Flexion Therapeutics (FLXN) 10-Q 4 Aug 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 01, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Registrant Name	Flexion Therapeutics, Inc.
Entity Central Index Key	0001419600
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		50,292,110
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Title of 12(b) Security	Common stock, $0.001 par value per share
Trading Symbol	FLXN
Security Exchange Name	NASDAQ
Entity File Number	001-36287
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-1388364
Entity Address, Address Line One	10 Mall Road
Entity Address, Address Line Two	Suite 301
Entity Address, City or Town	Burlington
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01803
City Area Code	781
Local Phone Number	305-7777
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 107,629	$ 107,704
Marketable securities	23,620	67,576
Accounts receivable, net	35,097	30,025
Inventories	12,301	15,394
Prepaid expenses and other current assets	5,474	5,112
Total current assets	184,121	225,811
Property and equipment, net	19,783	19,538
Right-of-use assets	6,143	6,577
Total assets	210,047	251,926
Current liabilities
Accounts payable	5,474	6,928
Accrued expenses and other current liabilities	21,352	20,008
Deferred revenue	10,000	10,000
Operating lease liabilities	1,577	1,526
Current portion of long-term debt	1,528	16,806
Total current liabilities	39,931	55,268
Long-term operating lease liability, net	5,777	6,123
Long-term debt, net	52,207	44,114
2024 convertible notes, net	167,814	162,786
Other long-term liabilities	489	295
Total liabilities	266,218	268,586
Commitments and contingencies
Preferred stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2021 and December 31, 2020 and 0 shares issued and outstanding at June 30, 2021 and December 31, 2020	0	0
Stockholders' deficit
Common stock, $0.001 par value; 100,000,000 shares authorized; 50,105,620 and 49,403,034 shares issued and outstanding, at June 30, 2021 and December 31, 2020, respectively	50	49
Additional paid-in capital	776,850	765,607
Accumulated other comprehensive loss	(2)	(11)
Accumulated deficit	(833,069)	(782,305)
Total stockholders' deficit	(56,171)	(16,660)
Total liabilities and stockholders' deficit	$ 210,047	$ 251,926

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	50,105,620	50,105,620
Common stock, shares outstanding	49,403,034	49,403,034

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues
Product revenue, net	$ 28,175	$ 15,451	$ 52,764	$ 35,578
Type of Revenue [Extensible List]	Product [Member]	Product [Member]	Product [Member]	Product [Member]
Operating expenses
Cost of sales	$ 4,979	$ 5,481	$ 11,064	$ 7,757
Type of Cost, Good or Service [Extensible List]	Product [Member]	Product [Member]	Product [Member]	Product [Member]
Research and development	$ 12,669	$ 12,507	$ 26,716	$ 33,641
Selling, general and administrative	27,409	24,730	55,007	54,029
Total operating expenses	45,057	42,718	92,787	95,427
Loss from operations	(16,882)	(27,267)	(40,023)	(59,849)
Other (expense) income
Interest income	177	95	477	522
Interest expense	(5,180)	(5,002)	(10,369)	(9,723)
Other expense	(323)	(197)	(849)	(123)
Total other (expense) income	(5,326)	(5,104)	(10,741)	(9,324)
Loss before income taxes	(22,208)	(32,371)	(50,764)	(69,173)
Income tax expense	0	248	0	248
Net loss	$ (22,208)	$ (32,619)	$ (50,764)	$ (69,421)
Net loss per common share, basic and diluted	$ (0.44)	$ (0.76)	$ (1.02)	$ (1.71)
Weighted average common shares outstanding, basic and diluted	49,968	42,776	49,905	40,664
Other comprehensive income (loss):
Unrealized gains (losses) from available-for-sale securities, net of tax of $0	$ 8	$ (3)	$ 9	$ (59)
Total other comprehensive income (loss)	8	(3)	9	(59)
Comprehensive loss	$ (22,200)	$ (32,622)	$ (50,755)	$ (69,480)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Unrealized gains from available-for-sale securities, tax	$ 0	$ 0	$ 0	$ 0

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Changes in Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in-Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2019	$ (20,108)	$ 38	$ 648,391	$ 62	$ (668,599)
Balance (in shares) at Dec. 31, 2019		38,361,000
Issuance of common stock for equity awards, net of shares withheld for taxes	9	$ 1	8
Issuance of common stock for equity awards, net of shares withheld for taxes (in shares)		201,000
Stock-based compensation expense	4,651		4,651
Net loss	(36,802)				(36,802)
Other comprehensive income (loss)	(56)			(56)
Balance at Mar. 31, 2020	(52,306)	$ 39	653,050	6	(705,401)
Balance (in shares) at Mar. 31, 2020		38,562,000
Balance at Dec. 31, 2019	(20,108)	$ 38	648,391	62	(668,599)
Balance (in shares) at Dec. 31, 2019		38,361,000
Net loss	(69,421)
Other comprehensive income (loss)	(59)
Balance at Jun. 30, 2020	16,515	$ 49	754,483	3	(738,020)
Balance (in shares) at Jun. 30, 2020		49,270,000
Balance at Mar. 31, 2020	(52,306)	$ 39	653,050	6	(705,401)
Balance (in shares) at Mar. 31, 2020		38,562,000
Issuance of common stock, net of issuance costs	96,764	$ 10	96,754
Issuance of common stock net of issuance costs (in shares)		10,615,000
Issuance of common stock for equity awards, net of shares withheld for taxes	1		1
Issuance of common stock for equity awards, net of shares withheld for taxes (in shares)		11,000
Employee stock purchase plan	891		891
Employee stock purchase plan (in shares)		82,000
Stock-based compensation expense	3,787		3,787
Net loss	(32,619)				(32,619)
Other comprehensive income (loss)	(3)			(3)
Balance at Jun. 30, 2020	16,515	$ 49	754,483	3	(738,020)
Balance (in shares) at Jun. 30, 2020		49,270,000
Balance at Dec. 31, 2020	(16,660)	$ 49	765,607	(11)	(782,305)
Balance (in shares) at Dec. 31, 2020		49,403,000
Issuance of common stock, net of issuance costs	1,700		1,700
Issuance of common stock net of issuance costs (in shares)		134,000
Issuance of common stock for equity awards, net of shares withheld for taxes	8	$ 1	7
Issuance of common stock for equity awards, net of shares withheld for taxes (in shares)		405,000
Stock-based compensation expense	4,640		4,640
Net loss	(28,556)				(28,556)
Other comprehensive income (loss)	1			1
Balance at Mar. 31, 2021	(38,867)	$ 50	771,954	(10)	(810,861)
Balance (in shares) at Mar. 31, 2021		49,942,000
Balance at Dec. 31, 2020	(16,660)	$ 49	765,607	(11)	(782,305)
Balance (in shares) at Dec. 31, 2020		49,403,000
Net loss	(50,764)
Other comprehensive income (loss)	9
Balance at Jun. 30, 2021	(56,171)	$ 50	776,850	(2)	(833,069)
Balance (in shares) at Jun. 30, 2021		50,106,000
Balance at Mar. 31, 2021	(38,867)	$ 50	771,954	(10)	(810,861)
Balance (in shares) at Mar. 31, 2021		49,942,000
Issuance of common stock for equity awards, net of shares withheld for taxes (in shares)		46,000
Employee stock purchase plan	921		921
Employee stock purchase plan (in shares)		118,000
Stock-based compensation expense	3,975		3,975
Net loss	(22,208)				(22,208)
Other comprehensive income (loss)	8			8
Balance at Jun. 30, 2021	$ (56,171)	$ 50	$ 776,850	$ (2)	$ (833,069)
Balance (in shares) at Jun. 30, 2021		50,106,000

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net loss	$ (50,764)	$ (69,421)
Adjustments to reconcile net loss to cash used in operating activities
Depreciation	1,046	751
Amortization of right-of-use assets	867	809
Stock-based compensation expense	8,615	8,438
Provision for inventory	560	0
Non cash interest expense	454	292
Amortization (accretion) of premium (discount) on marketable securities	401	(52)
Loss on disposal of fixed assets	0	262
Amortization of debt discount and debt issuance costs	5,028	4,577
Premium paid on securities purchased	3	(17)
Changes in operating assets and liabilities:
Accounts receivable	(5,072)	15,591
Inventory	2,533	(2,502)
Prepaid expenses and other current assets	(362)	328
Accounts payable	(1,286)	(7,540)
Accrued expenses and other current liabilities	1,469	(4,375)
Deferred revenue	0	5,000
Lease liabilities	(728)	(748)
Net cash used in operating activities	(37,236)	(48,607)
Cash flows from investing activities
Purchases of property and equipment	(1,265)	(5,538)
Purchases of marketable securities	(2,000)	(12,490)
Sale and redemption of marketable securities	45,561	49,398
Net cash provided by investing activities	42,296	31,370
Cash flows from financing activities
Proceeds from borrowings under term loan	0	15,000
Proceeds from revolving line of credit	0	20,000
Repayments of revolving line of credit	0	(15,000)
Proceeds from the offering of common stock	0	97,289
Proceeds from issuance of common stock (net of issuance costs)	1,700	0
Payments of public offering costs	(125)	(107)
Payments on notes payable	(7,639)	0
Proceeds from the exercise of stock options (net of shares withheld for taxes)	8	10
Proceeds from employee stock purchase plan	921	891
Net cash (used in) provided by financing activities	(5,135)	118,083
Net (decrease) increase in cash and cash equivalents	(75)	100,846
Cash and cash equivalents at beginning of period	107,704	82,253
Cash and cash equivalents at end of period	107,629	183,099
Non-cash operating, investing and financing activities
Right-of-use asset obtained in exchange for operating lease obligation	433	0
Purchases of property and equipment in accounts payable and accrued expenses	264	2,126
Public offering costs in accounts payable and accrued expenses	0	418
Supplemental disclosures of cash flow information
Cash paid for interest	$ 5,259	$ 5,048

Overview and Nature of the Busi

Overview and Nature of the Business	6 Months Ended
	Jun. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Overview and Nature of the Business	1. Overview and Nature of the Business Flexion Therapeutics, Inc. (“Flexion” or the “Company”) was incorporated under the laws of the state of Delaware on November 5, 2007 . Flexion is a biopharmaceutical company focused on the discovery, development, and commercialization of novel, local therapies for the treatment of patients with musculoskeletal conditions, beginning with osteoarthritis, or OA, the most common form of arthritis. The Company has an approved product, ZILRETTA ® , which it markets in the United States. ZILRETTA is the first and only extended-release, intra-articular, or IA (meaning in the joint), injection indicated for the management of OA knee pain. ZILRETTA is a non-opioid therapy that employs Flexion’s proprietary microsphere technology to provide pain relief. The pivotal Phase 3 trial, on which the approval of ZILRETTA was based, showed that ZILRETTA met the primary endpoint of pain reduction at Week 12, with statistically significant pain relief extending through Week 16. The Company also has two pipeline programs focused on the local treatment of musculoskeletal conditions: FX201, an investigational IA gene therapy product candidate in clinical development for the treatment of OA, and FX301, a locally administered peripheral nerve block product candidate in clinical development for the control of post-operative pain. The Company is subject to risks and uncertainties common to companies in the biopharmaceutical industry, including, but not limited to, new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, and the ability to secure additional capital to fund operations. Successfully commercializing ZILRETTA requires significant sales and marketing efforts and the Company’s pipeline programs will require significant additional research and development efforts, including extensive preclinical and clinical testing. These activities will in turn require significant amounts of capital, qualified personnel, and adequate infrastructure. There can be no assurance as to when, if ever, the Company will generate sales of ZILRETTA that are significant enough to achieve profitability or if the development efforts supporting the Company’s pipeline, including future clinical trials, will be successful. The accompanying condensed consolidated financial statements have been prepared on a basis that assumes that the Company will continue as a going concern and that contemplates the realization of assets and satisfaction of liabilities and commitments in the normal course of business. The Company has incurred recurring losses and negative cash flows from operations. As of June 30, 2021, the Company had cash, cash equivalents, and marketable securities of approximately $ 131.2 million. Management believes that current cash, cash equivalents, and marketable securities on hand at June 30, 2021 will be sufficient to fund operations and debt obligations for at least the next 12 months from the issuance date of these financial statements. The Company currently expects to be able to maintain the liquidity threshold in the amended and restated credit agreement described in Note 9 for at least 12 months following the issuance of these financial statements. As a result, the revenue covenant under the amended and restated credit and security agreement is not expected to be applicable through 12 months from the issuance of the financial statements. As of June 30, 2021, the Company was in compliance with all financial covenants under the amended and restated credit and security agreement. The Company’s operations have been and continue to be affected by the ongoing global pandemic of a novel strain of coronavirus (“COVID-19”). In March 2020, the World Health Organization declared COVID-19 a pandemic and recommended containment and mitigation measures worldwide. The COVID-19 pandemic has caused significant volatility and uncertainty, which could result in a prolonged economic downturn that has disrupted and is expected to continue to disrupt the Company’s business. While there have been no material asset impairments recorded to date, any prolonged material future disruptions to the work of the Company’s employees, suppliers, contract manufacturers, or vendors, or to the operations of physicians that administer ZILRETTA could negatively impact the Company’s operations, availability of supplies, carrying value of assets, operating results, or cash flows. The future viability of the Company is dependent on its ability to fund its operations through sales of ZILRETTA, and/or raising additional capital, such as through debt or equity offerings, as needed. If the Company is unable to grow sales of ZILRETTA in future periods, it is possible that the Company may not maintain compliance with the revenue covenant, in the event it applies, in future periods. As a result, the Company could be required to repay its outstanding borrowings under the term loan and revolving credit facility and would seek additional financing. The Company may not be able to obtain financing on acceptable terms, or at all. In particular, as a result of the COVID-19 pandemic and actions taken to slow its spread, the global credit and financial markets have experienced extreme volatility and disruptions, including declines in consumer confidence, declines in economic growth, increases in unemployment rates, and uncertainty about economic stability. If the equity and credit markets deteriorate, it may make any additional debt or equity financing more difficult, more costly, and more dilutive. If the Company is unable to obtain funding on a timely basis, the Company may need to curtail its operations, including the commercialization of ZILRETTA, and/or reduce the scope of, or delay certain research and development activities, including the FX201 or FX301 programs, which could adversely affect its prospects.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial statements as of June 30, 2021, and for the three and six months ended June 30, 2021 and 2020, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and Generally Accepted Accounting Principles (“GAAP”) for consolidated financial information including the accounts of the Company and its wholly owned subsidiary after elimination of all significant intercompany accounts and transactions. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all adjustments that are necessary for a fair statement of the Company’s financial position and results of its operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K filed with the SEC on March 10, 2021. The information presented in the condensed consolidated financial statements and related notes as of June 30, 2021, and December 31, 2020, and for the three and six months ended June 30, 2021 and 2020, is unaudited. The December 31, 2020, condensed consolidated balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements. Interim results for the three and six months ended June 30, 2021 , are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2021, or any future period. Recent Accounting Pronouncements Accounting Standards Recently Issued In August 2020, the FASB issued ASU No. 2020-06, (“ASU 2020-06”). The new standard simplifies the accounting for certain financial instruments with characteristics of liabilities and equity. The new guidance reduced the number of accounting models for convertible debt and convertible preferred stock instruments and made certain disclosure amendments intended to improve the information provided to users. The guidance also amended the derivative guidance for the “own stock” scope exception, which exempts qualifying instruments from being accounted for as derivatives if certain criteria are met. Finally, the standard changed the way certain convertible instruments are treated when calculating earnings per share. The standard is effective for the Company for fiscal years, and the interim periods within those years, beginning after December 15, 2021, and early adoption is permitted. The Company is currently evaluating the impact of ASU 2020-06 on the Company’s condensed consolidated financial statements. Consolidation The accompanying condensed consolidated financial statements include the Company and its wholly owned subsidiary, Flexion Therapeutics Securities Corporation. The Company has eliminated all intercompany transactions for the three and six months ended June 30, 2021, and the year ended December 31, 2020 . Revenue Recognition On October 6, 2017, the U.S. Food and Drug Administration (“FDA”) approved ZILRETTA. The Company entered into a limited number of arrangements with specialty distributors and a specialty pharmacy in the U.S. to distribute ZILRETTA. The Company recognizes revenue in accordance with Accounting Standards Codification (“ASC”) Topic 606 - Revenue from Contracts with Customers (“Topic 606”). Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to be entitled to in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the 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 revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to arrangements that meet the definition of a contract with a customer under Topic 606, including when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Product Revenue, Net The Company primarily sells ZILRETTA to specialty distributors and a specialty pharmacy, who then subsequently resell ZILRETTA to physicians, clinics, and certain medical centers or hospitals. The Company also contracts directly with healthcare providers and intermediaries such as Group Purchasing Organizations (“GPOs”). In addition, the Company enters into arrangements with government payers that provide for government mandated rebates and chargebacks with respect to the purchase of ZILRETTA. The Company recognizes revenue on product sales when the customer obtains control of the Company’s product, which occurs at a point in time (upon delivery to the customer). The Company has determined that the delivery of ZILRETTA to its customers constitutes a single performance obligation. There are no other promises to deliver goods or services beyond what is specified in each accepted customer order. The Company has assessed the existence of a significant financing component in the agreements with its customers. The trade payment terms with customers do not exceed one year , and therefore the Company has elected to apply the practical expedient and no amount of consideration has been allocated as a financing component. Product revenues are recorded net of applicable reserves for variable consideration, including discounts and allowances. Transaction Price, including Variable Consideration Revenues from product sales are recorded at the net sales price (transaction price), which includes estimates of variable consideration for which reserves are established. Components of variable consideration include trade discounts and allowances, product returns, government chargebacks, discounts and rebates, and other incentives, such as voluntary patient assistance, and other fee-for-service amounts that are detailed within contracts between the Company and its customers relating to the Company’s sale of its products. These reserves, as detailed below, are based on the amounts earned, or to be claimed on the related sales, and are classified as reductions of accounts receivable (if the amount is payable to the customer) or a current liability (if the amount is payable to a party other than a customer). These estimates take into consideration a range of possible outcomes that are probability-weighted in accordance with the expected value method in Topic 606 for relevant factors such as current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the respective underlying contracts. The amount of variable consideration that is included in the transaction price may be constrained and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized under the contract will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s original estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. Service Fees and Allowances The Company compensates its customers and GPOs for sales order management, data, and distribution services. However, the Company has determined such services received to date are not distinct from the Company’s sale of products to the customer and, therefore, these payments have been recorded as a reduction of revenue within the statement of operations and comprehensive loss through June 30, 2021, as well as a reduction to trade receivables, net on the condensed consolidated balance sheets. Product Returns Consistent with industry practice, the Company generally offers customers a limited right of return for product that has been purchased from the Company based on the product’s expiration date. The Company estimates the amount of its product sales that may be returned by its customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized, as well as within accrued expenses and other current liabilities, net, on the condensed consolidated balance sheets. The Company currently estimates product return liabilities using available industry data and its own sales information, including its visibility into the inventory remaining in the distribution channel. The Company has received an immaterial amount of returns to date and believes that future returns of ZILRETTA will be minimal. Chargebacks Chargebacks for fees and discounts to qualified government healthcare providers represent the estimated obligations resulting from contractual commitments to sell products to qualified VA hospitals and 340b entities at prices lower than the list prices charged to customers who directly purchase the product from the Company. The 340b Drug Discount Program is a U.S. federal government program created in 1992 that requires drug manufacturers to provide outpatient drugs to eligible health care organizations and covered entities at significantly reduced prices. Customers charge the Company for the difference between what they pay for the product and the statutory selling price to the qualified government entity. These reserves are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and trade receivables, net. Chargeback amounts are generally determined at the time of resale to the qualified government healthcare provider by customers, and the Company generally issues credits for such amounts within a few weeks of the customer’s notification to the Company of the resale. Reserves for chargebacks consist of credits that the Company expects to issue for units that remain in the distribution channel inventories at each reporting period-end that the Company expects will be sold to qualified healthcare providers, and chargebacks that customers have claimed, but for which the Company has not yet issued a credit. Government Rebates The Company is subject to discount obligations under state Medicaid programs and Medicare. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability that is included in accrued expenses and other current liabilities on the condensed consolidated balance sheets. For Medicare, the Company also estimates the number of patients in the prescription drug coverage gap for whom the Company will owe an additional liability under the Medicare Part D program. The Company estimates its exposure to utilization from the Medicare Part D coverage gap discount program to be immaterial. For Medicaid programs, the Company estimates the portion of sales attributed to Medicaid patients and records a liability for the rebates to be paid to the respective state Medicaid programs. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but that remains in the distribution channel inventories at the end of each reporting period. Purchaser/Provider Discounts and Rebates The Company offers rebates to eligible purchasers and healthcare providers that are variable based on volume of product purchased. Rebates are based on actual purchase levels during the rebate purchase period. The Company estimates these rebates and records such estimates in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability that is included in accrued expenses and other current liabilities on the condensed consolidated balance sheets. Other Incentives Other incentives that the Company offers include voluntary patient assistance programs, such as the co-pay assistance program, which are intended to provide financial assistance to qualified commercially insured patients with prescription drug co-payments required by payers. The calculation of the accrual for co-pay assistance is based on an estimate of claims and the cost per claim that the Company expects to receive associated with product that has been recognized as revenue, but remains in the distribution channel inventories at the end of each reporting period. The adjustments are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability that is included as a component of accrued expenses and other current liabilities on the condensed consolidated balance sheets. To date, the Company’s only source of product revenue has been from the U.S. sales of ZILRETTA, which it began shipping to customers in October 2017. The following table summarizes activity in each of the product revenue allowance and reserve categories for the six months ended June 30, 2021 and 2020: (In thousands) Service Fees, Government Product Returns Purchaser/ Provider Discounts and Rebates Total Balance as of December 31, 2020 $ 1,733 $ 530 $ 628 $ 1,832 $ 4,723 Provision related to sales in the current quarter 2,188 383 151 2,703 5,425 Credits and payments made ( 1,969 ) ( 266 ) ( 9 ) ( 1,832 ) ( 4,076 ) Adjustments related to prior period sales — — ( 111 ) — ( 111 ) Balance as of March 31, 2021 1,952 647 659 2,703 5,961 Provision related to sales in the current quarter 2,682 424 179 3,100 6,385 Credits and payments made ( 2,527 ) ( 311 ) ( 86 ) ( 2,711 ) ( 5,635 ) Adjustments related to prior period sales ( 10 ) — — — ( 10 ) Balance as of June 30, 2021 $ 2,097 $ 760 $ 752 $ 3,092 $ 6,701 Balance as of December 31, 2019 $ 1,847 $ 248 $ 402 $ 1,656 $ 4,153 Provision related to sales in the current quarter 1,590 254 114 526 2,484 Credits and payments made ( 1,852 ) ( 199 ) ( 10 ) ( 1,656 ) ( 3,717 ) Adjustments related to prior period sales — 95 — — 95 Balance as of March 31, 2020 1,585 398 506 526 3,015 Provision related to sales in the current quarter 1,417 133 98 892 2,540 Credits and payments made ( 1,172 ) ( 262 ) ( 1 ) ( 528 ) ( 1,963 ) Adjustments related to prior period sales — 90 2 92 Balance as of June 30, 2020 $ 1,830 $ 359 $ 603 $ 892 $ 3,684 License Agreement – On March 30, 2020, the Company entered into an exclusive license agreement with Hong Kong Tainuo Pharma Ltd. (“HK Tainuo”) and Jiangsu Tainuo Pharmaceutical Co. Ltd. (“Jiangsu Tainuo”), a subsidiary of China Shijiazhuang Pharmaceutical Co, Ltd., for the development and commercialization (other than manufacturing) of ZILRETTA in Greater China (consisting of mainland China, Hong Kong and Macau, and Taiwan). Under the terms of the agreement, HK Tainuo paid the Company an upfront payment of $ 10.0 million, of which $ 5.0 million was received as of June 30, 2020, and the remaining $ 5.0 million was received as of September 30, 2020. The Company is also eligible to receive up to $ 32.5 million in aggregate development, regulatory, and commercial sales milestone payments. All payments received from HK Tainuo are subject to applicable Hong Kong withholding taxes. HK Tainuo is responsible for the clinical development, product registration, and commercialization of ZILRETTA in Greater China, and Jiangsu Tainuo serves as the guarantor of HK Tainuo’s obligations and responsibilities under the agreement. The Company is solely responsible for the manufacture and supply of ZILRETTA to HK Tainuo for all clinical and commercial activities. The terms related to product manufacturing and supply, including pricing and minimum purchase requirements agreed to in the license agreement, will be covered by a separate supply agreement, which has not yet been finalized. All amounts owed to the Company are nonrefundable and non-creditable once paid. Unless terminated earlier in accordance with its terms, the license agreement continues in effect in perpetuity or as long as HK Tainuo or Jiangsu Tainuo continue to sell ZILRETTA in Greater China. Either party may terminate the agreement prior to expiration in the event of a material breach if not cured within 60 days from the date of notice of such breach (30 days in the case of payment obligations), or either party files for bankruptcy. The Company also has the right to terminate the agreement if HK Tainuo, Jiangsu Tainuo, or any affiliate of each commences any action or proceeding that challenges the validity, enforceability, or scope of any Company patent in Greater China. Upon any such termination, the license granted to HK Tainuo will terminate and all know-how and patents will revert back to the Company. The Company concluded that the license and supply obligations were not distinct performance obligations, and therefore the transaction price will be recognized as revenue as the Company’s supply obligation is fulfilled over the term of the supply agreement, which has not yet commenced. No revenue was recognized associated with this contract as of June 30, 2021. The proceeds associated with the upfront payment have been recorded in short-term deferred revenue on the Company’s condensed consolidated balance sheet as of June 30, 2021, as there is uncertainty around the timing of when the revenue will be recognized. The Company will re-evaluate the classification of deferred revenue when the supply agreement is finalized. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and judgments that may affect the reported amounts of assets and liabilities, revenue and expenses, and related disclosures. The Company bases estimates and judgments on historical experience and on various other factors that it believes to be reasonable under the circumstances. The most significant estimates in these condensed consolidated financial statements include estimates related to revenue recognition and accrued expenses related to preclinical and clinical development costs. The Company’s actual results may differ from these estimates under different assumptions or conditions. The Company evaluates its estimates on an ongoing basis. Changes in estimates are reflected in reported results in the period in which they become known by the Company’s management. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations, and financial condition, including sales, expenses, reserves and allowances, clinical trials, research and development expenses, and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat it, as well as the economic impact on local, regional, national, and international customers and markets. The Company has made estimates of the impact of COVID-19 within its financial statements, and there may be changes to those estimates in future periods. Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation and amortization expense is recognized using the straight-line method over the following estimated useful lives: Estimated Computers, office equipment, and minor computer software 3 Computer software 7 Manufacturing equipment 7 - 10 Furniture and fixtures 5 Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. Costs of major additions and improvements are capitalized and depreciated on a straight-line basis over their useful lives. Repairs and maintenance costs are expensed as incurred. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is credited or charged to income. Property and equipment includes construction-in-progress that is not yet in service. Foreign Currencies The Company maintains a bank account denominated in British Pounds. All foreign currency payables and cash balances are measured at the applicable exchange rate at the end of the reporting period. All associated gains and losses from foreign currency transactions are reflected in the consolidated statements of operations. Leases The Company determines if an arrangement is a lease at contract inception. Operating lease assets represent a right to use an underlying asset for the lease term and operating lease liabilities represent an obligation to make lease payments arising from the lease. Operating lease liabilities with a term greater than one year and their corresponding right-of-use assets are recognized on the balance sheet at the commencement date of the lease based on the present value of lease payments over the expected lease term. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or incentives received. The Company made an accounting policy election to expense leases with a term of one year or less on a straight-line basis over the lease term. To date, the Company has not identified any material short-term leases, either individually or in the aggregate. As the Company’s leases do not provide an implicit rate, the Company utilized the appropriate incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. The Company estimated the incremental borrowing rate based on a yield curve analysis of companies with a similar credit rating to its own, which was calculated using a number of financial ratios and qualitative considerations of the Company’s business. The yields on the Company’s currently outstanding debt (the convertible senior notes and term loan described below) were also used as inputs to the analysis to calculate a spread, adjusted for factors that reflect the profile of secured borrowing over the expected term of the lease. The components of a lease should be split into three categories: lease components ( e.g. , land, building, etc.), non-lease components ( e.g. , common area maintenance, utilities, performance of manufacturing services, purchase of inventory, etc.), and non-components ( e.g. , property taxes, insurance, etc.). Then the fixed contract consideration (including any related to non-components) must be allocated based on fair values to the lease components and non-lease components. Although separation of lease and non-lease components is required, certain practical expedients are available to entities. Entities electing the practical expedient would not separate lease and non-lease components. Rather, they would account for each lease component and the related non-lease component together as a single component. The Company has elected to use this practical expedient for its real estate leases and account for each lease component and related non-lease component as one single component. In contrast, the Company has elected not to apply the practical expedient for its lease of manufacturing space at Patheon and has instead allocated consideration between the lease and non-lease components of the contract. The Company calculated the fair value of the lease component using publicly available information to identify comparable rentals in the same geographic area. The remainder of the consideration was allocated to the non-lease components.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	3. Fair Value of Financial Assets and Liabilities The following tables present information about the Company’s assets that are measured at fair value on a recurring basis as of June 30, 2021 and December 31, 2020, and indicate the level of the fair value hierarchy utilized to determine such fair value: Fair Value Measurements as of June 30, 2021 Using: (In thousands) Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 90,169 $ — $ — $ 90,169 Marketable securities — 23,620 — 23,620 $ 90,169 $ 23,620 $ — $ 113,789 Fair Value Measurements as of December 31, 2020 Using: (In thousands) Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 79,148 $ 6,832 $ — $ 85,980 Marketable securities — 67,576 — 67,576 $ 79,148 $ 74,408 $ — $ 153,556 As of June 30, 2021 and December 31, 2020, the Company’s cash equivalents that are invested in money market funds are valued using Level 1 inputs based on quoted prices for identical securities in active markets. The Company’s marketable securities are valued using Level 2 inputs and primarily rely on quoted prices in active markets for similar marketable securities. Amortization and accretion of discounts and premiums are recorded in other income. As of June 30, 2021, the Company has a term loan outstanding under its 2019 credit facility with Silicon Valley Bank as agent, MidCap Financial Trust, and Flexpoint MCLS Holdings, LLC (the “2019 term loan”), as well as a revolving credit facility. The amount outstanding on the 2019 term loan is reported at its carrying value in the accompanying balance sheet as of June 30, 2021. The Company determined the fair value of the 2019 term loan using an income approach that utilizes a discounted cash flow analysis based on current market interest rates for debt issuances with similar remaining years to maturity, adjusted for credit risk. The 2019 term loan was valued using Level 2 inputs as of June 30, 2021. The result of the calculation yielded a fair value that approximates its carrying value. The Company also concluded that the carrying value of the revolving credit facility approximates fair value because of the short-term maturity of this debt instrument. On May 2, 2017, the Company issued 3.375 % convertible senior notes due 2024 (the “2024 Convertible Notes”) with embedded conversion features. The Company estimated the fair value of the 2024 Convertible Notes using a discounted cash flow approach to derive the value of a debt instrument using the expected cash flows and the estimated yield related to the convertible notes. The significant assumptions used in estimating the expected cash flows were: the estimated market yield based on an implied yield and credit quality analysis of a term loan with similar attributes and the average implied volatility of the Company’s traded and quoted options available as of May 2, 2017. The Company recorded approximately $ 136.7 million as the fair value of the liability on May 2, 2017, with a corresponding amount recorded as a discount on the initial issuance of the 2024 Convertible Notes of approximately $ 64.5 million. The debt discount was recorded to equity and is being amortized to the debt liability over the life of the 2024 Convertible Notes using the effective interest method. The fair value of the 2024 Convertible Notes, which differs from their carrying value, is influenced by interest rates, stock price, and stock price volatility and is determined by prices for the 2024 Convertible Notes observed in market trading. The market for trading of the 2024 Convertible Notes is not considered to be an active market, and therefore the estimate of fair value is based on Level 2 inputs. The estimated fair value of the 2024 Convertible Notes, face value of $ 201.3 million, was $ 183.9 million at June 30, 2021 .

Marketable Securities

Marketable Securities	6 Months Ended
	Jun. 30, 2021
Investments Debt And Equity Securities [Abstract]
Marketable Securities	4. Marketable Securities As of June 30, 2021 and December 31, 2020, the fair value of available-for-sale marketable securities by type of security was as follows: June 30, 2021 (In thousands) Amortized Cost Gross Unrealized Gross Unrealized Fair Value Commercial paper $ 6,397 $ — $ — $ 6,397 Corporate bonds 17,225 — ( 2 ) $ 17,223 $ 23,622 $ — $ ( 2 ) $ 23,620 December 31, 2020 (In thousands) Amortized Cost Gross Unrealized Gross Unrealized Fair Value Commercial paper $ 6,890 $ — $ — $ 6,890 U.S. government obligations 9,997 1 — 9,998 Corporate bonds 50,700 2 ( 14 ) 50,688 $ 67,587 $ 3 $ ( 14 ) $ 67,576 As of June 30, 2021 and December 31, 2020, marketable securities consisted of $ 23.6 million and $ 67.6 million, respectively, of investments that mature within 12 months. There were no investments with maturities greater than 12 months as of June 30, 2021, and December 31, 2020. The Company assesses its available-for-sale marketable securities for impairment on a quarterly basis in accordance with ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . There were no material impairments of the Company’s available-for-sale marketable securities measured and carried at fair value during the three and six months ended June 30, 2021 .

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	6 Months Ended
	Jun. 30, 2021
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	5. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following as of June 30, 2021, and December 31, 2020: (In thousands) June 30, December 31, Prepaid expenses $ 4,756 $ 4,346 Deposits 176 112 Interest receivable on marketable securities 134 246 Other 408 408 Total prepaid expenses and other current assets $ 5,474 $ 5,112

Inventory

Inventory	6 Months Ended
	Jun. 30, 2021
Inventory Disclosure [Abstract]
Inventory	6. Inventory Inventory consisted of the following as of June 30, 2021, and December 31, 2020: (In thousands) June 30, December 31, Raw materials $ 3,573 $ 4,287 Work in process 4,992 4,666 Finished goods 3,736 6,441 Total inventories $ 12,301 $ 15,394 Finished goods manufactured by the Company have a shelf life of approximately 24 months from the date of manufacture. The Company reduces its inventory to net realizable value for potentially excess, dated, or obsolete inventory based on an analysis of forecasted demand compared to quantities on hand and any firm purchase orders, as well as product shelf life. During the three and six months ended June 30, 2021, the Company expensed $ 2.1 million and $ 5.2 million, respectively, to cost of sales for unabsorbed manufacturing and overhead costs related to the operation of the United Kingdom facility at Patheon UK Limited. In addition, cost of sales for the three and six months ended June 30, 2021 , included a charge of $ 0.1 million and $ 0.6 million, respectively, resulting from the write-down of short-dated ZILRETTA inventory that is not expected to be sold prior to expiry.

Property and Equipment, Net

Property and Equipment, Net	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Property and Equipment, Net	7. Property and Equipment, Net Property and equipment, net, as of June 30, 2021, and December 31, 2020, consisted of the following: (In thousands) June 30, December 31, Computer and office equipment $ 1,215 $ 1,203 Manufacturing equipment 12,524 12,297 Furniture and fixtures 609 609 Software 495 495 Leasehold improvements 1,177 1,157 Construction in progress 14,956 13,924 30,976 29,685 Less: Accumulated depreciation ( 11,193 ) ( 10,147 ) Total property and equipment, net $ 19,783 $ 19,538 Depreciation for the three and six months ended June 30, 2021, was approximately $ 0.5 million and $ 1.0 million, respectively, compared to $ 0.6 and $ 0.8 million, respectively, for the same periods in the prior year. No property and equipment was disposed of during the six months ended June 30, 2021 . The Company disposed of one piece of equipment during the three months ended March 31, 2020, and recorded a loss on the disposal of $ 0.3 million. As of June 30, 2021 , construction in progress consisted primarily of equipment purchases related to the expansion of the Company’s manufacturing capabilities at its contract manufacturer, Patheon U.K. Limited.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	6 Months Ended
	Jun. 30, 2021
Payables And Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	8. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following as of June 30, 2021, and December 31, 2020: (In thousands) June 30, December 31, Research and development $ 2,267 $ 1,856 Payroll and other employee-related expenses 9,192 10,674 Professional services fees 2,873 2,094 Accrued interest 1,411 1,464 Product revenue reserves 4,604 2,990 Other 1,005 930 Total accrued expenses and other current liabilities $ 21,352 $ 20,008

Debt

Debt	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Debt	9. Debt Amended and Restated Credit and Security Agreement Term Loan On August 4, 2015, the Company entered into a credit and security agreement with MidCap Financial Trust, as agent, and MidCap Financial Funding XIII Trust and Silicon Valley Bank, as lenders, to borrow up to $ 30.0 million in term loans (the “2015 term loan”). On August 2, 2019, the Company terminated the credit and security agreement and concurrently entered into an amended and restated credit and security agreement (the “amended and restated credit and security agreement”) with Silicon Valley Bank as agent, MidCap Financial Trust, Flexpoint MCLS Holdings, LLC, and the other lenders from time to time party thereto (collectively, the “Lenders”), providing for a term loan of $ 40.0 million and a revolving credit facility of up to $ 20.0 million, both of which mature on January 1, 2024 (the “Maturity Date”). The Company concurrently borrowed the $ 40.0 million term loan and used $ 7.7 million of the proceeds to repay the remaining amount owed on the 2015 term loan. The Company granted the Lenders a security interest in substantially all of its personal property, rights, and assets, other than intellectual property, to secure the payment of all amounts owed under the amended and restated credit and security agreement. The Company agreed not to encumber any of its intellectual property without the Lenders’ prior written consent. The amended and restated credit and security agreement contains certain representations, warranties, and covenants of the Company, including a minimum revenue covenant that will be in effect at any time the Company’s liquidity (defined as cash, cash equivalents, and marketable securities held with Silicon Valley Bank and certain accounts receivable as deemed eligible under the amended and restated credit and security agreement) is below $ 80.0 million. Additionally, if the Company’s liquidity is below $ 80.0 million, all amounts received from customer collections will be applied immediately to reduce the revolving credit facility. Beginning in May 2021, the minimum revenue covenant, if it applies, will be the greatest of (i) a conservative percentage of the year’s approved forecast, (ii) modest growth over the trailing twelve months of actual revenues, and (iii) 100 % of the minimum revenue covenant amount for the preceding month. On May 18, 2020, the Company borrowed $ 15.0 million under a new term loan advance and immediately used the proceeds to repay an equal amount under the revolving credit facility, and the maximum principal amount of the revolving credit facility was reduced from $ 20.0 million to $ 5.0 million. The new term loan is subject to substantially the same terms, including interest rate, amortization, and maturity date, as the existing term loan under the credit facility. The amended and restated credit and security agreement also has a material adverse event clause. If the minimum revenue covenant becomes applicable and the Company fails to comply with it, or a material adverse change as defined in the agreement occurs, the amounts due under the amended and restated credit and security agreement could be declared immediately due and payable. As of June 30, 2021, the Company was compliant with all financial covenants. Term loan borrowings under the credit facility accrue interest monthly at a floating interest rate equal to the greater of the prime rate plus 1.5% or 6.5% per annum . Following an interest-only period of 18 months, principal is due in 36 equal monthly installments commencing February 1, 2021 , and ending on the Maturity Date. Upon the Maturity Date, the Company will be obligated to pay a final payment equal to 6.75 % of the total principal amounts borrowed under the facility. The final payment amount is being accreted to the carrying value of the debt using the straight-line method, which approximates the effective interest method. As of June 30, 2021, the carrying value of the 2019 term loan was approximately $ 48.7 million, of which $ 1.5 million is due within 12 months and $ 47.2 million is due in greater than 12 months. Due to the July 30, 2021, refinancing discussed in Note 13, the carrying value of the 2019 term loan, less payments made subsequent to the balance sheet date and prior to the refinancing, has been presented as long-term debt in the Company’s condensed consolidated balance sheet as of June 30, 2021. The Company may prepay the 2019 term loan at any time by paying the outstanding principal balance, a final payment equal to 6.75 % of the term loan amount, all accrued interest, and a prepayment fee of 3 % of the outstanding term loan amount if repaid in the first year, 2 % of the outstanding term loan amount if repaid in the second year, and 1 % of the outstanding term loan amount if repaid in the third year of the loan; no prepayment fee is required thereafter. As of June 30, 2021, annual principal and interest payments due under the term loan were as follows: Year Aggregate (in thousands) 2021 10,605 2022 20,296 2023 19,088 2024 5,249 Thereafter — Total $ 55,238 Less interest ( 4,164 ) Less unamortized portion of final payment ( 2,339 ) Total $ 48,735 Revolving Credit Facility Borrowings under the revolving credit facility accrue interest monthly at a floating interest rate equal to the greater of the prime rate or 5.50% per annum . In addition to paying interest on any amounts borrowed under the revolving credit facility, the Company owes an unused revolving line facility fee equal to 0.25 % per annum of the average unused portion of the revolving line, multiplied by the difference between the total amount available to be borrowed (the “Revolving Commitment Amount”) and the greater of the average outstanding revolver balance and 25 % of the Revolving Commitment Amount . The revolving credit facility and any related fees or interest payments became available to the Company beginning January 1, 2020, and, in February 2020, the Company drew down the $ 20.0 million available. On May 18, 2020, the Company repaid $ 15.0 million of the outstanding principal balance, and the maximum principal amount of the revolving credit facility was reduced from $20.0 million to $ 5.0 million. Beginning on January 1, 2020, if the interest payment on the revolving credit facility is less than the amount of interest that would have been payable had the Company borrowed 25% of the Revolving Commitment Amount, then the Company will be required to pay the difference. The Company may retire the revolving credit facility early, at any time, by paying the outstanding principal balance, all accrued interest, and a termination fee equal to 2 % of the Revolving Commitment Amount if repaid in the first year, and 1 % of the Revolving Commitment Amount if repaid in the second year; with no termination fee thereafter. 2024 Convertible Notes On May 2, 2017, the Company issued an aggregate of $ 201.3 million principal amount of the 2024 Convertible Notes. The 2024 Convertible Notes have a maturity date of May 1, 2024 , are unsecured, and accrue interest at a rate of 3.375 % per annum, payable semi-annually on May 1 and November 1 of each year, beginning November 1, 2017. The Company received $ 194.8 million for the sale of the 2024 Convertible Notes, after deducting fees and expenses of $ 6.5 million. Upon conversion of the 2024 Convertible Notes, at the election of each holder of a 2024 Convertible Note (the “Holder”), the note will be convertible into cash, shares of the Company’s common stock, or a combination thereof, at the Company’s election (subject to certain limitations in the 2015 term loan), at a conversion rate of approximately 37.3413 shares of common stock per $1,000 principal amount of the 2024 Convertible Notes, which corresponds to an initial conversion price of approximately $ 26.78 per share of the Company’s common stock. The conversion rate is subject to adjustment from time to time upon the occurrence of certain events, including, but not limited to, fundamental change events and certain corporate events that occur prior to the maturity date of the notes. In addition, if the Company delivers a notice of redemption, the Company will increase, in certain circumstances, the conversion rate for a Holder who elects to convert its notes in connection with such a corporate event or notice of redemption, as the case may be. At any time prior to the close of business on the business day immediately preceding February 1, 2024, Holders may convert all, or any portion, of the 2024 Convertible Notes at their option only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on June 30, 2017 (and only during such calendar quarter), if the last reported sale price of the common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130 % of the conversion price on each applicable trading day; (2) during the five -business-day period after any ten -consecutive-trading-day period (the “measurement period”) in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98 % of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day; (3) if the Company calls any or all of the notes for redemption, at any time prior to the close of business on the business day immediately preceding the redemption date; and (4) upon the occurrence of specified corporate events. On or after February 1, 2024, until the close of business on the business day immediately preceding the maturity date, Holders may convert their notes at any time, regardless of the foregoing circumstances. The Company may redeem, for cash, all or any portion of the 2024 Convertible Notes, at its option, on or after May 6, 2020 , if the last reported sale price of the Company’s common stock has been at least 130 % of the conversion price for at least 20 trading days during any 30 consecutive day trading period, at a redemption price equal to 100 % of the principal amount of the 2024 Convertible Notes to be redeemed, plus accrued and unpaid interest, subject to the Holders’ right to convert as described above. The 2024 Convertible Notes are considered convertible debt with a cash conversion feature. Per ASC 470-20, Debt with Conversion and Other Options, the Company has separated the convertible debt into liability and equity components based on the fair value of a similar debt instrument excluding the embedded conversion option. The carrying amount of the liability component was calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The allocation was performed in a manner that reflected our non-convertible debt borrowing rate for similar debt. The equity component of the 2024 Convertible Notes was recognized as a debt discount and represents the difference between the proceeds from the issuance of the 2024 Convertible Notes and the fair value of the liability of the 2024 Convertible Notes on their respective dates of issuance. The excess of the principal amount of the liability component over its carrying amount (“debt discount”) is amortized to interest expense using the effective interest method over seven years . The equity component is not re-measured as long as it continues to meet the conditions for equity classification. The liability component of $ 136.7 million was recorded as long-term debt at May 2, 2017, with the remaining equity component of $ 64.5 million recorded as additional paid-in capital. In connection with the issuance of the 2024 Convertible Notes, the Company incurred approximately $ 6.5 million of debt issuance costs, which primarily consisted of underwriting, legal, and other professional fees, and allocated these costs to the liability and equity components based on the allocation of the proceeds. Of the total debt issuance costs, $ 4.4 million was allocated to the liability component and are recorded as a reduction of the 2024 Convertible Notes in our consolidated balance sheets. The remaining $ 2.1 million was allocated to the equity component and is recorded as a reduction to additional paid-in capital. Debt discount and issuance costs of $ 68.9 million are being amortized to interest expense over the life of the 2024 Convertible Notes using the effective interest rate method. As of June 30, 2021 , the stated interest rate was 3.375 %, and the effective interest rate was 9.71 %. Interest expense related to the 2024 Convertible Notes for the three and six months ended June 30, 2021, was $ 4.1 million and $ 8.1 million, including $ 2.4 million and $ 4.7 million, related to amortization of the debt discount. The table below summarizes the carrying value of the 2024 Convertible Notes as of June 30, 2021: ( in thousands ) Gross proceeds $ 201,250 Portion of proceeds allocated to equity component (additional ( 64,541 ) Debt issuance costs ( 6,470 ) Portion of issuance costs allocated to equity component 2,075 Amortization of debt discount and debt issuance costs 35,500 Carrying value 2024 Convertible Notes $ 167,814

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	10. Stock-Based Compensation Stock Option Valuation The fair value of each of the Company’s stock option grants is estimated on the date of grant using the Black-Scholes option-pricing model. Expected volatility is based on historical volatility of the Company’s common stock. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain vanilla” options. The expected term of stock options granted to non-employees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. The relevant data used to determine the value of the stock option grants for the three and six months ended June 30, 2021 and 2020, were as follows: Three months ended Six months ended June 30, June 30, 2021 2020 2021 2020 Risk-free interest rates 1.26 - 1.28 % 0.51 - 0.56 % 1.12 - 1.28 % 0.51 - 1.79 % Expected dividend yield 0.00 % 0.00 % 0.00 % 0.00 % Expected term (in years) 6.0 6.0 6.0 6.0 Expected volatility 71.9 - 72.2 % 70.3 - 72.3 % 71.9 - 72.4 % 65.4 - 72.3 % The following table summarizes stock option activity for the six months ended June 30, 2021: (In thousands, except per share amounts) Shares Issuable Options Weighted Average Price Outstanding as of December 31, 2020 4,592 $ 17.77 Granted 350 9.55 Exercised ( 43 ) 3.40 Cancelled ( 522 ) 18.42 Outstanding as of June 30, 2021 4,377 $ 17.18 Options vested and expected to vest at June 30, 2021 4,377 $ 17.18 Options exercisable at June 30, 2021 3,480 $ 18.12 The aggregate intrinsic value of options is calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock. Options to purchase a total of 42,682 shares of the Company’s common stock, with an aggregate intrinsic value of approximately $ 386,138 , were exercised during the six months ended June 30, 2021. At June 30, 2021 and 2020, there were options for the purchase of 4,376,841 and 4,926,718 shares of the Company’s common stock outstanding, respectively, with a weighted average remaining contractual term of 5.9 years and 6.7 years, respectively, and with a weighted average exercise price of $ 17.18 and $ 17.75 per share, respectively. The weighted average grant date fair value of options granted during the six months ended June 30, 2021 and 2020, was $ 6.09 and $ 8.94 per share, respectively. Restricted Stock Units During the six months ended June 30, 2021, the Company awarded 1,097,555 restricted stock units (“RSUs”) to employees at a weighted average grant date fair value of $ 9.73 per share. The majority of the RSUs vest in four substantially equal installments on each of the first four anniversaries of the vesting commencement date, subject to the employee’s continued employment with, or services to, the Company on each vesting date . Compensation expense is recognized on a straight-line basis. Included in the 2021 RSU awards was a grant of 106,100 RSUs to the Company’s chief executive officer. These RSUs have two performance conditions relating to achieving a certain revenue threshold for the year ending December 31, 2021, as well as progressing at least one of the Company’s current pipeline assets. The number of shares ultimately eligible for vesting under the RSU award will depend upon the degree to which the performance conditions are achieved. The maximum number of shares that are eligible for vesting under the award is 159,150 , which would be earned based on 150 % achievement of the performance conditions. The portion of the RSUs eligible for vesting will vest in four substantially equal installments starting in 2022 upon confirmation of such performance metrics being achieved and thereafter on January 1 of the subsequent three years so that all of such shares will have vested on January 1, 2025, subject to the employee’s continued employment with, or services to, the Company on each vesting date. As of June 30, 2021, the Company concluded that it was not probable that either performance condition would be met. Therefore, no expense has been recognized for these awards during the three and six months ended June 30, 2021. The following table summarizes the RSU activity for the six months ended June 30, 2021: (In thousands, except per share amounts) Number of Weighted Nonvested balance as of December 31, 2020 2,193 $ 14.15 Granted 1,098 9.73 Vested/Released ( 419 ) 15.22 Cancelled ( 434 ) 13.44 Nonvested Balance as of June 30, 2021 2,438 $ 12.10 Stock-based Compensation The Company recorded stock-based compensation expense related to stock options and RSUs and shares purchased under the Employee Stock Purchase Plan for the three and six months ended June 30, 2021 and 2020, as follows: For the three months For the six months (In thousands) 2021 2020 2021 2020 Research and development $ 1,024 $ 1,087 $ 2,303 $ 3,289 Selling, general and administrative 2,951 2,700 6,312 5,149 Total $ 3,975 $ 3,787 $ 8,615 $ 8,438 As of June 30, 2021, unrecognized stock-based compensation expense for stock options outstanding was approximately $ 7.2 million, which is expected to be recognized over a weighted average period of 2.3 years. As of June 30, 2021, unrecognized stock-based compensation expense for RSUs outstanding was $ 23.3 million, which is expected to be recognized over a weighted average period of 2.4 years.

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Loss per Share	11. Net Loss per Share Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the three and six months ended June 30, 2021 and 2020: For the three months For the six months (In thousands, except per share amounts) 2021 2020 2021 2020 Numerator: Net loss $ ( 22,208 ) $ ( 32,619 ) $ ( 50,764 ) $ ( 69,421 ) Net loss: $ ( 22,208 ) $ ( 32,619 ) $ ( 50,764 ) $ ( 69,421 ) Denominator: Weighted average common shares 49,968 42,776 49,905 40,664 Net loss per share, basic and diluted $ ( 0.44 ) $ ( 0.76 ) $ ( 1.02 ) $ ( 1.71 ) The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated as including them would have an anti-dilutive effect: For the three months For the six months (In thousands) 2021 2020 2021 2020 Shares issuable upon conversion of the 7,515 7,515 7,515 7,515 Stock options 4,401 4,987 4,530 4,925 Restricted stock units 2,618 1,479 2,376 1,196 Total 14,534 13,981 14,421 13,636

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	12. Commitments and Contingencies Operating Leases Burlington Lease In May 2013, the Company entered into a lease for office space in Burlington, Massachusetts (the “Lease”), for an initial term of 42 months. In June 2019, the Company amended the Lease to add additional square feet of office space and extend the term of the Lease through April 30, 2025 (the “Amended Lease”). As a result of the Amended Lease, the total rentable floor area is 41,873 square feet. Starting in August 2019, the Company’s minimum monthly lease payment is approximately $ 108,000 , which increases over the term of the Amended Lease. In addition to the base rent for the office space, the Company is responsible for its share of operating expenses and real estate taxes. The straight-line lease cost for the Amended Lease (including the expense relating to the original Lease) for the three and six months ended June 30, 2021 , amounted to $ 0.5 million and $ 0.9 million, respectively, compared to $ 0.4 million and $ 0.9 million, respectively, for the same periods in the prior year, and was included in operating expenses. As of June 30, 2021 , the remaining lease term on the Amended Lease was 3.8 years, which includes the 18 -month extension resulting from the amendment signed in June 2019. Woburn Lease In February 2017, the Company entered into a five-year lease for laboratory space located in Woburn, Massachusetts, with a monthly lease payment of approximately $ 15,000 , which increases over the term of the lease, plus a share of operating expenses. The straight-line lease cost for the Woburn lease amounted to $ 46,000 and $ 92,000 for each of the three and six months ended June 30, 2021 and 2020, respectively, and was included in operating expenses. In June 2021, the Company amended the Woburn lease to extend the term of the lease through February 29, 2024 . Starting in March 2022, the Company’s minimum monthly lease payment will be approximately $ 20,400 , which increases over the term of the amended lease. The Company accounted for the amended lease as a modification that is not a separate contract from the original lease, as the amended lease does not contain any additional rights, and recorded an incremental right-of-use asset and lease liability of $ 0.4 million, which represents the present value of the lease payments over the remaining lease term of 2.7 years, discounted at 8.4%. As of June 30, 2021 , the remaining lease term on the Woburn lease, as amended, was 2.7 years. Manufacturing and Supply Agreement with Patheon UK Limited In July 2015, the Company and Patheon UK Limited (“Patheon”) entered into a Manufacturing and Supply Agreement (the “Manufacturing Agreement”) and a Technical Transfer and Service Agreement (the “Technical Transfer Agreement”) for the manufacture of ZILRETTA. Patheon agreed in the Technical Transfer Agreement to undertake certain transfer activities and construction services needed to prepare Patheon’s United Kingdom facility for the commercial manufacture of ZILRETTA in dedicated manufacturing suites. The Company provided Patheon with certain equipment and materials necessary to manufacture ZILRETTA and pays Patheon a monthly fee for such activities and reimburses Patheon for certain material, equipment, and miscellaneous expenses and additional services. The initial term of the Manufacturing Agreement is 10 years from approval by the FDA of the Patheon manufacturing suites for ZILRETTA, or until October 6, 2027. The Company pays a monthly base fee to Patheon for the operation of the manufacturing suites and a per product fee for each vial based upon a forecast of commercial demand. The Company also reimburses Patheon for purchases of materials and equipment made on its behalf, certain nominal expenses, and additional services. The Manufacturing Agreement will remain in full effect unless and until it expires or is terminated. Upon termination of the Manufacturing Agreement (other than termination by Flexion in the event that Patheon does not meet the construction and manufacturing milestones or for a breach by Patheon), Flexion will be obligated to pay for the costs incurred by Patheon associated with the removal of Flexion’s manufacturing equipment and for Patheon’s termination costs up to a capped amount. The Manufacturing Agreement with Patheon contains an operating lease for the use of dedicated manufacturing suites. With the adoption of ASU 2016-02, the Company recorded a right-of-use asset and corresponding lease liability for the operating lease. In June 2019, the Company and Patheon amended the Manufacturing Agreement and the Technical Transfer Agreement. The amendment primarily modifies the compensation structure, which is comprised of base fees and per product fees the Company pays to Patheon and does not result in any additional rights of use. The Company accounted for the amendment as a lease modification that is not a separate contract from the original lease. As part of the modification, the Company reassessed whether the contract is or contains a lease and determined that there is an operating lease component for the use of dedicated manufacturing suites. The remainder of the consideration is allocated to the service component. The Company also reassessed the lease liability by calculating the present value of the remaining lease payments as of the modification date, discounted at 6.1 %. The modification resulted in an increase to each of the lease liability and right of use asset of $ 0.5 million. In April 2020, the Company entered into a side letter amending the Manufacturing Agreement with Patheon pursuant to which the parties agreed that the Company would continue to pay the monthly base fee for maintaining the manufacturing suites, but minimum purchase obligations would be cancelled for 2020 as the Company temporarily suspended manufacturing activities for ZILRETTA due to COVID-19. The amendment did not change the amount of fixed consideration owed to Patheon over the life of the contract, nor did it grant the Company any additional rights of use. As such, there was no change in the accounting for the embedded lease as a result of this amendment. The Company restarted manufacturing activities at Patheon in the fourth quarter of 2020. As of June 30, 2021 , the remaining lease term on the Patheon lease was 6.3 years. The straight-line lease cost for the three and six months ended June 30, 2021 , amounted to $ 62,000 and $ 124,000 , respectively, compared to $ 55,000 and $ 113,000 , respectively, for the same periods in the prior year, and is included in inventory as part of manufacturing overhead. The components of lease expense and related cash flows were as follows: (In thousands) For the three months For the six months Operating lease cost 2021 2020 2021 2020 Operating lease cost included in operating expenses $ 514 $ 514 $ 1,027 $ 1,027 Operating lease cost included in inventory 62 55 124 113 Total operating lease cost 576 569 1,151 1,140 Operating cash flows from operating leases 809 739 1,595 1,557 Maturities of lease liability due under these lease agreements as of June 30, 2021, were as follows: Year Operating Lease Obligations (In thousands) 2021 1,027 2022 2,093 2023 2,148 2024 1,981 2025 816 Thereafter 433 Present value of imputed interest ( 2,211 ) Total $ 6,287 Other Commitments and Contingencies Evonik Supply Agreement In November 2016, the Company entered into a Supply Agreement with Evonik Corporation (“Evonik”) for the purchase of PLGA, which is used in the manufacturing of clinical and commercial supply of ZILRETTA. Pursuant to the Supply Agreement, Flexion is obligated to submit rolling monthly forecasts to Evonik for PLGA supply, a portion of which will constitute binding orders. In addition, Flexion agreed to certain minimum purchase requirements, which do not apply (i) during periods in which Evonik is in material breach of the Supply Agreement or is unable to perform its obligations due to a force majeure event, (ii) with respect to orders that Evonik is unable to supply in excess of binding orders, (iii) for orders Evonik is unable to timely deliver or does not deliver conforming product and provides a credit for such order, or (iv) during an uncured material quality failure by Evonik. Flexion agreed to purchase PLGA batches at a specified price per gram in U.S. dollars, subject to adjustment from time to time, including due to changes in price indices and in the event the initial term of the Supply Agreement was extended. The initial term of the agreement was five years , commencing in July 2016. In May 2021, the Company entered into an amendment to the Supply Agreement that became effective on June 30, 2021. The total term of the Supply Agreement, as amended, is eight years. Upon termination of the Supply Agreement (other than termination due to the bankruptcy of either Evonik or Flexion), Flexion is obligated to pay the costs associated with the binding supply forecast provided to Evonik. FX201-Related Agreements In December 2017, the Company entered into a definitive agreement with GeneQuine Biotherapeutics GmbH (“GeneQuine”) to acquire the global rights to FX201. As part of the asset purchase transaction, the Company made an upfront payment to GeneQuine of $ 2.0 million. The upfront fee was attributed to the intellectual property acquired and recognized as research and development expense in December 2017 as the FX201 rights had not been commercially approved and had no alternative future use. In 2018, the Company paid GeneQuine $ 750,000 for initiating a GLP toxicology study of FX201. In addition, the Company paid GeneQuine $ 750,000 in November 2019 following the FDA acceptance of the Investigational New Drug (“IND”) application for FX201. The next milestone of $ 2.5 million was achieved in March 2020, when the first patient was treated in the Phase 1 clinical trial. The Company may also be required to make additional milestone payments during the development of FX201, including up to $ 4.5 million for the initiation of a Phase 2 proof of concept (“PoC”) clinical trial and, following successful PoC, up to an additional $ 51.5 million in development and global regulatory approval milestone payments. The transaction was accounted for as an asset acquisition, as it did not qualify as a business combination. Milestone payments earned prior to regulatory approval of FX201 are recognized as research and development expense in the period when the milestone events become probable of being achieved. Future milestones earned upon regulatory approval would be recognized as an intangible asset and amortized to expense over its estimated life. As of June 30, 2021 , no other milestones under the arrangement were probable of being achieved. As part of the transaction, the Company became the direct licensee of certain underlying Baylor College of Medicine (“Baylor”) patents and other proprietary rights related to FX201 for human applications. The Baylor license agreement grants the Company an exclusive, royalty-bearing, world-wide right and license (with a right to sublicense) for human applications under its patent and other proprietary rights directly related to FX201, with a similar non-exclusive license to certain Baylor intellectual property rights that are not specific to FX201. The license agreement with Baylor includes a low single-digit royalty on net sales of FX201 and requires the Company to use reasonable efforts to develop FX201 according to timelines set out in the license agreement. In December 2017, the Company also entered into a Master Production Services Agreement with SAFC Carlsbad, Inc., a part of MilliporeSigma, for the manufacturing of preclinical and initial clinical supplies of FX201. In addition, in February 2020 the Company entered into a manufacturing agreement with another vendor for clinical trial supply of FX201 through Phase 3 clinical trials. FX301-Related Agreements In September 2019, the Company entered into a definitive agreement with Xenon Pharmaceuticals, Inc. (“Xenon”) that provides the Company with the global rights to develop and commercialize XEN402, Xenon’s NaV1.7 inhibitor known as funapide, formulated for extended release with a novel, Flexion proprietary thermosensitive hydrogel under the Company’s preclinical program known as FX301. The transaction was accounted for as an asset acquisition, as it did not qualify as a business combination. As part of the asset purchase transaction, the Company made an upfront payment to Xenon of $ 3.0 million. The upfront fee was attributed to the intellectual property acquired and was recognized as research and development expense in September 2019 as the FX301 product candidate had not been commercially approved and had no alternative future use. The next milestone of $ 0.5 million was achieved following the commencement of the GLP toxicology study. This milestone was recognized as research and development expense in the first quarter of 2020. The Company also paid $ 1.0 million when the IND was cleared by FDA in February 2021 and $ 2.0 million upon the initiation of the Phase 1b clinical trial in March 2021. These milestones were recognized as research and development expenses in the first quarter of 2021. The Company may also be required to make additional milestone payments during the development of FX301, including up to $ 5.0 million through initiation of a Phase 2 PoC clinical trial and, following successful PoC, up to $ 40.8 million in development and global regulatory approval milestone payments and up to an additional $ 75.0 million in sales-related milestone payments. Future milestone payments earned prior to regulatory approval of FX301 would be recognized as research and development expense in the period when the milestone events become probable of being achieved. Future milestones earned subsequent to regulatory approval would be recognized as an intangible asset and amortized to expense over the estimated life of FX301. As of June 30, 2021 , no other milestones under the arrangement were probable of being achieved. As part of the transaction, the Company became the direct licensee of certain underlying Xenon patents and other proprietary rights related to XEN402 for human applications. The Xenon agreement grants the Company an exclusive, royalty-bearing, world-wide right and license (with a right to sublicense) for human applications under its patents directly related to XEN402, with a similar royalty-free license to other Xenon proprietary rights directly related to XEN402. The agreement with Xenon includes a tiered royalty ranging from mid-single digits to low double digits that is based on aggregate annual net sales of FX301 and requires the Company to use reasonable efforts to develop FX301 according to timelines set out in the agreement.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	13. Subsequent Events On July 30, 2021, the Company entered into a second amendment (the “2021 Amended Credit Agreement”) to its amended and restated credit and security agreement (the “Existing Credit Agreement”) with Silicon Valley Bank, as agent and lender, MidCap Financial Trust, MidCap Funding XIII Trust, and the other lenders from time to time party thereto (collectively, the “Lenders”), providing for a term loan facility of up to $ 75.0 million, with $ 55.0 million available at closing and an additional $ 20.0 million (the “second tranche”) available upon positive Phase 1 clinical trial data in either of the Company’s two pipeline programs, FX201 and FX301, sufficient to initiate a Phase 2 clinical study, and a revolving credit facility of up to $ 25.0 million, both of which mature on February 1, 2024 , which may be extended to July 1, 2026, upon satisfaction of certain specified conditions set forth in the 2021 Amended Credit Agreement (the “Maturity Date”). The Company concurrently borrowed the $ 55.0 million term loan (the “2021 term loan”), simultaneously used $ 48.1 million of the proceeds to repay the outstanding term loan under the Existing Credit Agreement, and drew down $ 20.0 million from the revolving credit facility, bringing the total revolver balance to $ 25.0 million. The 2021 Amended Credit Agreement contains certain representations, warranties, and covenants, including a minimum revenue covenant that will be in effect at any time the Company’s liquidity (defined as cash, cash equivalents and marketable securities held with Silicon Valley Bank and certain accounts receivable as deemed eligible under the 2021 Amended Credit Agreement) is below $ 100.0 million (if the second tranche is undrawn) or $ 120.0 million (if the second tranche is drawn). Additionally, if the Company’s liquidity is below $100.0 million, all amounts received from customer collections will be applied immediately to reduce the revolving credit facility. The minimum revenue covenant, if it applies in the future, is applied to the trailing six-months of net revenue and is determined based on the Company’s approved forecast, as determined by the Lenders. The applicable interest rate under the 2021 Amended Credit Agreement is (a) with respect to the term loan, the greater of (i) the prime rate published by the Wall Street Journal (“Prime Rate”) plus 2.75% or (ii) 6.00%, and (b) with respect to the revolving loan is the greater of (i) the Prime Rate plus 1.75% or (ii) 5.00%. Under the term loan credit facility, following an interest-only period ending on August 1, 2023 (if the second tranche is undrawn), or August 1, 2024 (if the second tranche is drawn), principal is due in equal monthly installments through the Maturity Date. The Company may prepay the term loan at any time by paying the outstanding principal balance, a final payment equal to 4.75 % of the term loan amount, all accrued interest, and a prepayment fee of 3 % of the outstanding term loan amount if repaid in the first year, 2 % of the outstanding term loan amount if repaid in the second year, and 1 % of the outstanding term loan amount if repaid in the third year of the loan; no prepayment fee is required thereafter. The Company granted the Lenders a security interest in substantially all of its personal property, rights, and assets, other than intellectual property, to secure the payment of all amounts owed under the 2021 Amended Credit Agreement. The Company also agreed not to encumber any of its intellectual property without the Lenders’ prior written consent.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements as of June 30, 2021, and for the three and six months ended June 30, 2021 and 2020, have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (the “SEC”) and Generally Accepted Accounting Principles (“GAAP”) for consolidated financial information including the accounts of the Company and its wholly owned subsidiary after elimination of all significant intercompany accounts and transactions. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In the opinion of management, these condensed consolidated financial statements reflect all adjustments that are necessary for a fair statement of the Company’s financial position and results of its operations, as of and for the periods presented. These condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K filed with the SEC on March 10, 2021. The information presented in the condensed consolidated financial statements and related notes as of June 30, 2021, and December 31, 2020, and for the three and six months ended June 30, 2021 and 2020, is unaudited. The December 31, 2020, condensed consolidated balance sheet included herein was derived from the audited financial statements as of that date, but does not include all disclosures, including notes, required by GAAP for complete financial statements. Interim results for the three and six months ended June 30, 2021 , are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2021, or any future period.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting Standards Recently Issued In August 2020, the FASB issued ASU No. 2020-06, (“ASU 2020-06”). The new standard simplifies the accounting for certain financial instruments with characteristics of liabilities and equity. The new guidance reduced the number of accounting models for convertible debt and convertible preferred stock instruments and made certain disclosure amendments intended to improve the information provided to users. The guidance also amended the derivative guidance for the “own stock” scope exception, which exempts qualifying instruments from being accounted for as derivatives if certain criteria are met. Finally, the standard changed the way certain convertible instruments are treated when calculating earnings per share. The standard is effective for the Company for fiscal years, and the interim periods within those years, beginning after December 15, 2021, and early adoption is permitted. The Company is currently evaluating the impact of ASU 2020-06 on the Company’s condensed consolidated financial statements.
Consolidation	Consolidation The accompanying condensed consolidated financial statements include the Company and its wholly owned subsidiary, Flexion Therapeutics Securities Corporation. The Company has eliminated all intercompany transactions for the three and six months ended June 30, 2021, and the year ended December 31, 2020 .
Revenue Recognition	Revenue Recognition On October 6, 2017, the U.S. Food and Drug Administration (“FDA”) approved ZILRETTA. The Company entered into a limited number of arrangements with specialty distributors and a specialty pharmacy in the U.S. to distribute ZILRETTA. The Company recognizes revenue in accordance with Accounting Standards Codification (“ASC”) Topic 606 - Revenue from Contracts with Customers (“Topic 606”). Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to be entitled to in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the 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 revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to arrangements that meet the definition of a contract with a customer under Topic 606, including when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Product Revenue, Net The Company primarily sells ZILRETTA to specialty distributors and a specialty pharmacy, who then subsequently resell ZILRETTA to physicians, clinics, and certain medical centers or hospitals. The Company also contracts directly with healthcare providers and intermediaries such as Group Purchasing Organizations (“GPOs”). In addition, the Company enters into arrangements with government payers that provide for government mandated rebates and chargebacks with respect to the purchase of ZILRETTA. The Company recognizes revenue on product sales when the customer obtains control of the Company’s product, which occurs at a point in time (upon delivery to the customer). The Company has determined that the delivery of ZILRETTA to its customers constitutes a single performance obligation. There are no other promises to deliver goods or services beyond what is specified in each accepted customer order. The Company has assessed the existence of a significant financing component in the agreements with its customers. The trade payment terms with customers do not exceed one year , and therefore the Company has elected to apply the practical expedient and no amount of consideration has been allocated as a financing component. Product revenues are recorded net of applicable reserves for variable consideration, including discounts and allowances. Transaction Price, including Variable Consideration Revenues from product sales are recorded at the net sales price (transaction price), which includes estimates of variable consideration for which reserves are established. Components of variable consideration include trade discounts and allowances, product returns, government chargebacks, discounts and rebates, and other incentives, such as voluntary patient assistance, and other fee-for-service amounts that are detailed within contracts between the Company and its customers relating to the Company’s sale of its products. These reserves, as detailed below, are based on the amounts earned, or to be claimed on the related sales, and are classified as reductions of accounts receivable (if the amount is payable to the customer) or a current liability (if the amount is payable to a party other than a customer). These estimates take into consideration a range of possible outcomes that are probability-weighted in accordance with the expected value method in Topic 606 for relevant factors such as current contractual and statutory requirements, specific known market events and trends, industry data, and forecasted customer buying and payment patterns. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the respective underlying contracts. The amount of variable consideration that is included in the transaction price may be constrained and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized under the contract will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s original estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. Service Fees and Allowances The Company compensates its customers and GPOs for sales order management, data, and distribution services. However, the Company has determined such services received to date are not distinct from the Company’s sale of products to the customer and, therefore, these payments have been recorded as a reduction of revenue within the statement of operations and comprehensive loss through June 30, 2021, as well as a reduction to trade receivables, net on the condensed consolidated balance sheets. Product Returns Consistent with industry practice, the Company generally offers customers a limited right of return for product that has been purchased from the Company based on the product’s expiration date. The Company estimates the amount of its product sales that may be returned by its customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized, as well as within accrued expenses and other current liabilities, net, on the condensed consolidated balance sheets. The Company currently estimates product return liabilities using available industry data and its own sales information, including its visibility into the inventory remaining in the distribution channel. The Company has received an immaterial amount of returns to date and believes that future returns of ZILRETTA will be minimal. Chargebacks Chargebacks for fees and discounts to qualified government healthcare providers represent the estimated obligations resulting from contractual commitments to sell products to qualified VA hospitals and 340b entities at prices lower than the list prices charged to customers who directly purchase the product from the Company. The 340b Drug Discount Program is a U.S. federal government program created in 1992 that requires drug manufacturers to provide outpatient drugs to eligible health care organizations and covered entities at significantly reduced prices. Customers charge the Company for the difference between what they pay for the product and the statutory selling price to the qualified government entity. These reserves are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and trade receivables, net. Chargeback amounts are generally determined at the time of resale to the qualified government healthcare provider by customers, and the Company generally issues credits for such amounts within a few weeks of the customer’s notification to the Company of the resale. Reserves for chargebacks consist of credits that the Company expects to issue for units that remain in the distribution channel inventories at each reporting period-end that the Company expects will be sold to qualified healthcare providers, and chargebacks that customers have claimed, but for which the Company has not yet issued a credit. Government Rebates The Company is subject to discount obligations under state Medicaid programs and Medicare. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability that is included in accrued expenses and other current liabilities on the condensed consolidated balance sheets. For Medicare, the Company also estimates the number of patients in the prescription drug coverage gap for whom the Company will owe an additional liability under the Medicare Part D program. The Company estimates its exposure to utilization from the Medicare Part D coverage gap discount program to be immaterial. For Medicaid programs, the Company estimates the portion of sales attributed to Medicaid patients and records a liability for the rebates to be paid to the respective state Medicaid programs. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but that remains in the distribution channel inventories at the end of each reporting period. Purchaser/Provider Discounts and Rebates The Company offers rebates to eligible purchasers and healthcare providers that are variable based on volume of product purchased. Rebates are based on actual purchase levels during the rebate purchase period. The Company estimates these rebates and records such estimates in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability that is included in accrued expenses and other current liabilities on the condensed consolidated balance sheets. Other Incentives Other incentives that the Company offers include voluntary patient assistance programs, such as the co-pay assistance program, which are intended to provide financial assistance to qualified commercially insured patients with prescription drug co-payments required by payers. The calculation of the accrual for co-pay assistance is based on an estimate of claims and the cost per claim that the Company expects to receive associated with product that has been recognized as revenue, but remains in the distribution channel inventories at the end of each reporting period. The adjustments are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability that is included as a component of accrued expenses and other current liabilities on the condensed consolidated balance sheets. To date, the Company’s only source of product revenue has been from the U.S. sales of ZILRETTA, which it began shipping to customers in October 2017.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and judgments that may affect the reported amounts of assets and liabilities, revenue and expenses, and related disclosures. The Company bases estimates and judgments on historical experience and on various other factors that it believes to be reasonable under the circumstances. The most significant estimates in these condensed consolidated financial statements include estimates related to revenue recognition and accrued expenses related to preclinical and clinical development costs. The Company’s actual results may differ from these estimates under different assumptions or conditions. The Company evaluates its estimates on an ongoing basis. Changes in estimates are reflected in reported results in the period in which they become known by the Company’s management. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations, and financial condition, including sales, expenses, reserves and allowances, clinical trials, research and development expenses, and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat it, as well as the economic impact on local, regional, national, and international customers and markets. The Company has made estimates of the impact of COVID-19 within its financial statements, and there may be changes to those estimates in future periods.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation and amortization expense is recognized using the straight-line method over the following estimated useful lives: Estimated Computers, office equipment, and minor computer software 3 Computer software 7 Manufacturing equipment 7 - 10 Furniture and fixtures 5 Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. Costs of major additions and improvements are capitalized and depreciated on a straight-line basis over their useful lives. Repairs and maintenance costs are expensed as incurred. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is credited or charged to income. Property and equipment includes construction-in-progress that is not yet in service.
Foreign Currencies	Foreign Currencies The Company maintains a bank account denominated in British Pounds. All foreign currency payables and cash balances are measured at the applicable exchange rate at the end of the reporting period. All associated gains and losses from foreign currency transactions are reflected in the consolidated statements of operations.
Leases	Leases The Company determines if an arrangement is a lease at contract inception. Operating lease assets represent a right to use an underlying asset for the lease term and operating lease liabilities represent an obligation to make lease payments arising from the lease. Operating lease liabilities with a term greater than one year and their corresponding right-of-use assets are recognized on the balance sheet at the commencement date of the lease based on the present value of lease payments over the expected lease term. Certain adjustments to the right-of-use asset may be required for items such as initial direct costs paid or incentives received. The Company made an accounting policy election to expense leases with a term of one year or less on a straight-line basis over the lease term. To date, the Company has not identified any material short-term leases, either individually or in the aggregate. As the Company’s leases do not provide an implicit rate, the Company utilized the appropriate incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. The Company estimated the incremental borrowing rate based on a yield curve analysis of companies with a similar credit rating to its own, which was calculated using a number of financial ratios and qualitative considerations of the Company’s business. The yields on the Company’s currently outstanding debt (the convertible senior notes and term loan described below) were also used as inputs to the analysis to calculate a spread, adjusted for factors that reflect the profile of secured borrowing over the expected term of the lease. The components of a lease should be split into three categories: lease components ( e.g. , land, building, etc.), non-lease components ( e.g. , common area maintenance, utilities, performance of manufacturing services, purchase of inventory, etc.), and non-components ( e.g. , property taxes, insurance, etc.). Then the fixed contract consideration (including any related to non-components) must be allocated based on fair values to the lease components and non-lease components. Although separation of lease and non-lease components is required, certain practical expedients are available to entities. Entities electing the practical expedient would not separate lease and non-lease components. Rather, they would account for each lease component and the related non-lease component together as a single component. The Company has elected to use this practical expedient for its real estate leases and account for each lease component and related non-lease component as one single component. In contrast, the Company has elected not to apply the practical expedient for its lease of manufacturing space at Patheon and has instead allocated consideration between the lease and non-lease components of the contract. The Company calculated the fair value of the lease component using publicly available information to identify comparable rentals in the same geographic area. The remainder of the consideration was allocated to the non-lease components.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Product Revenue Allowance And Reserve Categories	The following table summarizes activity in each of the product revenue allowance and reserve categories for the six months ended June 30, 2021 and 2020: (In thousands) Service Fees, Government Product Returns Purchaser/ Provider Discounts and Rebates Total Balance as of December 31, 2020 $ 1,733 $ 530 $ 628 $ 1,832 $ 4,723 Provision related to sales in the current quarter 2,188 383 151 2,703 5,425 Credits and payments made ( 1,969 ) ( 266 ) ( 9 ) ( 1,832 ) ( 4,076 ) Adjustments related to prior period sales — — ( 111 ) — ( 111 ) Balance as of March 31, 2021 1,952 647 659 2,703 5,961 Provision related to sales in the current quarter 2,682 424 179 3,100 6,385 Credits and payments made ( 2,527 ) ( 311 ) ( 86 ) ( 2,711 ) ( 5,635 ) Adjustments related to prior period sales ( 10 ) — — — ( 10 ) Balance as of June 30, 2021 $ 2,097 $ 760 $ 752 $ 3,092 $ 6,701 Balance as of December 31, 2019 $ 1,847 $ 248 $ 402 $ 1,656 $ 4,153 Provision related to sales in the current quarter 1,590 254 114 526 2,484 Credits and payments made ( 1,852 ) ( 199 ) ( 10 ) ( 1,656 ) ( 3,717 ) Adjustments related to prior period sales — 95 — — 95 Balance as of March 31, 2020 1,585 398 506 526 3,015 Provision related to sales in the current quarter 1,417 133 98 892 2,540 Credits and payments made ( 1,172 ) ( 262 ) ( 1 ) ( 528 ) ( 1,963 ) Adjustments related to prior period sales — 90 2 92 Balance as of June 30, 2020 $ 1,830 $ 359 $ 603 $ 892 $ 3,684
Property Plant and Equipment Estimated Useful Lives	Property and equipment are stated at cost less accumulated depreciation. Depreciation and amortization expense is recognized using the straight-line method over the following estimated useful lives: Estimated Computers, office equipment, and minor computer software 3 Computer software 7 Manufacturing equipment 7 - 10 Furniture and fixtures 5

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Assets Measured at Fair Value on Recurring Basis	The following tables present information about the Company’s assets that are measured at fair value on a recurring basis as of June 30, 2021 and December 31, 2020, and indicate the level of the fair value hierarchy utilized to determine such fair value: Fair Value Measurements as of June 30, 2021 Using: (In thousands) Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 90,169 $ — $ — $ 90,169 Marketable securities — 23,620 — 23,620 $ 90,169 $ 23,620 $ — $ 113,789 Fair Value Measurements as of December 31, 2020 Using: (In thousands) Level 1 Level 2 Level 3 Total Assets: Cash equivalents $ 79,148 $ 6,832 $ — $ 85,980 Marketable securities — 67,576 — 67,576 $ 79,148 $ 74,408 $ — $ 153,556

Marketable Securities (Tables)

Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2021
Investments Debt And Equity Securities [Abstract]
Summary of Fair Value of Available-for-Sale Marketable Securities by Type of Security	As of June 30, 2021 and December 31, 2020, the fair value of available-for-sale marketable securities by type of security was as follows: June 30, 2021 (In thousands) Amortized Cost Gross Unrealized Gross Unrealized Fair Value Commercial paper $ 6,397 $ — $ — $ 6,397 Corporate bonds 17,225 — ( 2 ) $ 17,223 $ 23,622 $ — $ ( 2 ) $ 23,620 December 31, 2020 (In thousands) Amortized Cost Gross Unrealized Gross Unrealized Fair Value Commercial paper $ 6,890 $ — $ — $ 6,890 U.S. government obligations 9,997 1 — 9,998 Corporate bonds 50,700 2 ( 14 ) 50,688 $ 67,587 $ 3 $ ( 14 ) $ 67,576

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	6 Months Ended
	Jun. 30, 2021
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following as of June 30, 2021, and December 31, 2020: (In thousands) June 30, December 31, Prepaid expenses $ 4,756 $ 4,346 Deposits 176 112 Interest receivable on marketable securities 134 246 Other 408 408 Total prepaid expenses and other current assets $ 5,474 $ 5,112

Inventory (Tables)

Inventory (Tables)	6 Months Ended
	Jun. 30, 2021
Inventory Disclosure [Abstract]
Schedule of Inventory	Inventory consisted of the following as of June 30, 2021, and December 31, 2020: (In thousands) June 30, December 31, Raw materials $ 3,573 $ 4,287 Work in process 4,992 4,666 Finished goods 3,736 6,441 Total inventories $ 12,301 $ 15,394

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	6 Months Ended
	Jun. 30, 2021
Property Plant And Equipment [Abstract]
Components of Property and Equipment	Property and equipment, net, as of June 30, 2021, and December 31, 2020, consisted of the following: (In thousands) June 30, December 31, Computer and office equipment $ 1,215 $ 1,203 Manufacturing equipment 12,524 12,297 Furniture and fixtures 609 609 Software 495 495 Leasehold improvements 1,177 1,157 Construction in progress 14,956 13,924 30,976 29,685 Less: Accumulated depreciation ( 11,193 ) ( 10,147 ) Total property and equipment, net $ 19,783 $ 19,538

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	6 Months Ended
	Jun. 30, 2021
Payables And Accruals [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following as of June 30, 2021, and December 31, 2020: (In thousands) June 30, December 31, Research and development $ 2,267 $ 1,856 Payroll and other employee-related expenses 9,192 10,674 Professional services fees 2,873 2,094 Accrued interest 1,411 1,464 Product revenue reserves 4,604 2,990 Other 1,005 930 Total accrued expenses and other current liabilities $ 21,352 $ 20,008

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Schedule of Annual Principal and Interest Payments Due Under Term Loan	As of June 30, 2021, annual principal and interest payments due under the term loan were as follows: Year Aggregate (in thousands) 2021 10,605 2022 20,296 2023 19,088 2024 5,249 Thereafter — Total $ 55,238 Less interest ( 4,164 ) Less unamortized portion of final payment ( 2,339 ) Total $ 48,735
Summary of Carrying Value of Convertible Notes	The table below summarizes the carrying value of the 2024 Convertible Notes as of June 30, 2021: ( in thousands ) Gross proceeds $ 201,250 Portion of proceeds allocated to equity component (additional ( 64,541 ) Debt issuance costs ( 6,470 ) Portion of issuance costs allocated to equity component 2,075 Amortization of debt discount and debt issuance costs 35,500 Carrying value 2024 Convertible Notes $ 167,814

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Relevant Data Used to Estimate Fair Value of Stock Option Grants	The relevant data used to determine the value of the stock option grants for the three and six months ended June 30, 2021 and 2020, were as follows: Three months ended Six months ended June 30, June 30, 2021 2020 2021 2020 Risk-free interest rates 1.26 - 1.28 % 0.51 - 0.56 % 1.12 - 1.28 % 0.51 - 1.79 % Expected dividend yield 0.00 % 0.00 % 0.00 % 0.00 % Expected term (in years) 6.0 6.0 6.0 6.0 Expected volatility 71.9 - 72.2 % 70.3 - 72.3 % 71.9 - 72.4 % 65.4 - 72.3 %
Summary of Stock Option Activity	The following table summarizes stock option activity for the six months ended June 30, 2021: (In thousands, except per share amounts) Shares Issuable Options Weighted Average Price Outstanding as of December 31, 2020 4,592 $ 17.77 Granted 350 9.55 Exercised ( 43 ) 3.40 Cancelled ( 522 ) 18.42 Outstanding as of June 30, 2021 4,377 $ 17.18 Options vested and expected to vest at June 30, 2021 4,377 $ 17.18 Options exercisable at June 30, 2021 3,480 $ 18.12
Summary of of RSU Activity	The following table summarizes the RSU activity for the six months ended June 30, 2021: (In thousands, except per share amounts) Number of Weighted Nonvested balance as of December 31, 2020 2,193 $ 14.15 Granted 1,098 9.73 Vested/Released ( 419 ) 15.22 Cancelled ( 434 ) 13.44 Nonvested Balance as of June 30, 2021 2,438 $ 12.10
Stock-Based Compensation Expense Related to Stock Options, and RSUs and Shares Purchased Under Employee Stock Purchase Plan	The Company recorded stock-based compensation expense related to stock options and RSUs and shares purchased under the Employee Stock Purchase Plan for the three and six months ended June 30, 2021 and 2020, as follows: For the three months For the six months (In thousands) 2021 2020 2021 2020 Research and development $ 1,024 $ 1,087 $ 2,303 $ 3,289 Selling, general and administrative 2,951 2,700 6,312 5,149 Total $ 3,975 $ 3,787 $ 8,615 $ 8,438

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders	Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the three and six months ended June 30, 2021 and 2020: For the three months For the six months (In thousands, except per share amounts) 2021 2020 2021 2020 Numerator: Net loss $ ( 22,208 ) $ ( 32,619 ) $ ( 50,764 ) $ ( 69,421 ) Net loss: $ ( 22,208 ) $ ( 32,619 ) $ ( 50,764 ) $ ( 69,421 ) Denominator: Weighted average common shares 49,968 42,776 49,905 40,664 Net loss per share, basic and diluted $ ( 0.44 ) $ ( 0.76 ) $ ( 1.02 ) $ ( 1.71 )
Schedule of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share, as Including them Would have Anti-dilutive Effect	The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated as including them would have an anti-dilutive effect: For the three months For the six months (In thousands) 2021 2020 2021 2020 Shares issuable upon conversion of the 7,515 7,515 7,515 7,515 Stock options 4,401 4,987 4,530 4,925 Restricted stock units 2,618 1,479 2,376 1,196 Total 14,534 13,981 14,421 13,636

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Components of Lease Expense and Related Cash Flows	The components of lease expense and related cash flows were as follows: (In thousands) For the three months For the six months Operating lease cost 2021 2020 2021 2020 Operating lease cost included in operating expenses $ 514 $ 514 $ 1,027 $ 1,027 Operating lease cost included in inventory 62 55 124 113 Total operating lease cost 576 569 1,151 1,140 Operating cash flows from operating leases 809 739 1,595 1,557
Schedule of Maturities of Lease Liability Due Under Lease Agreements	Maturities of lease liability due under these lease agreements as of June 30, 2021, were as follows: Year Operating Lease Obligations (In thousands) 2021 1,027 2022 2,093 2023 2,148 2024 1,981 2025 816 Thereafter 433 Present value of imputed interest ( 2,211 ) Total $ 6,287

Overview and Nature of the Bu_2

Overview and Nature of the Business - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Incorporation date	Nov. 5, 2007
Cash and cash equivalents and marketable securities	$ 131.2

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 30, 2020	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Summary Of Significant Accounting Policies [Line Items]
License agreement upfront payment.	$ 10,000
Revenue			$ 0
Aggregate development, regulatory and commercial sales milestone payments	$ 32,500
Collaborative agreements term related to obligation and rights	terminate the agreement prior to expiration in the event of a material breach if not cured within 60 days from the date of notice of such breach (30 days in the case of payment obligations), or either party files for bankruptcy.
Collaborative arrangement proceeds from upfront payment received		$ 5,000		$ 5,000
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Trade payment term			1 year

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Product Revenue Allowance And Reserve Categories (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020
Service Fees, Allowances and Chargebacks [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	$ 1,952	$ 1,733	$ 1,585	$ 1,847
Provision related to sales in the current quarter	2,682	2,188	1,417	1,590
Credits and payments made	(2,527)	(1,969)	(1,172)	(1,852)
Adjustments related to prior period sales	(10)
Ending Balance	2,097	1,952	1,830	1,585
Government Rebates and Other Incentives [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	647	530	398	248
Provision related to sales in the current quarter	424	383	133	254
Credits and payments made	(311)	(266)	(262)	(199)
Adjustments related to prior period sales			90	95
Ending Balance	760	647	359	398
Product Returns [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	659	628	506	402
Provision related to sales in the current quarter	179	151	98	114
Credits and payments made	(86)	(9)	(1)	(10)
Adjustments related to prior period sales		(111)
Ending Balance	752	659	603	506
Purchaser/Provider Discounts and Rebates [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	2,703	1,832	526	1,656
Provision related to sales in the current quarter	3,100	2,703	892	526
Credits and payments made	(2,711)	(1,832)	(528)	(1,656)
Adjustments related to prior period sales			2
Ending Balance	3,092	2,703	892	526
Product Revenue Allowance and Reserve [Member]
Summary Of Significant Accounting Policies [Line Items]
Beginning Balance	5,961	4,723	3,015	4,153
Provision related to sales in the current quarter	6,385	5,425	2,540	2,484
Credits and payments made	(5,635)	(4,076)	(1,963)	(3,717)
Adjustments related to prior period sales	(10)	(111)	92	95
Ending Balance	$ 6,701	$ 5,961	$ 3,684	$ 3,015

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Property Plant and Equipment Estimated Useful Lives (Detail)	6 Months Ended
	Jun. 30, 2021
Computers, Office Equipment, and Minor Computer Software [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (Years)	3 years
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (Years)	7 years
Manufacturing Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (Years)	7 years
Manufacturing Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (Years)	10 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life (Years)	5 years

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Schedule of Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 23,620	$ 67,576
Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	90,169	85,980
Marketable securities	23,620	67,576
Assets, Total	113,789	153,556
Fair Value Measurements, Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	90,169	79,148
Marketable securities	0	0
Assets, Total	90,169	79,148
Fair Value Measurements, Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	6,832
Marketable securities	23,620	67,576
Assets, Total	23,620	74,408
Fair Value Measurements, Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Marketable securities	0	0
Assets, Total	$ 0	$ 0

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - 2024 Convertible Notes [Member] - USD ($) $ in Millions	Jun. 30, 2021	May 02, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fair value of liability		$ 136.7
Unamortized debt discount		$ 64.5
Debt instrument interest rate	3.375%	3.375%
Term loan, principal amount		$ 201.3
Estimated fair value of Convertible Notes	$ 183.9

Marketable Securities - Summary

Marketable Securities - Summary of Fair Value of Available-for-Sale Marketable Securities by Type of Security (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 23,622	$ 67,587
Gross Unrealized Gains		3
Gross Unrealized Losses	(2)	(14)
Fair Value	23,620	67,576
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,397	6,890
Fair Value	6,397	6,890
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,225	50,700
Gross Unrealized Gains		2
Gross Unrealized Losses	(2)	(14)
Fair Value	$ 17,223	50,688
U.S. Government Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		9,997
Gross Unrealized Gains		1
Fair Value		$ 9,998

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Marketable securities	$ 23,620	$ 23,620	$ 67,576
Long-term investment, marketable securities	0	0	$ 0
Impairment for available-for-sale marketable securities	$ 0	$ 0

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid expenses	$ 4,756	$ 4,346
Deposits	176	112
Interest receivable on marketable securities	134	246
Other	408	408
Total prepaid expenses and other current assets	$ 5,474	$ 5,112

Inventory - Schedule of Invento

Inventory - Schedule of Inventory (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 3,573	$ 4,287
Work in process	4,992	4,666
Finished goods	3,736	6,441
Total inventories	$ 12,301	$ 15,394

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021	Jun. 30, 2020
Inventory [Line Items]
Inventory finished goods shelf life		24 months
Provision for inventory	$ 100	$ 560	$ 0
Product [Member] | United Kingdom Facility at Patheon UK Limited [Member]
Inventory [Line Items]
Cost of sales expense for unabsorbed manufacturing and overhead costs	$ 2,100	$ 5,200

Property and Equipment, Net - C

Property and Equipment, Net - Components of Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment gross	$ 30,976	$ 29,685
Less: Accumulated depreciation	(11,193)	(10,147)
Total property and equipment, net	19,783	19,538
Computer and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	1,215	1,203
Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	12,524	12,297
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	609	609
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	1,177	1,157
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	14,956	13,924
Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment gross	$ 495	$ 495

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020Equipment	Jun. 30, 2021USD ($)Equipment	Jun. 30, 2020USD ($)
Property Plant And Equipment [Abstract]
Depreciation	$ 500	$ 600		$ 1,046	$ 751
Property and equipment disposals | Equipment			1	0
Gains losses on disposals of property plant and equipment				$ (300)

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Research and development	$ 2,267	$ 1,856
Payroll and other employee-related expenses	9,192	10,674
Professional services fees	2,873	2,094
Accrued interest	1,411	1,464
Product revenue reserves	4,604	2,990
Other	1,005	930
Total accrued expenses and other current liabilities	$ 21,352	$ 20,008

Debt - Additional Information (

Debt - Additional Information (Detail) $ / shares in Units, $ in Thousands	May 18, 2020USD ($)	Aug. 02, 2019USD ($)	May 02, 2017USD ($)	Jun. 30, 2021USD ($)$ / shares	Jun. 30, 2021USD ($)TradingDay$ / sharesshares	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Aug. 04, 2015USD ($)
Debt Instrument [Line Items]
Long-term debt, net				$ 52,207	$ 52,207		$ 44,114
Repayments of lines of credit					0	$ 15,000
Amount borrowed					$ 0	$ 15,000
Interest on final payment				6.75%	6.75%
Carrying value of term loan				$ 48,700	$ 48,700
Current portion of long-term debt				$ 1,528	$ 1,528		$ 16,806
Repaid In Year One [Member]
Debt Instrument [Line Items]
Debt instrument interest rate				3.00%	3.00%
Repaid In Year Two [Member]
Debt Instrument [Line Items]
Debt instrument interest rate				2.00%	2.00%
Repaid In Year Three [Member]
Debt Instrument [Line Items]
Debt instrument interest rate				1.00%	1.00%
Repaid In Year Three And Thereafter [Member]
Debt Instrument [Line Items]
Debt instrument interest rate				0.00%	0.00%
2015 Term Loan [Member]
Debt Instrument [Line Items]
Repayments of lines of credit					$ 7,700
Carrying value of term loan				$ 48,735	48,735
Liability component of Convertible Notes recorded as long-term debt				55,238	55,238
Mid Cap Financial Trust [Member] | 2015 Term Loan [Member]
Debt Instrument [Line Items]
Term loan, maximum borrowings								$ 30,000
Long-term debt, net				47,200	47,200
Silicon Valley Bank [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Term loan, maximum borrowings		$ 20,000
Repayments of lines of credit	$ 15,000
Minimum liquidity threshold					$ 80,000
Minimum liquidity threshold, percentage					100.00%
Debt instrument interest rate description					Borrowings under the revolving credit facility accrue interest monthly at a floating interest rate equal to the greater of the prime rate or 5.50% per annum
Unused portion of revolving line, percentage					0.25%
Drew down amount from credit facilities		20,000
Line of credit facility, fee description					unused revolving line facility fee equal to 0.25% per annum of the average unused portion of the revolving line, multiplied by the difference between the total amount available to be borrowed (the “Revolving Commitment Amount”) and the greater of the average outstanding revolver balance and 25% of the Revolving Commitment Amount
Line of credit facility, minimum interest calculation as a percentage of revolving commitment amount					25.00%
Revolving credit facility and any related fees, description					Beginning on January 1, 2020, if the interest payment on the revolving credit facility is less than the amount of interest that would have been payable had the Company borrowed 25% of the Revolving Commitment Amount, then the Company will be required to pay the difference.
Silicon Valley Bank [Member] | Revolving Credit Facility [Member] | Repaid In Year One [Member]
Debt Instrument [Line Items]
Line of credit facility, termination fees, percentage					2.00%
Silicon Valley Bank [Member] | Revolving Credit Facility [Member] | Repaid In Year Two [Member]
Debt Instrument [Line Items]
Line of credit facility, termination fees, percentage					1.00%
Silicon Valley Bank [Member] | Revolving Credit Facility [Member] | Repaid In Year Three And Thereafter [Member]
Debt Instrument [Line Items]
Line of credit facility, termination fees, percentage					0.00%
Silicon Valley Bank [Member] | 2015 Term Loan [Member]
Debt Instrument [Line Items]
Long-term debt, net				$ 40,000	$ 40,000
Silicon Valley Bank [Member] | 2019 Term Loan [Member]
Debt Instrument [Line Items]
Term loan, principal amount		$ 40,000
Debt instrument maturity date					Jan. 1, 2024
Debt instrument interest rate description					Term loan borrowings under the credit facility accrue interest monthly at a floating interest rate equal to the greater of the prime rate plus 1.5% or 6.5% per annum
Term loan, first periodic payment date		Feb. 1, 2021
Interest on final payment				6.75%	6.75%
Term loan, payment description					interest-only period of 18 months, principal is due in 36 equal monthly installments
Silicon Valley Bank [Member] | 2019 Term Loan [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Repayments of lines of credit	15,000
Term loan, maximum borrowings	20,000
Term loan, remaining borrowings	$ 5,000				$ 5,000
2024 Convertible Notes [Member]
Debt Instrument [Line Items]
Term loan, principal amount			$ 201,300
Debt instrument maturity date			May 1, 2024
Debt instrument interest rate			3.375%	3.375%	3.375%
Debt instrument interest rate			3.375%	9.71%	9.71%
Debt instrument frequency of periodic payment			semi-annually
Net proceeds from offering of convertible senior notes			$ 194,800
Debt discount and issuance costs			6,500	$ 68,900	$ 68,900
Number of shares issued upon conversion of $1,000 debt principal amount | shares					37.3413
Debt instrument convertible initial conversion price per share of common stock | $ / shares				$ 26.78	$ 26.78
Number of days within 30 consecutive trading days in which the closing price of the entity's common stock must exceed the conversion price for the notes to be convertible into common stock | TradingDay					20
Number of consecutive trading days during which the closing price of the entity's common stock must exceed the conversion price for at least 20 days in order for the notes to be convertible into common stock | TradingDay					30
Percentage of the closing sales price of the entity's common stock that the conversion price must exceed in order for the notes to be convertible					130.00%
Number of consecutive business days immediately after any five consecutive trading day period during the note measurement period | TradingDay					5
Number of consecutive trading days before five consecutive business days during the note measurement period | TradingDay					10
Liability component of Convertible Notes recorded as long-term debt			136,700
Equity component of Convertible Notes recorded as additional paid-in capital			$ 64,500
Debt instrument effective interest rate period					7 years
Debt issuance costs					$ 6,500
Debt issuance costs allocated to liability component					4,400
Debt issuance costs allocated to equity component reduction to additional paid-in capital					2,100
Interest expense				$ 4,100	8,100
Amortization of debt discount				$ 2,400	$ 4,700
2024 Convertible Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument conversion obligation trading price as percentage of product common stock closing sale price and conversion rate					98.00%
2024 Convertible Notes [Member] | Repaid In Year Two [Member]
Debt Instrument [Line Items]
Number of days within 30 consecutive trading days in which the closing price of the entity's common stock must exceed the conversion price for the notes to be convertible into common stock | TradingDay					20
Number of consecutive trading days during which the closing price of the entity's common stock must exceed the conversion price for at least 20 days in order for the notes to be convertible into common stock | TradingDay					30
Percentage of the closing sales price of the entity's common stock that the conversion price must exceed in order for the notes to be convertible					130.00%
Debt instrument redemption date					May 6, 2020
Redemption price percentage of principal amount to be redeemed					100.00%

Debt - Schedule of Annual Princ

Debt - Schedule of Annual Principal and Interest Payments Due Under Term Loan (Detail) $ in Thousands	Jun. 30, 2021USD ($)
Long-term Debt, Fiscal Year Maturity [Abstract]
Total	$ 48,700
2015 Term Loan [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
2021	10,605
2022	20,296
2023	19,088
2024	5,249
Thereafter
Total	55,238
Less interest	(4,164)
Less unamortized portion of final payment	(2,339)
Total	$ 48,735

Debt - Summary of Carrying Valu

Debt - Summary of Carrying Value of Convertible Notes (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Debt Instrument [Line Items]
Amortization of debt discount and debt issuance costs	$ 5,028	$ 4,577
Carrying value 2024 Convertible Notes	167,814		$ 162,786
2024 Convertible Notes [Member]
Debt Instrument [Line Items]
Gross proceeds	201,250
Gross proceeds, Portion of proceeds allocated to equity component (additional paid-in capital)	(64,541)
Debt issuance costs	(6,470)
Debt issuance costs, Portion of issuance costs allocated to equity component (additional paid-in capital)	2,075
Amortization of debt discount and debt issuance costs	35,500
Carrying value 2024 Convertible Notes	$ 167,814

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Relevant Data Used to Estimate Fair Value of Stock Option Grants (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rates, Minimum	1.26%	0.51%	1.12%	0.51%
Risk-free interest rates, Maximum	1.28%	0.56%	1.28%	1.79%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected term (in years)	6 years	6 years	6 years	6 years
Expected volatility, Minimum	71.90%	70.30%	71.90%	65.40%
Expected volatility, Maximum	72.20%	72.30%	72.40%	72.30%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Detail)	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Issuable Under Options, Beginning balance | shares	4,592,000
Shares Issuable Under Options, Granted | shares	350,000
Shares Issuable Under Options, Exercised | shares	(42,682)
Shares Issuable Under Options, Cancelled | shares	(522,000)
Shares Issuable Under Options, Ending balance | shares	4,376,841
Shares Issuable Under Options, Options vested and expected to vest at June 30, 2021 | shares	4,377,000
Shares Issuable Under Options, Options exercisable at June 30, 2021 | shares	3,480,000
Weighted Average Exercise Price Per Share, Beginning balance | $ / shares	$ 17.77
Weighted Average Exercise Price Per Share, Granted | $ / shares	9.55
Weighted Average Exercise Price Per Share, Exercised | $ / shares	3.40
Weighted Average Exercise Price Per Share, Cancelled | $ / shares	18.42
Weighted Average Exercise Price Per Share, Ending balance | $ / shares	17.18
Weighted Average Exercise Price Per Share, Options vested and expected to vest at June 30, 2021 | $ / shares	17.18
Weighted Average Exercise Price Per Share, Options exercisable at June 30, 2021 | $ / shares	$ 18.12

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail)	3 Months Ended	6 Months Ended
	Jun. 30, 2021USD ($)$ / sharesshares	Jun. 30, 2021USD ($)Installment$ / sharesshares	Jun. 30, 2020$ / sharesshares	Dec. 31, 2020$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options exercised		42,682
Aggregate intrinsic value of stock options exercised | $		$ 386,138
Options to purchase common stock, outstanding	4,376,841	4,376,841	4,926,718	4,592,000
Weighted average remaining contractual term		5 years 10 months 24 days	6 years 8 months 12 days
Weighted average exercise price | $ / shares	$ 17.18	$ 17.18	$ 17.75	$ 17.77
Weighted average grant date fair value of options granted | $ / shares		$ 6.09	$ 8.94
Unrecognized stock-based compensation expense | $	$ 7,200,000	$ 7,200,000
Unrecognized compensation costs, weighted-average recognition periods		2 years 3 months 18 days
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, number of shares granted		1,097,555
Weighted average grant date fair value, shares granted, per share | $ / shares		$ 9.73
Awards vesting right		RSUs vest in four substantially equal installments on each of the first four anniversaries of the vesting commencement date, subject to the employee’s continued employment with, or services to, the Company on each vesting date
Stock-based compensation expense recognized | $	0	$ 0
Share based compensation award, vested		419,000
Performance achievement conditions percentage related to vesting of shares..		150.00%
Unrecognized stock-based compensation expense | $	$ 23,300,000	$ 23,300,000
Unrecognized compensation costs, weighted-average recognition periods		2 years 4 months 24 days
Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation award, vested		159,150
Restricted Stock Units (RSUs) [Member] | First Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, award vesting installments | Installment		4
Restricted Stock Units (RSUs) [Member] | Second Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, award vesting installments | Installment		4
Restricted Stock Units (RSUs) [Member] | Third Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, award vesting installments | Installment		4
Restricted Stock Units (RSUs) [Member] | Fourth Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, award vesting installments | Installment		4
Restricted Stock Units (RSUs) [Member] | Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation, number of shares granted		106,100

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of of RSU Activity (Detail) - Restricted Stock Units (RSUs) [Member]	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning balance | shares	2,193,000
Number of Shares, Granted | shares	1,097,555
Number of Shares, Vested/Released | shares	(419,000)
Number of Shares, Cancelled | shares	(434,000)
Number of Shares, Ending balance | shares	2,438,000
Weighted Average Grant Date Fair Value Per Share, Beginning balance | $ / shares	$ 14.15
Weighted Average Grant Date Fair Value Per Share, Granted | $ / shares	9.73
Weighted Average Grant Date Fair Value Per Share, Vested/Released | $ / shares	15.22
Weighted Average Grant Date Fair Value Per Share, Cancelled | $ / shares	13.44
Weighted Average Grant Date Fair Value Per Share, Ending balance | $ / shares	$ 12.10

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense Related to Stock Options, and RSUs and Shares Purchased Under Employee Stock Purchase Plan (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3,975	$ 3,787	$ 8,615	$ 8,438
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,024	1,087	2,303	3,289
Selling, General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,951	$ 2,700	$ 6,312	$ 5,149

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net loss	$ (22,208)	$ (28,556)	$ (32,619)	$ (36,802)	$ (50,764)	$ (69,421)
Net loss:	$ (22,208)	$ (28,556)	$ (32,619)	$ (36,802)	$ (50,764)	$ (69,421)
Denominator:
Weighted average common shares outstanding, basic and diluted	49,968		42,776		49,905	40,664
Net loss per share, basic and diluted	$ (0.44)		$ (0.76)		$ (1.02)	$ (1.71)

Net Loss per Share - Schedule_2

Net Loss per Share - Schedule of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share, as Including them Would have Anti-dilutive Effect (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share, as including them would have anti-dilutive effect	14,534	13,981	14,421	13,636
Shares Issuable Upon Conversion of the 2024 Convertible Notes [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share, as including them would have anti-dilutive effect	7,515	7,515	7,515	7,515
Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share, as including them would have anti-dilutive effect	4,401	4,987	4,530	4,925
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share, as including them would have anti-dilutive effect	2,618	1,479	2,376	1,196

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)

Jun. 30, 2019USD ($)ft²

Jan. 31, 2018USD ($)

Feb. 28, 2017USD ($)

Jan. 31, 2016

Jul. 31, 2015

Feb. 28, 2021USD ($)

Nov. 30, 2019USD ($)

Sep. 30, 2019USD ($)

Dec. 31, 2017USD ($)

Jun. 30, 2021USD ($)

Mar. 31, 2021USD ($)

Jun. 30, 2020USD ($)

Mar. 31, 2020USD ($)

Jun. 30, 2021USD ($)

Jun. 30, 2020USD ($)

Feb. 02, 2018

May 31, 2013

Commitment And Contingencies [Line Items]

Operating lease term

42 years

Lease termination date

Apr. 30, 2025

Operating lease, straight-line cost

$ 500,000

Operating lease, remaining lease term

2 years 8 months 12 days

2 years 8 months 12 days

Right-of-Use Asset Obtained in Exchange for Operating Lease Liability

$ 433,000

$ 0

Increase in operating lease liability

728,000

748,000

Milestone payment

$ 1,000,000

Definitive Agreement [Member]

Commitment And Contingencies [Line Items]

Research and development milestone payment

$ 500,000

GeneQuine Biotherapeutics GmbH ("GeneQuine") [Member] | Definitive Agreement [Member]

Commitment And Contingencies [Line Items]

License agreement, upfront fee paid

$ 2,000,000

Milestone, Revenue recognized

0

Research and development milestone payment

$ 750,000

GeneQuine Biotherapeutics GmbH ("GeneQuine") [Member] | Definitive Agreement [Member] | Investigational New Drug

Commitment And Contingencies [Line Items]

Research and development milestone payment

$ 750,000

GeneQuine Biotherapeutics GmbH ("GeneQuine") [Member] | Definitive Agreement [Member] | Maximum [Member]

Commitment And Contingencies [Line Items]

Additional milestone payments

51,500,000

Xenon Pharmaceuticals, Inc. ("Xenon") [Member] | Definitive Agreement [Member]

Commitment And Contingencies [Line Items]

License agreement, upfront fee paid

3,000,000

Milestone, Revenue recognized

0

Xenon Pharmaceuticals, Inc. ("Xenon") [Member] | Definitive Agreement [Member] | Sales Related Milestone Payments [Member]

Commitment And Contingencies [Line Items]

Additional milestone payments

75,000,000

Xenon Pharmaceuticals, Inc. ("Xenon") [Member] | Definitive Agreement [Member] | Maximum [Member]

Commitment And Contingencies [Line Items]

Additional milestone payments

40,800,000

Evonik Corporation [Member]

Commitment And Contingencies [Line Items]

Supply agreement period

5 years

Manufacturing and Supply Agreement with Patheon UK Limited [Member]

Commitment And Contingencies [Line Items]

Operating lease, straight-line cost

$ 62,000,000

$ 55,000,000

$ 124,000,000

$ 113,000,000

Operating lease, remaining lease term

6 years 3 months 18 days

6 years 3 months 18 days

Manufacturing agreement period

10 years

Operating lease, discount rate

6.10%

Increase in right of use asset

$ 500,000

Phase 2 Proof of Concept (PoC) Clinical Trial [Member] | GeneQuine Biotherapeutics GmbH ("GeneQuine") [Member] | Definitive Agreement [Member] | Maximum [Member]

Commitment And Contingencies [Line Items]

Additional milestone payments

$ 4,500,000

Phase 2 Proof of Concept (PoC) Clinical Trial [Member] | Xenon Pharmaceuticals, Inc. ("Xenon") [Member] | Definitive Agreement [Member] | Maximum [Member]

Commitment And Contingencies [Line Items]

Additional milestone payments

$ 5,000,000

Phase1 clinical trial [Member]

Commitment And Contingencies [Line Items]

Additional milestone payments

$ 2,000,000

Milestone payment

2,500,000

Burlington Massachusetts [Member]

Commitment And Contingencies [Line Items]

Operating lease office space | ft²

41,873

Minimum monthly lease payments

$ 108,000,000

Operating lease, straight-line cost

$ 900,000

$ 400,000

$ 900,000

Operating lease, remaining lease term

3 years 9 months 18 days

3 years 9 months 18 days

Lessee, operating lease, extension term

18 months

18 months

Woburn, Massachusetts [Member]

Commitment And Contingencies [Line Items]

Operating lease term

5 years

Lease termination date

Feb. 29, 2024

Minimum monthly lease payments

$ 20,400,000

Operating lease, straight-line cost

$ 46,000,000

$ 92,000,000

Monthly lease payment

$ 15,000,000

Commitments and Contingencies_2

Commitments and Contingencies - Components of Lease Expense and Related Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Commitment And Contingencies [Line Items]
Total operating lease cost	$ 576	$ 569	$ 1,151	$ 1,140
Operating cash flows from operating leases	809	739	1,595	1,557
Inventory [Member]
Commitment And Contingencies [Line Items]
Total operating lease cost	62	55	124	113
Operating Expense [Member]
Commitment And Contingencies [Line Items]
Total operating lease cost	$ 514	$ 514	$ 1,027	$ 1,027

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Maturities of Lease Liability Due Under Lease Agreements (Detail) $ in Thousands	Jun. 30, 2021USD ($)
Commitments And Contingencies Disclosure [Abstract]
Aggregate Minimum Payments, 2021	$ 1,027
Aggregate Minimum Payments, 2022	2,093
Aggregate Minimum Payments, 2023	2,148
Aggregate Minimum Payments, 2024	1,981
Aggregate Minimum Payments, 2025	816
Aggregate Minimum Payments, Thereafter	433
Aggregate Minimum Payments, Present value of imputed interest	2,211
Aggregate Minimum Payments, Total	$ 6,287

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ in Thousands	Jul. 31, 2021	Jun. 30, 2021	Dec. 31, 2020	Aug. 02, 2019
Subsequent Event [Line Items]
Long-term debt, net		$ 52,207	$ 44,114
Interest on final payment		6.75%
Repaid In Year One [Member]
Subsequent Event [Line Items]
Debt instrument interest rate		3.00%
Repaid In Year Two [Member]
Subsequent Event [Line Items]
Debt instrument interest rate		2.00%
Repaid In Year Three [Member]
Subsequent Event [Line Items]
Debt instrument interest rate		1.00%
Repaid In Year Three And Thereafter [Member]
Subsequent Event [Line Items]
Debt instrument interest rate		0.00%
Subsequent Event [Member] | 2021 Amended Credit Agreement [Member]
Subsequent Event [Line Items]
Debt instrument interest rate description	The applicable interest rate under the 2021 Amended Credit Agreement is (a) with respect to the term loan, the greater of (i) the prime rate published by the Wall Street Journal (“Prime Rate”) plus 2.75% or (ii) 6.00%, and (b) with respect to the revolving loan is the greater of (i) the Prime Rate plus 1.75% or (ii) 5.00%.
Interest on final payment	4.75%
Subsequent Event [Member] | 2021 Amended Credit Agreement [Member] | Repaid In Year One [Member]
Subsequent Event [Line Items]
Debt instrument interest rate	3.00%
Subsequent Event [Member] | 2021 Amended Credit Agreement [Member] | Repaid In Year Two [Member]
Subsequent Event [Line Items]
Debt instrument interest rate	2.00%
Subsequent Event [Member] | 2021 Amended Credit Agreement [Member] | Repaid In Year Three [Member]
Subsequent Event [Line Items]
Debt instrument interest rate	1.00%
Subsequent Event [Member] | 2021 Amended Credit Agreement [Member] | Repaid In Year Three And Thereafter [Member]
Subsequent Event [Line Items]
Prepayment fee	$ 0
Silicon Valley Bank [Member] | Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Term loan, maximum borrowings				$ 20,000
Debt instrument interest rate description		Borrowings under the revolving credit facility accrue interest monthly at a floating interest rate equal to the greater of the prime rate or 5.50% per annum
Silicon Valley Bank [Member] | Subsequent Event [Member] | Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Debt instrument maturity date	Feb. 1, 2024
Debt instrument maturity date option to extend	Jul. 1, 2026
Term loan, maximum borrowings	$ 25,000
Repayment of term loan	20,000
Silicon Valley Bank [Member] | Subsequent Event [Member] | 2021 Amended Credit Agreement [Member] | Second Tranche Undrawn [Member]
Subsequent Event [Line Items]
Company liquidity with banks	100,000
Silicon Valley Bank [Member] | Subsequent Event [Member] | 2021 Amended Credit Agreement [Member] | Second Tranche Drawn [Member]
Subsequent Event [Line Items]
Company liquidity with banks	120,000
Silicon Valley Bank [Member] | 2021 Term Loan [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Term loan, principal amount	55,000
Long-term debt, net	55,000
Silicon Valley Bank [Member] | 2021 Term Loan [Member] | Subsequent Event [Member] | Maximum [Member]
Subsequent Event [Line Items]
Term loan, principal amount	75,000
Silicon Valley Bank [Member] | 2021 Term Loan [Member] | Subsequent Event [Member] | Second Tranche [Member]
Subsequent Event [Line Items]
Term loan, principal amount	20,000
Silicon Valley Bank [Member] | 2019 Term Loan [Member]
Subsequent Event [Line Items]
Term loan, principal amount				$ 40,000
Debt instrument maturity date		Jan. 1, 2024
Debt instrument interest rate description		Term loan borrowings under the credit facility accrue interest monthly at a floating interest rate equal to the greater of the prime rate plus 1.5% or 6.5% per annum
Interest on final payment		6.75%
Silicon Valley Bank [Member] | 2019 Term Loan [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Total revolver balance	25,000
Silicon Valley Bank [Member] | 2019 Term Loan [Member] | Subsequent Event [Member] | Revolving Credit Facility [Member]
Subsequent Event [Line Items]
Repayment of term loan	$ 48,100