Kura Oncology (KURA) 10-K 14 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Mar. 10, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Trading Symbol	KURA
Entity Registrant Name	Kura Oncology, Inc.
Entity Central Index Key	1,422,143
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	Smaller Reporting Company
Entity Public Float			$ 45.8
Entity Common Stock, Shares Outstanding		21,384,817

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 9,725	$ 15,443
Short-term investments	58,065	70,303
Accounts receivable, related party	295	430
Prepaid expenses and other current assets	725	693
Total current assets	68,810	86,869
Property and equipment, net	40	71
Other long-term assets	971	319
Total assets	69,821	87,259
Current liabilities:
Accounts payable and accrued expenses	4,681	4,118
Accounts payable and accrued expenses, related party	770	937
Total current liabilities	5,451	5,055
Long-term debt, net	7,324
Other long-term liabilities	170	101
Total liabilities	12,945	5,156
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized; no shares issued and outstanding
Common stock, $0.0001 par value; 200,000 shares authorized; 21,368 and 21,371 shares issued as of December 31, 2016 and 2015, respectively; and 19,348 and 18,138 shares outstanding as of December 31, 2016 and 2015, respectively, excluding 2,020 and 3,233 shares subject to repurchase as of December 31, 2016 and December 31, 2015, respectively	2	2
Additional paid-in capital	110,748	108,484
Accumulated other comprehensive loss	(18)	(87)
Accumulated deficit	(53,856)	(26,296)
Total stockholders' equity	56,876	82,103
Total liabilities and stockholders' equity	$ 69,821	$ 87,259

BALANCE SHEETS (Parenthetical)

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	21,368,000	21,371,000
Common stock, shares outstanding	19,348,000	18,138,000
Number of shares, subject to repurchase	2,020,000	3,233,000

STATEMENTS OF OPERATIONS AND CO

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating Expenses:
Research and development	$ 16,575	$ 13,905
Research and development, related party	3,829	3,872
General and administrative	7,861	6,019
General and administrative, related party	102	69
Total operating expenses	28,367	23,865
Other Income (Expense):
Management fee income, related party	885	1,200
Interest income	499	128
Interest expense	(577)	(42)
Interest expense, related party		(46)
Total other income	807	1,240
Net loss	$ (27,560)	$ (22,625)
Net loss per share, basic and diluted	$ (1.47)	$ (2.28)
Weighted-average number of shares used in computing net loss per share, basic and diluted	18,701	9,933
Comprehensive Loss:
Net loss	$ (27,560)	$ (22,625)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	69	(87)
Comprehensive loss	$ (27,491)	$ (22,712)

STATEMENTS OF STOCKHOLDERS' EQU

STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid- In Capital	Unrealized Gain (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2014	$ (3,433)		$ 238		$ (3,671)
Beginning balance (in shares) at Dec. 31, 2014		411
Issuance of common stock, net of offering costs	97,870	$ 2	97,868
Issuance of common stock, net of offering costs, ( in shares)		15,164
Issuance of common stock for license fee	500		500
Issuance of common stock for license fee, ( in shares)		79
Conversion of notes payable and accrued interest	7,615		7,615
Conversion of notes payable and accrued interest (in shares)		1,205
Restricted stock awards vested	4		4
Restricted stock awards vested (in shares)		1,279
Share-based compensation expense	2,259		2,259
Unrealized gain (loss) on marketable securities	(87)			$ (87)
Net loss	(22,625)				(22,625)
Ending balance at Dec. 31, 2015	82,103	$ 2	108,484	(87)	(26,296)
Ending balance (in shares) at Dec. 31, 2015		18,138
Restricted stock awards vested	3		3
Restricted stock awards vested (in shares)		1,210
Share-based compensation expense	2,089		2,089
Unrealized gain (loss) on marketable securities	69			69
Issuance of warrants in connection with debt facility	172		172
Net loss	(27,560)				(27,560)
Ending balance at Dec. 31, 2016	$ 56,876	$ 2	$ 110,748	$ (18)	$ (53,856)
Ending balance (in shares) at Dec. 31, 2016		19,348

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating Activities
Net loss	$ (27,560)	$ (22,625)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	2,089	2,259
Non-cash license fee expense		500
Change in value of derivative liability		268
Non-cash interest expense	42	37
Non-cash interest expense, related party		42
Depreciation expense	31	20
Amortization of discount on marketable securities	129	171
Changes in operating assets and liabilities:
Accounts receivable, related party	135	(400)
Prepaid expenses and other current assets	(32)	(650)
Other long-term assets	(652)	(164)
Accounts payable and accrued expenses	471	2,812
Accounts payable and accrued expenses, related party	(167)	803
Other long-term liabilities	165	(998)
Net cash used in operating activities	(25,349)	(17,925)
Investing Activities
Maturities of marketable securities	68,605	6,000
Purchases of marketable securities	(56,427)	(76,562)
Purchases of property and equipment		(64)
Net cash provided by (used in) investing activities	12,178	(70,626)
Financing Activities
Proceeds from issuance of long-term debt, net	7,453
Proceeds from issuance of common stock, net		97,870
Proceeds from issuance of convertible notes		4,290
Proceeds from issuance of convertible notes, related party		710
Net cash provided by financing activities	7,453	102,870
Net (decrease) increase in cash and cash equivalents	(5,718)	14,319
Cash and cash equivalents at beginning of period	15,443	1,124
Cash and cash equivalents at end of period	9,725	15,443
Supplemental disclosure of cash flow information:
Interest paid	352
Supplemental non-cash disclosures:
Warrants issued in connection with debt facility	$ 172
Conversion of convertible notes and related accrued interest to common stock		4,327
Conversion of convertible notes and related accrued interest to common stock, related party		$ 3,288

Organization and Basis of Prese

Organization and Basis of Presentation	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Organization and Basis of Presentation	1. Organization and Basis of Presentation Kura Oncology, Inc., is a clinical-stage biopharmaceutical company committed to realizing the promise of precision medicines for the treatment of cancer. Our pipeline consists of small molecule product candidates that target cancer signaling pathways where there is a strong scientific and clinical rationale to improve outcomes by identifying those patients most likely to benefit from treatment. References in these Notes to Financial Statements to the “Company” or “we”, “our” or “us”, refer to Kura Oncology, Inc., or Prior Kura, a private Delaware corporation incorporated in the State of Delaware in August 2014, for the periods prior to the Merger (as defined below) which took place on March 6, 2015, and Kura Oncology, Inc., a Delaware corporation incorporated in November 2007 and formerly known as Zeta Acquisition Corp. III, or Zeta, a public shell company, for the periods following the Merger. Effective March 6, 2015, or the Effective Time, we completed a reverse merger, or the Merger, with a wholly owned subsidiary of Zeta, leaving Prior Kura as the surviving entity. On March 31, 2015, the surviving entity merged with and into us. Zeta was formed in November 2007 with no specific business plan or purpose. As a result of the Merger and related transactions, Zeta changed its name to “Kura Oncology, Inc.” and began operating Prior Kura’s business. Pursuant to the terms of an Agreement and Plan of Merger dated March 6, 2015, by and among Zeta, Kura Operations, Inc. and Prior Kura, at the Effective Time, each share of Prior Kura common stock outstanding immediately prior to the Effective Time was exchanged for one-half (0.5) of a share of our common stock. We issued an aggregate of 14,508,177 shares of our common stock upon such exchange of the Prior Kura common stock outstanding. The Merger was accounted for as a reverse merger and a capital transaction. Prior Kura is the acquirer for accounting purposes and Zeta is the acquired company. Immediately prior to the Merger, on March 6, 2015, Prior Kura sold to investors 9,485,566 shares of its common stock at a price of $6.32 per share, or Private Placement, for net proceeds of approximately $55.8 million, which included approximately $7.5 million in principal and $115,000 in accrued interest from the conversion of the then outstanding convertible promissory notes.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates Our financial statements are prepared in accordance with accounting principles generally accepted in the United States. The preparation of our financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Reported amounts and note disclosures reflect the overall economic conditions that are most likely to occur and anticipated measures management intends to take. Actual results could differ materially from those estimates. All revisions to accounting estimates are recognized in the period in which the estimates are revised and in any future periods affected. Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. We operate in a single industry segment which is the discovery and development of precision medicines for the treatment of cancer. Our chief operating decision-maker reviews the operating results on an aggregate basis and manages the operations as a single operating segment. Cash and Cash Equivalents Cash and cash equivalents consist of checking, money market and highly liquid investments that are readily convertible to cash and that mature within three months or less from the date of purchase. The carrying amounts approximate fair value due to the short maturities of these instruments. Short-Term Investments Short-term investments are marketable securities with maturities greater than three months from date of purchase that are specifically identified to fund current operations. These investments are classified as current assets, even though the stated maturity date may be one year or more beyond the current balance sheet date, which reflects management’s intention to use the proceeds from sales of these securities to fund our operations, as necessary. The cost of short-term investments is adjusted for amortization of premiums or accretion of discounts to maturity, and such amortization or accretion is included in interest income. Dividend and interest income is recognized as interest income on the statements of operations and comprehensive loss when earned. Short-term investments are classified as available-for-sale securities and carried at fair value with unrealized gains and losses recorded in other comprehensive loss and included as a separate component of stockholders' equity. Realized gains and losses from the sale of available-for-sale securities and declines in value judged to be other than temporary on short-term investments, if any, are determined on a specific identification basis and are reclassified out of comprehensive loss and included in interest income on the statements of operations and comprehensive loss. Fair Value Measurements Fair value is defined as the exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: • Level 1 - Quoted prices (unadjusted) in active markets for identical assets or liabilities; • Level 2 - Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable; • Level 3 - Unobservable inputs in which little or no market activity exists, therefore requiring an entity to develop its own assumptions about the assumptions that market participants would use in pricing. Concentration of Credit Risk Financial instruments that potentially subject us to significant concentrations of credit risk consist primarily of cash, cash equivalents and short-term investments. We maintain deposits in federally insured financial institutions in excess of federally insured limits. We have established guidelines to limit our exposure to credit risk by placing investments with high credit quality financial institutions, diversifying our investment portfolio and placing investments with maturities that maintain safety and liquidity. Property and Equipment Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets which is three years for each asset class. Impairment of Long-Lived Assets We review our long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. If such circumstances are determined to exist, an estimate of undiscounted future cash flows produced by the long-lived asset, including its eventual residual value, is compared to the carrying value to determine whether impairment exists. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their estimated fair values. While our current and historical operating losses and negative cash flows are indicators of impairment, we believe that future cash flows to be received support the carrying value of our long-lived assets and, accordingly, have not recognized any impairment losses through December 31, 2016. Research and Development Expenses Research and development expenses consist of costs associated with our research activities including salaries, benefits, share-based compensation and other personnel costs, clinical trial costs, preclinical study fees, manufacturing costs for non-commercial products, costs for the development of our earlier-stage programs and research supply, equipment and facility costs. All such costs are charged to research and development expense as incurred when these expenditures have no alternative future uses. We are obligated to make upfront payments upon execution of certain research and development agreements. Advance payments, including nonrefundable amounts, for goods or services that will be used or rendered for future research and development activities are deferred. Such amounts are recognized as expense as the related goods are delivered or the related services are performed or such time when we do not expect the goods to be delivered or services to be performed. Payments that we make in connection with in-licensed technology for a particular research and development project that have no alternative future uses (in other research and development projects or otherwise) and therefore no separate economic values are expensed as research and development costs at the time such costs are incurred. As of December 31, 2016, we have no in-licensed technologies that have alternative future uses in research and development projects or otherwise. Clinical Trial Costs and Accruals A significant portion of our clinical trial costs relate to contracts with contract research organizations, or CROs. The financial terms of our CRO contracts may result in payment flows that do not match the periods over which materials or services are provided to us under such contracts. Our objective is to reflect the appropriate clinical trial expenses in our financial statements by matching those expenses with the period in which services and efforts are expended. As part of the process of preparing our financial statements, we rely on cost information provided by our CROs (concerning monthly expenses as well as reimbursement for pass through costs). We are also required to estimate certain of our expenses resulting from our obligations under our CRO contracts. Accordingly, our clinical trial accrual is dependent upon the timely and accurate reporting of CROs and other third-party vendors. If the contracted amounts are modified (for instance, as a result of changes in the clinical trial protocol or scope of work to be performed), we modify our accruals accordingly on a prospective basis. Revisions in the scope of a contract are charged to expense in the period in which the facts that give rise to the revision become reasonably certain. Historically, we have had no material changes in clinical trial expense that had a material impact on our results of operations or financial position. Patent Costs We expense all costs as incurred in connection with patent applications, including direct application fees, and the legal and consulting expenses related to making such applications, and such costs are included in general and administrative expenses on the statements of operations and comprehensive loss. Share-Based Payments Our share-based awards are measured at fair value on the date of grant based upon the estimated fair value of common stock. The fair value of awards expected to vest are recognized and amortized on a straight-line basis over the requisite service period of the award less actual forfeitures. The fair value of each stock option is estimated on the date of grant using the Black-Scholes option pricing model, or Black-Scholes model, that requires the use of subjective assumptions including volatility, expected term, risk-free rate and the fair value of the underlying common stock. Awards granted to non-employees are subject to periodic revaluation over their vesting terms. The fair value of non-employee awards is remeasured at each reporting period as the underlying awards vest unless the instruments are fully vested, immediately exercisable and nonforfeitable on the date of grant. We record the expense for stock option grants to non-employees based on the estimated fair value of the stock options using the Black-Scholes model. Estimated fair value of the restricted stock awards granted to non-employees is recorded on the earlier of the performance commitment date or the date the services required are completed and are remeasured at fair value during the service period. As non-employee restricted stock awards vest, they are remeasured at fair value and expensed based on the intrinsic value method which is measured as the difference between the exercise price paid for the restricted stock award and the fair value of the shares as the right of the repurchase lapses each vesting period. Income Taxes Income taxes are accounted for using the asset and liability method. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates applicable to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance against deferred tax assets is recorded if, based upon the weight of all available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. For uncertain tax positions that meet “a more likely than not” threshold, we recognize the benefit of uncertain tax positions in the financial statements. Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity during the period from transactions and other events and non-owner sources. For the periods presented, accumulated other comprehensive income (loss) consists solely of unrealized gains and losses on marketable securities. Net Loss per Share Net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by dividing the net loss by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. Dilutive common stock equivalents are comprised of unvested restricted stock awards, outstanding stock options and outstanding warrants. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to the antidilutive effect of the securities. Because of our net loss, unvested restricted stock awards, outstanding stock options and outstanding warrants are excluded from the calculation of diluted net loss per common share for the years ended December 31, 2016 and 2015, due to the anti-dilutive effect of the securities. The following table summarizes the number of potentially dilutive securities that were excluded from our calculation of diluted net loss per share for the years ended December 31, 2016 and 2015: Years Ended December 31, 2016 2015 Unvested restricted stock awards 2,020,266 3,232,350 Stock options 1,201,591 574,312 Warrants 67,976 — Total 3,289,833 3,806,662

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2016
Accounting Changes And Error Corrections [Abstract]
Recent Accounting Pronouncements	3. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2014-09, Revenue from Contracts with Customers (Topic 606), that supersedes most current revenue recognition guidance, including industry-specific guidance. The guidance provides that an entity recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments, and assets recognized from costs incurred to obtain or fulfill a contract. In July 2015, the FASB voted to amend ASU 2014-09 by approving a one-year deferral of the effective date as well as providing the option to early adopt the standard on the original effective date. Accordingly, we will adopt the standard in the first quarter of 2018. We plan to adopt the accounting standard using the modified retrospective transition approach. The modified retrospective transition approach will recognize any changes from the beginning of the year of initial application through retailed earnings with no restatement of comparative periods. We currently do not have any revenue contracts with customers and will review any new contracts entered into prior to the adoption of the new standard. The adoption of this guidance is not expected to have an impact on our financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires lessees to recognize a right-to-use asset and a lease obligation for all leases. Lessees are permitted to make an accounting policy election to not recognize an asset and liability for leases with a term of 12 months or less. Lessor accounting under the new standard is substantially unchanged. Additional qualitative and quantitative disclosures, including significant judgments made by management, will be required.

Investments

Investments	12 Months Ended
	Dec. 31, 2016
Investments All Other Investments [Abstract]
Investments	4. Investments We invest in available-for-sale securities consisting of money market funds, U.S. Treasury securities, corporate debt securities, commercial paper and government sponsored enterprise securities. Available-for-sale securities are classified as part of either cash and cash equivalents or short-term investments in the balance sheets. The following tables summarize, by major security type, our investments that are measured at fair value on a recurring basis as of December 31, 2016 and 2015, in thousands: As of December 31, 2016 Maturities (years) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents: Money market funds 1 or less $ 5,762 $ — $ — $ 5,762 Commercial paper 1 or less 2,000 — — 2,000 Total cash equivalents 7,762 — — 7,762 Short-term investments: U.S. Treasury securities 2 or less 28,006 5 (9 ) 28,002 Commercial paper 1 or less 14,273 — — 14,273 Corporate debt securities 2 or less 13,603 — (14 ) 13,589 Government sponsored enterprise securities 1 or less 2,201 — — 2,201 Total short-term investments 58,083 5 (23 ) 58,065 Total $ 65,845 $ 5 $ (23 ) $ 65,827 As of December 31, 2015 Maturities (years) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents: Money market funds 1 or less $ 12,984 $ — $ — $ 12,984 Short-term investments: U.S. Treasury securities 2 or less 16,007 — (18 ) 15,989 Commercial paper 1 or less 18,367 — — 18,367 Corporate debt securities 2 or less 22,758 — (48 ) 22,710 Government sponsored enterprise securities 2 or less 13,258 — (21 ) 13,237 Total short-term investments 70,390 — (87 ) 70,303 Total $ 83,374 $ — $ (87 ) $ 83,287 The available-for-sale investments are classified as current assets, even though the stated maturity date may be one year or more beyond the current balance sheet date, which reflects management’s intention to use the proceeds from sales of these securities to fund our operations, as necessary. As of December 31, 2016 and 2015, $50.3 million and $57.6 million of our short-term investments had maturities less than one year, respectively, and $7.8 million and $12.7 million had maturities between one to two years, respectively. There were no realized gains or losses for the years ended December 31, 2016 and 2015. As of December 31, 2016 and 2015, $32.8 million and $51.9 million of our marketable securities were in gross unrealized loss positions, respectively, all of which had been in such position for less than 12 months. We reviewed our marketable securities as of December 31, 2016 and determined that the unrealized losses were not considered to be other-than-temporary based upon (i) the financial strength of the issuing institution and (ii) the fact that all securities have been in an unrealized loss position for less than 12 months. In addition, we do not intend to sell these securities and it is not more likely than not that we will be required to sell these securities before the recovery of their amortized cost basis

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	5. Fair Value Measurements As of December 31, 2016 and 2015, we had cash equivalents and short-term investments measured at fair value on a recurring basis. The carrying amounts of our financial instruments, which include cash equivalents, prepaid expenses, accounts payable, accrued expenses and all related party amounts approximate their fair values as of December 31, 2016 and 2015, primarily due to their short-term nature. 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 and therefore cannot be determined with precision. Available-for-sale marketable securities consist of U.S. Treasury securities, which were measured at fair value using Level 1 inputs, and corporate debt securities, commercial paper and government sponsored enterprise securities, which were measured at fair value using Level 2 inputs. We determine the fair value of Level 2 related securities with the aid of valuations provided by third parties using proprietary valuation models and analytical tools. These valuation models and analytical tools use market pricing or prices for similar instruments that are both objective and publicly available, including matrix pricing or reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids and/or offers. We validate the fair values of Level 2 financial instruments by comparing these fair values to a third-party pricing source. No transfers between levels have occurred during the periods presented. The following tables summarize, by major security type, our cash equivalents and short-term investments that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy as of December 31, 2016 and 2015, in thousands: As of December 31, 2016 Balance Level 1 Level 2 Cash equivalents: Money market funds $ 5,762 $ 5,762 $ — Commercial paper 2,000 — 2,000 Total cash equivalents 7,762 5,762 2,000 Short-term investments: U.S. Treasury securities 28,002 28,002 — Commercial paper 14,273 — 14,273 Corporate debt securities 13,589 — 13,589 Government sponsored enterprise securities 2,201 — 2,201 Total short-term investments 58,065 28,002 30,063 Total $ 65,827 $ 33,764 $ 32,063 As of December 31, 2015 Balance Level 1 Level 2 Cash equivalents: Money market funds $ 12,984 $ 12,984 $ — Short-term investments: U.S. Treasury securities 15,989 15,989 — Commercial paper 18,367 — 18,367 Corporate debt securities 22,710 — 22,710 Government sponsored enterprise securities 13,237 — 13,237 Total short-term investments 70,303 15,989 54,314 Total $ 83,287 $ 28,973 $ 54,314 We believe that our term loan facility bears interest at a rate that approximates prevailing market rates for instruments with similar characteristics and, accordingly, the carrying value of the term loan facility approximates fair value. The fair value of our term loan facility is determined using Level 2 inputs in the fair value hierarchy. See Note 8, Long-Term Debt, for further discussion of our term loan facility.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Property and Equipment, Net	6. Property and Equipment, Net Property and equipment consisted of the following, in thousands: December 31, 2016 2015 Computer equipment $ 85 $ 85 Software 7 7 Property and equipment, gross 92 92 Less: accumulated depreciation (52 ) (21 ) Property and equipment, net $ 40 $ 71 Depreciation expense was $31,000 and $20,000 for the years ended December 31, 2016 and 2015, respectively.

Accounts Payable and Accrued Li

Accounts Payable and Accrued Liabilities	12 Months Ended
	Dec. 31, 2016
Payables And Accruals [Abstract]
Accounts Payable and Accrued Liabilities	7. Accounts Payable and Accrued Liabilities Accounts payable and accrued liabilities consisted of the following, in thousands: December 31, 2016 2015 Accounts payable $ 638 $ 902 Accrued compensation and benefits 1,907 1,282 Other accrued expenses 2,136 1,934 Total accounts payable and accrued expenses $ 4,681 $ 4,118

Long-Term Debt

Long-Term Debt	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Long-Term Debt	8. Long-Term Debt On April 27, 2016, we entered into a loan and security agreement, or the Loan Agreement, with Oxford Finance LLC and Silicon Valley Bank, or the Lenders, pursuant to which the Lenders provided a term loan facility of up to $20.0 million. Upon entering into the Loan Agreement, we borrowed $7.5 million from the Lenders, or Term A Loan. We may, at our sole discretion, borrow up to an additional $12.5 million at any time between December 31, 2016 and May 1, 2017, or Term B Loan, and together with the Term A Loan, the Term Loans, subject to our successful advancement of KO-947, a small molecule inhibitor of extracellular signal regulated kinase, into Phase 1 clinical trials. In addition, each Term B Loan must be in an amount equal to the lesser of $5.0 million or the amount that is remaining under the Term B Loan. All of the Term Loans will mature on November 1, 2020 , or Maturity Date. Repayment of the We are subject to customary affirmative and restrictive covenants under the term loan facility. Our obligations under the Loan Agreement are secured by a first priority security interest in substantially all of our current and future assets, other than our intellectual property. We have also agreed not to encumber our intellectual property assets, except as permitted by the Loan Agreement. The Loan Agreement also contains customary indemnification obligations and customary events of default, including, among other things, our failure to fulfill certain obligations under the Loan Agreement and the occurrence of a material adverse change in our business, operations, or condition (financial or otherwise), a material impairment of the prospect of repayment of any portion of the loan, or a material impairment in the perfection or priority of Lenders’ lien in the collateral or in the value of such collateral. In the event of default by us under the Loan Agreement, the Lenders would be entitled to exercise their remedies thereunder, including the right to accelerate the debt, upon which we may be required to repay all amounts then outstanding under the Loan Agreement. The conditional exercisable call option related to the event of default is considered to be an embedded derivative which is required to be bifurcated and accounted for as a separate financial instrument. In the periods presented, the value of the embedded derivative is not material, but could become material in future periods if an event of default became more probable than is currently estimated. As of December 31, 2016, we were in compliance with all material covenants under the Loan Agreement and there had been no material adverse change. In connection with the Term A Loan, we issued to the Lenders warrants to purchase up to 67,976 shares of our common stock at an exercise price of $3.31 per share, or the Warrants. The Warrants are exercisable, in whole or in part, and will terminate on the earlier of April 27, 2026 or the closing of certain merger or consolidation transactions. The Warrants were valued using the Black-Scholes model with the following assumptions: volatility of 70.92%, expected term of ten years, risk-free interest rate of 2.11% and a zero dividend yield. The fair value of the Warrants was approximately $172,000 upon issuance, which was recorded as a debt discount and is being amortized to interest expense using the effective interest method through the scheduled maturity date. If we borrow under the Term B Loan, upon the funding of the Term B Loan, we will issue to the Lenders additional warrants to purchase shares of our common stock equal to 3.00% of each Term B Loan amount divided by the lower of (i) the ten day average closing price of our common stock reported on the Nasdaq Global Select Market prior to funding or (ii) the closing price of our common stock reported on the Nasdaq Global Select Market on the day prior to funding. Such lower amount of (i) and (ii) above will also be the exercise price per share for such warrants. The terms of such warrants would be substantially the same as those contained in the Warrants. The following table summarizes future minimum payments under the term loan facility as of December 31, 2016, in thousands: Year Ending December 31, 2017 $ 607 2018 2,323 2019 3,355 2020 3,424 Total future minimum payments 9,709 Less: interest payments (2,209 ) Principal amount of long-term debt 7,500 Less: Unamortized discount (176 ) Long-term debt, net of unamortized discount 7,324 Current portion of long-term debt — Long-term debt, net $ 7,324

Notes Payable

Notes Payable	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Notes Payable	9. Notes Payable Araxes Convertible Note In October 2014, we entered into a Note Purchase Agreement and Convertible Promissory Note with an affiliated company Araxes Pharma LLC, or Araxes, under which Araxes provided a $2.0 million loan in the form of a convertible promissory note. In connection with the Private Placement, the total amount of unpaid principal and accrued interest as of February 28, 2015 was automatically converted into 326,443 shares of our common stock. Araxes Asset Purchase Agreement – Convertible Note As consideration for the patents acquired under the Araxes Asset Purchase Agreement entered into in December 2014, Araxes issued a convertible promissory note equal to the purchase price of the patent rights of $500,000. In connection with the Private Placement, the total amount of unpaid principal and accrued interest as of February 28, 2015 under the note was automatically converted into 80,293 shares of our common stock. January 2015 Convertible Notes In January 2015, we entered into a Note Purchase Agreement and Convertible Promissory Note for a $3.0 million loan with various persons and entities named within the agreement of which $710,000 were with certain officers and certain officers’ related parties. In connection with the Private Placement, the total amount of unpaid principal and accrued interest as of February 28, 2015 under the note was automatically converted into 479,667 shares of our common stock. JJDC Convertible Note In accordance with the license agreement with Janssen Pharmaceutica NV, a foreign entity headquartered in Belgium and an affiliate of Johnson & Johnson, Inc., or Janssen, in January 2015 we entered into a Convertible Promissory Note with Janssen’s affiliated company, Johnson & Johnson Innovation – JJDC, Inc., for $1.0 million. In connection with the Private Placement, the total amount of unpaid principal and accrued interest as of February 28, 2015 under the note was automatically converted into 159,615 shares of our common stock. February 2015 Convertible Notes In February 2015, we entered into a Note Purchase Agreement and Convertible Promissory Note with entities named within the agreement, or the February 2015 Note Holders, under which the February 2015 Note Holders provided a $1.0 million loan in the form of convertible promissory notes. In connection with the Private Placement, the total amount of unpaid principal and accrued interest as of February 28, 2015 under the note was automatically converted into 158,852 shares of our common stock.

License Agreements

License Agreements	12 Months Ended
	Dec. 31, 2016
License Agreements [Abstract]
License Agreements	10. License Agreements Janssen License Agreement In December 2014, we entered into a license agreement with Janssen, which was amended in June 2016, under which we received certain intellectual property rights related to tipifarnib in all indications other than The agreement will terminate upon the last-to-expire patent rights or last-to-expire royalty term, or may be terminated by us with 180 days written notice of termination. Either party may terminate the agreement in the event of material breach of the agreement that is not cured within 45 days. Janssen may also terminate the agreement due to our lack of diligence that is not cured within a three-month period. The upfront license fee was recorded as research and development expense for the period from August 22, 2014 (Inception) to December 31, 2014 and paid in January 2015. Subsequent to such payment, in accordance with the agreement, we entered into a convertible promissory note with Johnson & Johnson Innovation—JJDC, Inc. as described in Note 9. The University of Michigan License Agreement In December 2014, we entered into a license agreement with the Regents of the University of Michigan, or the University of Michigan, which was amended in March 2015, July 2015, September 2016 and February 2017, under which we received certain license rights for a non-refundable upfront license, annual maintenance fees and payments upon achievement of certain development and sales-based milestones. The licensed asset consists of several compounds, which are in the lead discovery/lead optimization phase. All future development, regulatory and commercial work on the asset will be completed fully and at our sole expense. The University of Michigan retains the right to use the asset for non-commercial research, internal and/or educational purposes, with the right to grant the same limited rights to other non-profit research institutions. Furthermore, the agreement stipulates contingent consideration for the issuance of shares equivalent to a set dollar value upon the occurrence of a qualified financing or a change of control event, as defined in the amendment to the agreement, consistent with the terms issued to any future investors or the per share consideration to be received by other shareholders. As a result of our Private Placement, we issued 79,113 shares of our common stock at a fair value of $500,000, which was recognized as research and development expense during the year ended December 31, 2015. The agreement will terminate upon the last-to-expire patent rights, or may be terminated by us at any time with 90 days written notice of termination or terminated by the University of Michigan upon a bankruptcy by us, payment failure by us that is not cured within 30 days or a material breach of the agreement by us that is not cured within 60 days. The University of California San Francisco License Agreement In November 2014, we entered into a license agreement with The Regents of the University of California San Francisco, or UCSF, which was amended in April 2015, under which we received certain license rights. The agreement provided for an upfront payment as well as contingent milestone payments. Additionally, the agreement provided for a one-time indexed milestone payment upon the occurrence of a qualified financing and a subsequent initial public offering or a change of control event as defined in the agreement. Upon completion of the qualified financing event in March 2015 and the public offering completed in November 2015, the indexed milestone payment was determined to be $464,000 and was paid in full as of December 31, 2016. The license agreement with UCSF was terminated effective as of January 8, 2017. Future Milestone Payments under License Agreements Collectively, all of our license agreements provide for specified development, regulatory and sales-based milestone payments up to a total of $79.4 million payable upon occurrence of each stated event, of which $425,000 relates to the initiation of certain development activities, $28.2 million relates to the achievement of specified regulatory approvals for the first indication and up to $50.8 million for the achievement of specified levels of product sales. Additional payments will be due for each subsequent indication if specified regulatory approvals are achieved. All milestone payments under the agreements will be recognized as research and development expense upon completion of the required events because the triggering events are not considered to be probable until they are achieved. As of December 31, 2016, we have not achieved any milestones under the agreements. Furthermore, if all the programs are successfully commercialized, we will be required to pay tiered royalties on annual net product sales ranging from the low single digits to the low teens, depending on the volume of sales and the respective agreement. Araxes Asset Purchase Agreement In December 2014, we entered into an asset purchase agreement with Araxes, which was amended and restated in February 2015, under which we purchased certain early stage patent rights related to compounds in the field of oncology for a purchase price of $500,000 payable under a convertible promissory note. All ongoing development, regulatory and commercial work will be completed fully and at our sole expense. The agreement allows for contingent milestone payments of $9.7 million throughout development and commercialization of the asset, of which $1.2 million relates to the initiation of certain development activities, and $8.5 million relates to the submission of certain regulatory filings and receipt of certain regulatory approvals. Additional payments will be due for each subsequent indication if specified regulatory approvals are achieved. We will recognize the milestones as expense when each event occurs. Furthermore, if the program is successfully commercialized, we will be required to pay tiered royalties on annual net product sales ranging in the low single digits, depending on the volume of sales. All milestone payments under the agreement will be recognized upon completion of the required events because the triggering events will not be considered to be probable until they are achieved. As of December 31, 2016, we paid a $100,000 milestone payment to Araxes upon the filing of the investigational new drug application, or IND, for KO-947 in the fourth quarter of 2016.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies Sponsored Research Agreement with the University of Michigan In February 2015, we entered into a sponsored research agreement with the University of Michigan under which we agreed to sponsor up to $2.7 million of research at the University of Michigan over a three-year period. We receive a non-exclusive right to any technology developed under this agreement and have an option right for an exclusive right to any such licenses developed under the agreement. The sponsored research agreement allows for termination with notice at any time by us. Any costs incurred for the sponsored research agreement will be expensed as incurred. For the years ended December 31, 2016 and 2015, we recorded approximately $1.0 million and $0.9 million, respectively, in research and development expense under this sponsored research agreement. Operating Leases In August 2014, we entered into a sublease agreement, or the Sublease, with Wellspring Biosciences, Inc. (formerly Wellspring Biosciences LLC), or Wellspring, a wholly owned subsidiary of our affiliated company Araxes for office space located on North Torrey Pines Road in La Jolla, California . The Sublease was amended effective September 1, 2014 to provide for a monthly rent of $4,820 per month. The Sublease includes rent escalation of 3.0% per year. In addition to the base monthly rent, we are obligated to pay for operating expenses, taxes, insurance and utilities applicable to the subleased property. In December 2016, we entered into a new sublease, or the New Sublease, with Wellspring for 5,216 square feet of office space located on Science Park Road in San Diego, California for a monthly rent of approximately $16,000 per month and security deposit of approximately $16,000. The New Sublease includes rent escalation of 3.0% per year. In addition to the base monthly rent, we will be obligated to pay for operating costs, amenities fees and all other costs applicable to the subleased property. The terms of the new sublease will commence on the later of (i) June 1, 2017 or (ii) the date on which Wellspring’s landlord delivers certain premises under Wellspring’s master lease to Wellspring with certain improvements substantially completed. The New Sublease will expire on October 31, 2019. In August 2015, we entered into a lease agreement for approximately 3,766 square feet of office space located in Cambridge, Massachusetts. We paid a security deposit of approximately $44,000. The lease is subject to a 60 month term expiring on August 1, 2020, with initial monthly rent of approximately $21,000 per month, and subject to a 1.4% annual rent increase. Total base rent payable over the lease period is $1.3 million. In addition to base monthly rent, we are obligated to pay for taxes, insurance and utilities applicable to the leased property. Future minimum payments required under the facility leases as of December 31, 2016 are summarized as follows, in thousands: Year Ending December 31, 2017 $ 406 2018 461 2019 436 2020 159 Total future minimum lease payments $ 1,462 Rent expense for the years ended December 31, 2016 and 2015 was $342,000 and $267,000, respectively. Charitable Gift We are obligated to make a charitable gift of $285,000 to the Leukemia and Lymphoma Society in connection with the University of Michigan agreement described in Note 10 to be paid in three equal parts: the first part was due and paid in January 2015, the second part was due and paid in January 2016 and the final part was due and paid in January 2017. As of December 31, 2016, $95,000 was included in accounts payable and accrued expenses on the balance sheets. As of December 31, 2015, $95,000 was included in accounts payable and accrued expenses and $95,000 in other long-term liabilities on the balance sheets. Litigation From time to time, we may be involved in disputes, including litigation, relating to claims arising out of operations in the normal course of our business. Any of these claims could subject us to costly legal expenses and, while we generally believe that we have adequate insurance to cover many different types of liabilities, our insurance carriers may deny coverage or our policy limits may be inadequate to fully satisfy any damage awards or settlements. If this were to happen, the payment of any such awards could have a material adverse effect on our results of operations and financial position. Additionally, any such claims, whether or not successful, could damage our reputation and business. We currently are not a party to any legal proceedings, the adverse outcome of which, in management’s opinion, individually or in the aggregate, would have a material adverse effect on our results of operations or financial position.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Stockholders' Equity	12. Stockholders’ Equity Immediately prior to the Merger, on March 6, 2015, Prior Kura sold an aggregate of 9,485,566 shares of its common stock at a price of $6.32 per share, for net proceeds of approximately $55.8 million, net of $4.1 million in fees. The Private Placement represented a qualified financing conversion event pursuant to Prior Kura’s then outstanding convertible promissory notes. As such, upon the closing of the Private Placement, an aggregate of $7.5 million in principal under such convertible promissory notes and $115,000 in accrued interest through February 28, 2015 automatically converted into 1,204,870 shares of our common stock (which shares and net proceeds are included in the amounts set forth above). In addition, we incurred approximately $568,000 in costs related to the Merger which were accounted for as financing costs in additional paid-in capital. In November 2015, we completed a public offering in which we sold an aggregate of 6,883,467 shares of common stock at a price of $8.00 per share. Net proceeds from the public offering, after deducting underwriting discounts, commissions and offering expenses, were approximately $50.3 million.

Equity Incentive Plan

Equity Incentive Plan	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Incentive Plan	13. Equity Incentive Plan Under our Amended and Restated The number of shares available for future grant under our 2014 Plan will automatically increase on January 1 of each year by 4% of the total number of shares of our common stock outstanding on December 31 of the preceding calendar year, subject to the ability of our board of directors to take action to reduce the size of the increase in any given year. On January 1, 2016 and 2017, an automatic increase pursuant to the 2014 Plan occurred, resulting in 854,822 and 854,709 additional shares available for future grant under the 2014 Plan, respectively. In addition, as of December 31, 2016, we had 238,705 shares of common stock reserved for future issuance under our 2015 Employee Stock Purchase Plan, or ESPP, which has not been implemented as of December 31, 2016. The number of shares of our common stock reserved for issuance under the ESPP will automatically increase on January 1 of each calendar year by the lesser of 1% of the total number of shares of our common stock outstanding on December 31 of the preceding calendar year and 2,000,000 shares, subject to the ability of our board of directors to take action to reduce the size of the increase in any given year. Stock Options The exercise price of all stock options granted was equal to no less than the estimated fair market value of such stock on the date of grant. Stock options generally vest over a three to four-year period. The maximum contractual term for all options is ten years. The following is a summary of stock option activity for the year ended December 31, 2016, in thousands (except per share and years data): Number of Shares Weighted-Average Exercise Price per Share Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at December 31, 2015 574 $ 9.10 Granted 703 $ 4.72 Canceled/forfeited (75 ) $ 11.64 Outstanding at December 31, 2016 1,202 $ 6.38 8.9 $ 840 Exercisable at December 31, 2016 331 $ 6.92 8.7 $ 148 The assumptions used to estimate the fair value of stock options granted to employees in the years ended December 31, 2016 and 2015 using the Black-Scholes model were as follows: Years Ended December 31, 2016 2015 Weighted-average grant date fair value per share $ 3.09 $ 4.16 Expected volatility 73.8% — 76.6% 70.8% — 72.8% Expected term (in years) 5.50 — 6.08 6.00 — 6.08 Risk free interest rate 1.5% — 1.7% 1.7% — 1.8% Expected dividend yield — — In estimating fair value for stock options issued under the 2014 Plan, expected volatility was based on historical volatility of comparable publicly-traded companies because our common stock has only been publicly traded since September 16, 2015. Due to the lack of historical option exercise data, we estimated the expected term using the simplified method. The risk-free interest rates are based on the U.S. Treasury zero-coupon bonds with maturities similar to those of the expected term of the award being valued. The expected dividend yield of zero reflects that we have not paid cash dividends since inception and do not intend to pay cash dividends in the foreseeable future. We adopted ASU 2016-09 in 2016, and as a result, apply actual forfeitures as they occur. For the years ended December 31, 2016 and 2015, we recognized $1.1 million and $399,000 expense related to options, respectively. As of December 31, 2016, unrecognized estimated compensation expense related to options was $2.7 million, which is expected to be recognized over the weighted-average remaining requisite service period of approximately 2.7 years. Restricted Stock Awards Restricted stock awards were granted at a price equal to the estimated fair market value on the date of grant. The restricted stock awards generally vest over four years from the original vesting date, with certain grants subject to one-year cliff vesting. The vesting provisions of individual awards may vary as approved by our board of directors. In connection with the issuance of restricted common stock, we maintain a repurchase right where shares of restricted common stock are released from such repurchase right over a period of time of continued service by the recipient. The repurchase price for unvested stock awards will be the lower of (i) the fair market value of the shares of common stock on the date of repurchase or (ii) their original purchase price. As of December 31, 2016, there were 2,020,266 The following is a summary of restricted stock awards activity for the year ended December 31, 2016, in thousands (except per share data): Number Shares Employee Non-employee Weighted-Average Grant Date Fair Value of Employee Awards Unvested at December 31, 2015 3,233 2,717 516 $ 0.002 Granted — — — $ — Vested (1,210 ) (1,017 ) (193 ) $ 0.002 Forfeited (3 ) (3 ) — $ 0.002 Unvested at December 31, 2016 2,020 1,697 323 $ 0.002 Vested at December 31, 2016 2,899 2,375 524 $ 0.002 For the years ended December 31, 2016 and 2015, we recognized expense related to restricted stock awards totaling $1.0 million and $1.9 million, respectively, of which $856,000 and $1.7 million in expense related to non-employee restricted stock awards, respectively. As of December 31, 2016, unrecognized estimated compensation expense related to employee restricted stock awards was $227,000, which is expected to be recognized over the weighted-average remaining requisite service period of approximately 1.7 years. The following table summarizes share-based compensation expense for all share-based compensation arrangements, in thousands: Years Ended December 31, 2016 2015 Research and development $ 1,293 $ 1,916 General and administrative 796 343 Total share-based compensation expense $ 2,089 $ 2,259

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
Related Party Transactions	14. Related Party Transactions In January 2015, we entered into a Note Purchase Agreement and Convertible Promissory Note for a $3.0 million loan with various persons and entities named within the agreement, of which $710,000 were with certain officers and certain officers’ related parties. In connection with the Private Placement, the total amount of unpaid principal and accrued interest as of February 28, 2015 under the notes was automatically converted into 479,667 shares of our common stock. Our president and chief executive officer is also the sole managing member of our affiliated company Araxes. Four individuals are significant stockholders of each of us and Araxes. The following is a summary of transactions with Araxes for the years ended December 31, 2016 and 2015: • Asset Purchase Agreement Under our asset purchase agreement with Araxes, we paid a $100,000 milestone payment to Araxes upon the filing of the IND for KO-947 in the fourth quarter of 2016. • Convertible Promissory Notes In connection with the Private Placement, the total amount of unpaid principal and accrued interest as of February 28, 2015 under a convertible note issued to Araxes in connection with (i) the Araxes asset purchase was automatically converted into 80,293 shares of our common stock and (ii) an Araxes $2.0 million loan was automatically converted into 326,443 shares of our common stock. • Facility Sublease We sublease office space in La Jolla, California from Wellspring. Rent expense related to the Sublease for the years ended December 31, 2016 and 2015 was $65,000 and $58,000, respectively. Pursuant to the terms of the Sublease, as amended in June 2016, the Sublease would have expired on October 31, 2019. In December 2016, we entered into a third amendment to Sublease pursuant to which the Sublease will expire on the later of (i) June 8, 2017 or (ii) seven days after the date on which Wellspring’s landlord delivers the premises to Wellspring. In December 2016, we entered into the New Sublease with Wellspring for office space in San Diego, California. The terms of the New Sublease will commence on the later of (i) June 1, 2017 or (ii) the date on which Wellspring’s landlord delivers the premises subject to Wellspring’s master lease to Wellspring with certain improvements substantially completed. The New Sublease will expire on October 31, 2019. See Note 11, Commitments and Contingencies, for further details of the terms of the Sublease and New Sublease. • Management Fees We have a management services agreement with Araxes pursuant to which Araxes pays us a fixed fee of $65,000 per month for management services. In addition, the agreement allows for Araxes to reimburse us an amount equal to the number of full time equivalents, or FTE, performing research and development services for Araxes, at an annual FTE rate of approximately $350,000, plus actual expenses as reasonably incurred. The initial term of this agreement expired on December 31, 2015 but, pursuant to the terms of the agreement, renews automatically for additional consecutive one-year periods. The agreement may be terminated by either party with a notice of at least 30 days prior to the expiration of the then-renewal term. For the years ended December 31, 2016 and 2015, we recorded reimbursements of $358,000 and $330,000, respectively, for research and development services provided to Araxes, which was recorded as a reduction to research and development expenses on the statements of operations and comprehensive loss. As of December 31, 2016 and 2015, $295,000 and $430,000 related to management fees and reimbursements of research and development services, respectively, are included in accounts receivable, related party on the balance sheets. • Services Agreement We have a services agreement with Wellspring which allows for payment of research and development services provided to us of an amount equal to the number of FTE’s performing the services, at an annual FTE rate of $400,000, plus actual expenses as reasonably incurred. The initial term of this services agreement expired on December 31, 2015 but, pursuant to the terms of the agreement, renews automatically for additional consecutive one-year periods. The agreement may be terminated by either party with a notice of at least 30 days prior to the expiration of the then-renewal term. For the years ended December 31, 2016 and 2015, we recognized $4.0 million and $4.1 million, respectively, from research and development services provided to us under this agreement as research and development expense, related party on the statements of operations and comprehensive loss. As of December 31, 2016 and 2015, $770,000 and $911,000, respectively, related to research and development services under this agreement are included in accounts payable and accrued expenses, related party on the balance sheets.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2016
Postemployment Benefits [Abstract]
Employee Benefit Plan	15. Employee Benefit Plan We have a defined contribution 401(k) plan for all employees. Under the terms of the plan, employees may make voluntary contributions as a percentage or defined amount of compensation. We did not provide a matching contribution program in 2015. Beginning in 2016, we provide a safe harbor contribution of 3.0% of the employee’s compensation, not to exceed eligible limits. For the year ended December 31, 2016, we incurred $176,000 in expenses related to the safe harbor contribution.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	16. Income Taxes We file tax returns as prescribed by the tax laws of the jurisdictions in which we operate. In the normal course of business, our 2014 through 2016 tax years will be subject to examination by the federal and state jurisdictions where applicable. We have not been, nor are we currently, under examination by the federal or any state tax authority. Our effective income tax rate differs from the statutory federal rate of 34% for the years ended December 31, 2016 and 2015, due to the following, in thousands: Years Ended December 31, 2016 2015 Income taxes at statutory federal rate $ (9,370 ) $ (7,693 ) State income tax, net of federal benefit (1,823 ) (1,412 ) Share-based compensation 564 712 Research and development tax credits (560 ) (544 ) Other 50 29 Valuation allowance 11,139 8,908 Income tax expense $ — $ — Significant components of our deferred tax assets at December 31, 2016 and 2015 are shown below, in thousands: December 31, 2016 2015 Deferred tax assets Net operating loss carryforwards $ 18,321 $ 7,975 Intangibles 982 999 Research and development tax credit carryforwards 971 573 Accruals 809 662 Other 371 106 Total deferred tax assets 21,454 10,315 Less valuation allowance (21,454 ) (10,315 ) Net deferred tax assets $ — $ — At December 31, 2016, we had federal and state net operating loss, or NOL, carryforwa rds of $44.8 million and $54.4 million, respe begin to expire in 2034, unless previously utilized. We have $54.1 million of state losses that begin to expire in 2034 and $310,000 of state loss carryforwards that begin to expire in 2030, unless previously utilized. We also have federal and state research and development credit carryforwards of $857,000 (net of $250,000 to be utilized as a payroll tax offset) and $629,000, respectively research and development expire in 2034, unless previously research and development research and development Management assesses the available positive and negative evidence to estimate if sufficient future taxable income will be generated to use existing deferred tax assets. Based on the weight of the evidence, including our limited existence and losses since inception, management has determined that it is more likely than not that the deferred tax assets will not be realized. The valuation allowance increased by $11.1 million and $8.9 million from December 31, 2015 to Pursuant to Sections 382 and 383 of the IRC annual use of our NOL or research and development credit carryforwards may be limited in the event a cumulative change in ownership of more than 50% occurs within a three-year period. We completed a study to assess whether an ownership change, as defined by IRC Section 382, had occurred from our formation through March 31, 2016. Based upon the study, we determined that an ownership change occurred on March 6, 2015 concurrent with the Private Placement and the Merger. The analysis concluded the annual utilization limitation will be sufficient to utilize our pre-ownership change NOLs and research and development credits prior to expiration. Future ownership changes may limit our ability to utilize remaining tax attributes. Any carryforwards that will expire prior to utilization as a result of such additional limitations will be removed from deferred tax assets, with a corresponding reduction of the valuation allowance. In accordance with authoritative guidance, the impact of an uncertain income tax position is recognized at the largest amount that is “more likely than not” to be sustained upon audit by the relevant taxing authority. An uncertain tax position will not be recognized if it has less than a 50% likelihood of being sustained. The following table summarizes the activity related to our unrecognized tax benefits, in thousands: December 31, 2016 2015 Gross unrecognized tax benefits at the beginning of the year $ 167 $ — Increases from tax positions taken in the current year 191 167 Gross unrecognized tax benefits at the end of the year $ 358 $ 167 Our practice is to recognize interest and penalties related to income tax matters in income tax expense. We did not have any accrued interest or penalties included on the balance sheets and have not recognized interest and penalties on the statements of operations and comprehensive loss for the years ended December 31, 2016 or 2015. We do not expect that there will be a significant change in the unrecognized tax benefits over the next 12 months. Due to the existence of the valuation allowance, future changes in our unrecognized tax benefits will not impact our effective tax rate.

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Event	17. Subsequent Event Entry into ATM Facility On January 27, 2017, we entered into an at the market issuance sales agreement, or ATM agreement, with Cowen and Company, LLC, or Cowen, under which we may offer and sell, from time to time, in our sole discretion, shares of our common stock having an aggregate offering price of up to $25.0 million through Cowen as our sales agent, or the ATM facility. Cowen may sell common stock under the ATM facility by any method permitted by law deemed to be an “at the market offering” as defined in Rule 415 of the Securities Act of 1933, as amended, We are not obligated to make any sales of common stock under the ATM facility. The offering of shares of common stock pursuant to the ATM facility will terminate upon the earlier of (i) the sale of all common stock subject to the ATM facility, or (ii) termination of the ATM agreement in accordance with its terms.

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates Our financial statements are prepared in accordance with accounting principles generally accepted in the United States. The preparation of our financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Reported amounts and note disclosures reflect the overall economic conditions that are most likely to occur and anticipated measures management intends to take. Actual results could differ materially from those estimates. All revisions to accounting estimates are recognized in the period in which the estimates are revised and in any future periods affected.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. We operate in a single industry segment which is the discovery and development of precision medicines for the treatment of cancer. Our chief operating decision-maker reviews the operating results on an aggregate basis and manages the operations as a single operating segment.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of checking, money market and highly liquid investments that are readily convertible to cash and that mature within three months or less from the date of purchase. The carrying amounts approximate fair value due to the short maturities of these instruments.
Short-Term Investments	Short-Term Investments Short-term investments are marketable securities with maturities greater than three months from date of purchase that are specifically identified to fund current operations. These investments are classified as current assets, even though the stated maturity date may be one year or more beyond the current balance sheet date, which reflects management’s intention to use the proceeds from sales of these securities to fund our operations, as necessary. The cost of short-term investments is adjusted for amortization of premiums or accretion of discounts to maturity, and such amortization or accretion is included in interest income. Dividend and interest income is recognized as interest income on the statements of operations and comprehensive loss when earned. Short-term investments are classified as available-for-sale securities and carried at fair value with unrealized gains and losses recorded in other comprehensive loss and included as a separate component of stockholders' equity. Realized gains and losses from the sale of available-for-sale securities and declines in value judged to be other than temporary on short-term investments, if any, are determined on a specific identification basis and are reclassified out of comprehensive loss and included in interest income on the statements of operations and comprehensive loss.
Fair Value Measurements	Fair Value Measurements Fair value is defined as the exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: • Level 1 - Quoted prices (unadjusted) in active markets for identical assets or liabilities; • Level 2 - Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable; • Level 3 - Unobservable inputs in which little or no market activity exists, therefore requiring an entity to develop its own assumptions about the assumptions that market participants would use in pricing.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject us to significant concentrations of credit risk consist primarily of cash, cash equivalents and short-term investments. We maintain deposits in federally insured financial institutions in excess of federally insured limits. We have established guidelines to limit our exposure to credit risk by placing investments with high credit quality financial institutions, diversifying our investment portfolio and placing investments with maturities that maintain safety and liquidity.
Property and Equipment	Property and Equipment Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets which is three years for each asset class.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets We review our long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. If such circumstances are determined to exist, an estimate of undiscounted future cash flows produced by the long-lived asset, including its eventual residual value, is compared to the carrying value to determine whether impairment exists. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their estimated fair values. While our current and historical operating losses and negative cash flows are indicators of impairment, we believe that future cash flows to be received support the carrying value of our long-lived assets and, accordingly, have not recognized any impairment losses through December 31, 2016.
Research and Development Expenses	Research and Development Expenses Research and development expenses consist of costs associated with our research activities including salaries, benefits, share-based compensation and other personnel costs, clinical trial costs, preclinical study fees, manufacturing costs for non-commercial products, costs for the development of our earlier-stage programs and research supply, equipment and facility costs. All such costs are charged to research and development expense as incurred when these expenditures have no alternative future uses. We are obligated to make upfront payments upon execution of certain research and development agreements. Advance payments, including nonrefundable amounts, for goods or services that will be used or rendered for future research and development activities are deferred. Such amounts are recognized as expense as the related goods are delivered or the related services are performed or such time when we do not expect the goods to be delivered or services to be performed. Payments that we make in connection with in-licensed technology for a particular research and development project that have no alternative future uses (in other research and development projects or otherwise) and therefore no separate economic values are expensed as research and development costs at the time such costs are incurred. As of December 31, 2016, we have no in-licensed technologies that have alternative future uses in research and development projects or otherwise.
Clinical Trial Costs and Accruals	Clinical Trial Costs and Accruals A significant portion of our clinical trial costs relate to contracts with contract research organizations, or CROs. The financial terms of our CRO contracts may result in payment flows that do not match the periods over which materials or services are provided to us under such contracts. Our objective is to reflect the appropriate clinical trial expenses in our financial statements by matching those expenses with the period in which services and efforts are expended. As part of the process of preparing our financial statements, we rely on cost information provided by our CROs (concerning monthly expenses as well as reimbursement for pass through costs). We are also required to estimate certain of our expenses resulting from our obligations under our CRO contracts. Accordingly, our clinical trial accrual is dependent upon the timely and accurate reporting of CROs and other third-party vendors. If the contracted amounts are modified (for instance, as a result of changes in the clinical trial protocol or scope of work to be performed), we modify our accruals accordingly on a prospective basis. Revisions in the scope of a contract are charged to expense in the period in which the facts that give rise to the revision become reasonably certain. Historically, we have had no material changes in clinical trial expense that had a material impact on our results of operations or financial position.
Patent Costs	Patent Costs We expense all costs as incurred in connection with patent applications, including direct application fees, and the legal and consulting expenses related to making such applications, and such costs are included in general and administrative expenses on the statements of operations and comprehensive loss.
Share-Based Payments	Share-Based Payments Our share-based awards are measured at fair value on the date of grant based upon the estimated fair value of common stock. The fair value of awards expected to vest are recognized and amortized on a straight-line basis over the requisite service period of the award less actual forfeitures. The fair value of each stock option is estimated on the date of grant using the Black-Scholes option pricing model, or Black-Scholes model, that requires the use of subjective assumptions including volatility, expected term, risk-free rate and the fair value of the underlying common stock. Awards granted to non-employees are subject to periodic revaluation over their vesting terms. The fair value of non-employee awards is remeasured at each reporting period as the underlying awards vest unless the instruments are fully vested, immediately exercisable and nonforfeitable on the date of grant. We record the expense for stock option grants to non-employees based on the estimated fair value of the stock options using the Black-Scholes model. Estimated fair value of the restricted stock awards granted to non-employees is recorded on the earlier of the performance commitment date or the date the services required are completed and are remeasured at fair value during the service period. As non-employee restricted stock awards vest, they are remeasured at fair value and expensed based on the intrinsic value method which is measured as the difference between the exercise price paid for the restricted stock award and the fair value of the shares as the right of the repurchase lapses each vesting period.
Income Taxes	Income Taxes Income taxes are accounted for using the asset and liability method. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates applicable to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance against deferred tax assets is recorded if, based upon the weight of all available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. For uncertain tax positions that meet “a more likely than not” threshold, we recognize the benefit of uncertain tax positions in the financial statements.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) is defined as the change in equity during the period from transactions and other events and non-owner sources. For the periods presented, accumulated other comprehensive income (loss) consists solely of unrealized gains and losses on marketable securities.
Net Loss per Share	Net Loss per Share Net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by dividing the net loss by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. Dilutive common stock equivalents are comprised of unvested restricted stock awards, outstanding stock options and outstanding warrants. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to the antidilutive effect of the securities. Because of our net loss, unvested restricted stock awards, outstanding stock options and outstanding warrants are excluded from the calculation of diluted net loss per common share for the years ended December 31, 2016 and 2015, due to the anti-dilutive effect of the securities. The following table summarizes the number of potentially dilutive securities that were excluded from our calculation of diluted net loss per share for the years ended December 31, 2016 and 2015: Years Ended December 31, 2016 2015 Unvested restricted stock awards 2,020,266 3,232,350 Stock options 1,201,591 574,312 Warrants 67,976 — Total 3,289,833 3,806,662
Recent Accounting Pronouncements	In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2014-09, Revenue from Contracts with Customers (Topic 606), that supersedes most current revenue recognition guidance, including industry-specific guidance. The guidance provides that an entity recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This guidance also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments, and assets recognized from costs incurred to obtain or fulfill a contract. In July 2015, the FASB voted to amend ASU 2014-09 by approving a one-year deferral of the effective date as well as providing the option to early adopt the standard on the original effective date. Accordingly, we will adopt the standard in the first quarter of 2018. We plan to adopt the accounting standard using the modified retrospective transition approach. The modified retrospective transition approach will recognize any changes from the beginning of the year of initial application through retailed earnings with no restatement of comparative periods. We currently do not have any revenue contracts with customers and will review any new contracts entered into prior to the adoption of the new standard. The adoption of this guidance is not expected to have an impact on our financial statements. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires lessees to recognize a right-to-use asset and a lease obligation for all leases. Lessees are permitted to make an accounting policy election to not recognize an asset and liability for leases with a term of 12 months or less. Lessor accounting under the new standard is substantially unchanged. Additional qualitative and quantitative disclosures, including significant judgments made by management, will be required.

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of Number of Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share	The following table summarizes the number of potentially dilutive securities that were excluded from our calculation of diluted net loss per share for the years ended December 31, 2016 and 2015: Years Ended December 31, 2016 2015 Unvested restricted stock awards 2,020,266 3,232,350 Stock options 1,201,591 574,312 Warrants 67,976 — Total 3,289,833 3,806,662

Investments (Tables)

Investments (Tables)	12 Months Ended
	Dec. 31, 2016
Investments All Other Investments [Abstract]
Investments Measured at Fair Value on Recurring Basis	The following tables summarize, by major security type, our investments that are measured at fair value on a recurring basis as of December 31, 2016 and 2015, in thousands: As of December 31, 2016 Maturities (years) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents: Money market funds 1 or less $ 5,762 $ — $ — $ 5,762 Commercial paper 1 or less 2,000 — — 2,000 Total cash equivalents 7,762 — — 7,762 Short-term investments: U.S. Treasury securities 2 or less 28,006 5 (9 ) 28,002 Commercial paper 1 or less 14,273 — — 14,273 Corporate debt securities 2 or less 13,603 — (14 ) 13,589 Government sponsored enterprise securities 1 or less 2,201 — — 2,201 Total short-term investments 58,083 5 (23 ) 58,065 Total $ 65,845 $ 5 $ (23 ) $ 65,827 As of December 31, 2015 Maturities (years) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents: Money market funds 1 or less $ 12,984 $ — $ — $ 12,984 Short-term investments: U.S. Treasury securities 2 or less 16,007 — (18 ) 15,989 Commercial paper 1 or less 18,367 — — 18,367 Corporate debt securities 2 or less 22,758 — (48 ) 22,710 Government sponsored enterprise securities 2 or less 13,258 — (21 ) 13,237 Total short-term investments 70,390 — (87 ) 70,303 Total $ 83,374 $ — $ (87 ) $ 83,287

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Schedule Of Fair Value Measurements, By Major Security Type	The following tables summarize, by major security type, our cash equivalents and short-term investments that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy as of December 31, 2016 and 2015, in thousands: As of December 31, 2016 Balance Level 1 Level 2 Cash equivalents: Money market funds $ 5,762 $ 5,762 $ — Commercial paper 2,000 — 2,000 Total cash equivalents 7,762 5,762 2,000 Short-term investments: U.S. Treasury securities 28,002 28,002 — Commercial paper 14,273 — 14,273 Corporate debt securities 13,589 — 13,589 Government sponsored enterprise securities 2,201 — 2,201 Total short-term investments 58,065 28,002 30,063 Total $ 65,827 $ 33,764 $ 32,063 As of December 31, 2015 Balance Level 1 Level 2 Cash equivalents: Money market funds $ 12,984 $ 12,984 $ — Short-term investments: U.S. Treasury securities 15,989 15,989 — Commercial paper 18,367 — 18,367 Corporate debt securities 22,710 — 22,710 Government sponsored enterprise securities 13,237 — 13,237 Total short-term investments 70,303 15,989 54,314 Total $ 83,287 $ 28,973 $ 54,314

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Property and Equipment, Net	Property and equipment consisted of the following, in thousands: December 31, 2016 2015 Computer equipment $ 85 $ 85 Software 7 7 Property and equipment, gross 92 92 Less: accumulated depreciation (52 ) (21 ) Property and equipment, net $ 40 $ 71

Accounts Payable and Accrued 29

Accounts Payable and Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2016
Payables And Accruals [Abstract]
Accounts Payable and Accrued Liabilities	Accounts payable and accrued liabilities consisted of the following, in thousands: December 31, 2016 2015 Accounts payable $ 638 $ 902 Accrued compensation and benefits 1,907 1,282 Other accrued expenses 2,136 1,934 Total accounts payable and accrued expenses $ 4,681 $ 4,118

Long-Term Debt (Tables)

Long-Term Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Future Minimum Payments under Term Loan Facility	The following table summarizes future minimum payments under the term loan facility as of December 31, 2016, in thousands: Year Ending December 31, 2017 $ 607 2018 2,323 2019 3,355 2020 3,424 Total future minimum payments 9,709 Less: interest payments (2,209 ) Principal amount of long-term debt 7,500 Less: Unamortized discount (176 ) Long-term debt, net of unamortized discount 7,324 Current portion of long-term debt — Long-term debt, net $ 7,324

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Payments Required under Facility Leases	Future minimum payments required under the facility leases as of December 31, 2016 are summarized as follows, in thousands: Year Ending December 31, 2017 $ 406 2018 461 2019 436 2020 159 Total future minimum lease payments $ 1,462

Equity Incentive Plan (Tables)

Equity Incentive Plan (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activities	The exercise price of all stock options granted was equal to no less than the estimated fair market value of such stock on the date of grant. Stock options generally vest over a three to four-year period. The maximum contractual term for all options is ten years. The following is a summary of stock option activity for the year ended December 31, 2016, in thousands (except per share and years data): Number of Shares Weighted-Average Exercise Price per Share Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at December 31, 2015 574 $ 9.10 Granted 703 $ 4.72 Canceled/forfeited (75 ) $ 11.64 Outstanding at December 31, 2016 1,202 $ 6.38 8.9 $ 840 Exercisable at December 31, 2016 331 $ 6.92 8.7 $ 148
Summary of Assumptions used to Estimate the Fair Value of Stock Options Under Black-Scholes Model	The assumptions used to estimate the fair value of stock options granted to employees in the years ended December 31, 2016 and 2015 using the Black-Scholes model were as follows: Years Ended December 31, 2016 2015 Weighted-average grant date fair value per share $ 3.09 $ 4.16 Expected volatility 73.8% — 76.6% 70.8% — 72.8% Expected term (in years) 5.50 — 6.08 6.00 — 6.08 Risk free interest rate 1.5% — 1.7% 1.7% — 1.8% Expected dividend yield — —
Summary of Restricted Stock Awards Activity	The following is a summary of restricted stock awards activity for the year ended December 31, 2016, in thousands (except per share data): Number Shares Employee Non-employee Weighted-Average Grant Date Fair Value of Employee Awards Unvested at December 31, 2015 3,233 2,717 516 $ 0.002 Granted — — — $ — Vested (1,210 ) (1,017 ) (193 ) $ 0.002 Forfeited (3 ) (3 ) — $ 0.002 Unvested at December 31, 2016 2,020 1,697 323 $ 0.002 Vested at December 31, 2016 2,899 2,375 524 $ 0.002
Summary of Share-based Compensation Expense	The following table summarizes share-based compensation expense for all share-based compensation arrangements, in thousands: Years Ended December 31, 2016 2015 Research and development $ 1,293 $ 1,916 General and administrative 796 343 Total share-based compensation expense $ 2,089 $ 2,259

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	Our effective income tax rate differs from the statutory federal rate of 34% for the years ended December 31, 2016 and 2015, due to the following, in thousands: Years Ended December 31, 2016 2015 Income taxes at statutory federal rate $ (9,370 ) $ (7,693 ) State income tax, net of federal benefit (1,823 ) (1,412 ) Share-based compensation 564 712 Research and development tax credits (560 ) (544 ) Other 50 29 Valuation allowance 11,139 8,908 Income tax expense $ — $ —
Components of Deferred Tax Assets	Significant components of our deferred tax assets at December 31, 2016 and 2015 are shown below, in thousands: December 31, 2016 2015 Deferred tax assets Net operating loss carryforwards $ 18,321 $ 7,975 Intangibles 982 999 Research and development tax credit carryforwards 971 573 Accruals 809 662 Other 371 106 Total deferred tax assets 21,454 10,315 Less valuation allowance (21,454 ) (10,315 ) Net deferred tax assets $ — $ —
Schedule of Activity Related to Unrecognized Tax Benefits	The following table summarizes the activity related to our unrecognized tax benefits, in thousands: December 31, 2016 2015 Gross unrecognized tax benefits at the beginning of the year $ 167 $ — Increases from tax positions taken in the current year 191 167 Gross unrecognized tax benefits at the end of the year $ 358 $ 167

Organization and Basis of Pre34

Organization and Basis of Presentation - Additional Information (Detail) - USD ($)	Nov. 05, 2015	Mar. 06, 2015	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2016
Product Information [Line Items]
Common stock, shares issued		14,508,177	21,371,000	21,371,000	21,368,000
Common stock, shares issued	6,883,467
Common stock, issued price per share	$ 8
Proceeds from issuance of common stock, net			$ 50,300,000	$ 97,870,000
Private Placement
Product Information [Line Items]
Common stock, shares issued		9,485,566
Common stock, issued price per share		$ 6.32
Proceeds from issuance of common stock, net		$ 55,800,000
Convertible promissory notes accrued interest		115,000
Conversion of common stock		$ 7,500,000

Summary of Significant Accoun35

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)Segment
Accounting Policies [Abstract]
Number of operating segments | Segment	1
Property and equipment, estimated useful life	3 years
Impairment losses on long-lived assets | $	$ 0

Summary of Significant Accoun36

Summary of Significant Accounting Policies - Summary of Number of Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	3,289,833	3,806,662
Unvested Restricted Stock Awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	2,020,266	3,232,350
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	1,201,591	574,312
Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	67,976

Investments - Investments Measu

Investments - Investments Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Short-term investments	$ 58,065	$ 70,303
Fair Value Measurements on Recurring Basis
Schedule Of Available For Sale Securities [Line Items]
Cash equivalents, Amortized Cost	7,762
Cash equivalents, Fair Value	7,762
Short-term investments, Amortized Cost	58,083	70,390
Short-term investments, Unrealized Gains	5
Short-term investments, Unrealized Losses	(23)	(87)
Short-term investments	58,065	70,303
Cash equivalents and Short-term investments, Amortized Cost	65,845	83,374
Cash equivalents and Short-term investments, Fair Value	$ 65,827	$ 83,287
Fair Value Measurements on Recurring Basis | Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Maturities (years)	1 or less	1 or less
Cash equivalents, Amortized Cost	$ 5,762	$ 12,984
Cash equivalents, Fair Value	$ 5,762	$ 12,984
Fair Value Measurements on Recurring Basis | Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Maturities (years)	1 or less	1 or less
Cash equivalents, Amortized Cost	$ 2,000
Cash equivalents, Fair Value	2,000
Short-term investments, Amortized Cost	14,273	$ 18,367
Short-term investments	$ 14,273	$ 18,367
Fair Value Measurements on Recurring Basis | U.S. Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Maturities (years)	2 or less	2 or less
Short-term investments, Amortized Cost	$ 28,006	$ 16,007
Short-term investments, Unrealized Gains	5
Short-term investments, Unrealized Losses	(9)	(18)
Short-term investments	$ 28,002	$ 15,989
Fair Value Measurements on Recurring Basis | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturities (years)	2 or less	2 or less
Short-term investments, Amortized Cost	$ 13,603	$ 22,758
Short-term investments, Unrealized Losses	(14)	(48)
Short-term investments	$ 13,589	$ 22,710
Fair Value Measurements on Recurring Basis | Government Sponsored Enterprise Securities
Schedule Of Available For Sale Securities [Line Items]
Maturities (years)	1 or less	2 or less
Short-term investments, Amortized Cost	$ 2,201	$ 13,258
Short-term investments, Unrealized Losses		(21)
Short-term investments	$ 2,201	$ 13,237

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Investments All Other Investments [Abstract]
Short-term investments with maturities less than one year	$ 50,300,000	$ 57,600,000
Short-term investments with maturities between one to two years	7,800,000	12,700,000
Available-for-sale securities, realized gains or losses	0	0
Marketable securities gross unrealized loss positions for less than twelve months	$ 32,800,000	$ 51,900,000

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values of Investment Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 58,065	$ 70,303
Fair Value Measurements on Recurring Basis
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	7,762
Short-term investments	58,065	70,303
Cash equivalents and short-term investments	65,827	83,287
Fair Value Measurements on Recurring Basis | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	5,762	12,984
Fair Value Measurements on Recurring Basis | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	2,000
Short-term investments	14,273	18,367
Fair Value Measurements on Recurring Basis | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	28,002	15,989
Fair Value Measurements on Recurring Basis | Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	13,589	22,710
Fair Value Measurements on Recurring Basis | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	5,762
Short-term investments	28,002	15,989
Cash equivalents and short-term investments	33,764	28,973
Fair Value Measurements on Recurring Basis | Level 1 | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	5,762	12,984
Fair Value Measurements on Recurring Basis | Level 1 | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	28,002	15,989
Fair Value Measurements on Recurring Basis | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	2,000
Short-term investments	30,063	54,314
Cash equivalents and short-term investments	32,063	54,314
Fair Value Measurements on Recurring Basis | Level 2 | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	2,000
Short-term investments	14,273	18,367
Fair Value Measurements on Recurring Basis | Level 2 | Corporate Debt Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	13,589	22,710
Fair Value Measurements on Recurring Basis | Government Sponsored Enterprise Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	2,201	13,237
Fair Value Measurements on Recurring Basis | Government Sponsored Enterprise Securities | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 2,201	$ 13,237

Property and Equipment, Net (De

Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 92	$ 92
Less: accumulated depreciation	(52)	(21)
Property and equipment, net	40	71
Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	85	85
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 7	$ 7

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Depreciation expense	$ 31	$ 20

Accounts Payable and Accrued 42

Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Accounts payable	$ 638	$ 902
Accrued compensation and benefits	1,907	1,282
Other accrued expenses	2,136	1,934
Total accounts payable and accrued expenses	$ 4,681	$ 4,118

Long-Term Debt - Additional Inf

Long-Term Debt - Additional Information (Detail) - USD ($)	Apr. 27, 2016	Dec. 31, 2016
Debt Instrument [Line Items]
Maximum borrowing capacity under term loans	$ 20,000,000
Principal amount outstanding on loan		$ 7,500,000
Term loan remaining borrowing capacity	12,500,000
Additional borrowing description		We may, at our sole discretion, borrow up to an additional $12.5 million at any time between December 31, 2016 and May 1, 2017, or Term B Loan, and together with the Term A Loan, the Term Loans, subject to our successful advancement of KO-947, a small molecule inhibitor of extracellular signal regulated kinase, into Phase 1 clinical trials.
Term A Loan
Debt Instrument [Line Items]
Principal amount outstanding on loan	7,500,000
Final payment due on the maturity date	563,000
Fair Value Of Warrants	$ 172,000
Term A Loan | Term Loan Warrants
Debt Instrument [Line Items]
Warrants exercisable exercise price	$ 3.31
Warrants termination date		Apr. 27, 2026
Volatility Rate	70.92%
Expected Term	10 years
Risk Free Interest Rate	2.11%
Dividend yield	0.00%
Term A Loan | Maximum | Term Loan Warrants
Debt Instrument [Line Items]
Warrants issued to purchase of common stock	67,976
Term B Loan
Debt Instrument [Line Items]
Description of required debt amount		each Term B Loan must be in an amount equal to the lesser of $5.0 million or the amount that is remaining under the Term B Loan.
Term B Loan | Term Loan Warrants
Debt Instrument [Line Items]
Warrant shares percentage issued of loan amount	3.00%
Number of trading days for average closing price	10 days
Term B Loan | Minimum
Debt Instrument [Line Items]
Term B Loan Minimum draw amount	$ 5,000,000
Term Loans
Debt Instrument [Line Items]
Term loan facility maturity date	Nov. 1, 2020
Description of term loan payment terms		All of the Term Loans will mature on November 1, 2020, or Maturity Date. Repayment of the Term Loans is interest only through May 1, 2018, followed by 30 equal monthly payments of principal plus accrued interest commencing on June 1, 2018.
Percentage of prime rate included in effective interest rate	4.25%
Final payment as a percentage of amounts borrowed	7.50%
Team loan effective interest rate description		The per annum interest rate for any outstanding Term Loans is the greater of (i) 7.75% and (ii) the sum of (a) the prime rate reported in The Wall Street Journal on the last business day of the month that immediately precedes the month in which the interest will accrue, plus (b) 4.25%.
Unused fee description		unused fee on the earlier of May 2, 2017 or prior repayment of the Term Loans in an amount equal to (a) 2.00% multiplied by (b) $20.0 million minus the aggregate amount of the Term Loans drawn on or before May 1, 2017.
Term Loans | Base Rate
Debt Instrument [Line Items]
Commitment fee percentage on unused capacity	2.00%
Term Loans | Transaction Occurring Assumption One
Debt Instrument [Line Items]
Prepayment fee equal to outstanding principal amount	1.00%
Term Loans | Transaction Occurring Assumption Two
Debt Instrument [Line Items]
Prepayment fee equal to outstanding principal amount	2.00%
Term Loans | Transaction Occurring Assumption Three
Debt Instrument [Line Items]
Prepayment fee equal to outstanding principal amount	3.00%
Term Loans | Minimum | Base Rate
Debt Instrument [Line Items]
Minimum percentage of interest rate on outstanding borrowings	7.75%

Long-Term Debt - Future Minimum

Long-Term Debt - Future Minimum Payments under Term Loan Facility (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Debt Disclosure [Abstract]
2,017	$ 607
2,018	2,323
2,019	3,355
2,020	3,424
Total future minimum payments	9,709
Less: interest payments	(2,209)
Principal amount of long-term debt	7,500
Less: Unamortized discount	(176)
Long-term debt, net of unamortized discount	7,324
Long-term debt, net	$ 7,324

Notes Payable - Additional Info

Notes Payable - Additional Information (Detail) - USD ($)	Mar. 06, 2015	Feb. 11, 2015	Jan. 20, 2015	Jan. 12, 2015	Dec. 23, 2014	Oct. 08, 2014
Johnson & Johnson Innovation - JJDC, Inc
Debt Instrument [Line Items]
Convertible promissory note			$ 1,000,000
Unpaid principal and accrued interest converted into common stock shares	159,615
January 2015 Convertible Notes
Debt Instrument [Line Items]
Convertible promissory note				$ 3,000,000
Unpaid principal and accrued interest converted into common stock shares	479,667
February 2015 Convertible Notes
Debt Instrument [Line Items]
Convertible promissory note		$ 1,000,000
Unpaid principal and accrued interest converted into common stock shares	158,852
Araxes Asset Purchase Agreement
Debt Instrument [Line Items]
Convertible promissory note					$ 500,000
Unpaid principal and accrued interest converted into common stock shares	80,293
Araxes Pharma LLC
Debt Instrument [Line Items]
Convertible promissory note						$ 2,000,000
Unpaid principal and accrued interest converted into common stock shares	326,443
Certain Officers and Certain Officer's Related Parties | January 2015 Convertible Notes
Debt Instrument [Line Items]
Convertible promissory note				$ 710,000

License Agreements - Additional

License Agreements - Additional Information (Detail) - USD ($)	Mar. 06, 2015	Dec. 23, 2014	Dec. 22, 2014	Dec. 18, 2014	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
License Agreements [Line Items]
License agreements with Janssen, Michigan, and UCSF			$ 79,400,000
Araxes Asset Purchase Agreement
License Agreements [Line Items]
Convertible notes payable, related party		$ 500,000
Contingent Milestone Payables		9,700,000
Milestone payment paid					$ 100,000
Common Stock
License Agreements [Line Items]
Common stock, shares issued							79,000
The University of Michigan License Agreement
License Agreements [Line Items]
Agreement termination written notice			90 days
Agreement termination notice period in event of material breach			60 days
License agreement date			Dec. 22, 2014
Common stock, shares issued, Fair Value	$ 500,000
Agreement termination period due to payment failure			30 days
The University of Michigan License Agreement | Common Stock
License Agreements [Line Items]
Common stock, shares issued	79,113
The University of California San Francisco License Agreement
License Agreements [Line Items]
Indexed milestone paid						$ 464,000
License agreement termination description.						The license agreement with UCSF was terminated effective as of January 8, 2017.
Janssen License Agreement
License Agreements [Line Items]
Agreement termination written notice				180 days
Agreement termination notice period in event of material breach				45 days
Initiation of Certain Development Activities
License Agreements [Line Items]
License agreements with Janssen, Michigan, and UCSF			$ 425,000
Specified Regulatory Approvals
License Agreements [Line Items]
License agreements with Janssen, Michigan, and UCSF			28,200,000
Specified Levels of Product Sales
License Agreements [Line Items]
License agreements with Janssen, Michigan, and UCSF			$ 50,800,000
Initiation of Certain Development Activities | Araxes Asset Purchase Agreement
License Agreements [Line Items]
License agreements with Janssen, Michigan, and UCSF		8,500,000
Contingent Milestone Payables		$ 1,200,000
Up front Payment Arrangement | Janssen License Agreement
License Agreements [Line Items]
Upfront license expense				$ 1,000,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Aug. 01, 2015USD ($)ft²	Feb. 15, 2015USD ($)	Dec. 18, 2014	Dec. 31, 2016USD ($)ft²	Aug. 31, 2014USD ($)	Dec. 31, 2016USD ($)ft²	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Loss Contingencies [Line Items]
Rent expense						$ 342,000	$ 267,000
Accounts payable and accrued expenses for charitable gift				$ 4,681,000		4,681,000	4,118,000
Other non-current liabilities for charitable gift				$ 170,000		170,000	101,000
Cambridge, Massachusetts
Loss Contingencies [Line Items]
Operating lease, area of space | ft²	3,766
Security deposit	$ 44,000
Lease term period	60 months
Lease expiration date	Aug. 1, 2020
Office space lease monthly rent	$ 21,000
Operating lease rate of increase in annual rent	1.40%
Total base rent payable over the lease period	$ 1,300,000
Wellspring Biosciences Inc
Loss Contingencies [Line Items]
Research and development						4,000,000	4,100,000
Rent expense						$ 65,000	58,000
Wellspring Biosciences Inc | La Jolla, California
Loss Contingencies [Line Items]
Percentage of rent escalation					3.00%
Sublease expiration date			Oct. 31, 2019			Oct. 31, 2019
Sublease term description						In December 2016, we entered into a third amendment to Sublease pursuant to which the Sublease will expire on the later of (i) June 8, 2017 or (ii) seven days after the date on which Wellspring’s landlord delivers the new subleased premises to Wellspring
Wellspring Biosciences Inc | La Jolla, California | Monthly
Loss Contingencies [Line Items]
Rent expense					$ 4,820
Wellspring Biosciences Inc | San Diego, California
Loss Contingencies [Line Items]
Percentage of rent escalation				3.00%		3.00%
Sublease expiration date						Oct. 31, 2019
Sublease term description						The terms of the new sublease will commence on the later of (i) June 1, 2017 or (ii) the date on which Wellspring’s landlord delivers certain premises under Wellspring’s master lease to Wellspring with certain improvements substantially completed
Operating lease, area of space | ft²				5,216		5,216
Security deposit				$ 16,000		$ 16,000
Wellspring Biosciences Inc | San Diego, California | Monthly
Loss Contingencies [Line Items]
Rent expense				16,000
The University of Michigan Sponsored Research Agreement
Loss Contingencies [Line Items]
Sponsor of research over three- year		$ 2,700,000
Sponsored research agreement period		3 years
Research and development						$ 1,000,000	900,000
The University of Michigan License Agreement
Loss Contingencies [Line Items]
Commitment to provide charitable contribution								$ 285,000
Commitment to provide charitable contribution, description						We are obligated to make a charitable gift of $285,000 to the Leukemia and Lymphoma Society in connection with the University of Michigan agreement described in Note 10 to be paid in three equal parts: the first part was due and paid in January 2015, the second part was due and paid in January 2016 and the final part was due and paid in January 2017.
Accounts payable and accrued expenses for charitable gift				$ 95,000		$ 95,000	95,000
Other non-current liabilities for charitable gift							$ 95,000

Commitments and Contingencies48

Commitments and Contingencies - Future Minimum Payments Required under Facility Leases (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Leases [Abstract]
2,017	$ 406
2,018	461
2,019	436
2,020	159
Total future minimum lease payments	$ 1,462

Stockholder's Equity - Addition

Stockholder's Equity - Additional Information (Detail) - USD ($)	Nov. 05, 2015	Mar. 06, 2015	Dec. 31, 2015	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Common stock, shares issued	6,883,467
Common stock, issued price per share	$ 8
Proceeds from issuance of common stock, net			$ 50,300,000	$ 97,870,000
Common Stock
Stockholders' Equity Note [Abstract]
Common stock, shares issued				15,164,000
Private Placement
Stockholders' Equity Note [Abstract]
Common stock, shares issued		9,485,566
Common stock, issued price per share		$ 6.32
Financing fees		$ 4,100,000
Conversion of common stock		7,500,000
Convertible promissory notes accrued interest		115,000
Payments for merger related costs		568,000
Proceeds from issuance of common stock, net		$ 55,800,000
Private Placement | Common Stock
Stockholders' Equity Note [Abstract]
Conversion of convertible promissory notes and accrued interest, Shares		1,204,870

Equity Incentive Plan - Additio

Equity Incentive Plan - Additional Information (Detail) - USD ($)	Jan. 01, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 01, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense		$ 2,089,000	$ 2,259,000
Number of shares, subject to repurchase		2,020,000	3,233,000
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense		$ 1,100,000	$ 399,000
Unrecognized estimated stock option compensation expenses		$ 2,700,000
Weighted average service period		2 years 8 months 12 days
Restricted Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense		$ 1,000,000	1,900,000
Weighted average service period		1 year 8 months 12 days
Number of shares, subject to repurchase		1,697,556
Non-employee share based compensation expense		$ 856,000	$ 1,700,000
Unrecognized Expense		$ 227,000
Non Employee Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, subject to repurchase		322,710
Maximum | Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
Term of options to be granted under the Plan		10 years
Minimum | Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		3 years
2014 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for future issuance pursuant to future option grants		708,628		854,822
Percentage of increase in common shares reserved for future issuance pursuant to future option grants		4.00%
2014 Plan | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance		5,975,000
2014 Plan | Restricted Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		4 years
2014 Plan | Restricted Stock With Cliff Vesting
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period		1 year
2015 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for future issuance pursuant to future option grants		238,705
2015 Employee Stock Purchase Plan | Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional common shares reserved for future issuance pursuant to future option grants		2,000,000
2015 Employee Stock Purchase Plan | Maximum | Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of increase in common shares reserved for future issuance pursuant to future option grants		1.00%
Subsequent Event | 2014 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional common shares reserved for future issuance pursuant to future option grants	854,709

Equity Incentive Plan - Summary

Equity Incentive Plan - Summary of Stock Option Activities (Detail) - Stock Option $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding, Number of Shares | shares	574
Granted, Number of Shares | shares	703
Canceled/forfeited, Number of Shares | shares	(75)
Outstanding, Number of Shares | shares	1,202
Exercisable, Number of Shares | shares	331
Outstanding, Weighted-Average Exercise Price per Share | $ / shares	$ 9.10
Granted, Weighted-Average Exercise Price per Share | $ / shares	4.72
Canceled/forfeited, Weighted-Average Exercise Price per Share | $ / shares	11.64
Outstanding, Weighted-Average Exercise Price per Share | $ / shares	6.38
Exercisable, Weighted-Average Exercise Price per Share | $ / shares	$ 6.92
Outstanding, Weighted -Average Remaining Contractual Term (years)	8 years 10 months 24 days
Exercisable, Weighted -Average Remaining Contractual Term (years)	8 years 8 months 12 days
Outstanding, Aggregate Intrinsic Value | $	$ 840
Exercisable, Aggregate Intrinsic Value | $	$ 148

Equity Incentive Plan - Summa52

Equity Incentive Plan - Summary of Assumptions used to Estimate the Fair Value of Stock Options Under Black-Scholes Model (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value per share	$ 3.09	$ 4.16
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	73.80%	70.80%
Expected term (in years)	5 years 6 months	6 years
Risk free interest rate	1.50%	1.70%
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	76.60%	72.80%
Expected term (in years)	6 years 29 days	6 years 29 days
Risk free interest rate	1.70%	1.80%

Equity Incentive Plan - Summa53

Equity Incentive Plan - Summary of Restricted Stock Awards Activity (Detail) - Restricted Stock Awards shares in Thousands	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Beginning Balance, Number of Shares	3,233
Vested, Number of Shares	(1,210)
Forfeited, Number of Shares	(3)
Ending Balance, Number of Shares	2,020
Vested, Number of Shares	2,899
Beginning Balance, Weighted-Average Grant Date Fair Value | $ / shares	$ 0.002
Vested, Weighted-Average Grant Date Fair Value | $ / shares	0.002
Forfeited, Weighted-Average Grant Date Fair Value | $ / shares	0.002
Ending Balance, Weighted-Average Grant Date Fair Value | $ / shares	0.002
Vested, Weighted-Average Grant Date Fair Value | $ / shares	$ 0.002
Employee
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Beginning Balance, Number of Shares	2,717
Vested, Number of Shares	(1,017)
Forfeited, Number of Shares	(3)
Ending Balance, Number of Shares	1,697
Vested, Number of Shares	2,375
Non-employee
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Beginning Balance, Number of Shares	516
Vested, Number of Shares	(193)
Ending Balance, Number of Shares	323
Vested, Number of Shares	524

Equity Incentive Plan - Summa54

Equity Incentive Plan - Summary of Share-based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 2,089	$ 2,259
Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	1,293	1,916
General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 796	$ 343

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	Apr. 30, 2016	Dec. 18, 2014	Oct. 01, 2014	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Mar. 06, 2015	Jan. 12, 2015	Dec. 23, 2014	Oct. 08, 2014
Related Party Transaction [Line Items]
Rent expense related to office space sublease					$ 342,000	$ 267,000
Accounts receivable, related party				$ 295,000	$ 295,000	430,000
Araxes Asset Purchase Agreement
Related Party Transaction [Line Items]
Convertible promissory note									$ 500,000
Unpaid principal and accrued interest converted into common stock shares							80,293
Araxes Pharma LLC
Related Party Transaction [Line Items]
Convertible promissory note										$ 2,000,000
Unpaid principal and accrued interest converted into common stock shares							326,443
Management Fee, Description					We have a management services agreement with Araxes pursuant to which Araxes pays us a fixed fee of $65,000 per month for management services. In addition, the agreement allows for Araxes to reimburse us an amount equal to the number of full time equivalents, or FTE, performing research and development services for Araxes, at an annual FTE rate of approximately $350,000, plus actual expenses as reasonably incurred. The initial term of this agreement expired on December 31, 2015 but, pursuant to the terms of the agreement, renews automatically for additional consecutive one-year periods. The agreement may be terminated by either party with a notice of at least 30 days prior to the expiration of the then-renewal term.
Management service agreement, fixed	$ 65,000
Management service agreement, full time equivalents performing research and development services	$ 350,000
Agreement expiration date			Dec. 31, 2015
Agreement termination notice period			30 days
Amount received on research and development services					$ 358,000	330,000
Accounts receivable, related party				295,000	295,000	430,000
Araxes Pharma LLC | Convertible Promissory Note
Related Party Transaction [Line Items]
Unpaid principal and accrued interest converted into common stock shares							80,293
Araxes Pharma LLC | Araxes Asset Purchase Agreement
Related Party Transaction [Line Items]
Milestone payment paid				100,000
Wellspring Biosciences Inc
Related Party Transaction [Line Items]
Rent expense related to office space sublease					65,000	58,000
Agreement expiration date			Dec. 31, 2015
Agreement termination notice period			30 days
Research and development services expense at full time equivalents rate			$ 400,000
Research and development, related party					4,000,000	4,100,000
Accrued expenses, related party				$ 770,000	$ 770,000	$ 911,000
Wellspring Biosciences Inc | La Jolla, California
Related Party Transaction [Line Items]
Sublease expiration date		Oct. 31, 2019			Oct. 31, 2019
Sublease agreement description					In December 2016, we entered into a third amendment to Sublease pursuant to which the Sublease will expire on the later of (i) June 8, 2017 or (ii) seven days after the date on which Wellspring’s landlord delivers the premises to Wellspring.
Wellspring Biosciences Inc | San Diego, California
Related Party Transaction [Line Items]
Sublease expiration date					Oct. 31, 2019
Sublease agreement description					The terms of the New Sublease will commence on the later of (i) June 1, 2017 or (ii) the date on which Wellspring’s landlord delivers the premises subject to Wellspring’s master lease to Wellspring with certain improvements substantially completed. The New Sublease will expire on October 31, 2019.
January 2015 Convertible Notes
Related Party Transaction [Line Items]
Convertible promissory note								$ 3,000,000
Unpaid principal and accrued interest converted into common stock shares							479,667
January 2015 Convertible Notes | Certain Officers and Certain Officer's Related Parties
Related Party Transaction [Line Items]
Convertible promissory note								$ 710,000

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - Safe Harbor 401(k) Plan	12 Months Ended
	Dec. 31, 2016USD ($)
Defined Benefit Plan Disclosure [Line Items]
Expenses related to contribution plan	$ 176,000
Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of employees compensation	3.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Significant Components Of Deferred Tax Assets And Liabilities [Line Items]
Effective federal statutory income tax rate, Percent	34.00%	34.00%
Loss carryforwards begin to expire	2,034
Increase in valuation allowance	$ 11,100,000	$ 8,900,000
Income tax examination, likelihood of unfavorable settlement	An uncertain tax position will not be recognized if it has less than a 50% likelihood of being sustained.
Unrecognized interest or penalties	$ 0	$ 0
Domestic Tax Authority
Significant Components Of Deferred Tax Assets And Liabilities [Line Items]
Net operating loss	44,800,000
Research and development credit carryforwards	857,000
Research and development credit carryforwards, payroll tax offset utilized	$ 250,000
Credit carry forward begin to expire	2,034
Domestic Tax Authority | Research and Development Credits
Significant Components Of Deferred Tax Assets And Liabilities [Line Items]
Deferred tax assets tax credit carryforwards recognized benefit	$ 250,000
Domestic Tax Authority | Research and Development Credits | Maximum
Significant Components Of Deferred Tax Assets And Liabilities [Line Items]
Research and development credit carryforwards payroll tax offset qualifying amount	250,000
State and Local Jurisdiction
Significant Components Of Deferred Tax Assets And Liabilities [Line Items]
Net operating loss	54,400,000
Research and development credit carryforwards	629,000
State and Local Jurisdiction | Research and Development Credits
Significant Components Of Deferred Tax Assets And Liabilities [Line Items]
Credit carryforwards not subject to expiration	593,000
State and Local Jurisdiction | Expire in 2034
Significant Components Of Deferred Tax Assets And Liabilities [Line Items]
Net operating loss	$ 54,100,000
Credit carry forward begin to expire	2,034
State and Local Jurisdiction | Expire in 2030
Significant Components Of Deferred Tax Assets And Liabilities [Line Items]
Net operating loss	$ 310,000
Credit carry forward begin to expire	2,030
State and Local Jurisdiction | Expire in 2031 | Research and Development Credits
Significant Components Of Deferred Tax Assets And Liabilities [Line Items]
Credit carry forward begin to expire	2,031
Credit carryforwards subject to expiration	$ 36,000

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income taxes at statutory federal rate	$ (9,370)	$ (7,693)
State income tax, net of federal benefit	(1,823)	(1,412)
Share-based compensation	564	712
Research and development tax credits	(560)	(544)
Other	50	29
Valuation allowance	11,139	8,908
Income tax expense	$ 0	$ 0

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets
Net operating loss carryforwards	$ 18,321	$ 7,975
Intangibles	982	999
Research and development tax credit carryforwards	971	573
Accruals	809	662
Other	371	106
Total deferred tax assets	21,454	10,315
Less valuation allowance	(21,454)	(10,315)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Schedule of Acti

Income Taxes - Schedule of Activity Related to Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits at the beginning of the year	$ 167
Increases from tax positions taken in the current year	191	$ 167
Gross unrecognized tax benefits at the end of the year	$ 358	$ 167

Subsequent Event - Additional I

Subsequent Event - Additional Information (Detail) - Subsequent Event - Cowen and Company, LLC - At-The-Market - Maximum	Jan. 27, 2017USD ($)
Subsequent Event [Line Items]
Aggregate offering price	$ 25,000,000
Percentage of Commission on the gross proceeds from sales agreement	3.00%