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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Trading Symbol	CRNX
Entity Registrant Name	Crinetics Pharmaceuticals, Inc.
Entity Central Index Key	0001658247
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		24,036,983

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 169,654	$ 14,192
Prepaid expenses and other current assets	1,387	973
Total current assets	171,041	15,165
Property and equipment, net	4,353	400
Restricted cash	500
Other long-term assets	789	33
Total assets	176,683	15,598
Current liabilities:
Accounts payable	1,398	403
Accrued expenses	4,116	494
Total current liabilities	5,514	897
Deferred rent	3,437	20
Unvested stock liability	209	3
Total liabilities	9,160	920
Commitments and contingencies
Convertible preferred stock, $0.001 par; no shares authorized, issued and outstanding at September 30, 2018; 38,350,914 shares authorized, 28,763,179 shares issued and outstanding, liquidation preference of $30,000 at December 31, 2017		29,700
Stockholders’ equity (deficit):
Preferred stock, $0.001 par; 10,000,000 shares authorized, no shares issued or outstanding at September 30, 2018; no shares authorized, issued or outstanding at December 31, 2017
Common stock, $0.001 par; 200,000,000 shares authorized, 24,168,029 shares issued and 24,034,988 shares outstanding at September 30, 2018; 50,500,000 shares authorized, 2,076,171 shares issued and 1,549,575 shares outstanding at December 31, 2017	24	1
Additional paid-in capital	202,384	1,242
Accumulated deficit	(34,885)	(16,265)
Total stockholders’ equity (deficit)	167,523	(15,022)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 176,683	$ 15,598

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	50,500,000
Common stock, shares issued	24,168,029	2,076,171
Common stock, shares outstanding	24,034,988	1,549,575
Convertible Preferred Stock
Temporary equity, par value	$ 0.001	$ 0.001
Temporary equity, shares authorized	0	38,350,914
Temporary equity, shares issued	0	28,763,179
Temporary equity, shares outstanding	0	28,763,179
Temporary equity, liquidation preference		$ 30,000

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Grant revenues	$ 548	$ 640	$ 1,647	$ 1,517
Type of revenue [Extensible list]	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember	us-gaap:GrantMember
Operating expenses:
Research and development	$ 6,886	$ 2,523	$ 16,828	$ 6,671
General and administrative	1,732	491	4,098	1,472
Total operating expenses	8,618	3,014	20,926	8,143
Loss from operations	(8,070)	(2,374)	(19,279)	(6,626)
Other income (expense):
Interest income	534	6	749	20
Interest expense		(2)		(7)
Other income (expense)	(52)	(12)	(90)	(23)
Total other income (expense), net	482	(8)	659	(10)
Net loss	$ (7,588)	$ (2,382)	$ (18,620)	$ (6,636)
Net loss per share:
Net loss per share – basic and diluted	$ (0.38)	$ (1.67)	$ (2.29)	$ (5.00)
Weighted-average shares outstanding – basic and diluted	20,016	1,430	8,131	1,326

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (18,620)	$ (6,636)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	1,473	199
Depreciation and amortization	263	80
Other	11
Increase (decrease) in cash resulting from changes in:
Prepaid expenses and other assets	(1,170)	(658)
Accounts payable and accrued expenses	4,480	35
Deferred rent	113	12
Net cash used in operating activities	(13,450)	(6,968)
Cash flows from investing activities:
Purchases of property and equipment	(777)	(73)
Net cash used in investing activities	(777)	(73)
Financing activities:
Proceeds from issuance of convertible preferred stock, net of issuance costs	63,266	4,722
Proceeds from issuance of common stock, net	106,472
Proceeds from exercise of common stock options	451	66
Repayment of borrowings under long-term debt		(36)
Net cash provided by financing activities	170,189	4,752
Net change in cash, cash equivalents and restricted cash	155,962	(2,289)
Cash, cash equivalents and restricted cash at beginning of period	14,192	12,152
Cash, cash equivalents and restricted cash at end of period	170,154	9,863
Supplemental disclosures of cash flow information:
Cash paid for interest		$ 7
Noncash investing and financing activities:
Change in unvested stock liability	(14)
Accrued but unpaid property and equipment purchases	146
Tenant improvement allowance	$ 3,304

Organization and Basis of Presentation	9 Months Ended
Organization and Basis of Presentation	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Basis of Presentation	1. ORGANIZATION AND BASIS OF PRESENTATION Description of Business Crinetics Pharmaceuticals, Inc. (the “Company”) is a clinical stage pharmaceutical company incorporated in Delaware on November 18, 2008 and based in San Diego, California. The Company is focused on the discovery, development and commercialization of novel therapeutics for rare endocrine diseases and endocrine-related tumors. In January 2017, the Company established a wholly-owned Australian subsidiary, Crinetics Australia Pty Ltd (“CAPL”), in order to conduct various preclinical and clinical activities for its development candidates. Reverse Stock Split On July 6, 2018, the Company effected a 1-for-3.29 reverse stock split of its common stock. The par value and the authorized shares of the common stock were not adjusted as a result of the reverse stock split. The reverse stock split resulted in an adjustment to the conversion prices of the Company’s Series A and B preferred stock to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying condensed consolidated financial statements and notes to the condensed consolidated financial statements give retroactive effect to the reverse stock split for all periods presented. Segment Reporting Operating segments are identified as components of an enterprise about which discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment. Principles of Consolidation and Foreign Currency Transactions The condensed consolidated financial statements include the accounts of the Company and CAPL. All intercompany accounts and transactions have been eliminated in consolidation. The functional currency of both the Company and CAPL is the U.S. dollar. The Company’s assets and liabilities that are not denominated in the functional currency are remeasured into U.S. dollars at foreign currency exchange rates in effect at the balance sheet date except for nonmonetary assets, which are remeasured at historical foreign currency exchange rates in effect at the date of transaction. Net realized and unrealized gains and losses from foreign currency transactions and remeasurement are reported in other income (expense), in the condensed consolidated statements of operations and were not material for all periods presented. Unaudited Interim Financial Information The accompanying interim condensed consolidated balance sheet as of September 30, 2018, the condensed consolidated statements of operations for the three and nine months ended September 30, 2018 and 2017, and the statements of cash flows for the nine months ended September 30, 2018 and 2017, and the related disclosures are unaudited. In management’s opinion, the unaudited interim financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of September 30, 2018 and the results of its operations and cash flows for the three and nine months ended September 30, 2018 and 2017 in accordance with U.S. GAAP. The results for the three and nine months ended September 30, 2018 are not necessarily indicative of the results expected for the full fiscal year or any other interim period. Liquidity and Going Concern From inception, the Company has devoted substantially all of its efforts to drug discovery and development and conducting preclinical studies and clinical trials. The Company has a limited operating history and the sales and income potential of the Company’s business and market are unproven. Successful transition to attaining profitable operations is dependent upon achieving a level of revenues adequate to support the Company’s cost structure. As of September 30, 2018, the Company had $169.7 million in unrestricted cash and cash equivalents. The Company believes it has sufficient cash to meet its funding requirements for at least the next 12 months. However, the Company has experienced net losses and negative cash flows from operating activities since its inception and has an accumulated deficit of $34.9 million as of September 30, 2018. The Company expects to continue to incur net losses for the foreseeable future and believes it will need to raise substantial additional capital to accomplish its business plan over the next several years. The Company plans to continue to fund its losses from operations and capital funding needs through a combination of equity offerings, debt financings or other sources, including potentially collaborations, licenses and other similar arrangements. If the Company is not able to secure adequate additional funding, the Company may be forced to make reductions in spending, extend payment terms with suppliers, liquidate assets where possible, or suspend or curtail planned programs. Any of these actions could materially harm the Company’s business, results of operations and future prospects. There can be no assurance as to the availability or terms upon which such financing and capital might be available in the future.

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Use of Estimates The Company’s condensed consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The preparation of the Company’s condensed consolidated financial statements requires it to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s condensed consolidated financial statements and accompanying notes. The most significant estimates in the Company’s condensed consolidated financial statements relate to revenue recognition, accrued amounts receivable under the Australian research and development tax incentive program, accrued expenses, and the assumptions underlying the determination of the fair value of equity awards for purposes of determining stock-based compensation. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions. Fair Value Measurements The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or non-recurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1: Observable inputs such as quoted prices in active markets. Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly. Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. The carrying amounts of the Company’s current financial assets, restricted cash and current financial liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments. As of each of September 30, 2018, and December 31, 2017, the Company had no financial assets measured at fair value on a recurring basis and none of the Company’s non-financial assets and liabilities were recorded at fair value on a non-recurring basis. No transfers between levels have occurred for the periods presented. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents include cash in readily available checking and money market accounts. Restricted cash represents cash held as collateral for the Company’s facility lease and is reported as a long-term asset in the accompanying condensed consolidated balance sheets. Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institution in which those deposits are held. Additionally, the Company has established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity. Revenue Recognition The Company’s revenues are derived from Small Business Innovation Research (“SBIR”) grants from the National Institutes of Health. The Company recognizes SBIR grant revenue as reimbursable grant costs are incurred. The costs associated with these reimbursements are reflected as a component of research and development expense in the accompanying condensed consolidated statements of operations. Australian Research and Development Tax Incentive CAPL is eligible to obtain a cash refund from the Australian Taxation Office for eligible research and development expenditures under the Australian Research and Development Tax Incentive Program (the “Australian Tax Incentive”). The Australian Tax Incentive is recognized as a reduction to research and development expense when there is reasonable assurance that the Australian Tax Incentive will be received, the relevant expenditure has been incurred, and the amount can be reliably measured. The Company recognized reductions to research and development expense of $48,000 and $0.9 million, respectively, for the three and nine months ended September 30, 2018. The Company recognized a reduction to research and development expense of $0.2 million for each of the three and nine months ended September 30, 2017. Research and Development Expenses The Company’s research and development expenses consist primarily of salaries, payroll taxes, employee benefits and stock-based compensation charges for those individuals involved in research and development efforts, as well as consulting expenses, third-party research and development expenses, laboratory supplies, clinical materials and overhead, including facilities and depreciation costs, offset by the Australian Tax Incentive discussed above. Research and development expenses are charged to expense as incurred. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received. Stock-Based Compensation Stock-based compensation expense represents the cost of the grant date fair value of employee awards over the requisite service period of the awards (usually the vesting period) on a straight-line basis. For stock awards for which vesting is subject to performance-based milestones, the expense is recorded over the remaining service period after the point when the achievement of the milestone is probable, or the performance condition has been achieved. The Company accounts for awards to nonemployees using the fair value method. Awards to nonemployees are subject to periodic revaluation over their vesting terms. The Company estimates the fair value of all stock option grants using the Black-Scholes option pricing model and recognizes forfeitures as they occur. Comprehensive Loss Comprehensive loss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. There have been no items qualifying as other comprehensive loss and, therefore, for all periods presented, the Company’s comprehensive loss was the same as its reported net loss. Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period determined using the treasury-stock and if-converted methods. Dilutive common stock equivalents are comprised of convertible preferred stock, common stock subject to repurchase, and options outstanding under the Company’s stock option plan. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding as inclusion of the potentially dilutive securities would be antidilutive. Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases, which outlines a comprehensive lease accounting model and supersedes the current lease guidance. The new accounting standard requires lessees to recognize right-of-use assets and corresponding lease liabilities for all leases with lease terms of greater than twelve months. It also changes the definition of a lease and expands the disclosure requirements of lease arrangements. The new accounting standard will be adopted by the Company in the first quarter of 2019 and must be accounted for using the modified retrospective approach. The Company anticipates that the inclusion of lease-related assets and liabilities will have a material impact on its consolidated balance sheets but believes adoption of this guidance will not have a material impact on the consolidated statements of operations and comprehensive loss. In July 2018, the FASB issued ASU 2018-10, “Codification Improvements to Topic 842, Leases,” which affects narrow aspects of the guidance in ASU 2016-02, Leases (Topic 842). The amendments include sixteen narrow amendments to the Leases standard resulting from implementation activities, such as discussions between the FASB and stakeholders, technical inquiries, and routine Codification feedback. This ASU is intended to clarify the intended application of certain aspects of the new lease guidance and correct cross-reference inconsistencies. The new standard has the same effective date and transition requirements as ASU 2016-02. The Company is currently evaluating the impact of adoption of this new standard on its condensed consolidated financial statements. In July 2018, the FASB issued ASU 2018-11, “Leases (Topic 842): Targeted Improvements,” which provides entities with an additional (and optional) transition method to adopt the new leases standard. Under this new transition method, an entity initially applies the new leases standard at the adoption date and recognizes a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The new standard has the same effective date and transition requirements as ASU 2016-02. The Company is currently evaluating the impact of adoption of this new standard on its condensed consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting, which supersedes most of the prior accounting guidance on nonemployee share-based payments, and instead aligns it with existing guidance on employee share-based payments in Topic 718. As a result, nonemployee share-based payment transactions will be measured by estimating the fair value of the equity instruments that an entity is obligated to issue, and the measurement date will be consistent with the measurement date for employee share-based payment awards. Probability is to be considered on nonemployee awards with performance conditions. The classification will continue to be subject to the requirements of Topic 718, although cost recognition of nonemployee awards will remain unchanged. This guidance is effective for the fiscal years and interim reporting periods beginning after December 15, 2018 with early adoption permitted, but no earlier than an entity’s adoption date of Topic 606. The Company is in the process of determining the effects the adoption will have on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, “Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement,” which improves the effectiveness of the disclosures required under ASC 820 and modifies the disclosure requirements on fair value measurements, including the consideration of costs and benefits. The new standard is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. The Company is currently evaluating the impact of the pending adoption of this new standard on its condensed consolidated financial statements.

Balance Sheet Details

9 Months Ended

Sep. 30, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Details

3. BALANCE SHEET DETAILS

Prepaid expenses and other current assets consist of the following (in thousands):

	September 30, 2018		December 31, 2017
SBIR grant receivable	$	510	$	231
Australian tax incentive receivable		—		503
Prepaid expenses and other assets		877		239
Total	$	1,387	$	973

Property and equipment consist of the following (in thousands):

	September 30, 2018			December 31, 2017
Leasehold improvements	$	3,440		$	18
Laboratory equipment		894			640
Office equipment		510			19
Computers and software		41			27
Property and equipment at cost		4,885			704
Accumulated depreciation and amortization		(532	)		(304	)
Total	$	4,353		$	400

Other long-term assets consist of the following (in thousands):

	September 30, 2018		December 31, 2017
Long-term portion of Australian tax incentive receivable	$	777	$	—
Other		12		33
Total	$	789	$	33

Accrued expenses consist of the following (in thousands):

	September 30, 2018		December 31, 2017
Accrued research and development costs	$	2,382	$	126
Accrued compensation		1,573		315
Other accrued expenses		161		53
Total	$	4,116	$	494

Equity Incentive Plans

9 Months Ended

Sep. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Equity Incentive Plans

7. EQUITY INCENTIVE PLANS

2018 Incentive Award Plan

In July 2018, the Company adopted the 2018 Incentive Award Plan (the “2018 Plan”). Under the 2018 Plan, which expires in July 2028, the Company may grant equity-based awards to individuals who are employees, officers, directors or consultants of the Company. At adoption, a total of 1,991,636 shares of common stock were available for issuance under the 2018 Plan, which number includes the number of shares available for future issuance under the 2015 Plan as of the effective date of the 2018 Plan. In addition, the number of shares of common stock available for issuance under the 2018 Plan will automatically increase on the first day of each calendar year (beginning January 1, 2019) by an amount equal to (i) 5% of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year or (ii) such lesser amount as determined by the Company Board of Directors. Options issued under the 2018 Plan, will generally expire ten years from the date of grant and vest over a four-year period. As of September 30, 2018, 1,905,846 shares remained available for future issuance.

2015 Stock Incentive Plan

In February 2015, the Company adopted the Crinetics Pharmaceuticals, Inc. 2015 Stock Incentive Plan (the “2015 Plan”), which provided for the issuance of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock unit awards and other stock awards to its employees, members of its board of directors and consultants. In general, options issued under this plan vest over four years and expire after 10 years. Upon the adoption of the 2018 Plan, no additional equity awards can be made under the 2015 Plan.

Certain awards under the 2015 Plan allowed for exercise prior to vesting. Shares issued under such early-exercise provisions are subject to repurchase by the Company until they become fully vested. As of September 30, 2018, 133,041 unvested shares issued under early-exercise provisions were subject to repurchase by the Company. The condensed consolidated balance sheet reflects an unvested stock liability of $0.2 million as of September 30, 2018.

2018 Employee Stock Purchase Plan

In July 2018, the Company’s board of directors and stockholders approved and adopted the 2018 Employee Stock Purchase Plan (the “ESPP”). The ESPP became effective on the day prior to the effectiveness of the IPO. The ESPP permits participants to purchase common stock through payroll deductions of up to 20% of their eligible compensation. A total of 250,000 shares of common stock were approved to be initially reserved for issuance under the ESPP. In addition, the number of shares of common stock available for issuance under the ESPP will be automatically increased on the first day of each calendar year during the ten-year term of the ESPP, beginning with January 1, 2019, by an amount equal to (i) 1% of the outstanding number of shares of the Company’s common stock on December 31 of the preceding calendar year or (ii) such lesser amount determined by the Company.

Stock Options

A summary of the 2018 activity (and related information) under both of the 2015 Plan and the 2018 Plan follows:

				Weighted-		Weighted-		Aggregate
				Average		Average		Intrinsic
	Options			Exercise		Remaining		Value
	Outstanding			Price		Term		(000’s)
Balance at December 31, 2017		838,276		$	0.80
Granted		1,951,882		$	6.89
Exercised		(479,287	)	$	0.94
Forfeited and expired		(22,164	)	$	0.91
Balance at September 30, 2018		2,288,707		$	5.97		9.2	$	52,021
Exercisable at September 30, 2018		457,933		$	2.10		8.1	$	12,156

Fair Value of Stock Option Awards

The Company utilizes the Black-Scholes option pricing model to value awards under its option plans. The key assumptions used in the Black-Scholes option pricing model to determine the fair value of employee stock option grants, and the Company’s rationale, were as follows:

•

Expected term. The expected term represents the period that options are expected to be outstanding. As the Company does not have significant historical exercise behavior, it determines the expected life assumption using the simplified method, which is an average of the contractual option term and its vesting period.

•

Expected volatility. As the Company’s common stock does not have a significant trading history, the expected volatility assumption is based on volatilities of a peer group of similar companies in the biotechnology industry whose share prices are publicly available. The Company will continue to apply this process until sufficient historical information regarding the volatility of its own stock price is available.

•

Risk-free interest rate. The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant for zero coupon U.S. Treasury notes with maturities that approximate the expected terms of awards.

•

Expected dividend yield. The Company bases the expected dividend yield assumption on the fact that it has never paid cash dividends and has no present intention to pay cash dividends, and therefore, the Company used an expected dividend yield of zero.

The weighted average assumptions underlying the fair value calculations for stock option awards made during the first nine months of 2018 and 2017 included:

	2018	2017
Expected life of option	6.0 years	6.1 years
Volatility	69%	69%
Risk free interest rate	2.8%	1.9%
Dividend yield	—%	—%

The weighted-average fair value of stock options granted to employees during the first nine months of each of 2018 and 2017 was $4.39 and $0.64 per share, respectively.

Stock-Based Compensation Expense

Stock-based compensation expense recognized in the condensed consolidated statements of operations as follows (in thousands):

	Three months ended				Nine months ended
	September 30,				September 30,
	2018		2017		2018		2017
Included in research and development	$	373	$	30	$	663	$	91
Included in general and administrative		402		40		810		108
Total	$	775	$	70	$	1,473	$	199

Unrecognized stock-based compensation cost related to employee awards was $7.7 million as of September 30, 2018, which is expected to be recognized over a remaining weighted-average period of approximately 3.6 years.

Unrecognized stock-based compensation cost related to the ESPP was $0.5 million as of September 30, 2018, which is expected to be recognized over a remaining period of approximately 1.6 years.

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2018
Accounting Policies [Abstract]
Description of Business	Description of Business Crinetics Pharmaceuticals, Inc. (the “Company”) is a clinical stage pharmaceutical company incorporated in Delaware on November 18, 2008 and based in San Diego, California. The Company is focused on the discovery, development and commercialization of novel therapeutics for rare endocrine diseases and endocrine-related tumors. In January 2017, the Company established a wholly-owned Australian subsidiary, Crinetics Australia Pty Ltd (“CAPL”), in order to conduct various preclinical and clinical activities for its development candidates.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment.
Principles of Consolidation and Foreign Currency Transactions	Principles of Consolidation and Foreign Currency Transactions The condensed consolidated financial statements include the accounts of the Company and CAPL. All intercompany accounts and transactions have been eliminated in consolidation. The functional currency of both the Company and CAPL is the U.S. dollar. The Company’s assets and liabilities that are not denominated in the functional currency are remeasured into U.S. dollars at foreign currency exchange rates in effect at the balance sheet date except for nonmonetary assets, which are remeasured at historical foreign currency exchange rates in effect at the date of transaction. Net realized and unrealized gains and losses from foreign currency transactions and remeasurement are reported in other income (expense), in the condensed consolidated statements of operations and were not material for all periods presented.
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying interim condensed consolidated balance sheet as of September 30, 2018, the condensed consolidated statements of operations for the three and nine months ended September 30, 2018 and 2017, and the statements of cash flows for the nine months ended September 30, 2018 and 2017, and the related disclosures are unaudited. In management’s opinion, the unaudited interim financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of September 30, 2018 and the results of its operations and cash flows for the three and nine months ended September 30, 2018 and 2017 in accordance with U.S. GAAP. The results for the three and nine months ended September 30, 2018 are not necessarily indicative of the results expected for the full fiscal year or any other interim period.
Liquidity and Going Concern	Liquidity and Going Concern From inception, the Company has devoted substantially all of its efforts to drug discovery and development and conducting preclinical studies and clinical trials. The Company has a limited operating history and the sales and income potential of the Company’s business and market are unproven. Successful transition to attaining profitable operations is dependent upon achieving a level of revenues adequate to support the Company’s cost structure. As of September 30, 2018, the Company had $169.7 million in unrestricted cash and cash equivalents. The Company believes it has sufficient cash to meet its funding requirements for at least the next 12 months. However, the Company has experienced net losses and negative cash flows from operating activities since its inception and has an accumulated deficit of $34.9 million as of September 30, 2018. The Company expects to continue to incur net losses for the foreseeable future and believes it will need to raise substantial additional capital to accomplish its business plan over the next several years. The Company plans to continue to fund its losses from operations and capital funding needs through a combination of equity offerings, debt financings or other sources, including potentially collaborations, licenses and other similar arrangements. If the Company is not able to secure adequate additional funding, the Company may be forced to make reductions in spending, extend payment terms with suppliers, liquidate assets where possible, or suspend or curtail planned programs. Any of these actions could materially harm the Company’s business, results of operations and future prospects. There can be no assurance as to the availability or terms upon which such financing and capital might be available in the future.
Use of Estimates	Use of Estimates The Company’s condensed consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The preparation of the Company’s condensed consolidated financial statements requires it to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s condensed consolidated financial statements and accompanying notes. The most significant estimates in the Company’s condensed consolidated financial statements relate to revenue recognition, accrued amounts receivable under the Australian research and development tax incentive program, accrued expenses, and the assumptions underlying the determination of the fair value of equity awards for purposes of determining stock-based compensation. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.
Fair Value Measurements	Fair Value Measurements The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or non-recurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1: Observable inputs such as quoted prices in active markets. Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly. Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. The carrying amounts of the Company’s current financial assets, restricted cash and current financial liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments. As of each of September 30, 2018, and December 31, 2017, the Company had no financial assets measured at fair value on a recurring basis and none of the Company’s non-financial assets and liabilities were recorded at fair value on a non-recurring basis. No transfers between levels have occurred for the periods presented.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents include cash in readily available checking and money market accounts. Restricted cash represents cash held as collateral for the Company’s facility lease and is reported as a long-term asset in the accompanying condensed consolidated balance sheets.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institution in which those deposits are held. Additionally, the Company has established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity.
Revenue Recognition	Revenue Recognition The Company’s revenues are derived from Small Business Innovation Research (“SBIR”) grants from the National Institutes of Health. The Company recognizes SBIR grant revenue as reimbursable grant costs are incurred. The costs associated with these reimbursements are reflected as a component of research and development expense in the accompanying condensed consolidated statements of operations.
Australian Research and Development Tax Incentive	Australian Research and Development Tax Incentive CAPL is eligible to obtain a cash refund from the Australian Taxation Office for eligible research and development expenditures under the Australian Research and Development Tax Incentive Program (the “Australian Tax Incentive”). The Australian Tax Incentive is recognized as a reduction to research and development expense when there is reasonable assurance that the Australian Tax Incentive will be received, the relevant expenditure has been incurred, and the amount can be reliably measured. The Company recognized reductions to research and development expense of $48,000 and $0.9 million, respectively, for the three and nine months ended September 30, 2018. The Company recognized a reduction to research and development expense of $0.2 million for each of the three and nine months ended September 30, 2017.
Research and Development Expenses	Research and Development Expenses The Company’s research and development expenses consist primarily of salaries, payroll taxes, employee benefits and stock-based compensation charges for those individuals involved in research and development efforts, as well as consulting expenses, third-party research and development expenses, laboratory supplies, clinical materials and overhead, including facilities and depreciation costs, offset by the Australian Tax Incentive discussed above. Research and development expenses are charged to expense as incurred. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense represents the cost of the grant date fair value of employee awards over the requisite service period of the awards (usually the vesting period) on a straight-line basis. For stock awards for which vesting is subject to performance-based milestones, the expense is recorded over the remaining service period after the point when the achievement of the milestone is probable, or the performance condition has been achieved. The Company accounts for awards to nonemployees using the fair value method. Awards to nonemployees are subject to periodic revaluation over their vesting terms. The Company estimates the fair value of all stock option grants using the Black-Scholes option pricing model and recognizes forfeitures as they occur.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. There have been no items qualifying as other comprehensive loss and, therefore, for all periods presented, the Company’s comprehensive loss was the same as its reported net loss.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period determined using the treasury-stock and if-converted methods. Dilutive common stock equivalents are comprised of convertible preferred stock, common stock subject to repurchase, and options outstanding under the Company’s stock option plan. For all periods presented, there is no difference in the number of shares used to calculate basic and diluted shares outstanding as inclusion of the potentially dilutive securities would be antidilutive.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases, which outlines a comprehensive lease accounting model and supersedes the current lease guidance. The new accounting standard requires lessees to recognize right-of-use assets and corresponding lease liabilities for all leases with lease terms of greater than twelve months. It also changes the definition of a lease and expands the disclosure requirements of lease arrangements. The new accounting standard will be adopted by the Company in the first quarter of 2019 and must be accounted for using the modified retrospective approach. The Company anticipates that the inclusion of lease-related assets and liabilities will have a material impact on its consolidated balance sheets but believes adoption of this guidance will not have a material impact on the consolidated statements of operations and comprehensive loss. In July 2018, the FASB issued ASU 2018-10, “Codification Improvements to Topic 842, Leases,” which affects narrow aspects of the guidance in ASU 2016-02, Leases (Topic 842). The amendments include sixteen narrow amendments to the Leases standard resulting from implementation activities, such as discussions between the FASB and stakeholders, technical inquiries, and routine Codification feedback. This ASU is intended to clarify the intended application of certain aspects of the new lease guidance and correct cross-reference inconsistencies. The new standard has the same effective date and transition requirements as ASU 2016-02. The Company is currently evaluating the impact of adoption of this new standard on its condensed consolidated financial statements. In July 2018, the FASB issued ASU 2018-11, “Leases (Topic 842): Targeted Improvements,” which provides entities with an additional (and optional) transition method to adopt the new leases standard. Under this new transition method, an entity initially applies the new leases standard at the adoption date and recognizes a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. The new standard has the same effective date and transition requirements as ASU 2016-02. The Company is currently evaluating the impact of adoption of this new standard on its condensed consolidated financial statements. In June 2018, the FASB issued ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting, which supersedes most of the prior accounting guidance on nonemployee share-based payments, and instead aligns it with existing guidance on employee share-based payments in Topic 718. As a result, nonemployee share-based payment transactions will be measured by estimating the fair value of the equity instruments that an entity is obligated to issue, and the measurement date will be consistent with the measurement date for employee share-based payment awards. Probability is to be considered on nonemployee awards with performance conditions. The classification will continue to be subject to the requirements of Topic 718, although cost recognition of nonemployee awards will remain unchanged. This guidance is effective for the fiscal years and interim reporting periods beginning after December 15, 2018 with early adoption permitted, but no earlier than an entity’s adoption date of Topic 606. The Company is in the process of determining the effects the adoption will have on its consolidated financial statements. In August 2018, the FASB issued ASU 2018-13, “Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement,” which improves the effectiveness of the disclosures required under ASC 820 and modifies the disclosure requirements on fair value measurements, including the consideration of costs and benefits. The new standard is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years, and early adoption is permitted. The Company is currently evaluating the impact of the pending adoption of this new standard on its condensed consolidated financial statements.

Balance Sheet Details (Tables)

9 Months Ended

Sep. 30, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Components of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	September 30, 2018		December 31, 2017
SBIR grant receivable	$	510	$	231
Australian tax incentive receivable		—		503
Prepaid expenses and other assets		877		239
Total	$	1,387	$	973

Components of Property and Equipment

Property and equipment consist of the following (in thousands):

	September 30, 2018			December 31, 2017
Leasehold improvements	$	3,440		$	18
Laboratory equipment		894			640
Office equipment		510			19
Computers and software		41			27
Property and equipment at cost		4,885			704
Accumulated depreciation and amortization		(532	)		(304	)
Total	$	4,353		$	400

Components of Other Long-Term Assets

Other long-term assets consist of the following (in thousands):

	September 30, 2018		December 31, 2017
Long-term portion of Australian tax incentive receivable	$	777	$	—
Other		12		33
Total	$	789	$	33

Components of Accrued Expenses

Accrued expenses consist of the following (in thousands):

	September 30, 2018		December 31, 2017
Accrued research and development costs	$	2,382	$	126
Accrued compensation		1,573		315
Other accrued expenses		161		53
Total	$	4,116	$	494

Equity Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of 2018 Activity (and Related Information) under 2015 Plan and 2018 Plan

A summary of the 2018 activity (and related information) under both of the 2015 Plan and the 2018 Plan follows:

				Weighted-		Weighted-		Aggregate
				Average		Average		Intrinsic
	Options			Exercise		Remaining		Value
	Outstanding			Price		Term		(000’s)
Balance at December 31, 2017		838,276		$	0.80
Granted		1,951,882		$	6.89
Exercised		(479,287	)	$	0.94
Forfeited and expired		(22,164	)	$	0.91
Balance at September 30, 2018		2,288,707		$	5.97		9.2	$	52,021
Exercisable at September 30, 2018		457,933		$	2.10		8.1	$	12,156

Weighted Average Assumptions Underlying Fair Value Calculations for Stock Option Awards

The weighted average assumptions underlying the fair value calculations for stock option awards made during the first nine months of 2018 and 2017 included:

	2018	2017
Expected life of option	6.0 years	6.1 years
Volatility	69%	69%
Risk free interest rate	2.8%	1.9%
Dividend yield	—%	—%

Stock-based Compensation Expense Recognized

Stock-based compensation expense recognized in the condensed consolidated statements of operations as follows (in thousands):

	Three months ended				Nine months ended
	September 30,				September 30,
	2018		2017		2018		2017
Included in research and development	$	373	$	30	$	663	$	91
Included in general and administrative		402		40		810		108
Total	$	775	$	70	$	1,473	$	199

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Fair value assets transferred from level 1 to level 2	$ 0		$ 0		$ 0
Fair value assets transferred from level 2 to level 1	0		0		0
Fair value liabilities transferred from level 1 to level 2	0		0		0
Fair value liabilities transferred from level 2 to level 1	0		0		0
Fair value assets transferred into level 3			0		0
Fair value assets transferred out of level 3			0		0
Fair value liabilities transferred into level 3			0		0
Fair value liabilities transferred out of level 3			0		0
Australian Research and Development Tax Incentive \| Australian Taxation Office
Summary Of Significant Accounting Policies [Line Items]
Tax incentive receivable, reductions to research and development expense	48,000	$ 200,000	900,000	$ 200,000
Fair Value, Measurements, Recurring
Summary Of Significant Accounting Policies [Line Items]
Assets, fair value disclosure	0		0		0
Fair Value, Measurements, Nonrecurring
Summary Of Significant Accounting Policies [Line Items]
Assets, fair value disclosure	0		0		0
Liabilities, fair value disclosure	$ 0		$ 0		$ 0

Commitments and Contingencies - Schedule of Future Minimum Payments Under Non-cancellable Operating Leases (Details) $ in Thousands	Sep. 30, 2018 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2018 (3 months)	$ 166
2019	1,058
2020	1,123
2021	1,173
2022	1,208
Thereafter	3,395
Total	$ 8,123

Stockholders Equity - Additional Information (Details) - USD ($)		1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 20, 2018	Oct. 31, 2015	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Proceeds from IPO net of underwriting discounts and commissions and offering costs					$ 106,472,000
Common stock, shares authorized			200,000,000		200,000,000		50,500,000
Preferred stock, shares authorized			10,000,000		10,000,000		0
Stock-based compensation expenses					$ 1,473,000	$ 199,000
Stock Restriction Agreement
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrestricted shares of common stock repurchased		1,914,893
Common stock repurchase rights lapsed		765,957
Common stock repurchase rights to be lapsed monthly thereafter till fully vested in October 2019					23,936
Unrestricted shares of common stock fair value		$ 1,400,000
Stock-based compensation expenses			$ 0	$ 52,000	$ 400,000	$ 200,000
IPO
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Proceeds from IPO net of underwriting discounts and commissions and offering costs	$ 106,500,000
Common stock, shares authorized	200,000,000
Preferred stock, shares authorized	10,000,000
Common Stock \| IPO
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share of common stock issued	6,900,000
Sale of stock, price per share	$ 17.00

Equity Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		9 Months Ended
	Jul. 31, 2018	Feb. 28, 2015	Sep. 30, 2018	Sep. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividend yield			0.00%
Weighted-average fair value of stock options granted to employees per share			$ 4.39	$ 0.64
Unrecognized stock-based compensation cost			$ 7.7
Weighted-average period of unrecognized stock-based compensation cost expected to be recognized over remaining period			3 years 7 months 6 days
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan expiration term	10 years
Maximum percentage of eligible compensation to purchase common stock through payroll deductions	20.00%
Weighted-average period of unrecognized stock-based compensation cost expected to be recognized over remaining period			1 year 7 months 6 days
Unrecognized stock-based compensation cost			$ 0.5
2018 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan expiration period	2028-07
Plan expiration term	10 years
Vesting period	4 years
2015 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan expiration term		10 years
Vesting period		4 years
Shares issued under early-exercise provisions subject to repurchase			133,041
Unvested stock liability			$ 0.2
Common Stock \| ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance, authorized	250,000
Incremental percentage of shares authorized each year applied on outstanding number of shares	1.00%
Common Stock \| 2018 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved for issuance, authorized	1,991,636
Incremental percentage of shares authorized each year applied on outstanding number of shares	5.00%
Remaining shares available for future issuance			1,905,846

Equity Incentive Plans - Summary of 2018 Activity (and Related Information) under 2015 Plan and 2018 Plan (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options Outstanding, Beginning balance \| shares	838,276
Options Outstanding, Granted \| shares	1,951,882
Options Outstanding, Exercised \| shares	(479,287)
Options Outstanding, Forfeited and expired \| shares	(22,164)
Options Outstanding, Ending balance \| shares	2,288,707
Options Outstanding, Exercisable \| shares	457,933
Weighted-Average Exercise Price, Beginning balance \| $ / shares	$ 0.80
Weighted-Average Exercise Price, Granted \| $ / shares	6.89
Weighted Average Exercise Price, Exercised \| $ / shares	0.94
Weighted Average Exercise Price, Forfeited and expired \| $ / shares	0.91
Weighted-Average Exercise Price, Ending balance \| $ / shares	5.97
Weighted-Average Exercise Price, Exercisable \| $ / shares	$ 2.10
Weighted-Average Remaining Term, Ending balance	9 years 2 months 12 days
Weighted-Average Remaining Term, Exercisable	8 years 1 month 6 days
Aggregate Intrinsic Value, Ending balance \| $	$ 52,021
Aggregate Intrinsic Value, Exercisable \| $	$ 12,156

Convertible Preferred Stock	9 Months Ended
Convertible Preferred Stock	Sep. 30, 2018
Temporary Equity Disclosure [Abstract]
Convertible Preferred Stock	5. CONVERTIBLE PREFERRED STOCK In connection with the Company’s initial public offering, the outstanding shares of the Company’s Series A and Series B convertible preferred stock automatically converted into 14,712,571 shares of common stock (see Note 6). In February and March 2018, the Company issued an aggregate of 19,641,200 shares of its Series B convertible preferred stock for net proceeds of $63.3 million. The issuance costs incurred in connection with this offering were $0.2 million.

Stockholders Equity	9 Months Ended
Stockholders Equity	Sep. 30, 2018
Equity [Abstract]
Stockholders Equity	6. STOCKHOLDERS’ EQUITY Initial Public Offering On July 20, 2018, the Company completed its initial public offering (“IPO”) whereby it sold 6,900,000 shares of common stock at a price to the public of $17.00 per share. Proceeds from the IPO were approximately $106.5 million, net of underwriting discounts and commissions and offering costs. In addition, an amended and restated certificate of incorporation was filed by the Company on July 20, 2018, authorizing 200,000,000 shares of common stock and 10,000,000 shares of undesignated preferred stock. Shares of Common Stock Subject to Repurchase In October 2015, in connection with the issuance of the Company’s Series A convertible preferred stock, certain of the Company’s founders entered into stock restriction agreements, whereby 1,914,893 of previously unrestricted shares of common stock became subject to repurchase by the Company upon the stockholder’s termination of employment or service to the Company. The Company’s repurchase rights lapsed as to 765,957 shares of common stock in October 2015, with the remainder scheduled to lapse at the rate of 23,936 shares monthly thereafter such that the shares of common stock would have been fully vested in October 2019. Under the terms of the stock restriction agreements, the shares of common stock were also subject to accelerated vesting upon certain events, such that all of these restricted shares became fully vested upon the closing of the Company’s Series B preferred stock financing in February 2018 (see Note 5). The stock restriction agreements resulted in the deemed cancellation and reissuance of shares of common stock and therefore, for accounting purposes, the shares subject to repurchase were not considered to be outstanding until vested. The fair value of these shares of $1.4 million as of October 2015 was recognized as compensation expense over the vesting period. For the three months ended September 30, 2018 and 2017, the Company recognized stock-based compensation for these awards of zero and $52,000, respectively. For the nine months ended September 30, 2018 and 2017, the Company recognized stock-based compensation for these awards of $0.4 million and $0.2 million, respectively.

Organization and Basis of Presentation - Additional Information (Details) $ in Thousands		9 Months Ended
	Jul. 06, 2018	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Organization And Basis Of Presentation [Line Items]
Number of operating segments		1
Unrestricted cash and cash equivalents		$ 169,654	$ 14,192
Accumulated deficit		$ 34,900
Minimum
Organization And Basis Of Presentation [Line Items]
Period of sufficient cash to meet its funding requirements		12 months
Common Stock
Organization And Basis Of Presentation [Line Items]
Stock reverse stock split	1-for-3.29
Stock split conversion ratio	0.3040

Commitments and Contingencies - Additional Information (Details) - USD ($)	9 Months Ended
	Sep. 30, 2018	Mar. 31, 2018
2018 Operating Lease
Loss Contingencies [Line Items]
Operating lease, initial term		7 years
Operating lease, option to extend term	five years
Irrevocable letter of credit		$ 500,000
2013 Operating Lease
Loss Contingencies [Line Items]
Operating lease notice of termination period	2018-08
Payments for rent and common area costs	$ 0

Convertible Preferred Stock - Additional Information (Details) - USD ($) $ in Thousands		2 Months Ended	9 Months Ended
	Jul. 20, 2018	Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Temporary Equity [Line Items]
Proceeds from issuance of convertible preferred stock, net of issuance costs			$ 63,266	$ 4,722
Series B Convertible Preferred Stock
Temporary Equity [Line Items]
Convertible preferred stock, shares issued		19,641,200
Proceeds from issuance of convertible preferred stock, net of issuance costs		$ 63,300
Convertible preferred stock, issuance costs		$ 200
Initial Public Offering \| Series A and B Convertible Preferred Stock
Temporary Equity [Line Items]
Stock issued upon conversion of convertible securities	14,712,571

Balance Sheet Details - Components of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
SBIR grant receivable	$ 510	$ 231
Australian tax incentive receivable		503
Prepaid expenses and other assets	877	239
Total	$ 1,387	$ 973

Balance Sheet Details - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and equipment at cost	$ 4,885	$ 704
Accumulated depreciation and amortization	(532)	(304)
Total	4,353	400
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment at cost	3,440	18
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment at cost	894	640
Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment at cost	510	19
Computers and Software
Property Plant And Equipment [Line Items]
Property and equipment at cost	$ 41	$ 27

Balance Sheet Details - Components of Other Long-Term Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Assets Noncurrent [Abstract]
Long-term portion of Australian tax incentive receivable	$ 777
Other	12	$ 33
Total	$ 789	$ 33

Balance Sheet Details - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Accrued research and development costs	$ 2,382	$ 126
Accrued compensation	1,573	315
Other accrued expenses	161	53
Total	$ 4,116	$ 494