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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2017	Oct. 31, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q3
Trading Symbol	DCPH
Entity Registrant Name	DECIPHERA PHARMACEUTICALS, INC.
Entity Central Index Key	0001654151
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		32,591,686

Balance Sheets - USD ($)	Sep. 30, 2017	Aug. 01, 2017	Dec. 31, 2016
Members' Deficit:
Common shares, no par value; 5,217,929 shares authorized as of September 30, 2017 and 4,366,052 shares authorized as of December 31, 2016; no shares issued or outstanding as of September 30, 2017 or December 31, 2016	$ 0	$ 0
Total stockholders' equity	0	$ 0
Deciphera Pharmaceuticals, LLC [Member]
Current assets:
Cash and cash equivalents	82,149,000		$ 57,461,000
Prepaid expenses and other current assets	596,000		791,000
Total current assets	82,745,000		58,252,000
Property and equipment, net	731,000		514,000
Deferred offering costs	4,316,000		104,000
Other assets	75,000		75,000
Assets	87,867,000		58,945,000
Current liabilities:
Accounts payable	3,104,000		1,413,000
Accrued expenses	6,789,000		2,957,000
Notes payable to related party	187,000		187,000
Total current liabilities	10,080,000		4,557,000
Notes payable to related party, net of current portion	1,341,000		1,481,000
Other long-term liabilities	18,000
Total liabilities	11,439,000		6,038,000
Commitments and contingencies (Note 10)
Convertible preferred shares (Series A, B-1, B-2, C), no par value; 4,455,039 shares authorized at September 30, 2017 and 3,632,711 shares authorized as of December 31, 2016; 4,323,044 shares issued and outstanding as of September 30, 2017, 3,632,711 shares issued and outstanding as of December 31, 2016; aggregate liquidation preference of $246,388 as of September 30, 2017 and $194,088 as of December 31, 2016	244,538,000		192,667,000
Members' Deficit:
Common shares, no par value; 5,217,929 shares authorized as of September 30, 2017 and 4,366,052 shares authorized as of December 31, 2016; no shares issued or outstanding as of September 30, 2017 or December 31, 2016	0		0
Additional paid-in capital	7,847,000		5,825,000
Accumulated deficit	(175,957,000)		(145,585,000)
Total members' deficit	(168,110,000)		(139,760,000)
Total liabilities, convertible preferred shares and members' deficit	$ 87,867,000		$ 58,945,000

Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Common stock, par value	$ 0.01
Common stock, shares authorized	1,000
Common stock, shares issued	0
Common stock, shares outstanding	0
Deciphera Pharmaceuticals, LLC [Member]
Convertible preferred shares, shares authorized	4,455,039	3,632,711
Convertible preferred shares, no par value	$ 0	$ 0
Convertible preferred shares, shares issued	4,323,044	3,632,711
Convertible preferred shares, shares outstanding	4,323,044	3,632,711
Convertible preferred shares, aggregate liquidation preference	$ 246,388	$ 194,088
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	5,217,929	4,366,052
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0

Statements of Operations and Comprehensive Loss - Deciphera Pharmaceuticals, LLC [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenue	$ 0	$ 0	$ 0	$ 0
Operating expenses:
Research and development	9,751	4,717	23,856	13,626
General and administrative	2,430	1,350	6,741	3,678
Total operating expenses	12,181	6,067	30,597	17,304
Loss from operations	(12,181)	(6,067)	(30,597)	(17,304)
Other income (expense):
Interest expense	(23)	(26)	(72)	(81)
Other income (expense), net	166	(6)	297	2
Total other income (expense), net	143	(32)	225	(79)
Net loss and comprehensive loss	(12,038)	(6,099)	(30,372)	(17,383)
Series A Convertible Preferred Stock [Member]
Other income (expense):
Net loss attributable to Series A convertible preferred shareholders-basic and diluted	$ (12,038)	$ (6,099)	$ (30,372)	$ (17,383)
Net loss per share attributable to Series A convertible preferred shareholders-basic and diluted	$ (5.85)	$ (2.96)	$ (14.76)	$ (8.45)
Weighted average Series A convertible preferred shares outstanding-basic and diluted	2,057,750	2,057,750	2,057,750	2,057,750

Statements of Cash Flows - Deciphera Pharmaceuticals, LLC [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net loss	$ (30,372)	$ (17,383)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	2,022	950
Depreciation and amortization expense	101	60
Loss on disposal of property and equipment	10	6
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	195	59
Accounts payable	1,439	(349)
Accrued expenses	2,638	539
Other assets		(55)
Other long-term liabilities	18
Net cash used in operating activities	(23,949)	(16,173)
Cash flows from investing activities:
Purchases of property and equipment	(276)	(104)
Net cash used in investing activities	(276)	(104)
Cash flows from financing activities:
Proceeds from issuance of convertible preferred shares	52,300	55,324
Repayment of notes payable to related party	(140)	(151)
Payments of convertible preferred share issuance costs	(429)	(25)
Payments of initial public offering costs	(2,818)	(8)
Net cash provided by financing activities	48,913	55,140
Net increase in cash and cash equivalents	24,688	38,863
Cash and cash equivalents at beginning of period	57,461	25,777
Cash and cash equivalents at end of period	82,149	64,640
Supplemental disclosure of cash flow information:
Cash paid for interest	72	81
Supplemental disclosure of non-cash investing activities:
Purchases of property and equipment included in accounts payable	52
Supplemental disclosure of non-cash financing activities:
Deferred offering costs included in accounts payable or accrued expenses	$ 1,394	$ 87

Organization	9 Months Ended
Organization	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Deciphera Pharmaceuticals, Inc. (the “Company”) was formed as a Delaware corporation on August 1, 2017. The Company was formed for the sole purpose of completing an initial public offering, (the “IPO”) and related transactions in order to carry on the business of Deciphera Pharmaceuticals, LLC. The Company will be the sole managing member of Deciphera Pharmaceuticals, LLC and will operate and control all of the businesses and affairs of Deciphera Pharmaceuticals, LLC. The Company does not intend to be an operating entity and incur any expenses prior to, and independent of the IPO (see Note 4).

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2017

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The balance sheet is presented in accordance with accounting principles generally accepted in the United States of America. Separate statements of operations, of comprehensive income, of stockholders’ equity and of cash flows have not been presented in the financial statements because there have been no activities in this entity.

The Company’s fiscal year ends on December 31.

Deciphera Pharmaceuticals, LLC [Member]

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 financial statements include, but are not limited to, the accrual for research and development expenses and the valuation of common shares and share-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.

Unaudited Interim Financial Information

The balance sheet at December 31, 2016 was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. The accompanying unaudited financial statements as of September 30, 2017 and for the three and nine months ended September 30, 2017 and 2016 have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. The Company believes, however, that the disclosures are adequate to make the information presented not misleading. These financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto for the year ended December 31, 2016 included in the Company’s Registration Statement on Form S-1, File Number 333-220299 on file with SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s financial position as of September 30, 2017 and results of operations for the three and nine months ended September 30, 2017 and 2016 and cash flows for the nine months ended September 30, 2017 and 2016 have been made. The results of operations for three and nine months ended September 30, 2017 and 2016 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2017.

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 has not recorded any U.S. federal or state income tax benefits for the net losses incurred in each reporting period or for any earned research and development tax credits. Through September 30, 2017, the operating losses incurred by the Company have been passed through to its members.

As a result of the Conversion on October 2, 2017, the Company became subject to corporate U.S. federal and state income taxes (see Note 13).

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 members’ deficit as a reduction of additional paid-in capital generated as a result of the offering. As of September 30, 2017 and December 31, 2016, the Company recorded $4.3 million and $0.1 million, respectively, of deferred offering costs in contemplation of the IPO. Such costs were transferred to additional paid-in capital upon completion of the IPO on October 2, 2017.

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 5) as of September 30, 2017 and December 31, 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.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in 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 financial statements.

Net Loss per Share

The Company did not have any common shares outstanding during the three and nine months ended September 30, 2017 and 2016. Accordingly, net loss attributable to common shareholders and basic net loss per share attributable to common shareholders have not been presented in the Company’s statements of operations and comprehensive loss. 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. Net loss attributable to Series A convertible preferred shareholders and basic and diluted net loss per share attributable to Series A convertible preferred shareholders have been presented in the Company’s statements of operations and comprehensive loss for the three and nine months ended September 30, 2017 and 2016 because Series A convertible preferred shares represent the most subordinated share class outstanding during those periods.

The Company follows the two-class method when computing net income (loss) per share as the Company has issued shares that meet the definition of participating securities. The two-class method determines net income (loss) per share for each class of participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to Series A convertible preferred shareholders for the period to be allocated between participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed.

Basic net income (loss) per share attributable to Series A convertible preferred shareholders is computed by dividing the net income (loss) attributable to Series A convertible preferred shareholders by the weighted average number of Series A convertible preferred shares outstanding for the period. Diluted net income (loss) attributable to Series A convertible preferred shareholders is computed by adjusting net income (loss) attributable to Series A convertible preferred shareholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share attributable to Series A convertible preferred shareholders is computed by dividing the diluted net income (loss) attributable to Series A convertible preferred shareholders by the weighted average number of Series A convertible preferred shares outstanding for the period, including potential dilutive Series A convertible preferred shares. For purposes of this calculation, outstanding notes payable convertible into Series A convertible preferred shares are considered potential dilutive Series A convertible preferred shares.

The Company’s outstanding convertible preferred shares contractually entitle the holders of such shares to participate in distributions but contractually do not require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reports a net loss, such losses are not allocated to such participating securities. In periods in which the Company reports a net loss attributable to Series A convertible preferred shareholders, diluted net loss per share attributable to Series A convertible preferred shareholders is the same as basic net loss per share attributable to Series A convertible preferred shareholders, since dilutive Series A convertible preferred shares are not assumed to have been issued if their effect is anti-dilutive.

The Company reported a net loss attributable to Series A convertible preferred shareholders for the three and nine months ended September 30, 2017 and 2016.

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. Early adoption of the standard is permitted for annual periods beginning after December 15, 2016. 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 Company does not intend to early adopt these accounting standards and will apply the modified-retrospective method. 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.

Common Shares	9 Months Ended
Common Shares	Sep. 30, 2017
Common Shares	3. Stockholders’ Equity As of September 30, 2017 and August 1, 2017, the Company was authorized to issue 1,000 shares of common stock, par value $0.01 per share, none of which had been issued. *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. On September 21, 2017, the Board of Directors of the Company approved the grant of options to purchase 505,675 shares of common stock to certain employees and directors at an exercise price equal to the IPO price of its common stock, which was $17.00 per share, subject to the completion of the Conversion (see Note 4). *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 our common stock on the immediately preceding December 31; (ii) 400,000 shares or (iii) such number of shares as determined by the ESPP administrator. As of September 30, 2017, no offering periods have commenced under the ESPP.
Deciphera Pharmaceuticals, LLC [Member]
Common Shares	7. Common Shares In May 2017, the Company’s operating agreement was amended and restated to increase the number of common shares authorized from 4,366,052 to 5,217,929 shares.

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2017
Subsequent Events	4. Subsequent Events *Increase in Authorized Shares* On October 2, 2017, the Company’s amended and restated its certificate of incorporation to increase authorized capital stock 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. *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. *Initial Public Offering* On October 2, 2017, the Company 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 $118.6 million after deducting underwriting discounts and commissions but before other offering expenses. On October 4, 2017, the Company issued and sold an additional 666,496 shares of its common stock at the IPO price of $17.00 per share, less underwriting discounts and commissions, pursuant to the underwriters’ partial exercise of their option to purchase additional shares of common stock, resulting in additional net proceeds to the Company of $10.5 million after deducting underwriting discounts and commissions.
Deciphera Pharmaceuticals, LLC [Member]
Subsequent Events	13. Subsequent Events *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. *Initial Public Offering* On October 2, 2017, the Company completed an IPO of its common stock, and issued and sold 7,500,000 shares of common stock at a public offering price of $17.00 per share, resulting in net proceeds of $118.6 million after deducting underwriting discounts and commissions but before other offering expenses. On October 4, 2017, the Company issued and sold an additional 666,496 shares of its common stock at the IPO price of $17.00 per share, less underwriting discounts and commissions, pursuant to the underwriters partial exercise of their option to purchase additional shares of common stock, resulting in additional net proceeds to the Company of $10.5 million after deducting discounts and commissions.

Nature of the Business and Basis of Presentation	9 Months Ended
Nature of the Business and Basis of Presentation	Sep. 30, 2017
Deciphera Pharmaceuticals, LLC [Member]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Basis of Presentation Deciphera Pharmaceuticals, LLC (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. In September 2015, the Company re-domesticated from a Kansas limited liability company to a Delaware limited liability company. 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. 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”) (see Note 13). 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 $118.6 million after deducting underwriting discounts and commissions but before other offering expenses. On October 4, 2017, Deciphera Pharmaceuticals, Inc., issued and sold an additional 666,496 shares of its 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 (see Note 6). 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 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. Through September 30, 2017, the Company has funded its operations with the sales of convertible preferred shares, borrowings under convertible notes, borrowings under a construction loan, payments received in connection with a concluded collaboration agreement and grants from the Kansas Bioscience Authority (the “KBA”). Since inception, the Company has incurred recurring losses including net losses of $30.4 million for the nine months ended September 30, 2017 and $25.9 million for the year ended December 31, 2016. As of September 30, 2017, the Company had an accumulated deficit of $176.0 million. The Company expects to continue to generate operating losses in the foreseeable future. As of the issuance date of the interim financial statements, the Company expects that the $129.1 million of net proceeds after deducting underwriting discounts and commissions it received from the completion of its initial public offering (“IPO”) in October 2017, together with its cash and cash equivalents of $82.1 million as of September 30, 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 interim 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 financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”).

Fair Value of Financial Assets

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

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 September 30, 2017 Using
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	78,507	$	—	$	78,507

Total	$	—	$	78,507	$	—	$	78,507


	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

- 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

Accrued Expenses

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

Accrued Expenses

4. Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	September 30,		December 31,
	2017		2016
Accrued external research and development expenses	$	3,869	$	1,433
Accrued professional fees		1,659		240
Accrued payroll and related expenses		1,243		1,267
Accrued other		18		17

	$	6,789	$	2,957

Notes Payable to Related Party

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

Notes Payable to Related Party

5. Notes Payable to Related Party

Notes payable to related party as of September 30, 2017 and December 31, 2016 consisted of outstanding borrowings under a loan agreement and a security agreement (together, the “CRL Construction Loan”) with Clinical Reference Laboratory, Inc. (“CRL”), a related party (see Note 12), as follows (in thousands):


	September 30,			December 31,
	2017			2016
Notes payable to related party	$	1,528		$	1,668
Less: Current portion		(187	)		(187	)

Notes payable to related party, net of current portion	$	1,341		$	1,481

Total interest expense for each of the three months ended September 30, 2017 and 2016 was less than $0.1 million. Total interest expense for each of the nine months ended September 30, 2017 and 2016 was $0.1 million.

Convertible Preferred Shares

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

Convertible Preferred Shares

6. Convertible Preferred Shares

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. In connection with the Series C preferred shares purchase agreement, the Company’s operating agreement was amended and restated to authorize the Company to issue 822,328 Series C Shares.

As of each balance sheet date, the Preferred Shares consisted of the following (in thousands, except share amounts):


	September 30, 2017
	Preferred Shares Authorized		Preferred Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion
Series A Shares		2,057,750		2,057,750	$	102,556	$	103,484		2,057,750
Series B-1 Shares		698,595		698,595		34,812		35,279		698,595
Series B-2 Shares		876,366		876,366		55,299		55,325		876,366
Series C Shares		822,328		690,333		51,871		52,300		690,333

		4,455,039		4,323,044	$	244,538	$	246,388		4,323,044


	December 31, 2016
	Preferred Shares Authorized		Preferred Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion
Series A Shares		2,057,750		2,057,750	$	102,556	$	103,484		2,057,750
Series B-1 Shares		698,595		698,595		34,812		35,279		698,595
Series B-2 Shares		876,366		876,366		55,299		55,325		876,366

		3,632,711		3,632,711	$	192,667	$	194,088		3,632,711

Immediately prior to the closing of the IPO on October 2, 2017, the Company’s outstanding convertible preferred shares automatically converted into 24,425,190 shares of common stock of Deciphera Pharmaceuticals, Inc. (see Note 13).

Share-Based Awards

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

Share-Based Awards

8. Share-Based Awards

2015 Equity Incentive Plan

In May 2017, the Company’s operating agreement was amended and restated to increase the number of common shares reserved for issuance under the 2015 Equity Incentive Plan from 641,066 to 762,890 shares. Upon completion of the IPO, the Company will no longer be making any future awards under this plan (see Note 13).

Share-Based Compensation

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


	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2017		2016		2017		2016
Research and development expenses	$	459	$	189	$	797	$	382
General and administrative expenses		553		273		1,225		568

	$	1,012	$	462	$	2,022	$	950

As of September 30, 2017, total unrecognized compensation cost related to the unvested share-based awards was $4.0 million, which is expected to be recognized over a weighted average of 1.5 years.

Net Loss per Share

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Net Loss per Share

9. Net Loss per Share

Net loss attributable to Series A convertible preferred shareholders and basic and diluted net loss per share attributable to Series A convertible preferred shareholders have been presented in the Company’s statements of operations and comprehensive loss for the three and nine months ended September 30, 2017 and 2016 because Series A convertible preferred shares represent the most subordinated share class outstanding during those periods.

Basic and diluted net loss per share attributable to Series A convertible preferred shareholders was calculated as follows (in thousands, except share and per share amounts):


	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2017			2016			2017			2016
Numerator:
Net loss attributable to Series A convertible preferred shareholders	$	(12,038	)	$	(6,099	)	$	(30,372	)	$	(17,383	)

Denominator:
Weighted average Series A convertible preferred shares outstanding—basic and diluted		2,057,750			2,057,750			2,057,750			2,057,750

Net loss per share attributable to Series A convertible preferred shareholders—basic and diluted	$	(5.85	)	$	(2.96	)	$	(14.76	)	$	(8.45	)

Series A Preferred Share Equivalents

The Company had no securities outstanding as of September 30, 2017 and 2016 that represented potential Series A convertible preferred shares.

Common Share Equivalents

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


	As of September 30,
	2017		2016
Series B convertible preferred shares (as converted to common shares)		1,574,961		1,574,961
Series C convertible preferred shares (as converted to common shares)		690,333		—
Options to purchase common shares		601,556		443,849
Share appreciation rights		122,823		82,509

		2,989,673		2,101,319

Commitments and Contingencies

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

Commitments and Contingencies

10. 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. In August 2017, the Company entered into a lease for additional office space in Lawrence, Kansas, effective September 1, 2017, that will expire in December 2020, with annual payments due of less than $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 $0.1 million during each of the three months ended September 30, 2017 and 2016, respectively, and $0.4 million and $0.3 million during the nine months ended September 30, 2017 and 2016, respectively.

The following table summarizes the future minimum lease payments due under the operating leases as of September 30, 2017 (in thousands):


Remainder of 2017	$	154
2018		617
2019		519
2020		315

	$	1,605

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 financial statements as of September 30, 2017 or December 31, 2016.

401(k) Savings Plan	9 Months Ended
401(k) Savings Plan	Sep. 30, 2017
Deciphera Pharmaceuticals, LLC [Member]
401(k) Savings Plan	11. 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 less than $0.1 million for each of the three months ended September 30, 2017 and 2016 and $0.1 million for each of the nine months ended September 30, 2017 and 2016. 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	9 Months Ended
Related Parties	Sep. 30, 2017
Deciphera Pharmaceuticals, LLC [Member]
Related Parties	12. 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 Preferred Shares. 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 three months ended September 30, 2017 and 2016, the Company recorded less than $0.1 million of interest expense related to this loan. For each of the nine months ended September 30, 2017 and 2016, the Company recorded $0.1 million of interest expense related to this loan. For each of the nine months ended September 30, 2017 and 2016, the Company made $0.2 million of principal and interest payments under the loan. As of September 30, 2017 and December 31, 2016, principal amounts owed under the loan agreement totaled $1.5 million and $1.7 million, respectively (see Note 5). 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 three months ended September 30, 2017 and 2016, the Company recorded $0.2 million and $0.1 million, respectively, of research and development expense incurred under this agreement. For the nine months ended September 30, 2017 and 2016, the Company recorded $0.3 million and $0.1 million, respectively, of research and development expense incurred under this agreement, of which $0.2 million and $0.1 million, respectively, was paid to CRL during those same periods. As of September 30, 2017 and December 31, 2016, total amounts owed to CRL for laboratory services were $0.2 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 the three months ended September 30, 2017 and 2016, the total amount of contributions made by employees of the Company under the plan was $0.1 million and less than $0.1 million, respectively. For the nine months ended September 30, 2017 and 2016, the total amount of contributions made by employees of the Company under the plan was $0.4 million and $0.2 million, respectively.

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2017

Basis of Presentation

Basis of Presentation

The Company’s fiscal year ends on December 31.

Deciphera Pharmaceuticals, LLC [Member]

Use of Estimates

Use of Estimates

Unaudited Interim Financial Information

Unaudited Interim Financial Information

Income Taxes

Income Taxes

As a result of the Conversion on October 2, 2017, the Company became subject to corporate U.S. federal and state income taxes (see Note 13).

Deferred Offering Costs

Deferred Offering Costs

Fair Value Measurements

Fair Value Measurements

•

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

•

Comprehensive Loss

Comprehensive Loss

Net Loss per Share

Net Loss per Share

The Company reported a net loss attributable to Series A convertible preferred shareholders for the three and nine months ended September 30, 2017 and 2016.

Recently Issued Accounting Pronouncements

Recently Issued Accounting Pronouncements

Fair Value of Financial Assets (Tables)

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

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


	Fair Value Measurements at September 30, 2017 Using
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	78,507	$	—	$	78,507

Total	$	—	$	78,507	$	—	$	78,507


	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

Accrued Expenses (Tables)

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

Schedule of Accrued Expenses

Accrued expenses consisted of the following (in thousands):


	September 30,		December 31,
	2017		2016
Accrued external research and development expenses	$	3,869	$	1,433
Accrued professional fees		1,659		240
Accrued payroll and related expenses		1,243		1,267
Accrued other		18		17

	$	6,789	$	2,957

Notes Payable to Related Party (Tables)

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

Schedule of Notes Payable to Related Party


	September 30,			December 31,
	2017			2016
Notes payable to related party	$	1,528		$	1,668
Less: Current portion		(187	)		(187	)

Notes payable to related party, net of current portion	$	1,341		$	1,481

Convertible Preferred Shares (Tables)

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

Schedule of Preferred Shares

As of each balance sheet date, the Preferred Shares consisted of the following (in thousands, except share amounts):


	September 30, 2017
	Preferred Shares Authorized		Preferred Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion
Series A Shares		2,057,750		2,057,750	$	102,556	$	103,484		2,057,750
Series B-1 Shares		698,595		698,595		34,812		35,279		698,595
Series B-2 Shares		876,366		876,366		55,299		55,325		876,366
Series C Shares		822,328		690,333		51,871		52,300		690,333

		4,455,039		4,323,044	$	244,538	$	246,388		4,323,044


	December 31, 2016
	Preferred Shares Authorized		Preferred Shares Issued and Outstanding		Carrying Value		Liquidation Preference		Common Shares Issuable Upon Conversion
Series A Shares		2,057,750		2,057,750	$	102,556	$	103,484		2,057,750
Series B-1 Shares		698,595		698,595		34,812		35,279		698,595
Series B-2 Shares		876,366		876,366		55,299		55,325		876,366

		3,632,711		3,632,711	$	192,667	$	194,088		3,632,711

Share-Based Awards (Tables)

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

Classification of Share-Based Compensation Expense

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


	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2017		2016		2017		2016
Research and development expenses	$	459	$	189	$	797	$	382
General and administrative expenses		553		273		1,225		568

	$	1,012	$	462	$	2,022	$	950

Net Loss per Share (Tables) - Deciphera Pharmaceuticals, LLC [Member]

9 Months Ended

Sep. 30, 2017

Summary of Basic and Diluted Net Loss per Share Attributable to Series A Convertible Preferred Shareholders

Basic and diluted net loss per share attributable to Series A convertible preferred shareholders was calculated as follows (in thousands, except share and per share amounts):


	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2017			2016			2017			2016
Numerator:
Net loss attributable to Series A convertible preferred shareholders	$	(12,038	)	$	(6,099	)	$	(30,372	)	$	(17,383	)

Denominator:
Weighted average Series A convertible preferred shares outstanding—basic and diluted		2,057,750			2,057,750			2,057,750			2,057,750

Net loss per share attributable to Series A convertible preferred shareholders—basic and diluted	$	(5.85	)	$	(2.96	)	$	(14.76	)	$	(8.45	)

Summary of Potential Dilutive Securities


	As of September 30,
	2017		2016
Series B convertible preferred shares (as converted to common shares)		1,574,961		1,574,961
Series C convertible preferred shares (as converted to common shares)		690,333		—
Options to purchase common shares		601,556		443,849
Share appreciation rights		122,823		82,509

		2,989,673		2,101,319

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2017

Deciphera Pharmaceuticals, LLC [Member]

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 September 30, 2017 (in thousands):


Remainder of 2017	$	154
2018		617
2019		519
2020		315

	$	1,605

Organization - Additional Information (Detail)	9 Months Ended
Organization - Additional Information (Detail)	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Place of incorporation	Delaware
Date of formation	Aug. 01, 2017

Stockholders' Equity - Additional Information (Detail)		9 Months Ended
Stockholders' Equity - Additional Information (Detail)	Sep. 21, 2017 $ / shares shares	Sep. 30, 2017 OfferingPeriods $ / shares shares	Aug. 01, 2017 $ / shares shares
Class of Stock [Line Items]
Common stock, shares authorized		1,000	1,000
Common stock, par value \| $ / shares		$ 0.01	$ 0.01
Common stock, shares issued		0	0
Number of offering periods \| OfferingPeriods		0
Common Stock [Member] \| 2017 Equity Incentive Plan [Member]
Class of Stock [Line Items]
Number of common shares reserved for issuance	2,655,831
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 Employee Stock Purchase Plan [Member]
Class of Stock [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] \| Minimum [Member]
Class of Stock [Line Items]
Percentage of automatic annual increase in number of shares reserved for future issuance	1.00%
IPO [Member]
Class of Stock [Line Items]
Options to purchase common stock for certain employees and directors	505,675
Public offering price of common stock \| $ / shares	$ 17.00

Subsequent Events - Additional Information (Detail) $ / shares in Units, $ in Millions	Oct. 04, 2017 USD ($) $ / shares shares	Oct. 02, 2017 USD ($) $ / shares shares	Sep. 30, 2017 $ / shares shares	Sep. 21, 2017 $ / shares	Aug. 01, 2017 $ / shares shares	Dec. 31, 2016 $ / shares shares
Subsequent Event [Line Items]
Common stock, shares authorized			1,000		1,000
Common stock, par value \| $ / shares			$ 0.01		$ 0.01
Deciphera Pharmaceuticals, LLC [Member]
Subsequent Event [Line Items]
Common stock, shares authorized			5,217,929			4,366,052
Common stock, par value \| $ / shares			$ 0			$ 0
IPO [Member]
Subsequent Event [Line Items]
Public offering price of common stock \| $ / shares				$ 17.00
Subsequent Event [Member]
Subsequent Event [Line Items]
Common stock, shares authorized		125,000,000
Preferred stock, shares authorized		5,000,000
Common stock, par value \| $ / shares		$ 0.01
Preferred stock, par value \| $ / shares		$ 0.01
Share conversion ratio		5.65
Conversion of preferred stock to common stock		24,425,190
Options to purchase common stock		4,092,710
Weighted average exercise price \| $ / shares		$ 3.37
Subsequent Event [Member] \| Deciphera Pharmaceuticals, LLC [Member]
Subsequent Event [Line Items]
Share conversion ratio		5.65
Conversion of preferred stock to common stock		24,425,190
Options to purchase common stock		4,092,710
Weighted average exercise price \| $ / shares		$ 3.37
Subsequent Event [Member] \| IPO [Member]
Subsequent Event [Line Items]
Number of additional shares issued and sold		7,500,000
Public offering price of common stock \| $ / shares		$ 17.00
Proceeds from initial offering after deducting underwriting discounts and commissions \| $		$ 118.6
Subsequent Event [Member] \| IPO [Member] \| Deciphera Pharmaceuticals, LLC [Member]
Subsequent Event [Line Items]
Number of additional shares issued and sold		7,500,000
Public offering price of common stock \| $ / shares		$ 17.00
Proceeds from initial offering after deducting underwriting discounts and commissions \| $		$ 118.6
Subsequent Event [Member] \| Over-Allotment Option [Member]
Subsequent Event [Line Items]
Number of additional shares issued and sold	666,496
Public offering price of common stock \| $ / shares	$ 17.00
Proceeds from initial offering after deducting underwriting discounts and commissions \| $	$ 10.5
Subsequent Event [Member] \| Over-Allotment Option [Member] \| Deciphera Pharmaceuticals, LLC [Member]
Subsequent Event [Line Items]
Number of additional shares issued and sold	666,496
Public offering price of common stock \| $ / shares	$ 17.00
Proceeds from initial offering after deducting underwriting discounts and commissions \| $	$ 10.5

Nature of the Business and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended		12 Months Ended
	Oct. 04, 2017 USD ($) $ / shares shares	Oct. 02, 2017 USD ($) $ / shares shares	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Sep. 21, 2017 $ / shares	Dec. 31, 2015 USD ($)
IPO [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Additional offering price of common stock \| $ / shares								$ 17.00
Deciphera Pharmaceuticals, LLC [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Accumulated deficit			$ (175,957)		$ (175,957)		$ (145,585)
Cash and cash equivalents			82,149	$ 64,640	82,149	$ 64,640	57,461		$ 25,777
Recurring losses including net losses			$ 12,038	$ 6,099	$ 30,372	$ 17,383	$ 25,900
Subsequent Event [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Share conversion ratio		5.65
Subsequent Event [Member] \| IPO [Member]
Nature Of Business And Basis Of Presentation [Line Items]
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		$ 118,600
Subsequent Event [Member] \| 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
Subsequent Event [Member] \| Deciphera Pharmaceuticals, LLC [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Share conversion ratio		5.65
Subsequent Event [Member] \| Deciphera Pharmaceuticals, LLC [Member] \| IPO [Member]
Nature Of Business And Basis Of Presentation [Line Items]
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		$ 118,600
Subsequent Event [Member] \| Deciphera Pharmaceuticals, LLC [Member] \| 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 ($) $ in Thousands	Sep. 30, 2017	Aug. 01, 2017	Dec. 31, 2016	Sep. 30, 2016
Significant Accounting Policies [Line Items]
Common shares, shares outstanding	0	0
Deciphera Pharmaceuticals, LLC [Member]
Significant Accounting Policies [Line Items]
Deferred offering costs	$ 4,316		$ 104
Common shares, shares outstanding	0		0
Deciphera Pharmaceuticals, LLC [Member] \| No Par Value Common Stock [Member]
Significant Accounting Policies [Line Items]
Common shares, shares outstanding	0			0
Deciphera Pharmaceuticals, LLC [Member] \| Par Value Common Stock [Member]
Significant Accounting Policies [Line Items]
Common shares, shares outstanding	0			0
Deciphera Pharmaceuticals, LLC [Member] \| CRL Construction Loan [Member]
Significant Accounting Policies [Line Items]
Fair value of outstanding notes payable to related party	$ 1,200		$ 1,300

Fair Value of Financial Assets - Schedule of Financial Assets Measured at Fair Value on a Recurring Basis (Detail) - Deciphera Pharmaceuticals, LLC [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Cash equivalents:
Total Cash equivalents	$ 78,507	$ 53,180
Money Market Funds [Member]
Cash equivalents:
Total Cash equivalents	78,507	53,180
Level 2 [Member]
Cash equivalents:
Total Cash equivalents	78,507	53,180
Level 2 [Member] \| Money Market Funds [Member]
Cash equivalents:
Total Cash equivalents	$ 78,507	$ 53,180

Accrued Expenses - Schedule of Accrued Expenses (Detail) - Deciphera Pharmaceuticals, LLC [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Accrued Expenses [Line Items]
Accrued external research and development expenses	$ 3,869	$ 1,433
Accrued professional fees	1,659	240
Accrued payroll and related expenses	1,243	1,267
Accrued other	18	17
Accrued Expenses	$ 6,789	$ 2,957

Notes Payable to Related Party - Schedule of Notes Payable to Related Party (Detail) - Deciphera Pharmaceuticals, LLC [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Less: Current portion	$ (187)	$ (187)
Notes payable to related party, net of current portion	1,341	1,481
CRL Construction Loan [Member]
Related Party Transaction [Line Items]
Notes payable to related party	1,528	1,668
Less: Current portion	(187)	(187)
Notes payable to related party, net of current portion	$ 1,341	$ 1,481

Notes Payable to Related Party - Additional Information (Detail) - Deciphera Pharmaceuticals, LLC [Member] - CRL Construction Loan [Member] - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Related Party Transaction [Line Items]
Total interest expense			$ 100,000	$ 100,000
Maximum [Member]
Related Party Transaction [Line Items]
Total interest expense	$ 100,000	$ 100,000

Convertible Preferred Shares - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	9 Months Ended
	Oct. 02, 2017	May 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Subsequent Event [Member]
Redeemable Noncontrolling Interest [Line Items]
Conversion of preferred stock to common stock	24,425,190
Deciphera Pharmaceuticals, LLC [Member]
Redeemable Noncontrolling Interest [Line Items]
Proceeds from issuance of convertible preferred shares			$ 52,300	$ 55,324
Payments of convertible preferred share issuance costs			$ 429	$ 25
Number of convertible preferred shares authorized for issuance			4,455,039		3,632,711
Deciphera Pharmaceuticals, LLC [Member] \| Subsequent Event [Member]
Redeemable Noncontrolling Interest [Line Items]
Conversion of preferred stock to common stock	24,425,190
Series C Convertible Preferred Shares [Member] \| Deciphera Pharmaceuticals, LLC [Member]
Redeemable Noncontrolling Interest [Line Items]
Number of convertible preferred shares sold under share purchase agreement		690,333
Convertible preferred shares sold under share purchase agreement, price per share		$ 75.76
Proceeds from issuance of convertible preferred shares		$ 51,900
Payments of convertible preferred share issuance costs		$ 400
Number of convertible preferred shares authorized for issuance		822,328	822,328

Convertible Preferred Shares - Schedule of Preferred Shares (Detail) - Deciphera Pharmaceuticals, LLC [Member] - USD ($) $ in Thousands	Sep. 30, 2017	May 31, 2017	Dec. 31, 2016
Temporary Equity [Line Items]
Preferred Shares Authorized	4,455,039		3,632,711
Preferred Shares Issued	4,323,044		3,632,711
Preferred Shares Outstanding	4,323,044		3,632,711
Carrying Value	$ 244,538		$ 192,667
Liquidation Preference	$ 246,388		$ 194,088
Common Shares Issuable Upon Conversion	4,323,044		3,632,711
Series A Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized	2,057,750		2,057,750
Preferred Shares Issued	2,057,750		2,057,750
Preferred Shares Outstanding	2,057,750		2,057,750
Carrying Value	$ 102,556		$ 102,556
Liquidation Preference	$ 103,484		$ 103,484
Common Shares Issuable Upon Conversion	2,057,750		2,057,750
Series B-1 Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized	698,595		698,595
Preferred Shares Issued	698,595		698,595
Preferred Shares Outstanding	698,595		698,595
Carrying Value	$ 34,812		$ 34,812
Liquidation Preference	$ 35,279		$ 35,279
Common Shares Issuable Upon Conversion	698,595		698,595
Series B-2 Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized	876,366		876,366
Preferred Shares Issued	876,366		876,366
Preferred Shares Outstanding	876,366		876,366
Carrying Value	$ 55,299		$ 55,299
Liquidation Preference	$ 55,325		$ 55,325
Common Shares Issuable Upon Conversion	876,366		876,366
Series C Convertible Preferred Shares [Member]
Temporary Equity [Line Items]
Preferred Shares Authorized	822,328	822,328
Preferred Shares Issued	690,333
Preferred Shares Outstanding	690,333
Carrying Value	$ 51,871
Liquidation Preference	$ 52,300
Common Shares Issuable Upon Conversion	690,333

Common Shares - Additional Information (Detail) - shares	Sep. 30, 2017	Aug. 01, 2017	May 31, 2017	Apr. 30, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Common shares, authorized	1,000	1,000
Deciphera Pharmaceuticals, LLC [Member]
Class of Stock [Line Items]
Common shares, authorized	5,217,929				4,366,052
Deciphera Pharmaceuticals, LLC [Member] \| No Par Value Common Stock [Member]
Class of Stock [Line Items]
Common shares, authorized			5,217,929	4,366,052

Share-Based Awards - Additional Information (Detail) - Deciphera Pharmaceuticals, LLC [Member] - USD ($) $ in Millions	Sep. 30, 2017	May 31, 2017	May 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested share-based awards	$ 4.0
Unrecognized compensation cost related to unvested share-based awards, period for recognition	1 year 6 months
Common Stock [Member] \| 2015 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common shares reserved for issuance		762,890	641,066

Share-Based Awards - Classification of Share-Based Compensation Expense (Detail) - Deciphera Pharmaceuticals, LLC [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1,012	$ 462	$ 2,022	$ 950
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	459	189	797	382
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 553	$ 273	$ 1,225	$ 568

Net Loss per Share - Additional Information (Detail) - shares	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Aug. 01, 2017	Dec. 31, 2016
Earnings Per Share [Line Items]
Common shares, outstanding	0		0
Deciphera Pharmaceuticals, LLC [Member]
Earnings Per Share [Line Items]
Common shares, outstanding	0			0
Number of securities outstanding	2,989,673	2,101,319
No Par Value Common Stock [Member] \| Deciphera Pharmaceuticals, LLC [Member]
Earnings Per Share [Line Items]
Common shares, outstanding	0	0
Par Value Common Stock [Member] \| Deciphera Pharmaceuticals, LLC [Member]
Earnings Per Share [Line Items]
Common shares, outstanding	0	0
Series A Convertible Preferred Stock [Member] \| Deciphera Pharmaceuticals, LLC [Member]
Earnings Per Share [Line Items]
Number of securities outstanding	0	0

Net Loss per Share - Summary of Basic and Diluted Net Loss Per Share Attributable to Series A Convertible Preferred Shareholders (Detail) - Series A Convertible Preferred Stock [Member] - Deciphera Pharmaceuticals, LLC [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net loss attributable to Series A convertible preferred shareholders	$ (12,038)	$ (6,099)	$ (30,372)	$ (17,383)
Denominator:
Weighted average Series A convertible preferred shares outstanding-basic and diluted	2,057,750	2,057,750	2,057,750	2,057,750
Net loss per share attributable to Series A convertible preferred shareholders-basic and diluted	$ (5.85)	$ (2.96)	$ (14.76)	$ (8.45)

Net Loss per Share - Summary of Potential Dilutive Securities (Detail) - Deciphera Pharmaceuticals, LLC [Member] - shares	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	2,989,673	2,101,319
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	601,556	443,849
Stock Appreciation Rights [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	122,823	82,509
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	1,574,961	1,574,961
Series C 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	690,333

Commitments and Contingencies - Additional Information (Detail) - Deciphera Pharmaceuticals, LLC [Member]			1 Months Ended	3 Months Ended		9 Months Ended
	Dec. 31, 2013 USD ($)	Dec. 30, 2013 USD ($) award	Aug. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) Lease	Sep. 30, 2016 USD ($)
Other Commitments [Line Items]
Rent expense				$ 100,000	$ 100,000	$ 400,000	$ 300,000
KBA Grants [Member]
Other Commitments [Line Items]
Number of awards grants \| award		2
Amount of grants awarded	$ 0	$ 2,000,000
Sublease Agreement for Office Space in Waltham, Massachusetts [Member]
Other Commitments [Line Items]
Sublease term						3 years
Sublease expiration date						Sep. 30, 2019
Lease Agreement for Office and Laboratory Space in Lawrence, Kansas [Member]
Other Commitments [Line Items]
Lease term						5 years
Number of lease agreement \| Lease						2
Operating lease expiry date						Dec. 31, 2020
Lease Agreement for Additional Office Space in Lawrence, Kansas [Member]
Other Commitments [Line Items]
Operating lease expiry date			Dec. 31, 2020
Lease Agreement for Additional Office Space in Lawrence, Kansas [Member] \| Maximum [Member]
Other Commitments [Line Items]
Annual payment on lease			$ 100,000

Commitments and Contingencies - Summary of Future Minimum Lease Payments under Operating Leases (Detail) - Deciphera Pharmaceuticals, LLC [Member] $ in Thousands	Sep. 30, 2017 USD ($)
Operating Leased Assets [Line Items]
Remainder of 2017	$ 154
2018	617
2019	519
2020	315
Future minimum lease payments due	$ 1,605

401(k) Savings Plan - Additional Information (Detail) - Clinical Reference Laboratory, Inc. [Member] - Deciphera Pharmaceuticals, LLC [Member] - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
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	$ 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) - Deciphera Pharmaceuticals, LLC [Member] - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Research and development expense	$ 9,751,000	$ 4,717,000	$ 23,856,000	$ 13,626,000
Clinical Reference Laboratory, Inc. [Member]
Related Party Transaction [Line Items]
Research and development expense	200,000	100,000	300,000	100,000
Laboratory services	200,000		200,000
Employees contributions under 401(K) plan	100,000		400,000	200,000
Clinical Reference Laboratory, Inc. [Member] \| Loan and Security Agreement [Member]
Related Party Transaction [Line Items]
Aggregate borrowings	2,800,000		2,800,000
Interest expense on borrowings			100,000	100,000
Debt instrument principal and interest payment			200,000	$ 200,000
Principal amount owed under loan agreement	1,500,000		$ 1,500,000		$ 1,700,000
Clinical Reference Laboratory, Inc. [Member] \| Maximum [Member]
Related Party Transaction [Line Items]
Laboratory services					$ 100,000
Employees contributions under 401(K) plan		100,000
Clinical Reference Laboratory, Inc. [Member] \| Maximum [Member] \| Loan and Security Agreement [Member]
Related Party Transaction [Line Items]
Interest expense on borrowings	$ 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%		31.00%
Clinical Reference Laboratory, Inc. [Member] \| Brightstar [Member] \| Minimum [Member]
Related Party Transaction [Line Items]
Percentage of preferred shares			5.00%