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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2015	Aug. 12, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q2
Entity Registrant Name	Kura Oncology, Inc.
Entity Central Index Key	0001422143
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		14,508,177

Condensed Balance Sheets (Unaudited) - USD ($)
$ in Thousands

Jun. 30, 2015

Dec. 31, 2014

Current assets:

Cash and cash equivalents

$ 19,788

$ 1,124

^[1]

Short-term investments

26,145

Accounts receivable, related party

372

^[1]

Prepaid expenses and other current assets

884

^[1]

Total current assets

47,189

1,196

^[1]

Property and equipment, net

^[1]

Other long-term assets

279

150

^[1]

Other long-term assets, related party

^[1]

Total assets

47,532

1,378

^[1]

Current liabilities:

Accounts payable and accrued expenses

2,492

846

^[1]

Accounts payable and accrued expenses, related party

1,112

134

^[1]

Convertible notes payable, related party, current

^[1]

2,036

Total current liabilities

3,604

3,016

^[1]

Convertible notes payable, related party

^[1]

493

Other long-term liabilities

604

1,295

^[1]

Other long-term liabilities, related party

^[1]

Total liabilities

4,208

4,811

^[1]

Commitments and contingencies (Note 10)

^[1]

Stockholders' equity (deficit):

Preferred stock, $0.0001 par value; 10,000 shares authorized; no shares issued and outstanding

^[1]

Common stock, $0.0001 par value; 200,000 and 100,000 shares authorized; 14,508 and 4,944 shares issued; and 10,609 and 411 shares outstanding, excluding 3,899 and 4,533 shares subject to repurchase as of June 30, 2015 and December 31, 2014, respectively

Additional paid-in capital

57,069

238

^[1]

Accumulated comprehensive loss

(14)

Accumulated deficit

(13,732)

(3,671)

^[1]

Total stockholders' equity (deficit)

43,324

(3,433)

^[1]

Total liabilities and stockholders' equity (deficit)

$ 47,532

$ 1,378

^[1]

[1]	The balance sheet data at December 31, 2014 has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by U.S. generally accepted accounting principles for complete financial statements.

Condensed Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2015	Dec. 31, 2014
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	100,000,000
Common stock, shares issued	14,508,177	4,944,000
Common stock, shares outstanding	10,609,000	411,000
Number of shares, subject to repurchase	3,899,000	4,533,000

Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015
Operating Expenses:
Research and development	$ 3,345	$ 5,949
General and administrative	1,492	2,529
General and administrative, related party	14	37
Total operating expenses	5,907	10,595
Other Income (Expense):
Management fee income, related party	300	600
Interest income	22	22
Interest expense		(42)
Interest expense, related party		(46)
Total other income	322	534
Net loss	$ (5,585)	$ (10,061)
Net loss per share, basic and diluted	$ (0.54)	$ (1.47)
Weighted average number of shares used in computing net loss per share, basic and diluted	10,420	6,822
Comprehensive Loss:
Net loss	$ (5,585)	$ (10,061)
Unrealized loss on marketable securities	(14)	(14)
Comprehensive loss	(5,599)	(10,075)
Related party
Operating Expenses:
Research and development	$ 1,056	$ 2,080

Condensed Statement of Cash Flows (Unaudited)

6 Months Ended

Jun. 30, 2015

USD ($)

Operating Activities

Net loss

$ (10,061,000)

Adjustments to reconcile net loss to net cash used in operating activities:

Share-based compensation expense

1,129,000

Non-cash license fee expense

500,000

Change in value of derivative liability

307,000

^[1]

Non-cash accrued interest expense

37,000

Non-cash accrued interest expense, related parties

42,000

Depreciation expense

6,000

Amortization of discount on marketable securities

37,000

Changes in operating assets and liabilities:

Accounts receivable, related party

(342,000)

Prepaid expenses and other current assets

(778,000)

Other long-term assets

(129,000)

Accounts payable and accrued expenses

1,382,000

Accounts payable and accrued expenses, related party

978,000

Other long-term liabilities

(998,000)

Net cash used in operating activities

(7,890,000)

Investing Activities

Purchases of marketable securities

(26,260,000)

Purchases of property and equipment

(27,000)

Net cash used in investing activities

(26,287,000)

Financing Activities

Proceeds from issuance of common stock, net

47,841,000

Proceeds from issuance of convertible notes payable

5,000,000

Net cash provided by financing activities

52,841,000

Net increase in cash and cash equivalents

18,664,000

Cash and cash equivalents at beginning of period

1,124,000

^[2]

Cash and cash equivalents at end of period

19,788,000

Supplemental disclosure of non-cash financing activities:

Conversion of convertible notes and related accrued interest to common stock

4,327,000

Conversion of convertible notes and related accrued interest to common stock, related party

3,288,000

Financing costs included in accounts payable and accrued expenses

$ 253,000

[1]	The amount is included within research and development expenses on our condensed statement of operations and comprehensive loss. The change in fair value of the derivative liability for the three and six months ended June 30, 2015 was $210,000 and $307,000, respectively.
[2]	The balance sheet data at December 31, 2014 has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by U.S. generally accepted accounting principles for complete financial statements.

Business and Organization	6 Months Ended
Business and Organization	Jun. 30, 2015
Accounting Policies [Abstract]
Business and Organization	1. Business and Organization Kura Oncology, Inc., is a clinical stage biopharmaceutical company discovering and developing personalized therapeutics for the treatment of solid tumors and blood cancers. We focus on the development of small molecule drug candidates that target cell signaling pathways that are important to driving the progression of certain cancers. We aim to employ molecular diagnostics to identify patients with cancers who are likely to benefit from our targeted drug candidates. References in these Notes to Unaudited Condensed 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, for the periods following the Merger. Effective March 6, 2015, or Effective Time, we completed a reverse merger, or the Merger, with a wholly owned subsidiary of “Zeta Acquisition Corp. III,” or Zeta, a public shell company, 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 the Merger Agreement, at the Effective Time, each share of Prior Kura common stock outstanding immediately prior to the Effective Time was exchanged for one-half (1/2) of a share of our common stock. The share and price per share amounts presented in these Unaudited Condensed Financial Statements have been adjusted for such exchange. We issued an aggregate of 14,508,177 shares of our common stock upon such exchange of the Prior Kura common stock outstanding. In addition, at the Effective Time, we assumed Prior Kura’s 2014 Equity Incentive Plan that was in existence immediately prior to the Effective Time and concurrently approved the amendment and restatement of the Prior Kura 2014 Equity Incentive Plan, or 2014 Plan, pursuant to our 2014 Plan, which became effective in April 2015. Refer to Note 12, Equity Incentive Plan for detailed discussion of the 2014 Plan. Immediately following the Effective Time, pursuant to the terms of a Redemption Agreement dated March 6, 2015, or the Redemption Agreement, by and among Zeta and its pre-Merger stockholders, we completed the closing of a redemption of 5,000,000 shares of our common stock, or the Redemption, from our pre-Merger stockholders for consideration of $70,000, plus $30,000 in professional fees related to the transaction. The 5,000,000 shares constituted all of the issued and outstanding shares of Zeta’s capital stock, on a fully-diluted basis, immediately prior to the Merger. Upon completion of the Merger and the Redemption, Prior Kura’s stockholders held 100% of the outstanding shares of our capital stock. Immediately prior to the Merger, on March 6, 2015, Prior Kura sold 8,280,696 shares of our common stock to investors at a price of $6.32 per share for gross proceeds of $52.3 million, or the Financing. The Financing represented a qualified financing conversion event pursuant to the then outstanding convertible promissory notes. As such, upon the closing of the Financing, $7.5 million in principal and $115,000 in accrued interest on such convertible promissory notes through February 28, 2015 automatically converted into 1,204,870 shares of our common stock. The Merger is accounted for as a reverse merger and a capital transaction. Prior Kura is the acquirer for accounting purposes and Zeta is the acquired company. Consequently, the assets and liabilities and the operations that are reflected in the historical financial statements prior to the Merger are those of Prior Kura and are recorded at Prior Kura’s historical cost basis. Prior Kura was incorporated in August 2014; therefore, there were no operations in the periods prior to August 2014. The financial statements after completion of the Merger include our assets, liabilities and operations. The historical equity accounts and awards of Prior Kura, including par value per share, share and per share numbers, have been retrospectively adjusted to reflect the one for 0.5 shares common stock exchange, the par value of $0.0001 and the number of shares received in the Merger.

Basis of Presentation	6 Months Ended
Basis of Presentation	Jun. 30, 2015
Accounting Policies [Abstract]
Basis of Presentation	2. Basis of Presentation The accompanying unaudited condensed financial statements should be read in conjunction with Prior Kura’s audited financial statements and notes thereto for the year ended December 31, 2014 included in the final prospectus dated July 21, 2015 filed with the Securities and Exchange Commission, or SEC, pursuant to Rule 424(b) under the Securities Act of 1933, as amended, relating to our registration statement on Form S-1 (333-203503), originally filed with on April 17, 2015, as amended, from which we derived our balance sheet as of December 31, 2014. The accompanying condensed financial statements have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, since they are interim statements, the accompanying condensed financial statements do not include all of the information and notes required by GAAP for complete financial statements. The accompanying condensed financial statements reflect all adjustments, consisting of normal recurring adjustments, that are, in the opinion of our management, necessary to a fair statement of the results for the interim periods presented. Interim results are not necessarily indicative of results for a full year. The preparation of the condensed financial statements in accordance with GAAP requires our management to make estimates and assumptions that affect the amounts reported in our condensed financial statements and accompanying notes. The amounts reported could differ under different estimates and assumptions. On an ongoing basis, we evaluate our estimates and judgments, which are based on historical and anticipated results and trends and on various other assumptions that management believes to be reasonable under the circumstances. By their nature, estimates are subject to an inherent degree of uncertainty and, as such, actual results may differ from management’s estimates.

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2015

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

3. Summary of Significant Accounting Policies

Cash and Cash Equivalents

Cash equivalents consist of 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. Cash and cash equivalents consist primarily of cash in readily available checking and money market accounts.

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. Short-term investments are classified as available-for-sale at fair value as determined by prices for identical or similar securities at the balance sheet date. 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. The available-for-sale investments are carried at fair value with unrealized gains and losses recorded in other comprehensive loss and included as a separate component of stockholders' equity (deficit). 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 in the condensed statement 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; and

•	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.

Research and Development Expenses

Research and development expenses consist of salaries, benefits, and other personnel costs, preclinical and clinical trial costs, manufacturing costs for non-commercial products, and research and development facilities costs. All such costs are charged to research and development expense as incurred when these expenditures have no alternative future uses. 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 June 30, 2015, 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 condensed financial statements by matching those expenses with the period in which services and efforts are expended. As part of the process of preparing our condensed 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.

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 estimated forfeitures. The fair value of each stock option is estimated on the date of grant using the Black-Scholes option pricing 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 option pricing 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.

Comprehensive Loss

Comprehensive loss is defined as the change in equity during the period from transactions and other events and non-owner sources, including unrealized losses on marketable securities.

Segment Reporting

We operate in a single industry segment which is the discovery and development of personalized therapeutics for the treatment of solid tumors and blood cancers. Our chief operating decision-maker reviews the operating results on an aggregate basis and manages the operations as a single operating segment.

Net Loss per Share

We calculated basic net loss per common share 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 and outstanding stock options under our equity plan. 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 stock awards representing an aggregate of 3,899,285 shares of common stock and options to purchase an aggregate of 410,000 shares of common stock, are excluded from the calculation of diluted net loss per common share as of June 30, 2015 due to the anti-dilutive effect of the securities.

Recent Accounting Pronouncements

In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standard 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. The new standard allows for two methods of adoption: (a) full retrospective adoption, meaning the standard is applied to all periods presented, or (b) modified retrospective adoption, meaning the cumulative effect of applying the new standard is recognized as an adjustment to the opening retained earnings balance.

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 for annual reporting period beginning after December 15, 2017, including interim periods within that reporting period. We are currently evaluating the alternative transition methods and the potential effects on our financial statements and future operating results.

In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements-Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. Under the new guidance, management will be required to assess an entity’s ability to continue as a going concern, and to provide related footnote disclosures in certain circumstances. The provisions of this ASU are effective for annual periods beginning after December 15, 2016, and for annual and interim periods thereafter. We are currently evaluating the potential changes from this ASU to our future financial reporting and disclosures.

Short-Term Investments

6 Months Ended

Jun. 30, 2015

Investments All Other Investments [Abstract]

Short-Term Investments

4. Short-Term Investments

The following table summarizes, by major security type, our short-term investments that are measured at fair value on a recurring basis as of June 30, 2015, in thousands:

		As of June 30, 2015
	Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Government sponsored entities	2 years or less	$	13,317	$	1	$	(2	)	$	13,316
Corporate debt securities	2 years or less		8,946		-		(13	)		8,933
Commercial paper	1 year or less		3,896		-		-			3,896
Total		$	26,159	$	1	$	(15	)	$	26,145

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. We review our investments to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee, and our intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. As of June 30, 2015, we had not recognized any such impairment in our condensed financial statements.

- Definition

The entire disclosure for investments in certain debt and equity securities.

+ References + Details

Fair Value Measurements

6 Months Ended

Jun. 30, 2015

Fair Value Disclosures [Abstract]

Fair Value Measurements

5. Fair Value Measurements

Investment Securities

As of June 30, 2015, we had cash equivalents and short-term investments measured at fair value on a recurring basis. As of December 31, 2014, we did not have any cash equivalents or 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 June 30, 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 corporate debt securities, commercial paper and government sponsored entities and 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 table summarizes, 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 June 30, 2015, in thousands:

	Fair Value Measurements at June 30, 2015
	Balance		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	18,753	$	18,753	$	-	$	-

Short-term investments:
Government sponsored entities		13,316		-		13,316		-
Corporate debt securities		8,933		-		8,933		-
Commercial paper		3,896		-		3,896		-
Total short-term investments		26,145		-		26,145		-
Total	$	44,898	$	18,753	$	26,145	$	-

Derivative Liability

Our license agreement with The Regents of the University of California San Francisco, or UCSF, which was amended in April 2015, provides for an 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. The indexed milestone was determined to qualify as an embedded derivative liability requiring an estimate of fair value. The UCSF derivative liability is measured at fair value (Level 3) on a recurring basis and is included in other long-term liabilities on the condensed balance sheets. No transfers between levels have occurred during the periods presented.

We estimate the fair value of our derivative liabilities at the time of issuance and subsequent remeasurement at each reporting date using a probability model that considers the probability of achieving the events that would trigger such liabilities and the estimated time period the liabilities would be outstanding. The estimates are based, in part, on subjective assumptions and could differ materially in the future. Changes to these assumptions can have a significant impact on the fair value of the derivative liabilities.

The following table provides a reconciliation of all liabilities measured at fair value using Level 3 significant unobservable inputs:

	Derivative Liabilities
	(In thousands)
Balance at December 31, 2014	$	196
Change in fair value ⁽¹⁾		307
Balance at June 30, 2015	$	503

(1)	The amount is included within research and development expenses on our condensed statement of operations and comprehensive loss. The change in fair value of the derivative liability for the three and six months ended June 30, 2015 was $210,000 and $307,000, respectively.

Property and Equipment, Net

6 Months Ended

Jun. 30, 2015

Property Plant And Equipment [Abstract]

Property and Equipment, Net

6. Property and Equipment, Net

Property and equipment consisted of the following, in thousands:

	June 30, 2015			December 31, 2014
Computer equipment	$	59		$	26
Software		7			2
		66			28
Less: accumulated depreciation		(7	)		(1	)
Property and equipment, net	$	59		$	27

Accounts Payable and Accrued Liabilities

6 Months Ended

Jun. 30, 2015

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:

	June 30, 2015		December 31, 2014
Accounts payable	$	715	$	226
Accrued expenses		1,193		581
Accrued compensation and benefits		584		39
Total accounts payable and accrued expenses	$	2,492	$	846

Notes Payable	6 Months Ended
Notes Payable	Jun. 30, 2015
Debt Disclosure [Abstract]
Notes Payable	8. 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. As a result of the Financing, the total 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. As a result of the Financing, the total of unpaid principal and accrued interest as of February 28, 2015 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, or the Holders, of which $710,000 were with certain officers and certain officers’ related parties. As a result of the Financing, the total of unpaid principal and accrued interest as of February 28, 2015 was automatically converted into 479,667 shares of our common stock. JJDC Convertible Note In accordance with the license agreement with Janssen Pharmaceutica NV, or Janssen, a foreign entity headquartered in Belgium and an affiliate of Johnson & Johnson, Inc., in January 2015 we entered into a Convertible Promissory Note with Janssen’s affiliated company, Johnson & Johnson Innovation – JJDC, Inc., or JJDC, for $1.0 million. As a result of the Financing, the total of unpaid principal and accrued interest as of February 28, 2015 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 Note Holders, under which the February Note Holders provided a $1.0 million loan in the form of convertible promissory notes. As a result of the Financing, the total of unpaid principal and accrued interest as of February 28, 2015 was automatically converted into 158,852 shares of our common stock.

License Agreements	6 Months Ended
License Agreements	Jun. 30, 2015
License Agreements [Abstract]
License Agreements	9. License Agreements License Agreement with The University of Michigan In December 2014, we entered into a license agreement with The Regents of The University of Michigan, or Michigan, 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 a number of 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. 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 the Financing, 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 six months ended June 30, 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 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. Sponsored Research Agreement with The University of Michigan In February 2015, we entered into a Sponsored Research Agreement with Michigan under which we will sponsor up to $2.7 million of research at Michigan over a three-year period. We will 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. In the event of termination by us prior to the second anniversary of the agreement, other than due to breach by Michigan, we will be required to pay costs budgeted through the second anniversary up to $2.0 million of the sponsored research amount. Any costs incurred for the Sponsored Research Agreement will be expensed as incurred. For the three and six months ended June 30, 2015, we recorded approximately $251,000 and $376,000, respectively, in research and development expense under this research agreement. Collectively, our outstanding license agreements provide for specified development, regulatory and sales-based milestone payments up to a total of $81.7 million payable upon occurrence of each stated event, of which $1.2 million relates to the initiation of certain development activities, $30.5 million relates to the achievement of specified regulatory approvals for the first indication and up to $50.0 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 June 30, 2015, 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.

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Jun. 30, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments and Contingencies 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	6 Months Ended
Stockholders' Equity	Jun. 30, 2015
Equity [Abstract]
Stockholders' Equity	11. Stockholders’ Equity Immediately prior to the Merger, on March 6, 2015, Prior Kura sold 8,280,696 shares of our common stock at a price of $6.32 per share, for net proceeds of approximately $48.2 million, net of $4.1 million in fees. The Financing represented a qualified financing conversion event pursuant to the Notes. As such, upon the closing of the Financing, an aggregate of $7.5 million in principal under the Notes and $115,000 in accrued interest through February 28, 2015 automatically converted into 1,204,870 shares of our common stock. 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. Effective April 13, 2015, pursuant to our amended and restated certificate of incorporation, we have authorized capital stock consisting of 200,000,000 shares of common stock, par value $0.0001 per share, and 10,000,000 shares of preferred stock, par value $0.0001 per share.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(d),(e))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74512-122707

Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21488-112644

Reference 5: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29-31)
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Reference 6: http://www.xbrl.org/2003/role/presentationRef
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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
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-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23285-112656

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Preferred Stock
-URI http://asc.fasb.org/extlink&oid=6521494

Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21564-112644

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 08
-Paragraph d
-Article 4

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 29, 30, 31
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Reference 16: http://www.xbrl.org/2003/role/presentationRef
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-Name Staff Accounting Bulletin (SAB)
-Number Topic 4
-Section E

Reference 17: http://www.xbrl.org/2003/role/presentationRef
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Reference 18: http://www.xbrl.org/2003/role/presentationRef
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Reference 19: http://www.xbrl.org/2003/role/presentationRef
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-Name Regulation S-X (SX)
-Number 210
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-Article 3

+ Details

Equity Incentive Plan

6 Months Ended

Jun. 30, 2015

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Equity Incentive Plan

12. Equity Incentive Plan

In August 2014, Prior Kura adopted the Prior Kura 2014 Equity Incentive Plan. In connection with the Merger as discussed in Note 1, at the Effective Time of the Merger, we adopted the Prior Kura 2014 Equity Incentive Plan and approved the amendment and restatement of the Prior Kura 2014 Equity Incentive Plan pursuant to the 2014 Plan, which became effective April 13, 2015. Under the 2014 Plan, a total of 5,975,000 shares are reserved for issuance. As of June 30, 2015, there were 621,500 shares of common stock reserved for future stock awards under the 2014 Plan. The 2014 Plan provides equity-based incentives in the form of stock awards to employees and other providers of services to us. The 2014 Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock unit awards, performance-based stock awards and other forms of equity compensation to eligible recipients. Recipients of incentive stock options shall be eligible to purchase shares of our common stock at an exercise price equal to no less than the estimated fair market value of such stock on the date of grant. The maximum term of options to be granted under the Plan is ten years.

Stock Options

The following is a summary of stock option activity for the six months ended June 30, 2015, in thousands (except per share data):

	Number of Shares		Weighted Average Exercise Price per Share
Balance at December 31, 2014		-
Granted		410	$	6.32
Balance at June 30, 2015		410	$	6.32
Exercisable at June 30, 2015		2	$	6.32

The weighted average assumptions used to estimate the fair value of stock options granted to employees in the six months ended June 30, 2015 using the Black-Scholes option pricing model were as follows:

	Six Months Ended
	June 30, 2015
Weighted average grant date fair value per share	$	4.02
Expected volatility		70.8	%
Expected term (in years)	6.00 — 6.08
Risk free interest rate		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 not been publicly traded. 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 apply estimate forfeitures at the time of grant based on historical experience and revise our estimate in subsequent periods if actual forfeitures differ from those estimates.

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 June 30, 2015, there were 3,899,285 shares subject to repurchase, of which 3,286,888 and 612,397 shares were related to employee and non-employee stock awards, respectively.

The following is a summary of restricted share activity for the six months ended June 30, 2015, in thousands (except per share data):

	Number of Shares			Weighted Average Grant Date Fair Value
Balance at December 31, 2014		4,533		$	0.002
Granted		-
Vested		(634	)
Unvested at June 30, 2015		3,899		$	0.003
Vested at June 30, 2015		1,044		$	0.004

For the six months ended June 30, 2015, 487,028 and 146,561 shares underlying restricted stock awards granted to employees and non-employees, respectively, vested. As of June 30, 2015, 809,112 and 235,103 shares of underlying restricted stock awards granted to employees and non-employees, respectively, were vested. For the three and six months ended June 30, 2015, we recognized share-based compensation expense related to restricted stock awards totaling $397,000 and $1.0 million, respectively, of which $364,000 and $968,000 related to non-employee restricted stock awards, respectively.

The following table summarizes share-based compensation expense for all equity awards granted, in thousands:

	Three months ended		Six months ended
	June 30, 2015		June 30, 2015
Research and development	$	404	$	1,007
General and administrative		81		122
Total stock-based compensation expense	$	485	$	1,129

Related Party Transactions	6 Months Ended
Related Party Transactions	Jun. 30, 2015
Related Party Transactions [Abstract]
Related Party Transactions	13. Related Party Transactions As discussed in Note 8, in January 2015, we entered into a Note Purchase Agreement and Convertible Promissory Note for a $3.0 million loan with the Holders, of which $710,000 were with certain officers and certain officers’ related parties. As a result of the Financing, the total of unpaid principal and accrued interest as of February 28, 2015 was automatically converted into 479,667 shares of our common stock. Our president and chief executive officer is also the managing member of our affiliated company Araxes. Four individuals are significant stockholders of each of us and Araxes. The following is a summary of all transactions with Araxes for the six months ended June 30, 2015: Convertible Promissory Notes As described in Note 8, as a result of the Financing, the total of unpaid principal and accrued interest as of February 28, 2015 for the convertible note payable to Araxes was automatically converted into 326,443 shares of our common stock. In addition, the total of unpaid principal and accrued interest as of February 28, 2015 for the convertible note payable related to the Araxes asset purchase was automatically converted into 80,293 shares of our common stock. Facility Sublease We sublease office space from Araxes for a base rent of approximately $5,000 per month plus operating expenses, taxes, insurance, and utilities applicable to the subleased property. Rent expense related to this sublease for the three and six months ended June 30, 2015 was $24,000 and $49,000, respectively. The sublease will expire on August 30, 2016. Management Fees We have a management services agreement with Araxes under which Araxes pays us a fixed $100,000 a month for management services. In addition, the agreement allows for Araxes to pay us an amount equal to the number of full time equivalents, or FTE, performing collaboration services for Araxes, at an annual FTE rate of $350,000, plus actual expenses as reasonably incurred. The agreement has an initial term expiring on December 31, 2015 and 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 December 31, 2015 or the expiration of the then-renewal term. Services Agreement We have a services agreement with Wellspring Biosciences LLC (a wholly owned subsidiary of Araxes) 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. This services agreement has an initial term expiring on December 31, 2015 and 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 December 31, 2015 or the expiration of the then-renewal term.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References + Details

Subsequent Events	6 Months Ended
Subsequent Events	Jun. 30, 2015
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events Cambridge Facilities Lease In August 2015, we entered into a lease agreement for approximately 3,677 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, 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 operating expenses, taxes, insurance and utilities applicable to the leased property.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2015

Accounting Policies [Abstract]

Cash and Cash Equivalents

Short-Term Investments

Fair Value Measurements

•	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; and

•	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.

Research and Development Expenses

Clinical Trial Costs and Accruals

Share-Based Payments

Comprehensive Loss

Comprehensive loss is defined as the change in equity during the period from transactions and other events and non-owner sources, including unrealized losses on marketable securities.

Segment Reporting

Net Loss per Share

Recent Accounting Pronouncements

Short-Term Investments (Tables)

6 Months Ended

Jun. 30, 2015

Investments All Other Investments [Abstract]

Short-Term Investments Measured at Fair Value on Recurring Basis

The following table summarizes, by major security type, our short-term investments that are measured at fair value on a recurring basis as of June 30, 2015, in thousands:

		As of June 30, 2015
	Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Government sponsored entities	2 years or less	$	13,317	$	1	$	(2	)	$	13,316
Corporate debt securities	2 years or less		8,946		-		(13	)		8,933
Commercial paper	1 year or less		3,896		-		-			3,896
Total		$	26,159	$	1	$	(15	)	$	26,145

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2015

Fair Value Disclosures [Abstract]

Schedule Of Fair Value Measurements, By Major Security Type

	Fair Value Measurements at June 30, 2015
	Balance		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	18,753	$	18,753	$	-	$	-

Short-term investments:
Government sponsored entities		13,316		-		13,316		-
Corporate debt securities		8,933		-		8,933		-
Commercial paper		3,896		-		3,896		-
Total short-term investments		26,145		-		26,145		-
Total	$	44,898	$	18,753	$	26,145	$	-

Significant Impact of Changes in Assumptions on Fair Value of Derivative Liabilities

Changes to these assumptions can have a significant impact on the fair value of the derivative liabilities.

	Derivative Liabilities
	(In thousands)
Balance at December 31, 2014	$	196
Change in fair value ⁽¹⁾		307
Balance at June 30, 2015	$	503

The amount is included within research and development expenses on our condensed statement of operations and comprehensive loss. The change in fair value of the derivative liability for the three and six months ended June 30, 2015 was $210,000 and $307,000, respectively.

Property and Equipment, Net (Tables)

6 Months Ended

Jun. 30, 2015

Property Plant And Equipment [Abstract]

Property and Equipment, Net

Property and equipment consisted of the following, in thousands:

	June 30, 2015			December 31, 2014
Computer equipment	$	59		$	26
Software		7			2
		66			28
Less: accumulated depreciation		(7	)		(1	)
Property and equipment, net	$	59		$	27

Accounts Payable and Accrued Liabilities (Tables)

6 Months Ended

Jun. 30, 2015

Payables And Accruals [Abstract]

Accounts Payable and Accrued Liabilities

Accounts payable and accrued liabilities consisted of the following, in thousands:

	June 30, 2015		December 31, 2014
Accounts payable	$	715	$	226
Accrued expenses		1,193		581
Accrued compensation and benefits		584		39
Total accounts payable and accrued expenses	$	2,492	$	846

Equity Incentive Plan (Tables)

6 Months Ended

Jun. 30, 2015

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity

The following is a summary of stock option activity for the six months ended June 30, 2015, in thousands (except per share data):

	Number of Shares		Weighted Average Exercise Price per Share
Balance at December 31, 2014		-
Granted		410	$	6.32
Balance at June 30, 2015		410	$	6.32
Exercisable at June 30, 2015		2	$	6.32

Summary of Weighted Average Assumptions of Fair Value of Stock Options Under Black-Scholes Option Pricing Model

	Six Months Ended
	June 30, 2015
Weighted average grant date fair value per share	$	4.02
Expected volatility		70.8	%
Expected term (in years)	6.00 — 6.08
Risk free interest rate		1.8	%
Expected dividend yield	-

Summary of Restricted Share Activity

The following is a summary of restricted share activity for the six months ended June 30, 2015, in thousands (except per share data):

	Number of Shares			Weighted Average Grant Date Fair Value
Balance at December 31, 2014		4,533		$	0.002
Granted		-
Vested		(634	)
Unvested at June 30, 2015		3,899		$	0.003
Vested at June 30, 2015		1,044		$	0.004

Summary of Share-based Compensation Expense

The following table summarizes share-based compensation expense for all equity awards granted, in thousands:

	Three months ended		Six months ended
	June 30, 2015		June 30, 2015
Research and development	$	404	$	1,007
General and administrative		81		122
Total stock-based compensation expense	$	485	$	1,129

Business and Organization - Additional Information (Detail)			6 Months Ended
	Mar. 06, 2015 USD ($) $ / shares shares	Feb. 28, 2015 USD ($) shares	Jun. 30, 2015 USD ($) $ / shares shares	Apr. 13, 2015 $ / shares	Dec. 31, 2014 $ / shares shares
Product Information [Line Items]
Common stock, shares issued \| shares			14,508,177		4,944,000
Redemption of pre merger common stock shares \| shares	5,000,000
Aggregate consideration of redemption	$ 70,000
Professional costs	$ 30,000
Percentage by Parent	100.00%
Proceeds from issuance of common stock, net			$ 47,841,000
Conversion of convertible promissory notes and accrued interest, Shares \| shares		1,204,870
Reverse merger common share exchange ratio			0.5
Common stock, par value \| $ / shares			$ 0.0001	$ 0.0001	$ 0.0001
Private Placement [Member]
Product Information [Line Items]
Common stock, shares issued \| shares	8,280,696
Common stock, issued price per share \| $ / shares	$ 6.32
Proceeds from issuance of common stock, net	$ 52,300,000
Convertible promissory notes accrued interest		$ 115,000
Conversion of common stock		$ 7,500,000

Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2015 Segment shares
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments \| Segment	1
Unvested Stock Awards
Summary Of Significant Accounting Policies [Line Items]
Potentially dilutive securities	3,899,285
Employee Stock Option
Summary Of Significant Accounting Policies [Line Items]
Potentially dilutive securities	410,000

Short-Term Investments - Short-Term Investments Measured at Fair Value on Recurring Basis (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2015 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 26,159
Unrealized Gains	1
Unrealized Losses	(15)
Fair Value	$ 26,145
Government Sponsored Entities
Schedule Of Available For Sale Securities [Line Items]
Maturity (in years)	2 years or less
Amortized Cost	$ 13,317
Unrealized Gains	1
Unrealized Losses	(2)
Fair Value	$ 13,316
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturity (in years)	2 years or less
Amortized Cost	$ 8,946
Unrealized Losses	(13)
Fair Value	$ 8,933
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Maturity (in years)	1 year or less
Amortized Cost	$ 3,896
Fair Value	$ 3,896

Fair Value Measurement - Fair Values of Investment Securities (Detail) $ in Thousands	Jun. 30, 2015 USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 26,145
Fair Value Measurements on Recurring Basis
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	26,145
Cash equivalents and short-term investments	44,898
Fair Value Measurements on Recurring Basis \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents and short-term investments	18,753
Fair Value Measurements on Recurring Basis \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	26,145
Cash equivalents and short-term investments	26,145
Fair Value Measurements on Recurring Basis \| Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	18,753
Fair Value Measurements on Recurring Basis \| Money Market Funds \| Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	18,753
Fair Value Measurements on Recurring Basis \| Government Sponsored Entities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	13,316
Fair Value Measurements on Recurring Basis \| Government Sponsored Entities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	13,316
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	8,933
Fair Value Measurements on Recurring Basis \| Corporate Debt Securities \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	8,933
Fair Value Measurements on Recurring Basis \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	3,896
Fair Value Measurements on Recurring Basis \| Commercial Paper \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 3,896

Fair Value Measurement - Summary of Significant Impact of Changes in Assumptions on Fair Value of Derivative Liabilities (Detail) - USD ($)

3 Months Ended

6 Months Ended

Jun. 30, 2015

Fair Value Disclosures [Abstract]

Derivative Liabilities, Beginning Balance

$ 196,000

Change in value of derivative liability

$ 210,000

307,000

^[1]

Derivative Liabilities, Ending Balance

$ 503,000

[1]	The amount is included within research and development expenses on our condensed statement of operations and comprehensive loss. The change in fair value of the derivative liability for the three and six months ended June 30, 2015 was $210,000 and $307,000, respectively.

Fair Value Measurement - Summary of Significant Impact of Changes in Assumptions on Fair Value of Derivative Liabilities (Parenthetical) (Detail) - USD ($)

3 Months Ended

6 Months Ended

Jun. 30, 2015

Fair Value Disclosures [Abstract]

Change in fair value

$ (210,000)

$ (307,000)

^[1]

[1]	The amount is included within research and development expenses on our condensed statement of operations and comprehensive loss. The change in fair value of the derivative liability for the three and six months ended June 30, 2015 was $210,000 and $307,000, respectively.

Property and Equipment, Net (Detail) - USD ($)
$ in Thousands

Jun. 30, 2015

Dec. 31, 2014

Property Plant And Equipment [Line Items]

Property and equipment, gross

$ 66

$ 28

Less: accumulated depreciation

(7)

(1)

Property and equipment, net

^[1]

Computer Equipment

Property Plant And Equipment [Line Items]

Property and equipment, gross

Software

Property Plant And Equipment [Line Items]

Property and equipment, gross

$ 7

$ 2

[1]	The balance sheet data at December 31, 2014 has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by U.S. generally accepted accounting principles for complete financial statements.

Accounts Payable and Accrued Liabilities (Detail) - USD ($)
$ in Thousands

Jun. 30, 2015

Dec. 31, 2014

Payables And Accruals [Abstract]

Accounts payable

$ 715

$ 226

Accrued expenses

1,193

581

Accrued compensation and benefits

584

Total accounts payable and accrued expenses

$ 2,492

$ 846

^[1]

[1]	The balance sheet data at December 31, 2014 has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by U.S. generally accepted accounting principles for complete financial statements.

Notes Payable - Additional Information (Detail) - USD ($)	Feb. 28, 2015	Jan. 31, 2015	Dec. 31, 2014	Oct. 31, 2014
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 Information (Detail) - USD ($) $ in Thousands			3 Months Ended	6 Months Ended
	Feb. 15, 2015	Nov. 21, 2014	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
License Agreements [Line Items]
Common stock, shares issued			14,508,177	14,508,177	4,944,000
Research and development			$ 3,345	$ 5,949
The University of Michigan License Agreement
License Agreements [Line Items]
License agreement date				Dec. 22, 2014
Common stock, shares issued			79,113	79,113
Research and development				$ 500
Agreement termination written notice				90 days
Agreement termination period due to payment failure				30 days
Agreement termination notice period in event of material breach				60 days
The University of Michigan Sponsored Research Agreement
License Agreements [Line Items]
Research and development			$ 251	$ 376
Sponsor of research over three- year	$ 2,700
Sponsored research agreement period	3 years
Sponsored research amount, expensed as incurred	$ 2,000
License Agreements
License Agreements [Line Items]
Outstanding license agreements		$ 81,700
License Agreements \| Initiation of Certain Development Activities
License Agreements [Line Items]
Outstanding license agreements		1,200
License Agreements \| Specified Regulatory Approvals
License Agreements [Line Items]
Outstanding license agreements		30,500
License Agreements \| Specified Levels of Product Sales
License Agreements [Line Items]
Outstanding license agreements		$ 50,000

Stockholder's Equity - Additional Information (Detail) - USD ($)	Mar. 06, 2015	Feb. 28, 2015	Jun. 30, 2015	Apr. 13, 2015	Dec. 31, 2014
Stockholders' Equity Note [Abstract]
Conversion of convertible promissory notes and accrued interest, Shares		1,204,870
Common stock, shares authorized			200,000,000	200,000,000	100,000,000
Common stock, par value			$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, shares authorized			10,000,000	10,000,000	10,000,000
Preferred stock, par value			$ 0.0001	$ 0.0001	$ 0.0001
Private Placement [Member]
Stockholders' Equity Note [Abstract]
Common stock, shares issued	8,280,696
Common stock, issued price per share	$ 6.32
Proceeds from issuance of common stock net of issuance costs	$ 48,200,000
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
Private Placement [Member] \| Common Stock [Member]
Stockholders' Equity Note [Abstract]
Conversion of convertible promissory notes and accrued interest, Shares		1,204,870

Equity Incentive Plan - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Aug. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, subject to repurchase		3,899,285
Number of shares, subject to repurchase	3,899,000	3,899,000	4,533,000
Share-based compensation expense	$ 485,000	$ 1,129,000
Restricted Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of restricted stock awards vested		634,000
Share-based compensation expense	$ 397,000	$ 1,000,000
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, subject to repurchase	3,286,888	3,286,888
Non Employee Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, subject to repurchase	612,397	612,397
Employee Restricted Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of restricted stock awards vested		809,112
Employee Restricted Shares [Member] \| Share-based Compensation Award, Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of restricted stock awards vested		487,028
Non-Employee Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of restricted stock awards vested		235,103
Share-based compensation expense	$ 364,000	$ 968,000
Non-Employee Restricted Stock [Member] \| Share-based Compensation Award, Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of restricted stock awards vested		146,561
2014 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance				5,975,000
Common shares reserved for future issuance pursuant to future option grants	621,500	621,500
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
2014 Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of options to be granted under the Plan		10 years

Equity Incentive Plan - Summary of Stock Option Activity (Detail) - Stock Option shares in Thousands	6 Months Ended
	Jun. 30, 2015 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Number of Shares \| shares	410
Ending Balance, Number of Shares \| shares	410
Exercisable, Number of Shares \| shares	2
Granted, Weighted-Average Exercise Price per Share \| $ / shares	$ 6.32
Ending Balance, Weighted-Average Exercise Price per Share \| $ / shares	6.32
Exercisable, Weighted-Average Exercise Price per Share \| $ / shares	$ 6.32

Equity Incentive Plan - Summary of Weighted Average Assumptions of Fair Value of Stock Options Under Black-Scholes Option Pricing Model (Detail)	6 Months Ended
	Jun. 30, 2015 $ / shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value per share	$ 4.02
Expected volatility	70.80%
Risk free interest rate	1.80%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 29 days

Equity Incentive Plan - Summary of Restricted Share Activity (Detail) - Restricted Stock Awards shares in Thousands	6 Months Ended
	Jun. 30, 2015 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Beginning Balance, Number of Shares	4,533
Vested, Number of Shares	(634)
Ending Balance, Number of Shares	3,899
Vested, Number of Shares	1,044
Beginning Balance, Weighted-Average Grant Date Fair Value \| $ / shares	$ 0.002
Vested, Weighted-Average Grant Date Fair Value \| $ / shares	0.004
Ending Balance, Weighted-Average Grant Date Fair Value \| $ / shares	$ 0.003

Equity Incentive Plan - Summary of Share-based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 485	$ 1,129
Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	404	1,007
General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 81	$ 122

Related Party Transactions - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Feb. 28, 2015	Jan. 31, 2015	Dec. 31, 2014	Oct. 31, 2014
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
Agreement expiration date		Dec. 31, 2015
Agreement termination notice period		30 days
Management Fee, Description		We have a management services agreement with Araxes under which Araxes pays us a fixed $100,000 a month for management services. In addition, the agreement allows for Araxes to pay us an amount equal to the number of full time equivalents, or FTE, performing collaboration services for Araxes, at an annual FTE rate of $350,000, plus actual expenses as reasonably incurred. The agreement has an initial term expiring on December 31, 2015 and 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 December 31, 2015 or the expiration of the then-renewal term.
Director
Related Party Transaction [Line Items]
Office space sublease monthly rent		$ 5,000
Rent expense related to office space sublease	$ 24,000	$ 49,000
Sublease expiration date		Aug. 30, 2016
Management service agreement, fixed		$ 100,000
Management service agreement, full time equivalents performing collaboration services		$ 350,000
Wellspring Biosciences LLC
Related Party Transaction [Line Items]
Agreement expiration date		Dec. 31, 2015
Agreement termination notice period		30 days
Research and development services expense at full time equivalents rate		$ 400,000
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

Subsequent Events - Additional Information (Detail) - Cambridge Facilities Lease [Member] - Subsequent Event	Aug. 13, 2015 USD ($) ft²
Subsequent Event [Line Items]
Operating lease, area of space \| ft²	3,677
Security deposit	$ 44,000
Lease term period	60 months
Office space sublease monthly rent	$ 21,000
Operating lease rate of increase in annual rent	1.40%
Rent payable over the lease period	$ 1,300,000