Vericel (VCEL) 10-Q 6 Aug 19 2019 Q2 Quarterly report Financial data

Cover

Cover - shares	6 Months Ended
	Jun. 30, 2019	Jul. 31, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	001-35280
Entity Registrant Name	VERICEL CORP
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		44,136,896,000
Entity Central Index Key	0000887359
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 13,962	$ 18,286
Short-term investments	52,047	64,638
Accounts receivable (net of allowance for doubtful accounts of $748 and $514, respectively)	21,084	23,454
Inventory	4,788	3,558
Other current assets	2,167	2,847
Total current assets	94,048	112,783
Property and equipment, net	6,963	5,906
Right-of-use assets	24,815	0
Total assets	125,826	118,689
Current liabilities:
Accounts payable	5,250	7,108
Accrued expenses	4,701	6,930
Current portion of operating lease liabilities	2,558	0
Other liabilities	34	754
Total current liabilities	12,543	14,792
Operating lease liabilities	24,607	0
Other long-term liabilities	134	1,666
Total liabilities	37,284	16,458
COMMITMENTS AND CONTINGENCIES
Shareholders’ equity:
Common stock, no par value; shares authorized — 75,000; shares issued and outstanding — 44,066 and 43,578, respectively	480,050	471,180
Other comprehensive gain (loss)	38	(39)
Warrants	104	104
Accumulated deficit	(391,650)	(369,014)
Total shareholders’ equity	88,542	102,231
Total liabilities and shareholders’ equity	$ 125,826	$ 118,689

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 748	$ 514
Common stock, authorized (in shares)	75,000,000	75,000,000
Common stock, issued (in shares)	44,066,000	43,578,000
Common stock, outstanding (in shares)	44,066,000	43,578,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Product sales, net	$ 26,151	$ 19,011	$ 47,961	$ 37,038
Gross profit	17,129	11,284	30,299	21,645
Research and development	21,070	3,739	24,078	7,468
Selling, general and administrative	16,259	11,791	29,779	22,745
Total operating expenses	37,329	15,530	53,857	30,213
Loss from operations	(20,200)	(4,246)	(23,558)	(8,568)
Other income (expense):
Increase in fair value of warrants	0	(37)	0	(2,944)
Interest income	428	83	908	83
Interest expense	(2)	(448)	(4)	(880)
Other income (expense)	(18)	(3)	18	(1)
Total other income (expense)	408	(405)	922	(3,742)
Net loss	$ (19,792)	$ (4,651)	$ (22,636)	$ (12,310)
Net loss per share attributable to common shareholders (Basic and Diluted) (in dollars per share)	$ (0.45)	$ (0.12)	$ (0.52)	$ (0.33)
Weighted average number of common shares outstanding (Basic and Diluted) (in shares)	43,956	38,349	43,841	37,251
Product
Product sales, net	$ 26,151	$ 19,011	$ 47,961	$ 37,038
Cost of product sales	$ 9,022	$ 7,727	$ 17,662	$ 15,393

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (19,792)	$ (4,651)	$ (22,636)	$ (12,310)
Other comprehensive loss:
Unrealized gain on investments	35	0	38	0
Comprehensive loss	$ (19,757)	$ (4,651)	$ (22,598)	$ (12,310)

CONSOLIDATED STATEMENTS OF SHAR

CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Warrants Amounts	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017		35,861,000
Beginning balance at Dec. 31, 2017	$ 22,540	$ 383,020	$ 397	$ 0	$ (360,877)
Increase (Decrease) in Shareholders' Equity
Net loss	(7,659)				(7,659)
Compensation expense related to stock options granted, net of forfeitures	1,348	$ 1,348
Stock option exercises (in shares)		253,000
Stock option exercises	851	$ 851
Shares issued under the Employee Stock Purchase Plan ( in shares )		28,000
Shares issued under the Employee Stock Purchase Plan	127	$ 127
Exercise of warrants resulting in the issuance of common stock (Note 11) (in shares)		360,000
Exercise of warrants resulting in the issuance of common stock	1,727	$ 1,727
Net change in warrant valuation of exercised warrants	2,001	$ 2,001
Ending balance (in shares) at Mar. 31, 2018		36,502,000
Ending balance at Mar. 31, 2018	20,935	$ 389,074	397	0	(368,536)
Beginning balance (in shares) at Dec. 31, 2017		35,861,000
Beginning balance at Dec. 31, 2017	22,540	$ 383,020	397	0	(360,877)
Increase (Decrease) in Shareholders' Equity
Net loss	(12,310)
Ending balance (in shares) at Jun. 30, 2018		42,684,000
Ending balance at Jun. 30, 2018	90,598	$ 463,483	302	0	(373,187)
Beginning balance (in shares) at Mar. 31, 2018		36,502,000
Beginning balance at Mar. 31, 2018	20,935	$ 389,074	397	0	(368,536)
Increase (Decrease) in Shareholders' Equity
Net loss	(4,651)				(4,651)
Compensation expense related to stock options granted, net of forfeitures	2,465	$ 2,465
Issuance of common stock, net of issuance costs (in shares)		5,750,000
Issuance of common stock, net of issuance costs	70,090	$ 70,090
Stock option exercises (in shares)		306,000
Stock option exercises	964	$ 964
Shares issued under the Employee Stock Purchase Plan ( in shares )		31,000
Shares issued under the Employee Stock Purchase Plan	148	$ 148
Exercise of warrants resulting in the issuance of common stock (Note 11) (in shares)		95,000
Exercise of warrants resulting in the issuance of common stock	238	$ 333	(95)
Net change in warrant valuation of exercised warrants	409	$ 409
Ending balance (in shares) at Jun. 30, 2018		42,684,000
Ending balance at Jun. 30, 2018	90,598	$ 463,483	302	0	(373,187)
Beginning balance (in shares) at Dec. 31, 2018		43,578,000
Beginning balance at Dec. 31, 2018	102,231	$ 471,180	104	(39)	(369,014)
Increase (Decrease) in Shareholders' Equity
Net loss	(2,844)				(2,844)
Compensation expense related to stock options granted, net of forfeitures	2,628	$ 2,628
Stock option exercises (in shares)		228,000
Stock option exercises	780	$ 780
Shares issued under the Employee Stock Purchase Plan ( in shares )		19,000
Shares issued under the Employee Stock Purchase Plan	218	$ 218
Change in unrealized gain (loss) on investments	42			42
Ending balance (in shares) at Mar. 31, 2019		43,825,000
Ending balance at Mar. 31, 2019	103,055	$ 474,806	104	3	(371,858)
Beginning balance (in shares) at Dec. 31, 2018		43,578,000
Beginning balance at Dec. 31, 2018	102,231	$ 471,180	104	(39)	(369,014)
Increase (Decrease) in Shareholders' Equity
Net loss	(22,636)
Ending balance (in shares) at Jun. 30, 2019		44,066,000
Ending balance at Jun. 30, 2019	88,542	$ 480,050	104	38	(391,650)
Beginning balance (in shares) at Mar. 31, 2019		43,825,000
Beginning balance at Mar. 31, 2019	103,055	$ 474,806	104	3	(371,858)
Increase (Decrease) in Shareholders' Equity
Net loss	(19,792)				(19,792)
Compensation expense related to stock options granted, net of forfeitures	4,183	$ 4,183
Stock option exercises (in shares)		227,000
Stock option exercises	850	$ 850
Shares issued under the Employee Stock Purchase Plan ( in shares )		14,000
Shares issued under the Employee Stock Purchase Plan	211	$ 211
Change in unrealized gain (loss) on investments	35			35
Ending balance (in shares) at Jun. 30, 2019		44,066,000
Ending balance at Jun. 30, 2019	$ 88,542	$ 480,050	$ 104	$ 38	$ (391,650)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities:
Net loss	$ (22,636)	$ (12,310)
Adjustments to reconcile net loss to net cash used for operating activities:
Depreciation and amortization expense	698	813
Stock compensation expense	6,810	3,807
Change in fair value of warrants	0	2,944
Loss on sale of fixed assets	0	23
Foreign currency translation loss	13	49
Amortization of premiums and discounts on marketable securities	(408)	0
Non-cash lease cost	1,139	0
Change in operating assets and liabilities:
Inventory	(1,230)	68
Accounts receivable	2,370	771
Prepaid and other current assets	680	254
Accounts payable	(2,238)	(1,049)
Accrued expenses	(2,229)	(462)
Operating lease liabilities	(1,007)	0
Other assets and liabilities, net	(187)	56
Net cash used in operating activities	(18,225)	(5,036)
Investing activities:
Purchases of short-term investments	(32,402)	0
Maturities of short-term investments	45,477	0
Expenditures for property, plant and equipment	(1,224)	(979)
Net cash provided by (used in) investing activities	11,851	(979)
Financing activities:
Net proceeds from equity offering	0	70,090
Net proceeds from common stock issuance due to stock option exercises	2,059	2,096
Proceeds from exercise of warrants	0	1,965
Other	(9)	(29)
Net cash provided by financing activities	2,050	74,122
Net increase (decrease) in cash and cash equivalents	(4,324)	68,107
Cash and cash equivalents at beginning of period	18,286	26,862
Cash and cash equivalents at end of period	$ 13,962	$ 94,969

Organization

Organization	6 Months Ended
	Jun. 30, 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 related to the MACI ® , Epicel ® and Carticel ® 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. At the end of the second quarter of 2017, the Company removed Carticel (autologous cultured chondrocytes), an earlier generation autologous chrondocyte implant (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 greater than or equal to 30 percent of total body surface area (TBSA). The Company also entered into exclusive license and supply agreements with MediWound Ltd. (MediWound) to commercialize NexoBrid ® in all countries in 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 a U.S. Biologics License Application (BLA) currently is targeted for submission to the U.S. Food and Drug Administration (FDA) in the second quarter of 2020. The Company operates its business primarily in the U.S. in one reportable segment — the research, product development, manufacture and distribution of advanced therapies for use in the treatment of specific diseases. The accompanying condensed 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 June 30, 2019 , the Company has an accumulated deficit of $391.7 million and had a net loss of $19.8 million and $22.6 million during the three and six months ended June 30, 2019 . The Company had cash and cash equivalents of $14.0 million , and short-term investments of $52.0 million as of June 30, 2019 . The Company expects that existing cash, cash equivalents and short-term investments will be sufficient to support the Company's current operations through at least 12 months from the issuance of these financial statements. The Company may seek additional funding through debt or equity financings. 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.

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2019
Basis of Presentation [Abstract]
Basis of Presentation	Basis of Presentation The condensed consolidated financial statements included herein have been prepared in accordance with the rules and regulations of the U.S. Securities and Exchange Commission (SEC). The preparation of condensed consolidated financial statements in conformity with generally accepted accounting principles in the United States of America (U.S. GAAP) requires management to make estimates, judgments, and assumptions that may affect the reported amounts of assets, liabilities, equity, revenues and expenses. Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been omitted pursuant to such rules and regulations. The financial statements reflect, in the opinion of management, all adjustments (consisting only of normal, recurring adjustments) necessary to state fairly the financial position and results of operations as of and for the periods indicated. The results of operations for the three and six months ended June 30, 2019 , are not necessarily indicative of the results to be expected for the full year or for any other period. The June 30, 2019 condensed consolidated balance sheet data was derived from the Company’s audited consolidated financial statements, but does not include all disclosures required by U.S. GAAP. These condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and the notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2018 , as filed with the SEC on February 26, 2019 (Annual Report). Consolidated Statement of Cash Flows The following table presents certain supplementary cash flows information for the six months ended June 30, 2019 and 2018 : Six Months Ended June 30, (In thousands) 2019 2018 Supplementary Cash Flows information: Warrants exercised for common stock $ — $ 2,409 Interest paid (net of interest capitalized) 4 754 Additions to equipment in process included in accounts payable 365 459 Right-of-use asset and lease liability recognized 560 —

Recent Accounting Pronouncement

Recent Accounting Pronouncements	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting for Leases The 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 leasing Accounting Standard Update 2016-02, 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. The guidance is effective for annual reporting periods beginning after December 15, 2019. The Company is currently in the process of evaluating the impact to its consolidated financial statements.

Revenue

Revenue	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Revenue Recognition and Net Product Sales 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 doctor) 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 The Company recognizes product revenues from sales of MACI implants upon delivery at which time the customer is in control of the implant and the claim is billable. Prior authorization or 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. Depending upon the type of contract and payer for the MACI implant, the Company's net product revenues are either based on contracted rates or estimated based on expected payments from the insurance provider, hospital or patient. The estimates of such payment amounts vary by customer and payer and are based on either contracted rates, publicly available rates or past payer precedents. Changes in estimates are recorded through revenue in the period such change occurs. Net product revenues from sales to distributors may include a prompt pay discount. On July 25, 2018 and August 10, 2018, the Company entered into amendments to its distribution agreement with Orsini Pharmaceutical Services, Inc. (Orsini). The amendments modified certain payment terms for surgeries after June 15, 2018. In addition, under the revised agreement, the parties agreed to limit Orsini's right to serve as the Company's exclusive distributor for MACI to a specified set of payers as the Company moved to a limited expanded network of distributors. The agreement with Orsini includes a provision whereby the Company retains the credit and collection risk from the end customer on implants after June 15, 2018. Orsini performs the collection activities. The net product revenues for these cases are based on expected payments from the insurance provider, hospital or patient. The estimates of such payment amounts vary by customer and payer and are based on either contracted rates, publicly available rates or past payer precedents. Changes in estimates are recorded through revenue in the period in which such change occurs. On April 18, 2019, the Company entered into an amendment with Orsini that extended the term of the agreement until May 2022, modified the per case dispensing fee, and eliminated Orsini’s exclusivity for all payers. On July 26, 2018, the Company entered into a Dispensing Agreement (Dispensing Agreement) with AllCare Plus Pharmacy, Inc. (AllCare). Pursuant to the Dispensing Agreement, the Company appoints AllCare as a non-exclusive specialty pharmacy provider of MACI. The Company pays AllCare a fee for each patient to whom MACI is dispensed. Under the Dispensing Agreement, the Company retains the credit and collection risk from the end customer on all implants. Depending upon the type of contract and payer for the MACI implant, the Company's net product revenues are based on contracted rates or estimated based on expected payments from the insurance provider, hospital or patient. The estimates of such payment amounts vary by customer and payer and are based on either contracted rates, publicly available rates or past payer precedents. Changes in estimates are recorded through revenue in the period such change occurs. On May 1, 2019, the Company entered into an amendment with AllCare that extended the term of the Dispensing Agreement until May 2022 and modified the per case dispensing fee. 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. Revenue by Product and Customer The following table and description below reflect the products from which the Company generated its revenue: Three Months Ended June 30, Six Months Ended June 30, Revenue by product (in thousands) 2019 2018 2019 2018 MACI implants and kits Implants based on contracted rate sold through a specialty pharmacy (a) $ 12,989 $ 7,363 $ 22,776 $ 15,155 Implants subject to third-party reimbursement sold through a specialty pharmacy (b) 3,459 2,639 6,202 3,647 Implants sold direct based on contracted rates (c) 3,450 3,409 6,676 6,083 Implants sold direct subject to third-party reimbursement (d) 281 297 603 580 Biopsy kits - direct bill 557 468 1,099 904 Change in estimates related to prior periods 87 (51 ) 50 (189 ) Epicel Direct bill (hospital) 5,328 4,886 10,555 10,858 Total revenue $ 26,151 $ 19,011 $ 47,961 $ 37,038 (a) Represents implants sold through Orsini or AllCare in which such specialty pharmacy has entered into a direct contract with the underlying insurance provider. The amount of reimbursement is known at the time of sale supported by the pharmacy's direct contract. (b) Represents implants sold through Orsini or AllCare 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 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 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 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 customers of MACI and Epicel, as follows: Revenue Concentration Accounts Receivable Concentration Three Months Ended June 30, Six Months Ended June 30, June 30, December 31, 2019 2018 2019 2018 2019 2018 MACI 7 % 39 % 7 % 41 % 7 % 8 % Epicel 6 % 9 % 8 % 12 % 3 % 4 %

Selected Balance Sheet Componen

Selected Balance Sheet Components	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Selected Balance Sheet Components	Selected Balance Sheet Components Inventory as of June 30, 2019 and December 31, 2018 : (In thousands) June 30, 2019 December 31, 2018 Raw materials $ 4,127 $ 2,872 Work-in-process 596 638 Finished goods 65 48 Inventory $ 4,788 $ 3,558 Property and equipment, net as of June 30, 2019 and December 31, 2018 : (In thousands) June 30, 2019 December 31, 2018 Machinery and equipment $ 2,456 $ 1,536 Furniture, fixtures and office equipment 775 775 Computer equipment and software 5,906 3,712 Leasehold improvements 4,631 4,587 Construction in process 1,230 2,801 Financing right-of-use lease 166 — Total property and equipment, gross 15,164 13,411 Less: Accumulated depreciation (8,201 ) (7,505 ) $ 6,963 $ 5,906 Depreciation expense for the three and six months ended June 30, 2019 was $0.4 million and $0.7 million and $0.4 million and $0.8 million for the same period in 2018. Accrued expenses as of June 30, 2019 and December 31, 2018 : (In thousands) June 30, 2019 December 31, 2018 Bonus related compensation $ 1,528 $ 5,161 Employee related accruals 2,695 1,559 Other accrued expenses 478 210 $ 4,701 $ 6,930

Stock Purchase Warrants

Stock Purchase Warrants	6 Months Ended
	Jun. 30, 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 and in December 2017 the Company issued warrants in connection with a previous loan agreement. The following table describes the outstanding warrants classified in equity as of June 30, 2019 : December 2017 Warrants Exercise price $4.27 Expiration date December 6, 2023 Total shares issuable on exercise 26,951 The fair value of the warrants described in the table above were initially 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 remaining at zero .

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	Leases The Company leases facilities in Ann Arbor, Michigan and Cambridge, Massachusetts. 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 six months ended June 30, 2019 , lease expense of less than $0.1 million was recorded related to short-term leases for both the three and six months ended June 30, 2019 . 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 both the three and six months ended June 30, 2019 and for the same periods ending June 30, 2018 (as reported under the prior leasing guidance), the Company recognized $1.3 million and $2.6 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 June 30, 2019 are as follows: (In thousands) Classification June 30, 2019 Assets Operating Right-of-use assets $ 24,815 Finance Property and equipment, net 166 $ 24,981 Liabilities Current Operating Current portion of operating lease liabilities 2,558 Finance Other liabilities 34 $ 2,592 Non-current Operating Operating lease liabilities 24,607 Finance Other long-term liabilities 134 $ 24,741 Cash paid for amounts included in the measurement of the Company's operating lease liabilities was $2.5 million for the six months ended June 30, 2019 . Maturity of lease liabilities as of June 30, 2019 are as follows: (In thousands) Operating Leases Finance Leases Total 2019 $ 2,504 $ 21 $ 2,525 2020 4,944 41 4,985 2021 4,864 41 4,905 2022 4,929 41 4,970 2023 4,901 41 4,942 2024 4,968 — 4,968 Thereafter 11,269 — 11,269 Total lease payments 38,379 185 38,564 Less: Interest (11,214 ) (17 ) (11,231 ) Present value of lease liabilities $ 27,165 $ 168 $ 27,333 An explicit rate is not provided for 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 June 30, 2019 are as follows: June 30, 2019 Weighted average remaining lease term (years) Operating leases 7.26 Finance leases 4.01 Weighted average discount rate Operating leases 9.53 % 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 $ —
Leases	Leases The Company leases facilities in Ann Arbor, Michigan and Cambridge, Massachusetts. 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 six months ended June 30, 2019 , lease expense of less than $0.1 million was recorded related to short-term leases for both the three and six months ended June 30, 2019 . 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 both the three and six months ended June 30, 2019 and for the same periods ending June 30, 2018 (as reported under the prior leasing guidance), the Company recognized $1.3 million and $2.6 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 June 30, 2019 are as follows: (In thousands) Classification June 30, 2019 Assets Operating Right-of-use assets $ 24,815 Finance Property and equipment, net 166 $ 24,981 Liabilities Current Operating Current portion of operating lease liabilities 2,558 Finance Other liabilities 34 $ 2,592 Non-current Operating Operating lease liabilities 24,607 Finance Other long-term liabilities 134 $ 24,741 Cash paid for amounts included in the measurement of the Company's operating lease liabilities was $2.5 million for the six months ended June 30, 2019 . Maturity of lease liabilities as of June 30, 2019 are as follows: (In thousands) Operating Leases Finance Leases Total 2019 $ 2,504 $ 21 $ 2,525 2020 4,944 41 4,985 2021 4,864 41 4,905 2022 4,929 41 4,970 2023 4,901 41 4,942 2024 4,968 — 4,968 Thereafter 11,269 — 11,269 Total lease payments 38,379 185 38,564 Less: Interest (11,214 ) (17 ) (11,231 ) Present value of lease liabilities $ 27,165 $ 168 $ 27,333 An explicit rate is not provided for 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 June 30, 2019 are as follows: June 30, 2019 Weighted average remaining lease term (years) Operating leases 7.26 Finance leases 4.01 Weighted average discount rate Operating leases 9.53 % 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 $ —

Stock-based Compensation

Stock-based Compensation	6 Months Ended
	Jun. 30, 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 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. For certain non-employee consultants, stock option awards continue to vest post-termination. The guidance for non-employee stock compensation accounting for equity-classified awards was updated, and these awards are now subject to fixed grant date fair value principles which eliminates the variable mark-to-market accounting. The options were valued as of the adoption date of July 1, 2018. 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 awards 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 June 30, 2019 , there were 3,517,347 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 558,977 have been issued since the inception of the plan 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. On July 1, 2019, employees purchased 18,729 shares resulting in proceeds from the sale of common stock of $0.3 million under the ESPP. Service-Based Stock Options During the three and six months ended June 30, 2019 , the Company granted 152,500 and 1,638,510 service-based options to purchase common stock. The options have an exercise price equal to the fair market value per share of common stock on the grant date, generally vest over four years (other than 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 under the 2017 and 2019 Plans for the three and six month periods ended June 30, 2019 was $11.94 and $12.74 , respectively and $9.26 and $6.85 , respectively, for the same periods in 2018. Restricted Stock Units During the three and six months ended June 30, 2019 , the Company granted 10,500 and 186,922 service-based 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 weighted average grant-date fair value of restricted stock units awarded for the three and six month periods ended June 30, 2019 was $16.62 and $17.71 . The total grant-date fair value of restricted stock units granted in the six months ended June 30, 2019 was $3.3 million. No restricted stock units were granted in 2018. 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: Three Months Ended June 30, Six Months Ended June 30, (In thousands) 2019 2018 2019 2018 Cost of goods sold $ 716 $ 394 $ 976 $ 536 Research and development 886 442 1,410 917 Selling, general and administrative 2,581 1,629 4,424 2,354 Total non-cash stock-based compensation expense $ 4,183 $ 2,465 $ 6,810 $ 3,807 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. Six Months Ended June 30, Service-Based Stock Options 2019 2018 Expected dividend rate — % — % Expected stock price volatility 79.5-85.5% 82.3-88.3% Risk-free interest rate 1.9-2.7% 2.4-2.9% Expected life (years) 5.3-6.3 5.2-6.3

Cash Equivalents and Investment

Cash Equivalents and Investments	6 Months Ended
	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Cash Equivalents and Investments	Cash Equivalents and Investments Marketable debt securities 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 June 30, 2019 and December 31, 2018: June 30, 2019 Gross Unrealized (In thousands) Amortized Cost Gains Losses Fair Value Money market funds $ 4,831 $ — $ — $ 4,831 Commercial paper 17,149 — — 17,149 Corporate notes 17,225 20 — 17,245 U.S. government securities 6,955 11 — 6,966 U.S. asset-backed securities 10,680 7 — 10,687 $ 56,840 $ 38 $ — $ 56,878 Classified as: Cash equivalents $ 4,831 Short-term investments 52,047 $ 56,878 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 At December 31, 2018, the Company invested $5.0 million in overnight repurchase agreement securities classified as cash equivalents on the balance sheet. As of June 30, 2019 , no amounts were invested in overnight repurchase agreements. There were no marketable securities that the Company considers to be other-than-temporarily impaired as of June 30, 2019 . The Company's investment strategy is to buy short-duration marketable securities with a high credit rating. As of June 30, 2019 , all marketable securities held by the Company had remaining contractual maturities of one year 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 statements of operations. There have been no impairments of the Company’s assets measured and carried at fair value during the six months ended June 30, 2019 .

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 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; and • 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 from December 31, 2018 to June 30, 2019. 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: June 30, 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 $ 4,831 $ 4,831 $ — $ — $ 5,838 $ 5,838 $ — $ — Repurchase agreements — — — — 5,000 — 5,000 — Commercial paper 17,149 — 17,149 — 30,710 — 30,710 — Corporate notes 17,245 — 17,245 — 13,144 — 13,144 — U.S. government securities 6,966 — 6,966 — 10,166 — 10,166 — U.S. asset-backed securities 10,687 — 10,687 — 10,618 — 10,618 — $ 56,878 $ 4,831 $ 52,047 $ — $ 75,476 $ 5,838 $ 69,638 $ —

Net Loss Per Common Share

Net Loss Per Common Share	6 Months Ended
	Jun. 30, 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: Three Months Ended June 30, Six Months Ended June 30, (Amounts in thousands except per share amounts) 2019 2018 2019 2018 Numerator: Net loss $ (19,792 ) $ (4,651 ) (22,636 ) $ (12,310 ) Denominator for basic and diluted EPS: Weighted-average common shares outstanding 43,956 38,349 43,841 37,251 Net loss per share attributable to common shareholders (basic and diluted) $ (0.45 ) (0.12 ) $ (0.52 ) (0.33 ) Common equivalent shares are not included in the diluted per share calculation where the effect of their inclusion would be anti-dilutive. The number of common equivalent shares of options of 5.6 million , restricted stock unit awards of 0.2 million and less than 0.1 million of warrants have been excluded from the computations of diluted net loss per common share at June 30, 2019 and 2018 . The number of common equivalent shares of options of 5.4 million and 0.4 million of warrants have been excluded from the computations of diluted net loss per common share at June 30, 2018 .

Nexobrid License and Supply Agr

Nexobrid License and Supply Agreements	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Abstract]
Nexobrid License Agreement	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 three months ended June 30, 2019 as the license is for registration-stage product rights and 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 high single-digit to low double-digit 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.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies The Company leases facilities in Ann Arbor, Michigan and Cambridge, Massachusetts. The Cambridge facility includes clean rooms, laboratories for MACI and Epicel manufacturing and office space. The Company also pays for use of an offsite warehouse space and leases various vehicles and computer equipment. In March 2016, the Company amended its current lease in Cambridge to, among other provisions, extend the term until February 2022. Under the amendment, the landlord will contribute approximately $2.0 million toward the cost of tenant improvements. The contribution toward the cost of tenant improvements is recorded as part of the operating lease assets under the new leasing guidance described below, on the Company's condensed consolidated balance sheet. As of June 30, 2019 , the Company has recorded $1.9 million of leasehold improvements funded by the tenant improvement allowance . The Company adopted the updated leasing guidance as described in note 7, as of January 1, 2019. 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 lease expense is recorded on a straight-line basis over the lease term. 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.

Recent Accounting Pronounceme_2

Recent Accounting Pronouncements - (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Accounting for Leases	Accounting for Leases The 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 leasing Accounting Standard Update 2016-02, 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	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. The guidance is effective for annual reporting periods beginning after December 15, 2019. The Company is currently in the process of evaluating the impact to its consolidated financial statements.

Basis of Presentation - (Tables

Basis of Presentation - (Tables)	6 Months Ended
	Jun. 30, 2019
Basis of Presentation [Abstract]
Schedule of cash flow, supplemental disclosures	The following table presents certain supplementary cash flows information for the six months ended June 30, 2019 and 2018 : Six Months Ended June 30, (In thousands) 2019 2018 Supplementary Cash Flows information: Warrants exercised for common stock $ — $ 2,409 Interest paid (net of interest capitalized) 4 754 Additions to equipment in process included in accounts payable 365 459 Right-of-use asset and lease liability recognized 560 —

Revenue - (Tables)

Revenue - (Tables)	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Schedule of revenue by product and customer	The following table and description below reflect the products from which the Company generated its revenue: Three Months Ended June 30, Six Months Ended June 30, Revenue by product (in thousands) 2019 2018 2019 2018 MACI implants and kits Implants based on contracted rate sold through a specialty pharmacy (a) $ 12,989 $ 7,363 $ 22,776 $ 15,155 Implants subject to third-party reimbursement sold through a specialty pharmacy (b) 3,459 2,639 6,202 3,647 Implants sold direct based on contracted rates (c) 3,450 3,409 6,676 6,083 Implants sold direct subject to third-party reimbursement (d) 281 297 603 580 Biopsy kits - direct bill 557 468 1,099 904 Change in estimates related to prior periods 87 (51 ) 50 (189 ) Epicel Direct bill (hospital) 5,328 4,886 10,555 10,858 Total revenue $ 26,151 $ 19,011 $ 47,961 $ 37,038 (a) Represents implants sold through Orsini or AllCare in which such specialty pharmacy has entered into a direct contract with the underlying insurance provider. The amount of reimbursement is known at the time of sale supported by the pharmacy's direct contract. (b) Represents implants sold through Orsini or AllCare 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	's total revenue and accounts receivable balances were comprised of the following concentrations from its largest customers of MACI and Epicel, as follows: Revenue Concentration Accounts Receivable Concentration Three Months Ended June 30, Six Months Ended June 30, June 30, December 31, 2019 2018 2019 2018 2019 2018 MACI 7 % 39 % 7 % 41 % 7 % 8 % Epicel 6 % 9 % 8 % 12 % 3 % 4 %

Selected Balance Sheet Compon_2

Selected Balance Sheet Components - (Tables)	6 Months Ended
	Jun. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Schedule of inventory	Inventory as of June 30, 2019 and December 31, 2018 : (In thousands) June 30, 2019 December 31, 2018 Raw materials $ 4,127 $ 2,872 Work-in-process 596 638 Finished goods 65 48 Inventory $ 4,788 $ 3,558
Schedule of property and equipment, net	Property and equipment, net as of June 30, 2019 and December 31, 2018 : (In thousands) June 30, 2019 December 31, 2018 Machinery and equipment $ 2,456 $ 1,536 Furniture, fixtures and office equipment 775 775 Computer equipment and software 5,906 3,712 Leasehold improvements 4,631 4,587 Construction in process 1,230 2,801 Financing right-of-use lease 166 — Total property and equipment, gross 15,164 13,411 Less: Accumulated depreciation (8,201 ) (7,505 ) $ 6,963 $ 5,906 Depreciation expense for the three and six months ended June 30, 2019 was $0.4 million and $0.7 million and $0.4 million and $0.8 million for the same period in 2018.
Schedule of accounts payable and accrued expenses	Accrued expenses as of June 30, 2019 and December 31, 2018 : (In thousands) June 30, 2019 December 31, 2018 Bonus related compensation $ 1,528 $ 5,161 Employee related accruals 2,695 1,559 Other accrued expenses 478 210 $ 4,701 $ 6,930

Stock Purchase Warrants - (Tabl

Stock Purchase Warrants - (Tables)	6 Months Ended
	Jun. 30, 2019
Warrants and Rights Note Disclosure [Abstract]
Schedule of warrants outstanding	The following table describes the outstanding warrants classified in equity as of June 30, 2019 : December 2017 Warrants Exercise price $4.27 Expiration date December 6, 2023 Total shares issuable on exercise 26,951

Leases - (Tables)

Leases - (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2019 are as follows: (In thousands) Classification June 30, 2019 Assets Operating Right-of-use assets $ 24,815 Finance Property and equipment, net 166 $ 24,981 Liabilities Current Operating Current portion of operating lease liabilities 2,558 Finance Other liabilities 34 $ 2,592 Non-current Operating Operating lease liabilities 24,607 Finance Other long-term liabilities 134 $ 24,741
Maturity of lease liabilities	Maturity of lease liabilities as of June 30, 2019 are as follows: (In thousands) Operating Leases Finance Leases Total 2019 $ 2,504 $ 21 $ 2,525 2020 4,944 41 4,985 2021 4,864 41 4,905 2022 4,929 41 4,970 2023 4,901 41 4,942 2024 4,968 — 4,968 Thereafter 11,269 — 11,269 Total lease payments 38,379 185 38,564 Less: Interest (11,214 ) (17 ) (11,231 ) Present value of lease liabilities $ 27,165 $ 168 $ 27,333
Maturity of lease liabilities	Maturity of lease liabilities as of June 30, 2019 are as follows: (In thousands) Operating Leases Finance Leases Total 2019 $ 2,504 $ 21 $ 2,525 2020 4,944 41 4,985 2021 4,864 41 4,905 2022 4,929 41 4,970 2023 4,901 41 4,942 2024 4,968 — 4,968 Thereafter 11,269 — 11,269 Total lease payments 38,379 185 38,564 Less: Interest (11,214 ) (17 ) (11,231 ) Present value of lease liabilities $ 27,165 $ 168 $ 27,333
Lease term and discount rate	Lease terms and discount rates as of June 30, 2019 are as follows: June 30, 2019 Weighted average remaining lease term (years) Operating leases 7.26 Finance leases 4.01 Weighted average discount rate Operating leases 9.53 % Finance leases 5.00 %
Schedule Of Future Minimum Rental Payments For 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 $ —

Stock-based Compensation - (Tab

Stock-based Compensation - (Tables)	6 Months Ended
	Jun. 30, 2019
Share-based Payment Arrangement [Abstract]
Schedule of non-cash stock-based 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: Three Months Ended June 30, Six Months Ended June 30, (In thousands) 2019 2018 2019 2018 Cost of goods sold $ 716 $ 394 $ 976 $ 536 Research and development 886 442 1,410 917 Selling, general and administrative 2,581 1,629 4,424 2,354 Total non-cash stock-based compensation expense $ 4,183 $ 2,465 $ 6,810 $ 3,807
Schedule of weighted average assumptions used to estimate fair value of each service-based stock option grant	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. Six Months Ended June 30, Service-Based Stock Options 2019 2018 Expected dividend rate — % — % Expected stock price volatility 79.5-85.5% 82.3-88.3% Risk-free interest rate 1.9-2.7% 2.4-2.9% Expected life (years) 5.3-6.3 5.2-6.3

Cash Equivalents and Investme_2

Cash Equivalents and Investments - (Tables)	6 Months Ended
	Jun. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Schedule of fair value of securities, not including cash	The following tables summarize the gross unrealized gains and losses of the Company’s marketable securities as of June 30, 2019 and December 31, 2018: June 30, 2019 Gross Unrealized (In thousands) Amortized Cost Gains Losses Fair Value Money market funds $ 4,831 $ — $ — $ 4,831 Commercial paper 17,149 — — 17,149 Corporate notes 17,225 20 — 17,245 U.S. government securities 6,955 11 — 6,966 U.S. asset-backed securities 10,680 7 — 10,687 $ 56,840 $ 38 $ — $ 56,878 Classified as: Cash equivalents $ 4,831 Short-term investments 52,047 $ 56,878 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

Fair Value Measurements - (Tabl

Fair Value Measurements - (Tables)	6 Months Ended
	Jun. 30, 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: June 30, 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 $ 4,831 $ 4,831 $ — $ — $ 5,838 $ 5,838 $ — $ — Repurchase agreements — — — — 5,000 — 5,000 — Commercial paper 17,149 — 17,149 — 30,710 — 30,710 — Corporate notes 17,245 — 17,245 — 13,144 — 13,144 — U.S. government securities 6,966 — 6,966 — 10,166 — 10,166 — U.S. asset-backed securities 10,687 — 10,687 — 10,618 — 10,618 — $ 56,878 $ 4,831 $ 52,047 $ — $ 75,476 $ 5,838 $ 69,638 $ —

Net Loss Per Common Share - (Ta

Net Loss Per Common Share - (Tables)	6 Months Ended
	Jun. 30, 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: Three Months Ended June 30, Six Months Ended June 30, (Amounts in thousands except per share amounts) 2019 2018 2019 2018 Numerator: Net loss $ (19,792 ) $ (4,651 ) (22,636 ) $ (12,310 ) Denominator for basic and diluted EPS: Weighted-average common shares outstanding 43,956 38,349 43,841 37,251 Net loss per share attributable to common shareholders (basic and diluted) $ (0.45 ) (0.12 ) $ (0.52 ) (0.33 )

Organization - Narrative (Detai

Organization - Narrative (Details) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Jun. 30, 2019USD ($)segment	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | segment					1
Accumulated deficit	$ 391,650				$ 391,650		$ 369,014
Net loss	19,792	$ 2,844	$ 4,651	$ 7,659	22,636	$ 12,310
Cash and cash equivalents	13,962				13,962		18,286
Short-term investments	$ 52,047				$ 52,047		$ 64,638

Basis of Presentation - Narrati

Basis of Presentation - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Basis of Presentation [Abstract]
Warrants exercised for common stock	$ 0	$ 2,409
Interest paid (net of interest capitalized)	4	754
Additions to equipment in process included in accounts payable	365	459
Right-of-use asset and lease liability recognized	$ 560	$ 0

Revenue - Revenue by product an

Revenue - Revenue by product and customer (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Product sales, net	$ 26,151	$ 19,011	$ 47,961	$ 37,038
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Disaggregation of Revenue [Line Items]
Product sales, net	87	(51)	50	(189)
Implants | Contracted rate | Third party distributor
Disaggregation of Revenue [Line Items]
Product sales, net	12,989	7,363	22,776	15,155
Implants | Contracted rate | Provider or Facility
Disaggregation of Revenue [Line Items]
Product sales, net	3,450	3,409	6,676	6,083
Implants | Time-and-materials Contract | Third party distributor
Disaggregation of Revenue [Line Items]
Product sales, net	3,459	2,639	6,202	3,647
Implants | Time-and-materials Contract | Time-and-materials Contract
Disaggregation of Revenue [Line Items]
Product sales, net	281	297	603	580
Biopsy kits | Direct bill
Disaggregation of Revenue [Line Items]
Product sales, net	557	468	1,099	904
Epicel | Direct bill
Disaggregation of Revenue [Line Items]
Product sales, net	$ 5,328	$ 4,886	$ 10,555	$ 10,858

Revenue - Concentration of Cred

Revenue - Concentration of Credit Risk (Details) - Customer concentration	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
MACI | Revenue Concentration
CONCENTRATION
Concentration risk	7.00%	39.00%	7.00%	41.00%
MACI | Accounts Receivable Concentration
CONCENTRATION
Concentration risk			7.00%		8.00%
Epicel | Revenue Concentration
CONCENTRATION
Concentration risk	6.00%	9.00%	8.00%	12.00%
Epicel | Accounts Receivable Concentration
CONCENTRATION
Concentration risk			3.00%		4.00%

Selected Balance Sheet Compon_3

Selected Balance Sheet Components - Inventory (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Inventory:
Raw materials	$ 4,127	$ 2,872
Work-in-process	596	638
Finished goods	65	48
Inventory	$ 4,788	$ 3,558

Selected Balance Sheet Compon_4

Selected Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Property and equipment, net:
Total property and equipment, gross	$ 15,164		$ 15,164		$ 13,411
Finance	166		166		0
Less: Accumulated depreciation	(8,201)		(8,201)		(7,505)
Total, net	6,963		6,963		5,906
Depreciation and amortization	400	$ 400	700	$ 800
Machinery and equipment
Property and equipment, net:
Total property and equipment, gross	2,456		2,456		1,536
Furniture, fixtures and office equipment
Property and equipment, net:
Total property and equipment, gross	775		775		775
Computer equipment and software
Property and equipment, net:
Total property and equipment, gross	5,906		5,906		3,712
Leasehold improvements
Property and equipment, net:
Total property and equipment, gross	4,631		4,631		4,587
Construction in process
Property and equipment, net:
Total property and equipment, gross	$ 1,230		$ 1,230		$ 2,801

Selected Balance Sheet Compon_5

Selected Balance Sheet Components - Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accounts payable and accrued expenses:
Bonus related compensation	$ 1,528	$ 5,161
Employee related accruals	2,695	1,559
Other accrued expenses	478	210
Total	$ 4,701	$ 6,930

Stock Purchase Warrants - Narra

Stock Purchase Warrants - Narrative (Details)	Jun. 30, 2019$ / sharesshares
Measurement Input, Expected Dividend Rate
Stock Purchase Warrants
Warrants and Rights Outstanding ( as a percent )	0
December 2017 Warrants
Stock Purchase Warrants
Exercise price (in dollars per share) | $ / shares	$ 4.27
Total shares issuable on exercise (in shares) | shares	26,951

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Jan. 01, 2019
Leases [Abstract]
Measurement of Lease Liability		$ 2,500
Short-term lease cost	$ 100	100
Net Lease Assets	24,981	24,981		$ 25,600
Lease Liability	27,333	27,333		$ 27,800
Operating Lease Expense	1,300	$ 2,600
Finance lease expense	$ 100
Capital Leases Expense			$ 2,600

Leases - Assets And Liabilities

Leases - Assets And Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
ASSETS
Right-of-use assets	$ 24,815		$ 0
Finance	166		0
Right Of Use Asset	24,981	$ 25,600
Current liabilities:
Operating	2,558		0
Finance	34
Lease Liability Current	2,592
Non-current
Operating	24,607		$ 0
Finance	134
Lease Liability Noncurrent	$ 24,741

Leases - Maturities of lease li

Leases - Maturities of lease liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
Operating Leases
2019	$ 2,504
2020	4,944
2021	4,864
2022	4,929
2023	4,901
2024	4,968
Thereafter	11,269
Total lease payments	38,379
Less: Interest	(11,214)
Present value of lease liabilities	27,165
Finance Leases
2019	21
2020	41
2021	41
2022	41
2023	41
2024	0
Thereafter	0
Total lease payments	185
Less: Interest	(17)
Present value of lease liabilities	168
2019	2,525
2020	4,985
2021	4,905
2022	4,970
2023	4,942
2024	4,968
Thereafter	11,269
Total lease payments	38,564
Less: Interest	(11,231)
Present value of lease liabilities	$ 27,333	$ 27,800

Leases - Lease term and discoun

Leases - Lease term and discount rate (Details)	Jun. 30, 2019
Leases [Abstract]
Operating Lease Term (in years)	7 years 3 months 3 days
Finance Lease Term (in years)	4 years 3 days
Operating Lease Discount Rate ( as a percent )	9.53%
Finance Lease Discount Rate ( as a percent )	5.00%

Leases - Schedule Prior To Adop

Leases - Schedule Prior To Adoption (Details) $ in Thousands	Dec. 31, 2018USD ($)
Operating leases
Total	$ 15,386
2019	4,879
2020	4,719
2021	4,754
2022	966
2023	68
More than 5 years	0
Capital leases
Total	205
2019	41
2020	41
2021	41
2022	41
2023	41
More than 5 years	0
Operating And Capital Leases [Abstract]
Total	15,591
2019	4,920
2020	4,760
2021	4,795
2022	1,007
2023	109
More than 5 years	$ 0

Stock-based Compensation - Narr

Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	Jul. 01, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2018
Stock-Based Compensation
Shares issued under the Employee Stock Purchase Plan		$ 211	$ 218	$ 148	$ 127
2004, 2001, 1992, and 2009 Plans
Stock-Based Compensation
Number of shares available for grant (in shares)		0				0
2017 Plan
Stock-Based Compensation
Number of shares available for grant (in shares)		3,517,347				3,517,347
Service-Based Stock Options
Stock-Based Compensation
Expiration period						10 years
Vesting period						4 years
Granted (in shares)		152,500				1,638,510
Grant date fair value (in dollars per share)		$ 11.94		$ 9.26		$ 12.74	$ 6.85
Restricted Stock or Unit Expense						$ 3,300
Service-Based Stock Options | Maximum
Stock-Based Compensation
Expiration period						10 years
Restricted Stock Units (RSUs)
Stock-Based Compensation
Granted (in shares)		10,500				186,922
Grant date fair value (in dollars per share)		$ 16.62				$ 17.71
Employee Stock
Stock-Based Compensation
Employee Stock Purchase Plan, number of shares authorized (in shares)		1,000,000				1,000,000
Employee Stock Purchase Plan, grants since inception (in shares)								558,977
Subsequent Event | Employee Stock
Stock-Based Compensation
Shares issued under the Employee Stock Purchase Plan ( in shares )	18,729
Shares issued under the Employee Stock Purchase Plan	$ 300

Stock-based Compensation - Non-

Stock-based Compensation - Non-cash Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-cash stock-based compensation expense	$ 4,183	$ 2,465	$ 6,810	$ 3,807
Cost of goods sold
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-cash stock-based compensation expense	716	394	976	536
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-cash stock-based compensation expense	886	442	1,410	917
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-cash stock-based compensation expense	$ 2,581	$ 1,629	$ 4,424	$ 2,354

Stock-based Compensation - Weig

Stock-based Compensation - Weighted average assumptions used to estimate fair value (Details) - Service-Based Stock Options	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Stock-Based Compensation
Expected dividend rate	0.00%	0.00%
Minimum
Stock-Based Compensation
Expected stock price volatility	79.50%	82.30%
Risk-free interest rate	1.90%	2.40%
Expected life	5 years 3 months 18 days	5 years 2 months 12 days
Maximum
Stock-Based Compensation
Expected stock price volatility	85.50%	88.30%
Risk-free interest rate	2.70%	2.90%
Expected life	6 years 3 months 18 days	6 years 3 months 18 days

Cash Equivalents and Investme_3

Cash Equivalents and Investments - Schedule of Fair Value of Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 56,840	$ 75,515
Gains	38	0
Losses	0	(39)
Fair Value	56,878	75,476
Cash equivalents
Debt Securities, Available-for-sale [Line Items]
Fair Value	4,831	10,838
Short-term investments
Debt Securities, Available-for-sale [Line Items]
Fair Value	52,047	64,638
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,831	5,838
Gains	0	0
Losses	0	0
Fair Value	4,831	5,838
Repurchase agreements
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		5,000
Gains		0
Losses		0
Fair Value		5,000
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	17,149	30,710
Gains	0	0
Losses	0	0
Fair Value	17,149	30,710
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	17,225	13,168
Gains	20	0
Losses	0	(24)
Fair Value	17,245	13,144
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,955	10,167
Gains	11	0
Losses	0	(1)
Fair Value	6,966	10,166
U.S. asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	10,680	10,632
Gains	7	0
Losses	0	(14)
Fair Value	$ 10,687	$ 10,618

Cash Equivalents and Investme_4

Cash Equivalents and Investments - Narrative (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)
Repurchase agreements
Debt Securities, Available-for-sale [Line Items]
Payments to acquire investment funds and securities	$ 5

Fair Value Measurements - Recur

Fair Value Measurements - Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Assets:
Assets, fair value	$ 56,878	$ 75,476
Level 1
Assets:
Assets, fair value	4,831	5,838
Level 2
Assets:
Assets, fair value	52,047	69,638
Level 3
Assets:
Assets, fair value	0	0
Money market funds
Assets:
Assets, fair value	4,831	5,838
Money market funds | Level 1
Assets:
Assets, fair value	4,831	5,838
Money market funds | Level 2
Assets:
Assets, fair value	0	0
Money market funds | Level 3
Assets:
Assets, fair value	0	0
Repurchase agreements
Assets:
Assets, fair value	0	5,000
Repurchase agreements | Level 1
Assets:
Assets, fair value	0	0
Repurchase agreements | Level 2
Assets:
Assets, fair value	0	5,000
Repurchase agreements | Level 3
Assets:
Assets, fair value	0	0
Commercial paper
Assets:
Assets, fair value	17,149	30,710
Commercial paper | Level 1
Assets:
Assets, fair value	0	0
Commercial paper | Level 2
Assets:
Assets, fair value	17,149	30,710
Commercial paper | Level 3
Assets:
Assets, fair value	0	0
Corporate notes
Assets:
Assets, fair value	17,245	13,144
Corporate notes | Level 1
Assets:
Assets, fair value	0	0
Corporate notes | Level 2
Assets:
Assets, fair value	17,245	13,144
Corporate notes | Level 3
Assets:
Assets, fair value	0	0
U.S. government securities
Assets:
Assets, fair value	6,966	10,166
U.S. government securities | Level 1
Assets:
Assets, fair value	0	0
U.S. government securities | Level 2
Assets:
Assets, fair value	6,966	10,166
U.S. government securities | Level 3
Assets:
Assets, fair value	0	0
U.S. asset-backed securities
Assets:
Assets, fair value	10,687	10,618
U.S. asset-backed securities | Level 1
Assets:
Assets, fair value	0	0
U.S. asset-backed securities | Level 2
Assets:
Assets, fair value	10,687	10,618
U.S. asset-backed securities | Level 3
Assets:
Assets, fair value	$ 0	$ 0

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				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net loss	$ (19,792)	$ (2,844)	$ (4,651)	$ (7,659)	$ (22,636)	$ (12,310)
Denominator for basic and diluted EPS:
Weighted-average common shares outstanding (in shares)	43,956		38,349		43,841	37,251
Net loss per share attributable to common shareholders (basic and diluted) (in dollars per share)	$ (0.45)		$ (0.12)		$ (0.52)	$ (0.33)
Options
Denominator for basic and diluted EPS:
Aggregate number of common equivalent shares (related to options, warrants and preferred stock) excluded from diluted net loss per common share (in shares)					5,600	5,400
Restricted Stock
Denominator for basic and diluted EPS:
Aggregate number of common equivalent shares (related to options, warrants and preferred stock) excluded from diluted net loss per common share (in shares)					200
Warrants Amounts
Denominator for basic and diluted EPS:
Aggregate number of common equivalent shares (related to options, warrants and preferred stock) excluded from diluted net loss per common share (in shares)					100	400

Nexobrid License and Supply A_2

Nexobrid License and Supply Agreements - Narrative (Details) - MediWound Ltd [Member]	May 31, 2019USD ($)
Related Party Transaction [Line Items]
Payable	$ 17,500,000
Contingent Consideration	7,500,000
Max contingent consideration	125,000,000
Sales Initial Milestone	$ 75,000,000

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	Jun. 30, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
Incentive from Lessor	$ 2
Deferred Rent Credit	$ 1.9