Kura Oncology (KURA) 10-Q 1 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 30, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	KURA
Entity Registrant Name	Kura Oncology, Inc.
Entity Central Index Key	0001422143
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		45,214,920
Entity File Number	001-37620
Entity Tax Identification Number	611547851
Entity Address, Address Line One	3033 Science Park Road
Entity Address, Address Line Two	Suite 220
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	500-8800

Condensed Balance Sheets (Unaud

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	[1]
Current assets:
Cash and cash equivalents	$ 122,080	$ 16,119
Short-term investments	139,333	162,866
Accounts receivable, related party	111	224
Prepaid expenses and other current assets	2,380	1,988
Total current assets	263,904	181,197
Other long-term assets	1,587	1,166
Other long-term assets, related party	194	16
Total assets	265,685	182,379
Current liabilities:
Accounts payable and accrued expenses	10,878	13,385
Accounts payable and accrued expenses, related party	354	230
Total current liabilities	11,232	13,615
Long-term debt, net	7,500	7,500
Other long-term liabilities	372	279
Total liabilities	19,104	21,394
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; 45,189 and 38,148 shares issued and outstanding as of June 30, 2019 and December 31, 2018, respectively	5	4
Additional paid-in capital	425,035	310,849
Accumulated other comprehensive income (loss)	161	(131)
Accumulated deficit	(178,620)	(149,737)
Total stockholders' equity	246,581	160,985
Total liabilities and stockholders' equity	$ 265,685	$ 182,379
[1]	The balance sheet data at December 31, 2018 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 (Una_2

Condensed Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018	[1]
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	45,189,000	38,148,000
Common stock, shares outstanding	45,189,000	38,148,000
[1]	The balance sheet data at December 31, 2018 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 Statements of Operati

Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating Expenses:
Research and development	$ 11,342	$ 11,099	$ 21,671	$ 22,366
Research and development, related party	98	377	151	676
General and administrative	4,363	3,736	8,845	7,102
General and administrative, related party	88	64	175	123
Total operating expenses	15,891	15,276	30,842	30,267
Other Income (Expense):
Management fee income, related party	74	180	200	375
Interest income	1,022	624	2,052	1,074
Interest expense	(148)	(267)	(293)	(525)
Total other income	948	537	1,959	924
Net Loss	$ (14,943)	$ (14,739)	$ (28,883)	$ (29,343)
Net loss per share, basic and diluted	$ (0.38)	$ (0.45)	$ (0.75)	$ (0.91)
Weighted average number of shares used in computing net loss per share, basic and diluted	38,928	32,971	38,550	32,403
Comprehensive Loss:
Net loss	$ (14,943)	$ (14,739)	$ (28,883)	$ (29,343)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	143	(25)	292	(44)
Comprehensive Loss	$ (14,800)	$ (14,764)	$ (28,591)	$ (29,387)

Condensed Statements of Stockho

Condensed Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total		Common Stock	Additional Paid- In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ 79,865		$ 3	$ 169,201	$ (49)	$ (89,290)
Beginning balance (in shares) at Dec. 31, 2017			29,424
Issuance of common stock, net of offering costs	57,378			57,378
Issuance of common stock, net of offering costs, ( in shares)			3,137
Share-based compensation expense	4,415			4,415
Restricted stock awards vested	1			1
Restricted stock awards vested (in shares)			590
Issuance of common stock from exercise of options	125			125
Issuance of common stock from exercise of options (in shares)			22
Other comprehensive income (loss)	(44)				(44)
Net loss	(29,343)					(29,343)
Ending balance at Jun. 30, 2018	112,397		$ 3	231,120	(93)	(118,633)
Ending balance (in shares) at Jun. 30, 2018			33,173
Beginning balance at Mar. 31, 2018	124,800		$ 3	228,759	(68)	(103,894)
Beginning balance (in shares) at Mar. 31, 2018			32,856
Share-based compensation expense	2,236			2,236
Restricted stock awards vested (in shares)			295
Issuance of common stock from exercise of options	125			125
Issuance of common stock from exercise of options (in shares)			22
Other comprehensive income (loss)	(25)				(25)
Net loss	(14,739)					(14,739)
Ending balance at Jun. 30, 2018	112,397		$ 3	231,120	(93)	(118,633)
Ending balance (in shares) at Jun. 30, 2018			33,173
Beginning balance at Dec. 31, 2018	160,985	[1]	$ 4	310,849	(131)	(149,737)
Beginning balance (in shares) at Dec. 31, 2018			38,148
Issuance of common stock, net of offering costs	108,109		$ 1	108,108
Issuance of common stock, net of offering costs, ( in shares)			6,785
Share-based compensation expense	4,518			4,518
Issuance of common stock from exercise of options and employee stock purchase plan	1,560			1,560
Issuance of common stock from exercise of options and employee stock purchase plan (in shares)			256
Other comprehensive income (loss)	292				292
Net loss	(28,883)					(28,883)
Ending balance at Jun. 30, 2019	246,581		$ 5	425,035	161	(178,620)
Ending balance (in shares) at Jun. 30, 2019			45,189
Beginning balance at Mar. 31, 2019	149,565		$ 4	313,220	18	(163,677)
Beginning balance (in shares) at Mar. 31, 2019			38,169
Issuance of common stock, net of offering costs	108,109		$ 1	108,108
Issuance of common stock, net of offering costs, ( in shares)			6,785
Share-based compensation expense	2,249			2,249
Issuance of common stock from exercise of options and employee stock purchase plan	1,458			1,458
Issuance of common stock from exercise of options and employee stock purchase plan (in shares)			235
Other comprehensive income (loss)	143				143
Net loss	(14,943)					(14,943)
Ending balance at Jun. 30, 2019	$ 246,581		$ 5	$ 425,035	$ 161	$ (178,620)
Ending balance (in shares) at Jun. 30, 2019			45,189
[1]	The balance sheet data at December 31, 2018 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 Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018
Operating Activities
Net loss	$ (28,883)		$ (29,343)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	4,518		4,415
Non-cash interest expense			114
Depreciation expense			9
Amortization of premium and accretion of discount on marketable securities, net	(859)		(703)
Changes in operating assets and liabilities:
Accounts receivable, related party	129		(14)
Prepaid expenses and other current assets	(142)		(1,026)
Other long-term assets	(321)		(42)
Other long-term assets, related party	106
Accounts payable and accrued expenses	(3,124)		814
Accounts payable and accrued expenses, related party	(176)		221
Other long-term liabilities	70		112
Net cash used in operating activities	(28,682)		(25,443)
Investing Activities
Maturities and sales of marketable securities	126,556		80,993
Purchases of marketable securities	(101,872)		(106,850)
Net cash provided by (used in) investing activities	24,684		(25,857)
Financing Activities
Proceeds from issuance of common stock, net	108,399		57,650
Proceeds from exercise of stock options and purchases under employee stock purchase plan	1,560		125
Repayment of long-term debt			(250)
Net cash provided by financing activities	109,959		57,525
Net increase in cash and cash equivalents	105,961		6,225
Cash and cash equivalents at beginning of period	16,119	[1]	11,433
Cash and cash equivalents at end of period	$ 122,080		$ 17,658
[1]	The balance sheet data at December 31, 2018 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.

Organization and Basis of Prese

Organization and Basis of Presentation	6 Months Ended
	Jun. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Basis of Presentation	1. Organization and Basis of Presentation The Company 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, and we intend to pair them with molecular or cellular diagnostics to identify those patients most likely to respond to treatment. We plan to advance our product candidates through a combination of internal development and strategic partnerships and maintain significant development and commercial rights. References in these Notes to Unaudited Condensed Financial Statements to the “Company,” “we,” “our” or “us,” refer to Kura Oncology, Inc. Basis of Presentation The accompanying unaudited condensed financial statements should be read in conjunction with the audited financial statements and notes thereto in our Annual Report on Form 10-K for the fiscal year ended December 31, 2018, as filed with the Securities and Exchange Commission on March 5, 2019, from which we derived our balance sheet as of December 31, 2018. The accompanying unaudited 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 unaudited condensed financial statements do not include all of the information and notes required by GAAP for complete financial statements. The accompanying unaudited 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 unaudited condensed financial statements in accordance with GAAP requires our management to make estimates and assumptions that affect the amounts reported on our unaudited 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 Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Comprehensive Loss Comprehensive 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 of unrealized gains and losses on marketable securities and foreign currency. 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 shares and common stock equivalents outstanding for the period determined using the treasury-stock method. Dilutive common stock equivalents are comprised of outstanding stock options, an outstanding warrant, employee stock purchase plan rights and unvested restricted stock awards. 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, outstanding stock options, an outstanding warrant, employee stock purchase plan rights and unvested restricted stock awards are excluded from the calculation of diluted net loss per common share for the periods presented, 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, in thousands: Three and Six Months Ended June 30, 2019 2018 Stock options 4,102 3,097 Warrant 34 34 Employee stock purchase plan rights 4 — Unvested restricted stock awards — 202 Total 4,140 3,333 Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2016-02, Leases (Topic 842), which amended prior accounting standards for leases. ASU 2016-02 requires lessees to recognize right-of-use, or ROU, assets and lease liabilities on the balance sheet and requires expanded disclosures about leasing arrangements. We adopted the new lease standard on January 1, 2019, using the alternative modified transition method provided by ASU 2018-11 and did not retrospectively apply to prior periods. We elected the “package of practical expedients” permitted under the transition which allows us not to reassess our historical assessment of whether existing contracts are or contain a lease and the classification of existing lease arrangements, and to calculate the present value of the fixed payments without performing an allocation of lease and non-lease components. As a result of the adoption of the new standard, we recognized operating lease ROU assets and operating lease liabilities of $0.6 million on our unaudited condensed balance sheet as of January 1, 2019. ROU assets are recorded in Other Long-Term Assets and Other Long-Term Assets, Related Party on our unaudited condensed balance sheets. Current and non-current lease liabilities are recorded in Accounts Payable and Accrued Expenses and Accounts Payable and Accrued Expenses, Related Party and Other Long-Term Liabilities and Other Long-Term Liabilities, Related Party, respectively, on our unaudited condensed balance sheets. The adoption of the new lease standard had no impact on our accumulated deficit. The adoption of the new lease standard did not have a material impact on our results of operations and cash flows. See Note 6, Leases, for further details. In June 2018, the FASB issued ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting (Topic 718), which expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The new guidance is intended to simplify aspects of share-based compensation issued to nonemployees by aligning the accounting for share-based payment awards issued to employees and nonemployees as it relates to measurement date and impact of performance conditions. This standard is effective for fiscal years beginning after December 15, 2018, and interim periods within those annual periods. We adopted ASU 2018-07 on January 1, 2019. The adoption of ASU 2018-07 did not have a material impact on our unaudited condensed financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments, which changes the impairment model for most financial assets and certain other instruments. For trade receivables and other instruments, entities will be required to use a new forward-looking expected loss model that generally will result in the earlier recognition of allowances for losses. For available-for-sale debt securities with unrealized losses, the losses will be recognized as allowances rather than as reductions in the amortized cost of the securities. This guidance is effective for annual reporting periods beginning after December 15, 2019, including interim periods within those years, with early adoption permitted only as of annual reporting periods beginning after December 15, 2018. We are currently evaluating the timing and impact of the adoption of ASU 2016-13 on our unaudited condensed In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. The new guidance modifies the disclosure requirements on fair value measurements in Topic 820. The amendments in ASU 2018-13 are effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. We are currently evaluating the timing and impact of the adoption of ASU 2018-13 on our unaudited condensed financial statements or related financial statement disclosures.

Investments

Investments	6 Months Ended
	Jun. 30, 2019
Investments All Other Investments [Abstract]
Investments	3. Investments We invest in available-for-sale securities consisting of money market funds, U.S. Treasury securities, corporate debt securities and commercial paper. Available-for-sale securities are classified as part of either cash and cash equivalents or short-term investments on our unaudited condensed balance sheets. The following tables summarize, by major security type, our investments that are measured at fair value on a recurring basis, in thousands: As of June 30, 2019 Maturities (years) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents: Money market funds 1 or less $ 114,910 $ — $ — $ 114,910 Short-term investments: Corporate debt securities 2 or less 96,346 144 (19 ) 96,471 U.S. Treasury securities 1 or less 39,852 37 (1 ) 39,888 Commercial paper 1 or less 2,974 — — 2,974 Total short-term investments 139,172 181 (20 ) 139,333 Total $ 254,082 $ 181 $ (20 ) $ 254,243 As of December 31, 2018 Maturities (years) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents: Money market funds 1 or less $ 8,508 $ — $ — $ 8,508 Short-term investments: Corporate debt securities 1 or less 56,779 6 (77 ) 56,708 U.S. Treasury securities 1 or less 39,780 — (57 ) 39,723 Commercial paper 1 or less 66,435 — — 66,435 Total short-term investments 162,994 6 (134 ) 162,866 Total $ 171,502 $ 6 $ (134 ) $ 171,374 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 June 30, 2019, $136.3 million of our short-term investments had maturities less than one year, and $3.0 million had maturities between one to two years. Realized gains and losses were de minimus for the three and six months ended June 30, 2019. As of June 30, 2019, $39.0 million of our marketable securities were in immaterial gross unrealized loss positions. At each reporting date, we perform an evaluation of our marketable securities to determine if any unrealized losses are other-than-temporary. Factors considered in determining whether a loss is other-than-temporary include (i) the financial strength of the issuing institution, (ii) the length of time and extent for which fair value has been less than the cost basis and (iii) our intent and ability to hold our investments in unrealized loss positions until their amortized cost basis has been recovered. Based on our evaluation, we determined that our unrealized losses were not other-than-temporary at June 30, 2019 and December 31, 2018.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements As a basis for considering assumptions that market participants would use in pricing an asset or liability, 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. 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 and commercial paper, 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, in thousands: As of June 30, 2019 Balance Level 1 Level 2 Cash equivalents: Money market funds $ 114,910 $ 114,910 $ — Short-term investments: Corporate debt securities 96,471 — 96,471 U.S. Treasury securities 39,888 39,888 — Commercial paper 2,974 — 2,974 Total short-term investments 139,333 39,888 99,445 Total $ 254,243 $ 154,798 $ 99,445 As of December 31, 2018 Balance Level 1 Level 2 Cash equivalents: Money market funds $ 8,508 $ 8,508 $ — Short-term investments: Corporate debt securities 56,708 — 56,708 U.S. Treasury securities 39,723 39,723 — Commercial paper 66,435 — 66,435 Total short-term investments 162,866 39,723 123,143 Total $ 171,374 $ 48,231 $ 123,143 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.

Accounts Payable and Accrued Li

Accounts Payable and Accrued Liabilities	6 Months Ended
	Jun. 30, 2019
Payables And Accruals [Abstract]
Accounts Payable and Accrued Liabilities	5. Accounts Payable and Accrued Liabilities Accounts payable and accrued liabilities consisted of the following, in thousands: June 30, 2019 December 31, 2018 Accounts payable $ 3,556 $ 3,890 Accrued research and development expenses 4,019 5,550 Accrued compensation and benefits 2,278 3,437 Other accrued expenses 1,025 508 Total accounts payable and accrued expenses $ 10,878 $ 13,385

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	6. Leases We determine if an arrangement is a lease or contains lease components at inception. For operating leases with an initial term greater than 12 months, we recognize operating lease ROU assets and operating lease liabilities based on the present value of lease payments over the lease term at commencement date. Operating lease ROU assets are comprised of the lease liability plus any lease payments made and excludes lease incentives. Lease terms may include options to extend or terminate when we are reasonably certain that the option will be exercised. For our operating leases, we generally cannot determine the interest rate implicit in the lease, in which case we use our incremental borrowing rate as the discount rate for the lease. We estimate our incremental borrowing rate for our operating leases based on what we would normally pay to borrow on a collateralized basis over a similar term for an amount equal to the lease payments. Operating lease expense is recognized on a straight-line basis over the lease term. If a lease is modified, the modified contract is evaluated to determine whether it is or contains a lease. If a lease continues to exist, the lease modification is determined to be a separate contract when the modification grants the lessee an additional right of use that is not included in the original lease and the lease payments increase commensurate with the standalone price for the additional ROU. A lease modification that results in a separate contract will be accounted for in the same manner as a new lease. For a modification that is not a separate contract, we reassess the lease classification using the modified terms and conditions and the facts and circumstances as of the effective date of the modification and recognize the amount of the remeasurement of the lease liability for the modified lease as an adjustment to the corresponding ROU asset. We have a sublease with a related party for office space in San Diego, California and a lease for office space in Cambridge, Massachusetts, that existed before January 1, 2019 and were classified as operating leases. In March 2019, the sublease was amended to extend the expiration date from October 31, 2019 to April 30, 2020 with the monthly rent increased from approximately $16,000 to approximately $24,000 per month effective November 1, 2019. See Note 9, Related Party Transactions for further details of the sublease. We determined the sublease amendment did not modify the ROU asset and, therefore, was not a separate contract. Accordingly, we reassessed the lease classification and concluded the operating lease classification remained appropriate. The modified lease terms were included in determining the present value of lease payments for the sublease at the modification date. As such, we recognized an adjustment of approximately $0.1 million as an increase to the sublease liability and ROU asset. We do not have any new operating leases nor any finance leases as of June 30, 2019. Operating lease expense was as follows, in thousands: Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Operating lease cost $ 67 $ 135 Operating lease cost, related party 54 112 Total operating lease costs $ 121 $ 247 Supplemental cash flow information related to our operating leases was as follows, in thousands: Six Months Ended June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 134 Operating cash flows from operating leases, related party 98 Total cash paid for amounts included in the measurement of lease liabilities $ 232 ROU assets obtained in exchange for operating lease liabilities $ 122 ROU assets obtained in exchange for operating lease liabilities, related party 107 Total ROU assets obtained in exchange for operating lease liabilities $ 229 Supplemental balance sheet information related to our operating leases was as follows, in thousands (except lease term and discount rate): June 30, 2019 Operating lease ROU assets $ 283 Operating lease ROU assets, related party 194 Total operating lease ROU assets $ 477 Current lease liabilities $ 263 Current lease liabilities, related party 207 Non-current lease liabilities 23 Total operating lease liabilities $ 493 Weighted-average remaining lease term (in years) 1.0 Weighted-average discount rate 6.5 % Maturities of lease liabilities are as follows, in thousands: Year Ending December 31, 2019 (remaining) $ 252 2020 256 Total lease payments 508 Less: imputed interest (15 ) Total operating lease liabilities $ 493

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2019
Equity [Abstract]
Stockholders' Equity	7. Stockholders’ Equity In June 2019, we completed a public offering in which we sold an aggregate of 6,785,000 shares of common stock at a price of $17.00 per share. Net proceeds from the public offering, after deducting underwriting discounts, commissions and offering expenses, were approximately $108.1 million.

Share-Based Compensation

Share-Based Compensation	6 Months Ended
	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation	8. Share-Based Compensation The following table summarizes share-based compensation expense for all share-based compensation arrangements, in thousands: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Research and development $ 884 $ 1,369 $ 1,681 $ 2,808 General and administrative 1,365 867 2,837 1,607 Total share-based compensation expense $ 2,249 $ 2,236 $ 4,518 $ 4,415 As of June 30, 2019, unrecognized compensation costs related to employee stock options was approximately $25.0 million, which is expected to be recognized over a weighted average period of approximately 2.8 years.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	9. Related Party Transactions Our president and chief executive officer is also the sole managing member of Araxes Pharma LLC, or • Facility Sublease We sublease office space in San Diego, California from Wellspring Biosciences, Inc., or Wellspring, a wholly owned subsidiary of Araxes. The sublease commenced in June 2017 and would have expired on October 31, 2019. In March 2019, the sublease was amended to extend until April 30, 2020, and the monthly rent will increase to approximately $24,000 per month effective November 1, 2019, corresponding to the increase in Wellspring’s monthly rent, . • Management Fees We have a management services agreement with Araxes pursuant to which Araxes pays us monthly fees for management services calculated based on costs incurred by us in the provision of services to Araxes, plus a reasonable mark-up. For the three months ended June 30, 2019 and 2018, we recorded approximately $0.1 million and $0.2 million, respectively, and for the six months ended June 30, 2019 and 2018, we recorded approximately $0.2 million and $0.4 million, respectively, in management fee income. 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 $374,000, 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 three and six months ended June 30, 2019 and 2018, we recorded reimbursements of approximately $0.1 million in each period for research and development services provided to Araxes, which was recorded as a reduction to research and development expenses, related party, on our unaudited condensed statements of operations and comprehensive loss. As of June 30, 2019 and December 31, 2018, approximately $0.1 million and $0.2 million, respectively, related to management fees and reimbursements of research and development services are included in accounts receivable, related party on our unaudited condensed balance sheets. • Services Agreement We have a services agreement with Wellspring pursuant to which we pay Wellspring for research and development services provided to us in 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 three months ended June 30, 2019 and 2018, we recognized approximately $0.1 million and $0.4 million, respectively, and for the six months ended June 30, 2019 and 2018, we recognized $0.1 million and $0.7 million, respectively, from research and development services provided to us under this agreement as research and development expense, related party on our unaudited condensed statements of operations and comprehensive loss. As of June 30, 2019 and December 31, 2018, approximately $0.1 million and $0.2 million, respectively, related to research and development services under this agreement are included in accounts payable and accrued expenses, related party on our unaudited condensed balance sheets.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Comprehensive Loss	Comprehensive Loss Comprehensive 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 of unrealized gains and losses on marketable securities and foreign currency.
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 shares and common stock equivalents outstanding for the period determined using the treasury-stock method. Dilutive common stock equivalents are comprised of outstanding stock options, an outstanding warrant, employee stock purchase plan rights and unvested restricted stock awards. 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, outstanding stock options, an outstanding warrant, employee stock purchase plan rights and unvested restricted stock awards are excluded from the calculation of diluted net loss per common share for the periods presented, 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, in thousands: Three and Six Months Ended June 30, 2019 2018 Stock options 4,102 3,097 Warrant 34 34 Employee stock purchase plan rights 4 — Unvested restricted stock awards — 202 Total 4,140 3,333
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2016-02, Leases (Topic 842), which amended prior accounting standards for leases. ASU 2016-02 requires lessees to recognize right-of-use, or ROU, assets and lease liabilities on the balance sheet and requires expanded disclosures about leasing arrangements. We adopted the new lease standard on January 1, 2019, using the alternative modified transition method provided by ASU 2018-11 and did not retrospectively apply to prior periods. We elected the “package of practical expedients” permitted under the transition which allows us not to reassess our historical assessment of whether existing contracts are or contain a lease and the classification of existing lease arrangements, and to calculate the present value of the fixed payments without performing an allocation of lease and non-lease components. As a result of the adoption of the new standard, we recognized operating lease ROU assets and operating lease liabilities of $0.6 million on our unaudited condensed balance sheet as of January 1, 2019. ROU assets are recorded in Other Long-Term Assets and Other Long-Term Assets, Related Party on our unaudited condensed balance sheets. Current and non-current lease liabilities are recorded in Accounts Payable and Accrued Expenses and Accounts Payable and Accrued Expenses, Related Party and Other Long-Term Liabilities and Other Long-Term Liabilities, Related Party, respectively, on our unaudited condensed balance sheets. The adoption of the new lease standard had no impact on our accumulated deficit. The adoption of the new lease standard did not have a material impact on our results of operations and cash flows. See Note 6, Leases, for further details. In June 2018, the FASB issued ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting (Topic 718), which expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The new guidance is intended to simplify aspects of share-based compensation issued to nonemployees by aligning the accounting for share-based payment awards issued to employees and nonemployees as it relates to measurement date and impact of performance conditions. This standard is effective for fiscal years beginning after December 15, 2018, and interim periods within those annual periods. We adopted ASU 2018-07 on January 1, 2019. The adoption of ASU 2018-07 did not have a material impact on our unaudited condensed financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments, which changes the impairment model for most financial assets and certain other instruments. For trade receivables and other instruments, entities will be required to use a new forward-looking expected loss model that generally will result in the earlier recognition of allowances for losses. For available-for-sale debt securities with unrealized losses, the losses will be recognized as allowances rather than as reductions in the amortized cost of the securities. This guidance is effective for annual reporting periods beginning after December 15, 2019, including interim periods within those years, with early adoption permitted only as of annual reporting periods beginning after December 15, 2018. We are currently evaluating the timing and impact of the adoption of ASU 2016-13 on our unaudited condensed In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. The new guidance modifies the disclosure requirements on fair value measurements in Topic 820. The amendments in ASU 2018-13 are effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. We are currently evaluating the timing and impact of the adoption of ASU 2018-13 on our unaudited condensed financial statements or related financial statement disclosures.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2019
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, in thousands: Three and Six Months Ended June 30, 2019 2018 Stock options 4,102 3,097 Warrant 34 34 Employee stock purchase plan rights 4 — Unvested restricted stock awards — 202 Total 4,140 3,333

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2019
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, in thousands: As of June 30, 2019 Maturities (years) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents: Money market funds 1 or less $ 114,910 $ — $ — $ 114,910 Short-term investments: Corporate debt securities 2 or less 96,346 144 (19 ) 96,471 U.S. Treasury securities 1 or less 39,852 37 (1 ) 39,888 Commercial paper 1 or less 2,974 — — 2,974 Total short-term investments 139,172 181 (20 ) 139,333 Total $ 254,082 $ 181 $ (20 ) $ 254,243 As of December 31, 2018 Maturities (years) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Cash equivalents: Money market funds 1 or less $ 8,508 $ — $ — $ 8,508 Short-term investments: Corporate debt securities 1 or less 56,779 6 (77 ) 56,708 U.S. Treasury securities 1 or less 39,780 — (57 ) 39,723 Commercial paper 1 or less 66,435 — — 66,435 Total short-term investments 162,994 6 (134 ) 162,866 Total $ 171,502 $ 6 $ (134 ) $ 171,374

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
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, in thousands: As of June 30, 2019 Balance Level 1 Level 2 Cash equivalents: Money market funds $ 114,910 $ 114,910 $ — Short-term investments: Corporate debt securities 96,471 — 96,471 U.S. Treasury securities 39,888 39,888 — Commercial paper 2,974 — 2,974 Total short-term investments 139,333 39,888 99,445 Total $ 254,243 $ 154,798 $ 99,445 As of December 31, 2018 Balance Level 1 Level 2 Cash equivalents: Money market funds $ 8,508 $ 8,508 $ — Short-term investments: Corporate debt securities 56,708 — 56,708 U.S. Treasury securities 39,723 39,723 — Commercial paper 66,435 — 66,435 Total short-term investments 162,866 39,723 123,143 Total $ 171,374 $ 48,231 $ 123,143

Accounts Payable and Accrued _2

Accounts Payable and Accrued Liabilities (Tables)	6 Months Ended
	Jun. 30, 2019
Payables And Accruals [Abstract]
Accounts Payable and Accrued Liabilities	Accounts payable and accrued liabilities consisted of the following, in thousands: June 30, 2019 December 31, 2018 Accounts payable $ 3,556 $ 3,890 Accrued research and development expenses 4,019 5,550 Accrued compensation and benefits 2,278 3,437 Other accrued expenses 1,025 508 Total accounts payable and accrued expenses $ 10,878 $ 13,385

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Schedule of Operating Lease Expense	Operating lease expense was as follows, in thousands: Three Months Ended Six Months Ended June 30, 2019 June 30, 2019 Operating lease cost $ 67 $ 135 Operating lease cost, related party 54 112 Total operating lease costs $ 121 $ 247
Schedule of Supplemental Cash Flow Information Related to Operating Leases	Supplemental cash flow information related to our operating leases was as follows, in thousands: Six Months Ended June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 134 Operating cash flows from operating leases, related party 98 Total cash paid for amounts included in the measurement of lease liabilities $ 232 ROU assets obtained in exchange for operating lease liabilities $ 122 ROU assets obtained in exchange for operating lease liabilities, related party 107 Total ROU assets obtained in exchange for operating lease liabilities $ 229
Schedule of Supplemental Balance Sheet Information Related to Operating Leases	Supplemental balance sheet information related to our operating leases was as follows, in thousands (except lease term and discount rate): June 30, 2019 Operating lease ROU assets $ 283 Operating lease ROU assets, related party 194 Total operating lease ROU assets $ 477 Current lease liabilities $ 263 Current lease liabilities, related party 207 Non-current lease liabilities 23 Total operating lease liabilities $ 493 Weighted-average remaining lease term (in years) 1.0 Weighted-average discount rate 6.5 %
Schedule of Maturities of Lease Liabilities	Maturities of lease liabilities are as follows, in thousands: Year Ending December 31, 2019 (remaining) $ 252 2020 256 Total lease payments 508 Less: imputed interest (15 ) Total operating lease liabilities $ 493

Share-Based Compensation (Table

Share-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Share-based Compensation Expense	The following table summarizes share-based compensation expense for all share-based compensation arrangements, in thousands: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Research and development $ 884 $ 1,369 $ 1,681 $ 2,808 General and administrative 1,365 867 2,837 1,607 Total share-based compensation expense $ 2,249 $ 2,236 $ 4,518 $ 4,415

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Summary of Number of Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	4,140	3,333
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	4,102	3,097
Warrant
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	34	34
Employee Stock Purchase Plan Rights
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	4
Unvested Restricted Stock Awards
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities		202

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
Accounting Policies [Abstract]
Operating leases, right of use asset	$ 477	$ 600
Operating leases, liability	$ 493	$ 600

Investments - Investments Measu

Investments - Investments Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Short-term investments, Fair Value	$ 139,333	$ 162,866	[1]
Fair Value Measurements on Recurring Basis
Schedule Of Available For Sale Securities [Line Items]
Short-term investments, Amortized Cost	139,172	162,994
Short-term investments, Unrealized Gains	181	6
Short-term investments, Unrealized Losses	(20)	(134)
Short-term investments, Fair Value	139,333	162,866
Cash equivalents and Short-term investments, Amortized Cost	254,082	171,502
Cash equivalents and Short-term investments, Unrealized Gains	181	6
Cash equivalents and Short-term investments, Unrealized Losses	(20)	(134)
Cash equivalents and Short-term investments, Fair Value	$ 254,243	$ 171,374
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	$ 114,910	$ 8,508
Cash equivalents, Fair Value	$ 114,910	$ 8,508
Fair Value Measurements on Recurring Basis | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Maturities (years)	2 or less	1 or less
Short-term investments, Amortized Cost	$ 96,346	$ 56,779
Short-term investments, Unrealized Gains	144	6
Short-term investments, Unrealized Losses	(19)	(77)
Short-term investments, Fair Value	$ 96,471	$ 56,708
Fair Value Measurements on Recurring Basis | U.S. Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Maturities (years)	1 or less	1 or less
Short-term investments, Amortized Cost	$ 39,852	$ 39,780
Short-term investments, Unrealized Gains	37
Short-term investments, Unrealized Losses	(1)	(57)
Short-term investments, Fair Value	$ 39,888	$ 39,723
Fair Value Measurements on Recurring Basis | Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Maturities (years)	1 or less	1 or less
Short-term investments, Amortized Cost	$ 2,974	$ 66,435
Short-term investments, Fair Value	$ 2,974	$ 66,435
[1]	The balance sheet data at December 31, 2018 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.

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Investments All Other Investments [Abstract]
Marketable securities gross unrealized loss positions	$ 39,000,000
Short-term investments maturities, description	As of June 30, 2019, $136.3 million of our short-term investments had maturities less than one year, and $3.0 million had maturities between one to two years
Short-term investments with maturities less than one year	$ 136,300,000
Short-term investments with maturities between one to two years	3,000,000
Unrealized losses other-than-temporary	$ 0	$ 0

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values of Investment Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 139,333	$ 162,866	[1]
Fair Value Measurements on Recurring Basis
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	139,333	162,866
Cash equivalents and short-term investments	254,243	171,374
Fair Value Measurements on Recurring Basis | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	39,888	39,723
Cash equivalents and short-term investments	154,798	48,231
Fair Value Measurements on Recurring Basis | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	99,445	123,143
Cash equivalents and short-term investments	99,445	123,143
Fair Value Measurements on Recurring Basis | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	114,910	8,508
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	114,910	8,508
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	96,471	56,708
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	96,471	56,708
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	39,888	39,723
Fair Value Measurements on Recurring Basis | U.S. Treasury Securities | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	39,888	39,723
Fair Value Measurements on Recurring Basis | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	2,974	66,435
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	$ 2,974	$ 66,435
[1]	The balance sheet data at December 31, 2018 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 _3

Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accounts payable	$ 3,556	$ 3,890
Accrued research and development expenses	4,019	5,550
Accrued compensation and benefits	2,278	3,437
Other accrued expenses	1,025	508
Total accounts payable and accrued expenses	$ 10,878	$ 13,385	[1]
[1]	The balance sheet data at December 31, 2018 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.

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($)	Nov. 01, 2019	Jun. 01, 2017	Mar. 31, 2019	Jun. 30, 2019	Jan. 01, 2019
Lessee Lease Description [Line Items]
Increase in operating lease ROU asset				$ 477,000	$ 600,000
Wellspring Biosciences Inc | San Diego, California
Lessee Lease Description [Line Items]
Sublease expiration date		Oct. 31, 2019
Sublease extended date			Apr. 30, 2020
Amended sublease effective date			Nov. 1, 2019
Increase in sublease liability			$ 100,000
Increase in operating lease ROU asset			$ 100,000
Wellspring Biosciences Inc | San Diego, California | Monthly
Lessee Lease Description [Line Items]
Rent expense		$ 16,000
Wellspring Biosciences Inc | San Diego, California | Monthly | Scenario Forecast
Lessee Lease Description [Line Items]
Rent expense	$ 24,000

Leases - Schedule of Operating

Leases - Schedule of Operating Lease Expense (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Lessee Lease Description [Line Items]
Operating lease costs	$ 121	$ 247
Cambridge. MA Office Lease
Lessee Lease Description [Line Items]
Operating lease costs	67	135
Wellspring Biosciences Inc
Lessee Lease Description [Line Items]
Operating lease costs	$ 54	$ 112

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information Related to Operating Leases (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 232
ROU assets obtained in exchange for operating lease liabilities	229
Cambridge. MA Office Lease
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	134
ROU assets obtained in exchange for operating lease liabilities	122
Wellspring Biosciences Inc
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	98
ROU assets obtained in exchange for operating lease liabilities	$ 107

Leases - Schedule of Suppleme_2

Leases - Schedule of Supplemental Balance Sheet Information Related to Operating Leases (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
Lessee Lease Description [Line Items]
Operating lease ROU assets	$ 477	$ 600
Total operating lease liabilities	$ 493	$ 600
Weighted-average remaining lease term (in years)	1 year
Weighted-average discount rate	6.50%
Cambridge. MA Office Lease
Lessee Lease Description [Line Items]
Operating lease ROU assets	$ 283
Current lease liabilities	263
Non-current lease liabilities	23
Wellspring Biosciences Inc
Lessee Lease Description [Line Items]
Operating lease ROU assets, related party	194
Current lease liabilities, related party	$ 207

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
Leases [Abstract]
2019 (remaining)	$ 252
2020	256
Total lease payments	508
Less: imputed interest	(15)
Total operating lease liabilities	$ 493	$ 600

Stockholder's Equity - Addition

Stockholder's Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018
Stockholders' Equity Note [Abstract]
Common stock, shares issued	6,785,000
Common stock, issued price per share	$ 17	$ 17
Proceeds from issuance of common stock, net	$ 108,100	$ 108,399	$ 57,650

Share-Based Compensation - Summ

Share-Based Compensation - Summary of Share-based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 2,249	$ 2,236	$ 4,518	$ 4,415
Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	884	1,369	1,681	2,808
General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 1,365	$ 867	$ 2,837	$ 1,607

Share-Based Compensation - Addi

Share-Based Compensation - Additional Information (Detail) - Employee Stock Option $ in Millions	6 Months Ended
	Jun. 30, 2019USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized Expense	$ 25
Weighted average service period	2 years 9 months 18 days

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	Jan. 02, 2019	Jun. 01, 2017	Oct. 01, 2014	Mar. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Management fee income					$ 74,000	$ 180,000	$ 200,000	$ 375,000
Accounts receivable, related party					111,000		111,000		$ 224,000	[1]
Research and development, related party					98,000	377,000	151,000	676,000
Accounts payable and accrued expenses, related party					354,000		354,000		230,000	[1]
Wellspring Biosciences Inc | San Diego, California
Related Party Transaction [Line Items]
Sublease commencement date		Jun. 30, 2017
Sublease expiration date		Oct. 31, 2019
Sublease extended date				Apr. 30, 2020
Amended sublease effective date				Nov. 1, 2019
Wellspring Biosciences Inc | Sublease | San Diego, California
Related Party Transaction [Line Items]
Rent expense related to office space sublease					100,000	100,000	$ 200,000	200,000
Wellspring Biosciences Inc | Monthly | San Diego, California
Related Party Transaction [Line Items]
Rent expense related to office space sublease				$ 24,000
Araxes Pharma LLC | Management Fees
Related Party Transaction [Line Items]
Research and development services reimbursement, description							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 $374,000, 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 fee income					100,000	200,000	$ 200,000	400,000
Service Agreement for research and development	$ 374,000
Agreement expiration date			Dec. 31, 2015
Agreement termination notice period			30 days
Reimbursements of research and development services for related party					100,000	100,000	100,000	100,000
Accounts receivable, related party					100,000		$ 100,000		200,000
Service Agreements | Wellspring Biosciences Inc
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
Research and development expense payment, description							We have a services agreement with Wellspring pursuant to which we pay Wellspring for research and development services provided to us in 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.
Research and development, related party					100,000	$ 400,000	$ 100,000	$ 700,000
Accounts payable and accrued expenses, related party					$ 100,000		$ 100,000		$ 200,000
[1]	The balance sheet data at December 31, 2018 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.