0001564590-19-028537 | 10-Q | XBRL Viewer | Heron Therapeutics INC DE

Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2019	Jul. 17, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	HRTX
Entity Registrant Name	HERON THERAPEUTICS, INC. /DE/
Entity Central Index Key	0000818033
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		79,816,417
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity File Number	001-33221
Entity Tax Identification Number	94-2875566
Entity Address, Address Line One	4242 Campus Point Court
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	251-4400
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock
Security Exchange Name	NASDAQ
Entity Ex Transition Period	false

Condensed Consolidated Balance Sheets (Current Period Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 53,038	$ 31,836
Short-term investments	222,967	300,535
Accounts receivable, net	66,821	64,652
Inventory	29,270	39,032
Prepaid expenses and other current assets	8,739	11,193
Total current assets	380,835	447,248
Property and equipment, net	17,910	14,677
Right-of-use lease assets	12,667
Other assets	254	254
Total assets	411,666	462,179
Current liabilities:
Accounts payable	7,997	16,863
Accrued clinical and manufacturing liabilities	25,383	24,470
Accrued payroll and employee liabilities	8,982	13,397
Other accrued liabilities	45,891	32,715
Current lease liabilities	1,722
Convertible notes payable to related parties, net of discount	5,081	4,574
Total current liabilities	95,056	92,019
Non-current lease liabilities	11,251
Total liabilities	106,307	92,019
Stockholders’ equity:
Common stock	798	782
Additional paid-in capital	1,378,368	1,330,186
Accumulated other comprehensive income (loss)	148	(87)
Accumulated deficit	(1,073,955)	(960,721)
Total stockholders’ equity	305,359	370,160
Total liabilities and stockholders’ equity	$ 411,666	$ 462,179

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues:
Net product sales	$ 36,659	$ 17,277	$ 68,261	$ 28,844
Operating expenses:
Cost of product sales	13,588	5,231	28,550	8,364
Research and development	41,425	30,159	84,397	69,720
General and administrative	9,778	6,209	19,426	13,237
Sales and marketing	23,647	14,531	52,367	28,366
Total operating expenses	88,438	56,130	184,740	119,687
Loss from operations	(51,779)	(38,853)	(116,479)	(90,843)
Other income (expense), net	1,557	183	3,245	(92)
Net loss	(50,222)	(38,670)	(113,234)	(90,935)
Other comprehensive income (loss):
Unrealized gains (losses) on short-term investments	112	17	235	(15)
Comprehensive loss	$ (50,110)	$ (38,653)	$ (112,999)	$ (90,950)
Basic and diluted net loss per share	$ (0.63)	$ (0.54)	$ (1.43)	$ (1.33)
Shares used in computing basic and diluted net loss per share	79,548	71,952	78,987	68,358

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Balance at Dec. 31, 2017	$ 131,136	$ 646	$ 913,955	$ (10)	$ (783,455)
Balance (in shares) at Dec. 31, 2017		64,609,000
Cumulative effect of adoption of new accounting standard at Dec. 31, 2017	1,573				1,573
Issuance of common stock in public offerings, net	(205)		(205)
Conversion benefit included in Convertible Notes issued	96		96
Issuance of common stock on exercise of stock options	4,202	$ 4	4,198
Issuance of common stock on exercise of stock options (in shares)		435,000
Stock-based compensation expense	7,701		7,701
Net loss	(52,265)				(52,265)
Net unrealized gain (loss) on short-term investments	(32)			(32)
Comprehensive loss	(52,297)
Balance at Mar. 31, 2018	92,206	$ 650	925,745	(42)	(834,147)
Balance (in shares) at Mar. 31, 2018		65,044,000
Cumulative effect of adoption of new accounting standard at Mar. 31, 2018	1				1
Balance at Dec. 31, 2017	131,136	$ 646	913,955	(10)	(783,455)
Balance (in shares) at Dec. 31, 2017		64,609,000
Cumulative effect of adoption of new accounting standard at Dec. 31, 2017	1,573				1,573
Net loss	(90,935)
Net unrealized gain (loss) on short-term investments	(15)
Comprehensive loss	(90,950)
Balance at Jun. 30, 2018	431,891	$ 775	1,303,957	(25)	(872,816)
Balance (in shares) at Jun. 30, 2018		77,560,000
Balance at Mar. 31, 2018	92,206	$ 650	925,745	(42)	(834,147)
Balance (in shares) at Mar. 31, 2018		65,044,000
Cumulative effect of adoption of new accounting standard at Mar. 31, 2018	1				1
Issuance of common stock in public offerings, net	363,332	$ 120	363,212
Issuance of common stock in public offerings, net (in shares)		11,963,000
Conversion benefit included in Convertible Notes issued	97		97
Issuance of common stock on exercise of stock options	6,439	$ 5	6,434
Issuance of common stock on exercise of stock options (in shares)		504,000
Issuance of common stock on under the employee stock purchase plan	648		648
Issuance of common stock on under the Employee Stock Purchase Plan (in shares)		49,000
Stock-based compensation expense	7,821		7,821
Net loss	(38,670)				(38,670)
Net unrealized gain (loss) on short-term investments	17			17
Comprehensive loss	(38,653)
Balance at Jun. 30, 2018	431,891	$ 775	1,303,957	(25)	(872,816)
Balance (in shares) at Jun. 30, 2018		77,560,000
Balance at Dec. 31, 2018	370,160	$ 782	1,330,186	(87)	(960,721)
Balance (in shares) at Dec. 31, 2018		78,174,000
Conversion benefit included in Convertible Notes issued	102		102
Issuance of common stock on exercise of stock options	6,539	$ 7	6,532
Issuance of common stock on exercise of stock options (in shares)		732,000
Stock-based compensation expense	17,902		17,902
Net loss	(63,012)				(63,012)
Net unrealized gain (loss) on short-term investments	123			123
Comprehensive loss	(62,889)
Balance at Mar. 31, 2019	331,814	$ 789	1,354,722	36	(1,023,733)
Balance (in shares) at Mar. 31, 2019		78,906,000
Balance at Dec. 31, 2018	$ 370,160	$ 782	1,330,186	(87)	(960,721)
Balance (in shares) at Dec. 31, 2018		78,174,000
Issuance of common stock on exercise of stock options (in shares)	1,542,000
Net loss	$ (113,234)
Net unrealized gain (loss) on short-term investments	235
Comprehensive loss	(112,999)
Balance at Jun. 30, 2019	305,359	$ 798	1,378,368	148	(1,073,955)
Balance (in shares) at Jun. 30, 2019		79,779,000
Balance at Mar. 31, 2019	331,814	$ 789	1,354,722	36	(1,023,733)
Balance (in shares) at Mar. 31, 2019		78,906,000
Conversion benefit included in Convertible Notes issued	103		103
Issuance of common stock on exercise of stock options	9,676	$ 8	9,668
Issuance of common stock on exercise of stock options (in shares)		810,000
Issuance of common stock on under the employee stock purchase plan	1,170	$ 1	1,169
Issuance of common stock on under the Employee Stock Purchase Plan (in shares)		63,000
Stock-based compensation expense	12,706		12,706
Net loss	(50,222)				(50,222)
Net unrealized gain (loss) on short-term investments	112			112
Comprehensive loss	(50,110)
Balance at Jun. 30, 2019	$ 305,359	$ 798	$ 1,378,368	$ 148	$ (1,073,955)
Balance (in shares) at Jun. 30, 2019		79,779,000

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities:
Net loss	$ (113,234,000)	$ (90,935,000)
Adjustments to reconcile net loss to net cash used for operating activities:
Stock-based compensation expense	30,608,000	15,522,000
Depreciation and amortization	959,000	711,000
Amortization of debt discount	507,000	428,000
Realized gain on short-term investments	(8,000)	0
Accretion of discount on short-term investments	(2,437,000)	(864,000)
Impairment on property and equipment	54,000
Loss on disposal of property and equipment	53,000	3,000
Change in operating assets and liabilities:
Accounts receivable	(2,169,000)	(4,012,000)
Prepaid expenses and other assets	2,454,000	(3,039,000)
Inventory	9,762,000	(17,287,000)
Accounts payable	(8,866,000)	(13,790,000)
Accrued clinical and manufacturing liabilities	913,000	(8,934,000)
Accrued payroll and employee liabilities	(4,415,000)	(1,974,000)
Other accrued liabilities	13,687,000	1,729,000
Net cash used for operating activities	(72,132,000)	(122,442,000)
Investing activities:
Purchases of short-term investments	(204,358,000)	(157,885,000)
Maturities and sales of short-term investments	284,606,000	22,500,000
Purchases of property and equipment	(4,299,000)	(2,238,000)
Net cash provided by (used for) investing activities	75,949,000	(137,623,000)
Financing activities:
Net proceeds from sale of common stock		363,127,000
Proceeds from stock option exercises	16,215,000	10,641,000
Proceeds from purchases under the Employee Stock Purchase Plan	1,170,000	648,000
Net cash provided by financing activities	17,385,000	374,416,000
Net increase in cash and cash equivalents	21,202,000	114,351,000
Cash and cash equivalents at beginning of year	31,836,000	144,583,000
Cash and cash equivalents at end of period	$ 53,038,000	258,934,000
Supplemental disclosure of cash flow information:
Interest paid		1,000,000
Cumulative effect of adoption of new accounting standard		$ 1,574,000

Business

6 Months Ended

Jun. 30, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Business

1. Business

We are a commercial-stage biotechnology company focused on improving the lives of patients by developing best-in-class treatments to address some of the most important unmet patient needs. We are developing novel, patient-focused solutions that apply our innovative science and technologies to already-approved pharmacological agents for patients suffering from pain or cancer.

On August 9, 2016, our first commercial product, SUSTOL (granisetron) extended-release injection (“SUSTOL”), was approved by the U.S. Food and Drug Administration (“FDA”). SUSTOL is indicated in combination with other antiemetics in adults for the prevention of acute and delayed nausea and vomiting associated with initial and repeat courses of moderately emetogenic chemotherapy (MEC) or anthracycline and cyclophosphamide (AC) combination chemotherapy regimens. SUSTOL is an extended-release, injectable 5-hydroxytryptamine type 3 receptor antagonist that utilizes Heron’s proprietary Biochronomer drug delivery technology (“Biochronomer Technology”) to maintain therapeutic levels of granisetron for ≥5 days. We commenced commercial sales of SUSTOL in the U.S. in October 2016.

On November 9, 2017, our second commercial product, CINVANTI (aprepitant) injectable emulsion (“CINVANTI”), was approved by the FDA. CINVANTI, in combination with other antiemetic agents, is indicated in adults for the prevention of acute and delayed nausea and vomiting associated with initial and repeat courses of highly emetogenic cancer chemotherapy (HEC) including high-dose cisplatin and nausea and vomiting associated with initial and repeat courses of moderately emetogenic cancer chemotherapy (MEC). CINVANTI is an intravenous (“IV”) formulation of aprepitant, a substance P/neurokinin-1 (“NK₁”) receptor antagonist. CINVANTI is the only IV formulation of an NK₁ receptor antagonist indicated for the prevention of acute and delayed nausea and vomiting associated with HEC and nausea and vomiting associated with MEC that is free of polysorbate 80 or any other synthetic surfactant. We commenced commercial sales of CINVANTI in the U.S. in January 2018. On February 26, 2019, we announced that the FDA approved our supplemental New Drug Application (“sNDA”) for CINVANTI, for IV use, which expanded the administration of CINVANTI beyond the initially approved administration method (a 30-minute IV infusion) to include a 2-minute IV injection.

HTX-011, which utilizes Heron’s proprietary Biochronomer Technology, is an investigational, long-acting, extended-release formulation of the local anesthetic bupivacaine in a fixed-dose combination with the anti-inflammatory meloxicam for postoperative pain management. By delivering sustained levels of both a potent anesthetic and a local anti-inflammatory agent directly to the site of tissue injury, HTX-011 was designed to deliver superior pain relief while reducing the need for systemically administered pain medications such as opioids, which carry the risk of harmful side effects, abuse and addiction. HTX-011 has been shown to reduce pain significantly better than placebo or bupivacaine alone in five diverse surgical models: hernia repair, abdominoplasty, bunionectomy, total knee arthroplasty and breast augmentation. HTX-011 was granted Fast Track designation from the FDA in the fourth quarter of 2017 and Breakthrough Therapy designation in the second quarter of 2018. We submitted a New Drug Application (“NDA”) for HTX-011 to the FDA in October of 2018 and received Priority Review designation in December of 2018. A Complete Response Letter (“CRL”) was received from the FDA regarding the NDA for HTX-011 on April 30, 2019. The CRL stated that the FDA was unable to approve the NDA in its present form based on the need for additional Chemistry, Manufacturing and Controls (“CMC”) and non-clinical information. Based on the complete review of the NDA, the FDA did not identify any clinical safety or efficacy issues, and there was no requirement for further clinical studies or data analyses. In April 2019, we announced that the Marketing Authorisation Application (“MAA”) for HTX-011 was validated by the European Medicines Agency (“EMA”). Validation of the MAA confirms that the submission is complete and starts the EMA's Centralised Procedure. The EMA granted eligibility to the Centralised Procedure for HTX-011 based on it meeting the criteria of a medicinal product constituting a significant scientific innovation. The Centralised Procedure allows applicants to receive a marketing authorisation that is valid throughout the European Union. An opinion from the EMA Committee for Medicinal Products for Human Use (CHMP) is anticipated in the first half of 2020.

HTX-034, our next generation product candidate for postoperative pain management, is in development for postoperative pain via local application. Based on the positive results of preclinical studies in which HTX-034 demonstrated significant pain reduction for seven days, we have initiated formal development of this next-generation postoperative pain management product candidate.

As of June 30, 2019 we had $276.0 million in cash, cash equivalents and short-term investments. We have incurred significant operating losses and negative cash flows from operations. Management believes that cash, cash equivalents and short-term investments as of June 30, 2019 will be sufficient to fund operations for at least one year from the date this Quarterly Report on Form 10-Q is filed with the U.S. Securities and Exchange Commission (“SEC”).

Basis of Presentation

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Basis of Presentation

2. Basis of Presentation

The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the U.S. (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three and six months ended June 30, 2019 are not necessarily indicative of the results that may be expected for other quarters or the year ending December 31, 2019. The condensed consolidated balance sheet as of December 31, 2018 has been derived from the audited financial statements as of that date, but does not include all of the information and disclosures required by GAAP. For more complete financial information, these unaudited condensed consolidated financial statements and the notes thereto should be read in conjunction with the audited financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2018, which was filed with the SEC on February 22, 2019.

Accounting Policies

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Accounting Policies

3. Accounting Policies

Principles of Consolidation

The accompanying unaudited condensed consolidated financial statements include the accounts of Heron Therapeutics, Inc. and its wholly-owned subsidiary, Heron Therapeutics B.V., which was organized in the Netherlands in March 2015. Heron Therapeutics B.V. has no operations and no material assets or liabilities, and there have been no significant transactions related to Heron Therapeutics B.V. since its inception.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and disclosures made in the accompanying notes to the financial statements. Our significant accounting policies that involve significant judgment and estimates include revenue recognition, inventory and the related reserves, accrued clinical liabilities, income taxes and stock-based compensation. Actual results could differ materially from those estimates.

Cash, Cash Equivalents and Short-term Investments

Cash and cash equivalents consist of cash and highly liquid investments with contractual maturities of three months or less from the original purchase date.

Short-term investments consist of securities with contractual maturities of greater than three months to one year from the original purchase date. We have classified our short-term investments as available-for-sale securities in the accompanying unaudited condensed consolidated financial statements. Available-for-sale securities are stated at fair market value, with net changes in unrealized gains and losses reported in other comprehensive loss and realized gains and losses included in other income (expense), net. The cost of securities sold is based on the specific-identification method. Interest and dividends on securities classified as available-for-sale are included in interest income.

Our bank and investment accounts have been placed under a control agreement in accordance with our Senior Secured Convertible Notes (“Convertible Notes”) (see Note 8).

Concentration of Credit Risk

Cash, cash equivalents and short-term investments are financial instruments that potentially subject us to concentrations of credit risk. We deposit our cash in financial institutions. At times, such deposits may be in excess of insured limits. We may also invest our excess cash in money market funds, U.S. government and agencies, corporate debt securities and commercial paper. We have established guidelines relative to our diversification of our cash investments and their maturities in an effort to maintain safety and liquidity. These guidelines are periodically reviewed and modified to take advantage of trends in yields and interest rates.

Our products are distributed in the U.S. through a limited number of specialty distributors and full line wholesalers (collectively, “Customers”) that resell our products to healthcare providers and hospitals, the end users.

The following table includes the percentage of net product sales and accounts receivable balances for our three major Customers, each of which comprised 10% or more of our net product sales:

	Net Product Sales						Accounts Receivable
	Three Months Ended June 30, 2019			Six Months Ended June 30, 2019			As of June 30, 2019
Customer A		41.3	%		41.0	%		42.0	%
Customer B		40.4	%		38.7	%		48.0	%
Customer C		15.8	%		17.9	%		8.9	%
Total		97.5	%		97.6	%		98.9	%

Accounts Receivable, Net

Accounts receivable are recorded at the invoice amount, net of an allowance for doubtful accounts. The allowance for doubtful accounts reflects accounts receivable balances that are believed to be uncollectible. In estimating the allowance for doubtful accounts, we consider: (1) our historical experience with collections and write-offs; (2) the credit quality of our Customers and any recent or anticipated changes thereto; and (3) the outstanding balances and past due amounts from our Customers.

We offered extended payment terms to our Customers in connection with our product launches of SUSTOL and CINVANTI in October 2016 and January 2018, respectively, in anticipation of the timing in reimbursement by government and commercial payers. Effective January 2018, we shortened payment terms to certain of our SUSTOL Customers. As of June 30, 2019, extended payment terms given to our Customers were evaluated in accordance with GAAP and did not impact the collectability of accounts receivables.

As of June 30, 2019, we determined that an allowance for doubtful accounts was not required. For the three months ended June 30, 2019, we did not write off any accounts receivable balances.

Inventory

Inventory is stated at the lower of cost or estimated net realizable value on a first-in, first-out, or FIFO, basis. We periodically analyze our inventory levels and write down inventory that has become obsolete, inventory that has a cost basis in excess of its estimated realizable value and inventory quantities that are in excess of expected sales requirements as cost of product sales. The determination of whether inventory costs will be realizable requires estimates by management. If actual market conditions are less favorable than projected by management, additional write-downs of inventory may be required, which would be recorded as a cost of product sales.

Leases

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842): Targeted Improvements and ASU No. 2018-10, Codification Improvements to Topic 842, Leases. ASU 2016-02 and the subsequent modifications are identified as “ASC 842.” ASC 842 requires lessees to classify leases as either finance or operating based on whether or not the lease is effectively a financed purchase. Lease expense is recognized over the term of the lease using an effective interest method for finance leases and on a straight-line basis over the lease term for operating leases. A lessee is also required to record a right-of-use (“ROU”) lease asset and a lease liability for all leases with a lease term greater than twelve months. Leases with a term of twelve months or less will be accounted for similar to existing guidance for operating leases. ASC 842 is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years.

We adopted ASC 842 on January 1, 2019 using the alternative transition method allowed under ASU No. 2018-11. We elected the package of practical expedients permitted under the transition guidance, which allowed us to carryforward our historical assessments of: (i) whether a contract is or contains a lease; (ii) lease classification; and (iii) initial direct costs. We elected a policy of not recording leases on the balance sheet when the lease term is 12 months or less. The adoption of ASC 842 had a substantial impact on the condensed consolidated balance sheet with the recognition of lease liabilities and corresponding ROU lease assets. There was no material impact on our results of operations or liquidity (see Note 7).

We determine if an agreement is a lease or contains lease components at inception. Operating leases are recorded as lease liabilities with corresponding ROU lease assets on the condensed consolidated balance sheets. ROU lease assets represent our right to use the underlying assets over the lease term, and lease liabilities represent the present value of our obligation to make lease payments arising from the lease. Lease liabilities are recognized at the lease commencement based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. We use the implicit rate when readily determinable. The ROU lease assets equal the lease liabilities, less unamortized lease incentives, unamortized initial direct costs and the cumulative difference between rent expense and amounts paid under the lease. The lease term includes any option to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense is recognized on a straight-line basis over the lease term. We have lease agreements with both lease and non-lease components, which are generally accounted for separately.

Revenue Recognition

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“Topic 606”). Topic 606 is based on the principle that revenue should be recognized to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In the first quarter of 2018, we adopted Topic 606 using the modified retrospective approach. Under this approach, incremental disclosures are provided to present each financial statement line item for 2018 under the prior standard. As a result of the adoption of Topic 606, we recorded a cumulative adjustment to retained earnings of $1.6 million on January 1, 2018. This adjustment reflects the acceleration of $2.9 million in gross product sales less $1.1 million in product sales allowances and $0.2 million in cost of product sales.

Product Sales

SUSTOL is distributed in the U.S. through a limited number of Customers that resell SUSTOL to healthcare providers, the end users of SUSTOL. CINVANTI is distributed in the U.S. through a limited number of Customers that resell CINVANTI to healthcare providers and hospitals, the end users of CINVANTI.

Revenue is recognized in an amount that reflects the consideration we expect to receive in exchange for our products. To determine revenue recognition for contracts with customers within the scope of Topic 606, we performed the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations of the contract(s); (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract(s); and (v) recognize revenue when (or as) we satisfy the performance obligations.

Product Sales Allowances

We recognize product sales allowances as a reduction of product sales in the same period the related revenue is recognized. Product sales allowances are based on amounts owed or to be claimed on the related sales. These estimates take into consideration the terms of our agreements with Customers, historical product returns, rebates or discounts taken, the shelf life of the product and specific known market events, such as competitive pricing and new product introductions. If actual future results vary from our estimates, we may need to adjust these estimates, which could have an effect on product sales and earnings in the period of adjustment. Our product sales allowances include:

•

Product Returns — We allow our Customers to return product for credit 12 months after its product expiration date. As such, there may be a significant period of time between the time the product is shipped and the time the credit is issued on returned product.

•

Distributor Fees — We offer contractually determined discounts to our Customers. These discounts are paid no later than two months after the quarter in which product was shipped.

•

Group Purchasing Organization (“GPO”) Discounts and Rebates — We offer cash discounts to GPO members. These discounts are taken when the GPO members purchase SUSTOL or CINVANTI from our Customers, who then charge back to us the discount amount. Additionally, we offer volume and contract-tier rebates to GPO members. Rebates are based on actual purchase levels during the quarterly rebate purchase period.

•

GPO Administrative Fees — We pay administrative fees to GPOs for services and access to data. These fees are based on contracted terms and are paid after the quarter in which the product was purchased by the GPOs’ members.

•

Medicaid Rebates — We participate in Medicaid rebate programs, which provide assistance to certain low-income patients based on each individual state’s guidelines regarding eligibility and services. Under the Medicaid rebate programs, we pay a rebate to each participating state, generally within three months after the quarter in which SUSTOL or CINVANTI was sold.

We believe our estimated allowance for product returns requires a high degree of judgment and is subject to change based on our experience and certain quantitative and qualitative factors. We believe our estimated allowances for distributor fees, GPO discounts, rebates and administrative fees and Medicaid rebates do not require a high degree of judgment because the amounts are settled within a relatively short period of time.

Our product sales allowances and related accruals are evaluated each reporting period and adjusted when trends or significant events indicate that a change in estimate is appropriate. Changes in sales allowance estimates could materially affect our results of operations and financial position.

The following table provides a summary of activity with respect to our product returns, distributor fees and discounts, rebates and administrative fees, which are included in other accrued liabilities on the condensed consolidated balance sheets (in thousands):

	Product Returns			Distributor Fees			Discounts, Rebates and Administrative Fees			Total
Balance at December 31, 2018	$	947		$	2,813		$	21,743		$	25,503
Provision		707			8,434			66,334			75,475
Payments/credits		(41	)		(7,225	)		(54,087	)		(61,353	)
Balance at June 30, 2019	$	1,613		$	4,022		$	33,990		$	39,625

Comprehensive Loss

Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources. Net changes in unrealized gains and losses on available-for-sale securities are included in other comprehensive loss and represent the difference between our net loss and comprehensive loss.

Net Loss per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration of common stock equivalents. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, stock options, warrants and shares of common stock underlying Convertible Notes are considered to be common stock equivalents and are included in the calculation of diluted net loss per share only when their effect is dilutive.

Because we have incurred a net loss for each of the periods presented in the unaudited condensed consolidated statements of operations and comprehensive loss, the following common stock equivalents were not included in the computation of net loss per share because their effect would be anti-dilutive (in thousands):

	June 30,
	2019		2018
Stock options outstanding		13,545		12,514
Warrants outstanding		640		640
Shares of common stock underlying Convertible Notes outstanding		8,729		8,224

Recent Accounting Pronouncements

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820) - Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”), which is designed to improve the effectiveness of disclosures by removing, modifying and adding disclosures related to fair value measurements. ASU 2018-13 is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted. We plan to adopt the provisions of ASU 2018-13 in the first quarter of 2020, and we are currently evaluating the impact on our consolidated financial statements.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”), which amends the impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables and available-for-sale debt securities. In May 2019, the FASB issued ASU No. 2019-05, Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief (“ASU 2019-05”), which amends ASU 2016-13 by providing entities with an option to irrevocably elect the fair value option to be applied on an instrument-by-instrument basis for eligible financial instruments that are within the scope of Topic 326. The fair value option election does not apply to held-to-maturity debt securities. ASU 2016-13, as amended, is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. Early adoption is permitted. We plan to adopt the provisions of ASU 2016-13, as amended, in the first quarter of 2020, and we are currently evaluating the impact on our results of operations, financial condition and internal controls.

Fair Value Measurements

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The FASB Accounting Standards Codification (“ASC”) Topic 820, Fair Value Measurements and Disclosures, establishes a fair value hierarchy which prioritizes the inputs used in measuring fair value as follows:

•

Level 1 — Observable inputs such as quoted prices in active markets for identical assets or liabilities.

•

Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

•

Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

We measure cash, cash equivalents and short-term investments at fair value on a recurring basis. The fair values of such assets were as follows (in thousands):

			Fair Value Measurements at Reporting Date Using
	Balance at June 30, 2019		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash and money market funds	$	33,070	$	33,070	$	—	$	—
U.S. treasury bills and government agency obligations		99,615		99,615		—		—
U.S. corporate debt securities		33,037		—		33,037		—
Foreign corporate debt securities		17,011		—		17,011		—
U.S. commercial paper		61,954		—		61,954		—
Foreign commercial paper		31,318		—		31,318		—
Total	$	276,005	$	132,685	$	143,320	$	—

			Fair Value Measurements at Reporting Date Using
	Balance at December 31, 2018		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash and money market funds	$	22,751	$	22,751	$	—	$	—
U.S. treasury bills and government agency obligations		59,741		59,741		—		—
U.S. corporate debt securities		59,087		—		59,087		—
Foreign corporate debt securities		5,046		—		5,046		—
U.S. commercial paper		61,885		—		61,885		—
Foreign commercial paper		123,861		—		123,861		—
Total	$	332,371	$	82,492	$	249,879	$	—

We have not transferred any investment securities between the three levels of the fair value hierarchy.

As of June 30, 2019, cash equivalents included $20.0 million of available-for-sale securities with contractual maturities of three months or less, and short-term investments included $223.0 million of available-for-sale securities with contractual maturities of three months to one year. As of December 31, 2018, cash equivalents included $9.1 million of available-for-sale securities with contractual maturities of three months or less, and short-term investments included $300.5 million of available-for-sale securities with contractual maturities of three months to one year. The money market funds as of June 30, 2019 and December 31, 2018 are included in cash and cash equivalents on the unaudited condensed consolidated balance sheets.

A company may elect to use fair value to measure accounts and loans receivable, available-for-sale and held-to-maturity securities, equity method investments, accounts payable, guarantees and issued debt. Other eligible items include firm commitments for financial instruments that otherwise would not be recognized at inception and non-cash warranty obligations where a warrantor is permitted to pay a third party to provide the warranty goods or services. If the use of fair value is elected, any upfront costs and fees related to the item such as debt issuance costs must be recognized in earnings and cannot be deferred. The fair value election is irrevocable and generally made on an instrument-by-instrument basis, even if a company has similar instruments that it elects not to measure based on fair value. Unrealized gains and losses on existing items for which fair value has been elected are reported as a cumulative adjustment to beginning retained earnings and any changes in fair value are recognized in earnings. We have elected to not apply the fair value option to our financial assets and liabilities.

Financial instruments, including cash, cash equivalents, receivables, inventory, prepaid expenses, other current assets, accounts payable and accrued expenses are carried at cost, which is considered to be representative of their respective fair values because of the short-term maturity of these instruments. Short-term available-for-sale investments are carried at fair value. Our Convertible Notes outstanding at June 30, 2019 do not have a readily available ascertainable market value, however, the carrying value is considered to approximate its fair value.

- Definition

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

+ References + Details

Short-Term Investments

6 Months Ended

Jun. 30, 2019

Short Term Investments [Abstract]

Short-Term Investments

5. Short-Term Investments

The following is a summary of our short-term investments (in thousands):

	June 30, 2019
			Gross		Gross
	Amortized		Unrealized		Unrealized		Estimated
	Cost		Gains		Losses		Fair Value
U.S. treasury bills and government agency obligations	$	99,524	$	91	$	—	$	99,615
U.S. corporate debt securities		33,007		30		—		33,037
Foreign corporate debt securities		10,002		16		—		10,018
U.S. commercial paper		48,969		10		—		48,979
Foreign commercial paper		31,318		—		—		31,318
Total	$	222,820	$	147	$	—	$	222,967

	December 31, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		Losses			Fair Value
U.S. treasury bills and government agency obligations	$	59,747	$	—	$	(6	)	$	59,741
U.S. corporate debt securities		59,164		—		(77	)		59,087
Foreign corporate debt securities		5,041		5		—			5,046
U.S. commercial paper		52,800		—		—			52,800
Foreign commercial paper		123,870		—		(9	)		123,861
Total	$	300,622	$	5	$	(92	)	$	300,535

The amortized cost of debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. We regularly monitor and evaluate the realizable value of our marketable securities. We did not recognize any impairment losses during the three and six months ended June 30, 2019 and 2018.

Realized gains and losses associated with our investments, if any, are reported in the statements of operations and comprehensive loss. We did not recognize any realized gains or losses during the three months ended June 30, 2019 and 2018. We recognized $8,000 in realized gains during the six months ended June 30, 2019. We did not recognize any realized gains or losses during the six months ended June 30, 2018.

Inventory

6 Months Ended

Jun. 30, 2019

Inventory Disclosure [Abstract]

Inventory

6. Inventory

Inventory consists of the following (in thousands):

	June 30, 2019		December 31, 2018
Raw materials	$	9,349	$	10,112
Work in process		13,026		20,604
Finished goods		6,895		8,316
Total inventory	$	29,270	$	39,032

As of June 30, 2019, total inventory included $4.0 million related to SUSTOL and $25.3 million related to CINVANTI. As of December 31, 2018, total inventory included $6.7 million related to SUSTOL and $32.3 million related to CINVANTI.

Leases

6 Months Ended

Jun. 30, 2019

Leases [Abstract]

Leases

7. Leases

As of June 30, 2019, we had operating leases for laboratory and office space in San Diego, California, as well as office space in Jersey City, New Jersey, with remaining lease terms of 78 months and six months, respectively.

On January 1, 2019, on the adoption of ASC 842, we recognized initial ROU lease assets of $13.7 million and initial lease liabilities of $14.5 million. Our weighted-average remaining lease term for our operating leases was 78 months. The option to extend our lease in San Diego was not recognized as part of our lease liability and ROU lease assets. During the three and six months ended June 30, 2019, we recognized $0.8 million and $1.7 million of operating lease expense, respectively. During the three and six months ended June 30, 2019, we paid $1.1 million and $2.1 million, respectively, for our operating leases.

Future minimum lease payments under our operating leases are as follows (in thousands):

Year Ending June 30,
2020	$	2,599
2021		2,761
2022		2,842
2023		2,925
2024		2,660
Thereafter		2,104
Total future minimum lease payments	$	15,891
Less: discount		(2,918	)
Total lease liabilities	$	12,973

Secured Notes to Related Party

6 Months Ended

Jun. 30, 2019

Debt Disclosure [Abstract]

Secured Notes to Related Party

8. Secured Notes to Related Party

Convertible Notes

In April 2011, we entered into a securities purchase agreement for a private placement of up to $4.5 million in Convertible Notes with certain investors, including Tang Capital Partners, LP (“TCP”). TCP is controlled by Tang Capital Management, LLC (“TCM”). The manager of TCM is Kevin C. Tang, who served as a director at the time and currently serves as the Chairman of our Board of Directors. At the time of issuance, the terms of the Convertible Notes were determined by our independent directors to be no less favorable than terms that would be obtained in an arm’s length financing transaction. We received a total of $4.3 million, net of issuance costs, from the issuance of these Convertible Notes.

The Convertible Notes are secured by substantially all of our assets, including placing our bank and investment accounts under a control agreement. The Convertible Notes bear interest at 6% per annum, payable quarterly in cash or in additional principal amount of Convertible Notes, at the election of the purchasers. The Convertible Notes mature on May 2, 2021; however, the holders of the Convertible Notes may require prepayment of the Convertible Notes at any time, at each holder’s option.

The Convertible Notes are convertible into shares of our common stock at a rate of 1,250 shares for every $1,000 of outstanding principal due under the Convertible Notes. There is no right to convert the Convertible Notes to the extent that, after giving effect to such conversion, the holder would beneficially own in excess of 9.99% of our outstanding common stock. Each holder of the Convertible Notes can increase or decrease this beneficial ownership conversion limit by written notice to us, which will not be effective until 61 days after delivery of the notice.

As of June 30, 2019, we were in compliance with all covenants under the Convertible Notes. On the occurrence of an event of default under the Convertible Notes, the holders of the Convertible Notes have the right to require us to redeem all or a portion of their Convertible Notes.

In 2011, we filed a registration statement with the SEC to register for resale 3.5 million shares underlying the Convertible Notes. The registration statement was declared effective on July 29, 2011. The Convertible Note holders have agreed to waive their right to require us to maintain the effectiveness of the registration statement and to register the additional shares underlying the Convertible Notes until they provide notice otherwise.

The Convertible Notes contain an embedded conversion feature that was in-the-money on the issuance dates. Based on an effective fixed conversion rate of 1,250 shares for every $1,000 of principal and accrued interest due under the Convertible Notes, the total conversion benefit at issuance exceeded the loan proceeds. Therefore, a debt discount was recorded in an amount equal to the face value of the Convertible Notes on the issuance dates, and we began amortizing the resultant debt discount over the respective 10-year term of the Convertible Notes. During the six months ended June 30, 2019, accrued interest of $0.2 million was paid-in-kind and rolled into the Convertible Note principal balance, which resulted in an additional debt discount of $0.2 million. For each of the three months ended June 30, 2019 and 2018, interest expense relating to the stated rate was $0.1 million. For the three months ended June 30, 2019 and 2018, interest expense relating to the amortization of the debt discount was $0.3 million and $0.2 million, respectively. For each of the six months ended June 30, 2019 and 2018, interest expense relating to the stated rate was $0.2 million. For the six months ended June 30, 2019 and 2018, interest expense relating to the amortization of the debt discount was $0.5 million and $0.4 million, respectively.

As of June 30, 2019, the carrying value of the Convertible Notes was $5.1 million, which is comprised of the $7.0 million principal amount of the Convertible Notes outstanding, less debt discount of $1.9 million. As of June 30, 2019, the Convertible Notes were convertible into 8.7 million shares of our common stock.

Promissory Note

In August 2016, we entered into the Subordinated Secured Promissory Note (“Promissory Note”) with TCP whereby TCP agreed to lend us up to $100.0 million. The Promissory Note had a two-year term and bore interest at a rate of 8% per annum. The first close of $50.0 million occurred on August 5, 2016. The second close of an additional $50.0 million was not drawn and expired prior to the draw down. There were no fees, no warrants and no equity conversion features associated with this transaction. The Promissory Note was secured by a second-priority lien on substantially all of our assets. TCP is controlled by TCM. The manager of TCM is Kevin C. Tang, who serves as the Chairman of our Board of Directors. The terms of the Promissory Note were determined by our independent directors to be no less favorable than terms that would be obtained in an arm’s length financing transaction.

For the three and six months ended June 30, 2018, interest expense was $0.5 million and $1.0 million, respectively. In August 2018, we paid the remaining obligation under the Promissory Note, which included $25.0 million of outstanding principal and $0.2 million of accrued interest. As of June 30, 2019, there were no remaining obligations under the Promissory Note.

Stockholders' Equity

6 Months Ended

Jun. 30, 2019

Equity [Abstract]

Stockholders’ Equity

9. Stockholders’ Equity

Common Stock Offerings

In April 2018, we sold 6.9 million shares of our common stock at a public offering price of $26.00 per share. We received total net cash proceeds of $168.7 million (net of $10.7 million in issuance costs) from the sale of the common stock.

In June 2018, we sold 5.1 million shares of our common stock at a public offering price of $39.50 per share. We received total net cash proceeds of $194.4 million (net of $5.6 million in issuance costs) from the sale of the common stock.

Stock Option Activity

The following table summarizes the stock option activity for the three months ended June 30, 2019:

	Shares (in thousands)			Weighted- average Exercise Price		Weighted- average Remaining Contractual Term (Years)
Balance at December 31, 2018		15,265		$	18.33		6.87
Granted		455		$	24.47
Exercised		(1,542	)	$	10.52
Expired and forfeited		(633	)	$	20.83
Balance at June 30, 2019		13,545		$	19.31		6.99

For the six months ended June 30, 2019, 1,542,000 shares of common stock were issued pursuant to the exercise of stock options, resulting in net proceeds of $16.2 million.

Stock-based Compensation

The following table summarizes stock-based compensation expense related to stock-based payment awards granted pursuant to all of our equity compensation arrangements (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Research and development	$	4,434	$	3,115	$	9,758	$	6,151
General and administrative		3,714		2,308		7,394		4,584
Sales and marketing		4,558		2,398		13,456		4,787
Total stock-based compensation expense	$	12,706	$	7,821	$	30,608	$	15,522

As of June 30, 2019, there was $84.5 million of total unrecognized compensation cost related to non-vested, stock-based payment awards granted under all of our equity compensation plans and all non-plan option grants. Total unrecognized compensation cost will be adjusted for future changes in estimated forfeitures. We expect to recognize this compensation cost over a weighted-average period of 2.5 years.

We estimated the fair value of each option grant on the grant date using the Black-Scholes option pricing model with the following weighted-average assumptions:

	June 30,
	2019			2018
Risk-free interest rate		2.4	%		2.7	%
Dividend yield		0.0	%		0.0	%
Volatility		68.0	%		71.1	%
Expected life (years)		6			6

We estimated the fair value of each purchase right granted under our 1997 Employee Stock Purchase Plan at the beginning of each new offering period using the Black-Scholes option pricing model with the following weighted-average assumptions:

	June 30,
	2019			2018
Risk-free interest rate		2.4	%		2.1	%
Dividend yield		0.0	%		0.0	%
Volatility		58.4	%		59.8	%
Expected life (months)		6			6

Income Taxes

6 Months Ended

Jun. 30, 2019

Income Tax Disclosure [Abstract]

Income Taxes

10. Income Taxes

Deferred income tax assets and liabilities are recognized for temporary differences between financial statements and income tax carrying values using tax rates in effect for the years such differences are expected to reverse. Due to uncertainties surrounding our ability to generate future taxable income and consequently realize such deferred income tax assets, a full valuation allowance has been established. We continue to maintain a full valuation allowance against our deferred tax assets as of June 30, 2019.

The impact of an uncertain income tax position on the income tax return must be recognized at the largest amount that is more likely than not to be sustained upon audit by the relevant tax authority. An uncertain income tax position will be recognized when it is more likely than not of being sustained. The disclosures included in our Annual Report on Form 10-K for the year ended December 31, 2018, which was filed with the SEC on February 22, 2019, continue to be accurate for the three and six months ended June 30, 2019.

Legal Proceedings

6 Months Ended

Jun. 30, 2019

Commitments And Contingencies Disclosure [Abstract]

Legal Proceedings

11. Legal Proceedings

On June 3, 2019, a purported federal securities class action complaint was filed against the Company, its Chief Executive Officer and Chief Financial Officer by Jimmy Wong, individually and on behalf of all others similarly situated (the “Plaintiff”), in the United States District Court for the Southern District of California (the “Complaint”). In the Complaint, the Plaintiff alleges certain violations of federal securities laws in connection with the decline in market value of the Company’s securities following the Company’s announcement of its receipt of a CRL from the FDA regarding the NDA for HTX-011. The Plaintiff seeks class action certification, damages in an unspecified amount, prejudgment and post-judgment interest, fees and costs and such other relief as the United States District Court for the Southern District of California may deem just and proper. The Company intends to defend itself vigorously in the case. Due to the early stage of this proceeding, we are not able to predict or reasonably estimate the outcome or possible losses relating to this matter.

Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Basis of Presentation

Principles of Consolidation

Use of Estimates

Cash, Cash Equivalents and Short-term Investments

Cash and cash equivalents consist of cash and highly liquid investments with contractual maturities of three months or less from the original purchase date.

Our bank and investment accounts have been placed under a control agreement in accordance with our Senior Secured Convertible Notes (“Convertible Notes”) (see Note 8).

Concentration of Credit Risk

The following table includes the percentage of net product sales and accounts receivable balances for our three major Customers, each of which comprised 10% or more of our net product sales:

	Net Product Sales						Accounts Receivable
	Three Months Ended June 30, 2019			Six Months Ended June 30, 2019			As of June 30, 2019
Customer A		41.3	%		41.0	%		42.0	%
Customer B		40.4	%		38.7	%		48.0	%
Customer C		15.8	%		17.9	%		8.9	%
Total		97.5	%		97.6	%		98.9	%

Accounts Receivable, Net

As of June 30, 2019, we determined that an allowance for doubtful accounts was not required. For the three months ended June 30, 2019, we did not write off any accounts receivable balances.

Inventory

Leases

Revenue Recognition

Product Sales

Product Sales Allowances

•

Distributor Fees — We offer contractually determined discounts to our Customers. These discounts are paid no later than two months after the quarter in which product was shipped.

•

	Product Returns			Distributor Fees			Discounts, Rebates and Administrative Fees			Total
Balance at December 31, 2018	$	947		$	2,813		$	21,743		$	25,503
Provision		707			8,434			66,334			75,475
Payments/credits		(41	)		(7,225	)		(54,087	)		(61,353	)
Balance at June 30, 2019	$	1,613		$	4,022		$	33,990		$	39,625

Comprehensive Loss

Net Loss per Share

	June 30,
	2019		2018
Stock options outstanding		13,545		12,514
Warrants outstanding		640		640
Shares of common stock underlying Convertible Notes outstanding		8,729		8,224

Recent Accounting Pronouncements

Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2019

Accounting Policies [Abstract]

Percentage of Net Product Sales and Accounts Receivable Balance

The following table includes the percentage of net product sales and accounts receivable balances for our three major Customers, each of which comprised 10% or more of our net product sales:

	Net Product Sales						Accounts Receivable
	Three Months Ended June 30, 2019			Six Months Ended June 30, 2019			As of June 30, 2019
Customer A		41.3	%		41.0	%		42.0	%
Customer B		40.4	%		38.7	%		48.0	%
Customer C		15.8	%		17.9	%		8.9	%
Total		97.5	%		97.6	%		98.9	%

Summary of Activity to Product Returns, Distributor Fees and Discounts, Rebates and Administrative Fees

	Product Returns			Distributor Fees			Discounts, Rebates and Administrative Fees			Total
Balance at December 31, 2018	$	947		$	2,813		$	21,743		$	25,503
Provision		707			8,434			66,334			75,475
Payments/credits		(41	)		(7,225	)		(54,087	)		(61,353	)
Balance at June 30, 2019	$	1,613		$	4,022		$	33,990		$	39,625

Common Stock Equivalents Excluded From Computation of Net Loss Per Share

	June 30,
	2019		2018
Stock options outstanding		13,545		12,514
Warrants outstanding		640		640
Shares of common stock underlying Convertible Notes outstanding		8,729		8,224

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2019

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

We measure cash, cash equivalents and short-term investments at fair value on a recurring basis. The fair values of such assets were as follows (in thousands):

			Fair Value Measurements at Reporting Date Using
	Balance at June 30, 2019		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash and money market funds	$	33,070	$	33,070	$	—	$	—
U.S. treasury bills and government agency obligations		99,615		99,615		—		—
U.S. corporate debt securities		33,037		—		33,037		—
Foreign corporate debt securities		17,011		—		17,011		—
U.S. commercial paper		61,954		—		61,954		—
Foreign commercial paper		31,318		—		31,318		—
Total	$	276,005	$	132,685	$	143,320	$	—

			Fair Value Measurements at Reporting Date Using
	Balance at December 31, 2018		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Cash and money market funds	$	22,751	$	22,751	$	—	$	—
U.S. treasury bills and government agency obligations		59,741		59,741		—		—
U.S. corporate debt securities		59,087		—		59,087		—
Foreign corporate debt securities		5,046		—		5,046		—
U.S. commercial paper		61,885		—		61,885		—
Foreign commercial paper		123,861		—		123,861		—
Total	$	332,371	$	82,492	$	249,879	$	—

Short-Term Investments (Tables)

6 Months Ended

Jun. 30, 2019

Short Term Investments [Abstract]

Summary of Short-Term Investments

The following is a summary of our short-term investments (in thousands):

	June 30, 2019
			Gross		Gross
	Amortized		Unrealized		Unrealized		Estimated
	Cost		Gains		Losses		Fair Value
U.S. treasury bills and government agency obligations	$	99,524	$	91	$	—	$	99,615
U.S. corporate debt securities		33,007		30		—		33,037
Foreign corporate debt securities		10,002		16		—		10,018
U.S. commercial paper		48,969		10		—		48,979
Foreign commercial paper		31,318		—		—		31,318
Total	$	222,820	$	147	$	—	$	222,967

	December 31, 2018
			Gross		Gross
	Amortized		Unrealized		Unrealized			Estimated
	Cost		Gains		Losses			Fair Value
U.S. treasury bills and government agency obligations	$	59,747	$	—	$	(6	)	$	59,741
U.S. corporate debt securities		59,164		—		(77	)		59,087
Foreign corporate debt securities		5,041		5		—			5,046
U.S. commercial paper		52,800		—		—			52,800
Foreign commercial paper		123,870		—		(9	)		123,861
Total	$	300,622	$	5	$	(92	)	$	300,535

Inventory (Tables)

6 Months Ended

Jun. 30, 2019

Inventory Disclosure [Abstract]

Schedule of Inventory

Inventory consists of the following (in thousands):

	June 30, 2019		December 31, 2018
Raw materials	$	9,349	$	10,112
Work in process		13,026		20,604
Finished goods		6,895		8,316
Total inventory	$	29,270	$	39,032

Leases (Tables)

6 Months Ended

Jun. 30, 2019

Leases [Abstract]

Summary of Future Minimum Lease Payments

Future minimum lease payments under our operating leases are as follows (in thousands):

Year Ending June 30,
2020	$	2,599
2021		2,761
2022		2,842
2023		2,925
2024		2,660
Thereafter		2,104
Total future minimum lease payments	$	15,891
Less: discount		(2,918	)
Total lease liabilities	$	12,973

Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2019

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Summary of Stock Option Activity

The following table summarizes the stock option activity for the three months ended June 30, 2019:

	Shares (in thousands)			Weighted- average Exercise Price		Weighted- average Remaining Contractual Term (Years)
Balance at December 31, 2018		15,265		$	18.33		6.87
Granted		455		$	24.47
Exercised		(1,542	)	$	10.52
Expired and forfeited		(633	)	$	20.83
Balance at June 30, 2019		13,545		$	19.31		6.99

Summary of Stock-Based Compensation Expense related to Stock-Based Payment Awards Granted

The following table summarizes stock-based compensation expense related to stock-based payment awards granted pursuant to all of our equity compensation arrangements (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Research and development	$	4,434	$	3,115	$	9,758	$	6,151
General and administrative		3,714		2,308		7,394		4,584
Sales and marketing		4,558		2,398		13,456		4,787
Total stock-based compensation expense	$	12,706	$	7,821	$	30,608	$	15,522

Summary of Fair Value of Option Grant on Grant Date Using Black-Scholes Option Pricing Model

We estimated the fair value of each option grant on the grant date using the Black-Scholes option pricing model with the following weighted-average assumptions:

	June 30,
	2019			2018
Risk-free interest rate		2.4	%		2.7	%
Dividend yield		0.0	%		0.0	%
Volatility		68.0	%		71.1	%
Expected life (years)		6			6

1997 Employee Stock Purchase Plan

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Summary of Fair Value of Option Grant on Grant Date Using Black-Scholes Option Pricing Model

	June 30,
	2019			2018
Risk-free interest rate		2.4	%		2.1	%
Dividend yield		0.0	%		0.0	%
Volatility		58.4	%		59.8	%
Expected life (months)		6			6

Business - Additional Information (Details) $ in Millions	Jun. 30, 2019 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash, cash equivalents and short-term investments	$ 276.0

Accounting Policies - Percentage of Net Product Sales and Accounts Receivable Balance (Details) - Customer Concentration Risk	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Revenue Benchmark
Product Information [Line Items]
Concentration risk percentage	97.50%	97.60%
Revenue Benchmark \| Largest Customer
Product Information [Line Items]
Concentration risk percentage	41.30%	41.00%
Revenue Benchmark \| Second Largest Customer
Product Information [Line Items]
Concentration risk percentage	40.40%	38.70%
Revenue Benchmark \| Third Largest Customer
Product Information [Line Items]
Concentration risk percentage	15.80%	17.90%
Accounts Receivable
Product Information [Line Items]
Concentration risk percentage		98.90%
Accounts Receivable \| Largest Customer
Product Information [Line Items]
Concentration risk percentage		42.00%
Accounts Receivable \| Second Largest Customer
Product Information [Line Items]
Concentration risk percentage		48.00%
Accounts Receivable \| Third Largest Customer
Product Information [Line Items]
Concentration risk percentage		8.90%

Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Product Information [Line Items]
Cumulative adjustment to retained earnings							$ 1	$ 1,573
Gross product sales		$ 36,659	$ 17,277	$ 68,261	$ 28,844
Product sales allowances		39,625		39,625		$ 25,503
Cost of product sales		$ 13,588	$ 5,231	$ 28,550	$ 8,364
Accounting Standards Update 2014-09
Product Information [Line Items]
Gross product sales	$ 2,900
Cost of product sales	200
Accounting Standards Update 2014-09 \| Product Sales Allowance
Product Information [Line Items]
Product sales allowances	1,100
Retained Earnings
Product Information [Line Items]
Cumulative adjustment to retained earnings							$ 1	$ 1,573
Retained Earnings \| Accounting Standards Update 2014-09
Product Information [Line Items]
Cumulative adjustment to retained earnings	$ 1,600

Accounting Policies - Summary of Activity to Product Returns, Distributor Fees and Discounts, Rebates and Administrative Fees (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Product Information [Line Items]
Balance	$ 25,503
Provision	75,475
Payments/credits	(61,353)
Balance	39,625
Allowance for Sales Returns
Product Information [Line Items]
Balance	947
Provision	707
Payments/credits	(41)
Balance	1,613
Allowance for Distributor Fees
Product Information [Line Items]
Balance	2,813
Provision	8,434
Payments/credits	(7,225)
Balance	4,022
Allowance for Rebates and Chargebacks
Product Information [Line Items]
Balance	21,743
Provision	66,334
Payments/credits	(54,087)
Balance	$ 33,990

Accounting Policies - Common Stock Equivalents Excluded From Computation of Net Loss Per Share (Details) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Share-based Payment Arrangement, Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded (in shares)	13,545	12,514
Warrant
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded (in shares)	640	640
Convertible Debt Securities
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares excluded (in shares)	8,729	8,224

Fair Value Measurements - Schedule of Financial Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 222,967	$ 300,535
U.S. Treasury Bills and Government Agency Obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	99,615	59,741
U.S. Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	33,037	59,087
Foreign Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	10,018	5,046
U.S. Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	48,979	52,800
Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	276,005	332,371
Fair Value, Recurring \| Foreign Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	31,318	123,861
Fair Value, Recurring \| U.S. Treasury Bills and Government Agency Obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	99,615	59,741
Fair Value, Recurring \| U.S. Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	33,037	59,087
Fair Value, Recurring \| Foreign Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	17,011	5,046
Fair Value, Recurring \| U.S. Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	61,954	61,885
Fair Value, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	132,685	82,492
Fair Value, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1) \| U.S. Treasury Bills and Government Agency Obligations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	99,615	59,741
Fair Value, Recurring \| Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	143,320	249,879
Fair Value, Recurring \| Significant Other Observable Inputs (Level 2) \| Foreign Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	31,318	123,861
Fair Value, Recurring \| Significant Other Observable Inputs (Level 2) \| U.S. Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	33,037	59,087
Fair Value, Recurring \| Significant Other Observable Inputs (Level 2) \| Foreign Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	17,011	5,046
Fair Value, Recurring \| Significant Other Observable Inputs (Level 2) \| U.S. Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Available-for-sale securities	61,954	61,885
Fair Value, Recurring \| Cash and Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and money market funds	33,070	22,751
Fair Value, Recurring \| Cash and Money Market Funds \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and money market funds	$ 33,070	$ 22,751

Fair Value Measurements - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Financial instruments transferred among fair value hierarchy levels	$ 0
Cash equivalents included of available-for-sale securities	20,000,000.0	$ 9,100,000
Short-term investments included of available-for-sale securities	$ 222,967,000	$ 300,535,000

Short-Term Investments - Summary of Short-Term Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	$ 222,820	$ 300,622
Available-for-sale securities, gross unrealized gains	147	5
Available-for-sale securities, gross unrealized losses		(92)
Available-for-sale securities	222,967	300,535
U.S. Treasury Bills and Government Agency Obligations
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	99,524	59,747
Available-for-sale securities, gross unrealized gains	91
Available-for-sale securities, gross unrealized losses		(6)
Available-for-sale securities	99,615	59,741
U.S. Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	33,007	59,164
Available-for-sale securities, gross unrealized gains	30
Available-for-sale securities, gross unrealized losses		(77)
Available-for-sale securities	33,037	59,087
Foreign Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	10,002	5,041
Available-for-sale securities, gross unrealized gains	16	5
Available-for-sale securities	10,018	5,046
U.S. Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	48,969	52,800
Available-for-sale securities, gross unrealized gains	10
Available-for-sale securities	48,979	52,800
Foreign Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, amortized cost	31,318	123,870
Available-for-sale securities, gross unrealized losses		(9)
Available-for-sale securities	$ 31,318	$ 123,861

Short-Term Investments - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Short Term Investments [Abstract]
Debt securities, impairment losses	$ 0	$ 0	$ 0	$ 0
Debt securities, realized gain and (losses)	$ 0	$ 0	$ 8,000	$ 0

Inventory - Schedule of Inventory (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 9,349	$ 10,112
Work in process	13,026	20,604
Finished goods	6,895	8,316
Total inventory	$ 29,270	$ 39,032

Inventory - Additional Information (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Inventory [Line Items]
Total inventory	$ 29,270	$ 39,032
SUSTOL
Inventory [Line Items]
Total inventory	4,000	6,700
CINVANTI
Inventory [Line Items]
Total inventory	$ 25,300	$ 32,300

Leases - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jan. 01, 2019
Lessee Lease Description [Line Items]
Right-of-use lease assets	$ 12,667	$ 12,667
Operating lease, initial lease liabilities	$ 12,973	$ 12,973
Operating lease, weighted-average remaining lease term	78 months	78 months
Operating lease, expense	$ 800	$ 1,700
Operating lease, payments	$ 1,100	$ 2,100
Accounting Standards Update 2016-02
Lessee Lease Description [Line Items]
Right-of-use lease assets			$ 13,700
Operating lease, initial lease liabilities			$ 14,500
San Diego, California
Lessee Lease Description [Line Items]
Operating leases, remaining lease term		78 months
Jersey City, New Jersey
Lessee Lease Description [Line Items]
Operating leases, remaining lease term		6 months

Leases - Summary of Future Minimum Lease Payments (Details) $ in Thousands	Jun. 30, 2019 USD ($)
Leases [Abstract]
2020	$ 2,599
2021	2,761
2022	2,842
2023	2,925
2024	2,660
Thereafter	2,104
Total future minimum lease payments	15,891
Less: discount	(2,918)
Total lease liabilities	$ 12,973

Secured Notes to Related Party - Additional Information (Details)				1 Months Ended			3 Months Ended		6 Months Ended
	Aug. 05, 2016 USD ($)	Aug. 02, 2016 USD ($) shares	Jul. 29, 2011 shares	Aug. 31, 2018 USD ($)	Aug. 31, 2016 USD ($)	Apr. 30, 2011 USD ($) Day shares	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) shares	Jun. 30, 2018 USD ($)
Debt Instrument [Line Items]
Proceeds from convertible debt						$ 4,300,000
Amortization of debt discount									$ 507,000	$ 428,000
Debt instrument, convertible, number shares of equity instruments \| shares									8,700,000
Convertible Notes
Debt Instrument [Line Items]
Convertible debt issuable in connection with private placement						$ 4,500,000
Debt instrument, interest rate						6.00%
Debt instrument, maturity date						May 02, 2021
Debt instrument conversion ratio multiple of principal						$ 1,000
Beneficial ownership after conversion						9.99%
Notice period associated with beneficial ownership percentage limitation convertible notes \| Day						61
Common shares registered for resale in connection with convertible notes \| shares			3,500,000
Debt instrument, term						10 years
Paid-in-kind interest									$ 200,000
Debt instrument, additional debt discount									200,000
Interest expense, debt, excluding amortization							$ 100,000	$ 100,000	200,000	200,000
Amortization of debt discount							300,000	200,000	500,000	400,000
Carrying value of debt							5,100,000		5,100,000
Debt instrument, face amount							7,000,000.0		7,000,000.0
Debt instrument, unamortized discount, total							1,900,000		1,900,000
Convertible Notes \| Common Stock
Debt Instrument [Line Items]
Debt instrument, number of shares issued for convertible notes \| shares						1,250
Term Loan \| Tang Capital
Debt Instrument [Line Items]
Debt instrument, interest rate					8.00%
Debt instrument, term					2 years
Carrying value of debt							$ 0		$ 0
Debt agreement, maximum borrowing capacity					$ 100,000,000.0
Proceeds from issuance of long-term debt, total	$ 50,000,000.0
Proceeds from issuance of long-term debt, subject to achievement of corporate milestone		$ 50,000,000.0
Debt instrument, fee amount		$ 0
Debt instrument, number of warrants \| shares		0
Debt instrument, convertible, beneficial conversion feature		$ 0
Interest expense								$ 500,000		$ 1,000,000.0
Debt outstanding principal paid				$ 25,000,000.0
Debt accrued interest paid				$ 200,000

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended				6 Months Ended
	Jun. 30, 2018	Apr. 30, 2018	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Class Of Stock [Line Items]
Proceeds from issuance of common stock	$ 194,400	$ 168,700
Shares of common stock issued pursuant to exercise of stock options							1,542,000
Proceeds from stock option exercises							$ 16,215	$ 10,641
Total unrecognized compensation cost related to non-vested, stock-based payment awards			$ 84,500				$ 84,500
Total unrecognized compensation cost, expect to recognize over weighted average period							2 years 6 months
Common Stock
Class Of Stock [Line Items]
Number of shares issued	5,100,000	6,900,000			11,963,000
Share price	$ 39.50	$ 26.00			$ 39.50			$ 39.50
Payments of stock issuance costs	$ 5,600	$ 10,700
Shares of common stock issued pursuant to exercise of stock options			810,000	732,000	504,000	435,000

Stockholders' Equity - Summary of Stock Option Activity (Details) - $ / shares	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Equity [Abstract]
Number of shares outstanding (in shares)	15,265,000
Number of shares granted (in shares)	455,000
Number of shares exercised (in shares)	(1,542,000)
Expired and forfeited (in shares)	(633,000)
Number of shares outstanding (in shares)	13,545,000	15,265,000
Number of shares outstanding, weighted average exercise price (in dollars per share)	$ 18.33
Number of shares granted, weighted average exercise price (in dollars per share)	24.47
Number of shares exercised, weighted average exercise price (in dollars per share)	10.52
Number of shares expired and forfeited, weighted average exercise price (in dollars per share)	20.83
Number of shares outstanding, weighted average exercise price (in dollars per share)	$ 19.31	$ 18.33
Number of shares outstanding, weighted average remaining contractual term (Year)	6 years 11 months 26 days	6 years 10 months 13 days

Stockholders' Equity - Summary of Stock-Based Compensation Expense related to Stock-Based Payment Awards Granted (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 12,706	$ 7,821	$ 30,608	$ 15,522
Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	4,434	3,115	9,758	6,151
General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	3,714	2,308	7,394	4,584
Selling and Marketing Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 4,558	$ 2,398	$ 13,456	$ 4,787

Stockholders' Equity - Summary of Fair Value of Option Grant on Grant Date Using Black-Scholes Option Pricing Model (Details)	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Share-based Payment Arrangement, Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	2.40%	2.70%
Dividend yield	0.00%	0.00%
Volatility	68.00%	71.10%
Expected life	6 years	6 years
1997 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	2.40%	2.10%
Dividend yield	0.00%	0.00%
Volatility	58.40%	59.80%
Expected life	6 months	6 months