transaction that is not a business combination, separate financial statements of entities not subject to tax, the intra-period tax allocation exception to the incremental approach, ownership changes in investments, changes from a subsidiary to an equity method investment, interim-period accounting for enacted changes in tax law, and the year-to-date loss limitation in interim-period tax accounting. This guidance is effective for the Company for annual and interim periods beginning after December 31, 2020; however, early adoption is permitted. The Company is currently in the process of evaluating the impact to its consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Supplementary cash flows information	The following table presents certain supplementary cash flows information for the years ended December 31, 2019 , 2018 and 2017 : Year Ended December 31, (In thousands) 2019 2018 2017 Supplementary Cash Flows information: Non-cash information: Warrants exercised for common stock $ 104 $ 3,538 $ — Right-of-use asset and lease liability recognized 2,599 — — Additions to equipment in process included in accounts payable 217 606 341 Shares exchanged between common and preferred stock — — (38,389 ) Cash information: Interest paid (net of interest capitalized) $ — $ 2,230 $ 931 Income tax withholding paid — — 100

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2019
Risks and Uncertainties [Abstract]
Disaggregation of Revenue	The following table and description below shows the products from which the Company generated its revenue: Year Ended December 31, Revenue by product (in thousands) 2019 2018 2017 MACI and Carticel implants and kits Implants based on contracted rate sold through a specialty pharmacy (a) $ 56,185 $ 42,926 $ 37,796 Implants subject to third party reimbursement sold through a specialty pharmacy (b) 17,076 8,621 1,299 Implants sold direct based on contracted rates (c) 13,933 12,122 3,393 Implants sold direct subject to third party reimbursement (d) 1,529 2,257 — Biopsy kits - direct bill 2,243 1,997 1,764 Change in estimates related to prior periods 654 (182 ) (350 ) Epicel Direct bill (hospital) 26,230 23,116 18,858 Other revenue — — 1,164 Total revenue $ 117,850 $ 90,857 $ 63,924 (a) Represents implants sold through Orsini and AllCare in both 2019 and 2018 and Dohmen Life Science Services, LLC (DLSS) and Vital Care, Inc (Vital Care) in 2017 in which such specialty pharmacies have entered into 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. Also represents sales with DMS and UsBio, based on direct contracts the Company holds with the facilities. The Company sold implants through DLSS and Vital Care through June 2017 and began selling directly to Orsini based on a fixed transfer price under a distribution model until June 2018. (b) Represents implants sold through Orsini, AllCare or DLSS in which such specialty pharmacy does not have a direct contract with the underlying payer. The amount of reimbursement is established based on a payer or state fee schedule and/or payer history. (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. (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.
Schedules of concentration of risk	The Company’s total revenue and accounts receivable balances were comprised of the following concentrations from its largest customer of MACI and Epicel based on customers whose revenue or accounts receivable concentration is greater than 10% of total revenue or total accounts receivable in any of the periods disclosed below and are as follows: Revenue Concentration Accounts Receivable Concentration Year Ended December 31, December 31, 2019 2018 2017 2019 2018 MACI (a) 8 % 16 % 35 % 8 % 2 % Epicel 7 % 7 % 10 % 2 % 4 % (a) For MACI net revenue, the concentration of credit risk in 2018 and 2017 represents sales directly to Orsini. The comparable concentration in 2019 represents a different end customer under the sales model where the Company retains the credit and collection risk from the end customer.

Selected Balance Sheet Compon_2

Selected Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Schedule of inventory	Inventory as of December 31, 2019 and 2018 : (In thousands) 2019 2018 Raw materials $ 6,085 $ 2,872 Work-in-process 541 638 Finished goods 190 48 Inventory $ 6,816 $ 3,558
Schedule of property and equipment, net	Property and Equipment, net as of December 31, 2019 and 2018 : (In thousands) 2019 2018 Machinery and equipment $ 3,152 $ 1,536 Furniture, fixtures and office equipment 775 775 Computer equipment and software 6,174 3,712 Leasehold improvements 5,256 4,587 Construction in process 859 2,801 Financing right-of-use lease 148 — Total property and equipment, gross 16,364 13,411 Less accumulated depreciation (9,220 ) (7,505 ) $ 7,144 $ 5,906
Schedule of accrued expenses	Accrued Expenses as of December 31, 2019 and 2018 : (In thousands) 2019 2018 Bonus related compensation $ 5,116 $ 5,161 Employee related accruals 1,785 1,559 Other accrued expenses 1,047 210 Accrued expenses $ 7,948 $ 6,930

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Assets And Liabilities	Total leased assets and liabilities as reassessed under the updated guidance and classified on the balance sheet, as of December 31, 2019 are as follows: (In thousands) Classification December 31, 2019 Assets Operating Right-of-use assets $ 25,103 Finance Property and equipment, net 148 $ 25,251 Liabilities Current Operating Current portion of operating lease liabilities $ 5,461 Finance Other liabilities 41 $ 5,502 Non-current Operating Operating lease liabilities $ 22,242 Finance Other long-term liabilities 110 $ 22,352
Maturity of lease liabilities	Maturity of lease liabilities as of December 31, 2019 are as follows: (In thousands) Operating Leases Finance Leases Total 2020 5,461 41 5,502 2021 5,358 41 5,399 2022 5,316 41 5,357 2023 5,294 41 5,335 2024 5,302 — 5,302 more than 5 years 11,270 — 11,270 Total lease payments $ 38,001 $ 164 $ 38,165 Less: Interest (10,298 ) (13 ) (10,311 ) Present value of lease liabilities $ 27,703 $ 151 $ 27,854
Maturity of lease liabilities	Maturity of lease liabilities as of December 31, 2019 are as follows: (In thousands) Operating Leases Finance Leases Total 2020 5,461 41 5,502 2021 5,358 41 5,399 2022 5,316 41 5,357 2023 5,294 41 5,335 2024 5,302 — 5,302 more than 5 years 11,270 — 11,270 Total lease payments $ 38,001 $ 164 $ 38,165 Less: Interest (10,298 ) (13 ) (10,311 ) Present value of lease liabilities $ 27,703 $ 151 $ 27,854
Lease term and discount rate	Lease terms and discount rates as of December 31, 2019 are as follows: December 31, 2019 Weighted average remaining lease term (years) Operating leases 6.8 Finance leases 3.5 Weighted average discount rate Operating leases 9.44 % Finance leases 5.00 %
Schedule Of Future Minimum Rental Payments For Operating And Capital Leases Table Text Block	Future minimum payments related to operating and capital leases, as reflected under the prior guidance, for the fiscal year ended December 31, 2018 , are as follows with no changes from prior disclosure: (in thousands) Total 2019 2020 2021 2022 2023 More than 5 Years Operating leases $ 15,386 $ 4,879 $ 4,719 $ 4,754 $ 966 $ 68 $ — Capital leases 205 41 41 41 41 41 — Total $ 15,591 $ 4,920 $ 4,760 $ 4,795 $ 1,007 $ 109 $ — Payments Due by Period (in thousands) Total 2020 2021 2022 2023 2024 More than 5 Years Purchase commitments $ 1,821 $ 607 $ 607 $ 607 $ — $ — $ —

Cash Equivalents and Investme_2

Cash Equivalents and Investments (Tables)	12 Months Ended
	Dec. 31, 2019
Cash and Cash Equivalents [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 as of December 31, 2019 and December 31, 2018 : December 31, 2019 Gross Unrealized Amortized Cost Gains Losses Estimated Fair Value Money market funds $ 5,381 $ — $ — $ 5,381 Commercial paper 11,892 — — 11,892 Corporate notes 18,369 11 — 18,380 U.S. government securities 11,291 4 — 11,295 U.S. asset-backed securities 10,503 6 — 10,509 $ 57,436 $ 21 $ — $ 57,457 Classified as: Cash equivalents $ 5,381 Short term investments 42,829 Long term investments 9,247 $ 57,457 December 31, 2018 Gross Unrealized (In thousands) Amortized Cost Gains Losses Fair Value Money market funds $ 5,838 $ — $ — $ 5,838 Repurchase agreements 5,000 — — 5,000 Commercial paper 30,710 — — 30,710 Corporate notes 13,168 — (24 ) 13,144 U.S. government securities 10,167 — (1 ) 10,166 U.S. asset-backed securities 10,632 — (14 ) 10,618 $ 75,515 $ — $ (39 ) $ 75,476 Classified as: Cash equivalents $ 10,838 Short-term investments 64,638 $ 75,476

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
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 weighted average assumptions noted in the following table. Year Ended December 31, Service-Based Stock Options 2019 2018 2017 Expected dividend rate —% —% —% Expected stock price volatility 77.9-85.5% 82.3 – 88.3% 79.7 – 88.2% Risk-free interest rate 1.4-2.7% 2.4 – 3.1% 1.39 – 2.3% Expected life (years) 5.3 - 6.3 5.3 - 6.3 5.5 - 6.3
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, 2018 4,790,683 $ 5.85 7.7 $ 11,407 Granted 2,033,760 $ 17.51 Exercised (1,197,016 ) $ 3.64 Expired (36,561 ) $ 26.16 Forfeited (537,916 ) $ 11.26 Outstanding at December 31, 2019 5,052,950 $ 10.35 7.7 $ 37,974 Exercisable at December 31, 2019 2,385,824 $ 7.49 6.5 $ 25,113
Summary of activity for restricted stock awards	The following table summarizes the activity for restricted stock awards for the indicated periods: Restricted Stock Units Number of Restricted Stock Awards Weighted Average Grant Date Fair Value Weighted Average Term Aggregate Intrinsic Value Outstanding at December 31, 2018 — Granted 186,922 $ 17.71 $ 3,310 Vested — Forfeited (29,892 ) $ 17.24 Unvested at December 31, 2019 157,030 $ 17.80 1.6 $ 2,732
Schedule of non-cash stock-based compensation expense	Years Ended December 31, (in thousands) 2019 2018 2017 Cost of goods sold $ 2,029 $ 1,015 $ 428 Research and development 2,428 1,672 506 General, selling and administrative 8,722 4,536 1,746 Total non-cash stock-based compensation expense $ 13,179 $ 7,223 $ 2,680

Net Loss Per Common Share (Tabl

Net Loss Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2019
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	The following reflects the net loss attributable to common shareholders and share data used in the basic and diluted earnings per share computations using the two class method: Year Ended December 31, (Amounts in thousands, except per share amounts) 2019 2018 2017 Numerator: Net loss $ (9,665 ) $ (8,137 ) $ (17,286 ) Denominator: Denominator for basic and diluted EPS: weighted-average common shares outstanding 44,180 40,242 33,355 Net loss per share attributable to common shareholders (basic and diluted) $ (0.22 ) $ (0.20 ) $ (0.52 ) Anti-dilutive shares excluded from the calculation of diluted earnings per share (a) (amounts in millions): Stock options 5.1 4.8 4.6 Restricted stock unit awards 0.2 — — Warrants — — 0.9 (a) Common equivalent shares are not included in the diluted per share calculation where the effect of their inclusion would be anti-dilutive.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 December 31, 2018 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 $ 5,381 $ 5,381 $ — $ — $ 5,838 $ 5,838 $ — $ — Repurchase agreements — — — — 5,000 — 5,000 — Commercial paper 11,892 — 11,892 — 30,710 — 30,710 — Corporate notes 18,380 — 18,380 — 13,144 — 13,144 — U.S. government securities 11,295 — 11,295 — 10,166 — 10,166 — U.S. asset-backed securities 10,509 — 10,509 — 10,618 — 10,618 — $ 57,457 $ 5,381 $ 52,076 $ — $ 75,476 $ 5,838 $ 69,638 $ —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Summary of income (loss) before income taxes for U.S. and non-U.S. operations	before income taxes for U.S and non-U.S operations was as follows: Year Ended December 31, 2019 2018 2017 U.S. loss $ (9,632 ) $ (8,056 ) $ (17,066 ) Non U.S. loss (33 ) (81 ) (220 ) $ (9,665 ) $ (8,137 ) $ (17,286 )
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 federal statutory rate to the taxes reported in the consolidated statements of operations is as follows: Year Ended December 31, (In thousands) 2019 2018 2017 Loss before income taxes $ (9,665 ) $ (8,137 ) $ (17,286 ) Federal statutory rate 21 % 21 % 34 % Taxes computed at federal statutory rate (2,030 ) (1,709 ) (5,877 ) State taxes (484 ) (385 ) (1,106 ) Stock compensation (1,329 ) (605 ) 563 Federal and State Rate Change (164 ) 839 11,749 Other (49 ) 172 116 Change in valuation allowance 4,056 1,688 (5,445 ) Reported income taxes $ — $ — $ —
Schedule of deferred tax assets	Deferred tax assets (liabilities) consist of the following: Year Ended December 31, (In thousands) 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 10,542 $ 10,969 Employee benefits and stock compensation 4,329 2,798 Research and development costs 7,851 9,067 Fixed assets — 418 Intangible assets 4,350 — Operating lease liability 102 — Inventory reserve 3,303 2,339 Other, net 119 345 Total deferred tax assets 30,596 25,936 Less: valuation allowance (29,991 ) (25,936 ) Total net deferred tax assets 605 — Deferred tax liabilities: Fixed assets (605 ) — Total net deferred tax liabilities (605 ) — Net deferred tax assets and liabilities $ — $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum payments related to operating and capital leases	Future minimum payments related to operating and capital leases, as reflected under the prior guidance, for the fiscal year ended December 31, 2018 , are as follows with no changes from prior disclosure: (in thousands) Total 2019 2020 2021 2022 2023 More than 5 Years Operating leases $ 15,386 $ 4,879 $ 4,719 $ 4,754 $ 966 $ 68 $ — Capital leases 205 41 41 41 41 41 — Total $ 15,591 $ 4,920 $ 4,760 $ 4,795 $ 1,007 $ 109 $ — Payments Due by Period (in thousands) Total 2020 2021 2022 2023 2024 More than 5 Years Purchase commitments $ 1,821 $ 607 $ 607 $ 607 $ — $ — $ —

Supplementary Quarterly Finan_2

Supplementary Quarterly Financial Information (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Schedule of quarterly financial information	In thousands, except per share data First Quarter Second Quarter Third Quarter Fourth Quarter Year 2019 Revenues $ 21,810 $ 26,151 $ 30,499 $ 39,390 $ 117,850 Gross profit 13,170 17,129 21,175 28,805 80,279 Income (loss) from operations (3,358 ) (20,200 ) 3,097 9,210 (11,251 ) Net (loss) income (2,844 ) (19,792 ) 3,470 9,501 (9,665 ) Net (loss) income per share (Basic) (0.07 ) (0.45 ) 0.08 0.21 (0.22 ) Net (loss) income per share (Diluted) (0.07 ) (0.45 ) 0.07 0.20 (0.22 ) 2018 Revenues $ 18,027 $ 19,011 $ 22,484 $ 31,335 $ 90,857 Gross profit 10,361 11,284 14,346 22,706 58,697 Income (loss) from operations (4,322 ) (4,246 ) (1,336 ) 5,995 (3,909 ) Net (loss) income (7,659 ) (4,651 ) (1,069 ) 5,242 (8,137 ) Net (loss) income per share (Basic) (0.21 ) (0.12 ) (0.02 ) 0.12 (0.20 ) Net (loss) income per share (Diluted) (0.21 ) (0.12 ) (0.02 ) 0.11 (0.20 )

Organization - Narrative (Detai

Organization - Narrative (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2019USD ($)segment	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | segment									1
Accumulated deficit	$ 378,679				$ 369,014				$ 378,679	$ 369,014
Net loss	(9,501)	$ (3,470)	$ 19,792	$ 2,844	(5,242)	$ 1,069	$ 4,651	$ 7,659	9,665	8,137	$ 17,286
Cash and cash equivalents	26,889				$ 18,286				26,889	$ 18,286
Short term investments	$ 52,100								$ 52,100

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Supplementary cash flows information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Non-cash information:
Warrants exercised for common stock	$ 104	$ 3,538	$ 0
Right-of-use asset and lease liability recognized	2,599	0	0
Additions to equipment in process included in accounts payable	217	606	341
Shares exchanged between common and preferred stock	0	0	(38,389)
Cash information:
Interest paid (net of interest capitalized)	0	2,230	931
Income tax withholding paid	0	0	100
Cash, cash equivalents, and restricted cash	26,978	18,286	$ 26,862	$ 22,978
Cash and cash equivalents	26,889	18,286
Restricted cash	$ 89	$ 0

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment
Cash, cash equivalents, and restricted cash	$ 26,978		$ 18,286	$ 26,862	$ 22,978
Right Of Use Asset	25,251	$ 25,600
Lease Liability	$ 27,854	$ 27,800
Minimum
Property, Plant and Equipment
Duration of lease renewal terms	1 year
Maximum
Property, Plant and Equipment
Duration of lease renewal terms	5 years
Equipment and computers | Minimum
Property, Plant and Equipment
Useful lives (in years)	3 years
Equipment and computers | Maximum
Property, Plant and Equipment
Useful lives (in years)	5 years
Furniture and fixtures
Property, Plant and Equipment
Useful lives (in years)	5 years
Building improvements and leasehold improvements | Maximum
Property, Plant and Equipment
Useful lives (in years)	10 years

Revenue - (Details)

Revenue - (Details) - USD ($) $ in Thousands	Dec. 21, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONCENTRATION
Allowance for doubtful accounts		$ 3,900				$ 2,000				$ 3,900	$ 2,000
Change in estimate of uncollectible (percent)										0.50%
Change in revenue recognized due to 0.5% change in uncollectible percentage										$ 500
Increase (decrease) to revenues		$ 39,390	$ 30,499	$ 26,151	$ 21,810	$ 31,335	$ 22,484	$ 19,011	$ 18,027	117,850	90,857	$ 62,760
Warrants issued in connection with debt arrangement										0	0	207
ICT
CONCENTRATION
Initial license agreement payment	$ 5,200
ICT | Potential Payment
CONCENTRATION
Other commitment	1,200											1,200
ICT | December 21, 2017 Warrants
CONCENTRATION
Warrants issued in connection with debt arrangement	$ 4,000
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
CONCENTRATION
Increase (decrease) to revenues										$ 654	$ (182)	$ (350)

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Product sales, net	$ 39,390	$ 30,499	$ 26,151	$ 21,810	$ 31,335	$ 22,484	$ 19,011	$ 18,027	$ 117,850	$ 90,857	$ 62,760
Revenues									117,850	90,857	63,924
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Disaggregation of Revenue [Line Items]
Product sales, net									654	(182)	(350)
Other revenue
Disaggregation of Revenue [Line Items]
Product sales, net									0	0	1,164
Through Intermediary | Implants | Contract rate
Disaggregation of Revenue [Line Items]
Product sales, net									56,185	42,926	37,796
Through Intermediary | Implants | Time-and-materials contract
Disaggregation of Revenue [Line Items]
Product sales, net									17,076	8,621	1,299
Time-and-materials contract | Implants | Time-and-materials contract
Disaggregation of Revenue [Line Items]
Product sales, net									1,529	2,257	0
Provider or Facility | Implants | Contract rate
Disaggregation of Revenue [Line Items]
Product sales, net									13,933	12,122	3,393
Directly to consumer | Biopsy kits
Disaggregation of Revenue [Line Items]
Product sales, net									2,243	1,997	1,764
Directly to consumer | Epicel
Disaggregation of Revenue [Line Items]
Product sales, net									$ 26,230	$ 23,116	$ 18,858

Revenue - Schedules of concentr

Revenue - Schedules of concentration of risk (Details) - Customer concentration	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue Concentration | MACI
Product Information [Line Items]
Concentration risk (as a percent)	8.00%	16.00%	35.00%
Revenue Concentration | Epicel
Product Information [Line Items]
Concentration risk (as a percent)	7.00%	7.00%	10.00%
Accounts Receivable Concentration | MACI
Product Information [Line Items]
Concentration risk (as a percent)	8.00%	2.00%
Accounts Receivable Concentration | Epicel
Product Information [Line Items]
Concentration risk (as a percent)	2.00%	4.00%

Selected Balance Sheet Compon_3

Selected Balance Sheet Components - Schedule of inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Inventory:
Raw materials	$ 6,085	$ 2,872
Work-in-process	541	638
Finished goods	190	48
Inventory	$ 6,816	$ 3,558

Selected Balance Sheet Compon_4

Selected Balance Sheet Components - Schedule of property and equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property and equipment, net:
Total property and equipment, gross		$ 13,411
Financing right-of-use lease	$ 148
Total property and equipment, gross	16,364
Less accumulated depreciation	(9,220)
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization	7,144
Less accumulated depreciation		(7,505)
Property and Equipment		5,906
Depreciation expense	1,700	1,400	$ 1,600
Machinery and equipment
Property and equipment, net:
Total property and equipment, gross	3,152	1,536
Furniture, fixtures and office equipment
Property and equipment, net:
Total property and equipment, gross	775	775
Computer equipment and software
Property and equipment, net:
Total property and equipment, gross	6,174	3,712
Leasehold improvements
Property and equipment, net:
Total property and equipment, gross	5,256	4,587
Construction in process
Property and equipment, net:
Total property and equipment, gross	$ 859	$ 2,801

Selected Balance Sheet Compon_5

Selected Balance Sheet Components - Schedule of accrued expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued expenses
Bonus related compensation	$ 5,116	$ 5,161
Employee related accruals	1,785	1,559
Other accrued expenses	1,047	210
Accrued expenses	$ 7,948	$ 6,930

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($) $ in Thousands	Dec. 19, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Repayments of debt		$ 0	$ 17,532	$ 7,151
Loss on extinguishment of debt		$ 0	838	860
SVB and MidCap | Term loan
Debt Instrument [Line Items]
Repayments of debt	$ 17,100
Pre-payment premium (as a percent)	1.50%
Payment for debt extinguishment or debt prepayment cost	$ 200
Stated percentage for final payment (as a percent)	3.60%
Debt instrument final payment	$ 500
Loss on extinguishment of debt			$ 800	$ 900

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Leases [Abstract]
Short-term lease costs (less than)	$ 100
Net lease assets	25,251			$ 25,600
Lease liability	27,854			$ 27,800
Operating lease expense	5,400
Finance lease expense	100
Operating lease expense		$ 5,200
Finance lease expense		100
Measurement of lease liability	5,000
Lease not yet commenced, liability	$ 2,100
Term of contract	4 years 3 months 18 days
Rent expense		$ 5,500	$ 5,600

Leases - Assets And Liabilities

Leases - Assets And Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Assets
Operating	$ 25,103
Finance	148
Right-of-use assets	25,251	$ 25,600
Current
Operating	5,461
Finance	41
Lease liability current	5,502
Non-current
Operating	22,242
Finance	110
Lease liability noncurrent	$ 22,352

Leases - Maturities of lease li

Leases - Maturities of lease liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019
Operating Leases
2020	$ 5,461
2021	5,358
2022	5,316
2023	5,294
2024	5,302
more than 5 years	11,270
Total	38,001
Less: Interest	(10,298)
Present value of lease liabilities	27,703
Finance Leases
2020	41
2021	41
2022	41
2023	41
2024	0
more than 5 years	0
Total	164
Less: Interest	(13)
Present value of lease liabilities	151
2020	5,502
2021	5,399
2022	5,357
2023	5,335
2024	5,302
more than 5 years	11,270
Total	38,165
Less: Interest	(10,311)
Present value of lease liabilities	$ 27,854	$ 27,800

Leases - Lease term and discoun

Leases - Lease term and discount rate (Details)	Dec. 31, 2019
Leases [Abstract]
Operating lease term (in years)	6 years 9 months 18 days
Finance lease term (in years)	3 years 6 months
Operating lease discount rate ( as a percent )	9.44%
Finance lease discount rate ( as a percent )	5.00%

Leases - Schedule Prior To Adop

Leases - Schedule Prior To Adoption (Details) $ in Thousands	Dec. 31, 2019USD ($)
Operating leases
Total	$ 15,386
2020	4,879
2021	4,719
2022	4,754
2023	966
2024	68
More than 5 Years	0
Capital leases
Total	205
2020	41
2021	41
2022	41
2023	41
2024	41
More than 5 Years	0
Total
Total	15,591
2020	4,920
2021	4,760
2022	4,795
2023	1,007
2024	109
More than 5 Years	$ 0

Cash Equivalents and Investme_3

Cash Equivalents and Investments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019
Marketable Securities [Line Items]
Amortized Cost	$ 75,515	$ 57,436
Gains	0	21
Losses	(39)	0
Fair Value	75,476	57,457
Cash equivalents
Marketable Securities [Line Items]
Fair Value	10,838	5,381
Short-term investments
Marketable Securities [Line Items]
Fair Value	64,638	42,829
Long term investments
Marketable Securities [Line Items]
Fair Value		9,247
Money market funds
Marketable Securities [Line Items]
Amortized Cost	5,838	5,381
Gains	0	0
Losses	0	0
Fair Value	5,838	5,381
Repurchase agreements
Marketable Securities [Line Items]
Amortized Cost	5,000
Gains	0
Losses	0
Fair Value	5,000
Payments to acquire debt securities, available-for-sale	5,000
Commercial paper
Marketable Securities [Line Items]
Amortized Cost	30,710	11,892
Gains	0	0
Losses	0	0
Fair Value	30,710	11,892
Corporate notes
Marketable Securities [Line Items]
Amortized Cost	13,168	18,369
Gains	0	11
Losses	(24)	0
Fair Value	13,144	18,380
U.S. government securities
Marketable Securities [Line Items]
Amortized Cost	10,167	11,291
Gains	0	4
Losses	(1)	0
Fair Value	10,166	11,295
U.S. asset-backed securities
Marketable Securities [Line Items]
Amortized Cost	10,632	10,503
Gains	0	6
Losses	(14)	0
Fair Value	$ 10,618	$ 10,509

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended			60 Months Ended
	Jan. 31, 2019	Dec. 31, 2018	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Stock-Based Compensation
Shares issued under the Employee Stock Purchase Plan (in shares)				$ 932	$ 656	$ 425
Granted (in shares)				2,033,760
Expected to vest (in shares)				4,700,318			4,700,318
Total unrecognized compensation cost				$ 16,600			$ 16,600
Intrinsic value of stock options exercised				$ 12,400	10,300	700
Service-based stock options
Stock-Based Compensation
Expiration period				10 years
Vesting period				4 years
Stock-based compensation expense				$ 11,800	$ 6,900	$ 2,500
Granted (in shares)				2,033,760
Weighted average grant-date fair value (in dollars per share)				$ 12.62	$ 6.96	$ 1.99
Weighted average period over which unrecognized compensation is expected to be recognized				3 years 2 months 12 days
Employee stock
Stock-Based Compensation
Common stock available for issuance (in shares)				1,000,000			1,000,000
Common stock granted since inception (in shares)							595,799
Shares purchased during period (in shares)	19,076
Shares issued under the Employee Stock Purchase Plan (in shares)		$ 200
Stock-based compensation expense				$ 300	$ 300	$ 200
Restricted Stock Units (RSUs)
Stock-Based Compensation
Vesting period				4 years
Stock-based compensation expense				$ 1,000
Unrecognized compensation cost				$ 1,800			$ 1,800
Weighted average period over which unrecognized compensation is expected to be recognized				3 years 1 month 6 days
Grant-date fair value of restricted stock units granted				$ 3,310
Restricted stock units granted (shares)				186,922	0
Prior Plans
Stock-Based Compensation
Awards available for future grant under the Plan (in shares)				0			0
Omnibus Incentive Plan 2019
Stock-Based Compensation
Awards available for future grant under the Plan (in shares)				3,344,242			3,344,242
Nonemployee directors | Service-based stock options
Stock-Based Compensation
Expiration period				10 years
Vesting period			1 year	1 year
Granted (in shares)				78,750

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of fair value assumptions (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock-Based Compensation
Expected dividend rate	0.00%	0.00%	0.00%
Service-based stock options | Minimum
Stock-Based Compensation
Expected stock price volatility	77.90%	82.30%	79.70%
Risk-free interest rate	1.40%	2.40%	1.39%
Expected life (years)	5 years 3 months 18 days	5 years 3 months 18 days	5 years 6 months
Service-based stock options | Maximum
Stock-Based Compensation
Expected stock price volatility	85.50%	88.30%	88.20%
Risk-free interest rate	2.70%	3.10%	2.30%
Expected life (years)	6 years 3 months 18 days	6 years 3 months 18 days	6 years 3 months 18 days

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of activity for service-based stock options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Options
Outstanding at the beginning of the period (in shares)	4,790,683
Granted (in shares)	2,033,760
Exercised (in shares)	(1,197,016)
Expired (in shares)	(36,561)
Forfeited (in shares)	(537,916)
Outstanding at the end of the period (in shares)	5,052,950	4,790,683
Exercisable at the end of the period (in shares)	2,385,824
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 5.85
Granted (in dollars per share)	17.51
Exercised (in dollars per share)	3.64
Expired (in dollars per share)	26.16
Forfeited (in dollars per share)	11.26
Outstanding at the end of the period (in dollars per share)	10.35	$ 5.85
Exercisable at the end of the period (in dollars per share)	$ 7.49
Weighted Average Remaining Contractual Term
Outstanding	7 years 8 months 12 days	7 years 8 months 12 days
Exercisable at end of period	6 years 6 months
Aggregate Intrinsic Value
Outstanding	$ 37,974	$ 11,407
Exercised	12,400	$ 10,300	$ 700
Exercisable at end of period	$ 25,113
Service-based stock options
Options
Granted (in shares)	2,033,760

Stock-Based Compensation - Sc_3

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total non-cash stock-based compensation expense	$ 13,179	$ 7,223	$ 2,680
Cost of goods sold
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total non-cash stock-based compensation expense	2,029	1,015	428
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total non-cash stock-based compensation expense	2,428	1,672	506
General, selling and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total non-cash stock-based compensation expense	$ 8,722	$ 4,536	$ 1,746

Stock-Based Compensation - Sc_4

Stock-Based Compensation - Schedule of restricted stock awards activity (Details) - Restricted Stock Units (RSUs) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Number of Restricted Stock Awards
Outstanding at December 31, 2018 (shares)	0
Granted (shares)	186,922	0
Vested (shares)	0
Forfeited (shares)	(29,892)
Unvested at December 31, 2019 (shares)	157,030	0
Weighted Average Grant Date Fair Value
Unvested at December 31, 2018 (in usd per share)
Granted (in usd per share)	17.71
Forfeited (in usd per share)	17.24
Unvested at December 31, 2019 (in usd per share)	$ 17.80
Unvested at December 31, 2019, Weighted Average Term	1 year 7 months 6 days
Aggregate Intrinsic Value (Thousands)
Granted, Aggregate Intrinsic Value	$ 3,310
Unvested at December 31, 2019, Aggregate Intrinsic Value	$ 2,732

Shareholders' Equity - Narrativ

Shareholders' Equity - Narrative (Details) - Public Stock Offering $ / shares in Units, $ in Millions	1 Months Ended
	Jun. 30, 2018USD ($)$ / sharesshares
Shareholders' Equity
Sale of stock, consideration received on transaction	$ 70.1
Commission and issuance cost	$ 4.7
Common Stock
Shareholders' Equity
Sale of stock, number of shares issued in transaction (in shares) | shares	5,750,000
Public offering price per share (in dollars per share) | $ / shares	$ 13

Net Loss Per Common Share - Nar

Net Loss Per Common Share - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net loss	$ 9,501	$ 3,470	$ (19,792)	$ (2,844)	$ 5,242	$ (1,069)	$ (4,651)	$ (7,659)	$ (9,665)	$ (8,137)	$ (17,286)
Denominator for basic and diluted EPS:
Weighted-average common shares outstanding (in shares)									44,180	40,242	33,355
Net loss per share attributable to common shareholders (Basic and Diluted) (in dollars per share)									$ (0.22)	$ (0.20)	$ (0.52)
Service-based stock options
Denominator for basic and diluted EPS:
Aggregate number of common equivalent shares (related to options, warrants and preferred stock) that have been excluded from computations of diluted net loss per common share (in shares)									5,100	4,800	4,600
Restricted Stock Units (RSUs)
Denominator for basic and diluted EPS:
Aggregate number of common equivalent shares (related to options, warrants and preferred stock) that have been excluded from computations of diluted net loss per common share (in shares)									200	0	0
Warrants
Denominator for basic and diluted EPS:
Aggregate number of common equivalent shares (related to options, warrants and preferred stock) that have been excluded from computations of diluted net loss per common share (in shares)									0	0	900

Stock Purchase Warrants - Narra

Stock Purchase Warrants - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 27, 2017	Dec. 21, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 06, 2017
Stock Purchase Warrants
Proceeds from issuance of warrants			$ 0	$ 0	$ 207
ICT
Stock Purchase Warrants
Initial license agreement payment		$ 5,200
ICT | Potential Payment
Stock Purchase Warrants
Other commitment		1,200			$ 1,200
Common Stock
Stock Purchase Warrants
Conversion of preferred stock for common stock (Note 9) (in shares)					1,094,000
Exercise of warrants resulting in the issuance of common stock (in shares)			20,000	681,000	817,000
December 2017 Warrants
Stock Purchase Warrants
Exercise price (in dollars per share)			$ 4.27
Warrants outstanding (in shares)			0
December 2017 Warrants | Common Stock
Stock Purchase Warrants
Conversion of preferred stock for common stock (Note 9) (in shares)			19,808
December 21, 2017 Warrants | ICT
Stock Purchase Warrants
Exercise price (in dollars per share)						$ 0.01
Proceeds from issuance of warrants		$ 4,000
Total shares issuable on exercise		818,424
Share price (in dollars per share)						$ 4.90
Exercise of warrants resulting in the issuance of common stock (in shares)	816,850
Warrants outstanding (in shares)			0

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	$ 57,457	$ 75,476
Recurring
Liabilities that are measured at fair value on a recurring basis
Repurchase agreements	0	5,000
Assets, fair value	57,457	75,476
Recurring | Level 1
Liabilities that are measured at fair value on a recurring basis
Repurchase agreements	0	0
Assets, fair value	5,381	5,838
Recurring | Level 2
Liabilities that are measured at fair value on a recurring basis
Repurchase agreements	0	5,000
Assets, fair value	52,076	69,638
Recurring | Level 3
Liabilities that are measured at fair value on a recurring basis
Repurchase agreements	0	0
Assets, fair value	0	0
Money market funds | Recurring
Liabilities that are measured at fair value on a recurring basis
Money market funds	5,381	5,838
Money market funds | Recurring | Level 1
Liabilities that are measured at fair value on a recurring basis
Money market funds	5,381	5,838
Money market funds | Recurring | Level 2
Liabilities that are measured at fair value on a recurring basis
Money market funds	0	0
Money market funds | Recurring | Level 3
Liabilities that are measured at fair value on a recurring basis
Money market funds	0	0
Commercial paper | Recurring
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	11,892	30,710
Commercial paper | Recurring | Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Commercial paper | Recurring | Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	11,892	30,710
Commercial paper | Recurring | Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Corporate Note Securities | Recurring
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	18,380	13,144
Corporate Note Securities | Recurring | Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Corporate Note Securities | Recurring | Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	18,380	13,144
Corporate Note Securities | Recurring | Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
US Government Debt Securities | Recurring
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	11,295	10,166
US Government Debt Securities | Recurring | Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
US Government Debt Securities | Recurring | Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	11,295	10,166
US Government Debt Securities | Recurring | Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Asset-backed Securities
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	10,509	10,618
Asset-backed Securities | Recurring
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	10,509	10,618
Asset-backed Securities | Recurring | Level 1
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	0	0
Asset-backed Securities | Recurring | Level 2
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	10,509	10,618
Asset-backed Securities | Recurring | Level 3
Liabilities that are measured at fair value on a recurring basis
Debt securities, fair value	$ 0	$ 0

Income Taxes - Components of In

Income Taxes - Components of Income (Loss) Before Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Loss before income taxes	$ (9,665)	$ (8,137)	$ (17,286)
U.S. loss
Operating Loss Carryforwards [Line Items]
Loss before income taxes	(9,632)	(8,056)	(17,066)
Non U.S. loss
Operating Loss Carryforwards [Line Items]
Loss before income taxes	$ (33)	$ (81)	$ (220)

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of income taxes computed using the federal statutory rate to the taxes reported in consolidated statements of operations
Loss before income taxes	$ (9,665)	$ (8,137)	$ (17,286)
Federal statutory rate	21.00%	21.00%	34.00%
Taxes computed at federal statutory rate	$ (2,030)	$ (1,709)	$ (5,877)
State taxes	(484)	(385)	(1,106)
Stock compensation	(1,329)	(605)	563
Federal and State Rate Change	(164)	839	11,749
Other	(49)	172	116
Change in valuation allowance	4,056	1,688	(5,445)
Reported income taxes	0	0	$ 0
Deferred tax assets
Net operating loss carryforwards	10,542	10,969
Employee benefits and stock compensation	4,329	2,798
Research and development costs	7,851	9,067
Fixed assets	0	418
Intangible assets	4,350	0
Operating lease liability	102	0
Inventory reserve	3,303	2,339
Other, net	119	345
Total deferred tax assets	30,596	25,936
Less: valuation allowance	(29,991)	(25,936)
Total net deferred tax assets	605	0
Deferred tax liabilities:
Fixed assets	(605)	0
Total net deferred tax liabilities	(605)	0
Net deferred tax assets and liabilities	$ 0	$ 0

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 22, 2017	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 16, 2014
Operating Loss Carryforwards [Line Items]
Profit (loss) from operations		$ 9,210	$ 3,097	$ (20,200)	$ (3,358)	$ 5,995	$ (1,336)	$ (4,246)	$ (4,322)	$ (11,251)	$ (3,909)	$ (14,984)
Projected annual limitation on the use of the net operating losses that existed prior to September 17, 2014													$ 800
Increase (decrease) in valuation allowance										4,100	1,700
Change in valuation allowance										$ 4,056	1,688	$ (5,445)
Tax Cuts and Jobs Act of 2017, incomplete accounting, change in tax rate, deferred tax asset, provisional income tax expense	$ 11,700
Federal | Internal Revenue Service
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards						42,200					42,200
Profit (loss) from operations											(1,500)
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards						$ 24,500					$ 24,500

Employee Savings Plan - Narrati

Employee Savings Plan - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Contributions made under 401(k) savings plan	$ 0.7	$ 0.6	$ 0.6

Nexobrid License and Supply A_2

Nexobrid License and Supply Agreements (Details) - MediWound Ltd $ in Millions	1 Months Ended
	May 31, 2019USD ($)
Related Party Transaction [Line Items]
License Agreement, Payable	$ 17.5
Payable	17.5
Contingent consideration	7.5
Max contingent consideration	125
Sales Initial milestone	$ 75

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended
	Oct. 31, 2015	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Purchase obligation, annual commitment	$ 600	$ 607
Purchase obligation, renewal option, term	5 years
Purchase obligation, automatic renewal, term	5 years

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Oct. 31, 2015
Purchase commitments
Total	$ 1,821
2020	607	$ 600
2021	607
2022	607
2023	0
2024	0
More than 5 Years	$ 0

Supplementary Quarterly Finan_3

Supplementary Quarterly Financial Information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Product sales, net	$ 39,390	$ 30,499	$ 26,151	$ 21,810	$ 31,335	$ 22,484	$ 19,011	$ 18,027	$ 117,850	$ 90,857	$ 62,760
Gross profit	28,805	21,175	17,129	13,170	22,706	14,346	11,284	10,361	80,279	58,697	33,570
Income (loss) from operations	9,210	3,097	(20,200)	(3,358)	5,995	(1,336)	(4,246)	(4,322)	(11,251)	(3,909)	(14,984)
Net (loss) income	$ 9,501	$ 3,470	$ (19,792)	$ (2,844)	$ 5,242	$ (1,069)	$ (4,651)	$ (7,659)	$ (9,665)	$ (8,137)	$ (17,286)
Net (loss) income per share (Basic) (in USD per share)	$ 0.21	$ 0.08	$ (0.45)	$ (0.07)	$ 0.12	$ (0.02)	$ (0.12)	$ (0.21)	$ (0.22)	$ (0.20)
Net (loss) income per share (Diluted) (in USD per share)	$ 0.20	$ 0.07	$ (0.45)	$ (0.07)	$ 0.11	$ (0.02)	$ (0.12)	$ (0.21)	$ (0.22)	$ (0.20)