Histogen (HSTO) 10-K 8 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Feb. 26, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	CNAT
Entity Registrant Name	Conatus Pharmaceuticals Inc.
Entity Central Index Key	1,383,701
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		33,165,122
Entity Public Float			$ 114.3

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 11,565	$ 16,079
Marketable securities	29,127	58,774
Collaboration receivables	3,677	3,367
Prepaid and other current assets	3,057	1,004
Total current assets	47,426	79,224
Property and equipment, net	154	179
Other assets	1,223	2,538
Total assets	48,803	81,941
Current liabilities:
Accounts payable and accrued expenses	6,216	11,962
Accrued compensation	2,230	2,008
Current portion of deferred revenue	10,075	14,172
Total current liabilities	18,521	28,142
Deferred revenue, less current portion	2,815	12,519
Convertible note payable	0	13,158
Deferred rent	68	126
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.0001 par value; 200,000 shares authorized; 33,165 shares issued and outstanding at December 31, 2018; 30,035 shares issued and outstanding at December 31, 2017	3	3
Additional paid-in capital	214,042	196,077
Accumulated other comprehensive loss	(17)	(77)
Accumulated deficit	(186,629)	(168,007)
Total stockholders’ equity	27,399	27,996
Total liabilities and stockholders’ equity	$ 48,803	$ 81,941

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
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	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	33,165,000	30,035,000
Common stock, shares outstanding	33,165,000	30,035,000

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Collaboration revenue	$ 33,586	$ 35,377	$ 799
Total revenues	33,586	35,377	799
Operating expenses:
Research and development	41,368	43,220	20,294
General and administrative	10,495	9,707	10,337
Total operating expenses	51,863	52,927	30,631
Loss from operations	(18,277)	(17,550)	(29,832)
Other income (expense):
Interest income	962	892	138
Interest expense	(696)	(662)	(70)
Other income (expense)	1	(76)	30
Total other income	267	154	98
Net loss	(18,010)	(17,396)	(29,734)
Other comprehensive income (loss):
Net unrealized gains (losses) on marketable securities	60	(71)	(2)
Comprehensive loss	$ (17,950)	$ (17,467)	$ (29,736)
Net loss per share, basic and diluted	$ (0.59)	$ (0.61)	$ (1.31)
Weighted average shares outstanding used in computing net loss per share, basic and diluted	30,370	28,587	22,650

Statements of Stockholders' Equ

Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2015	$ 34,540	$ 2	$ 155,441	$ (4)	$ (120,899)
Beginning balance, shares at Dec. 31, 2015		19,846
Vesting of early exercise of employee stock options	3	$ 0	3	0	0
Vesting of early exercise of employee stock options, shares		29
Issuance of common stock upon exercise of stock options	$ 56	$ 0	56	0	0
Issuance of common stock upon exercise of stock options, shares	61	61
Issuance of common stock for employee stock purchase plan	$ 50	$ 0	50	0	0
Issuance of common stock for employee stock purchase plan, shares		27
Share-based compensation	3,354	$ 0	3,354	0	0
Issuance of common stock, net of offering costs	13,522	$ 1	13,521	0	0
Issuance of common stock, net of offering costs, shares		6,156
Net loss	(29,734)	$ 0	0	0	(29,734)
Unrealized gain (loss) on marketable securities	(2)	0	0	(2)	0
Ending balance at Dec. 31, 2016	21,789	$ 3	172,425	(6)	(150,633)
Ending balance, shares at Dec. 31, 2016		26,119
Issuance of common stock upon exercise of stock options	$ 104	$ 0	104	0	0
Issuance of common stock upon exercise of stock options, shares	79	79
Issuance of common stock for employee stock purchase plan	$ 65	$ 0	65	0	0
Issuance of common stock for employee stock purchase plan, shares		24
Share-based compensation	4,098	$ 0	4,076	0	22
Issuance of common stock, net of offering costs	30,610	$ 0	30,610	0	0
Issuance of common stock, net of offering costs, shares		5,980
Repurchase of common stock	(11,203)	$ 0	(11,203)	0	0
Repurchase of common stock, shares		(2,167)
Net loss	(17,396)	$ 0	0	0	(17,396)
Unrealized gain (loss) on marketable securities	(71)	0	0	(71)	0
Ending balance at Dec. 31, 2017	27,996	$ 3	196,077	(77)	(168,007)
Ending balance, shares at Dec. 31, 2017		30,035
Issuance of common stock upon exercise of stock options	$ 362	$ 0	362	0	0
Issuance of common stock upon exercise of stock options, shares	211	211
Issuance of common stock for employee stock purchase plan	$ 117	$ 0	117	0	0
Issuance of common stock for employee stock purchase plan, shares		36
Share-based compensation	3,757	$ 0	3,757	0	0
Conversion of convertible note payable to common stock	13,729	$ 0	13,729	0	0
Conversion of convertible note payable to common stock, shares		2,883
Cumulative effect of adoption of accounting standard	(612)	$ 0	0	0	(612)
Net loss	(18,010)	0	0	0	(18,010)
Unrealized gain (loss) on marketable securities	60	0	0	60	0
Ending balance at Dec. 31, 2018	$ 27,399	$ 3	$ 214,042	$ (17)	$ (186,629)
Ending balance, shares at Dec. 31, 2018		33,165

Statements of Cash Flows

Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net loss	$ (18,010,000)	$ (17,396,000)	$ (29,734,000)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation	91,000	108,000	106,000
Stock-based compensation expense	3,757,000	4,098,000	3,354,000
Amortization of premiums and discounts on marketable securities, net	(341,000)	(68,000)	5,000
Accrued interest included in convertible note payable	696,000	658,000	0
Changes in operating assets and liabilities:
Collaboration receivables	(310,000)	(867,000)	(2,500,000)
Prepaid and other current assets	480,000	(123,000)	935,000
Other assets	(537,000)	(872,000)	(624,000)
Accounts payable and accrued expenses	(5,760,000)	6,638,000	2,856,000
Accrued compensation	222,000	(343,000)	918,000
Deferred revenue	(15,099,000)	(25,010,000)	51,701,000
Deferred rent	(46,000)	(32,000)	(20,000)
Net cash (used in) provided by operating activities	(34,857,000)	(33,209,000)	26,997,000
Investing activities
Maturities of marketable securities	69,685,000	81,877,000	44,597,000
Purchase of marketable securities	(39,637,000)	(121,723,000)	(40,905,000)
Capital expenditures	(66,000)	(25,000)	(110,000)
Net cash provided by (used in) investing activities	29,982,000	(39,871,000)	3,582,000
Financing activities
Proceeds from issuance of convertible note payable, net	0	12,500,000	0
Principal payment on promissory note	0	(1,000,000)	0
Proceeds from issuance of common stock, net	0	30,610,000	13,522,000
Repurchase of common stock	0	(11,203,000)	0
Deferred financing costs	(118,000)	0	0
Proceeds from stock issuances related to exercise of stock options and employee stock purchase plan	479,000	169,000	106,000
Net cash provided by financing activities	361,000	31,076,000	13,628,000
Net (decrease) increase in cash and cash equivalents	(4,514,000)	(42,004,000)	44,207,000
Cash and cash equivalents at beginning of period	16,079,000	58,083,000	13,876,000
Cash and cash equivalents at end of period	11,565,000	16,079,000	58,083,000
Supplemental disclosure of cash flow information:
Cash paid for interest	0	5,000	70,000
Supplemental schedule of noncash financing activities:
Conversion of convertible note payable to common stock	$ 13,729,000	$ 0	$ 0

Organization and Basis of Prese

Organization and Basis of Presentation	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Basis of Presentation	1. Organization and Basis of Presentation Conatus Pharmaceuticals Inc. (the Company) was incorporated in the state of Delaware on July 13, 2005. The Company is a biotechnology company focused on the development and commercialization of novel medicines to treat chronic diseases with significant unmet need. As of December 31, 2018, the Company has devoted substantially all of its efforts to product development and has not realized product sales revenues from its planned principal operations. The Company has a limited operating history, and the sales and income potential of the Company’s business and market are unproven. The Company has experienced net losses since its inception and, as of December 31, 2018, had an accumulated deficit of $186.6 million. The Company expects to continue to incur net losses for at least the next several years. Successful transition to attaining profitable operations is dependent upon achieving a level of revenues adequate to support the Company’s cost structure. If the Company is unable to generate revenues adequate to support its cost structure, the Company may need to raise additional equity or debt financing. As of December 31, 2018, the Company had cash, cash equivalents and marketable securities of $40.7 million and working capital of $28.9 million.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash. Additionally, the Company established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity. Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity from the date of purchase of three months or less to be cash equivalents. Cash and cash equivalents include cash in readily available checking and money market accounts. Marketable Securities The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the balance sheets, with unrealized gains and losses, if any, reported as a component of other comprehensive income (loss) within the statements of operations and comprehensive loss and as a separate component of stockholders’ equity. The Company classifies marketable securities with remaining maturities greater than one year as current assets because such marketable securities are available to fund the Company’s current operations. The Company invests its excess cash balances primarily in corporate debt securities and money market funds with strong credit ratings. Realized gains and losses are calculated on the specific identification method and recorded as interest income. There were no realized gains and losses for the years ended December 31, 2018, 2017 and 2016. At each balance sheet date, the Company assesses available-for-sale securities in an unrealized loss position to determine whether the unrealized loss is other-than-temporary. The Company considers factors including: the significance of the decline in value compared to the cost basis, underlying factors contributing to a decline in the prices of securities in a single asset class, the length of time the market value of the security has been less than its cost basis, the security’s relative performance versus its peers, sector or asset class, expected market volatility and the market and economy in general. When the Company determines that a decline in the fair value below its cost basis is other-than-temporary, the Company recognizes an impairment loss in the period in which the other-than-temporary decline occurred. There have been no other-than-temporary declines in the value of marketable securities for the years ended December 31, 2018, 2017 and 2016, as it is more likely than not the Company will hold the securities until maturity or a recovery of the cost basis. Fair Value of Financial Instruments The carrying amounts of collaboration receivables, prepaid and other current assets, and accounts payable and accrued expenses are reasonable estimates of their fair value because of the short maturity of these items. Property and Equipment Property and equipment, which consists of furniture and fixtures, computers and office equipment, scientific equipment and leasehold improvements, are stated at cost and depreciated over the estimated useful lives of the assets (three to five years) using the straight-line method. Leasehold improvements are amortized over the shorter of their estimated useful lives or the lease term. Long-Lived Assets The Company regularly reviews the carrying value and estimated lives of all of its long-lived assets, including property and equipment, to determine whether indicators of impairment may exist which warrant adjustments to carrying values or estimated useful lives. The determinants used for this evaluation include management’s estimate of the asset’s ability to generate positive income from operations and positive cash flow in future periods, as well as the strategic significance of the assets to the Company’s business objective. Should an impairment exist, the impairment loss would be measured based on the excess of the carrying amount of the asset’s fair value. The Company has not recognized any impairment losses through December 31, 2018. Revenue Recognition Under the relevant accounting literature, 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 receive in exchange for those goods or services. The Company performs the following five steps in order to determine revenue recognition for contracts: (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. At contract inception, the Company identifies the performance obligations in the contract by assessing whether the goods or services promised within each contract are distinct. Revenue is then recognized for the amount of the transaction price that is allocated to the respective performance obligation when, or as, the performance obligation is satisfied. In a contract with multiple performance obligations, the Company must develop estimates and assumptions that require judgment to determine the underlying stand-alone selling price for each performance obligation, which determines how the transaction price is allocated among the performance obligations. The estimation of the stand-alone selling price(s) may include estimates regarding forecasted revenues or costs, development timelines, discount rates, and probabilities of technical and regulatory success. The Company evaluates each performance obligation to determine if it can be satisfied at a point in time or over time. Any change made to estimated progress towards completion of a performance obligation and, therefore, revenue recognized will be recorded as a change in estimate. In addition, variable consideration must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price. If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in a contract, the Company recognizes revenues from the transaction price allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from the allocated transaction price. The Company evaluates the measure of progress at each reporting period and, if necessary, adjusts the measure of performance and related revenue or expense recognition as a change in estimate. At the inception of each arrangement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being reached. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s or a collaboration partner’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of milestones that are within its or a collaboration partner’s control, such as operational developmental milestones and any related constraint, and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which will affect collaboration revenues and earnings in the period of adjustment. Revisions to the Company’s estimate of the transaction price may also result in negative collaboration revenues and earnings in the period of adjustment. For arrangements that include sales-based royalties, including commercial milestone payments based on the level of sales, and a license is deemed to be the predominant item to which the royalties relate, the Company will recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied, or partially satisfied. To date, the Company has not recognized any royalty revenue from collaborative arrangements. In December 2016, the Company entered into an Option, Collaboration and License Agreement (the Collaboration Agreement) and an Investment Agreement (the Investment Agreement) with Novartis Pharma AG (Novartis). The Company concluded that there were two significant performance obligations under the Collaboration Agreement: the license and the research and development services, but that the license is not distinct from the research and development services as Novartis cannot obtain value from the license without the research and development services, which the Company is uniquely able to perform. The Company concluded that progress towards completion of the performance obligations related to the Collaboration Agreement is best measured in an amount proportional to the collaboration expenses incurred and the total estimated collaboration expenses. The Company periodically reviews and updates the estimated collaboration expenses, when appropriate, which adjusts the percentage of revenue that is recognized for the period. While such changes to the Company’s estimates have no impact on the Company’s reported cash flows, the amount of revenue recorded in the period could be materially impacted. The transaction price to be recognized as revenue under the Collaboration Agreement consists of the upfront payment, option exercise fee, deemed revenue from the premium paid by Novartis under the Investment Agreement and estimated reimbursable research and development costs. Certain expenses directly related to execution of the Collaboration Agreement were capitalized as assets on the balance sheet and are being expensed in a manner consistent with the methodology used for recognizing revenue. Potential future payments for variable consideration, such as clinical, regulatory or commercial milestones, will be recognized when it is probable that, if recorded, a significant reversal will not take place. Potential future royalty payments will be recorded as revenue when the associated sales occur. See Note 9 – Collaboration and License Agreements for further information. Research and Development Expenses All research and development costs are expensed as incurred. Income Taxes The Company’s policy related to accounting for uncertainty in income taxes prescribes a recognition threshold and measurement attribute criteria for the financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. For those benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by taxing authorities. As of December 31, 2018, there are no unrecognized tax benefits included in the balance sheet that would, if recognized, affect the Company’s effective tax rate. The Company has not recognized interest and penalties in the balance sheets or statements of operations and comprehensive loss. The Company is subject to U.S. and California taxation. As of December 31, 2018, the Company’s tax years beginning 2005 to date are subject to examination by taxing authorities. Stock-Based Compensation Stock-based compensation expense for stock option grants under the Company’s stock option plans is recorded at the estimated fair value of the award as of the grant date and is recognized as expense on a straight-line basis over the requisite service period of the stock-based award, and forfeitures are recognized as they occur. The fair value is estimated using the Black-Scholes model with the assumptions noted in the following table. The expected life of stock options is based on the simplified method described in the Securities and Exchange Commission (SEC) Staff Accounting Bulletin No. 107. The expected volatility of stock options is based upon the historical volatility of a number of publicly traded companies in similar stages of clinical development. The risk-free interest rate is based on the average yield of five- and seven-year U.S. Treasury Bills as of the valuation date. Year Ended December 31, 2018 2017 2016 Assumptions Risk-free interest rate 2.55% - 3.03% 1.83% - 2.13% 1.15% - 1.55% Expected dividend yield 0% 0% 0% Expected volatility 94% - 100% 93% - 97% 84% Expected term (in years) 5.5 - 6.1 5.5 - 6.1 5.5 - 6.1 Stock-based compensation expense for employee stock purchases under the Company’s 2013 Employee Stock Purchase Plan (the ESPP) is recorded at the estimated fair value of the purchase as of the plan enrollment date and is recognized as expense on a straight-line basis over the applicable six-month ESPP offering period. The fair value is estimated using the Black-Scholes model with inputs that include the applicable risk-free interest rate, expected dividend yield, expected volatility and expected term. Comprehensive Loss The Company is required to report all components of comprehensive loss, including net loss, in the financial statements in the period in which they are recognized. Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from nonowner sources, including unrealized gains and losses on marketable securities. Comprehensive gains (losses) have been reflected in the statements of operations and comprehensive loss for all periods presented. Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is used in making decisions regarding resource allocation and assessing performance. To date, the Company has viewed its operations and managed its business as one segment operating primarily in the United States. 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 during the period. Diluted net loss per share is computed by dividing the net loss by the weighted average number of common shares and common share equivalents outstanding for the period. Common stock equivalents are only included when their effect is dilutive. The Company’s potentially dilutive securities have been excluded from the computation of diluted net loss per share in the periods in which they would be anti-dilutive. For all periods presented, there is no difference in the number of shares used to compute basic and diluted shares outstanding due to the Company’s net loss position. The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because to do so would be anti-dilutive (in thousands): December 31, 2018 2017 2016 Warrants to purchase common stock 13 150 150 Common stock options issued and outstanding 5,385 4,826 3,394 Shares issuable upon conversion of convertible note payable — 2,965 — ESPP shares pending issuance 8 5 2 Total 5,406 7,946 3,546 Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606). In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718). Revenue from Contracts with Customers (Topic 606) In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808). Collaborative Arrangements (Topic 808) Revenue from Contracts with Customers (Topic 606) Revenue from Contracts with Customers (Topic 606)

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1: Includes financial instruments for which quoted market prices for identical instruments are available in active markets. Level 2: Includes financial instruments for which there are inputs other than quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets with insufficient volume or infrequent transaction (less active markets) or model-driven valuations in which significant inputs are observable or can be derived principally from, or corroborated by, observable market data. Level 3: Includes financial instruments for which fair value is derived from valuation techniques in which one or more significant inputs are unobservable, including management’s own assumptions. Below is a summary of assets, including cash equivalents and marketable securities, measured at fair value as of December 31, 2018 and 2017 (in thousands): Fair Value Measurements Using December 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Money market funds $ 8,000 $ 8,000 $ — $ — Corporate debt securities 30,620 — 30,620 — Total $ 38,620 $ 8,000 $ 30,620 $ — Fair Value Measurements Using December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Money market funds $ 12,218 $ 12,218 $ — $ — Corporate debt securities 61,774 — 61,774 — Total $ 73,992 $ 12,218 $ 61,774 $ — The Company’s marketable securities, consisting principally of debt securities, are classified as available-for-sale, are stated at fair value, and consist of Level 2 financial instruments in the fair value hierarchy. The Company determines the fair value of its debt security holdings based on pricing from a service provider. The service provider values the securities based on using market prices from a variety of industry-standard independent data providers. Such market prices may be quoted prices in active markets for identical assets (Level 1 inputs) or pricing determined using inputs other than quoted prices that are observable either directly or indirectly (Level 2 inputs), such as yield curve, volatility factors, credit spreads, default rates, loss severity, current market and contractual prices for the underlying instruments or debt, broker and dealer quotes, as well as other relevant economic measures.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Marketable Securities	4. Marketable Securities The Company invests its excess cash in money market funds and debt instruments of financial institutions, corporations, government sponsored entities and municipalities. The following tables summarize the Company’s marketable securities (in thousands): As of December 31, 2018 Maturity (in years) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Corporate debt securities 1 or less $ 29,144 $ — $ (17 ) $ 29,127 Total $ 29,144 $ — $ (17 ) $ 29,127 As of December 31, 2017 Maturity (in years) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Corporate debt securities 1 or less $ 58,851 $ — $ (77 ) $ 58,774 Total $ 58,851 $ — $ (77 ) $ 58,774

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Property and Equipment	5. Property and Equipment Property and equipment consist of the following (in thousands): December 31, 2018 2017 Furniture and fixtures $ 334 $ 334 Equipment 208 143 Leasehold improvements 147 152 689 629 Less accumulated depreciation and amortization (535 ) (450 ) Total $ 154 $ 179 Depreciation expense related to property and equipment was $91,000, $108,000 and $106,000 for the years ended December 31, 2018, 2017 and 2016, respectively.

Notes Payable

Notes Payable	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Notes Payable	6. Notes Payable In July 2010, the Company issued to Pfizer Inc. (Pfizer) a $1.0 million promissory note (the Pfizer Note). The Pfizer Note bore interest at a rate of 7% per annum and was scheduled to mature on July 29, 2020. Interest was payable on a quarterly basis. On January 24, 2017, the Company voluntarily prepaid the entire balance of the outstanding principal and accrued and unpaid interest of the Pfizer Note in the amount of $1,004,861. Prior to the prepayment of the Pfizer Note, the Company recorded the Pfizer Note on the balance sheet at face value. Based on borrowing rates available to the Company for loans with similar terms, the Company believed that the fair value of the Pfizer Note approximated its carrying value. The fair value measurement was categorized within Level 3 of the fair value hierarchy. On February 15, 2017, the Company issued a convertible promissory note (the Novartis Note) in the principal amount of $15.0 million, pursuant to the Investment Agreement. The Novartis Note bore interest on the unpaid principal balance at a rate of 6% per annum and had a scheduled maturity date of December 31, 2019. The terms of the Novartis Note allowed the Company to convert the principal and accrued interest into the Company’s common stock at a conversion price equal to 120% of the 20-day trailing average closing price per share of the common stock immediately prior to the conversion date. The ability to borrow and repay the debt at a discount using shares of the Company’s common stock was deemed to be additional, foregone revenue attributable to the Collaboration Agreement, which the Company imputed and recorded as both a receivable from Novartis and a liability (deferred revenue) of $2.5 million at the inception of the Collaboration Agreement and the Investment Agreement. On February 15, 2017, the Company recorded the $15.0 million proceeds from the issuance of the Novartis Note as a convertible note payable in the amount of $12.5 million and a reduction of the outstanding receivable from Novartis of $2.5 million. On December 5, 2018, the Company, at its option, converted the entire outstanding principal of $15.0 million and accrued and unpaid interest of the Novartis Note into 2,882,519 shares of the Company’s common stock at a conversion price of $5.77 per share. The Company elected to account for the Novartis Note under the fair value option. Prior to conversion of the Novartis Note, the Company concluded that the fair value of the Novartis Note remained at $12.5 million, plus the related accrued interest, due to its conversion features. The fair value measurement was categorized within Level 2 of the fair value hierarchy.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	7. Stockholders’ Equity Common Stock In May 2017, the Company completed a public offering of 5,980,000 shares of its common stock at a public offering price of $5.50 per share. The shares were registered pursuant to the Company’s Registration Statement on Form S-3 filed on August 14, 2014. The Company received net proceeds of $30.6 million, after deducting underwriting discounts and commissions and offering-related transaction costs. Immediately following the offering, the Company used $11.2 million of the net proceeds to repurchase and retire 2,166,836 shares of its common stock from funds affiliated with Advent Private Equity (collectively Advent) at a price of $5.17 per share , which is equal to the net proceeds per share that the Company received from the offering, before expenses, pursuant to a stock purchase agreement the Company entered into with Advent in May 2017. On August 2, 2018, the Company entered into an At Market Issuance Sales Agreement (the Sales Agreement) with Stifel, Nicolaus & Company, Incorporated (Stifel), pursuant to which the Company may sell from time to time, at its option, up to an aggregate of $35.0 million of shares of its common stock through Stifel, as sales agent. Sales of the Company’s common stock made pursuant to the Sales Agreement, if any, will be made on Nasdaq, under the Company’s Registration Statement on Form S-3 filed on August 17, 2017 and declared effective by the SEC on November 9, 2017, by means of ordinary brokers’ transactions at market prices. Additionally, under the terms of the Sales Agreement, the Company may also sell shares of its common stock through Stifel, on Nasdaq or otherwise, at negotiated prices or at prices related to the prevailing market price. The Company will pay a commission rate equal to up to 3.0% of the gross sales price per share sold. As of December 31, 2018, the Company has incurred legal and accounting costs of $0.1 million related to the Sales Agreement, which are recorded in other assets on the balance sheet until such time as the Company issues shares pursuant to the Sales Agreement. As of December 31, 2018, no shares were issued pursuant to the Sales Agreement. Warrants In 2013, the Company issued warrants exercisable for 1,124,026 shares of Series B preferred stock, at an exercise price of $0.90 per share, to certain existing investors in conjunction with a private placement (the 2013 Warrants) and warrants exercisable for 111,112 shares of Series B preferred stock, at an exercise price of $0.90 per share, to Oxford Finance LLC and Silicon Valley Bank in conjunction with the Company’s entry into a loan and security agreement (the Lender Warrants). Upon completion of the Company’s initial public offering (IPO), the 2013 Warrants and the Lender Warrants became exercisable for 136,236 and 13,468 shares of common stock, respectively, at an exercise price of $7.43 per share. The 2013 Warrants expired on May 30, 2018, and the Lender Warrants will expire on July 3, 2023. Stock Options The Company adopted an Equity Incentive Plan in 2006 (the 2006 Plan) under which 1,030,303 shares of common stock were reserved for issuance to employees, nonemployee directors and consultants of the Company. In July 2013, the Company adopted an Incentive Award Plan (the 2013 Plan), which provides for the grant of incentive stock options, nonstatutory stock options, rights to purchase restricted stock, stock appreciation rights, dividend equivalents, stock payments and restricted stock units to eligible recipients. Recipients of incentive stock options shall be eligible to purchase shares of the Company’s common stock at an exercise price equal to no less than the estimated fair market value of such stock on the date of grant. The maximum term of options granted under the 2013 Plan is ten years. Except for annual grants to non-employee directors, which vest one year from the grant date, options generally vest 25% on the first anniversary of the original vesting date, with the balance vesting monthly over the remaining three years. Pursuant to the 2013 Plan, the Company’s management is authorized to grant stock options to the Company’s employees, directors and consultants. The number of shares available for future grant under the 2013 Plan will automatically increase each year by an amount equal to the least of (1) 1,000,000 shares of the Company’s common stock, (2) 5% of the outstanding shares of the Company’s common stock as of the last day of the Company’s immediately preceding fiscal year, or (3) such other amount as the Company’s board of directors may determine. Shares that remain available, that expire or otherwise terminate without having been exercised in full, and unvested shares that are forfeited to or repurchased by the Company under the 2006 Plan will roll into the 2013 Plan. As of December 31, 2018, a total of 844,191 options remain available for future grant under the 2013 Plan. On August 31, 2017, in connection with the appointment of its new Executive Vice President, Chief Operating Officer and Chief Financial Officer, the Company granted stock options to purchase 525,000 shares of the Company’s common stock outside of its stock option plans. The following table summarizes the Company’s stock option activity under all stock option plans for the three years ended December 31, 2018 (options in thousands): Number of Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in years) Outstanding at December 31, 2015 2,465 $ 6.54 Granted 1,133 1.96 Exercised (61 ) 0.92 Forfeited/cancelled/expired (143 ) 6.65 Outstanding at December 31, 2016 3,394 5.10 Granted 1,733 4.91 Exercised (79 ) 1.32 Forfeited/cancelled/expired (222 ) 6.09 Outstanding at December 31, 2017 4,826 5.05 Granted 943 5.08 Exercised (211 ) 1.71 Forfeited/cancelled/expired (173 ) 4.83 Outstanding at December 31, 2018 5,385 $ 5.20 7.1 Exercisable at December 31, 2018 3,400 $ 5.46 6.3 The weighted-average fair value of options granted for the years ended December 31, 2018, 2017 and 2016 were $3.93, $3.79 and $1.38, respectively. The total intrinsic value of stock options exercised during the years ended December 31, 2018, 2017 and 2016 were $0.6 million, $0.3 million and $0.1 million, respectively. At December 31, 2018, the intrinsic value of options outstanding and exercisable were $0.2 million and $0.2 million, respectively. Employee Stock Purchase Plan In July 2013, the Company adopted the ESPP, which permits participants to contribute up to 20% of their eligible compensation during defined rolling six-month periods to purchase the Company’s common stock. The purchase price of the shares will be 85% of the lower of the fair market value of the Company’s common stock on the first day of trading of the offering period or on the applicable purchase date. The ESPP was activated in November 2014. The Company issued 36,296, 24,303 and 26,876 shares of common stock under the ESPP for the years ended December 31, 2018, 2017 and 2016, respectively. The Company had an outstanding liability of $28,936, $16,367 and $4,521 at December 31, 2018, 2017 and 2016, respectively, which is included in accounts payable and accrued expenses on the balance sheets, for employee contributions to the ESPP for shares pending issuance at the end of the offering period. Stock-Based Compensation The Company recorded stock-based compensation of $3.8 million, $4.1 million and $3.4 million for the years ended December 31, 2018, 2017 and 2016, respectively. Unrecognized compensation expense at December 31, 2018 was $6.2 million, which is expected to be recognized over a weighted-average vesting term of 2.4 years. Common Stock Reserved for Future Issuance The following shares of common stock were reserved for future issuance at December 31, 2018 and 2017 (in thousands): December 31, 2018 2017 Warrants to purchase common stock 13 150 Common stock options issued and outstanding 5,385 4,826 Common stock authorized for future option grants 844 614 Common stock authorized for the ESPP 495 531 Shares issuable upon conversion of convertible note payable — 2,965 Total 6,737 9,086

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	8. Income Taxes The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by the federal and state jurisdictions where applicable. There are currently no pending income tax examinations. The Company’s tax years for 2005 and forward are subject to examination by the federal and California tax authorities due to the carryforward of unutilized net operating losses (NOLs) and research and development credits. In accordance with the Tax Cut and Jobs Act, or the Tax Act, which was enacted on December 22, 2017, Pursuant to Internal Revenue Code (IRC) Sections 382 and 383, annual use of the Company’s NOL or research and development credit carryforwards may be limited in the event a cumulative change in ownership of more than 50% occurs within a three-year period. The Company previously completed a study to assess whether an ownership change, as defined by IRC Section 382, had occurred from its formation through December 31, 2017. Based upon this study, the Company determined that ownership changes had occurred in 2006 and 2013 but Significant components of the Company’s deferred tax assets at December 31, 2018 and 2017 are shown below (in thousands): December 31, 2018 2017 Deferred tax assets Net operating loss carryovers $ 31,135 $ 25,202 Research and development tax credits 8,641 7,529 Intangibles 379 480 Stock options 2,255 1,840 Compensation 452 406 Deferred revenue 2,642 5,605 Other 62 62 Total gross deferred tax assets 45,566 41,124 Less valuation allowance (45,566 ) (41,124 ) Net deferred tax assets $ — $ — A reconciliation of the statutory tax rates and the effective tax rates for the years ended December 31, 2018, 2017 and 2016 is as follows: December 31, 2018 2017 2016 Statutory rate 21.00 % 34.00 % 34.00 % State tax, net of federal benefit 0.00 % 0.00 % 0.00 % Valuation allowance (25.18 %) 51.50 % (34.26 %) Federal tax rate change 0.00 % (93.30 %) 0.00 % General business credits 6.18 % 10.80 % 0.00 % Other (2.00 %) (3.00 %) 0.26 % Effective tax rate — % — % — % At December 31, 2018, the Company had federal and state NOL carryforwards of $122.8 million and $76.4 million, respectively. The federal and state NOL carryforwards begin to expire in 2028, unless previously utilized. The federal NOL carryforwards generated after 2017 have an indefinite carryforward life. The Company also has federal, including orphan drug, and state research credit carryforwards of $8.8 million and $2.4 million, respectively. The federal research credit carryforwards will begin expiring in 2027, unless previously utilized. The state research credit will carry forward indefinitely. The change in the valuation allowance is an increase of $4.4 million for the year ended December 31, 2018, a decrease of $9.0 million for the year ended December 31, 2017 and an increase of $10.2 million for the year ended December 31, 2016. The Company recognizes the impact of uncertain income tax positions at the largest amount that is “more likely than not” to be sustained upon audit by the relevant taxing authority. An uncertain tax position will not be recognized if it has less than a 50% likelihood of being sustained. The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands): 2018 2017 2016 Balance at beginning of year $ 1,932 $ 1,319 $ 981 Additions based on tax positions related to the current year 289 613 338 Balance at end of year $ 2,221 $ 1,932 $ 1,319 The Company does not expect that the unrecognized tax benefits will change within 12 months of this reporting date. Due to the existence of the valuation allowance, future changes in the Company’s unrecognized tax benefits will not impact the Company’s effective tax rate. The Company’s policy is to recognize interest and penalties related to income tax matters in income tax expense. For the years ended December 31, 2018, 2017 and 2016, the Company has not recognized any interest or penalties related to income taxes.

Collaboration and License Agree

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreements	9. Collaboration and License Agreements In December 2016, the Company entered into the Collaboration Agreement, pursuant to which the Company granted Novartis an exclusive option to collaborate with the Company to develop products containing emricasan. Pursuant to the Collaboration Agreement, the Company received a non-refundable upfront payment of $50.0 million from Novartis. In May 2017, Novartis exercised its option under the Collaboration Agreement. In July 2017, the Company received a $7.0 million option exercise payment, at which time the license under the Collaboration Agreement became effective (the License Effective Date). Under the Collaboration Agreement, the Company is eligible to receive up to an aggregate of $650.0 million in milestone payments over the term of the Collaboration Agreement, contingent on the achievement of certain development, regulatory and commercial milestones, as well as royalties or profit and loss sharing on future product sales in the United States, if any. Pursuant to the Collaboration Agreement, the Company is responsible for completing its three ongoing Phase 2b trials. Novartis will generally pay 50% of the Company’s Phase 2b and observational study costs pursuant to an agreed upon budget. Upon completion of the ongoing Phase 2b trials, Novartis will assume 100% of the observational study costs. Novartis will assume full responsibility for emricasan’s Phase 3 development and all combination product development. Unless terminated earlier, the Collaboration Agreement will remain in effect on a product-by-product and country-by-country basis until Novartis’ royalty obligations expire. Novartis has certain termination rights in the event of a mandated clinical trial hold for any product containing emricasan as its sole active ingredient. Additionally, Novartis has the right to terminate the Collaboration Agreement without cause upon 180 days prior written notice to the Company. In such event, the license granted to Novartis will be terminated and revert to the Company. In the event Novartis terminates the Collaboration Agreement due to the Company’s uncured material breach or insolvency, the license granted to Novartis pursuant to the Collaboration Agreement will become irrevocable, and Novartis will be required to continue to make all milestone and royalty payments otherwise due to the Company under the Collaboration Agreement, provided that if the Company materially breaches the Collaboration Agreement such that the rights licensed to Novartis or the commercial prospects of the emricasan products are seriously impaired, the milestone and royalty payments will be reduced by 50%. Concurrent with entry into the Collaboration Agreement, the Company entered into the Investment Agreement, whereby the Company was able to borrow up to $15.0 million at a rate of 6% per annum, under one or two notes, with a maturity date of December 31, 2019. On February 15, 2017, the Company issued the Novartis Note in the principal amount of $15.0 million pursuant to the Investment Agreement. The terms of the Novartis Note allowed the Company to convert the principal and accrued interest into the Company’s common stock at a conversion price equal to 120% of the 20-day trailing average closing price per share of the common stock immediately prior to the conversion date. On December 5, 2018, the Company, at its option, converted the entire outstanding principal of $15.0 million and accrued and unpaid interest of the Novartis Note into 2,882,519 shares of the Company’s common stock at a conversion price of $5.77 per share. Under the Collaboration Agreement, there are two significant performance obligations: the license and the research and development services, but the license is not distinct from the research and development services as Novartis cannot obtain value from the license without the research and development services, which the Company is uniquely able to perform. The Company concluded that progress towards completion of the performance obligations related to the Collaboration Agreement is best measured in an amount proportional to the collaboration expenses incurred and the total estimated collaboration expenses. The transaction price to be recognized as revenue under the Collaboration Agreement consists of the upfront payment, option exercise fee, deemed revenue from the premium paid by Novartis under the Investment Agreement and estimated reimbursable research and development costs. Certain expenses directly related to execution of the Collaboration Agreement were capitalized as assets on the balance sheet and are being expensed in a manner consistent with the methodology used for recognizing revenue. A reconciliation of the opening and closing balances of deferred revenue related to the Collaboration Agreement, which represents the unrecognized balance of the transaction price, is as follows (in thousands): Deferred Revenue at Reporting Date Balance at December 31, 2017 $ 26,691 Cumulative effect of adoption of accounting standard 1,299 Additions to deferred revenue 18,486 Revenue recognized (33,586 ) Balance at December 31, 2018 $ 12,890 The Company expects to recognize deferred revenue related to the Collaboration Agreement as follows (in thousands): Total Within 1 Year 1-2 Years Deferred revenue $ 12,890 $ 10,075 $ 2,815 Total $ 12,890 $ 10,075 $ 2,815 A reconciliation of the opening and closing balances of deferred costs related to execution of the Collaboration Agreement is as follows (in thousands): Deferred Costs at Reporting Date Balance at December 31, 2017 $ — Cumulative effect of adoption of accounting standard 687 Costs recognized (377 ) Balance at December 31, 2018 $ 310 The Company expects to recognize deferred costs related to execution of the Collaboration Agreement as follows (in thousands): Total Within 1 Year 1-2 Years Deferred costs $ 310 $ 242 $ 68 Total $ 310 $ 242 $ 68

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2018
Postemployment Benefits [Abstract]
Employee Benefits	10. Employee Benefits Effective December 4, 2006, the Company has a defined contribution 401(k) plan for its employees. Employees are eligible to participate in the plan beginning on the first day of employment. Under the terms of the plan, employees may make voluntary contributions as a percent of compensation. Effective January 1, 2007,

Commitments

Commitments	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments	11. Commitments In February 2014, the Company entered into a noncancelable operating lease agreement (the Lease) for certain office space with a lease term from July 2014 through December 2019 and a renewal option for an additional five years. In May 2015, the Company entered into a first amendment to the Lease (the First Lease Amendment) for additional office space starting in September 2015 through September 2020. The First Lease Amendment also extended the term of the Lease to September 2020. The monthly base rent under the Lease and the First Lease Amendment increases approximately 3% annually from approximately $33,000 in 2015 to approximately $39,000 in 2020. As of December 31, 2018, future annual minimum payments under the Lease and the First Lease Amendment are as follows (in thousands): 2019 $ 437 2020 351 Total $ 788 Rent expense was $0.4 million for each of the years ended December 31, 2018, 2017 and 2016. In July 2010, the Company entered into a stock purchase agreement with Pfizer, pursuant to which the Company acquired all of the outstanding stock of Idun Pharmaceuticals, Inc., which was subsequently spun off to the Company’s stockholders in January 2013. Under the stock purchase agreement, the Company may be required to make payments to Pfizer totaling $18.0 million upon the achievement of specified regulatory milestones.

Quarterly Financial Data

Quarterly Financial Data	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	12. Quarterly Financial Data (unaudited) The following tables summarize the unaudited quarterly financial data for the last two fiscal years (in thousands, except per share data): 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenues $ 9,737 $ 8,774 $ 7,666 $ 7,409 Total operating expenses 14,794 13,331 12,324 11,414 Total other income 39 60 69 99 Net loss (5,018 ) (4,497 ) (4,589 ) (3,906 ) Net loss per share, basic and diluted (1) (0.17 ) (0.15 ) (0.15 ) (0.13 ) 2017 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenues $ 6,998 $ 10,008 $ 9,566 $ 8,805 Total operating expenses 10,689 15,412 13,614 13,212 Total other income (expense) 68 (13 ) 48 51 Net loss (3,623 ) (5,417 ) (4,000 ) (4,356 ) Net loss per share, basic and diluted (1) (0.14 ) (0.19 ) (0.13 ) (0.15 ) (1)

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with accounting principles generally accepted in the United States (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash. Additionally, the Company established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity from the date of purchase of three months or less to be cash equivalents. Cash and cash equivalents include cash in readily available checking and money market accounts.
Marketable Securities	Marketable Securities The Company classifies its marketable securities as available-for-sale and records such assets at estimated fair value in the balance sheets, with unrealized gains and losses, if any, reported as a component of other comprehensive income (loss) within the statements of operations and comprehensive loss and as a separate component of stockholders’ equity. The Company classifies marketable securities with remaining maturities greater than one year as current assets because such marketable securities are available to fund the Company’s current operations. The Company invests its excess cash balances primarily in corporate debt securities and money market funds with strong credit ratings. Realized gains and losses are calculated on the specific identification method and recorded as interest income. There were no realized gains and losses for the years ended December 31, 2018, 2017 and 2016. At each balance sheet date, the Company assesses available-for-sale securities in an unrealized loss position to determine whether the unrealized loss is other-than-temporary. The Company considers factors including: the significance of the decline in value compared to the cost basis, underlying factors contributing to a decline in the prices of securities in a single asset class, the length of time the market value of the security has been less than its cost basis, the security’s relative performance versus its peers, sector or asset class, expected market volatility and the market and economy in general. When the Company determines that a decline in the fair value below its cost basis is other-than-temporary, the Company recognizes an impairment loss in the period in which the other-than-temporary decline occurred. There have been no other-than-temporary declines in the value of marketable securities for the years ended December 31, 2018, 2017 and 2016, as it is more likely than not the Company will hold the securities until maturity or a recovery of the cost basis.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of collaboration receivables, prepaid and other current assets, and accounts payable and accrued expenses are reasonable estimates of their fair value because of the short maturity of these items.
Property and Equipment	Property and Equipment Property and equipment, which consists of furniture and fixtures, computers and office equipment, scientific equipment and leasehold improvements, are stated at cost and depreciated over the estimated useful lives of the assets (three to five years) using the straight-line method. Leasehold improvements are amortized over the shorter of their estimated useful lives or the lease term.
Long-Lived Assets	Long-Lived Assets The Company regularly reviews the carrying value and estimated lives of all of its long-lived assets, including property and equipment, to determine whether indicators of impairment may exist which warrant adjustments to carrying values or estimated useful lives. The determinants used for this evaluation include management’s estimate of the asset’s ability to generate positive income from operations and positive cash flow in future periods, as well as the strategic significance of the assets to the Company’s business objective. Should an impairment exist, the impairment loss would be measured based on the excess of the carrying amount of the asset’s fair value. The Company has not recognized any impairment losses through December 31, 2018.
Revenue Recognition	Revenue Recognition Under the relevant accounting literature, 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 receive in exchange for those goods or services. The Company performs the following five steps in order to determine revenue recognition for contracts: (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. At contract inception, the Company identifies the performance obligations in the contract by assessing whether the goods or services promised within each contract are distinct. Revenue is then recognized for the amount of the transaction price that is allocated to the respective performance obligation when, or as, the performance obligation is satisfied. In a contract with multiple performance obligations, the Company must develop estimates and assumptions that require judgment to determine the underlying stand-alone selling price for each performance obligation, which determines how the transaction price is allocated among the performance obligations. The estimation of the stand-alone selling price(s) may include estimates regarding forecasted revenues or costs, development timelines, discount rates, and probabilities of technical and regulatory success. The Company evaluates each performance obligation to determine if it can be satisfied at a point in time or over time. Any change made to estimated progress towards completion of a performance obligation and, therefore, revenue recognized will be recorded as a change in estimate. In addition, variable consideration must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price. If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in a contract, the Company recognizes revenues from the transaction price allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from the allocated transaction price. The Company evaluates the measure of progress at each reporting period and, if necessary, adjusts the measure of performance and related revenue or expense recognition as a change in estimate. At the inception of each arrangement that includes milestone payments, the Company evaluates whether the milestones are considered probable of being reached. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s or a collaboration partner’s control, such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. At the end of each reporting period, the Company re-evaluates the probability of achievement of milestones that are within its or a collaboration partner’s control, such as operational developmental milestones and any related constraint, and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which will affect collaboration revenues and earnings in the period of adjustment. Revisions to the Company’s estimate of the transaction price may also result in negative collaboration revenues and earnings in the period of adjustment. For arrangements that include sales-based royalties, including commercial milestone payments based on the level of sales, and a license is deemed to be the predominant item to which the royalties relate, the Company will recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied, or partially satisfied. To date, the Company has not recognized any royalty revenue from collaborative arrangements. In December 2016, the Company entered into an Option, Collaboration and License Agreement (the Collaboration Agreement) and an Investment Agreement (the Investment Agreement) with Novartis Pharma AG (Novartis). The Company concluded that there were two significant performance obligations under the Collaboration Agreement: the license and the research and development services, but that the license is not distinct from the research and development services as Novartis cannot obtain value from the license without the research and development services, which the Company is uniquely able to perform. The Company concluded that progress towards completion of the performance obligations related to the Collaboration Agreement is best measured in an amount proportional to the collaboration expenses incurred and the total estimated collaboration expenses. The Company periodically reviews and updates the estimated collaboration expenses, when appropriate, which adjusts the percentage of revenue that is recognized for the period. While such changes to the Company’s estimates have no impact on the Company’s reported cash flows, the amount of revenue recorded in the period could be materially impacted. The transaction price to be recognized as revenue under the Collaboration Agreement consists of the upfront payment, option exercise fee, deemed revenue from the premium paid by Novartis under the Investment Agreement and estimated reimbursable research and development costs. Certain expenses directly related to execution of the Collaboration Agreement were capitalized as assets on the balance sheet and are being expensed in a manner consistent with the methodology used for recognizing revenue. Potential future payments for variable consideration, such as clinical, regulatory or commercial milestones, will be recognized when it is probable that, if recorded, a significant reversal will not take place. Potential future royalty payments will be recorded as revenue when the associated sales occur. See Note 9 – Collaboration and License Agreements for further information.
Research and Development Expenses	Research and Development Expenses All research and development costs are expensed as incurred.
Income Taxes	Income Taxes The Company’s policy related to accounting for uncertainty in income taxes prescribes a recognition threshold and measurement attribute criteria for the financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. For those benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by taxing authorities. As of December 31, 2018, there are no unrecognized tax benefits included in the balance sheet that would, if recognized, affect the Company’s effective tax rate. The Company has not recognized interest and penalties in the balance sheets or statements of operations and comprehensive loss. The Company is subject to U.S. and California taxation. As of December 31, 2018, the Company’s tax years beginning 2005 to date are subject to examination by taxing authorities.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense for stock option grants under the Company’s stock option plans is recorded at the estimated fair value of the award as of the grant date and is recognized as expense on a straight-line basis over the requisite service period of the stock-based award, and forfeitures are recognized as they occur. The fair value is estimated using the Black-Scholes model with the assumptions noted in the following table. The expected life of stock options is based on the simplified method described in the Securities and Exchange Commission (SEC) Staff Accounting Bulletin No. 107. The expected volatility of stock options is based upon the historical volatility of a number of publicly traded companies in similar stages of clinical development. The risk-free interest rate is based on the average yield of five- and seven-year U.S. Treasury Bills as of the valuation date. Year Ended December 31, 2018 2017 2016 Assumptions Risk-free interest rate 2.55% - 3.03% 1.83% - 2.13% 1.15% - 1.55% Expected dividend yield 0% 0% 0% Expected volatility 94% - 100% 93% - 97% 84% Expected term (in years) 5.5 - 6.1 5.5 - 6.1 5.5 - 6.1 Stock-based compensation expense for employee stock purchases under the Company’s 2013 Employee Stock Purchase Plan (the ESPP) is recorded at the estimated fair value of the purchase as of the plan enrollment date and is recognized as expense on a straight-line basis over the applicable six-month ESPP offering period. The fair value is estimated using the Black-Scholes model with inputs that include the applicable risk-free interest rate, expected dividend yield, expected volatility and expected term.
Comprehensive Loss	Comprehensive Loss The Company is required to report all components of comprehensive loss, including net loss, in the financial statements in the period in which they are recognized. Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from nonowner sources, including unrealized gains and losses on marketable securities. Comprehensive gains (losses) have been reflected in the statements of operations and comprehensive loss for all periods presented.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is used in making decisions regarding resource allocation and assessing performance. To date, the Company has viewed its operations and managed its business as one segment operating primarily in the United States.
Net Loss Per Share	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 during the period. Diluted net loss per share is computed by dividing the net loss by the weighted average number of common shares and common share equivalents outstanding for the period. Common stock equivalents are only included when their effect is dilutive. The Company’s potentially dilutive securities have been excluded from the computation of diluted net loss per share in the periods in which they would be anti-dilutive. For all periods presented, there is no difference in the number of shares used to compute basic and diluted shares outstanding due to the Company’s net loss position. The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because to do so would be anti-dilutive (in thousands): December 31, 2018 2017 2016 Warrants to purchase common stock 13 150 150 Common stock options issued and outstanding 5,385 4,826 3,394 Shares issuable upon conversion of convertible note payable — 2,965 — ESPP shares pending issuance 8 5 2 Total 5,406 7,946 3,546
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606). In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718). Revenue from Contracts with Customers (Topic 606) In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808). Collaborative Arrangements (Topic 808) Revenue from Contracts with Customers (Topic 606) Revenue from Contracts with Customers (Topic 606)

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of Black-Scholes Option Pricing Model Assumptions	The fair value is estimated using the Black-Scholes model with the assumptions noted in the following table. The expected life of stock options is based on the simplified method described in the Securities and Exchange Commission (SEC) Staff Accounting Bulletin No. 107. The expected volatility of stock options is based upon the historical volatility of a number of publicly traded companies in similar stages of clinical development. The risk-free interest rate is based on the average yield of five- and seven-year U.S. Treasury Bills as of the valuation date. Year Ended December 31, 2018 2017 2016 Assumptions Risk-free interest rate 2.55% - 3.03% 1.83% - 2.13% 1.15% - 1.55% Expected dividend yield 0% 0% 0% Expected volatility 94% - 100% 93% - 97% 84% Expected term (in years) 5.5 - 6.1 5.5 - 6.1 5.5 - 6.1
Summary of Outstanding Potentially Dilutive Securities Excluded in Calculation of Diluted Net Loss Per Share	The following table sets forth the outstanding potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because to do so would be anti-dilutive (in thousands): December 31, 2018 2017 2016 Warrants to purchase common stock 13 150 150 Common stock options issued and outstanding 5,385 4,826 3,394 Shares issuable upon conversion of convertible note payable — 2,965 — ESPP shares pending issuance 8 5 2 Total 5,406 7,946 3,546

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Summary of Assets Measured at Fair Value	Below is a summary of assets, including cash equivalents and marketable securities, measured at fair value as of December 31, 2018 and 2017 (in thousands): Fair Value Measurements Using December 31, 2018 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Money market funds $ 8,000 $ 8,000 $ — $ — Corporate debt securities 30,620 — 30,620 — Total $ 38,620 $ 8,000 $ 30,620 $ — Fair Value Measurements Using December 31, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Money market funds $ 12,218 $ 12,218 $ — $ — Corporate debt securities 61,774 — 61,774 — Total $ 73,992 $ 12,218 $ 61,774 $ —

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Summary of Marketable Securities	The Company invests its excess cash in money market funds and debt instruments of financial institutions, corporations, government sponsored entities and municipalities. The following tables summarize the Company’s marketable securities (in thousands): As of December 31, 2018 Maturity (in years) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Corporate debt securities 1 or less $ 29,144 $ — $ (17 ) $ 29,127 Total $ 29,144 $ — $ (17 ) $ 29,127 As of December 31, 2017 Maturity (in years) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Corporate debt securities 1 or less $ 58,851 $ — $ (77 ) $ 58,774 Total $ 58,851 $ — $ (77 ) $ 58,774

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following (in thousands): December 31, 2018 2017 Furniture and fixtures $ 334 $ 334 Equipment 208 143 Leasehold improvements 147 152 689 629 Less accumulated depreciation and amortization (535 ) (450 ) Total $ 154 $ 179

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Summary of Stock Option Activity	The following table summarizes the Company’s stock option activity under all stock option plans for the three years ended December 31, 2018 (options in thousands): Number of Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in years) Outstanding at December 31, 2015 2,465 $ 6.54 Granted 1,133 1.96 Exercised (61 ) 0.92 Forfeited/cancelled/expired (143 ) 6.65 Outstanding at December 31, 2016 3,394 5.10 Granted 1,733 4.91 Exercised (79 ) 1.32 Forfeited/cancelled/expired (222 ) 6.09 Outstanding at December 31, 2017 4,826 5.05 Granted 943 5.08 Exercised (211 ) 1.71 Forfeited/cancelled/expired (173 ) 4.83 Outstanding at December 31, 2018 5,385 $ 5.20 7.1 Exercisable at December 31, 2018 3,400 $ 5.46 6.3
Summary of Common Stock Reserved for Future Issuance	The following shares of common stock were reserved for future issuance at December 31, 2018 and 2017 (in thousands): December 31, 2018 2017 Warrants to purchase common stock 13 150 Common stock options issued and outstanding 5,385 4,826 Common stock authorized for future option grants 844 614 Common stock authorized for the ESPP 495 531 Shares issuable upon conversion of convertible note payable — 2,965 Total 6,737 9,086

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Components of Company's Deferred Tax Assets	Significant components of the Company’s deferred tax assets at December 31, 2018 and 2017 are shown below (in thousands): December 31, 2018 2017 Deferred tax assets Net operating loss carryovers $ 31,135 $ 25,202 Research and development tax credits 8,641 7,529 Intangibles 379 480 Stock options 2,255 1,840 Compensation 452 406 Deferred revenue 2,642 5,605 Other 62 62 Total gross deferred tax assets 45,566 41,124 Less valuation allowance (45,566 ) (41,124 ) Net deferred tax assets $ — $ —
Reconciliation of Statutory Tax Rates and Effective Tax Rates	A reconciliation of the statutory tax rates and the effective tax rates for the years ended December 31, 2018, 2017 and 2016 is as follows: December 31, 2018 2017 2016 Statutory rate 21.00 % 34.00 % 34.00 % State tax, net of federal benefit 0.00 % 0.00 % 0.00 % Valuation allowance (25.18 %) 51.50 % (34.26 %) Federal tax rate change 0.00 % (93.30 %) 0.00 % General business credits 6.18 % 10.80 % 0.00 % Other (2.00 %) (3.00 %) 0.26 % Effective tax rate — % — % — %
Unrecognized Tax Benefits	The following table summarizes the activity related to the Company’s unrecognized tax benefits (in thousands): 2018 2017 2016 Balance at beginning of year $ 1,932 $ 1,319 $ 981 Additions based on tax positions related to the current year 289 613 338 Balance at end of year $ 2,221 $ 1,932 $ 1,319

Collaboration and License Agr_2

Collaboration and License Agreements (Tables)	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Summary of Reconciliation of Deferred Revenue Related to Collaboration Agreement	A reconciliation of the opening and closing balances of deferred revenue related to the Collaboration Agreement, which represents the unrecognized balance of the transaction price, is as follows (in thousands): Deferred Revenue at Reporting Date Balance at December 31, 2017 $ 26,691 Cumulative effect of adoption of accounting standard 1,299 Additions to deferred revenue 18,486 Revenue recognized (33,586 ) Balance at December 31, 2018 $ 12,890
Summary of Deferred Revenue Expected to Recognize Related to Collaboration Agreement	The Company expects to recognize deferred revenue related to the Collaboration Agreement as follows (in thousands): Total Within 1 Year 1-2 Years Deferred revenue $ 12,890 $ 10,075 $ 2,815 Total $ 12,890 $ 10,075 $ 2,815
Summary of Reconciliation of Deferred Costs Related To Collaboration Agreement	A reconciliation of the opening and closing balances of deferred costs related to execution of the Collaboration Agreement is as follows (in thousands): Deferred Costs at Reporting Date Balance at December 31, 2017 $ — Cumulative effect of adoption of accounting standard 687 Costs recognized (377 ) Balance at December 31, 2018 $ 310
Summary of Deferred Costs Expected To Recognize Related to Execution of Collaboration Agreement	The Company expects to recognize deferred costs related to execution of the Collaboration Agreement as follows (in thousands): Total Within 1 Year 1-2 Years Deferred costs $ 310 $ 242 $ 68 Total $ 310 $ 242 $ 68

Commitments (Tables)

Commitments (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Future Annual Minimum Payments Under Lease and First Lease Amendment	As of December 31, 2018, future annual minimum payments under the Lease and the First Lease Amendment are as follows (in thousands): 2019 $ 437 2020 351 Total $ 788

Quarterly Financial Data (Table

Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Data	The following tables summarize the unaudited quarterly financial data for the last two fiscal years (in thousands, except per share data): 2018 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenues $ 9,737 $ 8,774 $ 7,666 $ 7,409 Total operating expenses 14,794 13,331 12,324 11,414 Total other income 39 60 69 99 Net loss (5,018 ) (4,497 ) (4,589 ) (3,906 ) Net loss per share, basic and diluted (1) (0.17 ) (0.15 ) (0.15 ) (0.13 ) 2017 First Quarter Second Quarter Third Quarter Fourth Quarter Total revenues $ 6,998 $ 10,008 $ 9,566 $ 8,805 Total operating expenses 10,689 15,412 13,614 13,212 Total other income (expense) 68 (13 ) 48 51 Net loss (3,623 ) (5,417 ) (4,000 ) (4,356 ) Net loss per share, basic and diluted (1) (0.14 ) (0.19 ) (0.13 ) (0.15 ) (1)

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Date of incorporation	Jul. 13, 2005
Accumulated deficit	$ 186,629	$ 168,007
Cash, cash equivalents and marketable securities	40,700
Working capital	$ 28,900

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018USD ($)Segment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)PerformanceObligation	Jan. 01, 2019USD ($)	Jan. 01, 2018USD ($)
Summary Of Significant Accounting Policies [Line Items]
Realized gains and losses on investments	$ 0	$ 0	$ 0
Other-than-temporary declines in value of marketable securities	0	0	$ 0
Impairment losses not recognized	0
Unrecognized tax benefits that would, if recognized, affect the Company’s effective tax rate	$ 0
Risk-free interest rate basis	The risk-free interest rate is based on the average yield of five- and seven-year U.S. Treasury Bills as of the valuation date.
Number of operating segment | Segment	1
Accumulated deficit	$ 186,629,000	$ 168,007,000
Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
ROU assets				$ 600,000
Lease liabilities				$ 700,000
ASU No. 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit					$ 600,000
Collaboration Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Unrecognized royalty revenue	0
Revenue recognized	33,586,000
Collaboration Agreement [Member] | ASU No. 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Summary Of Significant Accounting Policies [Line Items]
Revenue recognized	2,900,000
Collaboration Agreement [Member] | ASU No. 2014-09 [Member] | Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Summary Of Significant Accounting Policies [Line Items]
Revenue recognized	$ 30,700,000
Collaboration Agreement [Member] | Novartis [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of significant performance obligations | PerformanceObligation			2
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets	5 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Black-Scholes Option Pricing Model Assumptions (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate - Minimum	2.55%	1.83%	1.15%
Risk-free interest rate - Maximum	3.03%	2.13%	1.55%
Expected dividend yield	0.00%	0.00%	0.00%
Expected volatility			84.00%
Expected volatility - Minimum	94.00%	93.00%
Expected volatility - Maximum	100.00%	97.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 6 months	5 years 6 months	5 years 6 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Outstanding Potentially Dilutive Securities Excluded in Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	5,406	7,946	3,546
ESPP shares pending issuance [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	8	5	2
Warrants to purchase common stock [Member] | Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	13	150	150
Common stock options issued and outstanding [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	5,385	4,826	3,394
Shares issuable upon conversion of convertible note payable [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	0	2,965	0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	$ 38,620	$ 73,992
Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	8,000	12,218
Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	30,620	61,774
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	8,000	12,218
Level 1 [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	8,000	12,218
Level 1 [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	0	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	30,620	61,774
Level 2 [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	0	0
Level 2 [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	30,620	61,774
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	0	0
Level 3 [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	0	0
Level 3 [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	$ 0	$ 0

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 29,144	$ 58,851
Unrealized Gains	0	0
Unrealized Losses	(17)	(77)
Estimated Fair Value	29,127	58,774
Corporate debt securities 1 or less years of maturity [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	29,144	58,851
Unrealized Gains	0	0
Unrealized Losses	(17)	(77)
Estimated Fair Value	$ 29,127	$ 58,774

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 689	$ 629
Less accumulated depreciation and amortization	(535)	(450)
Total	154	179
Furniture and fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	334	334
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	208	143
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 147	$ 152

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Depreciation	$ 91,000	$ 108,000	$ 106,000

Notes Payable - Additional Info

Notes Payable - Additional Information (Detail) - USD ($)	Dec. 05, 2018	Feb. 15, 2017	Jan. 24, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 19, 2016	Jul. 31, 2010
Debt Instrument [Line Items]
Proceeds from issuance of convertible note payable					$ 0	$ 12,500,000	$ 0
Conversion of convertible note payable					$ 13,729,000	$ 0	$ 0
Novartis [Member] | Investment Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate				6.00%			6.00%
Debt instrument, maturity date				Dec. 31, 2019
Principal and accrued interest of note to be converted into common stock at conversion price, in percentage				120.00%
Deferred revenue								$ 2,500,000
Promissory note [Member] | Pfizer Inc. [Member]
Debt Instrument [Line Items]
Note payable									$ 1,000,000
Debt instrument, interest rate					7.00%
Debt instrument, maturity date					Jul. 29, 2020
Prepayment of notes payable			$ 1,004,861
Convertible Promissory Note [Member] | Novartis [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate		6.00%
Debt instrument, maturity date		Dec. 31, 2019
Promissory note, principal amount		$ 15,000,000
Promissory note conversion, description					The terms of the Novartis Note allowed the Company to convert the principal and accrued interest into the Company’s common stock at a conversion price equal to 120% of the 20-day trailing average closing price per share of the common stock immediately prior to the conversion date.
Principal and accrued interest of note to be converted into common stock at conversion price, in percentage		120.00%
Trailing period for average closing price per share of common stock		20 days
Proceeds from issuance of convertible note payable		$ 15,000,000
Convertible note payable		12,500,000
Reduction of outstanding receivable		2,500,000
Conversion of convertible note payable	$ 15,000,000
Conversion of convertible note payable to common stock	2,882,519
Conversion price	$ 5.77
Fair value of convertible note payable					$ 12,500,000
Convertible Promissory Note [Member] | Novartis [Member] | Investment Agreement [Member]
Debt Instrument [Line Items]
Promissory note, principal amount		$ 15,000,000
Conversion of convertible note payable	$ 15,000,000
Conversion of convertible note payable to common stock	2,882,519
Conversion price	$ 5.77

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Aug. 02, 2018	Aug. 31, 2017	May 31, 2017	Jul. 31, 2013	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Net proceeds from the issuance of common stock			$ 30,600,000		$ 0	$ 30,610,000	$ 13,522,000
Payment for repurchase of common stock					$ 0	$ 11,203,000	$ 0
Total remaining options available for future grant					844,000	614,000
Stock options granted to purchase common stock					943,000	1,733,000	1,133,000
Weighted-average fair value of options granted					$ 3.93	$ 3.79	$ 1.38
Total intrinsic value of stock options exercised					$ 600,000	$ 300,000	$ 100,000
Intrinsic value of options outstanding					200,000
Intrinsic value of options exercisable					200,000
Accounts payable and accrued expenses					6,216,000	11,962,000
Stock-based compensation					3,800,000	$ 4,100,000	$ 3,400,000
Unrecognized compensation expense					$ 6,200,000
Weighted-average vesting term					2 years 4 months 24 days
Employment Inducement Award [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted to purchase common stock		525,000
2006 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance to employees, nonemployee directors and consultants					1,030,303
2013 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance to employees, nonemployee directors and consultants				1,000,000
Stock option plans, maximum term of plan				10 years
Stock option plans, remaining vesting period				3 years
Percentage of outstanding shares of common stock				5.00%
Total remaining options available for future grant					844,191
2013 Plan [Member] | Tranche right [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option plans, percentage of options vested				25.00%
2013 Warrants [Member] | Convertible promissory notes [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrant expiration date								May 30, 2018
2013 Warrants [Member] | Series B Preferred Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrant exercisable to purchase shares								1,124,026
2013 Warrants [Member] | Series B Preferred Stock [Member] | Convertible promissory notes [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of warrant per share								$ 0.90
Lender Warrants [Member] | Series B convertible preferred stock [Member] | Term Loan One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of warrant per share								$ 0.90
Warrant issued								111,112
Warrant expiration date								Jul. 3, 2023
Sales Agreement with Stifel [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares sold under sales agreement					0
Sales Agreement with Stifel [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, value of shares issued	$ 35,000,000
Percentage of commission of gross sales price per share	3.00%
Sales Agreement with Stifel [Member] | Other Assets [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Legal and accounting costs incurred					$ 100,000
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares issued						5,980,000	6,156,000
Common stock issued					36,000	24,000	27,000
Common Stock [Member] | 2013 Warrants [Member] | Convertible promissory notes [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of warrant per share				$ 7.43
Common Stock [Member] | Lender Warrants [Member] | Convertible promissory notes [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of warrant per share				$ 7.43
Warrants exercisable				13,468
Common Stock [Member] | Stock Purchase Agreement with Advent [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Payment for repurchase of common stock			$ 11,200,000
Shares repurchased and retired under stock purchase agreement			2,166,836
Shares repurchased and retired price per share			$ 5.17
Follow on Offering [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares issued			5,980,000
Common stock, price per share			$ 5.50
Post IPO [Member] | Common Stock [Member] | 2013 Warrants [Member] | Convertible promissory notes [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants exercisable				136,236
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Lower fair market value of purchase price share				85.00%
Accounts payable and accrued expenses					$ 28,936	$ 16,367	$ 4,521
Employee Stock Purchase Plan [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Employee stock purchase plan, employees contribution				20.00%
Employee Stock Purchase Plan [Member] | Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock issued					36,296	24,303	26,876

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock Option Activity (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, Beginning balance	4,826	3,394	2,465
Number of Options, Granted	943	1,733	1,133
Number of Options, Exercised	(211)	(79)	(61)
Number of Options, Forfeited/cancelled/expired	(173)	(222)	(143)
Number of Options, Ending balance	5,385	4,826	3,394
Number of Options, Exercisable	3,400
Weighted-Average Exercise Price, Beginning balance	$ 5.05	$ 5.10	$ 6.54
Weighted-Average Exercise Price, Granted	5.08	4.91	1.96
Weighted-Average Exercise Price, Exercised	1.71	1.32	0.92
Weighted-Average Exercise Price, Forfeited/cancelled/expired	4.83	6.09	6.65
Weighted-Average Exercise Price, Ending balance	5.20	$ 5.05	$ 5.10
Weighted-Average Exercise Price, Vested, Exercisable	$ 5.46
Weighted-Average Remaining Contractual Term Outstanding	7 years 1 month 6 days
Weighted-Average Remaining Contractual Term Exercisable	6 years 3 months 18 days

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Detail) - shares shares in Thousands	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Warrants to purchase common stock	13	150
Common stock options issued and outstanding	5,385	4,826
Common stock authorized for future option grants	844	614
Common stock authorized for the ESPP	495	531
Shares issuable upon conversion of convertible note payable	0	2,965
Total	6,737	9,086

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 22, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Tax Cuts and Jobs Act, Incomplete Accounting, Change in Tax Rate, Provisional Income Tax Expense (Benefit)			$ 16,200,000
Cumulative change in ownership percentage	50.00%
Period for cumulative change in ownership percentage	3 years
Research credit carryforwards expiration year	2,027
Deferred tax asset, change in valuation allowance amount	$ 4,400,000	$ (9,000,000)		$ 10,200,000
Minimum percentage of likelihood for uncertain tax position to be recognized	50.00%
Recognized interest or penalties on income tax	$ 0	$ 0		$ 0
Federal and State [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	122,800,000
Research credit carryforwards	$ 8,800,000
Operating loss carryforwards expiration year	2,028
State [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 76,400,000
Research credit carryforwards	$ 2,400,000

Income Taxes - Components of Co

Income Taxes - Components of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets
Net operating loss carryovers	$ 31,135	$ 25,202
Research and development tax credits	8,641	7,529
Intangibles	379	480
Stock options	2,255	1,840
Compensation	452	406
Deferred revenue	2,642	5,605
Other	62	62
Total gross deferred tax assets	45,566	41,124
Less valuation allowance	(45,566)	(41,124)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Statutory Tax Rates and Effective Tax Rates (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	34.00%	34.00%
State tax, net of federal benefit	0.00%	0.00%	0.00%
Valuation allowance	(25.18%)	51.50%	(34.26%)
Federal tax rate change	0.00%	(93.30%)	0.00%
General business credits	6.18%	10.80%	0.00%
Other	(2.00%)	(3.00%)	0.26%
Effective tax rate	0.00%	0.00%	0.00%

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 1,932	$ 1,319	$ 981
Additions based on tax positions related to the current year	289	613	338
Balance at end of year	$ 2,221	$ 1,932	$ 1,319

Collaboration and License Agr_3

Collaboration and License Agreements - Additional Information (Detail) - USD ($)	Dec. 05, 2018	Feb. 15, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jul. 05, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Conversion of convertible note payable				$ 13,729,000	$ 0	$ 0
Novartis [Member] | Convertible Promissory Note [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Debt instrument, interest rate		6.00%
Debt instrument, maturity date		Dec. 31, 2019
Debt instrument, conversion price percentage		120.00%
Promissory note, principal amount		$ 15,000,000
Conversion of convertible note payable	$ 15,000,000
Conversion of convertible note payable to common stock	2,882,519
Conversion price	$ 5.77
Collaboration Agreement [Member] | Novartis [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-refundable payment received			$ 50,000,000
Proceeds from option exercised							$ 7,000,000
Maximum milestone payments to be received upon achievement of certain milestones			$ 650,000,000
Percentage of observational study costs			50.00%
Assumed percentage of observational study costs upon completion of ongoing Phase 2b trails			100.00%
Required prior written notice period for termination of collaboration agreement			180 days
Percentage of reduction in milestone and royalty payments			50.00%
Investment Agreement [Member] | Novartis [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Debt instrument, maximum borrowing capacity			$ 15,000,000			$ 15,000,000
Debt instrument, interest rate			6.00%			6.00%
Debt instrument, maturity date			Dec. 31, 2019
Debt instrument, conversion price percentage			120.00%
Number of days trailing average closing price of common stock immediately prior to the conversion date			20 days
Investment Agreement [Member] | Novartis [Member] | Convertible Promissory Note [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Promissory note, principal amount		$ 15,000,000
Conversion of convertible note payable	$ 15,000,000
Conversion of convertible note payable to common stock	2,882,519
Conversion price	$ 5.77

Collaboration and License Agr_4

Collaboration and License Agreements - Summary of Reconciliation of Deferred Revenue Related to Collaboration Agreement (Detail) - Collaboration Agreement [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at December 31, 2017	$ 26,691
Cumulative effect of adoption of accounting standard	1,299
Additions to deferred revenue	18,486
Revenue recognized	(33,586)
Balance at December 31, 2018	$ 12,890

Collaboration and License Agr_5

Collaboration and License Agreements - Summary of Deferred Revenue Expected to Recognize Related to Collaboration Agreement (Detail) - Collaboration Agreement [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total	$ 12,890	$ 26,691
Within 1 Year	10,075
1-2 Years	2,815
Deferred Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total	12,890
Within 1 Year	10,075
1-2 Years	$ 2,815

Collaboration and License Agr_6

Collaboration and License Agreements - Summary of Reconciliation of Deferred Costs Related To Collaboration Agreement (Detail) - Collaboration Agreement [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at December 31, 2017	$ 0
Cumulative effect of adoption of accounting standard	687
Costs recognized	(377)
Balance at December 31, 2018	$ 310

Collaboration and License Agr_7

Collaboration and License Agreements - Summary of Deferred Costs Expected To Recognize Related to Execution of Collaboration Agreement (Detail) - Collaboration Agreement [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total	$ 310	$ 0
Within 1 Year	242
1-2 Years	68
Deferred Costs [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total	310
Within 1 Year	242
1-2 Years	$ 68

Employee Benefits - Additional

Employee Benefits - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Postemployment Benefits [Abstract]
Defined contribution plan, Employees voluntary contributions, Amount	$ 239,000	$ 217,000	$ 172,000
Eligibility criteria for employees to participate in the plan	Employees are eligible to participate in the plan beginning on the first day of employment.

Commitments - Additional Inform

Commitments - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	May 31, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jul. 31, 2010
Operating Leased Assets [Line Items]
Rent expense		$ 400,000	$ 400,000	$ 400,000
Amount payable upon the achievement of specified regulatory milestone					$ 18,000,000
Operating lease term July 2014 through December 2019 [Member]
Operating Leased Assets [Line Items]
Lease renewal term		5 years
Operating lease term September 2015 through September 2020 [Member]
Operating Leased Assets [Line Items]
Percentage of base rent escalator	3.00%
Rent expense	$ 33,000
Lease agreement rent expense for future period	$ 39,000

Commitments - Future Annual Min

Commitments - Future Annual Minimum Payments Under Lease and First Lease Amendment (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,019	$ 437
2,020	351
Total	$ 788

Quarterly Financial Data - Summ

Quarterly Financial Data - Summary of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 7,409		$ 7,666		$ 8,774		$ 9,737		$ 8,805		$ 9,566		$ 10,008		$ 6,998		$ 33,586	$ 35,377	$ 799
Total operating expenses	11,414		12,324		13,331		14,794		13,212		13,614		15,412		10,689		51,863	52,927	30,631
Total other income (expense)	99		69		60		39		51		48		(13)		68		267	154	98
Net loss	$ (3,906)		$ (4,589)		$ (4,497)		$ (5,018)		$ (4,356)		$ (4,000)		$ (5,417)		$ (3,623)		$ (18,010)	$ (17,396)	$ (29,734)
Net loss per share, basic and diluted	$ (0.13)	[1]	$ (0.15)	[1]	$ (0.15)	[1]	$ (0.17)	[1]	$ (0.15)	[1]	$ (0.13)	[1]	$ (0.19)	[1]	$ (0.14)	[1]	$ (0.59)	$ (0.61)	$ (1.31)
[1]	Net loss per share is computed independently for each quarter and the full year based upon respective shares outstanding; therefore, the sum of the quarterly net loss per share amounts may not equal the annual amounts reported.