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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2017	Feb. 28, 2018	Sep. 28, 2017
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	FY
Trading Symbol	DCPH
Entity Registrant Name	DECIPHERA PHARMACEUTICALS, INC.
Entity Central Index Key	0001654151
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		32,594,128
Entity Public Float			$ 147.6

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 196,754	$ 57,461
Prepaid expenses and other current assets	1,428	791
Total current assets	198,182	58,252
Property and equipment, net	838	514
Deferred offering costs	0	104
Other assets	75	75
Total assets	199,095	58,945
Current liabilities:
Accounts payable	4,395	1,413
Accrued expenses	9,233	2,957
Notes payable to related party	187	187
Total current liabilities	13,815	4,557
Notes payable to related party, net of current portion	1,294	1,481
Other long-term liabilities	13
Total liabilities	15,122	6,038
Commitments and contingencies (Note 11)
Convertible preferred shares (Series A, B-1, B-2, C), no par value; no shares and 3,632,711 authorized as of December 31, 2017 and 2016, respectively; no shares and 3,632,711 shares issued and outstanding as of December 31, 2017 and 2016	0	192,667
Stockholders' Equity/Members' Deficit:
Preferred stock value
Additional paid-incapital	379,516	5,825
Accumulated deficit	(195,869)	(145,585)
Total stockholders' equity	183,973	(139,760)
Total members equity		(139,760)
Total liabilities, convertible preferred shares and stockholders' equity/members' deficit	199,095	$ 58,945
Par Value Common Stock [Member]
Stockholders' Equity/Members' Deficit:
Common stock value	$ 326

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Convertible preferred shares, shares authorized	0	3,632,711
Convertible preferred shares, no par value	$ 0	$ 0
Convertible preferred shares, shares issued	0	3,632,711
Convertible preferred shares, shares outstanding	0	3,632,711
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
No Par Value Common Stock [Member]
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	0	4,366,052
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0
Par Value Common Stock [Member]
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	125,000,000	0
Common stock, shares issued	32,591,686	0
Common stock, shares outstanding	32,591,686	0

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenue	$ 0	$ 0	$ 0
Operating expenses:
Research and development	39,514	20,163	12,475
General and administrative	11,421	5,675	5,135
Total operating expenses	50,935	25,838	17,610
Loss from operations	(50,935)	(25,838)	(17,610)
Other income (expense):
Interest expense	(95)	(106)	(2,209)
Interest and other income, net	746	4	3
Total other income (expense), net	651	(102)	(2,206)
Net loss and comprehensive loss	$ (50,284)	$ (25,940)	$ (19,816)
Net loss per share-basic and diluted	$ (2.99)	$ (2.23)	$ (4.67)
Weighted average common shares outstanding-basic and diluted	16,792,179	11,626,287	4,245,698

Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
No Par Value Common Stock [Member]
Common stock, shares outstanding	0	0	0

Consolidated Statements of Convertible Preferred Shares and Stockholders' Equity/Members' Deficit - USD ($) $ in Thousands	Total	Member Units [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Series A Convertible Preferred Stock [Member]	Series A Convertible Preferred Stock [Member] Member Units [Member]	Series A Convertible Preferred Stock [Member] Common Stock [Member]	Series A Convertible Preferred Stock [Member] Additional Paid-in Capital [Member]	Series A Convertible Preferred Stock [Member] Accumulated Deficit [Member]	Series B-1 Convertible Preferred Stock [Member]	Series B-2 Convertible Preferred Stock [Member]	Series C Convertible Preferred Shares [Member]
Beginning balance at Dec. 31, 2014	$ (99,535)		$ 0	$ 294	$ (99,829)
Beginning balance, shares at Dec. 31, 2014			0
Conversion of member units into Series A convertible preferred shares						$ 0
Conversion of member units into Series A convertible preferred shares, shares						0		0	0	0
Gain on extinguishment of notes payable to related party	1,487			1,487
Share-based compensation expense	2,557			2,557
Net loss	(19,816)				(19,816)
Ending balance at Dec. 31, 2015	(115,307)		$ 0	4,338	(119,645)
Ending balance, shares at Dec. 31, 2015			0
Convertible preferred shares, beginning balance at Dec. 31, 2014	$ 0	$ 8,491
Convertible preferred shares, beginning balance, shares at Dec. 31, 2014	0	202,500
Conversion of member units into Series A convertible preferred shares						$ 8,491	$ (8,491)
Conversion of member units into Series A convertible preferred shares, shares						202,500	(202,500)
Conversion of notes payable and accrued interest into convertible preferred shares, net of issuance costs						$ 94,065					$ 3,728
Conversion of notes payable and accrued interest into convertible preferred shares, shares						1,855,250					73,811
Issuance of convertible preferred shares, net of issuance costs											$ 31,084
Issuance of convertible preferred shares, shares											624,784
Convertible preferred shares, ending balance at Dec. 31, 2015	$ 137,368
Convertible preferred shares, ending balance, shares at Dec. 31, 2015	2,756,345					202,500
Share-based compensation expense	$ 1,487			1,487
Net loss	(25,940)				(25,940)
Ending balance at Dec. 31, 2016	(139,760)		$ 0	5,825	(145,585)
Ending balance, shares at Dec. 31, 2016			0
Issuance of convertible preferred shares, net of issuance costs												$ 55,299
Issuance of convertible preferred shares, shares												876,366
Convertible preferred shares, ending balance at Dec. 31, 2016	$ 192,667					$ 102,556					$ 34,812	$ 55,299
Convertible preferred shares, ending balance, shares at Dec. 31, 2016	3,632,711					2,057,750					698,595	876,366
Effect of Conversion (Note 1)	$ 244,538		$ 244	244,294
Effect of Conversion (Note 1), convertible preferred shares	$ (244,538)
Effect of Conversion (Note 1), shares			24,425,190
Effect of Conversion (Note 1), shares, Convertible preferred shares, shares	(4,323,044)
Issuance of common stock sold in initial public offering, net of underwriting discounts, commissions and offering costs	$ 124,613		$ 82	124,531
Issuance of common stock sold in initial public offering, net of underwriting discounts, commissions and offering costs, shares			8,166,496
Share-based compensation expense	4,866			4,866
Net loss	(50,284)				(50,284)
Ending balance at Dec. 31, 2017	183,973		$ 326	$ 379,516	$ (195,869)
Ending balance, shares at Dec. 31, 2017			32,591,686
Issuance of convertible preferred shares, net of issuance costs													$ 51,871
Issuance of convertible preferred shares, shares													690,333
Convertible preferred shares, ending balance at Dec. 31, 2017	$ 0	$ 0
Convertible preferred shares, ending balance, shares at Dec. 31, 2017	0

Consolidated Statements of Convertible Preferred Shares and Stockholders' Equity/Members' Deficit (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Series A Convertible Preferred Stock [Member]
Issuance costs			$ 30
Series B-1 Convertible Preferred Stock [Member]
Issuance costs			$ 468
Series B-2 Convertible Preferred Stock [Member]
Issuance costs		$ 25
Series C Convertible Preferred Shares [Member]
Issuance costs	$ 429

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net loss	$ (50,284)	$ (25,940)	$ (19,816)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	4,866	1,487	2,557
Depreciation and amortization expense	150	90	73
Non-cash interest expense			2,091
Loss on disposal of property and equipment	10	6
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(637)	(185)	(516)
Accounts payable	2,904	(187)	1,176
Accrued expenses	6,276	1,694	1,160
Other assets		(55)	6
Other long-term liabilities	13
Net cash used in operating activities	(36,702)	(23,090)	(13,269)
Cash flows from investing activities:
Purchases of property and equipment	(406)	(223)	(142)
Net cash used in investing activities	(406)	(223)	(142)
Cash flows from financing activities:
Proceeds from initial public offering, net of underwriting discounts and commissions	129,112
Payments of initial public offering costs	(4,395)	(104)
Proceeds from issuance of convertible preferred shares	52,300	55,324	31,552
Proceeds from issuance of convertible notes payable to related parties			7,550
Repayment of notes payable to related party	(187)	(198)	(186)
Payments of convertible preferred share issuance costs	(429)	(25)	(498)
Net cash provided by financing activities	176,401	54,997	38,418
Net increase in cash and cash equivalents	139,293	31,684	25,007
Cash and cash equivalents at beginning of period	57,461	25,777	770
Cash and cash equivalents at end of period	196,754	57,461	25,777
Cash paid for interest	95	$ 106	117
Conversion of convertible preferred shares into common stock	244,538
Conversion of notes payable and accrued interest into convertible preferred shares			97,793
Conversion of member units into Series A convertible preferred shares			8,491
Gain on extinguishment of notes payable to related party			$ 1,487
Purchases of property and equipment included in accounts payable or accrued expenses	$ 78

Nature of the Business and Basis of Presentation

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Nature of the Business and Basis of Presentation

1.	Nature of the Business and Basis of Presentation

Deciphera Pharmaceuticals, Inc. (the “Company”) is a clinical-stage biopharmaceutical company developing new drugs to improve the lives of cancer patients by addressing key mechanisms of drug resistance that limit the rate and durability of response of many cancer therapies. The Company’s targeted, small molecule drug candidates, designed using its proprietary kinase switch control inhibitor platform, inhibit the activation of kinases, an important family of enzymes, that, when mutated or over expressed, are known to be directly involved in the growth and spread of many cancers.

On October 2, 2017, immediately prior to the completion of its initial public offering (“IPO”), the Company engaged in a series of transactions whereby Deciphera Pharmaceuticals, LLC became a wholly owned subsidiary of Deciphera Pharmaceuticals, Inc., a Delaware corporation. As part of the transactions, shareholders of Deciphera Pharmaceuticals, LLC exchanged their shares of Deciphera Pharmaceuticals, LLC for shares of Deciphera Pharmaceuticals, Inc. on a one-for-5.65 basis, (the “Conversion”).

On October 2, 2017, Deciphera Pharmaceuticals, Inc., completed the IPO, pursuant to which it issued and sold 7,500,000 shares of common stock at the IPO price of $17.00 per share, resulting in net proceeds of $114.1 million after deducting underwriting discounts and commissions and other offering expenses. On October 4, 2017, the Company issued and sold an additional 666,496 shares of common stock at the IPO price of $17.00 per share pursuant to the underwriters’ partial exercise of their option to purchase additional shares of common stock, resulting in additional net proceeds of $10.5 million after deducting underwriting discounts and commissions. Upon the closing of the IPO, the Company’s outstanding convertible preferred shares automatically converted into shares of common stock.

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Drug candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

The accompanying consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. Since inception, the Company has incurred recurring losses including net losses of $50.3 million and $25.9 million for the years ended December 31, 2017 and 2016, respectively. As of December 31, 2017 the Company had an accumulated deficit of $195.9 million. The Company expects to continue to generate operating losses in the foreseeable future. As of the issuance date of the consolidated financial statements, the Company expects that its cash and cash equivalents of $196.8 million as of December 31, 2017 would be sufficient to fund its operating expenses, capital expenditure requirements and debt service payments through at least 12 months from the issuance date of these consolidated financial statements. The future viability of the Company is dependent on its ability to raise additional capital to fund its operations.

The Company expects its expenses to increase substantially in connection with ongoing activities, particularly as the Company advances its preclinical activities and clinical trials for its drug candidates in development. Accordingly, the Company will need to obtain substantial additional funding in connection with continuing operations. If the Company is unable to raise capital when needed, or on attractive terms, it could be forced to delay, reduce or eliminate its research or drug development programs or any future commercialization efforts. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all.

The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated.

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”).

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of Significant Accounting Policies

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual for research and development expenses, prior to the Company’s IPO, the valuation of common stock, and the valuation of stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.

Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents.

Concentrations of Credit Risk and of Significant Suppliers

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains all cash and cash equivalents at one accredited financial institution. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs.

Deferred Offering Costs

The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ equity/members’ deficit as a reduction of additional paid-in capital generated as a result of the offering. Should the planned equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the statement of operations and comprehensive loss. As of December 31, 2016, the Company recorded $0.1 million of deferred offering costs in contemplation of the Company’s IPO, which closed in October 2017, and such costs were transferred to additional paid-in capital upon completion of the IPO. The Company has no deferred offering costs as of December 31, 2017.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows:


		Estimated Useful Life
Lab equipment		5 to 7 years
Computer equipment		3 to 5 years
Furniture and fixtures		7 years
Leasehold improvements		Shorter of life of lease or 15 years

Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation and amortization are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value, determined based on discounted cash flows. The Company did not record any impairment losses on long-lived assets during the years ended December 31, 2017, 2016 or 2015.

Fair Value Measurements

Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

•

Level 1—Quoted prices in active markets for identical assets or liabilities.

•

Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

•

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

The Company’s cash equivalents are carried at fair value, determined according to the fair value hierarchy described above (see Note 3). The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities. The fair value of the Company’s outstanding notes payable to related party (see Note 6) as of December 31, 2017 and 2016 approximated $1.2 million and $1.3 million, respectively. The fair value of the outstanding debt was estimated using a discounted cash flow analysis based on current market interest rates for debt issuances with similar remaining years to maturity, adjusted for credit risk, which represents a Level 3 measurement.

Segment Information

The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is designing, optimizing and introducing small molecule switch control inhibitors of protein kinases for human clinical trials and the global pharmaceutical marketplace through the use of its proprietary drug discovery technology platform. All of the Company’s tangible assets are held in the United States.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries, stock-based compensation and benefits, facilities costs, depreciation, manufacturing expenses and external costs of outside vendors engaged to conduct preclinical development activities and trials.

Advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. The prepaid amounts are expensed as the related goods are delivered or the services are performed.

Research Contract Costs and Accruals

The Company has entered into various research and development contracts with research institutions and other companies both inside and outside of the United States. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Stock-Based Compensation

The Company measures all stock options and other stock-based awards granted to employees and directors based on the fair value on the date of the grant and recognizes compensation expense of those awards over the requisite service period, which is generally the vesting period of the respective award. The straight-line method of expense recognition is applied to all awards with service-only conditions while the graded-vesting method is applied to all awards with both service and performance conditions. The Company accounts for forfeitures as they occur.

The Company classifies stock-based compensation expense in its statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

Income Taxes

Upon consummation of the Conversion on October 2, 2017, the Company became subject to corporate U.S. federal and state income taxes. Prior to the Conversion, the Company was treated as a partnership for income tax purposes and was not subject to U.S. federal or state income taxation. As a result, the Company had not recorded any U.S. federal or state income tax benefits prior to October 2, 2017 for the net losses incurred in each reporting period or for any earned research and orphan drug credits as the operating losses incurred by the Company had been passed through to its members.

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in its consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than- not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity/members’ deficit that result from transactions and economic events other than those with shareholders. There was no difference between net loss and comprehensive loss for each of the periods presented in the accompanying consolidated financial statements.

Net Loss per Share

Basic net income (loss) per share is computed by dividing the net income (loss) by the weighted average number of common shares outstanding for the year ended December 31, 2017. Diluted net income (loss) per is computed by dividing the diluted net income (loss) by the weighted average number of common shares, including potential dilutive common shares assuming the dilutive effect of outstanding stock options and unvested restricted common shares, as determined using the treasury stock method. For periods in which the Company has reported net losses, diluted net loss per common share is the same as basic net loss per common share, since dilutive common shares are not assumed to have been issued if their effect is antidilutive.

The Company did not have any common shares outstanding during the years ended December 31, 2015 and 2016 or for the period from January 1, 2017 through the closing of its initial public offering on October 2, 2017. To determine the weighted average shares outstanding for purpose of calculating net loss per share during those periods, the Company used the weighted average number of Series A convertible preferred shares outstanding because such shares represented the most subordinate share class outstanding during those periods, and such shares were retrospectively adjusted to give effect to the exchange of Series A convertible preferred shares into shares of common stock upon the Conversion (see Note 1).

Recently Issued Accounting Pronouncements

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes existing revenue recognition guidance under GAAP. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The standard defines a five-step process to achieve this principle, and will require companies to use more judgment and make more estimates than under the current guidance. The Company expects that these judgments and estimates will include identifying performance obligations in the customer contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. In August 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delays the effective date of ASU 2014-09 such that the standard is effective for public entities for annual periods beginning after December 15, 2017 and for interim periods within those fiscal years. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (“ASU 2016-08”), which further clarifies the implementation guidance on principal versus agent considerations in ASU 2014-09. In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing, clarifying the implementation guidance on identifying performance obligations and licensing. Specifically, the amendments in this update reduce the cost and complexity of identifying promised goods or services and improve the guidance for determining whether promises are separately identifiable. The amendments in this update also provide implementation guidance on determining whether an entity’s promise to grant a license provides a customer with either a right to use the entity’s intellectual property (which is satisfied at a point in time) or a right to access the entity’s intellectual property (which is satisfied over time). In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”), which clarifies the objective of the collectability criterion, presentation of taxes collected from customers, non-cash consideration, contract modifications at transition, completed contracts at transition and how guidance in ASU 2014-09 is retrospectively applied. ASU 2016-08, ASU 2016-10 and ASU 2016-12 have the same effective dates and transition requirements as ASU 2014-09. The adoption of these standards is not expected to have an impact on the Company’s financial position, results of operations or cash flows as the Company does not currently have any revenue-generating arrangements.

In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASU 2016-02”). ASU 2016-02 will require lessees to recognize most leases on their balance sheet as a right-of-use asset and a lease liability. Leases will be classified as either operating or finance, and classification will be based on criteria similar to current lease accounting, but without explicit bright lines. The guidance is effective for annual reporting periods beginning after December 15, 2018 and interim periods within those fiscal years, and early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2016-02 will have on its financial position, results of operations or cash flows.

In May 2017, the FASB issued ASU No. 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting (“ASU 2017-09”), which clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The standard is effective for annual periods beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2017-09 will have on its consolidated financial statements. The Company does not expect that the adoption of ASU 2017-09 will have a material impact on its financial position, results of operations or cash flows.

Fair Value of Financial Assets

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Fair Value of Financial Assets

3.	Fair Value of Financial Assets

The following tables present information about the Company’s financial assets measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands):


	Fair Value Measurements at December 31, 2017 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	191,950	$	—	$	191,950

Total	$	—	$	191,950	$	—	$	191,950


	Fair Value Measurements at December 31, 2016 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	53,180	$	—	$	53,180

Total	$	—	$	53,180	$	—	$	53,180

During the years ended December 31, 2017 and 2016, there were no transfers between Level 1, Level 2 and Level 3.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Property and Equipment, Net

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

4.	Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2017			2016
Laboratory equipment	$	981		$	602
Leasehold improvements		344			349
Computer equipment		300			225
Furniture and fixtures		128			104

		1,753			1,280
Less: Accumulated depreciation and amortization		(915	)		(766	)

	$	838		$	514

Depreciation and amortization expense was $0.2 million for the year ended December 31, 2017 and $0.1 million for each of the years ended December 31, 2016 and 2015, respectively.

Accrued Expenses

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Accrued Expenses

5.	Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	December 31,
	2017		2016
Accrued external research and development expenses	$	6,625	$	1,433
Accrued payroll and related expenses		2,233		1,267
Accrued professional fees		353		240
Accrued other		22		17

	$	9,233	$	2,957

Notes Payable to Related Parties

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Notes Payable to Related Parties

6.	Notes Payable to Related Parties

2004 Convertible Loan Agreement

In 2004, the Company entered into a convertible loan agreement (the “2004 Loan”) with Brightstar Associates, LLC (“Brightstar”), a related party (see Note 14). In May 2015, the 2004 Loan was amended to (i) consolidate the then-current accrued interest of $5.0 million and outstanding principal for a new principal balance of $12.6 million, (ii) extend the maturity date to be due on demand after December 31, 2019 and (iii) allow Brightstar, at its option, to convert the outstanding principal and accrued interest into member units of the Company at a price of $51.52 per member unit, subject to appropriate adjustment in the event of the issuance of any member units or securities convertible into member units at a lower price per member unit than $51.52. The Company determined that such amendments should be accounted for as an extinguishment of the 2004 Loan for accounting purposes. As a result, the carrying value of the 2004 Loan of $12.6 million at the time of the extinguishment was removed from the balance sheet and was recorded at its then-current fair value of $11.1 million. The resulting gain on extinguishment of $1.5 million was recognized as additional paid-in capital, a component of members’ deficit, due to the related party nature of the 2004 Loan. At the date of extinguishment, there were no unamortized debt discounts or debt issuance costs.

The Company assessed the embedded conversion and repayment features of the 2004 Loan and determined that there were no features that were required to be separated and accounted for as derivatives.

2006 through 2013 Convertible Loan Agreements

From September 2006 through June 2013, the Company entered into five convertible loan agreements (the “Pre-2015 Convertible Loans”) with Brightstar and Biochenomix, L.L.C. (“Biochenomix”), which provided for aggregate borrowings of up to $70.1 million. Through December 31, 2014, the Company drew down $66.2 million under the Pre-2015 Convertible Loans, and in 2015, the remaining $3.9 million was drawn down. Interest under the Pre-2015 Convertible Loans accrued monthly at the prime rate.

The Company assessed the embedded conversion and repayment features of the Pre-2015 Convertible Loans and determined that there were no features that were required to be separated and accounted for as derivatives.

Conversion of 2004 Loan and Pre-2015 Convertible Loans

In September 2015, all outstanding principal and accrued interest of $95.6 million, with a carrying value of $94.1 million, due under the 2004 Loan and the Pre-2015 Convertible Loans was converted into 1,855,250 Series A convertible preferred shares (see Note 7).

2015 Convertible Loan Agreement

In May 2015, the Company entered into a seventh convertible loan agreement (the “2015 Loan”) with Brightstar and Biochenomix, which provided for aggregate borrowings of up to $15.0 million. Interest under the 2015 Loan accrued monthly at the prime rate. In May 2015 and July 2015, the Company drew down $2.0 million and $1.7 million, respectively, under the 2015 Loan.

The Company assessed the embedded conversion and repayment features of the 2015 Loan and determined that there were no features that were required to be separated and accounted for as derivatives.

In September 2015, all outstanding principal and accrued interest of $3.7 million due under the 2015 Loan was converted into 73,811 Series B-1 convertible preferred shares (see Note 7).

2010 Construction Loan Agreement

In June 2010, the Company entered into a loan agreement and a security agreement (together, the “CRL Construction Loan”) with Clinical Reference Laboratory, Inc. (“CRL”), a related party (see Note 14), which provided for aggregate borrowings of up to $2.8 million to finance construction of the Company’s biology and chemistry laboratories. Borrowings under the CRL Construction Loan bear interest at a fixed rate equal to 6.0% per annum and interest accrues monthly. The CRL Construction Loan requires monthly payments of principal and interest commencing on January 1, 2011 and through the maturity date of January 1, 2026, based on a 15-year straight-line amortization schedule.

The CRL Construction Loan is collateralized by a security interest in all of the equipment and fixtures at the Company’s laboratories in Lawrence, Kansas. Under the loan and security agreements, the Company has agreed to affirmative, negative and financial covenants to which it will remain subject until the loan has been paid off in full. These covenants include limitations on the Company’s ability to incur additional indebtedness and engage in certain fundamental business transactions, such as mergers or acquisitions of other businesses, as well as requirements that the Company comply with a maximum liabilities-to-assets ratio, a minimum working capital threshold and a maximum debt-to-equity ratio. Events of default under the loan agreement include failure to make payments when due, insolvency events, failure to comply with covenants and material adverse effects with respect to the Company. The lender’s remedies upon an event of default include the ability to accelerate all amounts that are due under the CRL Construction Loan to become immediately due and payable. As of December 31, 2017 and 2016, the Company was in compliance with the financial covenants of the CRL Construction Loan.

Notes payable to related party as of December 31, 2017 and 2016 consisted only of outstanding borrowings under the CRL Construction Loan, as follows (in thousands):


	December 31,
	2017			2016
Notes payable to related party	$	1,481		$	1,668
Less: Current portion		(187	)		(187	)

Notes payable to related party, net of current portion	$	1,294		$	1,481

As of December 31, 2017, scheduled payments of principal and interest for the CRL Construction Loan are as follows (in thousands):


Year ending December 31,	Principal		Interest		Total
2018	$	187	$	84	$	271
2019		187		73		260
2020		187		61		248
2021		187		50		237
2022		187		39		226
Thereafter		546		49		595

	$	1,481	$	356	$	1,837

Total interest expense for each of the years ended December 31, 2017, 2016 and 2015 was $0.1 million, $0.1 million and $2.2 million, respectively.

Convertible Preferred Shares

12 Months Ended

Dec. 31, 2017

Text Block [Abstract]

Convertible Preferred Shares

7.	Convertible Preferred Shares

2015 Recapitalization

During 2015, the Company amended its operating agreement to affect a recapitalization of its members’ interests into three classes of shares: common shares, Series A Shares and Series B Shares. As a result of this recapitalization, the previously outstanding member units became 202,500 Series A Shares.

Series B Preferred Shares Purchase Agreement

In September 2015, the Company entered into a Series B preferred shares purchase agreement, which provided for total gross cash proceeds of up to $90.6 million, comprised of two tranches: a Series B-1 Share financing for total gross proceeds of $31.6 million (the “Series B-1 Share Financing”) and a Series B-2 Share financing for total gross cash proceeds of $55.3 million (the “Series B-2 Share Financing”).

In connection with the Series B preferred shares purchase agreement, in September 2015, the Company amended its operating agreement such that each member of the LLC would convert debt held by such member issued prior to January 1, 2015 into Series A Shares at their applicable conversion prices and that each member of the LLC would convert debt held by such member issued after January 1, 2015 into Series B-1 Shares at their applicable conversion prices. At that time, an aggregate of $95.6 million of outstanding principal and interest under the Company’s 2004 Loan and the Pre-2015 Convertible Loans, with a carrying value of $94.1 million, was converted into 1,855,250 Series A Shares. Additionally, $3.7 million of outstanding principal and accrued interest under the Company’s 2015 Loan was converted into 73,811 Series B-1 Shares.

In connection with the Series B-1 Share Financing, in September 2015 and December 2015, the Company sold an aggregate of 624,784 Series B-1 Shares at a price of $50.50 per share for gross proceeds of $31.6 million. The Company recorded issuance costs of $0.5 million in connection with the sale and issuance of the Series B-1 Shares. Purchasers of Series B-1 Shares also agreed to purchase an aggregate of 876,366 Series B-2 Shares at a price of $63.13 per share upon the achievement by the Company of one of two clinical development milestones and the certification by the Company’s board of directors that the milestone(s) had occurred. In addition, the purchasers of Series B-1 Shares were granted the right to purchase their respective allocation of Series B-2 Shares at any time more than 45 days from the initial closing and before the Company completed its next financing of more than $5.0 million. In July 2016, upon notice from the Company of the achievement of one of the required clinical milestones, the Company issued and sold 876,366 Series B-2 Shares at a price of $63.13 per share for gross proceeds of $55.3 million. Issuance costs associated with the issuance of Series B-2 Shares were less than $0.1 million. The Company determined that the future tranche obligation of the Series B preferred shares purchase agreement did not meet the definition of a freestanding financial instrument because, while separately exercisable, it was not legally detachable. Further, the Company determined that the embedded future tranche obligation did not require bifurcation for accounting purposes as it is clearly and closely related to the economic characteristics and risks of the initial preferred shares and would not meet the definition of a derivative on a standalone basis.

Series C Preferred Shares Purchase Agreement

In May 2017, the Company entered into a Series C preferred shares purchase agreement, pursuant to which the Company sold 690,333 Series C Shares at a price of $75.76 per share for proceeds of $51.9 million, net of issuance costs of $0.4 million.

Upon issuance of each class of Preferred Shares, the Company assessed the embedded conversion and liquidation features of the securities and determined that such features did not require the Company to separately account for these features. The Company also concluded that no beneficial conversion feature existed upon the issuance date of each class of Preferred Shares.

As of December 31, 2016, the Preferred Shares consisted of the following (in thousands, except share amounts):


	Preferred Shares Authorized		Preferred Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion⁽¹⁾
Series A Shares		2,057,750		2,057,750	$	102,556	$	103,484		11,626,287
Series B-1 Shares		698,595		698,595		34,812		35,279		3,947,060
Series B-2 Shares		876,366		876,366		55,299		55,325		4,951,467

		3,632,711		3,632,711	$	192,667	$	194,088		20,524,814

(1)	Amounts reflect the exchange of convertible preferred shares into shares of common stock on a one-for 5.65 basis upon the Conversion described in Note 1.

Upon closing of the IPO in October 2017, all of the outstanding Preferred Shares including the Series C issued in May 2017 were converted into 24,425,190 shares of common stock.

Conversion

On October 2, 2017, immediately prior to the completion of the IPO, the Company engaged in a series of transactions whereby Deciphera Pharmaceuticals, LLC became a wholly owned subsidiary of Deciphera Pharmaceuticals, Inc. As part of the transactions, shareholders of Deciphera Pharmaceuticals, LLC exchanged their shares of Deciphera Pharmaceuticals, LLC for shares of Deciphera Pharmaceuticals, Inc. on a one-for-5.65 basis and exchanged their outstanding equity incentive awards of Deciphera Pharmaceuticals, LLC for options to purchase the same number of shares of common stock of Deciphera Pharmaceuticals, Inc. multiplied by 5.65, with a corresponding adjustment to divide the exercise price by 5.65 (the “Conversion”). The Conversion included the exchange of all outstanding series A, series B and series C preferred shares of Deciphera Pharmaceuticals, LLC for an aggregate of 24,425,190 shares of common stock of Deciphera Pharmaceuticals, Inc. and the exchange of all outstanding options and share appreciations rights of Deciphera Pharmaceuticals, LLC for 4,092,710 options to purchase common stock of Deciphera Pharmaceuticals, Inc. with a weighted average exercise price of $3.37 per share.

Prior to the Conversion, the holders of the Preferred Shares had the following rights and preferences:

Voting Rights

The holders of Preferred Shares were entitled to vote, together with the holders of common shares, on all matters submitted to shareholders for a vote. Each preferred shareholder was entitled to the number of votes equal to the number of common shares into which each Preferred Share was convertible at the time of such vote.

Dividends and Distributions

There were no stated dividends on the Preferred Shares, however, holders of Preferred Shares were entitled to receive distributions when, as and if approved by the board of directors of the Company and together with holders of common shares in proportion to the number of common shares into which each Preferred Share was convertible at the time of such distribution. Additionally, to the extent the Company had sufficient cash available, without incurring any borrowings, the Company should make a tax distribution in an amount of cash equal to the excess, if any, of (i) the product of the net taxable income or gain of the Company for the year allocated to each member and the highest combined marginal federal, state and local income tax rate applicable to residents in Kansas over (ii) the aggregate amount of distributions previously made to such member during such taxable year.

Through December 31, 2017, no distributions had been approved or paid.

Liquidation

In the event of any liquidation, dissolution or winding-up of the Company or Liquidating Event (as described below), the holders of Preferred Shares were entitled to be paid out of the assets of the Company available for distribution to shareholders in the order and preference as specified in the Company’s certificate of incorporation, as amended and restated.

Unless the holders of a majority of the outstanding Preferred Shares, voting together as a single class, elect otherwise, a Liquidating Event should include a merger or consolidation (other than one in which shareholders of the Company own a majority of the voting power of the outstanding shares of the surviving or acquiring corporation) or a sale, lease, transfer, exclusive license or other disposition of all or substantially all of the assets of the Company.

Conversion

Each Preferred Share was convertible at the option of the shareholder at any time after the date of issuance, and automatically converted into shares of common stock upon the closing of the Company’s IPO in October 2017 on a one-for-5.65 basis.

Common Stock

12 Months Ended

Dec. 31, 2017

Equity [Abstract]

Common Stock

8.	Common Stock

On October 2, 2017, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue up to 125,000,000 shares of common stock and 5,000,000 shares of preferred stock, each with a par value of $0.01 per share.

As of December 31, 2016, the Company’s operating agreement, as amended and restated, authorized the Company to issue 4,366,052 shares of no par value common shares. Common shares shall be issued in one or more series as determined by the board of directors of the Company at the time of issuance. Each common share entitled the holder to one vote on all matters submitted to a vote of the Company’s shareholders.

Stock-Based Compensation

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

9.	Stock-Based Compensation

2017 Equity Incentive Plan

On September 21, 2017, the Company adopted the 2017 Stock Option and Incentive Plan (the “2017 Plan”) which became effective on September 26, 2017. The 2017 Plan provides for the grant of equity-based incentive awards. The Company initially reserved 2,655,831 shares of common stock for the issuance of awards under the 2017 Plan. The 2017 Plan provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning on January 1, 2018, by 4% of the outstanding number of shares of our common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Compensation Committee of the Company’s Board of Directors. As of December 31, 2017, 2,150,189 remained available for issuance under the 2017 Plan. The number of shares reserved for issuance under the 2017 Plan was increased by 1,303,667 shares effective January 1, 2018.

2017 Employee Stock Purchase Plan

On September 21, 2017, the Company adopted the 2017 Employee Stock Purchase Plan, (the “ESPP”) which became effective on September 26, 2017. The ESPP initially reserves and authorizes the issuance of up to a total of 306,750 shares of common stock to participating employees. The ESPP provides that the number of shares reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2018 and each January 1 thereafter through January 1, 2027, by the least of (i) 1% of the outstanding number of shares of common stock on the immediately preceding December 31; (ii) 400,000 shares or (iii) such number of shares as determined by the ESPP administrator. The number of shares reserved for issuance under the ESPP was increased by 325,916 shares effective January 1, 2018.

As of December 31, 2017, no offering periods have commenced under the ESPP.

2015 Equity Incentive Plan

Under the Company’s 2015 Equity Incentive Plan (the “2015 Plan”) the Company was authorized to sell or issue common shares or restricted common shares, or to grant options for the purchase of common shares, share appreciation rights (SARs) and other awards, to employees, members of the board of directors, consultants and advisors of the Company. Upon effectiveness of the 2017 Plan no further awards were available to be issued under the 2015 Plan.

Both the 2017 and 2015 Plans provide that they be administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices for stock options may not be less than 100% of the fair market value of the common stock on the date of grant and the term of awards may not be greater than ten years. The Company bases fair value of common stock on the quoted market price. Prior to the IPO, the Company valued its common shares by taking into consideration its most recently available third-party valuations of common shares performed under the direction of the board of directors as well as additional factors which may have changed since the date of the most recent contemporaneous valuation through the date of grant. Vesting periods are determined at the discretion of the board of directors. Awards granted to employees and directors typically vest over four years.

Conversion

In connection with the Conversion all outstanding options and share appreciation rights of Deciphera Pharmaceuticals, LLC were exchanged for options to purchase common stock of Deciphera Pharmaceuticals, Inc. Option and share appreciation amounts for periods prior to the Company’s IPO have been retrospectively adjusted to give effect to this exchange.

Stock Option Valuation

The fair value of each stock-based award is estimated on the date of grant using the Black-Scholes option-pricing model, which uses as inputs the fair value of the Company’s common stock and assumptions for the volatility of its common stock, the expected term of stock-based awards, the risk-free interest rate for a period that approximates the expected term of stock-based awards and the expected dividend yield. Prior to October 2017, the Company was privately-held and lacked company-specific historical and implied volatility information. Therefore, it estimates its expected share volatility based on the historical volatility of a set of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The Company estimated the expected term of its options using the “simplified” method for awards that qualify as “plain-vanilla” options. For options that do not qualify as “plain-vanilla”, the Company estimated the expected term using the average of vesting date and expiration date as it believes there is no better estimate of expected term. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends on common shares and does not expect to pay any cash dividends in the foreseeable future.

The assumptions that the Company used to determine the fair value of options granted to employees and directors were as follows, presented on a weighted average basis:


	Year Ended December 31,
	2017			2016			2015
Risk-free interest rate		1.9	%		1.3	%		2.0	%
Expected term (in years)		6.0			6.1			7.4
Expected volatility		78.3	%		76.1	%		86.6	%
Expected dividend yield		0	%		0	%		0	%

The following table summarizes the Company’s option activity from January 1, 2017 to December 31, 2017:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2016		3,214,452		$	2.43		9.2	$	4,890
Granted		1,553,639		$	10.02
Exercised		—			—
Forfeited		(169,739	)	$	2.58

Outstanding as of December 31, 2017		4,598,352		$	4.99		8.6	$	81,311

Options vested and expected to vest as of December 31, 2017		4,598,352		$	4.99		8.6	$	81,311

Options exercisable as of December 31, 2017		2,436,866		$	3.21		8.2	$	47,431

The aggregate intrinsic value of options is calculated as the difference between the exercise price of the options and the fair value of the Company’s common shares for those options that had exercise prices lower than the fair value of the Company’s common shares.

The weighted average grant-date fair value per share of options granted during the years ended December 31, 2017, 2016 and 2015 was $7.63, $2.43 and $1.45, respectively. The total fair value of options vested during the years ended December 31, 2017, 2016 and 2015 was $3.6 million, $0.8 million, and $1.9 million, respectively.

Stock-Based Compensation

Stock-based compensation expense was classified in the statements of operations and comprehensive loss as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Research and development expenses	$	1,320	$	541	$	1,382
General and administrative expenses		3,546		946		1,175

	$	4,866	$	1,487	$	2,557

As of December 31, 2017, total unrecognized compensation cost related to the unvested share-based awards was $8.8 million, which is expected to be recognized over a weighted average of 1.7 years.

During the year ended December 31, 2017, the Company granted 208,000 options, of which 115,918 options were immediately vested and the remaining 92,082 options vest over a weighted average period of 1.8 years.

Net Loss per Share

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Net Loss per Share

10.

Net Loss per Share

On October 2, 2017, in connection with the closing of the IPO, all outstanding convertible preferred shares of Deciphera Pharmaceuticals, LLC were exchanged for shares of common stock of Deciphera Pharmaceuticals, Inc. upon the Conversion (see Note 1). In addition, because the Company had a net loss in each of the periods presented, diluted net loss per share attributable to common shareholders has not been presented as the effect of including common share equivalents in the calculations would have had an anti-dilutive impact.

The Company did not have any common shares outstanding during the years ended December 31, 2015 and 2016 or during the period from January 1, 2017 through the closing of its initial public offering on October 2, 2017. Because the Series A convertible preferred shares represented the most subordinate share class outstanding during those periods, in determining weighted average common shares outstanding for purposes of calculating net loss per share for periods prior to the IPO, the Company utilized Series A convertible preferred shares. Such shares have also been retrospectively adjusted to give effect to the exchange of Series A convertible preferred shares into shares of common stock upon the Conversion.

Basic and diluted net loss per share was calculated as follows (in thousands, except share and per share amounts):


	Year Ended December 31,
	2017			2016			2015
Numerator:
Net loss	$	(50,284	)	$	(25,940	)	$	(19,816	)

Denominator:
Weighted average common shares outstanding—basic and diluted		16,792,179			11,626,287			4,245,698

Net loss per share —basic and diluted	$	(2.99	)	$	(2.23	)	$	(4.67	)

Common Stock Equivalents

The following potential dilutive securities, presented based on amounts outstanding at the end of each reporting period, have been excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive impact:


	December 31,
	2017		2016		2015
Series B Shares (as converted to common shares)⁽¹⁾		—		8,898,527		3,947,060
Options to purchase common stock⁽¹⁾		4,598,352		3,214,452		2,241,679

		4,598,352		12,112,979		6,188,739

(1)	Adjusted for the Conversion as described in Note 1

Commitments and Contingencies

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

11.

Commitments and Contingencies

Leases

The Company has a three-year sublease agreement for office space in Waltham, Massachusetts that began in September 2016 and expires in September 2019. Prior to this lease, the Company had a lease agreement for office space in Waltham, Massachusetts that expired in September 2016.

The Company has two five-year lease agreements for office and laboratory space in Lawrence, Kansas that began on January 1, 2016 and expire on December 31, 2020. During 2017, the Company entered into two leases for additional office space in Lawrence, Kansas, that will expire in December 2020, with annual payments due of $0.1 million.

Payment escalations specified in the lease agreements are accrued, and rent expense is recognized on a straight-line basis over the terms of occupancy.

The Company recorded rent expense of $0.6 million, 0.4 million and $0.2 million during the years ended December 31, 2017, 2016 and 2015, respectively.

The following table summarizes the future minimum lease payments due under the operating leases as of December 31, 2017 (in thousands):


Year Ending December 31,
2018	$	675
2019		578
2020		374

	$	1,627

KBA Grants

Prior to 2014, the Company received funding from two research and development grants from the KBA totaling $2.0 million. As of December 31, 2013, no further amounts will be received under these grants. Pursuant to Kansas law, the Company may be required to repay some or all of the financial assistance received from the KBA, subject to the discretion of the KBA, if the Company relocates the operations in which the KBA invested outside of the State of Kansas, if the Company initiates procedures to dissolve and wind up or cease operations within ten years after receiving such financial assistance, or upon certain significant changes to ownership of the Company. The Company will only account for the repayment of the grants if it becomes probable that the Company will be required to repay any funds previously received.

Legal Proceedings

The Company is not currently a party to any material legal proceedings. At each reporting date, the Company evaluates whether or not a potential loss amount or a potential range of loss is probable and reasonably estimable under the provisions of the authoritative guidance that addresses accounting for contingencies. The Company expenses the costs related to its legal proceedings as they are incurred.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and senior management that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any claims under indemnification arrangements, and it has not accrued any liabilities related to such obligations in its consolidated financial statements as of December 31, 2017 or 2016.

Income Taxes

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Income Taxes

12.

Income Taxes

Prior to the Conversion, the Company has been treated as a partnership for tax purposes and has not been subject to U.S. federal or state income taxation. As a result, since its inception, the Company has not recorded any U.S. federal or state income tax benefits for the net losses incurred in each year or for earned research and orphan drug credits. Upon the Conversion in October 2017, the Company became subject to Corporate U.S. federal and state income taxes.

During the period from October 2, 2017 to December 31, 2017, the Company recorded no income tax benefits for the net operating losses, due to its uncertainty of realizing a benefit from those items.

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31, 2017
Federal statutory income tax rate		34.0	%
State taxes, net of federal benefit		1.6
Federal research and orphan drug credit		7.7
Federal research and orphan drug credit addback		(6.6	)
Impact of change in tax status		(8.7	)
Effect of federal tax law change		(6.1	)
Permanent adjustments		(0.3	)
Increase in the valuation allowance		(21.6	)

Effective income tax rate		—	%

Net deferred tax assets as of December 31, 2017 consisted of the following (in thousands):


	December 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$	4,030
Research and orphan drug credit carryforwards		3,888
Stock-based compensation		2,366
Accrued expenses		672
Other		(121	)

Total gross deferred tax assets		10,835

Valuation allowance		(10,835	)

Net deferred tax assets	$	—

On December 22, 2017, the Tax Cuts and Jobs Act (the “TCJA”) was signed into United States law. The TCJA includes a number of changes to existing tax law, including, among other things, a permanent reduction in the federal corporate income tax rate from a top marginal rate of 35% to a flat rate of 21%, effective as of January 1, 2018, as well as limitation of the deduction for net operating losses to 80% of annual taxable income and elimination of net operating loss carrybacks, in each case, for losses arising in taxable years beginning after December 31, 2017 (though any such net operating losses may be carried forward indefinitely).

The Company remeasured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future. The provisional amount related to the re-measurement of the Company’s deferred tax balance was a reduction of $3.1 million. Due to the corresponding valuation allowance fully offsetting deferred taxes, there was no impact to the statement of operations and comprehensive loss.

In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118) which allows the Company to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. Since the Act was passed late in the fourth quarter of 2017, and ongoing guidance and accounting interpretation are expected over the next 12 months, the Company considers the accounting for the effect of the TCJA to be provisional in accordance with SAB 118.

Upon the Conversion in October 2017, the Company became subject to U.S. federal and state income taxes. The change in the valuation allowance was as follows (in thousands):


	Year Ended December 31, 2017
Valuation allowance as of beginning of year	$	—
Decreases recorded as benefit to income tax provision		—
Increases recorded to income tax provision		(10,835	)

Valuation allowance as of end of year	$	(10,835	)

As of December 31, 2017, the Company had net operating loss carryforwards for federal and state income tax purposes of $14.9 million and $15.2 million, respectively, which begin to expire in 2037 and 2027, respectively. As of December 31, 2017, the Company also had available research and orphan drug credit carryforwards for federal and state income tax purposes of $3.8 million and less than $0.1 million, respectively, which begin to expire in 2037 and 2032, respectively. Utilization of the net operating loss carryforwards and research and orphan drug credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended, (the “Code”), and similar state law due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. The Company has not conducted a formal study to assess whether a change of control has occurred or whether there have been multiple changes of control since the IPO due to the significant complexity and cost associated with such a study. If the Company has experienced a change of control, as defined by Section 382 of the Code and similar state law, at any time since the IPO, utilization of the net operating loss carryforwards or research and orphan drug credit carryforwards may be subject to an annual limitation under Section 382 of the Code, which is determined by first multiplying the value of the Company’s stock at the time of the ownership change by the applicable long-term tax-exempt rate, and then could be subject to additional adjustments, as required. Any limitation may result in expiration of a portion of the net operating loss carryforwards or research and orphan drug credit carryforwards before utilization.

The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the deferred tax assets as of December 31, 2017. Management reevaluates the positive and negative evidence at each reporting period.

The Company has not recorded any amounts for unrecognized tax benefits as of December 31, 2017.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending income tax examinations. The Company’s tax years that are open under statute are from October 2, 2017 to the present. The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision.

401(k) Savings Plan

12 Months Ended

Dec. 31, 2017

Retirement Benefits [Abstract]

401(k) Savings Plan

13.

401(k) Savings Plan

The Company has a defined contribution plan under Section 401(k) of the Internal Revenue Code that is managed by CRL, a related party (the “2015 401(k) Plan”). Under the 2015 401(k) Plan, the Company provides matching contributions up to 50% of actual dollars contributed, not to exceed a maximum of 4% of gross wages, subject to certain time-based vesting requirements. Total employer matching contributions related to the 2015 401(k) Plan were $0.1 million the year ended December 31, 2017 and less than $0.1 million for each of the years ended December 31, 2016 and 2015. Effective January 1, 2017, the matching contribution limit was increased to up to 50% of actual dollars contributed, not to exceed a maximum of 6% of gross wages.

Related Parties

12 Months Ended

Dec. 31, 2017

Related Parties

14.

Related Parties

Clinical Reference Laboratory, Inc.

One of the members of the Company’s board of directors is the Chief Executive Officer of CRL. CRL is the owner of approximately 31% of Brightstar, a holder of more than 5% of the Company’s common stock.

The Company is a party to a loan agreement and a security agreement, each dated as of June 11, 2010, with CRL. The Company borrowed an aggregate of $2.8 million under the loan agreement to finance improvements to the Company’s biology and chemistry laboratories in Lawrence, Kansas. In December 2016, the loan was assigned to CHC, Inc., a related party, which owns 100% of CRL. Borrowings under the loan bear interest at a fixed rate equal to 6.0% per annum and the Company is required to make monthly payments of principal and interest, based on a 15-year straight-line amortization schedule. For each of the years ended December 31, 2017, 2016 and 2015, the Company recorded $0.1 million of interest expense related to this loan. For each of the years ended December 31, 2017, 2016 and 2015, the Company made $0.3 million in principal and interest payments under the loan. As of December 31, 2017 and 2016, principal amounts owed under the loan agreement totaled $1.5 million and $1.7 million, respectively (see Note 6).

The Company is party to a master services agreement, effective as of May 20, 2013, with CRL under which the Company purchased and expects to continue to purchase laboratory services. Under the agreement, the Company has agreed to use CRL on an exclusive basis for laboratory testing needs. For the years ended December 31, 2017, 2016 and 2015, the Company recorded $0.4 million, $0.2 million and $0.1 million, respectively, of research and development expense incurred under this agreement, of which $0.4 million, $0.1 million and less than $0.1 million, respectively, were paid to CRL during those same periods. As of December 31, 2017 and 2016, total amounts owed to CRL for laboratory services were $0.1 million and less than $0.1 million, respectively, which amounts were included in accounts payable and accrued expenses. The Company is not committed to purchase any minimum amounts under the agreement.

In 2015, the Company entered into an agreement with CRL under which the Company became a participating employer in CRL’s 401(k) plan. For each of the years ended December 31, 2017, 2016 and 2015, the total amount of contributions made by employees of the Company under the plan was $0.6 million, $0.2 million and $0.2 million, respectively.

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Data (Unaudited)

15.

Selected Quarterly Financial Data (Unaudited)

The following information has been derived from unaudited consolidated financial statements that, in the opinion of management, include all recurring adjustments necessary for a fair statement of such information. (in thousands) except per share data:


	Three Months Ended
	Dec. 31, 2017			Sept. 30, 2017			June 30, 2017			March 31, 2017			Dec. 31, 2016			Sept. 30, 2016			June 30, 2016			March 31, 2016
Statements of Operations Data:
Revenue	$	—		$	—		$	—		$	—		$	—		$	—		$	—		$	—
Loss from operations		(20,338	)		(12,181	)		(10,691	)		(7,725	)		(8,534	)		(6,067	)		(5,913	)		(5,324	)
Net loss		(19,912	)		(12,038	)		(10,626	)		(7,708	)		(8,557	)		(6,099	)		(5,932	)		(5,352	)
Net loss per share—basic and diluted⁽¹⁾		(0.62	)		(1.04	)		(0.91	)		(0.66	)		(0.74	)		(0.52	)		(0.51	)		(0.46	)

(1)

The Company did not have any common shares outstanding for all periods through September 30, 2017. For purposes of calculating net loss per share, amounts for periods prior to the Company’s IPO have been retrospectively adjusted to give effect to the exchange of Series A convertible preferred shares into shares of common stock upon the Conversion described in Note 1 because series A preferred shares represent the most subordinated share class outstanding during those periods.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Use of Estimates

Use of Estimates

Cash Equivalents

Cash Equivalents

The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents.

Concentrations of Credit Risk and of Significant Suppliers

Concentrations of Credit Risk and of Significant Suppliers

Deferred Offering Costs

Deferred Offering Costs

Property and Equipment

Property and Equipment


		Estimated Useful Life
Lab equipment		5 to 7 years
Computer equipment		3 to 5 years
Furniture and fixtures		7 years
Leasehold improvements		Shorter of life of lease or 15 years

Impairment of Long-Lived Assets

Impairment of Long-Lived Assets

Fair Value Measurements

Fair Value Measurements

•

Level 1—Quoted prices in active markets for identical assets or liabilities.

•

Segment Information

Segment Information

Research and Development Costs

Research and Development Costs

Research Contract Costs and Accruals

Research Contract Costs and Accruals

Patent Costs

Patent Costs

Stock-Based Compensation

Stock-Based Compensation

Income Taxes

Income Taxes

Comprehensive Loss

Comprehensive Loss

Net Loss per Share

Net Loss per Share

Recently Issued Accounting Pronouncements

Recently Issued Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2017

Accounting Policies [Abstract]

Summary of Estimated Useful life of Assets

Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows:


		Estimated Useful Life
Lab equipment		5 to 7 years
Computer equipment		3 to 5 years
Furniture and fixtures		7 years
Leasehold improvements		Shorter of life of lease or 15 years

Fair Value of Financial Assets (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Schedule of Financial Assets Measured at Fair Value on a Recurring Basis


	Fair Value Measurements at December 31, 2017 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	191,950	$	—	$	191,950

Total	$	—	$	191,950	$	—	$	191,950


	Fair Value Measurements at December 31, 2016 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	53,180	$	—	$	53,180

Total	$	—	$	53,180	$	—	$	53,180

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2017

Property, Plant and Equipment [Abstract]

Summary of Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):


	December 31,
	2017			2016
Laboratory equipment	$	981		$	602
Leasehold improvements		344			349
Computer equipment		300			225
Furniture and fixtures		128			104

		1,753			1,280
Less: Accumulated depreciation and amortization		(915	)		(766	)

	$	838		$	514

Accrued Expenses (Tables)

12 Months Ended

Dec. 31, 2017

Payables and Accruals [Abstract]

Schedule of Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	December 31,
	2017		2016
Accrued external research and development expenses	$	6,625	$	1,433
Accrued payroll and related expenses		2,233		1,267
Accrued professional fees		353		240
Accrued other		22		17

	$	9,233	$	2,957

Notes Payable to Related Parties (Tables)

12 Months Ended

Dec. 31, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Notes Payable to Related Party

Notes payable to related party as of December 31, 2017 and 2016 consisted only of outstanding borrowings under the CRL Construction Loan, as follows (in thousands):


	December 31,
	2017			2016
Notes payable to related party	$	1,481		$	1,668
Less: Current portion		(187	)		(187	)

Notes payable to related party, net of current portion	$	1,294		$	1,481

Schedules Payments of Principal and Interest

As of December 31, 2017, scheduled payments of principal and interest for the CRL Construction Loan are as follows (in thousands):


Year ending December 31,	Principal		Interest		Total
2018	$	187	$	84	$	271
2019		187		73		260
2020		187		61		248
2021		187		50		237
2022		187		39		226
Thereafter		546		49		595

	$	1,481	$	356	$	1,837

Convertible Preferred Shares (Tables)

12 Months Ended

Dec. 31, 2017

Text Block [Abstract]

Schedule of Preferred Shares

As of December 31, 2016, the Preferred Shares consisted of the following (in thousands, except share amounts):


	Preferred Shares Authorized		Preferred Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion⁽¹⁾
Series A Shares		2,057,750		2,057,750	$	102,556	$	103,484		11,626,287
Series B-1 Shares		698,595		698,595		34,812		35,279		3,947,060
Series B-2 Shares		876,366		876,366		55,299		55,325		4,951,467

		3,632,711		3,632,711	$	192,667	$	194,088		20,524,814

(1)	Amounts reflect the exchange of convertible preferred shares into shares of common stock on a one-for 5.65 basis upon the Conversion described in Note 1.

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Assumptions used to Determine the Fair Value of Options Granted to Employees and Directors


	Year Ended December 31,
	2017			2016			2015
Risk-free interest rate		1.9	%		1.3	%		2.0	%
Expected term (in years)		6.0			6.1			7.4
Expected volatility		78.3	%		76.1	%		86.6	%
Expected dividend yield		0	%		0	%		0	%

Summary of Option Activity

The following table summarizes the Company’s option activity from January 1, 2017 to December 31, 2017:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2016		3,214,452		$	2.43		9.2	$	4,890
Granted		1,553,639		$	10.02
Exercised		—			—
Forfeited		(169,739	)	$	2.58

Outstanding as of December 31, 2017		4,598,352		$	4.99		8.6	$	81,311

Options vested and expected to vest as of December 31, 2017		4,598,352		$	4.99		8.6	$	81,311

Options exercisable as of December 31, 2017		2,436,866		$	3.21		8.2	$	47,431

Classification of Stock-Based Compensation Expense

Stock-based compensation expense was classified in the statements of operations and comprehensive loss as follows (in thousands):


	Year Ended December 31,
	2017		2016		2015
Research and development expenses	$	1,320	$	541	$	1,382
General and administrative expenses		3,546		946		1,175

	$	4,866	$	1,487	$	2,557

Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Summary of Basic and Diluted Net Loss per Share

Basic and diluted net loss per share was calculated as follows (in thousands, except share and per share amounts):


	Year Ended December 31,
	2017			2016			2015
Numerator:
Net loss	$	(50,284	)	$	(25,940	)	$	(19,816	)

Denominator:
Weighted average common shares outstanding—basic and diluted		16,792,179			11,626,287			4,245,698

Net loss per share —basic and diluted	$	(2.99	)	$	(2.23	)	$	(4.67	)

Summary of Potential Dilutive Securities


	December 31,
	2017		2016		2015
Series B Shares (as converted to common shares)⁽¹⁾		—		8,898,527		3,947,060
Options to purchase common stock⁽¹⁾		4,598,352		3,214,452		2,241,679

		4,598,352		12,112,979		6,188,739

(1)	Adjusted for the Conversion as described in Note 1

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments and Contingencies Disclosure [Abstract]

Summary of Future Minimum Lease Payments under Operating Leases

The following table summarizes the future minimum lease payments due under the operating leases as of December 31, 2017 (in thousands):


Year Ending December 31,
2018	$	675
2019		578
2020		374

	$	1,627

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended December 31, 2017
Federal statutory income tax rate		34.0	%
State taxes, net of federal benefit		1.6
Federal research and orphan drug credit		7.7
Federal research and orphan drug credit addback		(6.6	)
Impact of change in tax status		(8.7	)
Effect of federal tax law change		(6.1	)
Permanent adjustments		(0.3	)
Increase in the valuation allowance		(21.6	)

Effective income tax rate		—	%

Schedule of Net Deferred Tax Assets

Net deferred tax assets as of December 31, 2017 consisted of the following (in thousands):


	December 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$	4,030
Research and orphan drug credit carryforwards		3,888
Stock-based compensation		2,366
Accrued expenses		672
Other		(121	)

Total gross deferred tax assets		10,835

Valuation allowance		(10,835	)

Net deferred tax assets	$	—

Schedule of Changes in Valuation Allowance for Deferred Tax Assets

The change in the valuation allowance was as follows (in thousands):


	Year Ended December 31, 2017
Valuation allowance as of beginning of year	$	—
Decreases recorded as benefit to income tax provision		—
Increases recorded to income tax provision		(10,835	)

Valuation allowance as of end of year	$	(10,835	)

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2017

Quarterly Financial Information Disclosure [Abstract]

Schedule of Selected Quarterly Financial Data


	Three Months Ended
	Dec. 31, 2017			Sept. 30, 2017			June 30, 2017			March 31, 2017			Dec. 31, 2016			Sept. 30, 2016			June 30, 2016			March 31, 2016
Statements of Operations Data:
Revenue	$	—		$	—		$	—		$	—		$	—		$	—		$	—		$	—
Loss from operations		(20,338	)		(12,181	)		(10,691	)		(7,725	)		(8,534	)		(6,067	)		(5,913	)		(5,324	)
Net loss		(19,912	)		(12,038	)		(10,626	)		(7,708	)		(8,557	)		(6,099	)		(5,932	)		(5,352	)
Net loss per share—basic and diluted⁽¹⁾		(0.62	)		(1.04	)		(0.91	)		(0.66	)		(0.74	)		(0.52	)		(0.51	)		(0.46	)

(1)

Nature of the Business and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended								12 Months Ended
	Oct. 04, 2017 USD ($) $ / shares shares	Oct. 02, 2017 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Nature Of Business And Basis Of Presentation [Line Items]
Share conversion ratio		5.65										5.65
Proceeds from initial offering of shares											$ 129,112
Accumulated deficit			$ (195,869)				$ (145,585)				(195,869)	$ (145,585)
Cash and cash equivalents			196,754				57,461				196,754	57,461	$ 25,777	$ 770
Recurring losses including net losses			$ 19,912	$ 12,038	$ 10,626	$ 7,708	$ 8,557	$ 6,099	$ 5,932	$ 5,352	$ 50,284	$ 25,940	$ 19,816
IPO [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Share conversion ratio		5.65
Number of additional shares issued and sold \| shares		7,500,000
Additional offering price of common stock \| $ / shares		$ 17.00
Proceeds from initial offering of shares		$ 114,100
Over-Allotment Option [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Number of additional shares issued and sold \| shares	666,496
Additional offering price of common stock \| $ / shares	$ 17.00
Proceeds from additional offering of shares	$ 10,500

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Deferred offering costs	$ 0	$ 104,000
Method of depreciation and amortization expense calculation	Straight-line method
Impairment losses on long-lived assets	$ 0	$ 0	$ 0
No Par Value Common Stock [Member]
Significant Accounting Policies [Line Items]
Common stock, shares outstanding	0	0	0
CRL Construction Loan [Member]
Significant Accounting Policies [Line Items]
Fair value of outstanding notes payable to related party	$ 1,200,000	$ 1,300,000
Minimum [Member]
Significant Accounting Policies [Line Items]
Income tax examination, likelihood percentage	50

Summary of Significant Accounting Policies - Summary of Estimated Useful life of Assets (Detail)	12 Months Ended
	Dec. 31, 2017
Lab Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	5 years
Lab Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	7 years
Computer Equipment [Member] \| Minimum [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	3 years
Computer Equipment [Member] \| Maximum [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	5 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	7 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment estimated useful lives	Shorter of life of lease or 15 years

Fair Value of Financial Assets - Schedule of Financial Assets Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Cash equivalents:
Total Cash equivalents	$ 191,950	$ 53,180
Money Market Funds [Member]
Cash equivalents:
Total Cash equivalents	191,950	53,180
Level 2 [Member]
Cash equivalents:
Total Cash equivalents	191,950	53,180
Level 2 [Member] \| Money Market Funds [Member]
Cash equivalents:
Total Cash equivalents	$ 191,950	$ 53,180

Fair Value of Financial Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Transfers between Level 1, Level 2 and Level 3	$ 0	$ 0

Property and Equipment, Net - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,753	$ 1,280
Less: Accumulated depreciation and amortization	(915)	(766)
Property and equipment, net	838	514
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	981	602
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	344	349
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	300	225
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 128	$ 104

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 150	$ 90	$ 73

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts Payable and Accrued Liabilities [Abstract]
Accrued external research and development expenses	$ 6,625	$ 1,433
Accrued payroll and related expenses	2,233	1,267
Accrued professional fees	353	240
Accrued other	22	17
Accrued Expenses	$ 9,233	$ 2,957

Notes Payable to Related Parties - Additional Information (Detail)	1 Months Ended		12 Months Ended			82 Months Ended
	Sep. 30, 2015 USD ($) shares	May 31, 2015 USD ($) $ / shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2013 USD ($) Arrangements	Jul. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 30, 2010 USD ($)
Related Party Transaction [Line Items]
Accrued interest, current			$ 9,233,000	$ 2,957,000
Gain on extinguishment recognized as additional paid-in capital					$ 1,487,000
Conversion of 2004 Loan and Pre-2015 Convertible Loans [Member]
Related Party Transaction [Line Items]
Outstanding principal and accrued interest	$ 95,600,000
Carrying value of debt	$ 94,100,000
Series A Convertible Preferred Stock [Member] \| Conversion of 2004 Loan and Pre-2015 Convertible Loans [Member]
Related Party Transaction [Line Items]
Conversion of shares \| shares	1,855,250
Brightstar [Member] \| 2004 Convertible Loans Agreement [Member]
Related Party Transaction [Line Items]
Accrued interest, current		$ 5,000,000
Outstanding principal and accrued interest		12,600,000
Carrying value of debt		12,600,000
Fair value of convertible debt		11,100,000
Gain on extinguishment recognized as additional paid-in capital		1,500,000
Unamortized debt discounts		0
Debt issuance costs		$ 0
Brightstar [Member] \| 2004 Convertible Loans Agreement [Member] \| Unit Distribution [Member]
Related Party Transaction [Line Items]
Notes converted in to member units, per unit \| $ / shares		$ 51.52
Brightstar and Biochenomix, L.L.C. [Member] \| 2006 through 2013 Convertible Loan Agreements [Member]
Related Party Transaction [Line Items]
Number of convertible loan agreements \| Arrangements						5
Aggregate borrowings						$ 70,100,000
Amount drew down								$ 66,200,000
Remaining amount drawn down					3,900,000
Brightstar and Biochenomix, L.L.C. [Member] \| 2015 Convertible Loans Agreements [Member]
Related Party Transaction [Line Items]
Outstanding principal and accrued interest	$ 3,700,000
Aggregate borrowings		$ 15,000,000
Amount drew down		$ 2,000,000					$ 1,700,000
Brightstar and Biochenomix, L.L.C. [Member] \| Series B-1 Convertible Preferred Stock [Member] \| 2015 Convertible Loans Agreements [Member]
Related Party Transaction [Line Items]
Conversion of shares \| shares	73,811
Clinical Reference Laboratory, Inc. [Member] \| Loan and Security Agreement [Member]
Related Party Transaction [Line Items]
Aggregate borrowings			$ 2,800,000						$ 2,800,000
Fixed interest rate									6.00%
Debt instrument payment term			15-year straight-line amortization schedule
Total interest expense			$ 100,000	100,000	100,000
CRL Construction Loan [Member]
Related Party Transaction [Line Items]
Total interest expense			$ 100,000	$ 100,000	$ 2,200,000

Notes Payable to Related Parties - Schedule of Notes Payable to Related Party (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Less: Current portion	$ (187)	$ (187)
Notes payable to related party, net of current portion	1,294	1,481
CRL Construction Loan [Member]
Related Party Transaction [Line Items]
Notes payable to related party	1,481	1,668
Less: Current portion	(187)	(187)
Notes payable to related party, net of current portion	$ 1,294	$ 1,481

Notes Payable to Related Parties - Schedules Payments of Principal and Interest (Detail) - CRL Construction Loan [Member] - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Principal	$ 1,481	$ 1,668
Interest	356
Total	1,837
2018 [Member]
Related Party Transaction [Line Items]
Principal	187
Interest	84
Total	271
2019 [Member]
Related Party Transaction [Line Items]
Principal	187
Interest	73
Total	260
2020 [Member]
Related Party Transaction [Line Items]
Principal	187
Interest	61
Total	248
2021 [Member]
Related Party Transaction [Line Items]
Principal	187
Interest	50
Total	237
2022 [Member]
Related Party Transaction [Line Items]
Principal	187
Interest	39
Total	226
Thereafter [Member]
Related Party Transaction [Line Items]
Principal	546
Interest	49
Total	$ 595

Convertible Preferred Shares - Additional Information (Detail)		1 Months Ended					12 Months Ended
	Oct. 02, 2017 $ / shares shares	Oct. 31, 2017 shares	May 31, 2017 USD ($) $ / shares shares	Jul. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 shares
Redeemable Noncontrolling Interest [Line Items]
Member units outstanding \| shares					2,756,345		0	3,632,711	2,756,345	0
Proceeds from issuance of convertible preferred shares							$ 52,300,000	$ 55,324,000	$ 31,552,000
Payments of convertible preferred share issuance costs							429,000	$ 25,000	$ 498,000
Beneficial conversion feature							$ 0
Conversion of preferred stock to common stock \| shares	24,425,190	24,425,190
Share conversion ratio	5.65							5.65
Options to purchase common stock \| shares	4,092,710
Weighted average exercise price \| $ / shares	$ 3.37
Voting right description							The holders of Preferred Shares were entitled to vote, together with the holders of common shares, on all matters submitted to shareholders for a vote. Each preferred shareholder was entitled to the number of votes equal to the number of common shares into which each Preferred Share was convertible at the time of such vote.
2004 Loan and Pre-2015 Convertible Loans [Member]
Redeemable Noncontrolling Interest [Line Items]
Outstanding principal and interest						$ 95,600,000
Carrying value of debt						94,100,000
2015 Convertible Loans [Member]
Redeemable Noncontrolling Interest [Line Items]
Outstanding principal and interest						$ 3,700,000
IPO [Member]
Redeemable Noncontrolling Interest [Line Items]
Share conversion ratio	5.65
Series C Convertible Preferred Shares [Member]
Redeemable Noncontrolling Interest [Line Items]
Proceeds from issuance of convertible preferred shares			$ 51,900,000
Number of convertible preferred shares sold under share purchase agreement \| shares			690,333
Convertible preferred shares sold under share purchase agreement, price per share \| $ / shares			$ 75.76
Payments of convertible preferred share issuance costs			$ 400,000
Convertible Preferred Shares [Member]
Redeemable Noncontrolling Interest [Line Items]
Dividends and Distributions terms							There are no stated dividends on the Preferred Shares; however, holders of Preferred Shares are entitled to receive distributions when, as and if approved by the board of directors of the Company and together with holders of common shares in proportion to the number of common shares into which each Preferred Share is convertible at the time of such distribution. Additionally, to the extent the Company has sufficient cash available, without incurring any borrowings, the Company shall make a tax distribution in an amount of cash equal to the excess, if any, of (i) the product of the net taxable income or gain of the Company for the year allocated to each member and the highest combined marginal federal, state and local income tax rate applicable to residents in Kansas over (ii) the aggregate amount of distributions previously made to such member during such taxable year.
Dividend							$ 0
Distributions approved or paid							0
Series A Convertible Preferred Stock [Member]
Redeemable Noncontrolling Interest [Line Items]
Member units outstanding \| shares					202,500			2,057,750	202,500
Conversion of notes payable and accrued interest into convertible preferred shares \| shares						1,855,250
Series B-1 Convertible Preferred Stock [Member]
Redeemable Noncontrolling Interest [Line Items]
Member units outstanding \| shares								698,595
Proceeds from issuance of convertible preferred shares					$ 31,600,000	$ 31,600,000
Conversion of notes payable and accrued interest into convertible preferred shares \| shares						73,811
Number of convertible preferred shares sold under share purchase agreement \| shares					624,784	624,784
Convertible preferred shares sold under share purchase agreement, price per share \| $ / shares					$ 50.50	$ 50.50			$ 50.50
Payments of convertible preferred share issuance costs					$ 500,000	$ 500,000
Series B-2 Convertible Preferred Stock [Member]
Redeemable Noncontrolling Interest [Line Items]
Member units outstanding \| shares								876,366
Proceeds from issuance of convertible preferred shares				$ 55,300,000		55,300,000
Number of convertible preferred shares sold under share purchase agreement \| shares				876,366
Convertible preferred shares sold under share purchase agreement, price per share \| $ / shares				$ 63.13
Proceeds from financing required							$ 5,000,000
Series B-2 Convertible Preferred Stock [Member] \| Maximum [Member]
Redeemable Noncontrolling Interest [Line Items]
Payments of convertible preferred share issuance costs				$ 100,000
Series B Convertible Preferred Shares [Member]
Redeemable Noncontrolling Interest [Line Items]
Proceeds from issuance of convertible preferred shares						$ 90,600,000

Convertible Preferred Shares - Schedule of Preferred Shares (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Temporary Equity [Line Items]
Preferred Shares Authorized	0	3,632,711
Preferred Shares Issued	0	3,632,711
Preferred Shares Outstanding	0	3,632,711	2,756,345	0
Carrying Value	$ 0	$ 192,667	$ 137,368	$ 0
Liquidation Preference		$ 194,088
Common Shares Issuable Upon Conversion		20,524,814
Series A Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized		2,057,750
Preferred Shares Issued		2,057,750
Preferred Shares Outstanding		2,057,750	202,500
Carrying Value		$ 102,556
Liquidation Preference		$ 103,484
Common Shares Issuable Upon Conversion		11,626,287
Series B-1 Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized		698,595
Preferred Shares Issued		698,595
Preferred Shares Outstanding		698,595
Carrying Value		$ 34,812
Liquidation Preference		$ 35,279
Common Shares Issuable Upon Conversion		3,947,060
Series B-2 Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized		876,366
Preferred Shares Issued		876,366
Preferred Shares Outstanding		876,366
Carrying Value		$ 55,299
Liquidation Preference		$ 55,325
Common Shares Issuable Upon Conversion		4,951,467

Convertible Preferred Shares - Schedule of Preferred Shares (Parenthetical) (Detail)		12 Months Ended
	Oct. 02, 2017	Dec. 31, 2016
Temporary Equity Disclosure [Abstract]
Share conversion ratio	5.65	5.65

Common Stock - Additional Information (Detail) - $ / shares	Dec. 31, 2017	Oct. 02, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Preferred stock, shares authorized	5,000,000	5,000,000	0
Preferred stock, par value	$ 0.01	$ 0.01	$ 0.01
No Par Value Common Stock [Member]
Class of Stock [Line Items]
Common shares, authorized	0		4,366,052
Common shares, par value	$ 0		$ 0
Par Value Common Stock [Member]
Class of Stock [Line Items]
Common shares, authorized	125,000,000	125,000,000	0
Common shares, par value	$ 0.01	$ 0.01	$ 0.01

Stock-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Millions				12 Months Ended
	Jan. 01, 2018 shares	Dec. 31, 2017 USD ($) shares	Sep. 21, 2017 shares	Dec. 31, 2017 USD ($) OfferingPeriods $ / shares shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of offering periods \| OfferingPeriods				0
Weighted average grant-date fair value per share of options granted \| $ / shares				$ 7.63	$ 2.43	$ 1.45
Total fair value of options vested \| $				$ 3.6	$ 0.8	$ 1.9
Unrecognized compensation cost related to unvested share-based awards \| $		$ 8.8		$ 8.8
Unrecognized compensation cost related to unvested share-based awards, period for recognition		1 year 8 months 12 days
Options granted				208,000
Options vested				115,918
Nonvested options		92,082		92,082
Remaining Options Vested [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				1 year 9 months 18 days
2015 Equity Incentive Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value of common stock				100.00%
2015 Equity Incentive Plan [Member] \| Employees and Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				4 years
Common Stock [Member] \| 2017 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares reserved for issuance		2,150,189	2,655,831	2,150,189
Percentage of automatic annual increase in number of shares reserved for future issuance			4.00%
Effective date from which automatic annual increase in number of shares reserved for future issuance			Jan. 01, 2018
Common Stock [Member] \| 2017 Equity Incentive Plan [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for issuance	1,303,667
Common Stock [Member] \| 2017 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares reserved for issuance			306,750
Effective date from which automatic annual increase in number of shares reserved for future issuance			Jan. 01, 2018
Date until which automatic annual increase in number of shares reserved for future issuance			Jan. 01, 2027
Automatic annual increase in number of shares reserved for future issuance			400,000
Common Stock [Member] \| 2017 Employee Stock Purchase Plan [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in shares reserved for issuance	325,916
Common Stock [Member] \| 2017 Employee Stock Purchase Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of automatic annual increase in number of shares reserved for future issuance			1.00%

Stock-Based Compensation - Summary of Assumptions used to Determine the Fair Value of Options Granted to Employees and Directors (Detail) - Common Share Option and Stock Appreciation Right Activity [Member]	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.90%	1.30%	2.00%
Expected term (in years)	6 years	6 years 1 month 6 days	7 years 4 months 24 days
Expected volatility	78.30%	76.10%	86.60%
Expected dividend yield	0.00%	0.00%	0.00%

Stock-Based Compensation - Summary of Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, Beginning Balance, Number of Shares	3,214,452
Granted, Number of Shares	1,553,639
Exercised, Number of Shares	0
Forfeited, Number of Shares	(169,739)
Outstanding, Ending Balance, Number of Shares	4,598,352	3,214,452
Options vested and expected to vest, Ending Balance, Number of Shares	4,598,352
Options exercisable, Ending Balance, Number of Shares	2,436,866
Outstanding, Beginning Balance, Weighted Average Exercise Price	$ 2.43
Granted, Weighted Average Exercise Price	10.02
Exercised, Weighted Average Exercise Price	0
Forfeited, Weighted Average Exercise Price	2.58
Outstanding, Ending Balance, Weighted Average Exercise Price	4.99	$ 2.43
Options vested and expected to vest, Ending Balance, Weighted Average Exercise Price	4.99
Options exercisable, Ending Balance, Weighted Average Exercise Price	$ 3.21
Outstanding, Beginning Balance, Weighted Average Remaining Contractual Term	8 years 7 months 6 days	9 years 2 months 12 days
Options vested and expected to vest, Ending Balance, Weighted Average Remaining Contractual Term	8 years 7 months 6 days
Options exercisable, Ending Balance, Weighted Average Remaining Contractual Term	8 years 2 months 12 days
Outstanding, Beginning Balance, Aggregate Intrinsic Value	$ 81,311	$ 4,890
Options vested and expected to vest, Ending Balance, Aggregate Intrinsic Value	81,311
Options exercisable, Ending Balance, Aggregate Intrinsic Value	$ 47,431

Stock-Based Compensation - Classification of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 4,866	$ 1,487	$ 2,557
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	1,320	541	1,382
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 3,546	$ 946	$ 1,175

Net Loss per Share - Additional Information (Detail) - shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
No Par Value Common Stock [Member]
Earnings Per Share [Line Items]
Common stock, shares outstanding	0	0	0

Net Loss per Share - Summary of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net loss									$ (50,284)	$ (25,940)	$ (19,816)
Denominator:
Weighted average common shares outstanding-basic and diluted									16,792,179	11,626,287	4,245,698
Net loss per share-basic and diluted	$ (0.62)	$ (1.04)	$ (0.91)	$ (0.66)	$ (0.74)	$ (0.52)	$ (0.51)	$ (0.46)	$ (2.99)	$ (2.23)	$ (4.67)

Net Loss per Share - Summary of Potential Dilutive Securities (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	4,598,352	12,112,979	6,188,739
Series B Convertible Preferred Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share		8,898,527	3,947,060
Options to Purchase Common Shares [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	4,598,352	3,214,452	2,241,679

Commitments and Contingencies - Additional Information (Detail)		1 Months Ended	12 Months Ended
	Dec. 31, 2013 USD ($) award	Dec. 31, 2015 Lease	Dec. 31, 2017 USD ($) Lease	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2013 USD ($)
Other Commitments [Line Items]
Rent expense			$ 600,000	$ 400,000	$ 200,000
KBA Grants [Member]
Other Commitments [Line Items]
Number of awards grants \| award	2
Amount of grants awarded	$ 2,000,000					$ 0
Sublease Agreement for Office Space in Waltham, Massachusetts [Member]
Other Commitments [Line Items]
Sublease term			3 years
Sublease expiration date			Sep. 30, 2019
Lease for Additional Office Space in Lawrence, Kansas [Member]
Other Commitments [Line Items]
Number of lease agreement \| Lease			2
Operating lease expiry date			Dec. 31, 2020
Annual payments			$ 100,000
Lease Agreement for Office and Laboratory Space in Lawrence, Kansas [Member]
Other Commitments [Line Items]
Number of lease agreement \| Lease		2
Operating lease expiry date		Dec. 31, 2020
Lease term		5 years

Commitments and Contingencies - Summary of Future Minimum Lease Payments under Operating Leases (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2018	$ 675
2019	578
2020	374
Future minimum lease payments due	$ 1,627

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Income tax benefits		$ 0
Federal statutory income tax rate		34.00%
Percentage of net operating loss carry forward deductible from current year taxable income		80.00%
Decrease in deferred tax asset due to Tax Cuts and Jobs Act		$ 3,100,000
Tax Cuts And Jobs Act, incomplete accounting, provisional income tax expense (benefit)		0
Research and orphan drug credit carryforwards		3,888,000
Unrecognized tax benefits		$ 0
Income tax examination, description		There are currently no pending income tax examinations. The Company's tax years that are open under statute are from October 2, 2017 to the present.
Maximum [Member]
Income Tax Disclosure [Line Items]
Federal statutory income tax rate		35.00%
Scenario, Plan [Member]
Income Tax Disclosure [Line Items]
Federal statutory income tax rate	21.00%
Earliest Tax Year [Member]
Income Tax Disclosure [Line Items]
Open tax year		2017
Latest Tax Year [Member]
Income Tax Disclosure [Line Items]
Open tax year		2017
Federal [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		$ 14.9
Net operating loss carryforwards expiration year		2037
Research and orphan drug credit carryforwards		$ 3,800,000
Tax credit carryforwards expiration year		2037
State [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		$ 15.2
Net operating loss carryforwards expiration year		2027
Research and orphan drug credit carryforwards		$ 100,000
Tax credit carryforwards expiration year		2032

Income Taxes - Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	34.00%
State taxes, net of federal benefit	1.60%
Federal research and orphan drug credit	7.70%
Federal research and orphan drug credit addback	(6.60%)
Impact of change in tax status	(8.70%)
Effect of federal tax law change	(6.10%)
Permanent adjustments	(0.30%)
Increase in the valuation allowance	(21.60%)
Effective income tax rate	0.00%

Income Taxes - Schedule of Net Deferred Tax Assets (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Deferred tax assets:
Net operating loss carryforwards	$ 4,030
Research and orphan drug credit carryforwards	3,888
Stock-based compensation	2,366
Accrued expenses	672
Other	(121)
Total gross deferred tax assets	10,835
Valuation allowance	(10,835)
Net deferred tax assets	$ 0

Income Taxes - Schedule of Changes in Valuation Allowance for Deferred Tax Assets (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Income Tax Disclosure [Abstract]
Decreases recorded as benefit to income tax provision	$ 0
Increases recorded to income tax provision	(10,835)
Valuation allowance as of end of year	$ (10,835)

401(k) Savings Plan - Additional Information (Detail) - Clinical Reference Laboratory, Inc. [Member] - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan description		Under the 2015 401(k) Plan, the Company provides matching contributions up to 50% of actual dollars contributed, not to exceed a maximum of 4% of gross wages, subject to certain time-based vesting requirements.
Matching contributions to the plan by employer		$ 100,000
Percentage of salary for matching contribution per employee		6.00%
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of matching contribution to plan	50.00%	50.00%
Percentage of salary for matching contribution per employee on time-based vesting	4.00%
Matching contributions to the plan by employer			$ 100,000	$ 100,000

Related Parties - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2010
Related Party Transaction [Line Items]
Research and development expense	$ 39,514,000	$ 20,163,000	$ 12,475,000
Clinical Reference Laboratory, Inc. [Member] \| Loan and Security Agreement [Member]
Related Party Transaction [Line Items]
Aggregate borrowings	$ 2,800,000			$ 2,800,000
Fixed interest rate				6.00%
Debt instrument payment term	15-year straight-line amortization schedule
Interest expense on borrowings	$ 100,000	100,000	100,000
Debt instrument principal and interest payment	300,000	300,000	300,000
Principal amount owed under loan agreement	1,500,000	1,700,000
Clinical Reference Laboratory, Inc. [Member] \| Service Agreement [Member]
Related Party Transaction [Line Items]
Research and development expense	400,000	200,000	100,000
Payments for research and development expense	400,000	100,000
Employees contributions under 401(K) plan	600,000	200,000	200,000
Clinical Reference Laboratory, Inc. [Member] \| Maximum [Member]
Related Party Transaction [Line Items]
Payments for research and development expense			$ 100,000
Laboratory services	$ 100,000	$ 100,000
Clinical Reference Laboratory, Inc. [Member] \| CHC, Inc. [Member] \| Loan and Security Agreement [Member]
Related Party Transaction [Line Items]
Ownership percentage		100.00%
Fixed interest rate		6.00%
Debt instrument payment term	15-year straight-line amortization schedule
Debt instrument term	15 years
Clinical Reference Laboratory, Inc. [Member] \| Brightstar [Member]
Related Party Transaction [Line Items]
Ownership percentage	31.00%
Clinical Reference Laboratory, Inc. [Member] \| Brightstar [Member] \| Minimum [Member]
Related Party Transaction [Line Items]
Percentage of common stock holding	5.00%

Selected Quarterly Financial Data (Unaudited) - Schedule of Selected Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statements of Operations Data:
Revenue	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Loss from operations	(20,338)	(12,181)	(10,691)	(7,725)	(8,534)	(6,067)	(5,913)	(5,324)	(50,935)	(25,838)	(17,610)
Net loss	$ (19,912)	$ (12,038)	$ (10,626)	$ (7,708)	$ (8,557)	$ (6,099)	$ (5,932)	$ (5,352)	$ (50,284)	$ (25,940)	$ (19,816)
Net loss per share-basic and diluted	$ (0.62)	$ (1.04)	$ (0.91)	$ (0.66)	$ (0.74)	$ (0.52)	$ (0.51)	$ (0.46)	$ (2.99)	$ (2.23)	$ (4.67)

Selected Quarterly Financial Data (Unaudited) - Schedule of Selected Quarterly Financial Data (Parenthetical) (Detail) - shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
No Par Value Common Stock [Member]
Quarterly Financial Data [Line Items]
Common stock, shares outstanding	0	0	0