Cymabay Therapeutics (CBAY) 10-K 28 Feb 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Jan. 31, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	CBAY
Entity Registrant Name	CYMABAY THERAPEUTICS, INC.
Entity Central Index Key	1,042,074
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		59,470,368
Entity Public Float			$ 782,202,455

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 48,995	$ 23,054
Marketable securities	129,669	74,156
Receivable from collaboration		5,000
Prepaid expenses	2,594	1,208
Other current assets	304	126
Total current assets	181,562	103,544
Property and equipment, net	2,905	69
Other assets	2,280	634
Total assets	186,747	104,247
Current liabilities:
Accounts payable	1,973	1,311
Accrued clinical expenses	8,588	2,929
Other accrued liabilities	3,854	2,828
Warrant liability		6,091
Facility loan		3,108
Accrued interest payable		43
Total current liabilities	14,415	16,310
Deferred rent, less current portion	1,914
Facility loan, less current portion		2,990
Total liabilities	16,329	19,300
Stockholders’ equity:
Preferred stock, $0.0001 par value: 10,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.0001 par value: 100,000,000 shares authorized; 59,456,493 and 44,408,796 shares issued and outstanding as of December 31, 2018 and 2017, respectively	6	4
Additional paid-in capital	693,534	535,503
Accumulated other comprehensive loss	(58)	(44)
Accumulated deficit	(523,064)	(450,516)
Total stockholders’ equity	170,418	84,947
Total liabilities and stockholders’ equity	$ 186,747	$ 104,247

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	59,456,493	44,408,796
Common stock, shares outstanding	59,456,493	44,408,796

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Collaboration revenue		$ 10,000
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Operating expenses:
Research and development	$ 58,124	$ 18,938	$ 15,941
General and administrative	14,381	12,387	9,645
Total operating expenses	72,505	31,325	25,586
Loss from operations	(72,505)	(21,325)	(25,586)
Other income (expense):
Interest income	3,988	621	176
Interest expense	(336)	(1,080)	(1,337)
Loss on extinguishment of debt	(407)
Other (expense) income, net	(3,288)	(5,773)	76
Total other income (expense)	(43)	(6,232)	(1,085)
Net loss	(72,548)	(27,557)	(26,671)
Other comprehensive (loss) income:
Unrealized (loss) gain on marketable securities	(14)	(43)	20
Other comprehensive (loss) income	(14)	(43)	20
Comprehensive loss	$ (72,562)	$ (27,600)	$ (26,651)
Basic net loss per common share	$ (1.25)	$ (0.79)	$ (1.14)
Diluted net loss per common share	$ (1.26)	$ (0.79)	$ (1.14)
Weighted average common shares outstanding used to calculate basic net loss per common share	57,808,254	34,903,960	23,447,003
Weighted average common shares outstanding used to calculate diluted net loss per common share	57,838,299	34,903,960	23,447,003

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Balance at beginning of period at Dec. 31, 2015	$ 28,115	$ 2	$ 424,422	$ (21)	$ (396,288)
Balance at beginning of period (in shares) at Dec. 31, 2015		23,447,003
Stock-based compensation expense	2,473		2,473
Net loss	(26,671)				(26,671)
Net unrealized gain (loss) on marketable securities	20			20
Balance at end of period at Dec. 31, 2016	3,937	$ 2	426,895	(1)	(422,959)
Balance at end of period (in shares) at Dec. 31, 2016		23,447,003
Issuance of common stock upon exercise of warrants, value	1,058		1,058
Issuance of common stock upon exercise of warrants (Shares)		99,207
Issuance of common stock upon exercise of stock options and incentive awards	2,196		2,196
Issuance of common stock upon exercise of stock options and incentive awards (Shares)		607,138
Stock-based compensation expense	4,920		4,920
Issuance of common stock, value	100,436	$ 2	100,434
Issuance of common stock, (in shares)		20,255,448
Net loss	(27,557)				(27,557)
Net unrealized gain (loss) on marketable securities	(43)			(43)
Balance at end of period at Dec. 31, 2017	84,947	$ 4	535,503	(44)	(450,516)
Balance at end of period (in shares) at Dec. 31, 2017		44,408,796
Issuance of common stock upon exercise of warrants, value	11,929		11,929
Issuance of common stock upon exercise of warrants (Shares)		956,845
Issuance of common stock upon exercise of stock options, value	$ 3,571		3,571
Issuance of common stock upon exercise of stock options (Shares)	750,852	750,852
Stock-based compensation expense	$ 7,013		7,013
Issuance of common stock, value	135,520	$ 2	135,518
Issuance of common stock, (in shares)		13,340,000
Net loss	(72,548)				(72,548)
Net unrealized gain (loss) on marketable securities	(14)			(14)
Balance at end of period at Dec. 31, 2018	$ 170,418	$ 6	$ 693,534	$ (58)	$ (523,064)
Balance at end of period (in shares) at Dec. 31, 2018		59,456,493

Consolidated Statement of Sto_2

Consolidated Statement of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Statement Of Stockholders Equity [Abstract]
Stock issuance cost	$ 8,553	$ 7,047

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net loss	$ (72,548)	$ (27,557)	$ (26,671)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	105	35	29
Stock-based compensation expense	7,013	4,920	2,473
Net accretion and amortization of investments in marketable securities	(1,945)	(199)	125
Non-cash interest associated with debt discount accretion	148	437	476
Loss on extinguishment of debt	407
Change in fair value of warrant liability	3,710	5,773	(75)
Gain on extinguishment of warrant liability	(422)
Accretion of tenant improvement allowance	(263)
Changes in assets and liabilities:
Receivable from collaboration	5,000	(5,000)
Other current assets	(178)	(98)	165
Prepaid expenses	(1,386)	161	(761)
Other assets	(1,646)	120	(13)
Accounts payable	662	412	(109)
Accrued liabilities	6,450	1,387	1,015
Accrued interest payable	(43)	(23)	(7)
Net cash used in operating activities	(54,936)	(19,632)	(23,353)
Investing activities
Purchases of property and equipment	(529)	(27)	(42)
Purchases of marketable securities	(276,382)	(98,385)	(22,906)
Proceeds from maturities of marketable securities	222,800	30,884	50,076
Net cash (used in) provided by investing activities	(54,111)	(67,528)	27,128
Financing activities
Proceeds from issuance of common stock, net of issuance costs	135,520	100,436
Proceeds from issuance of common stock pursuant to equity award plans	3,571	2,189
Proceeds from issuance of common stock upon exercise of warrants	2,550	231
Repayment of facility loan principal	(6,527)	(3,137)	(986)
Payment of fees to extinguish facility loan	(126)
Net cash provided by (used in) financing activities	134,988	99,719	(986)
Net increase in cash and cash equivalents	25,941	12,559	2,789
Cash and cash equivalents at beginning of period	23,054	10,495	7,706
Cash and cash equivalents at end of period	48,995	23,054	10,495
Supplemental disclosure
Cash paid for interest	231	666	866
Supplemental non-cash investing and financing activities
Issuance of common stock upon warrant exercises	9,379	827
Lessor funded lease incentives included in property and equipment	2,256
Accrued property and equipment	$ 156
Net change in accrued financing costs		$ (144)	$ 144

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business CymaBay Therapeutics, Inc. (the Company or CymaBay) is a clinical-stage biopharmaceutical company focused on developing and providing access to innovative therapies for patients with liver and other chronic diseases with high unmet medical need. The Company’s key clinical development candidate is seladelpar (MBX-8025). Seladelpar is currently being developed for the treatment of the liver diseases primary biliary cholangitis (PBC) and nonalcoholic steatohepatitis (NASH). The Company was incorporated in Delaware in October 1988 as Transtech Corporation. The Company’s headquarters and operations are located in Newark, California and it operates in one segment. Liquidity The Company has incurred net operating losses and negative cash flows from operations since its inception. During the year ended December 31, 2018, the Company incurred a net loss of $72.5 million and used $54.9 million of cash in operations. At December 31, 2018, the Company had an accumulated deficit of $523.1 million. CymaBay expects to incur substantial research and development expenses as it continues to study its product candidates in clinical trials. To date, none of the Company’s product candidates have been approved for marketing and sale, and the Company has not recorded any revenue from product sales. As a result, management expects operating losses to continue in future years. The Company’s ability to achieve profitability is dependent primarily on its ability to successfully develop, acquire or in-license additional product candidates, continue clinical trials for product candidates currently in clinical development, obtain regulatory approvals, and support commercialization activities for partnered product candidates. Products developed by the Company will require approval of the U.S. Food and Drug Administration (FDA) or a foreign regulatory authority prior to commercial sale. The regulatory approval process is expensive, time-consuming, and uncertain, and any denial or delay of approval could have a material adverse effect on the Company. Even if approved, the Company’s products may not achieve market acceptance and will face competition from both generic and branded pharmaceutical products. As of December 31, 2018, the Company had cash, cash equivalents and marketable securities totaling $178.7 million which the Company believes is sufficient to fund the Company’s current operating plan into 2021.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Use of Estimates The accompanying consolidated financial statements are comprised of CymaBay and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The Company has no unconsolidated subsidiaries or investments accounted for under the equity method. These consolidated statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP), which requires management to make informed estimates and assumptions that impact the amounts and disclosures reported in the consolidated financial statements and accompanying notes. Certain reclassifications have been made to the prior period amounts to conform to the current year presentation. “Accrued clinical trial expenses” and “Other accrued liabilities”, which previously were reported as “Accrued liabilities” on the consolidated balance sheet, are now reported as separate line items. Accounting estimates and assumptions are inherently uncertain. Management bases its estimates on historical experience and on assumptions believed to be reasonable under the circumstances. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Actual results could differ materially from those estimates and assumptions. The Company believes significant judgment is involved in determining and in estimating the valuation of stock-based compensation, accrued clinical expenses, and equity instrument valuations. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. Estimates are assessed each reporting period and updated to reflect current information and any changes in estimates will generally be reflected in the period first identified. Fair Value of Financial Instruments The Company’s financial instruments during the periods reported consist of cash and cash equivalents, marketable securities, accounts receivable, prepaid expenses, other current assets, accounts payable, accrued interest payable, accrued expenses, the facility loan, and warrant liabilities. Fair value estimates of these instruments are made at a specific point in time based on relevant market information. These estimates may be subjective in nature and involve uncertainties and matters of significant judgment. The carrying amounts of financial instruments such as cash and cash equivalents, accounts receivable, prepaid expenses, other current assets, accounts payable, accrued expenses, and accrued interest payable approximate the related fair values due to the short maturities of these instruments. Based on prevailing borrowing rates available to the Company for loans with similar terms, the Company believes the fair value of the facility loan at December 31, 2017, considering level 2 inputs, approximated its carrying value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Assets and liabilities that are measured at fair value are reported using a three-level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and maximizes the use of unobservable inputs and is as follows: Level 1—Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Inputs other than quoted prices in active markets that are observable for the asset or liability, either directly or indirectly. Level 3—Inputs that are significant to the fair value measurement and are unobservable (i.e. supported by little market activity), which requires the reporting entity to develop its own valuation techniques and assumptions. The following tables present the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis using the above input categories (in thousands): As of December 31, 2018 Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds 39,481 - - 39,481 U.S. and foreign commercial paper - 6,469 - 6,469 Total cash equivalents 39,481 6,469 - 45,950 Short-term investments: U.S. and foreign commercial paper - 51,627 - 51,627 U.S. and foreign corporate debt securities - 34,634 - 34,634 Asset-backed securities - 25,472 - 25,472 U.S. treasury securities - 17,936 - 17,936 Total short-term investments - 129,669 - 129,669 Total assets measured at fair value $ 39,481 $ 136,138 $ — $ 175,619 As of December 31, 2017 Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds 12,822 - - 12,822 U.S. commercial paper - 6,035 - 6,035 Total cash equivalents 12,822 6,035 - 18,857 Short-term investments: U.S. and foreign commercial paper - 35,886 - 35,886 U.S. and foreign corporate debt securities - 19,760 - 19,760 Asset-backed securities - 11,060 - 11,060 U.S. treasury securities - 7,450 - 7,450 Total short-term investments - 74,156 - 74,156 Total assets measured at fair value 12,822 80,191 - 93,013 Warrant liability - - 6,091 6,091 Total liabilities measured at fair value - - 6,091 6,091 The Company estimates the fair value of its corporate debt, asset backed securities, and U.S. treasury securities by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. There were no transfers between Level 1 and Level 2 during the periods presented. Historically, the Company held a Level 3 liability associated with common stock warrants that were issued in connection with the Company’s financings completed in September and October 2013, January 2014, and August 2015. The warrants were accounted for as liabilities until either they were exercised or expired in September 2018. The Company used a binomial option pricing model to value its warrant liabilities prior to September 2017. The inputs for the binomial model are similar to the Black-Scholes model but also incorporate other more complex inputs that, in the Company’s case, included the expected timing, probability and valuation impact of certain potential strategic events. In September 2017, the Company changed its valuation technique and began to value its warrant liability using a Black-Scholes option pricing model, the inputs for which include: exercise price of the warrants, market price of the underlying common shares, dividend yield, expected term, expected volatility, and a risk-free interest rate. Changes to any of these inputs can have a significant impact on the estimated fair value of the warrants. The following tables set forth a summary of the changes in the fair value of the Company’s liabilities measured using Level 3 inputs (in thousands): Year Ended December 31, 2018 2017 Balance, beginning of period $ 6,091 $ 1,145 Change in fair value 3,710 5,773 Settlement of financial instruments (9,379 ) (827 ) Extinguishment of financial instruments (422 ) — Balance, end of period $ - $ 6,091 See Note 3 for further discussion regarding the carrying value of the Company’s financial instruments. Cash, Cash Equivalents, and Marketable Securities The Company considers all highly liquid investments with a remaining maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of deposits with commercial banks in checking, interest-bearing, demand money market accounts and commercial paper. The Company invests excess cash in marketable securities with high credit ratings that are classified in Level 1 and Level 2 of the fair value hierarchy. These securities consist primarily of corporate debt, commercial paper, asset-backed securities, and U.S. treasury securities and are classified as “available-for-sale.” The Company considers marketable securities as short-term investments if the maturity date is less than or equal to one year from the balance sheet date. The Company considers marketable securities as long-term investments if the maturity date is in excess of one year of the balance sheet date. Realized gains and losses from the sale of marketable securities, if any, are calculated using the specific-identification method. Realized gains and losses and declines in value judged to be other-than- temporary are included in interest income or expense in the consolidated statements of operations and comprehensive loss. Unrealized holding gains and losses are reported in accumulated other comprehensive loss in the consolidated balance sheets. To date, the Company has not recorded any impairment charges on its marketable securities related to other-than-temporary declines in market value. In determining whether a decline in market value is other-than-temporary, various factors are considered, including the cause, duration of time and severity of the impairment, any adverse changes in the investees’ financial condition, and the Company’s intent and ability to hold the security for a period of time sufficient to allow for an anticipated recovery in market value. Concentration of Credit Risk Cash, cash equivalents, and marketable securities consist of financial instruments that potentially subject the Company to a concentration of credit risk to the extent of the fair value recorded in the balance sheet. The Company invests cash that is not required for immediate operating needs primarily in highly liquid instruments that bear minimal risk. The Company has established guidelines relating to the quality, diversification, and maturities of securities to enable the Company to manage its credit risk. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents and investments and issuers of investments to the extent recorded on the consolidated balance sheets. Certain materials and key components that the Company utilizes in its operations are obtained through single suppliers. Since the suppliers of key components and materials must be named in a NDA filed with the FDA for a product, significant delays can occur if the qualification of a new supplier is required. If delivery of material from the Company’s suppliers were interrupted for any reason, the Company may be unable to supply any of its product candidates for clinical trials. Property and Equipment Property and equipment is recorded at cost, less accumulated depreciation and amortization. Depreciation and amortization is calculated using the straight-line method, and the cost is amortized over the estimated useful lives of the respective assets, generally three to seven years. Leasehold improvements are amortized over the shorter of the useful lives or the non-cancelable term of the related lease. Maintenance and repair costs are charged as expense in the consolidated statements of operations and comprehensive loss as incurred. Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment loss is recognized if the estimated undiscounted future cash flow expected to result from the use and eventual disposition of an asset is less than the carrying amount. While the Company’s current and historical operating losses and cash flows are indicators of impairment, the Company believes the future cash flows to be received support the carrying value of its long-lived assets. Accordingly, the Company has not recognized any impairment losses for the years ended December 31, 2018, 2017 or 2016. Leases The Company leases office space under a non-cancelable operating lease agreement and recognizes related rent expense on a straight-line basis over the term of the lease. Incentives granted under the Company’s office lease, including allowances for leasehold improvements and rent holidays, are recognized as reductions to rental expense on a straight-line basis over the term of the lease. The Company does not assume renewals in its determination of the lease term unless they are deemed to be reasonably assured at the inception of the lease and begins recognizing rent expense on the date that it obtains the legal right to use and control the leased space. Deferred rent consists of the difference between cash payments and the rent expense recognized. Revenue Recognition At the inception of an arrangement, the Company evaluates if a counterparty to a contract is a customer, if the arrangement is within the scope of revenue from contracts with customers guidance, and the term of the contract. The Company recognizes revenue when its customer obtains control of promised goods or services in a contract for an amount that reflects the consideration the Company expects to receive in exchange for those goods or services. For contracts with customers, the Company applies the following five-step model in order to determine this amount: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. As part of the accounting for contracts with customers, the Company must develop assumptions that require judgment to determine the standalone selling price of each performance obligation identified in the contract. The Company then allocates the total transaction price to each performance obligation based on the estimated standalone selling prices of each performance obligation. The Company recognizes the amount of the transaction price as revenue that is allocated to the respective performance obligation when the performance obligation is satisfied or as it is satisfied. Generally, the Company's performance obligations are transferred to customers at a point in time, typically upon delivery. The Company enters into collaboration arrangements, under which it licenses certain rights to its intellectual property to third parties. The terms of these agreements may include payment to the Company of one or more of the following: nonrefundable, upfront license fees; development and commercial milestone payments; funding of research and/or development activities; and royalties on net sales of licensed products. Revenues that result from these payments are classified as collaborative revenues except for royalties on net sales of licensed products, which are classified as royalty revenues. For each collaboration agreement that results in revenues, the Company identifies all material promised goods and services, which may include one or more of the following: a license to intellectual property and know-how, research and development services, and other transition support services. Promised goods or services are considered to be separate performance obligations if they are distinct. To determine the transaction price to be allocated to each performance obligation, in addition to any upfront payment, the Company estimates the amount of variable consideration at the outset of the contract either utilizing the expected value or most likely amount method, depending on the facts and circumstances relative to the contract. The Company constrains (reduces) the estimates of variable consideration such that it is probable that a significant reversal of previously recognized revenue, deferred revenue, or other amounts will not occur in future reporting periods. When determining if variable consideration should be constrained, management considers whether there are factors outside the Company’s control that increase the likelihood of a significant reversal of previously recognized revenue and revenue-related amounts in future reporting periods. These estimates are re-assessed each reporting period as necessary depending on the facts and circumstances of each contract. Once the estimated transaction price is established, amounts are allocated to identified performance obligations. The transaction price is generally allocated to each separate performance obligation on a relative standalone selling price (SSP) basis. The Company must develop assumptions that require judgment to determine the SSP to account for these agreements. To determine the SSP the Company’s assumptions may include (i) assumptions regarding the probability of obtaining marketing approval for the drug candidate, (ii) estimates regarding the timing of and the expected costs to develop and commercialize the drug candidate, (iii) estimates of future cash flows from potential product sales with respect to the drug candidate and (iv) appropriate discount and tax rates. SSPs used to perform the initial allocation are not updated after contract inception. The Company does not include a financing component to its estimated transaction price at contract inception unless it estimates that certain performance obligations will not be satisfied within one year. Upfront License Fees: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from nonrefundable, upfront license fees based on the relative value prescribed to the license compared to the total value of the arrangement. The revenue is recognized when the license is transferred to the collaborator and the collaborator is able to use and benefit from the license. For licenses that are not distinct from other obligations identified in the arrangement, 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. If the combined performance obligation is satisfied over time, the Company applies an appropriate method of measuring progress for purposes of recognizing revenue from nonrefundable, upfront license fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Development and Regulatory Milestone Payments : Depending on facts and circumstances, the Company may conclude that it is appropriate to include the milestone in the estimated transaction price using the most likely amount method or that it is appropriate to fully constrain the milestone. A milestone payment is included in the transaction price in the reporting period that the Company concludes that it is probable that recording revenue in the period will not result in a significant reversal in amounts recognized in future periods. The Company may record revenues from certain milestones in a reporting period before the milestone is achieved if the Company concludes that achievement of the milestone is probable and that recognition of revenue related to the milestone will not result in a significant reversal in amounts recognized in future periods. The Company records a corresponding contract asset when this conclusion is reached. Until that determination is made, milestone payments that have not been included in the transaction price to date are fully constrained. The Company re-evaluates the probability of achievement of such development milestones and any related constraint each reporting period. The Company adjusts its estimate of the overall transaction price, including the amount of collaborative revenue that it has recorded, if necessary. Sales-based Milestone and Royalty Payments: The Company’s collaborators may be required to pay the Company sales-based milestone payments or royalties on future sales of commercial products. The Company recognizes revenues related to sales-based milestone and royalty payments upon the later to occur of (i) achievement of the collaborator’s underlying sales or (ii) satisfaction of any performance obligation(s) related to these sales, in each case assuming the license to the Company’s intellectual property is deemed to be the predominant item to which the sales-based milestones and/or royalties relate. Research and Development Expenses Research and development expenses consist of costs incurred in identifying, developing, and testing product candidates. These expenses consist primarily of costs for research and development personnel, including related stock-based compensation; contract research organizations (CRO) and other third parties that assist in managing, monitoring, and analyzing clinical trials; investigator and site fees; laboratory services; consultants; contract manufacturing services; non-clinical studies, including materials; and allocated expenses, such as depreciation of assets, and facilities and information technology that support research and development activities. Research and development costs are expensed as incurred, including expenses that may or may not be reimbursed under research and development funding arrangements. Payments made prior to the receipt of goods or services to be used in research and development are recorded as prepaid assets until the goods are received or services are rendered. Such payments are evaluated for current or long term classification based on when they will be realized. The Company records expenses related to clinical studies and manufacturing development activities based on its estimates of the services received and efforts expended pursuant to contracts with multiple CROs and manufacturing vendors that conduct and manage these activities on its behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows. There may be instances in which payments made to the Company’s vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of subjects and the completion of clinical trial milestones. In amortizing or accruing service fees, the Company estimates the time period over which services will be performed, enrollment of subjects, number of sites activated and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the Company’s estimate, the Company will adjust the accrued or prepaid expense balance accordingly. To date, there have been no material differences from the Company’s estimates to the amounts actually incurred. Stock-Based Compensation Employee and director stock-based compensation is measured at fair value on the grant date of the award. Compensation cost is recognized as expense on a straight-line basis over the vesting period for options and on an accelerated basis for stock options with performance conditions, net of estimated forfeitures. For stock options with performance conditions, the Company evaluates the probability of achieving performance conditions at each reporting date. The Company begins to recognize the expense when it is deemed probable that the performance conditions will be met. The Company uses the Black-Scholes option pricing model to determine the fair value of stock option awards. The determination of fair value for stock-based awards using an option-pricing model requires management to make certain assumptions regarding subjective input variables such as expected term, dividends, volatility and risk-free rate. The Company is also required to make estimates as to the probability of achieving the specific performance criteria. If actual results are not consistent with the Company’s assumptions and judgments used in making these estimates, the Company may be required to increase or decrease compensation expense, which could be material to the Company’s results of operations. Equity awards granted to non-employees are valued using the Black-Scholes option pricing model. Stock-based compensation expense for nonemployee services is subject to remeasurement as the underlying equity instruments vest and is recognized as an expense over the period during which services are received. Common Stock Warrant Liabilities Historically, the Company’s outstanding common stock warrants issued in connection with certain equity and debt financings that occurred in 2013 through 2015 were classified as liabilities in the accompanying consolidated balance sheets because of certain contractual terms that preclude equity classification. All outstanding warrants related to these financings had been exercised or had expired by September 30, 2018. Upon expiration, the remaining fair value of the liability was extinguished and credited to other (expense) income, net in the Company’s consolidated statement of operations. Prior to expiration, the Company estimated the fair value of common stock warrants at each reporting period until the exercise of the warrants, at which time the liability was revalued and reclassified to stockholders’ equity. The determination of fair value of these common stock warrants required management to make certain assumptions regarding subjective input variables such as timing, probability and valuation impact of certain potential strategic events, expected term, dividends, expected volatility and risk-free interest rates. Income Taxes The Company utilizes the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and the tax bases of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. A valuation allowance is recorded when it is more likely than not that all or part of a deferred tax asset will not be realized. When the Company establishes or reduces the valuation allowance related to the deferred tax assets, the provision for income taxes will increase or decrease, respectively, in the period such determination is made. The accounting guidance for uncertainty in income taxes prescribes a recognition threshold and measurement attribute criteria for the financial 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 based on the technical merits of the position. The Company is required to file federal and state income tax returns in the United States. The preparation of these income tax returns requires the Company to interpret the applicable tax laws and regulations in effect that could affect the amount of tax paid to these jurisdictions. In December 2017, Securities and Exchange Commission (SEC) staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act The Company records interest related to income tax reserves, if any, as interest expense, and any penalties would be recorded as other expense in the consolidated statements of operations and comprehensive loss. There was no interest or penalties related to income tax reserves during the years ended December 31, 2018, 2017 and 2016. Comprehensive Loss Comprehensive loss includes net loss and net unrealized gains and losses on marketable securities, which are presented in a single continuous statement. Other comprehensive (loss) gain is also disclosed in the consolidated balance sheets and statements of stockholders’ equity in accumulated other comprehensive loss, and is stated net of related tax effects, if any. Net Loss Per Common Share Basic net loss per share of common stock is based on the weighted average number of shares of common stock outstanding equivalents during the period. Diluted net loss per share of common stock is calculated as the weighted average number of shares of common stock outstanding adjusted to include the assumed exercises of stock options and common stock warrants, if dilutive. The calculation of diluted loss per share also requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of the common stock warrants and the presumed exercise of such securities are dilutive to earnings (loss) per share for the period, adjustments to net income or net loss used in the calculation are required to remove the change in fair value of the common stock warrant liability for the period. Likewise, adjustments to the denominator are required to reflect the related dilutive shares. In all periods presented, the Company’s outstanding stock options were excluded from the calculation of net loss per share because the effect would be antidilutive. The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share amounts): Year Ended December 31, 2018 2017 2016 Numerator: Net loss allocated to common stock—basic $ (72,548 ) $ (27,557 ) $ (26,671 ) Adjustment for revaluation and extinguishment of common stock warrants (422 ) - - Net loss allocated to common stock—diluted $ (72,970 ) $ (27,557 ) $ (26,671 ) Denominator: Weighted average number of common stock shares outstanding - basic 57,808,254 34,903,960 23,447,003 Dilutive securities: Common stock warrants 30,045 - - Weighted average number of common stock shares outstanding - diluted 57,838,299 34,903,960 23,447,003 Net loss per share—basic $ (1.25 ) $ (0.79 ) $ (1.14 ) Net loss per share—diluted $ (1.26 ) $ (0.79 ) $ (1.14 ) The following table shows the total outstanding securities considered anti-dilutive and therefore excluded from the computation of diluted net loss per share (in thousands): Year Ended December 31, 2018 2017 2016 Common stock warrants - 1,461 1,667 Common stock options 5,593 4,356 2,721 Incentive awards 130 130 239 Total 5,723 5,947 4,627 Recently Adopted Accounting Pronouncements Accounting Standards Update 2014-09 On January 1, 2018, the Company adopted ASU No. 2014-09, Revenue from Contracts with Customers Accounting Standards Update 2017-09 In May 2017, the Financial Accounting Standards Board (FASB) issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718) - Scope of Modification Accounting Accounting Standards Update 2016-15 In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230: Classification of Certain Cash Receipts and Cash Payments) SEC Securities Act Release No. 33-10532 In August 2018, the SEC adopted amendments to certain disclosure requirements in Securities Act Release No. 33-10532, Disclosure Update and Simplification Recently Issued Accounting Pronouncements standard can be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company is currently evaluating the impact of adoption on its consolidated financial statements. Accounting Standards Update 2018-13 In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework – Accounting Standards Update 2018-08 In June 2018, the FASB issued ASU No. 2018-08, Not-For-Profit Entities (Topic 958): Clarifying the Scope and the Accounting Guidance for Contributions Received and Contributions Made, which is intended to clarify and improve the scope and the accounting guidance for contributions received and contributions made. The amendments in A

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2018
Cash And Cash Equivalents [Abstract]
Marketable Securities	3. Marketable Securities Marketable available-for-sale securities as of December 31, 2018 and 2017 consist of the following (in thousands): Gross Gross Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value As of December 31, 2018: U.S. and foreign commercial paper $ 51,627 $ - $ - $ 51,627 U.S. and foreign corporate debt securities 34,668 - (34 ) 34,634 Asset-backed securities 25,494 - (22 ) 25,472 U.S. treasury securities 17,938 - (2 ) 17,936 $ 129,727 $ - $ (58 ) $ 129,669 Gross Gross Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value As of December 31, 2017: U.S. and foreign commercial paper $ 35,886 $ - $ - $ 35,886 U.S. and foreign corporate debt securities 19,785 - (25 ) 19,760 Asset-backed securities 11,070 - (10 ) 11,060 U.S. treasury securities 7,459 - (9 ) 7,450 $ 74,200 $ - $ (44 ) $ 74,156 The Company’s commercial paper and corporate debt securities consist of U.S. and foreign securities, from issuers in various sectors including finance and industry. The Company’s asset-backed securities consist of credit card receivables with investment-grade ratings. As of December 31, 2018 and 2017, the remaining contractual maturities of the Company’s commercial paper, corporate debt securities, asset-backed securities, and U.S. treasury securities were less than 1 See Note 2 for further information regarding the fair value of the Company’s financial statements.

Certain Balance Sheet Items

Certain Balance Sheet Items	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Certain Balance Sheet Items	4. Certain Balance Sheet Items Property and equipment consist of the following (in thousands): December 31, 2018 2017 Leasehold improvements $ 2,417 $ 65 Office and computer equipment 214 177 Purchased software 44 83 Furniture and fixtures 360 65 Total 3,035 390 Less accumulated depreciation and amortization (130 ) (321 ) Property and equipment, net $ 2,905 $ 69 Other accrued liabilities consist of the following (in thousands): December 31, 2018 2017 Accrued compensation $ 2,759 $ 2,416 Accrued professional fees and other 670 399 Deferred rent 425 13 Total other accrued liabilities $ 3,854 $ 2,828

Collaboration and License Agree

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreements	5. Collaboration and License Agreements Kowa Pharmaceuticals America, Inc. On December 30, 2016, the Company entered into a license agreement with Kowa. Pursuant to the license agreement, the Company granted to Kowa an exclusive license, and right to sublicense, certain patent rights and technology related to arhalofenate. Kowa will have exclusive rights to, among other things, develop, use, manufacture, sell and otherwise exploit the licensed technology in the United States (including all possessions and territories). At Kowa’s option, the Company may also facilitate the placement of arhalofenate product manufacturing orders under the terms of the Company’s existing contract manufacturing agreements. In addition, the Company will complete specified in-process stability testing and non-clinical development services and will participate on a Joint Advisory Committee (JAC). Finally, the Company will transfer to Kowa certain arhalofenate product on hand. Under the license agreement, Kowa agreed to pay the Company a non-refundable upfront payment of $5.0 million upon contract execution. Kowa also agreed to pay the Company $5.0 million upon initiation of a study evaluating the pharmacokinetics of arhalofenate in subjects with renal impairment, which occurred during the quarter ended December 31, 2017 and payment was received in January 2018. An additional milestone payment of $5.0 million is due on initiation of a Phase 3 study of arhalofenate, and up to $190.0 million based upon the achievement of other specific development and sales milestones. The Company concluded that Kowa is a customer, and the contract is not subject to accounting literature on collaborative arrangements. This is because the Company granted to Kowa a license to its intellectual property and provided drug product and research and pre-clinical development services, all of which are outputs of the Company’s ongoing activities, in exchange for consideration. The Company identified the following three material promises under the license agreement: 1) the transfer of a license to intellectual property, inclusive of the related technology know-how conveyance and contract manufacturing rights and privileges (“license and know-how”); 2) the performance of specific ongoing research and non-clinical development services; and 3) the delivery of existing on hand arhalofenate clinical product. The Company’s participation on the JAC is not a performance obligation as the Company’s participation in the JAC is not required and is primarily for the Company’s benefit to obtain updates on the progress of Kowa’s activities. The Company provided to Kowa standard indemnification and protection of licensed intellectual property, which is part of assurance that the license meets the contract’s specifications and is not an obligation to provide goods or services. The Company concluded that the license and know-how, the research and development services, and delivery of arhalofenate product were separate performance obligations since each was identified as a material promise that was by itself distinct. The Company concluded that Kowa can benefit from the license and know-how on its own by developing and commercializing arhalofenate arhalofenate. The To allocate transaction price among the three performance obligations, the Company estimated its SSP. For the license and know-how, the SSP was estimated using the income approach based on assumptions regarding Kowa’s future revenues from the licensed intellectual property, projected costs of research and development, manufacturing and commercialization expenses, as well as the discount rate, the development timeline, and probabilities of technical and regulatory success. To estimate SSP of research and non-clinical development services and arhalofenate product on hand, the Company used a cost-plus margin approach. The Company believes that a change in the assumptions used to determine its best estimate of selling price for the performance obligations would not have a significant effect on the allocation of consideration received to the performance obligations. As of January 1, 2018, the transaction price was limited to $10.0 million, consisting of a $5.0 million upfront fee due upon contract initiation and a $5.0 million development milestone payment triggered when Kowa initiated a study evaluating the pharmacokinetics of arhalofenate in subjects with renal impairment. Of these amounts, the Company allocated $9.5 million to the license; $0.4 million to the arhalofenate product; and $0.1 million to the research and pre-clinical development services. As of January 1, 2018, all these performance obligations had been completed and the associated revenue had been recognized. The Company expensed the incremental costs of obtaining the Kowa contract prior to December 31, 2017, as substantially all costs related to the performance obligations completed by that date. Revenue recognized during the year ended December 31, 2017 was determined in accordance with the accounting rules applicable prior to the adoption of ASC 606 on January 1, 2018. There was no difference in the revenue recognized under ASC 606 or legacy GAAP for the year ended December 31, 2018. There were no contract assets or deferred revenues (contract liabilities) recorded during the year ended December 31, 2018. Accounts receivable from the Kowa contract consisted of the following (in thousands): December 31, 2018 2017 Accounts Receivable $ - $ 5,000 On October 24, 2018, the Company received a notice of Kowa’s intent to terminate the license agreement for the development of arhalofenate. The termination will be effective on January 22, 2019. As a result of the termination, the rights licensed to Kowa through the agreement revert to the Company on the termination date and the Company is no longer eligible to receive additional milestone payments or royalties from Kowa. As of the time of the receipt of Kowa’s notice to terminate, all remaining variable consideration under the license agreement had been fully constrained and all performance obligations had been satisfied. Janssen Pharmaceutical NV and Janssen Pharmaceuticals, Inc. In June 2006, the Company entered into an exclusive worldwide, royalty-bearing license to seladelpar and certain other PPARδ compounds (the PPARδ Products) with Janssen Pharmaceutical NV (Janssen NV), with the right to grant sublicenses to third parties to make, use and sell such PPARδ Products. Under the terms of the agreement, the Company has full control and responsibility over the research, development and registration of any PPARδ Products and is required to use diligent efforts to conduct all such activities. Janssen NV has the sole responsibility for the preparation, filing, prosecution, maintenance of, and defense of the patents with respect to, the PPARδ Products. Janssen NV has a right of first negotiation under the agreement to license PPARδ Products from the Company in the event that the Company elects to seek a third party corporate partner for the research, development, promotion, and/or commercialization of such PPARδ Products. Under the terms of the agreement Janssen NV is entitled to receive up to an 8% royalty on net sales of PPARδ Products. In June 2010, the Company entered into two development and license agreements with Janssen Pharmaceuticals, Inc. (Janssen), a subsidiary of Johnson and Johnson, to further develop and discover undisclosed metabolic disease target agonists for the treatment of Type 2 diabetes and other disorders and received a one-time nonrefundable technology access fee related to the agreements. The Company received a termination notice from Janssen, effectively ending these development and licensing agreements in early April 2015. In December 2015, the Company exercised an option pursuant to the terms of one of the original agreements to continue work to research, develop and commercialize compounds with activity against an undisclosed metabolic disease target. Janssen granted the Company an exclusive, worldwide license (with rights to sublicense) under the Janssen know-how and patents to research, develop, make, have made, use, offer for sale and sell such compounds. The Company has full control and responsibility over the research, development and registration of any products developed and/or discovered from the metabolic disease target and is required to use diligent efforts to conduct all such activities. DiaTex, Inc. In June 1998, the Company entered into a license agreement with DiaTex, Inc. (DiaTex) relating to products containing halofenate, its enantiomers, derivatives, and analogs (the licensed products). The license agreement provides that DiaTex and the Company are joint owners of all of the patents and patent applications covering the licensed products and methods of producing or using such compounds, as well as certain other know-how (the covered IP). As part of the license agreement, the Company received an exclusive worldwide license, including as to DiaTex, to use the covered IP to develop and commercialize the licensed products. The Company also retained the right to sub-license the covered IP. The license agreement contains a $2,000 per month license fee as well as a requirement to make additional payments for development achievements and royalty payments on any sales of licensed products. DiaTex is entitled to up to $0.8 million for the future development of arhalofenate, as well as royalty payments on commercial sales of products containing arhalofenate. In December 2016, the agreement was amended by the parties to change the timing of a specified development milestone. No development payments were made or due as of and for the years ended December 31, 2018, 2017 and 2016 and no royalties have been paid to date.

Facility Loans

Facility Loans	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Facility Loans	6. Facility Loans On August 7, 2015, the Company entered into a Loan and Security Agreement (the 2015 Term Loan Facility) pursuant to which it refinanced its existing term loan facility for an aggregate amount of up to $15.0 million. The first $10.0 million tranche of this new loan facility was made available to the Company immediately upon the closing and was used in part to retire all $4.1 million of the Company’s existing debt outstanding under the prior term loan facility, and to settle accrued interest and closing costs with the lenders. The remaining $5.0 million, referred to as the second tranche, was made available to the Company until March 31, 2016, for draw down upon the achievement of a specified milestone but expired as the second draw milestone was not achieved. The loan bore interest at 8.77%. The Company was required to make 12 monthly interest only payments after the funding date followed by a repayment schedule equal to 36 equal monthly payments of interest and principal. Upon maturity, the remaining balance of the first tranche and a final payment equal to 6.50% of the original principal amount advanced of the applicable tranche were payable. At the closing, the Company also agreed to pay a facility fee of 1.00% of the 2015 Term Loan Facility commitment. In addition, the Company issued warrants exercisable for a total of 114,436 shares of its common stock to the lenders at an exercise price of $2.84 per share, and with a term of ten years. Upon issuance, the fair value of a warrant liability of $0.3 million was recorded in the accompanying consolidated balance sheet, to be revalued at each balance sheet date until the warrants were exercised or expire. On June 4, 2018, the Company repaid in full the outstanding balance of the 2015 Term Loan Facility of $4.2 million plus a final fee of $0.7 million and a prepayment penalty of $0.1 million. In conjunction with this prepayment, the Company recorded a $0.4 million loss on early of extinguishment of this debt. As of December 31, 2018, the Company had no further obligations under the 2015 Term Loan Facility and all warrants previously issued in connection with it had been exercised. The term loan facility, debt discounts and final payment balances as of December 31, 2018 and 2017 are as follows (in thousands): December 31, 2018 2017 Principal payments due under the loan facility $ - $ 5,877 Less: unamortized debt discount - (296 ) Plus: accreted value of final payment - 517 Term loan facility, net $ - $ 6,098

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Operating Lease Commitments Rent expense was $0.3 million for each of the years ended December 31, 2018, 2017 and 2016. From January 2014 to November 2018, the Company leased 8,894 square feet of office space in Newark, California pursuant to a lease which commenced January 16, 2014 and was set to expire on January 15, 2019. On April 16, 2018, the Company entered into an amended lease to extend the term of its original lease by five years to January 15, 2024 and relocate and expand its office space within the same office park in Newark, California to approximately 17,698 square feet. The lease agreement includes an escalation clause for increased rent and a renewal provision allowing the Company to extend this lease for an additional five years by giving the landlord written notice of the election to exercise the option prior to the amended expiration date of January 15, 2024. The lease agreement also requires the lessor to fund and complete the construction of certain tenant improvements. These improvements were placed into service on December 1, 2018 and are classified as property and equipment, net on the consolidated balance sheet. The Company estimated the value of these tenant improvements at $2.3 million and also recorded them as a lease incentive within deferred rent on the Company’s consolidated balance sheet. Future minimum rent payments under noncancelable operating lease commitments are as follows (in thousands): Lease Payments Year ending December 31: 2019 $ 628 2020 647 2021 666 2022 687 2023 707 Thereafter 30 Total future minimum lease payments $ 3,365 Indemnification In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnification, including indemnification associated with product liability or infringement of intellectual property rights. The Company’s exposure under these agreements is unknown because it involves future claims that may be made against the Company that may be, but have not yet been, made. To date, the Company has not paid any claims or been required to defend any action related to these indemnification obligations, and no amounts have been accrued in the accompanying consolidated balance sheets related to these indemnification obligations. The Company has agreed to indemnify its officers and directors for losses and costs incurred in connection with certain events or occurrences, including advancing money to cover certain costs, subject to certain limitations. The maximum potential amount of future payments the Company could be required to make under this indemnification is unlimited; however, the Company maintains insurance policies that may limit its exposure and may enable it to recover a portion of any future amounts paid. Assuming the applicability of coverage, the willingness of the insurer to assume coverage, and subject to certain retention, loss limits, and other policy provisions, the Company believes the fair value of these indemnification obligations is not material. Accordingly, the Company has not recognized any liabilities relating to these obligations as of December 31, 2018 and 2017. No assurances can be given that the covering insurers will not attempt to dispute the validity, applicability, or amount of coverage without expensive litigation against these insurers, in which case the Company may incur substantial liabilities as a result of these indemnification obligations.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	8. Stockholders’ Equity The Company is authorized to issue 10,000,000 shares of preferred stock as of December 31, 2018 and 2017, respectively. The Company is authorized to issue 100,000,000 shares of common stock as of December 31, 2018 and 2017, respectively. Common Stock Issuances On February 7, 2017, pursuant to a shelf registration statement on Form S-3, the Company completed the issuance of 5,181,348 shares of its common stock at $1.93 per share which the Company refers to as the February 2017 public offering. Net proceeds to the Company in connection with the February 2017 public offering were approximately $9.2 million after deducting underwriting discounts, commissions and other offering expenses. On July 24, 2017, pursuant to a shelf registration statement on Form S-3, the Company completed the issuance of 14,950,000 shares of its common stock at $6.50 per share, which the Company refers to as the July 2017 public offering. Net proceeds to the Company in connection with the July 2017 public offering were approximately $91.1 million after deducting underwriting discounts, commissions and other offering expenses. On February 1, 2018, pursuant to a new $200 million shelf registration statement on Form S-3, the Company completed the issuance of 13,340,000 shares of its common stock at $10.80 per share, which the Company refers to as the February 2018 public offering. Net proceeds in connection with the February 2018 public offering were approximately $135.5 million after deducting underwriting discounts, commissions and other offering expenses. On December 28, 2018, the Company filed a new $200 million shelf registration statement on Form S-3 that was declared effective in February 2019. The Company’s existing $200 million shelf registration statement was also terminated on the effective date. Common Stock Warrants In connection with a 2013 financing and the Company’s private placement of common stock and warrants in September 2013, October 2013 and January 2014, the Company issued five-year warrants to purchase 1,741,788 shares of the Company’s common stock at an exercise price of $5.75 per share (referred to as the 2013 financing warrants). The Company also issued seven-year warrants to purchase 121,739 shares of the Company’s common stock to certain lenders at an exercise price of $5.00 per share in September 2013 and in connection with the 2015 loan facility, the Company issued ten-year warrants to purchase 114,436 shares of its common stock to its lenders at an exercise price of $2.84 per share (referred to as the lender warrants). The 2013 financing warrants contain anti-dilution provisions that are contingent on the occurrence of a major transaction which precludes them from being indexed to the Company’s common stock and also do not meet other criteria for equity classification. Such provisions could also result in the settlement of the 2013 financing warrants for more shares of common stock than the Company has authorized. Due to these provisions, the Company is required to account for the 2013 financing warrants and the lender warrants as liabilities at fair value. Accordingly, the Company recorded the warrants at fair value upon issuance and remeasured them at fair value at each balance sheet date until they were exercised or expired. As of December 31, 2018 and 2017, the Company’s warrants were remeasured using Level 3 inputs involving a Black-Scholes option pricing model, the inputs for which include: the exercise price of the warrants; the market price of the underlying common shares; a risk-free interest rate based on the rates for U.S. treasury zero-coupon bonds with maturities similar to those of the remaining contractual term of the warrants; an assumed dividend yield of zero based on the Company’s expectation that it will not pay dividends in the foreseeable future; an expected term based on the remaining contractual term of the warrants; and expected volatility based upon the Company’s historical volatility. The significant unobservable input used in measuring the fair value of the common stock warrant liabilities is the expected volatility. Significant increases in volatility would result in a higher fair value measurement. The resulting increases in warrant liability fair value of $3.7 million and $5.8 million for the years ended December 31, 2018 and 2017, respectively, were recorded as revaluation losses in other (expense) income, net in the Company’s consolidated statement of operations and comprehensive loss. During the year ended December 31, 2018, 443,505 warrants were exercised for cash proceeds of $2.6 million and 938,300 warrants were cashless exercised for 513,340 shares of the Company’s common stock. During the year ended December 31, 2017, 40,250 warrants were exercised for cash proceeds of $0.2 million and 166,193 warrants were cashless exercised for 58,957 shares of the Company’s common stock. On September 30, 2018, 79,150 of remaining unexercised warrants expired, resulting in the recognition of a $0.4 million gain on extinguishment of the related warrant liability. As of December 31, 2018, no warrants were outstanding. Shares of Common Stock Authorized for Issuance As of December 31, 2018 and 2017, the Company had reserved shares of authorized but unissued common stock as follows: December 31, 2018 2017 Common stock warrants - 1,460,955 Equity incentive plan 6,991,570 4,021,983 Total reserved shares of common stock 6,991,570 5,482,938

Stock Plan and Stock-Based Comp

Stock Plan and Stock-Based Compensation	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Plans and Stock-Based Compensation	9. Stock Plan and Stock-Based Compensation Stock Plan In September 2013, the Company’s stockholders approved the 2013 Equity Incentive Plan (the 2013 Plan), under which shares of common stock are reserved for the granting of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance stock awards, performance cash awards and other stock awards by the Company. These awards may be granted to employees, members of the Board of Directors, and consultants. The 2013 Plan has a term of ten years and replaced the 2003 Equity Incentive Plan, which had similar terms. The 2013 Plan permits the Company to (i) grant incentive stock options to directors and employees at not less than 100% of the fair value of common stock on the date of grant; (ii) grant nonqualified options to employees, directors, and consultants at not less than 85% of fair value; (iii) award stock bonuses; and (iv) grant rights to acquire restricted stock at not less than 85% of fair value. Options generally vest over a four year period and have a term of ten years. Options granted to 10% stockholders have a maximum term of five years and require an exercise price equal to at least 110% of the fair value on the date of grant. The exercise price of all options granted to date has been at least equal to the fair value of common stock on the date of grant. The share reserve under the 2013 Plan will automatically increase on January 1 st st st Stock Plan Activity As of December 31, 2018, there were 1,268,662 shares available for grant under the 2013 Plan. In accordance with the provisions of the 2013 Plan, the Board of Directors reduced the automatic increase in the share reserve to 2,378,259 shares, which were automatically available for issuance on January 1, 2019. The following table summarizes activity in the Company’s stock option grants, including performance options: Shares Subject to Outstanding Options Weighted Average Exercise Price of Options Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2017 4,356,441 $ 5.15 Options granted 2,167,272 11.84 Options exercised (750,852 ) 4.76 Options forfeited (179,729 ) 8.81 Outstanding as of December 31, 2018 5,593,132 $ 7.68 8.04 $ 11,096 Vested and expected to vest as of December 31, 2018 5,593,132 7.68 8.04 11,096 Exercisable as of December 31, 2018 2,627,819 $ 5.65 7.07 $ 7,799 The total intrinsic value of options exercised was $4.9 million and $2.5 million for the years ended December 31, 2018 and 2017, respectively. No options were exercised during the year ended December 31, 2016. Vested and Unvested Awards The total fair value of options vested including performance options, was $7.0 million, $3.9 million, and $2.2 million for the years ended December 31, 2018, 2017 and 2016, respectively. As of December 31, 2018, unamortized employee and non-employee stock-based compensation expense of $16.6 million is expected to be recognized over a weighted average period of 2.8 years. Performance Options In July 2016, the Company granted 327,000 performance-based stock options (PSOs) to executives and senior officers. PSOs represent a contingent right to purchase the Company’s common stock upon the achievement of specific conditions. Specifically, these PSOs vest upon the achievement of certain clinical development and capital raising milestones that must occur before December 31, 2016. In December 2016, the PSOs were modified by extending the term by one month to January 31, 2017. Upon achievement of the clinical development and capital raising milestones, related expense of $0.2 million was recognized in each of the years ended December 31, 2017 and 2016, respectively. The modification to extend the term of the PSOs did not have a material impact on the Company’s consolidated financial statements. There was no expense in 2018 associated with these awards. Incentive Awards In December 2013, January 2014, and April 2014, as permitted by the 2013 Plan, the Company issued certain incentive awards to directors, employees and a consultant which are subject to 252,752 shares of the Company’s common stock and are exercisable at a weighted average price of $5.21 per share when vested. The Company may determine at its option whether to settle exercised awards in shares of common stock or in cash. Each recipient’s incentive award defines the number of common shares that may be acquired upon exercise provided the Company chooses to settle in shares. For awards settled in cash, the Company must pay the recipient the excess of the fair market value of the Company’s common stock on the date of exercise over the exercise price paid by the recipient multiplied by the number of shares the recipient would be entitled to receive had the award been settled in shares of the Company’s common stock. Pursuant to their terms, the incentive awards have a term of 10 years and were initially scheduled to vest 100% on the second anniversary of their grant date. However, as a result of the approval by the Company’s stockholders of a 500,000 share increase to the 2013 Plan’s share reserve in June 2014, the incentive awards were automatically modified to vest monthly over four years effective from their grant date. The Company recognized the value of the incentive awards over the remaining four year vesting period which ended in the first quarter of 2018. The Company recorded an insignificant amount of stock based compensation expense in the year ended December 31, 2018 and $0.3 million of stock based compensation expense in the years ended December 31, 2017 and 2016, respectively, pertaining to its incentive awards. Incentive awards outstanding totaled 129,776 as of December 31, 2018 and 2017, respectively. Options Granted to Nonemployees The Company has issued options to purchase shares of common stock to certain scientific advisors and consultants. The stock options have various exercise prices, a term of ten years, and vest over periods up to forty-eight months. The Company granted to these advisors and consultants options to purchase 10,000 and 15,000 shares of common stock, in 2018 and 2017, respectively. As of December 31, 2018, options to purchase 22,793 shares of common stock remained unvested, and under current guidance compensation related to these stock options is subject to remeasurement each reporting period as the shares vest. In 2013, the Company also issued an incentive award for 2,335 shares to a scientific advisor, which was fully vested as of December 31, 2018. The Company recorded $0.1 million of expense in the years ended December 31, 2018 and 2017, respectively, and an insignificant amount in the year ended December 31, 2016, related to these options and awards. Stock-Based Compensation Expense Stock-based compensation expense is included in the consolidated statements of operations and comprehensive loss and is as follows (in thousands): Year Ended December 31, 2018 2017 2016 Research and development $ 2,760 $ 1,301 $ 995 General and administrative 4,253 3,619 1,478 Total stock-based compensation expense $ 7,013 $ 4,920 $ 2,473 Valuation Assumptions The following table presents the weighted-average assumptions the Company used in the Black-Scholes option-pricing model to derive the grant date fair values of stock options and performance-based stock options granted in each of the years presented along with the resulting estimated weighted-average grant date fair values per share: Year Ended December 31, 2018 2017 2016 Expected term Options 6.2 yrs 6.0 yrs 6.1 yrs Performance options — — 5.1 yrs Expected volatility Options 77 % 84 % 80 % Performance options — — 85 % Risk-free interest rate Options 2.62 % 2.15 % 1.57 % Performance options — — 1.56 % Expected dividend yield Options — — — Performance options — — — Weighted-average grant date fair value per share Options $ 8.14 $ 3.36 $ 0.89 Performance options — — 1.20 Expected Term The Company does not believe it can currently place reliance on its historical exercise and post-vesting termination activity to provide accurate data for estimating the expected term. Therefore, for stock option grants made during the years ended December 31, 2018, 2017 and 2016, the Company has opted to use the simplified method for estimating the expected term, which is an average of the contractual term of the options and its ordinary vesting period. The expected term represents the period of time that options are expected to be outstanding. Expected Volatility As the Company has limited trading history for its common stock, the expected stock price volatility for the Company’s common stock was estimated by considering the volatility rates of similar publicly traded peer entities within the life sciences industry. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. Risk-Free Interest Rate The risk-free interest rate assumption was based on U.S. treasury instruments with constant maturities whose term was consistent with the expected term of stock options granted by the Company. Expected Dividend Yield The Company has never declared or paid cash dividends and does not plan to pay cash dividends in the foreseeable future. Consequently, the Company uses an expected dividend yield of zero.

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2018
Postemployment Benefits [Abstract]
401(k) Plan	10. 401(k) Plan The Company provides a qualified 401(k) savings plan for its employees. All employees are eligible to participate, provided they meet the requirements of the plan. As is permitted under the plan, in 2018 the Company elected to match employee contributions up to $750 and accordingly matching contributions totaling an insignificant amount were made in the year ended December 31, 2018. No matching contributions were made in the years ended December 31, 2017 and 2016.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes No provision for U.S. income taxes exists due to tax losses incurred in all periods presented. All losses incurred were U.S. based. Significant components of the Company’s deferred tax assets are as follows (in thousands): December 31 2018 2017 Deferred tax assets: Federal and state net operating loss carryforwards $ 85,571 $ 63,935 Capitalized research and development 10,466 9,455 Federal and state tax credit carryforwards 18,590 13,529 Stock based compensation 2,848 1,493 Other 1,499 438 Total deferred tax assets 118,974 88,850 Deferred tax liabilities: Fixed assets (622 ) - Total deferred tax liabilities (622 ) - Valuation allowance (118,352 ) (88,850 ) Net deferred tax assets $ - $ - On December 22, 2017, the U.S. federal government enacted the Tax Cuts and Jobs Act (Tax Act). The Tax Act contains, among other things, significant changes to corporate taxation, including reduction of the corporate tax rate from a top marginal rate of 35% to a flat rate of 21% for tax years beginning after December 31, 2017, limitation of the deduction for net operating losses to 80% of current year taxable income and elimination of net operating loss carrybacks, implementing a territorial tax system, and requiring a mandatory one-time tax on U.S. owned undistributed foreign earnings and profits known as the transition tax. Pursuant to SAB 118, an entity may select between one of three scenarios to determine a reasonable estimate arising from the Tax Act. The scenarios are (i) a final estimate which effectively closes the measurement window; (ii) a reasonable estimate leaving the measurement window open for future revisions; and (iii) no estimate as the law is still being analyzed. The Company was able to provide a reasonable estimate for the revaluation of deferred taxes. As such, the Company recorded a $38.2 million reduction in deferred tax assets for the revaluation of deferred taxes in 2017 which was offset by a corresponding decrease to the Company’s full valuation allowance. The ultimate impact of the Act did not differ materially from provision amounts recorded. Adjustments, if any, would not have impacted the consolidated statement of operations and comprehensive loss due to the full valuation allowance on the Company’s deferred tax assets. Realization of the net deferred tax assets is dependent upon future taxable income, if any, the amount and timing of which is uncertain. Based on the weight of available positive and negative objective evidence, management believes it more likely than not that the Company’s deferred tax assets are not realizable. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. The net valuation allowance increased by $29.5 million during the year ended December 31, 2018 and decreased by $32.7 million during the year ended December 31, 2017, respectively. The following is a reconciliation of the expected statutory federal income tax provision to the actual income tax provision (in thousands): December 31 2018 2017 2016 Income tax benefit at federal statutory tax rate $ (15,235 ) $ (9,369 ) $ (9,068 ) Change in valuation allowance 29,501 (32,709 ) 9,775 Effect of change in enacted tax rates - 38,194 - State income taxes, net of federal benefit (10,112 ) 5,094 (458 ) Permanent items 563 4,027 196 Research credits (4,717 ) (5,237 ) (445 ) Income tax (benefit) expense $ - $ - $ - Pursuant to Internal Revenue Code (IRC), Section 382 and 383, use of the Company’s U.S. federal and state net operating loss and research and development income tax credit carryforwards may be limited in the event of a cumulative change in ownership of more than 50.0% within a three-year period. The Company completed an analysis under IRC Sections 382 and 383 through December 21, 2007 and determined that the Company’s net operating losses and research and development credits were subject to limitations due to changes in ownership through December 31, 2007. The net operating loss carryforwards reflected in the deferred tax assets at December 31, 2018 have been adjusted to reflect Section 382 limitations resulting from that change. The Company has been in a net operating loss position since 2008. The Company has not performed any additional analysis for IRC Sections 382 and 383 and there is a risk that additional changes in ownership could have occurred since December 31, 2007. If a change in ownership were to have occurred, additional net operating loss and tax credit carryforwards could be eliminated or restricted. If eliminated, the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance. As of December 31, 2018, the Company has federal net operating loss carryforwards of $332.7 million and state net operating loss carryforwards of $224.8 million to offset future taxable income, if any. In addition, the Company has federal research and development tax credit carryforwards of $8.5 million, federal research and development orphan drug tax credit carryforwards of $11.2 million, and state research and development tax credit carryforwards of $4.5 million. If not utilized, the federal net operating loss and tax credit carryforwards for years beginning before January 1, 2018 will expire beginning in 2024 through 2037 and the state net operating loss carryforwards will expire beginning in 2028 through 2038. Under the Act, federal net operating losses for tax years beginning after January 1, 2018 will be carried forward indefinitely, but the deductibility of such federal net operating losses is limited. It is uncertain to what extent various states will conform to the Act with regard to net operating loss carry forwards. The state tax credit will carry forward indefinitely. The following table summarizes activity related to the Company’s gross unrecognized tax benefits (in thousands): Total Balances as of December 31, 2015 $ 2,127 Increases related to prior year tax positions - Increases related to 2016 tax positions 159 Balances as of December 31, 2016 $ 2,286 Increases related to prior year tax positions - Increases related to 2017 tax positions 1,009 Balances as of December 31, 2017 $ 3,295 Increases related to prior year tax positions 6 Increases related to 2018 tax positions 1,283 Balances as of December 31, 2018 $ 4,584 The unrecognized tax benefits, if recognized, would not have an impact on the Company’s effective tax rate assuming the Company continues to maintain a full valuation allowance position. Based on prior year’s operations and experience, the Company does not expect a significant change to its unrecognized tax benefits over the next twelve months. The unrecognized tax benefits may increase or change during the next year for unexpected or unusual items for items that arise in the ordinary course of business. The Company files income tax returns in the U.S. federal and California jurisdictions and is not currently under examination by federal, state, or local taxing authorities for any open tax years. Due to net operating loss carryforwards, all years remain open for income tax examination by tax authorities in the U.S. and states in which the Company files tax returns.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	12. Selected Quarterly Financial Data (Unaudited) The following tables present selected quarterly financial data for the years ended December 31, 2018 and 2017 (in thousands, except per share data). This information has been prepared on the same basis as the audited consolidated financial statements and includes all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the unaudited quarterly results of operations set forth herein: Quarter Ended March 31 June 30 September 30 December 31 2018 Collaboration revenue $ - $ - $ - $ - Total operating expenses 12,850 17,971 21,129 20,555 Net loss (17,005 ) (17,531 ) (18,563 ) (19,449 ) Basic net loss per common share (0.32 ) (0.30 ) (0.31 ) (0.32 ) Diluted net loss per common share $ (0.32 ) $ (0.30 ) $ (0.34 ) $ (0.32 ) Quarter Ended March 31 June 30 September 30 December 31 2017 Collaboration revenue $ 4,793 $ - $ - $ 5,207 Total operating expenses 7,742 7,626 6,394 9,563 Net loss (5,351 ) (8,929 ) (8,234 ) (5,043 ) Basic net loss per common share (0.20 ) (0.31 ) (0.21 ) (0.11 ) Diluted net loss per common share $ (0.20 ) $ (0.31 ) $ (0.21 ) $ (0.11 )

Organization and Description _2

Organization and Description of Business (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Liquidity	Liquidity The Company has incurred net operating losses and negative cash flows from operations since its inception. During the year ended December 31, 2018, the Company incurred a net loss of $72.5 million and used $54.9 million of cash in operations. At December 31, 2018, the Company had an accumulated deficit of $523.1 million. CymaBay expects to incur substantial research and development expenses as it continues to study its product candidates in clinical trials. To date, none of the Company’s product candidates have been approved for marketing and sale, and the Company has not recorded any revenue from product sales. As a result, management expects operating losses to continue in future years. The Company’s ability to achieve profitability is dependent primarily on its ability to successfully develop, acquire or in-license additional product candidates, continue clinical trials for product candidates currently in clinical development, obtain regulatory approvals, and support commercialization activities for partnered product candidates. Products developed by the Company will require approval of the U.S. Food and Drug Administration (FDA) or a foreign regulatory authority prior to commercial sale. The regulatory approval process is expensive, time-consuming, and uncertain, and any denial or delay of approval could have a material adverse effect on the Company. Even if approved, the Company’s products may not achieve market acceptance and will face competition from both generic and branded pharmaceutical products. As of December 31, 2018, the Company had cash, cash equivalents and marketable securities totaling $178.7 million which the Company believes is sufficient to fund the Company’s current operating plan into 2021.
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying consolidated financial statements are comprised of CymaBay and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The Company has no unconsolidated subsidiaries or investments accounted for under the equity method. These consolidated statements have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP), which requires management to make informed estimates and assumptions that impact the amounts and disclosures reported in the consolidated financial statements and accompanying notes. Certain reclassifications have been made to the prior period amounts to conform to the current year presentation. “Accrued clinical trial expenses” and “Other accrued liabilities”, which previously were reported as “Accrued liabilities” on the consolidated balance sheet, are now reported as separate line items. Accounting estimates and assumptions are inherently uncertain. Management bases its estimates on historical experience and on assumptions believed to be reasonable under the circumstances. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Actual results could differ materially from those estimates and assumptions. The Company believes significant judgment is involved in determining and in estimating the valuation of stock-based compensation, accrued clinical expenses, and equity instrument valuations. These estimates form the basis for making judgments about the carrying values of assets and liabilities when these values are not readily apparent from other sources. Estimates are assessed each reporting period and updated to reflect current information and any changes in estimates will generally be reflected in the period first identified.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company’s financial instruments during the periods reported consist of cash and cash equivalents, marketable securities, accounts receivable, prepaid expenses, other current assets, accounts payable, accrued interest payable, accrued expenses, the facility loan, and warrant liabilities. Fair value estimates of these instruments are made at a specific point in time based on relevant market information. These estimates may be subjective in nature and involve uncertainties and matters of significant judgment. The carrying amounts of financial instruments such as cash and cash equivalents, accounts receivable, prepaid expenses, other current assets, accounts payable, accrued expenses, and accrued interest payable approximate the related fair values due to the short maturities of these instruments. Based on prevailing borrowing rates available to the Company for loans with similar terms, the Company believes the fair value of the facility loan at December 31, 2017, considering level 2 inputs, approximated its carrying value. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Assets and liabilities that are measured at fair value are reported using a three-level fair value hierarchy that prioritizes the inputs used to measure fair value. This hierarchy maximizes the use of observable inputs and maximizes the use of unobservable inputs and is as follows: Level 1—Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2—Inputs other than quoted prices in active markets that are observable for the asset or liability, either directly or indirectly. Level 3—Inputs that are significant to the fair value measurement and are unobservable (i.e. supported by little market activity), which requires the reporting entity to develop its own valuation techniques and assumptions. The following tables present the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis using the above input categories (in thousands): As of December 31, 2018 Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds 39,481 - - 39,481 U.S. and foreign commercial paper - 6,469 - 6,469 Total cash equivalents 39,481 6,469 - 45,950 Short-term investments: U.S. and foreign commercial paper - 51,627 - 51,627 U.S. and foreign corporate debt securities - 34,634 - 34,634 Asset-backed securities - 25,472 - 25,472 U.S. treasury securities - 17,936 - 17,936 Total short-term investments - 129,669 - 129,669 Total assets measured at fair value $ 39,481 $ 136,138 $ — $ 175,619 As of December 31, 2017 Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds 12,822 - - 12,822 U.S. commercial paper - 6,035 - 6,035 Total cash equivalents 12,822 6,035 - 18,857 Short-term investments: U.S. and foreign commercial paper - 35,886 - 35,886 U.S. and foreign corporate debt securities - 19,760 - 19,760 Asset-backed securities - 11,060 - 11,060 U.S. treasury securities - 7,450 - 7,450 Total short-term investments - 74,156 - 74,156 Total assets measured at fair value 12,822 80,191 - 93,013 Warrant liability - - 6,091 6,091 Total liabilities measured at fair value - - 6,091 6,091 The Company estimates the fair value of its corporate debt, asset backed securities, and U.S. treasury securities by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. There were no transfers between Level 1 and Level 2 during the periods presented. Historically, the Company held a Level 3 liability associated with common stock warrants that were issued in connection with the Company’s financings completed in September and October 2013, January 2014, and August 2015. The warrants were accounted for as liabilities until either they were exercised or expired in September 2018. The Company used a binomial option pricing model to value its warrant liabilities prior to September 2017. The inputs for the binomial model are similar to the Black-Scholes model but also incorporate other more complex inputs that, in the Company’s case, included the expected timing, probability and valuation impact of certain potential strategic events. In September 2017, the Company changed its valuation technique and began to value its warrant liability using a Black-Scholes option pricing model, the inputs for which include: exercise price of the warrants, market price of the underlying common shares, dividend yield, expected term, expected volatility, and a risk-free interest rate. Changes to any of these inputs can have a significant impact on the estimated fair value of the warrants. The following tables set forth a summary of the changes in the fair value of the Company’s liabilities measured using Level 3 inputs (in thousands): Year Ended December 31, 2018 2017 Balance, beginning of period $ 6,091 $ 1,145 Change in fair value 3,710 5,773 Settlement of financial instruments (9,379 ) (827 ) Extinguishment of financial instruments (422 ) — Balance, end of period $ - $ 6,091
Cash, Cash Equivalents, and Marketable Securities	Cash, Cash Equivalents, and Marketable Securities The Company considers all highly liquid investments with a remaining maturity of 90 days or less at the time of purchase to be cash equivalents. Cash and cash equivalents consist of deposits with commercial banks in checking, interest-bearing, demand money market accounts and commercial paper. The Company invests excess cash in marketable securities with high credit ratings that are classified in Level 1 and Level 2 of the fair value hierarchy. These securities consist primarily of corporate debt, commercial paper, asset-backed securities, and U.S. treasury securities and are classified as “available-for-sale.” The Company considers marketable securities as short-term investments if the maturity date is less than or equal to one year from the balance sheet date. The Company considers marketable securities as long-term investments if the maturity date is in excess of one year of the balance sheet date. Realized gains and losses from the sale of marketable securities, if any, are calculated using the specific-identification method. Realized gains and losses and declines in value judged to be other-than- temporary are included in interest income or expense in the consolidated statements of operations and comprehensive loss. Unrealized holding gains and losses are reported in accumulated other comprehensive loss in the consolidated balance sheets. To date, the Company has not recorded any impairment charges on its marketable securities related to other-than-temporary declines in market value. In determining whether a decline in market value is other-than-temporary, various factors are considered, including the cause, duration of time and severity of the impairment, any adverse changes in the investees’ financial condition, and the Company’s intent and ability to hold the security for a period of time sufficient to allow for an anticipated recovery in market value.
Concentration of Credit Risk	Concentration of Credit Risk Cash, cash equivalents, and marketable securities consist of financial instruments that potentially subject the Company to a concentration of credit risk to the extent of the fair value recorded in the balance sheet. The Company invests cash that is not required for immediate operating needs primarily in highly liquid instruments that bear minimal risk. The Company has established guidelines relating to the quality, diversification, and maturities of securities to enable the Company to manage its credit risk. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents and investments and issuers of investments to the extent recorded on the consolidated balance sheets. Certain materials and key components that the Company utilizes in its operations are obtained through single suppliers. Since the suppliers of key components and materials must be named in a NDA filed with the FDA for a product, significant delays can occur if the qualification of a new supplier is required. If delivery of material from the Company’s suppliers were interrupted for any reason, the Company may be unable to supply any of its product candidates for clinical trials.
Property and Equipment	Property and Equipment Property and equipment is recorded at cost, less accumulated depreciation and amortization. Depreciation and amortization is calculated using the straight-line method, and the cost is amortized over the estimated useful lives of the respective assets, generally three to seven years. Leasehold improvements are amortized over the shorter of the useful lives or the non-cancelable term of the related lease. Maintenance and repair costs are charged as expense in the consolidated statements of operations and comprehensive loss as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment loss is recognized if the estimated undiscounted future cash flow expected to result from the use and eventual disposition of an asset is less than the carrying amount. While the Company’s current and historical operating losses and cash flows are indicators of impairment, the Company believes the future cash flows to be received support the carrying value of its long-lived assets. Accordingly, the Company has not recognized any impairment losses for the years ended December 31, 2018, 2017 or 2016.
Leases	Leases The Company leases office space under a non-cancelable operating lease agreement and recognizes related rent expense on a straight-line basis over the term of the lease. Incentives granted under the Company’s office lease, including allowances for leasehold improvements and rent holidays, are recognized as reductions to rental expense on a straight-line basis over the term of the lease. The Company does not assume renewals in its determination of the lease term unless they are deemed to be reasonably assured at the inception of the lease and begins recognizing rent expense on the date that it obtains the legal right to use and control the leased space. Deferred rent consists of the difference between cash payments and the rent expense recognized.
Revenue Recognition	Revenue Recognition At the inception of an arrangement, the Company evaluates if a counterparty to a contract is a customer, if the arrangement is within the scope of revenue from contracts with customers guidance, and the term of the contract. The Company recognizes revenue when its customer obtains control of promised goods or services in a contract for an amount that reflects the consideration the Company expects to receive in exchange for those goods or services. For contracts with customers, the Company applies the following five-step model in order to determine this amount: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. As part of the accounting for contracts with customers, the Company must develop assumptions that require judgment to determine the standalone selling price of each performance obligation identified in the contract. The Company then allocates the total transaction price to each performance obligation based on the estimated standalone selling prices of each performance obligation. The Company recognizes the amount of the transaction price as revenue that is allocated to the respective performance obligation when the performance obligation is satisfied or as it is satisfied. Generally, the Company's performance obligations are transferred to customers at a point in time, typically upon delivery. The Company enters into collaboration arrangements, under which it licenses certain rights to its intellectual property to third parties. The terms of these agreements may include payment to the Company of one or more of the following: nonrefundable, upfront license fees; development and commercial milestone payments; funding of research and/or development activities; and royalties on net sales of licensed products. Revenues that result from these payments are classified as collaborative revenues except for royalties on net sales of licensed products, which are classified as royalty revenues. For each collaboration agreement that results in revenues, the Company identifies all material promised goods and services, which may include one or more of the following: a license to intellectual property and know-how, research and development services, and other transition support services. Promised goods or services are considered to be separate performance obligations if they are distinct. To determine the transaction price to be allocated to each performance obligation, in addition to any upfront payment, the Company estimates the amount of variable consideration at the outset of the contract either utilizing the expected value or most likely amount method, depending on the facts and circumstances relative to the contract. The Company constrains (reduces) the estimates of variable consideration such that it is probable that a significant reversal of previously recognized revenue, deferred revenue, or other amounts will not occur in future reporting periods. When determining if variable consideration should be constrained, management considers whether there are factors outside the Company’s control that increase the likelihood of a significant reversal of previously recognized revenue and revenue-related amounts in future reporting periods. These estimates are re-assessed each reporting period as necessary depending on the facts and circumstances of each contract. Once the estimated transaction price is established, amounts are allocated to identified performance obligations. The transaction price is generally allocated to each separate performance obligation on a relative standalone selling price (SSP) basis. The Company must develop assumptions that require judgment to determine the SSP to account for these agreements. To determine the SSP the Company’s assumptions may include (i) assumptions regarding the probability of obtaining marketing approval for the drug candidate, (ii) estimates regarding the timing of and the expected costs to develop and commercialize the drug candidate, (iii) estimates of future cash flows from potential product sales with respect to the drug candidate and (iv) appropriate discount and tax rates. SSPs used to perform the initial allocation are not updated after contract inception. The Company does not include a financing component to its estimated transaction price at contract inception unless it estimates that certain performance obligations will not be satisfied within one year. Upfront License Fees: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from nonrefundable, upfront license fees based on the relative value prescribed to the license compared to the total value of the arrangement. The revenue is recognized when the license is transferred to the collaborator and the collaborator is able to use and benefit from the license. For licenses that are not distinct from other obligations identified in the arrangement, 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. If the combined performance obligation is satisfied over time, the Company applies an appropriate method of measuring progress for purposes of recognizing revenue from nonrefundable, upfront license fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Development and Regulatory Milestone Payments : Depending on facts and circumstances, the Company may conclude that it is appropriate to include the milestone in the estimated transaction price using the most likely amount method or that it is appropriate to fully constrain the milestone. A milestone payment is included in the transaction price in the reporting period that the Company concludes that it is probable that recording revenue in the period will not result in a significant reversal in amounts recognized in future periods. The Company may record revenues from certain milestones in a reporting period before the milestone is achieved if the Company concludes that achievement of the milestone is probable and that recognition of revenue related to the milestone will not result in a significant reversal in amounts recognized in future periods. The Company records a corresponding contract asset when this conclusion is reached. Until that determination is made, milestone payments that have not been included in the transaction price to date are fully constrained. The Company re-evaluates the probability of achievement of such development milestones and any related constraint each reporting period. The Company adjusts its estimate of the overall transaction price, including the amount of collaborative revenue that it has recorded, if necessary. Sales-based Milestone and Royalty Payments: The Company’s collaborators may be required to pay the Company sales-based milestone payments or royalties on future sales of commercial products. The Company recognizes revenues related to sales-based milestone and royalty payments upon the later to occur of (i) achievement of the collaborator’s underlying sales or (ii) satisfaction of any performance obligation(s) related to these sales, in each case assuming the license to the Company’s intellectual property is deemed to be the predominant item to which the sales-based milestones and/or royalties relate.
Research and Development Expenses	Research and Development Expenses Research and development expenses consist of costs incurred in identifying, developing, and testing product candidates. These expenses consist primarily of costs for research and development personnel, including related stock-based compensation; contract research organizations (CRO) and other third parties that assist in managing, monitoring, and analyzing clinical trials; investigator and site fees; laboratory services; consultants; contract manufacturing services; non-clinical studies, including materials; and allocated expenses, such as depreciation of assets, and facilities and information technology that support research and development activities. Research and development costs are expensed as incurred, including expenses that may or may not be reimbursed under research and development funding arrangements. Payments made prior to the receipt of goods or services to be used in research and development are recorded as prepaid assets until the goods are received or services are rendered. Such payments are evaluated for current or long term classification based on when they will be realized. The Company records expenses related to clinical studies and manufacturing development activities based on its estimates of the services received and efforts expended pursuant to contracts with multiple CROs and manufacturing vendors that conduct and manage these activities on its behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract, and may result in uneven payment flows. There may be instances in which payments made to the Company’s vendors will exceed the level of services provided and result in a prepayment of the expense. Payments under some of these contracts depend on factors such as the successful enrollment of subjects and the completion of clinical trial milestones. In amortizing or accruing service fees, the Company estimates the time period over which services will be performed, enrollment of subjects, number of sites activated and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the Company’s estimate, the Company will adjust the accrued or prepaid expense balance accordingly. To date, there have been no material differences from the Company’s estimates to the amounts actually incurred.
Stock-Based Compensation	Stock-Based Compensation Employee and director stock-based compensation is measured at fair value on the grant date of the award. Compensation cost is recognized as expense on a straight-line basis over the vesting period for options and on an accelerated basis for stock options with performance conditions, net of estimated forfeitures. For stock options with performance conditions, the Company evaluates the probability of achieving performance conditions at each reporting date. The Company begins to recognize the expense when it is deemed probable that the performance conditions will be met. The Company uses the Black-Scholes option pricing model to determine the fair value of stock option awards. The determination of fair value for stock-based awards using an option-pricing model requires management to make certain assumptions regarding subjective input variables such as expected term, dividends, volatility and risk-free rate. The Company is also required to make estimates as to the probability of achieving the specific performance criteria. If actual results are not consistent with the Company’s assumptions and judgments used in making these estimates, the Company may be required to increase or decrease compensation expense, which could be material to the Company’s results of operations. Equity awards granted to non-employees are valued using the Black-Scholes option pricing model. Stock-based compensation expense for nonemployee services is subject to remeasurement as the underlying equity instruments vest and is recognized as an expense over the period during which services are received.
Common Stock Warrant Liabilities	Common Stock Warrant Liabilities Historically, the Company’s outstanding common stock warrants issued in connection with certain equity and debt financings that occurred in 2013 through 2015 were classified as liabilities in the accompanying consolidated balance sheets because of certain contractual terms that preclude equity classification. All outstanding warrants related to these financings had been exercised or had expired by September 30, 2018. Upon expiration, the remaining fair value of the liability was extinguished and credited to other (expense) income, net in the Company’s consolidated statement of operations. Prior to expiration, the Company estimated the fair value of common stock warrants at each reporting period until the exercise of the warrants, at which time the liability was revalued and reclassified to stockholders’ equity. The determination of fair value of these common stock warrants required management to make certain assumptions regarding subjective input variables such as timing, probability and valuation impact of certain potential strategic events, expected term, dividends, expected volatility and risk-free interest rates.
Income Taxes	Income Taxes The Company utilizes the liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between the financial reporting and the tax bases of assets and liabilities and are measured using enacted tax rates and laws that will be in effect when the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. A valuation allowance is recorded when it is more likely than not that all or part of a deferred tax asset will not be realized. When the Company establishes or reduces the valuation allowance related to the deferred tax assets, the provision for income taxes will increase or decrease, respectively, in the period such determination is made. The accounting guidance for uncertainty in income taxes prescribes a recognition threshold and measurement attribute criteria for the financial 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 based on the technical merits of the position. The Company is required to file federal and state income tax returns in the United States. The preparation of these income tax returns requires the Company to interpret the applicable tax laws and regulations in effect that could affect the amount of tax paid to these jurisdictions. In December 2017, Securities and Exchange Commission (SEC) staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act The Company records interest related to income tax reserves, if any, as interest expense, and any penalties would be recorded as other expense in the consolidated statements of operations and comprehensive loss. There was no interest or penalties related to income tax reserves during the years ended December 31, 2018, 2017 and 2016.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss and net unrealized gains and losses on marketable securities, which are presented in a single continuous statement. Other comprehensive (loss) gain is also disclosed in the consolidated balance sheets and statements of stockholders’ equity in accumulated other comprehensive loss, and is stated net of related tax effects, if any.
Net Loss Per Common Share	Net Loss Per Common Share Basic net loss per share of common stock is based on the weighted average number of shares of common stock outstanding equivalents during the period. Diluted net loss per share of common stock is calculated as the weighted average number of shares of common stock outstanding adjusted to include the assumed exercises of stock options and common stock warrants, if dilutive. The calculation of diluted loss per share also requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of the common stock warrants and the presumed exercise of such securities are dilutive to earnings (loss) per share for the period, adjustments to net income or net loss used in the calculation are required to remove the change in fair value of the common stock warrant liability for the period. Likewise, adjustments to the denominator are required to reflect the related dilutive shares. In all periods presented, the Company’s outstanding stock options were excluded from the calculation of net loss per share because the effect would be antidilutive. The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share amounts): Year Ended December 31, 2018 2017 2016 Numerator: Net loss allocated to common stock—basic $ (72,548 ) $ (27,557 ) $ (26,671 ) Adjustment for revaluation and extinguishment of common stock warrants (422 ) - - Net loss allocated to common stock—diluted $ (72,970 ) $ (27,557 ) $ (26,671 ) Denominator: Weighted average number of common stock shares outstanding - basic 57,808,254 34,903,960 23,447,003 Dilutive securities: Common stock warrants 30,045 - - Weighted average number of common stock shares outstanding - diluted 57,838,299 34,903,960 23,447,003 Net loss per share—basic $ (1.25 ) $ (0.79 ) $ (1.14 ) Net loss per share—diluted $ (1.26 ) $ (0.79 ) $ (1.14 ) The following table shows the total outstanding securities considered anti-dilutive and therefore excluded from the computation of diluted net loss per share (in thousands): Year Ended December 31, 2018 2017 2016 Common stock warrants - 1,461 1,667 Common stock options 5,593 4,356 2,721 Incentive awards 130 130 239 Total 5,723 5,947 4,627
Recently Adopted and Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements Accounting Standards Update 2014-09 On January 1, 2018, the Company adopted ASU No. 2014-09, Revenue from Contracts with Customers Accounting Standards Update 2017-09 In May 2017, the Financial Accounting Standards Board (FASB) issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718) - Scope of Modification Accounting Accounting Standards Update 2016-15 In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230: Classification of Certain Cash Receipts and Cash Payments) SEC Securities Act Release No. 33-10532 In August 2018, the SEC adopted amendments to certain disclosure requirements in Securities Act Release No. 33-10532, Disclosure Update and Simplification Recently Issued Accounting Pronouncements standard can be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company is currently evaluating the impact of adoption on its consolidated financial statements. Accounting Standards Update 2018-13 In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework – Accounting Standards Update 2018-08 In June 2018, the FASB issued ASU No. 2018-08, Not-For-Profit Entities (Topic 958): Clarifying the Scope and the Accounting Guidance for Contributions Received and Contributions Made, which is intended to clarify and improve the scope and the accounting guidance for contributions received and contributions made. The amendments in ASU No. 2018-08 should assist entities in (1) evaluating whether transactions should be accounted for as contributions (nonreciprocal transaction) within the scope of Topic 958, Not-for-Profit Entities, or as exchange (reciprocal) transactions subject to other guidance and (2) determining whether a contribution is conditional. This amendment applies to all entities that make or receive grants or contributions. This ASU is effective for public companies serving as resource providers for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. The Company will adopt this standard on January 1, 2019 and does not expect it will have a material impact on the Company’s consolidated financial statements. Accounting Standards Update 2018-07 Compensation – Stock Compensation – Accounting Standards Update 2016-02 and 2018-11 In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The Company will adopt this standard on January 1, 2019 using the modified retrospective approach with a cumulative effect adjustment to accumulated deficit at the beginning of the period of adoption. The Company will also adopt certain practical expedients provided by ASU 2018-11. The standard will have a material impact due to the recognition of right of use (ROU) assets and lease liabilities on the Company’s consolidated balance sheets, but it is not expected to have a material impact on the Company’s consolidated income statements. Adoption of the standard will result in the recognition of additional ROU assets and lease liabilities of $0.2 million and $2.5 million, respectively, and the derecognition of the deferred rent balance of $2.3 million as of January 1, 2019.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis	The following tables present the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis using the above input categories (in thousands): As of December 31, 2018 Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds 39,481 - - 39,481 U.S. and foreign commercial paper - 6,469 - 6,469 Total cash equivalents 39,481 6,469 - 45,950 Short-term investments: U.S. and foreign commercial paper - 51,627 - 51,627 U.S. and foreign corporate debt securities - 34,634 - 34,634 Asset-backed securities - 25,472 - 25,472 U.S. treasury securities - 17,936 - 17,936 Total short-term investments - 129,669 - 129,669 Total assets measured at fair value $ 39,481 $ 136,138 $ — $ 175,619 As of December 31, 2017 Level 1 Level 2 Level 3 Fair Value Cash equivalents: Money market funds 12,822 - - 12,822 U.S. commercial paper - 6,035 - 6,035 Total cash equivalents 12,822 6,035 - 18,857 Short-term investments: U.S. and foreign commercial paper - 35,886 - 35,886 U.S. and foreign corporate debt securities - 19,760 - 19,760 Asset-backed securities - 11,060 - 11,060 U.S. treasury securities - 7,450 - 7,450 Total short-term investments - 74,156 - 74,156 Total assets measured at fair value 12,822 80,191 - 93,013 Warrant liability - - 6,091 6,091 Total liabilities measured at fair value - - 6,091 6,091
Schedule of Changes in Fair Value of Liabilities	The following tables set forth a summary of the changes in the fair value of the Company’s liabilities measured using Level 3 inputs (in thousands): Year Ended December 31, 2018 2017 Balance, beginning of period $ 6,091 $ 1,145 Change in fair value 3,710 5,773 Settlement of financial instruments (9,379 ) (827 ) Extinguishment of financial instruments (422 ) — Balance, end of period $ - $ 6,091
Computation of Basic and Diluted Net Loss per Share	The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share amounts): Year Ended December 31, 2018 2017 2016 Numerator: Net loss allocated to common stock—basic $ (72,548 ) $ (27,557 ) $ (26,671 ) Adjustment for revaluation and extinguishment of common stock warrants (422 ) - - Net loss allocated to common stock—diluted $ (72,970 ) $ (27,557 ) $ (26,671 ) Denominator: Weighted average number of common stock shares outstanding - basic 57,808,254 34,903,960 23,447,003 Dilutive securities: Common stock warrants 30,045 - - Weighted average number of common stock shares outstanding - diluted 57,838,299 34,903,960 23,447,003 Net loss per share—basic $ (1.25 ) $ (0.79 ) $ (1.14 ) Net loss per share—diluted $ (1.26 ) $ (0.79 ) $ (1.14 )
Anti-Dilutive Securities Excluded from the Computation of Diluted Net Loss per Share	The following table shows the total outstanding securities considered anti-dilutive and therefore excluded from the computation of diluted net loss per share (in thousands): Year Ended December 31, 2018 2017 2016 Common stock warrants - 1,461 1,667 Common stock options 5,593 4,356 2,721 Incentive awards 130 130 239 Total 5,723 5,947 4,627

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2018
Cash And Cash Equivalents [Abstract]
Marketable Available-for-Sale Securities	Marketable available-for-sale securities as of December 31, 2018 and 2017 consist of the following (in thousands): Gross Gross Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value As of December 31, 2018: U.S. and foreign commercial paper $ 51,627 $ - $ - $ 51,627 U.S. and foreign corporate debt securities 34,668 - (34 ) 34,634 Asset-backed securities 25,494 - (22 ) 25,472 U.S. treasury securities 17,938 - (2 ) 17,936 $ 129,727 $ - $ (58 ) $ 129,669 Gross Gross Amortized Unrealized Unrealized Estimated Cost Gains Losses Fair Value As of December 31, 2017: U.S. and foreign commercial paper $ 35,886 $ - $ - $ 35,886 U.S. and foreign corporate debt securities 19,785 - (25 ) 19,760 Asset-backed securities 11,070 - (10 ) 11,060 U.S. treasury securities 7,459 - (9 ) 7,450 $ 74,200 $ - $ (44 ) $ 74,156

Certain Balance Sheet Items (Ta

Certain Balance Sheet Items (Tables)	12 Months Ended
	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Property and Equipment	Property and equipment consist of the following (in thousands): December 31, 2018 2017 Leasehold improvements $ 2,417 $ 65 Office and computer equipment 214 177 Purchased software 44 83 Furniture and fixtures 360 65 Total 3,035 390 Less accumulated depreciation and amortization (130 ) (321 ) Property and equipment, net $ 2,905 $ 69
Other Accrued Liabilities	Other accrued liabilities consist of the following (in thousands): December 31, 2018 2017 Accrued compensation $ 2,759 $ 2,416 Accrued professional fees and other 670 399 Deferred rent 425 13 Total other accrued liabilities $ 3,854 $ 2,828

Collaboration and License Agr_2

Collaboration and License Agreements (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue From Contract With Customer [Abstract]
Accounts Receivable from the Kowa Contract	There were no contract assets or deferred revenues (contract liabilities) recorded during the year ended December 31, 2018. Accounts receivable from the Kowa contract consisted of the following (in thousands): December 31, 2018 2017 Accounts Receivable $ - $ 5,000

Facility Loans (Tables)

Facility Loans (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Term Loan Facility, Debt Discounts and Final Payment	The term loan facility, debt discounts and final payment balances as of December 31, 2018 and 2017 are as follows (in thousands): December 31, 2018 2017 Principal payments due under the loan facility $ - $ 5,877 Less: unamortized debt discount - (296 ) Plus: accreted value of final payment - 517 Term loan facility, net $ - $ 6,098

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Rent Payments	Future minimum rent payments under noncancelable operating lease commitments are as follows (in thousands): Lease Payments Year ending December 31: 2019 $ 628 2020 647 2021 666 2022 687 2023 707 Thereafter 30 Total future minimum lease payments $ 3,365

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Reserved Shares of Authorized but Unissued Common Stock	As of December 31, 2018 and 2017, the Company had reserved shares of authorized but unissued common stock as follows: December 31, 2018 2017 Common stock warrants - 1,460,955 Equity incentive plan 6,991,570 4,021,983 Total reserved shares of common stock 6,991,570 5,482,938

Stock Plan and Stock-Based Co_2

Stock Plan and Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Grants, Including Performance Options	The following table summarizes activity in the Company’s stock option grants, including performance options: Shares Subject to Outstanding Options Weighted Average Exercise Price of Options Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2017 4,356,441 $ 5.15 Options granted 2,167,272 11.84 Options exercised (750,852 ) 4.76 Options forfeited (179,729 ) 8.81 Outstanding as of December 31, 2018 5,593,132 $ 7.68 8.04 $ 11,096 Vested and expected to vest as of December 31, 2018 5,593,132 7.68 8.04 11,096 Exercisable as of December 31, 2018 2,627,819 $ 5.65 7.07 $ 7,799
Summary of Stock-Based Compensation Expense	Stock-based compensation expense is included in the consolidated statements of operations and comprehensive loss and is as follows (in thousands): Year Ended December 31, 2018 2017 2016 Research and development $ 2,760 $ 1,301 $ 995 General and administrative 4,253 3,619 1,478 Total stock-based compensation expense $ 7,013 $ 4,920 $ 2,473
Estimated Weighted-Average Grant Date Fair Value	The following table presents the weighted-average assumptions the Company used in the Black-Scholes option-pricing model to derive the grant date fair values of stock options and performance-based stock options granted in each of the years presented along with the resulting estimated weighted-average grant date fair values per share: Year Ended December 31, 2018 2017 2016 Expected term Options 6.2 yrs 6.0 yrs 6.1 yrs Performance options — — 5.1 yrs Expected volatility Options 77 % 84 % 80 % Performance options — — 85 % Risk-free interest rate Options 2.62 % 2.15 % 1.57 % Performance options — — 1.56 % Expected dividend yield Options — — — Performance options — — — Weighted-average grant date fair value per share Options $ 8.14 $ 3.36 $ 0.89 Performance options — — 1.20

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Components of Deferred Tax Assets	Significant components of the Company’s deferred tax assets are as follows (in thousands): December 31 2018 2017 Deferred tax assets: Federal and state net operating loss carryforwards $ 85,571 $ 63,935 Capitalized research and development 10,466 9,455 Federal and state tax credit carryforwards 18,590 13,529 Stock based compensation 2,848 1,493 Other 1,499 438 Total deferred tax assets 118,974 88,850 Deferred tax liabilities: Fixed assets (622 ) - Total deferred tax liabilities (622 ) - Valuation allowance (118,352 ) (88,850 ) Net deferred tax assets $ - $ -
Summary of Reconciliation of Expected Statutory Federal Income Tax Provision to Actual Income Tax Provision	The following is a reconciliation of the expected statutory federal income tax provision to the actual income tax provision (in thousands): December 31 2018 2017 2016 Income tax benefit at federal statutory tax rate $ (15,235 ) $ (9,369 ) $ (9,068 ) Change in valuation allowance 29,501 (32,709 ) 9,775 Effect of change in enacted tax rates - 38,194 - State income taxes, net of federal benefit (10,112 ) 5,094 (458 ) Permanent items 563 4,027 196 Research credits (4,717 ) (5,237 ) (445 ) Income tax (benefit) expense $ - $ - $ -
Summary of Gross Unrecognized Tax Benefits	The following table summarizes activity related to the Company’s gross unrecognized tax benefits (in thousands): Total Balances as of December 31, 2015 $ 2,127 Increases related to prior year tax positions - Increases related to 2016 tax positions 159 Balances as of December 31, 2016 $ 2,286 Increases related to prior year tax positions - Increases related to 2017 tax positions 1,009 Balances as of December 31, 2017 $ 3,295 Increases related to prior year tax positions 6 Increases related to 2018 tax positions 1,283 Balances as of December 31, 2018 $ 4,584

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) - (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Data	The following tables present selected quarterly financial data for the years ended December 31, 2018 and 2017 (in thousands, except per share data). This information has been prepared on the same basis as the audited consolidated financial statements and includes all adjustments (consisting only of normal recurring adjustments) necessary to present fairly the unaudited quarterly results of operations set forth herein: Quarter Ended March 31 June 30 September 30 December 31 2018 Collaboration revenue $ - $ - $ - $ - Total operating expenses 12,850 17,971 21,129 20,555 Net loss (17,005 ) (17,531 ) (18,563 ) (19,449 ) Basic net loss per common share (0.32 ) (0.30 ) (0.31 ) (0.32 ) Diluted net loss per common share $ (0.32 ) $ (0.30 ) $ (0.34 ) $ (0.32 ) Quarter Ended March 31 June 30 September 30 December 31 2017 Collaboration revenue $ 4,793 $ - $ - $ 5,207 Total operating expenses 7,742 7,626 6,394 9,563 Net loss (5,351 ) (8,929 ) (8,234 ) (5,043 ) Basic net loss per common share (0.20 ) (0.31 ) (0.21 ) (0.11 ) Diluted net loss per common share $ (0.20 ) $ (0.31 ) $ (0.21 ) $ (0.11 )

Organization and Description _3

Organization and Description of Business - Additional Information (Detail) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018USD ($)	Sep. 30, 2018USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2018USD ($)Segment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of operating segments | Segment									1
Net loss	$ (19,449)	$ (18,563)	$ (17,531)	$ (17,005)	$ (5,043)	$ (8,234)	$ (8,929)	$ (5,351)	$ (72,548)	$ (27,557)	$ (26,671)
Cash flows from operating activities									(54,936)	(19,632)	$ (23,353)
Accumulated deficit	(523,064)				$ (450,516)				(523,064)	$ (450,516)
Cash and cash equivalents and marketable securities	$ 178,700								$ 178,700

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 175,619	$ 93,013
Total liabilities measured at fair value		6,091
Warrant Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value		6,091
Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	45,950	18,857
Cash Equivalents [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	39,481	12,822
Cash Equivalents [Member] | U.S. and Foreign Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	6,469	6,035
Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	129,669	74,156
Short-term Investments [Member] | U.S. and Foreign Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	51,627	35,886
Short-term Investments [Member] | U.S. and Foreign Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	34,634	19,760
Short-term Investments [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	25,472	11,060
Short-term Investments [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	17,936	7,450
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	39,481	12,822
Level 1 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	39,481	12,822
Level 1 [Member] | Cash Equivalents [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	39,481	12,822
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	136,138	80,191
Level 2 [Member] | Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	6,469	6,035
Level 2 [Member] | Cash Equivalents [Member] | U.S. and Foreign Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	6,469	6,035
Level 2 [Member] | Short-term Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	129,669	74,156
Level 2 [Member] | Short-term Investments [Member] | U.S. and Foreign Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	51,627	35,886
Level 2 [Member] | Short-term Investments [Member] | U.S. and Foreign Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	34,634	19,760
Level 2 [Member] | Short-term Investments [Member] | Asset-backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	25,472	11,060
Level 2 [Member] | Short-term Investments [Member] | U.S. Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured at fair value	$ 17,936	7,450
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value		6,091
Level 3 [Member] | Warrant Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured at fair value		$ 6,091

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Product Information [Line Items]
Warrants exercise or expiration period		Sep. 30, 2018
Cash and cash equivalents, maturity description		90 days or less
Impairment losses		$ 0	$ 0	$ 0
Interest or penalties related to income taxes		$ 0	$ 0	$ 0
Subsequent Event [Member] | ASU 2018-11 [Member]
Product Information [Line Items]
ROU assets	$ 200,000
Lease liabilities	2,500,000
Derecognition of the deferred rent	$ 2,300,000
Maximum [Member]
Product Information [Line Items]
Short-term contractual maturities		1 year
Property and equipment, estimated useful lives		7 years
Minimum [Member]
Product Information [Line Items]
Long-term contractual maturities		1 year
Property and equipment, estimated useful lives		3 years

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Changes in Fair Value of Liabilities (Detail) - Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of period	$ 6,091	$ 1,145
Change in fair value	3,710	5,773
Settlement of financial instruments	(9,379)	(827)
Extinguishment of financial instruments	$ (422)
Balance, end of period		$ 6,091

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Computation of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerator:
Net loss allocated to common stock—basic									$ (72,548)	$ (27,557)	$ (26,671)
Adjustment for revaluation and extinguishment of common stock warrants									(422)
Net loss allocated to common stock—diluted									$ (72,970)	$ (27,557)	$ (26,671)
Denominator:
Weighted average number of common stock shares outstanding - basic									57,808,254	34,903,960	23,447,003
Dilutive securities:
Common stock warrants									30,045
Weighted average number of common stock shares outstanding - diluted									57,838,299	34,903,960	23,447,003
Net loss per share—basic	$ (0.32)	$ (0.31)	$ (0.30)	$ (0.32)	$ (0.11)	$ (0.21)	$ (0.31)	$ (0.20)	$ (1.25)	$ (0.79)	$ (1.14)
Net loss per share—diluted	$ (0.32)	$ (0.34)	$ (0.30)	$ (0.32)	$ (0.11)	$ (0.21)	$ (0.31)	$ (0.20)	$ (1.26)	$ (0.79)	$ (1.14)

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Anti-Dilutive Securities Excluded from the Computation of Diluted Net Loss per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	5,723	5,947	4,627
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share		1,461	1,667
Common Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	5,593	4,356	2,721
Incentive Awards [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the computation of diluted loss per share	130	130	239

Marketable Securities - Marketa

Marketable Securities - Marketable Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 129,727	$ 74,200
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(58)	(44)
Estimated Fair Value	129,669	74,156
U.S. and Foreign Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	51,627	35,886
Estimated Fair Value	51,627	35,886
U.S. and Foreign Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	34,668	19,785
Gross Unrealized Losses	(34)	(25)
Estimated Fair Value	34,634	19,760
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25,494	11,070
Gross Unrealized Gains	0
Gross Unrealized Losses	(22)	(10)
Estimated Fair Value	25,472	11,060
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	17,938	7,459
Gross Unrealized Gains	0
Gross Unrealized Losses	(2)	(9)
Estimated Fair Value	$ 17,936	$ 7,450

Marketable Securities - Additio

Marketable Securities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Asset-backed Securities [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Remaining contractual maturities of marketable securities	1 year	1 year
U.S. and Foreign Commercial Paper [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Remaining contractual maturities of marketable securities	1 year	1 year
U.S. and Foreign Corporate Debt Securities [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Remaining contractual maturities of marketable securities	1 year	1 year
U.S. Treasury Securities [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Remaining contractual maturities of marketable securities	1 year	1 year
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Realized gains and losses	$ 0	$ 0	$ 0
Marketable investments continuous unrealized loss position	$ 0	$ 0

Certain Balance Sheet Items - P

Certain Balance Sheet Items - Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 3,035	$ 390
Less accumulated depreciation and amortization	(130)	(321)
Property and equipment, net	2,905	69
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,417	65
Office and Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	214	177
Purchased Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	44	83
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 360	$ 65

Certain Balance Sheet Items - O

Certain Balance Sheet Items - Other Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Accrued compensation	$ 2,759	$ 2,416
Accrued professional fees and other	670	399
Deferred rent	425	13
Total other accrued liabilities	$ 3,854	$ 2,828

Collaboration and License Agr_3

Collaboration and License Agreements - Additional Information (Detail)	1 Months Ended			3 Months Ended	12 Months Ended
	Jun. 30, 2010Agreement	Jun. 30, 2006	Jun. 30, 1998USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Jan. 01, 2018USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Transaction price allocated to performance obligations								$ 10,000,000
Contract assets					$ 0
Contract liabilities					0
Contract Initiation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Transaction price allocated to performance obligations								5,000,000
License [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Transaction price allocated to performance obligations								9,500,000
Arhalofenate Product [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Transaction price allocated to performance obligations								400,000
Research and Pre Clinical Development Services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Transaction price allocated to performance obligations								100,000
Pharmacokinetics of Arhalofenate [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Transaction price allocated to performance obligations								$ 5,000,000
Kowa Pharmaceuticals America Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable upfront payment				$ 5,000,000
Kowa Pharmaceuticals America Inc [Member] | Pharmacokinetics of Arhalofenate [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments				5,000,000
Kowa Pharmaceuticals America Inc [Member] | Achievement of Other Specific Development and Sales [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments				190,000,000
Kowa Pharmaceuticals America Inc [Member] | Phase 3 Study [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments				5,000,000
Janssen Pharmaceutical NV [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty payment					0	$ 0	$ 0
Accrued royalties				$ 0	0	0	0
Janssen Pharmaceutical NV [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of royalty on net sales		8.00%
Janssen Pharmaceuticals, Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of development and license agreements | Agreement	2
DiaTex, Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty payment					0	0	0
Monthly license fees			$ 2,000
Potential future development payments			$ 800,000
Development payment					$ 0	$ 0	$ 0

Collaboration and License Agr_4

Collaboration and License Agreements - Accounts Receivable from the Kowa Contract (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts Receivable	$ 5,000
Kowa Pharmaceuticals America Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Accounts Receivable	$ 5,000

Facility Loans - Additional Inf

Facility Loans - Additional Information (Detail) - USD ($)	Jun. 04, 2018	Aug. 07, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2013
Debt Instrument [Line Items]
Repayment of facility loan			$ 6,527,000	$ 3,137,000	$ 986,000
Loss on extinguishment of debt			$ (407,000)
Facility loan, less current portion				$ 2,990,000
Warrants [Member]
Debt Instrument [Line Items]
Fair value of warrant liabilities						$ 300,000
2015 Term Loan Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 15,000,000
Facility loan, fixed interest rate		8.77%
Debt instrument payment terms			The Company was required to make 12 monthly interest only payments after the funding date followed by a repayment schedule equal to 36 equal monthly payments of interest and principal.
Percentage of principal amount as final payment		6.50%
Facility fee		1.00%
Issued warrants to purchase common stock			114,436
Exercise price of common stock			$ 2.84
Warrant term			10 years
Repayment of facility loan	$ 4,200,000
Facility loan, final fee	700,000
Prepayment penalty	100,000
Loss on extinguishment of debt	$ (400,000)
Facility loan, less current portion			$ 0
2015 Term Loan Facility [Member] | First Tranche [Member]
Debt Instrument [Line Items]
Facility loan, drawn		$ 10,000,000
2015 Term Loan Facility [Member] | Second Tranche [Member]
Debt Instrument [Line Items]
Facility loan available for draw down		5,000,000
2013 Term Loan Facility [Member]
Debt Instrument [Line Items]
Retiring of existing debt		$ 4,100,000

Facility Loans - Schedule of Te

Facility Loans - Schedule of Term Loan Facility, Debt Discounts and Final Payment (Detail) - 2015 Term Loan Facility [Member] $ in Thousands	Dec. 31, 2017USD ($)
Line of Credit Facility [Line Items]
Principal payments due under the loan facility	$ 5,877
Less: unamortized debt discount	(296)
Plus: accreted value of final payment	517
Term loan facility, net	$ 6,098

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Apr. 16, 2018USD ($)ft²	Nov. 08, 2013ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Loss Contingencies [Line Items]
Rent expenses			$ 300,000	$ 300,000	$ 300,000
Lease expiration date	Jan. 15, 2024
Lease term, option to renew period	5 years
Area of office space to be expanded | ft²	17,698
Accretion of tenant improvement allowance	$ 2,300,000		263,000
Indemnification liabilities			0	$ 0
Accrued in the consolidated balance sheets related to indemnification obligations			$ 0
Lease Facility [Member]
Loss Contingencies [Line Items]
Area of office space | ft²		8,894
Lease start date		Jan. 16, 2014
Lease expiration date		Jan. 15, 2019

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Rent Payments (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,019	$ 628
2,020	647
2,021	666
2,022	687
2,023	707
Thereafter	30
Total future minimum lease payments	$ 3,365

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Sep. 30, 2018	Feb. 01, 2018	Jul. 24, 2017	Feb. 07, 2017	Aug. 07, 2015	Feb. 28, 2019	Sep. 30, 2013	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013	Dec. 28, 2018
Class of Stock [Line Items]
Preferred stock, shares authorized								10,000,000	10,000,000
Common stock, shares authorized								100,000,000	100,000,000
Common stock, shares issued		13,340,000	14,950,000	5,181,348				59,456,493	44,408,796
Common stock offering price		$ 10.80	$ 6.50	$ 1.93
Net proceeds from public offering		$ 135,500,000	$ 91,100,000	$ 9,200,000
Registration filed on Form S-3		$ 200,000,000										$ 200,000,000
Change in fair value of warrant liability								$ 3,710,000	$ 5,773,000	$ (75,000)
Warrants exercised								443,505	40,250
Cash proceeds from exercise of warrants								$ 2,550,000	$ 231,000
Common stock warrants exercised in cashless transactions								938,300	166,193
Net shares issued through cashless warrant exercises								513,340	58,957
Number of unexercised warrants expired	79,150
Gain on extinguishment of warrant liability	$ 400,000							$ 422,000
Number of warrants outstanding								0
Warrants, Exercise price of $5.75 per share [Member]
Class of Stock [Line Items]
Issued warrants to purchase common stock											1,741,788
Exercise price of common stock											$ 5.75
Warrant term											5 years
Warrants, Exercise Price of $5.00 Per Share [Member]
Class of Stock [Line Items]
Issued warrants to purchase common stock							121,739
Exercise price of common stock							$ 5
Warrant term							7 years
Warrants, Exercise Price of $2.84 Per Share [Member]
Class of Stock [Line Items]
Common stock, shares issued					114,436
Exercise price of common stock					$ 2.84
Warrant term					10 years
Subsequent Event [Member]
Class of Stock [Line Items]
Terminated amount of shelf registration statement						$ 200,000

Stockholder's Equity - Reserved

Stockholder's Equity - Reserved Shares of Authorized but Unissued Common Stock (Detail) - shares	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Total reserved shares of common stock	6,991,570	5,482,938
Common Stock Warrants [Member]
Class of Stock [Line Items]
Total reserved shares of common stock		1,460,955
Equity Incentive Plan [Member]
Class of Stock [Line Items]
Total reserved shares of common stock	6,991,570	4,021,983

Stock Plan and Stock-Based Co_3

Stock Plan and Stock-Based Compensation - Additional Information (Detail) - USD ($)	Jan. 01, 2019	Jul. 31, 2016	Sep. 30, 2013	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2013	Dec. 31, 2007	Jun. 30, 2014	Apr. 30, 2014	Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised				$ 4,900,000	$ 2,500,000	$ 0
Fair value of options vested				7,000,000	3,900,000	2,200,000
Unamortized employee and non-employee stock-based compensation expense				$ 16,600,000
Unamortized employee and non-employee stock-based compensation expense recognized period				2 years 9 months 18 days
Number of option granted to employees				2,167,272
Clinical development expense recognized				$ 0	$ 200,000	200,000
Share reserved for issue				6,991,570	5,482,938
Stock-based compensation expense				$ 7,013,000	$ 4,920,000	2,473,000
Stock options outstanding				5,593,132	4,356,441
Options to purchase common stock, unvested				0
Performance Option [Member] | Executives and Senior Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of option granted to employees		327,000
Scientific Advisors and Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, expiration period				10 years
Share based compensation arrangement by share based payment award, award vesting period				48 months
Stock-based compensation expense				$ 100,000	$ 100,000
Issued warrants to purchase common stock				10,000	15,000
Options to purchase common stock, unvested				22,793
Incentive award issued				2,335
Incentive awards outstanding, vested				2,335
2013 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, expiration period			10 years
Share based compensation arrangement percentage increase in share reserved			5.00%
Shares available for grant				1,268,662
2013 Equity Incentive Plan [Member] | Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for issuance	2,378,259
2013 Equity Incentive Plan [Member] | Incentive Stock Options for Employees and Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage			100.00%
2013 Equity Incentive Plan [Member] | Nonqualified Options to Employees, Directors and Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage			85.00%
2013 Equity Incentive Plan [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage			85.00%
Share based compensation arrangement by share based payment award, award vesting period			4 years
2013 Equity Incentive Plan [Member] | Stock Options to 10% Stockholders [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, exercise price percentage								110.00%
Share based compensation arrangement by share based payment award, award vesting period								5 years
Incentive Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation arrangement by share based payment award, expiration period							10 years
Share based compensation arrangement by share based payment award, award vesting period							4 years
Share reserved for issue							252,752		500,000	252,752	252,752
Exercisable weighted average price per share							$ 5.21			$ 5.21	$ 5.21
Stock option plan, Description				Vest monthly over four years effective from their grant date.
Stock-based compensation expense					$ 300,000	$ 300,000
Stock options outstanding				129,776	129,776
Incentive Awards [Member] | First Tranche [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incentive awards vested percentage							100.00%

Stock Plan and Stock-Based Co_4

Stock Plan and Stock-Based Compensation - Summary of Stock Option Grants, Including Performance Options (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)$ / sharesshares
Shares Subject to Outstanding Options
Outstanding at the beginning of period | shares	4,356,441
Options granted | shares	2,167,272
Options exercised | shares	(750,852)
Options forfeited | shares	(179,729)
Outstanding as end of period | shares	5,593,132
Vested and expected to vest | shares	5,593,132
Exercisable | shares	2,627,819
Weighted-Average Exercise Price of Options
Outstanding at the beginning of period | $ / shares	$ 5.15
Options granted | $ / shares	11.84
Options exercised | $ / shares	4.76
Options forfeited | $ / shares	8.81
Outstanding as end of period | $ / shares	7.68
Vested and expected to vest | $ / shares	7.68
Exercisable | $ / shares	$ 5.65
Weighted-Average Remaining Contractual Term (Years)
Outstanding	8 years 14 days
Vested and expected to vest	8 years 14 days
Exercisable	7 years 25 days
Aggregate Intrinsic Value (In Thousands)
Outstanding | $	$ 11,096
Vested and expected to vest | $	11,096
Exercisable | $	$ 7,799

Stock Plan and Stock-Based Co_5

Stock Plan and Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 7,013	$ 4,920	$ 2,473
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	2,760	1,301	995
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 4,253	$ 3,619	$ 1,478

Stock Plan and Stock-Based Co_6

Stock Plan and Stock-Based Compensation - Estimated Weighted-Average Grant Date Fair Value (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	6 years 2 months 12 days	6 years	6 years 1 month 6 days
Expected volatility	77.00%	84.00%	80.00%
Risk-free interest rate	2.62%	2.15%	1.57%
Expected dividend yield			0.00%
Weighted-average grant date fair value per share	$ 8.14	$ 3.36	$ 0.89
Performance Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term			5 years 1 month 6 days
Expected volatility			85.00%
Risk-free interest rate			1.56%
Expected dividend yield			0.00%
Weighted-average grant date fair value per share			$ 1.20

401(k) Plan - Additional Inform

401(k) Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Contribution Pension And Other Postretirement Plans Disclosure [Abstract]
Employees contribution to qualified savings plan	$ 750	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax [Line Items]
Provision for income taxes	$ 0	$ 0
US federal corporate tax rate	21.00%	35.00%
Limitation of the deduction for net operating losses	80.00%
Reduction in deferred tax assets		$ (38,200,000)
Net valuation allowance increase (decrease)	$ 29,500,000	$ (32,700,000)
Cumulative change in ownership	50.00%
Cumulative change in ownership period	3 years
Significant change to its unrecognized tax benefits over the next twelve months	$ 0
Income tax examination years	all years remain open for income tax examination by tax authorities
Domestic Tax Authority [Member]
Income Tax [Line Items]
Net operating loss carryforward	$ 332,700,000
Research and development tax credit carry forwards	8,500,000
Domestic Tax Authority [Member] | Orphan Drug [Member]
Income Tax [Line Items]
Research and development tax credit carry forwards	$ 11,200,000
Domestic Tax Authority [Member] | Minimum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2,024
Domestic Tax Authority [Member] | Maximum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2,037
State and Local Jurisdiction [Member]
Income Tax [Line Items]
Net operating loss carryforward	$ 224,800,000
Research and development tax credit carry forwards	$ 4,500,000
State and Local Jurisdiction [Member] | Minimum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2,028
State and Local Jurisdiction [Member] | Maximum [Member]
Income Tax [Line Items]
NOL carry forward expiry date	2,038

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Federal and state net operating loss carryforwards	$ 85,571	$ 63,935
Capitalized research and development	10,466	9,455
Federal and state tax credit carryforwards	18,590	13,529
Stock based compensation	2,848	1,493
Other	1,499	438
Total deferred tax assets	118,974	88,850
Deferred tax liabilities:
Fixed assets	(622)
Total deferred tax liabilities	(622)
Valuation allowance	(118,352)	(88,850)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Expected Statutory Federal Income Tax Provision to Actual Income Tax Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income tax benefit at federal statutory tax rate	$ (15,235)	$ (9,369)	$ (9,068)
Change in valuation allowance	29,501	(32,709)	9,775
Effect of change in enacted tax rates		38,194
State income taxes, net of federal benefit	(10,112)	5,094	(458)
Permanent items	563	4,027	196
Research credits	(4,717)	(5,237)	(445)
Income tax (benefit) expense	$ 0	$ 0	$ 0

Income Taxes - Summary of Gross

Income Taxes - Summary of Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Balance at beginning of period	$ 3,295	$ 2,286	$ 2,127
Increases related to prior year tax positions	6	0	0
Increases related to tax positions	1,283	1,009	159
Balance at end of period	4,584	3,295	2,286
Increases related to prior year tax positions	$ 6	$ 0	$ 0

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Collaboration revenue					$ 5,207			$ 4,793		$ 10,000
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Total operating expenses	$ 20,555	$ 21,129	$ 17,971	$ 12,850	$ 9,563	$ 6,394	$ 7,626	$ 7,742	$ 72,505	$ 31,325	$ 25,586
Net loss	$ (19,449)	$ (18,563)	$ (17,531)	$ (17,005)	$ (5,043)	$ (8,234)	$ (8,929)	$ (5,351)	$ (72,548)	$ (27,557)	$ (26,671)
Basic net loss per common share	$ (0.32)	$ (0.31)	$ (0.30)	$ (0.32)	$ (0.11)	$ (0.21)	$ (0.31)	$ (0.20)	$ (1.25)	$ (0.79)	$ (1.14)
Diluted net loss per common share	$ (0.32)	$ (0.34)	$ (0.30)	$ (0.32)	$ (0.11)	$ (0.21)	$ (0.31)	$ (0.20)	$ (1.26)	$ (0.79)	$ (1.14)