Histogen (HSTO) 10-Q 7 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 22, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	CNAT
Entity Registrant Name	Conatus Pharmaceuticals Inc.
Entity Central Index Key	0001383701
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Address, Address Line One	16745 W. Bernardo Dr.
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92127
City Area Code	(858)
Local Phone Number	376-2600
Entity File Number	001-36003
Entity Tax Identification Number	203183915
Entity Common Stock, Shares Outstanding		33,170,487

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 13,437	$ 11,565
Marketable securities	15,312	29,127
Collaboration receivables	3,194	3,677
Prepaid and other current assets	3,468	3,057
Total current assets	35,411	47,426
Property and equipment, net	124	154
Other assets	631	1,223
Total assets	36,166	48,803
Current liabilities:
Accounts payable and accrued expenses	8,609	6,216
Accrued compensation	783	2,230
Current portion of deferred revenue	2,130	10,075
Current portion of lease liabilities	419	0
Total current liabilities	11,941	18,521
Deferred revenue, less current portion	0	2,815
Lease liabilities, less current portion	116	0
Deferred rent, less current portion	0	68
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; 33,170 shares issued and outstanding at June 30, 2019; 33,165 shares issued and outstanding at December 31, 2018	3	3
Additional paid-in capital	216,133	214,042
Accumulated other comprehensive income (loss)	5	(17)
Accumulated deficit	(192,032)	(186,629)
Total stockholders’ equity	24,109	27,399
Total liabilities and stockholders’ equity	$ 36,166	$ 48,803

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
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	33,170,000	33,165,000
Common stock, shares outstanding	33,170,000	33,165,000

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues:
Collaboration revenue	$ 10,791	$ 8,774	$ 17,815	$ 18,511
Total revenues	10,791	8,774	17,815	18,511
Operating expenses:
Research and development	8,565	10,737	17,948	22,818
General and administrative	3,054	2,594	5,645	5,307
Total operating expenses	11,619	13,331	23,593	28,125
Loss from operations	(828)	(4,557)	(5,778)	(9,614)
Other income (expense):
Interest income	172	244	372	477
Interest expense	0	(187)	0	(372)
Other income (expense)	0	3	3	(6)
Total other income	172	60	375	99
Net loss	(656)	(4,497)	(5,403)	(9,515)
Other comprehensive income (loss):
Net unrealized gains on marketable securities	2	71	22	36
Comprehensive loss	$ (654)	$ (4,426)	$ (5,381)	$ (9,479)
Net loss per share, basic and diluted	$ (0.02)	$ (0.15)	$ (0.16)	$ (0.32)
Weighted average shares outstanding used in computing net loss per share, basic and diluted	33,168	30,114	33,167	30,081

Condensed Statements of Stockho

Condensed Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2017	$ 27,996	$ 3	$ 196,077	$ (77)	$ (168,007)
Beginning balance, shares at Dec. 31, 2017		30,035
Issuance of common stock upon exercise of stock options	37	$ 0	37	0	0
Issuance of common stock upon exercise of stock options, shares		28
Share-based compensation	983	$ 0	983	0	0
Cumulative effect of adoption of accounting standard	(612)	0	0	0	(612)
Net loss	(5,018)	0	0	0	(5,018)
Unrealized gain (loss) on marketable securities	(35)	0	0	(35)	0
Ending balance at Mar. 31, 2018	23,351	$ 3	197,097	(112)	(173,637)
Ending balance, shares at Mar. 31, 2018		30,063
Beginning balance at Dec. 31, 2017	27,996	$ 3	196,077	(77)	(168,007)
Beginning balance, shares at Dec. 31, 2017		30,035
Net loss	(9,515)
Unrealized gain (loss) on marketable securities	36
Ending balance at Jun. 30, 2018	19,971	$ 3	198,143	(41)	(178,134)
Ending balance, shares at Jun. 30, 2018		30,145
Beginning balance at Mar. 31, 2018	23,351	$ 3	197,097	(112)	(173,637)
Beginning balance, shares at Mar. 31, 2018		30,063
Issuance of common stock upon exercise of stock options	66	$ 0	66	0	0
Issuance of common stock upon exercise of stock options, shares		66
Issuance of common stock for employee stock purchase plan	51	$ 0	51	0	0
Issuance of common stock for employee stock purchase plan, shares		16
Share-based compensation	929	$ 0	929	0	0
Net loss	(4,497)	0	0	0	(4,497)
Unrealized gain (loss) on marketable securities	71	0	0	71	0
Ending balance at Jun. 30, 2018	19,971	$ 3	198,143	(41)	(178,134)
Ending balance, shares at Jun. 30, 2018		30,145
Beginning balance at Dec. 31, 2018	27,399	$ 3	214,042	(17)	(186,629)
Beginning balance, shares at Dec. 31, 2018		33,165
Share-based compensation	926	$ 0	926	0	0
Net loss	(4,747)	0	0	0	(4,747)
Unrealized gain (loss) on marketable securities	20	0	0	20	0
Ending balance at Mar. 31, 2019	23,598	$ 3	214,968	3	(191,376)
Ending balance, shares at Mar. 31, 2019		33,165
Beginning balance at Dec. 31, 2018	$ 27,399	$ 3	214,042	(17)	(186,629)
Beginning balance, shares at Dec. 31, 2018		33,165
Issuance of common stock upon exercise of stock options, shares	0
Net loss	$ (5,403)
Unrealized gain (loss) on marketable securities	22
Ending balance at Jun. 30, 2019	24,109	$ 3	216,133	5	(192,032)
Ending balance, shares at Jun. 30, 2019		33,170
Beginning balance at Mar. 31, 2019	23,598	$ 3	214,968	3	(191,376)
Beginning balance, shares at Mar. 31, 2019		33,165
Issuance of common stock for employee stock purchase plan	4	$ 0	4	0	0
Issuance of common stock for employee stock purchase plan, shares		5
Share-based compensation	1,161	$ 0	1,161	0	0
Net loss	(656)	0	0	0	(656)
Unrealized gain (loss) on marketable securities	2	0	0	2	0
Ending balance at Jun. 30, 2019	$ 24,109	$ 3	$ 216,133	$ 5	$ (192,032)
Ending balance, shares at Jun. 30, 2019		33,170

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net loss	$ (5,403)	$ (9,515)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	41	54
Stock-based compensation expense	2,087	1,912
Amortization of premiums and discounts on marketable securities, net	(162)	(127)
Accrued interest included in convertible note payable	0	372
Changes in operating assets and liabilities:
Collaboration receivables	483	(1,486)
Prepaid and other current assets	616	277
Accounts payable and accrued expenses	2,452	(334)
Accrued compensation	(1,447)	(523)
Deferred revenue	(10,760)	(7,811)
Lease liabilities, net	(27)	0
Deferred rent	0	(20)
Other assets	0	(246)
Net cash used in operating activities	(12,120)	(17,447)
Investing activities
Maturities of marketable securities	28,500	36,925
Purchase of marketable securities	(14,501)	(24,067)
Capital expenditures	(11)	(5)
Net cash provided by investing activities	13,988	12,853
Financing activities
Proceeds from stock issuances related to exercise of stock options and employee stock purchase plan	4	154
Net cash provided by financing activities	4	154
Net increase (decrease) in cash and cash equivalents	1,872	(4,440)
Cash and cash equivalents at beginning of period	11,565	16,079
Cash and cash equivalents at end of period	$ 13,437	$ 11,639

Organization and Basis of Prese

Organization and Basis of Presentation	6 Months Ended
	Jun. 30, 2019
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 that has been focused on the development and commercialization of novel medicines to treat chronic diseases with significant unmet need. The Company has been developing emricasan, a first-in-class, orally active pan-caspase inhibitor, for the treatment of patients with chronic liver disease. In December 2016, the Company entered into an Option, Collaboration and License Agreement (the Collaboration Agreement) with Novartis Pharma AG (Novartis) for the development and commercialization of emricasan. As of June 30, 2019, the Company has devoted substantially all of its efforts to product development and has not realized product sales revenues from its planned principal operations. In June 2019, the Company announced that top-line results from its ENCORE-LF clinical trial of emricasan did not meet the primary endpoint, and the Company is discontinuing further treatment of patients enrolled in the ENCORE-LF clinical trial. In addition, results from the 24-week extension in the Company’s ENCORE-PH clinical trial of emricasan were consistent with results from the initial 24-week treatment period and did not meet predefined objectives. In March 2019, the Company announced that top-line results from the ENCORE-NF clinical trial of emricasan also did not meet the primary endpoint. Consequently, the Company and Novartis have no further development plans for emricasan, and the Company plans to complete closeout activities for the clinical trials of emricasan for which it is responsible under the Collaboration Agreement. In connection with the recent emricasan clinical trial results, the Company commenced a restructuring plan in June 2019 that included reducing staff and suspending development of its inflammasome disease candidate, CTS-2090, in order to extend its resources. The Company has engaged a financial advisor to assist in the exploration and evaluation of strategic alternatives to enhance shareholder value, including a merger, an acquisition or sale of assets or a dissolution and liquidation of the Company. There can be no assurance any transaction will result from the Company’s evaluation of strategic alternatives. As part of this process, the Company plans to evaluate future opportunities, if any, for emricasan and the Company’s inflammasome program. 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 June 30, 2019, had an accumulated deficit of $192.0 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 or seek to complete one of the strategic alternatives described above. The accompanying unaudited interim condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and the rules and regulations of the Securities and Exchange Commission (SEC) related to a quarterly report on Form 10-Q. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations. The unaudited interim condensed financial statements reflect all adjustments which, in the opinion of management, are necessary for a fair statement of the results for the periods presented. All such adjustments are of a normal and recurring nature. The operating results presented in these unaudited interim condensed financial statements are not necessarily indicative of the results that may be expected for any future periods. These unaudited interim condensed financial statements should be read in conjunction with the audited financial statements and the notes thereto for the year ended December 31, 2018 included in the Company’s annual report on Form 10-K filed with the SEC on March 8, 2019.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of condensed financial statements in conformity with 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 condensed balance sheets, with unrealized gains and losses, if any, reported as a component of other comprehensive income (loss) within the condensed 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 six-month periods ended June 30, 2019 and 2018. 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, 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. 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. 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 estimation of stock option and ESPP fair value requires management to make estimates and judgments about, among other things, employee exercise behavior, forfeiture rates and volatility of the Company’s common stock. The judgments directly affect the amount of compensation expense that will be recognized. 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 June 30, 2019. 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 the Collaboration Agreement and an Investment Agreement (the Investment Agreement) with 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. The Company does not expect Novartis to continue development and commercialization of emricasan and does not expect to receive any future milestone, royalty or profit and loss sharing payments under the Collaboration Agreement. See Note 8 – 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 condensed balance sheet that would, if recognized, affect the Company’s effective tax rate, and the Company has noted no material changes through June 30, 2019. The Company has not recognized interest and penalties in the condensed balance sheets or condensed 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. Comprehensive Loss The Company is required to report all components of comprehensive loss, including net loss, in the condensed 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 condensed 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): June 30, 2019 2018 Warrants to purchase common stock 13 13 Common stock options issued and outstanding 6,411 5,528 Shares issuable upon conversion of convertible note payable — 2,846 ESPP shares pending issuance — 6 Total 6,424 8,393 Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842). This guidance requires lessees to recognize leases on the balance sheet and disclose key information about leasing arrangements. ASU 2016-02 establishes a right-of-use model (ROU) that requires a lessee to recognize an ROU asset and lease liability on the balance sheet for all leases with a term longer than 12 months. The Company adopted this standard effective January 1, 2019, as required, retrospectively through a cumulative effect adjustment. The new standard provides a number of optional practical expedients in transition. The Company elected the “package of practical expedients,” which permits the Company not to reassess, under ASU 2016-02, prior conclusions about lease identification, lease classification and initial direct costs. The new standard also provides practical expedients for an entity’s ongoing accounting. The Company elected to utilize the short-term lease recognition exemption for all leases that qualify. This means, for those short-term leases that qualify, the Company will not recognize ROU assets or lease liabilities. The Company also elected not to separate lease and non-lease components for facility leases. Adoption of this guidance resulted in the recognition of lease liabilities of $0.7 million, based on the present value of the remaining minimum rental payments under current leasing standards for the Company’s applicable existing office space operating lease, with corresponding ROU assets of $0.6 million. See Note 9 – Commitments for further information.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
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, cash equivalents and marketable securities, measured at fair value as of June 30, 2019 and December 31, 2018 (in thousands): Fair Value Measurements Using June 30, 2019 Quoted Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Cash $ 2,452 $ 2,452 $ — $ — Money market funds 6,997 6,997 — — Corporate debt securities 19,300 — 19,300 — Total $ 28,749 $ 9,449 $ 19,300 $ — Fair Value Measurements Using December 31, 2018 Quoted Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Cash $ 2,072 $ 2,072 $ — $ — Money market funds 8,000 8,000 — — Corporate debt securities 30,620 — 30,620 — Total $ 40,692 $ 10,072 $ 30,620 $ — 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	6 Months Ended
	Jun. 30, 2019
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 June 30, 2019 Maturity (in years) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Corporate debt securities 1 or less $ 15,307 $ 5 $ — $ 15,312 Total $ 15,307 $ 5 $ — $ 15,312 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

Property and Equipment

Property and Equipment	6 Months Ended
	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Property and Equipment	5. Property and Equipment Property and equipment consist of the following (in thousands): June 30, December 31, 2019 2018 Furniture and fixtures $ 334 $ 334 Equipment 215 208 Leasehold improvements 147 147 696 689 Less accumulated depreciation and amortization (572 ) (535 ) Total $ 124 $ 154

Note Payable

Note Payable	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Note Payable	6. Note Payable 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	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Stockholders' Equity	7. Stockholders’ Equity Common Stock 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 The Nasdaq Global Market (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 June 30, 2019, 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 June 30, 2019, no shares were issued pursuant to the Sales Agreement. Warrants In 2013, the Company issued 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, the Lender Warrants became exercisable for 13,468 shares of common stock at an exercise price of $7.43 per share. The Lender Warrants will expire on July 3, 2023. Stock Options The following table summarizes the Company’s stock option activity under all stock option plans for the six months ended June 30, 2019 (options in thousands): Total Options Weighted- Average Exercise Price Balance at December 31, 2018 5,385 $ 5.20 Granted 1,694 1.87 Exercised — — Forfeited/cancelled/expired (668 ) 4.04 Balance at June 30, 2019 6,411 $ 4.44 Stock-Based Compensation The Company recorded stock-based compensation of $1.2 million and $0.9 million for the three months ended June 30, 2019 and 2018, respectively, and $2.1 million and $1.9 million for the six months ended June 30, 2019 and 2018, respectively. Common Stock Reserved for Future Issuance The following shares of common stock were reserved for future issuance at June 30, 2019 (in thousands): Warrants to purchase common stock 13 Common stock options issued and outstanding 6,411 Common stock authorized for future option grants 818 Common stock authorized for the ESPP 490 Total 7,732

Collaboration and License Agree

Collaboration and License Agreements	6 Months Ended
	Jun. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreements	8. 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. 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. The Company and Novartis have no further development plans for emricasan. Therefore, the Company does not expect to receive any future milestone, royalty or profit and loss sharing payments under the Collaboration Agreement. 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. In connection with emricasan failing to meet the primary endpoints in the ENCORE clinical trials, the Company is discontinuing its ongoing emricasan clinical trials, resulting in a shortened timeline and reduced estimated costs related to completion of emricasan activities. During the three months ended June 30, 2019, the Company significantly reduced the total estimated collaboration expenses related to the Collaboration Agreement, which is used as the measure of progress for recognition of revenue related to the Collaboration Agreement, from the prior estimate as of March 31, 2019. Consequently, during the three months ended June 30, 2019, the Company significantly reduced the transaction price related to the Collaboration Agreement from the prior estimate as of March 31, 2019, to reflect lower estimated reimbursable research and development costs. The net effect of these changes was a cumulative catch-up in revenue of $4.6 million, which was recorded as revenue as a change in estimate during the three months ended June 30, 2019. Execution costs related to the Collaboration Agreement were similarly affected, resulting in a cumulative catch-up in operating expenses of $0.1 million. 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 Balance at December 31, 2018 $ 12,890 Additions to deferred revenue 7,055 Revenue recognized (17,815 ) Balance at June 30, 2019 $ 2,130 The Company expects to recognize deferred revenue related to the Collaboration Agreement within one year. 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 Balance at December 31, 2018 $ 310 Costs recognized (259 ) Balance at June 30, 2019 $ 51 The Company expects to recognize deferred costs related to execution of the Collaboration Agreement within one year.

Commitments

Commitments	6 Months Ended
	Jun. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments	9. Commitments Leases The Company determines if an arrangement is a finance lease, operating lease or short-term lease at inception, or as applicable, and accounts for the arrangement under the relevant accounting literature. Currently, the Company is only party to a non-cancelable office space operating lease and short-term lease arrangements. Under the relevant guidance, the Company recognizes operating lease ROU assets and liabilities based on the present value of the future minimum lease payments over the lease term at the commencement date, using the Company’s assumed incremental borrowing rate of 12%, and amortizes the ROU assets and liabilities over the lease term. Lease expense for operating leases is recognized on a straight-line basis over the lease term. The Company’s short-term leases are not subject to recognition of an ROU asset or liability or straight-line lease expense requirements. 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 June 30, 2019, the Company’s ROU assets and liabilities related to the Lease and the First Lease Amendment are as follows (in thousands): ROU assets (included in other assets) $ 436 Current portion of lease liabilities $ 419 Lease liabilities, less current portion 116 Total lease liabilities $ 535 The following table reconciles the undiscounted cash flows for the periods presented below to the operating lease liabilities recorded in the condensed balance sheet as of June 30, 2019 (in thousands): Remaining in 2019 $ 221 2020 351 Total lease payments 572 Present value adjustment (37 ) Total lease liabilities $ 535 Rent expense was as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Operating lease $ 94 $ 94 $ 189 $ 189 Short-term leases 19 4 36 4 Total $ 113 $ 98 $ 225 $ 193 Other Commitments In July 2010, the Company entered into a stock purchase agreement with Pfizer Inc. (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.

Restructuring Costs

Restructuring Costs	6 Months Ended
	Jun. 30, 2019
Restructuring And Related Activities [Abstract]
Restructuring Costs	10. Restructuring Costs In June 2019, the Company announced a restructuring plan that included reducing staff and suspending development of its inflammasome disease candidate, CTS-2090, in order to extend the Company’s resources. As a result, during the three months ended June 30, 2019, the Company recognized one-time employee severance expenses of $1.2 million, which are included in accounts payable and accrued expenses on the balance sheet, and noncash stock compensation expenses related to accelerated vesting of certain employee stock options of $0.3 million, both of which were recorded as operating expenses on the statement of operations and comprehensive loss. As of June 30, 2019, no payments have been made related to the accrued employee severance expenses of $1.2 million.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2019
Subsequent Events [Abstract]
Subsequent Events	11. Subsequent Events In August 2019, the Company effected a one-time option exchange, wherein certain employees were offered the opportunity to exchange eligible outstanding stock options with exercise prices that are significantly higher than the current fair market value of the Company’s common stock for the grant of a lesser number of restricted stock units (RSU). The participants received one new RSU for every two stock options tendered for exchange. As a result, 3,200,375 stock options were exchanged for 1,600,186 RSUs. The RSUs have a one-year vesting schedule or vest upon a Change of Control, an employee’s termination without Cause, or resignation for Good Reason as defined in the 2013 Incentive Award Plan. The one-time option exchange will result in additional stock compensation expense that is expected to be recorded over the one-year service term commencing August 1, 2019.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of condensed financial statements in conformity with 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 condensed balance sheets, with unrealized gains and losses, if any, reported as a component of other comprehensive income (loss) within the condensed 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 six-month periods ended June 30, 2019 and 2018. 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, 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.
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. 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 estimation of stock option and ESPP fair value requires management to make estimates and judgments about, among other things, employee exercise behavior, forfeiture rates and volatility of the Company’s common stock. The judgments directly affect the amount of compensation expense that will be recognized.
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 June 30, 2019.
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 the Collaboration Agreement and an Investment Agreement (the Investment Agreement) with 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. The Company does not expect Novartis to continue development and commercialization of emricasan and does not expect to receive any future milestone, royalty or profit and loss sharing payments under the Collaboration Agreement. See Note 8 – 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 condensed balance sheet that would, if recognized, affect the Company’s effective tax rate, and the Company has noted no material changes through June 30, 2019. The Company has not recognized interest and penalties in the condensed balance sheets or condensed 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.
Comprehensive Loss	Comprehensive Loss The Company is required to report all components of comprehensive loss, including net loss, in the condensed 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 condensed 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): June 30, 2019 2018 Warrants to purchase common stock 13 13 Common stock options issued and outstanding 6,411 5,528 Shares issuable upon conversion of convertible note payable — 2,846 ESPP shares pending issuance — 6 Total 6,424 8,393
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842). This guidance requires lessees to recognize leases on the balance sheet and disclose key information about leasing arrangements. ASU 2016-02 establishes a right-of-use model (ROU) that requires a lessee to recognize an ROU asset and lease liability on the balance sheet for all leases with a term longer than 12 months. The Company adopted this standard effective January 1, 2019, as required, retrospectively through a cumulative effect adjustment. The new standard provides a number of optional practical expedients in transition. The Company elected the “package of practical expedients,” which permits the Company not to reassess, under ASU 2016-02, prior conclusions about lease identification, lease classification and initial direct costs. The new standard also provides practical expedients for an entity’s ongoing accounting. The Company elected to utilize the short-term lease recognition exemption for all leases that qualify. This means, for those short-term leases that qualify, the Company will not recognize ROU assets or lease liabilities. The Company also elected not to separate lease and non-lease components for facility leases. Adoption of this guidance resulted in the recognition of lease liabilities of $0.7 million, based on the present value of the remaining minimum rental payments under current leasing standards for the Company’s applicable existing office space operating lease, with corresponding ROU assets of $0.6 million. See Note 9 – Commitments for further information.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
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): June 30, 2019 2018 Warrants to purchase common stock 13 13 Common stock options issued and outstanding 6,411 5,528 Shares issuable upon conversion of convertible note payable — 2,846 ESPP shares pending issuance — 6 Total 6,424 8,393

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Summary of Assets Measured at Fair Value	Below is a summary of assets, including cash, cash equivalents and marketable securities, measured at fair value as of June 30, 2019 and December 31, 2018 (in thousands): Fair Value Measurements Using June 30, 2019 Quoted Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Cash $ 2,452 $ 2,452 $ — $ — Money market funds 6,997 6,997 — — Corporate debt securities 19,300 — 19,300 — Total $ 28,749 $ 9,449 $ 19,300 $ — Fair Value Measurements Using December 31, 2018 Quoted Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets Cash $ 2,072 $ 2,072 $ — $ — Money market funds 8,000 8,000 — — Corporate debt securities 30,620 — 30,620 — Total $ 40,692 $ 10,072 $ 30,620 $ —

Marketable Securities (Tables)

Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2019
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 June 30, 2019 Maturity (in years) Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Corporate debt securities 1 or less $ 15,307 $ 5 $ — $ 15,312 Total $ 15,307 $ 5 $ — $ 15,312 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

Property and Equipment (Tables)

Property and Equipment (Tables)	6 Months Ended
	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following (in thousands): June 30, December 31, 2019 2018 Furniture and fixtures $ 334 $ 334 Equipment 215 208 Leasehold improvements 147 147 696 689 Less accumulated depreciation and amortization (572 ) (535 ) Total $ 124 $ 154

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Summary of Stock Option Activity	The following table summarizes the Company’s stock option activity under all stock option plans for the six months ended June 30, 2019 (options in thousands): Total Options Weighted- Average Exercise Price Balance at December 31, 2018 5,385 $ 5.20 Granted 1,694 1.87 Exercised — — Forfeited/cancelled/expired (668 ) 4.04 Balance at June 30, 2019 6,411 $ 4.44
Summary of Common Stock Reserved for Future Issuance	The following shares of common stock were reserved for future issuance at June 30, 2019 (in thousands): Warrants to purchase common stock 13 Common stock options issued and outstanding 6,411 Common stock authorized for future option grants 818 Common stock authorized for the ESPP 490 Total 7,732

Collaboration and License Agr_2

Collaboration and License Agreements (Tables)	6 Months Ended
	Jun. 30, 2019
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 Balance at December 31, 2018 $ 12,890 Additions to deferred revenue 7,055 Revenue recognized (17,815 ) Balance at June 30, 2019 $ 2,130
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 Balance at December 31, 2018 $ 310 Costs recognized (259 ) Balance at June 30, 2019 $ 51

Commitments (Tables)

Commitments (Tables)	6 Months Ended
	Jun. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Schedule of ROU Assets and Liabilities Related to Lease and First Lease Amendment	As of June 30, 2019, the Company’s ROU assets and liabilities related to the Lease and the First Lease Amendment are as follows (in thousands): ROU assets (included in other assets) $ 436 Current portion of lease liabilities $ 419 Lease liabilities, less current portion 116 Total lease liabilities $ 535
Schedule of Undiscounted Cash Flows for Operating Lease Liabilities Recorded in Balance Sheet	The following table reconciles the undiscounted cash flows for the periods presented below to the operating lease liabilities recorded in the condensed balance sheet as of June 30, 2019 (in thousands): Remaining in 2019 $ 221 2020 351 Total lease payments 572 Present value adjustment (37 ) Total lease liabilities $ 535
Schedule of Rent Expense	Rent expense was as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Operating lease $ 94 $ 94 $ 189 $ 189 Short-term leases 19 4 36 4 Total $ 113 $ 98 $ 225 $ 193

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Date of incorporation	Jul. 13, 2005
Accumulated deficit	$ 192,032	$ 186,629

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2019USD ($)Segment	Jun. 30, 2018USD ($)	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2016PerformanceObligation
Summary Of Significant Accounting Policies [Line Items]
Realized gains and losses on investments	$ 0	$ 0
Other-than-temporary declines in value of marketable securities	0
Impairment losses not recognized	$ 0
Unrecognized tax benefits that would, if recognized, affect the Company’s effective tax rate				$ 0
Number of operating segment | Segment	1
ROU assets	$ 436,000		$ 600,000
Lease liabilities	535,000		$ 700,000
Collaboration Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Unrecognized royalty revenue	$ 0
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 - Summary of Outstanding Potentially Dilutive Securities Excluded in Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	6,424	8,393
ESPP shares pending issuance [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	0	6
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	13
Common stock options issued and outstanding [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	6,411	5,528
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	2,846

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets Measured at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	$ 28,749	$ 40,692
Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	2,452	2,072
Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	6,997	8,000
Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	19,300	30,620
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	9,449	10,072
Level 1 [Member] | Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	2,452	2,072
Level 1 [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	6,997	8,000
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	19,300	30,620
Level 2 [Member] | Cash [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	0	0
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	19,300	30,620
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value	0	0
Level 3 [Member] | Cash [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	Jun. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 15,307	$ 29,144
Unrealized Gains	5	0
Unrealized Losses	0	(17)
Estimated Fair Value	15,312	29,127
Corporate debt securities 1 or less years of maturity [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,307	29,144
Unrealized Gains	5	0
Unrealized Losses	0	(17)
Estimated Fair Value	$ 15,312	$ 29,127

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 696	$ 689
Less accumulated depreciation and amortization	(572)	(535)
Total	124	154
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	215	208
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 147	$ 147

Note Payable - Additional Infor

Note Payable - Additional Information (Detail) - Novartis [Member] - USD ($)	Dec. 05, 2018	Feb. 15, 2017	Dec. 31, 2016	Jun. 30, 2019	Dec. 19, 2016
Investment Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate			6.00%
Debt instrument, maturity date			Dec. 31, 2019
Deferred revenue					$ 2,500,000
Convertible Promissory Note [Member]
Debt Instrument [Line Items]
Promissory note, principal amount		$ 15,000,000
Debt instrument, interest rate		6.00%
Debt instrument, maturity date		Dec. 31, 2019
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] | Investment Agreement [Member]
Debt Instrument [Line Items]
Promissory note, principal amount		$ 15,000,000
Principal and accrued interest of note to be converted into common stock at conversion price, in percentage		120.00%
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	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2013	Jul. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation		$ 1,200,000	$ 900,000	$ 2,100,000	$ 1,900,000
Lender Warrants [Member] | Series B convertible preferred stock [Member] | Term Loan One [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrant issued						111,112
Exercise price of warrant per share						$ 0.90
Warrant expiration date						Jul. 3, 2023
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
Sales Agreement with Stifel [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares sold under sales agreement		0		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		$ 100,000

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock Option Activity (Detail) shares in Thousands	6 Months Ended
	Jun. 30, 2019$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Total Options, Beginning balance | shares	5,385
Total Options, Granted | shares	1,694
Total Options, Exercised | shares	0
Total Options, Forfeited/cancelled/expired | shares	(668)
Total Options, Ending balance | shares	6,411
Weighted-Average Exercise Price, Beginning balance | $ / shares	$ 5.20
Weighted-Average Exercise Price, Granted | $ / shares	1.87
Weighted-Average Exercise Price, Exercised | $ / shares	0
Weighted-Average Exercise Price, Forfeited/cancelled/expired | $ / shares	4.04
Weighted-Average Exercise Price, Ending balance | $ / shares	$ 4.44

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Detail) shares in Thousands	Jun. 30, 2019shares
Equity [Abstract]
Warrants to purchase common stock	13
Common stock options issued and outstanding	6,411
Common stock authorized for future option grants	818
Common stock authorized for the ESPP	490
Total	7,732

Collaboration and License Agr_3

Collaboration and License Agreements - Additional Information (Detail) - USD ($)	Dec. 05, 2018	Feb. 15, 2017	Dec. 31, 2016	Jun. 30, 2019	Jun. 30, 2019	Jul. 05, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cumulative catch-up adjustment in revenue				$ 4,600,000
Cumulative catch-up adjustment in operating expenses				$ 100,000
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]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue recognize period					1 year
Deferred cost recognize period					1 year
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
Debt instrument, interest rate			6.00%
Debt instrument, maturity date			Dec. 31, 2019
Investment Agreement [Member] | Novartis [Member] | Convertible Promissory Note [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
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
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	6 Months Ended
	Jun. 30, 2019USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at December 31, 2018	$ 12,890
Additions to deferred revenue	7,055
Revenue recognized	(17,815)
Balance at June 30, 2019	$ 2,130

Collaboration and License Agr_5

Collaboration and License Agreements - Summary of Reconciliation of Deferred Costs Related To Collaboration Agreement (Detail) - Collaboration Agreement [Member] $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Balance at December 31, 2018	$ 310
Costs recognized	(259)
Balance at June 30, 2019	$ 51

Commitments - Additional Inform

Commitments - Additional Information (Detail) - USD ($)	1 Months Ended
	May 31, 2015	Jun. 30, 2019	Jul. 31, 2010
Operating Leased Assets [Line Items]
Incremental borrowing rate		12.00%
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 - Schedule of ROU A

Commitments - Schedule of ROU Assets and Liabilities Related to Lease and First Lease Amendment (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
ROU assets	$ 436	$ 600
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent
Current portion of lease liabilities	$ 419		$ 0
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OperatingLeaseLiabilityCurrent
Lease liabilities, less current portion	$ 116		$ 0
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OperatingLeaseLiabilityNoncurrent
Total lease liabilities	$ 535	$ 700

Commitments - Schedule of Undis

Commitments - Schedule of Undiscounted Cash Flows for Operating Lease Liabilities Recorded in Condensed Balance Sheet (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
Commitments And Contingencies Disclosure [Abstract]
Remaining in 2019	$ 221
2020	351
Total lease payments	572
Present value adjustment	(37)
Lease liabilities	$ 535	$ 700

Commitments - Schedule of Rent

Commitments - Schedule of Rent Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Operating lease	$ 94	$ 94	$ 189	$ 189
Short-term leases	19	4	36	4
Total	$ 113	$ 98	$ 225	$ 193

Restructuring Costs - Additiona

Restructuring Costs - Additional Information (Detail)	3 Months Ended
	Jun. 30, 2019USD ($)
Employee Severance [Member]
Restructuring Cost And Reserve [Line Items]
Payments for restructuring	$ 0
Employee Severance [Member] | Operating Expense [Member] | Accounts Payable and Accrued Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Severance expenses	1,200,000
Stock Compensation Expense [Member] | Operating Expense [Member]
Restructuring Cost And Reserve [Line Items]
Non-cash settlements	$ 300,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - One-Time Option Exchange [Member] - shares	Aug. 07, 2019	Jun. 30, 2019
Subsequent Event [Line Items]
Stock options exchange description		The participants received one new RSU for every two stock options tendered for exchange.
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of stock options exchanged	3,200,375
Additional stock compensation expense expected service term	1 year
Subsequent Event [Member] | Restricted Stock Units (RSUs) [Member]
Subsequent Event [Line Items]
Number of shares granted	1,600,186
Shares granted, vesting period	1 year