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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2018	Jul. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q2
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		37,657,201

Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 346,527	$ 196,754
Prepaid expenses and other current assets	2,221	1,428
Total current assets	348,748	198,182
Long-term investments-restricted	1,069
Property and equipment, net	18,264	838
Other assets	75	75
Total assets	368,156	199,095
Current liabilities:
Accounts payable	6,938	4,395
Accrued expenses and other current liabilities	11,790	9,233
Notes payable to related party	187	187
Total current liabilities	18,915	13,815
Notes payable to related party, net of current portion	1,201	1,294
Lease liability, net of current portion	16,896
Other long-term liabilities	47	13
Total liabilities	37,059	15,122
Commitments and contingencies (Note 8)
Stockholders' equity:
Preferred stock value
Common stock value	376	326
Additional paid-in capital	569,710	379,516
Accumulated deficit	(238,989)	(195,869)
Total stockholders' equity	331,097	183,973
Total liabilities and stockholders' equity	$ 368,156	$ 199,095

Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	37,633,450	32,591,686
Common stock, shares outstanding	37,633,450	32,591,686

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenue	$ 0	$ 0	$ 0	$ 0
Operating expenses:
Research and development	17,976	8,446	34,901	14,105
General and administrative	4,453	2,244	9,479	4,311
Total operating expenses	22,429	10,690	44,380	18,416
Loss from operations	(22,429)	(10,690)	(44,380)	(18,416)
Other income (expense):
Interest expense	(21)	(24)	(43)	(49)
Interest and other income, net	760	89	1,303	131
Total other income (expense), net	739	65	1,260	82
Net loss and comprehensive loss	$ (21,690)	$ (10,625)	$ (43,120)	$ (18,334)
Net loss per share-basic and diluted	$ (0.65)	$ (0.91)	$ (1.30)	$ (1.58)
Weighted average common shares outstanding-basic and diluted	33,567,314	11,626,287	33,083,383	11,626,287

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net loss	$ (43,120)	$ (18,334)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	4,269	1,010
Depreciation and amortization expense	130	62
Loss on disposal of property and equipment		6
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(793)	211
Accounts payable	2,225	446
Accrued expenses and other current liabilities	2,272	1,500
Other long-term liabilities	34	16
Net cash used in operating activities	(34,983)	(15,083)
Cash flows from investing activities:
Purchases of property and equipment	(606)	(74)
Increase in restricted investments	(1,069)
Net cash used in investing activities	(1,675)	(74)
Cash flows from financing activities:
Proceeds from follow-on public offering, net of underwriting discounts and commissions	185,932
Proceeds from issuance of convertible preferred shares		52,300
Repayment of notes payable to related party	(93)	(93)
Payments of follow-on public offering costs	(125)
Payments of convertible preferred share issuance costs		(187)
Payments of initial public offering costs		(332)
Proceeds from exercise of stock options	717
Net cash provided by financing activities	186,431	51,688
Net increase in cash and cash equivalents	149,773	36,531
Cash and cash equivalents at beginning of period	196,754	57,461
Cash and cash equivalents at end of period	346,527	93,992
Cash paid for interest	43	49
Amounts capitalized under build-to-suit lease transaction	17,028
Offering costs included in accounts payable or accrued expenses	$ 549	$ 1,699

Nature of the Business and Basis of Presentation	6 Months Ended
Nature of the Business and Basis of Presentation	Jun. 30, 2018
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 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”). 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. On June 11, 2018, the Company issued and sold 4,300,000 shares of its common stock in a follow-on public offering at a public offering price of $40.00 per share, resulting in net proceeds of $161.0 million after deducting underwriting discounts and commissions and other offering expenses. On June 20, 2018, the Company issued and sold an additional 645,000 shares of its common stock at the offering price of $40.00 per share, pursuant to the underwriters’ full exercise of their option to purchase additional shares of common stock, resulting in additional net proceeds of $24.3 million after deducting underwriting discounts and commissions. 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 $43.1 million and $50.3 million for the six months ended June 30, 2018 and the year ended December 31, 2017, respectively. As of June 30, 2018, the Company had an accumulated deficit of $239.0 million. The Company expects to continue to generate operating losses in the foreseeable future. The Company expects that its cash and cash equivalents of $346.5 million as of June 30, 2018 will 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. These consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated. These 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

6 Months Ended

Jun. 30, 2018

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, the valuation of common stock prior to the Company’s IPO, 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.

Unaudited Interim Financial Information

The consolidated balance sheet at December 31, 2017 was derived from audited financial statements, but does not include all disclosures required by U.S. GAAP. The accompanying unaudited consolidated financial statements as of June 30, 2018 and for the three and six months ended June 30, 2018 and 2017 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 consolidated financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017, on file with the SEC. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary for a fair statement of the Company’s consolidated financial position as of June 30, 2018 and consolidated results of operations for the three and six months ended June 30, 2018 and 2017 and consolidated cash flows for the six months ended June 30, 2018 and 2017 have been made. The consolidated results of operations for the six months ended June 30, 2018 are not necessarily indicative of the results of operations that may be expected for the year ending December 31, 2018.

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 June 30, 2018 and December 31, 2017 approximated $1.2 million. 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

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 three and six months ended June 30, 2018. Diluted net income (loss) per share 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 stock, as determined using the treasury stock method.

The Company did not have any common shares outstanding during the three and six months ended June 30, 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. Share amounts for periods prior to the 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 (see Note 1).

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 reported a net loss for the three and six months ended June 30, 2018 and 2017.

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:


	As of June 30,
	2018		2017
Series B convertible preferred shares (as converted to common shares)		—		8,898,527
Series C convertible preferred shares (as converted to common shares)		—		3,900,381
Options to purchase common stock		5,583,058		4,108,486

		5,583,058		16,907,394

Recently Adopted 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-cashconsideration, 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 did not 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 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 adoption of ASU 2017-09 did not have an impact on the Company’s financial position, results of operations or cash flows.

Recently Issued Accounting Pronouncements

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 and cash flows.

In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718)—Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”). This ASU is intended to simplify aspects of share-based compensation issued to non-employees by making the guidance consistent with the accounting for employee share-based compensation. 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 but no earlier than the Company’s adoption of ASU 2014-09. The Company is currently evaluating the impact that the adoption of ASU 2018-07will have on its financial position, results of operations and cash flows.

Fair Value of Financial Assets

6 Months Ended

Jun. 30, 2018

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 June 30, 2018 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	264,988	$	—	$	264,988

Total	$	—	$	264,988	$	—	$	264,988


	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

The table above as of June 30, 2018 excludes a certificate of deposit in the amount of $1.1 million that the Company held to secure a letter of credit associated with a lease (see Note 8).

- 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 and Other Current Liabilities

6 Months Ended

Jun. 30, 2018

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

4. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):


	June 30, 2018		December 31, 2017
Accrued external research and development expenses	$	8,170	$	6,625
Accrued payroll and related expenses		2,888		2,233
Accrued professional fees		582		353
Accrued other		150		22

	$	11,790	$	9,233

Income Taxes	6 Months Ended
Income Taxes	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	5. 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 has not recorded a tax benefit for its net losses in the three and six months ended June 30, 2018 or since its Conversion as the Company has provided a valuation allowance for the full amount of its net deferred tax assets because it was more likely than not that any future benefit from deductible temporary differences and net operating loss and tax credit carryforwards would not be realized. The Company had gross deferred tax assets of $10.8 million at December 31, 2017. 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 at December 31, 2017 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 for the year ended December 31, 2017. 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 at June 30, 2018. The Company has not recorded any amounts for unrecognized tax benefits as of June 30, 2018 or December 31, 2017. As of June 30, 2018 and December 31, 2017, the Company had no accrued interest or tax penalties recorded. The Company’s income tax return reporting periods since October 2, 2017 to present are open to income tax audit examination by the federal and state tax authorities.

Notes Payable to Related Party

6 Months Ended

Jun. 30, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Notes Payable to Related Party

6. Notes Payable to Related Party

Notes payable to related party as of June 30, 2018 and December 31, 2017 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 10), as follows (in thousands):


	June 30, 2018			December 31, 2017
Notes payable to related party	$	1,388		$	1,481
Less: Current portion		(187	)		(187	)

Notes payable to related party, net of current portion	$	1,201		$	1,294

Total interest expense was less than $0.1 million for each of the three and six months ended June 30, 2018 and 2017.

Stock-Based Awards

6 Months Ended

Jun. 30, 2018

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

Stock-Based Awards

7. Stock-Based Awards

The Company grants stock-based awards under its 2017 Stock Option and Incentive Plan (the “2017 Plan”) and is authorized to issue common stock under its 2017 Employee Stock Purchase Plan (“ESPP”). The Company also has outstanding stock options under its 2015 Equity Incentive Plan but is no longer granting awards under this plan. As of June 30, 2018, 2,372,386 shares of common stock were available for issuance under the 2017 Plan. As of June 30, 2018, 632,666 shares of common stock were available for issuance to participating employees under the ESPP.

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


	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Research and development expenses	$	983	$	202	$	1,945	$	338
General and administrative expenses		1,249		392		2,324		672

	$	2,232	$	594	$	4,269	$	1,010

As of June 30, 2018, total unrecognized compensation cost related to the unvested share-based awards was $25.1 million, which is expected to be recognized over a weighted average of 2.2 years.

Commitments and Contingencies

6 Months Ended

Jun. 30, 2018

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

8. 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.

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 $0.2 million during each of the three months ended June 30, 2018 and 2017 and $0.4 million and $0.3 million during the six months ended June 30, 2018 and 2017, respectively.

The following table summarizes the future minimum lease payments due under the operating leases as of June 30, 2018 (in thousands):


Remainder of 2018	$	338
2019		578
2020		374

	$	1,290

Build-to-suit lease

In May 2018, the Company entered into a lease for office space in Waltham, Massachusetts. The lease term is expected to commence on May 1, 2019 and expires 10 years and 7 months from the commencement date, unless terminated earlier in accordance with the terms of the lease. The Company is entitled to two five-year options to extend. The initial annual base rent is approximately $2.0 million and will increase annually. The Company is obligated to pay its portion of real estate taxes and costs related to the premises, including costs of operations, maintenance, repair, replacement and management of the new leased premises. The Company is required to maintain a cash balance of $1.1 million to secure a letter of credit associated with the lease. This amount was classified as long-term investment—restricted in the consolidated balance sheet as of June 30, 2018.

The Company is not the legal owner of the leased space. However, in accordance with ASC 840, Leases, the Company is deemed to be the owner of the leased space during the construction period because of certain provisions within the lease agreement. As a result, as of June 30, 2018, the Company capitalized approximately $17.0 million (equal to the estimated cost of its leased portion of the premises) as construction-in-progress within property and equipment and recorded a corresponding build-to-suit facility lease financing obligation. As of June 30, 2018, the current portion of the lease financing obligation of $0.1 million was classified within accrued expenses and other current liabilities and the remaining $16.9 million was classified as a long-term lease liability, net of current portion, on its consolidated balance sheet. The construction is expected to be completed in the second quarter of 2019.

As of June 30, 2018, minimum commitments under this lease are as follows (in thousands):


Year Ending December 31,
2019	$	170
2020		2,039
2021		2,084
2022		2,128
2023		2,172
Thereafter		13,756

	$	22,349

KBA Grants

Prior to 2014, the Company received funding from two research and development grants from the KBA totaling $2.0 million and 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 June 30, 2018 or December 31, 2017.

401(k) Savings Plan	6 Months Ended
401(k) Savings Plan	Jun. 30, 2018
Retirement Benefits [Abstract]
401(k) Savings Plan	9. 401(k) Savings Plan Effective January 1, 2018, the Company adopted the Deciphera Pharmaceuticals 401(k) Plan (the “2018 401(k) Plan”), a defined contribution plan under Section 401(k) of the Internal Revenue Code, whereby the Company provides matching contributions of 100% of each employee’s contribution up to a maximum matching contribution of 3% of the employee’s eligible compensation and at a rate of 50% of each employee’s contribution in excess of 3% up to a maximum of 5% of the employee’s eligible compensation. Prior to January 1, 2018, the Company had a defined contribution plan that was managed by CRL, a related party (the “CRL 401(k) Plan”). Effective January 1, 2018, employees’ and former employees’ accounts were transitioned from the CRL 401(k) Plan to the 2018 401(k) Plan. Under the CRL 401(k) Plan, the Company provided matching contributions up to 50% of actual dollars contributed, not to exceed a maximum of 6% of gross wages, subject to certain time-based vesting requirements. Total employer matching contributions related to these plans were $0.1 million and less than $0.1 million, respectively, for the three months ended June 30, 2018 and 2017 and $0.2 million and $0.1 million, respectively, for the six months ended June 30, 2018 and 2017.

Related Parties	6 Months Ended
Related Parties	Jun. 30, 2018
Related Party Transactions [Abstract]
Related Parties	10. 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 three months ended June 30, 2018 and 2017, the Company recorded less than $0.1 million of interest expense related to this loan. For each of the three months ended June 30, 2018 and 2017, the Company made $0.1 million in principal and interest payments under the loan. For each of the six months ended June 30, 2018 and 2017, the Company recorded less than $0.1 million of interest expense related to this loan. For each of the six months ended June 30, 2018 and 2017, the Company made $0.1 million in principal and interest payments under the loan. As of June 30, 2018 and December 31, 2017, principal amounts owed under the loan agreement totaled $1.4 million and $1.5 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 three months ended June 30, 2018 and 2017, the Company recorded $0.3 million and $0.1 million, respectively, of research and development expense incurred under this agreement, of which $0.3 million and less than $0.1 million, respectively, was paid to CRL during each those same periods. For the six months ended June 30, 2018 and 2017, the Company recorded $0.4 million and $0.2 million, respectively, of research and development expense incurred under this agreement, of which $0.4 million and less than $0.1 million, respectively, was paid to CRL during each those same periods. As of June 30, 2018 and December 31, 2017, total amounts owed to CRL for laboratory services were $0.2 million and $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. Effective January 1, 2018, the Company adopted the 2018 401(k) Plan to which employees’ and former employees’ accounts were transitioned from the CRL 401(k) Plan. For the three and six months ended June 30, 2018, no contributions were made by employees of the Company to the CRL 401(k) Plan. For the three and six months ended June 30, 2017, the total amount of contributions made by employees of the Company under the CRL 401(k) Plan was $0.2 million and $0.4 million, respectively.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2018

Accounting Policies [Abstract]

Use of Estimates

Use of Estimates

Unaudited Interim Financial Information

Unaudited Interim Financial Information

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


	As of June 30,
	2018		2017
Series B convertible preferred shares (as converted to common shares)		—		8,898,527
Series C convertible preferred shares (as converted to common shares)		—		3,900,381
Options to purchase common stock		5,583,058		4,108,486

		5,583,058		16,907,394

Recently Adopted and Recently Issued Accounting Pronouncements

Recently Adopted 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 did not 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.

Recently Issued Accounting Pronouncements

In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718)—Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”), that aligns the accounting for share-based payment awards issued to employees and nonemployees, particularly with regard to the measurement date and the impact of performance conditions. 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 2018-07 will have on its financial position, results of operations and cash flows.

Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2018

Accounting Policies [Abstract]

Summary of Potential Dilutive Securities


	As of June 30,
	2018		2017
Series B convertible preferred shares (as converted to common shares)		—		8,898,527
Series C convertible preferred shares (as converted to common shares)		—		3,900,381
Options to purchase common stock		5,583,058		4,108,486

		5,583,058		16,907,394

Fair Value of Financial Assets (Tables)

6 Months Ended

Jun. 30, 2018

Fair Value Disclosures [Abstract]

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


	Fair Value Measurements at June 30, 2018 Using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	264,988	$	—	$	264,988

Total	$	—	$	264,988	$	—	$	264,988


	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

Accrued Expenses and Other Current Liabilities (Tables)

6 Months Ended

Jun. 30, 2018

Payables and Accruals [Abstract]

Schedule of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following (in thousands):


	June 30, 2018		December 31, 2017
Accrued external research and development expenses	$	8,170	$	6,625
Accrued payroll and related expenses		2,888		2,233
Accrued professional fees		582		353
Accrued other		150		22

	$	11,790	$	9,233

Notes Payable to Related Party (Tables)

6 Months Ended

Jun. 30, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Notes Payable to Related Party


	June 30, 2018			December 31, 2017
Notes payable to related party	$	1,388		$	1,481
Less: Current portion		(187	)		(187	)

Notes payable to related party, net of current portion	$	1,201		$	1,294

Stock-Based Awards (Tables)

6 Months Ended

Jun. 30, 2018

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

Classification of Stock-Based Compensation Expense

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


	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Research and development expenses	$	983	$	202	$	1,945	$	338
General and administrative expenses		1,249		392		2,324		672

	$	2,232	$	594	$	4,269	$	1,010

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2018

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 June 30, 2018 (in thousands):


Remainder of 2018	$	338
2019		578
2020		374

	$	1,290

Summary of Future Minimum Lease Payments

As of June 30, 2018, minimum commitments under this lease are as follows (in thousands):


Year Ending December 31,
2019	$	170
2020		2,039
2021		2,084
2022		2,128
2023		2,172
Thereafter		13,756

	$	22,349

Nature of the Business and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands					3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 20, 2018 USD ($) $ / shares shares	Jun. 11, 2018 USD ($) $ / shares shares	Oct. 04, 2017 USD ($) $ / shares shares	Oct. 02, 2017 USD ($) $ / shares shares	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Nature Of Business And Basis Of Presentation [Line Items]
Share conversion ratio				5.65
Proceeds from additional offering of shares							$ 185,932
Accumulated deficit					$ (238,989)		(238,989)		$ (195,869)
Cash and cash equivalents					346,527		346,527		196,754
Recurring losses including net losses					$ 21,690	$ 10,625	$ 43,120	$ 18,334	$ 50,300
Common Stock [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Net proceeds from initial public offering	$ 24,300	$ 161,000
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
Net proceeds from initial public offering				$ 114,100
IPO [Member] \| Common Stock [Member]
Nature Of Business And Basis Of Presentation [Line Items]
Number of additional shares issued and sold \| shares	645,000	4,300,000
Additional offering price of common stock \| $ / shares	$ 40.00	$ 40.00
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 Millions	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Significant Accounting Policies [Line Items]
Common stock, shares outstanding	37,633,450	32,591,686
No Par Value Common Stock [Member]
Significant Accounting Policies [Line Items]
Common stock, shares outstanding			0
CRL Construction Loan [Member]
Significant Accounting Policies [Line Items]
Fair value of outstanding notes payable to related party	$ 1.2	$ 1.2

Summary of Significant Accounting Policies - Summary of Potential Dilutive Securities (Detail) - shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potential dilutive securities excluded from computation of diluted net loss per common share	5,583,058	16,907,394
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
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		3,900,381
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	5,583,058	4,108,486

Fair Value of Financial Assets - Schedule of Financial Assets Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Cash equivalents:
Total Cash equivalents	$ 264,988	$ 191,950
Money Market Funds [Member]
Cash equivalents:
Total Cash equivalents	264,988	191,950
Level 2 [Member]
Cash equivalents:
Total Cash equivalents	264,988	191,950
Level 2 [Member] \| Money Market Funds [Member]
Cash equivalents:
Total Cash equivalents	$ 264,988	$ 191,950

Fair Value of Financial Assets - Additional Information (Detail) $ in Millions	Jun. 30, 2018 USD ($)
Letter of Credit [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Certificate of deposit	$ 1.1

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounts Payable and Accrued Liabilities [Abstract]
Accrued external research and development expenses	$ 8,170	$ 6,625
Accrued payroll and related expenses	2,888	2,233
Accrued professional fees	582	353
Accrued other	150	22
Accrued Expenses and Other Current Liabilities	$ 11,790	$ 9,233

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Current provision for income taxes	$ 0	$ 0
Total gross deferred tax assets			$ 10,800,000
Federal statutory income tax rate		21.00%	35.00%
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
Provisional income tax expense (benefit)			0
Unrecognized tax benefits	0	$ 0	0
Accrued interest recorded	$ 0	0	0
Tax penalties recorded		$ 0	$ 0

Notes Payable to Related Party - Schedule of Notes Payable to Related Party (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Less: Current portion	$ (187)	$ (187)
Notes payable to related party, net of current portion	1,201	1,294
CRL Construction Loan [Member]
Related Party Transaction [Line Items]
Notes payable to related party	1,388	1,481
Less: Current portion	(187)	(187)
Notes payable to related party, net of current portion	$ 1,201	$ 1,294

Notes Payable to Related Party - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
CRL Construction Loan [Member] \| Maximum [Member]
Related Party Transaction [Line Items]
Total interest expense	$ 100,000	$ 100,000	$ 100,000	$ 100,000

Stock-Based Awards - Additional Information (Detail) $ in Millions	Jun. 30, 2018 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to unvested share-based awards \| $	$ 25.1
Unrecognized compensation cost related to unvested share-based awards, period for recognition	2 years 2 months 12 days
2017 Stock Option and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance	2,372,386
Employee Stock Purchase Plan (ESPP) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance	632,666

Stock-Based Awards - Classification of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 2,232	$ 594	$ 4,269	$ 1,010
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	983	202	1,945	338
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1,249	$ 392	$ 2,324	$ 672

Commitments and Contingencies - Additional Information (Detail)		1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2013 USD ($) award	Dec. 31, 2015 Lease	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) Lease	Dec. 31, 2013 USD ($)
Other Commitments [Line Items]
Rent expense			$ 200,000	$ 200,000	$ 400,000	$ 300,000
Lease term			10 years 7 months		10 years 7 months
Lease commencement period					2019-05
Lessee, finance lease, existence of option to extend					true
Lessee, finance lease, existence of option to terminate					true
Options to extend terms of the lease					Two five-year
Initial annual base rent					$ 2,000,000
Company capitalized construction-in-progress lease financing obligation					17,028,000
Current portion of the lease financing obligation			$ 100,000		100,000
Long-term lease liability, net of current portion			16,896,000		16,896,000
Cash [Member] \| Letter of Credit [Member]
Other Commitments [Line Items]
Cash balance to secure letter of credit associated with lease			$ 1,100,000		$ 1,100,000
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	Jun. 30, 2018 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Remainder of 2018	$ 338
2019	578
2020	374
Future minimum lease payments due	$ 1,290

Commitments and Contingencies - Future Minimum Lease Payments Commitments Lease (Detail) $ in Thousands	Jun. 30, 2018 USD ($)
Contractual Obligation, Fiscal Year Maturity Schedule [Abstract]
2019	$ 170
2020	2,039
2021	2,084
2022	2,128
2023	2,172
Thereafter	13,756
Total	$ 22,349

401(k) Savings Plan - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Contribution Plan Disclosure [Line Items]
Percentage of matching contribution to plan			50.00%
Clinical Reference Laboratory, Inc. [Member]
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan description			Effective January 1, 2018, the Company adopted the Deciphera Pharmaceuticals 401(k) plan (the “2018 401(k) Plan”), a defined contribution plan under Section 401(k) of the Internal Revenue Code, whereby the Company provides matching contributions of 100% of each employee’s contribution up to a maximum matching contribution of 3% of the employee’s eligible compensation and at a rate of 50% of each employee’s contribution in excess of 3% up to a maximum of 5% of the employee’s eligible compensation.
Percentage of matching contribution to plan			100.00%
Matching contributions to the plan by employer	$ 100,000		$ 200,000	$ 100,000
Maximum [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of salary for matching contribution per employee on time-based vesting			5.00%
Maximum [Member] \| Clinical Reference Laboratory, Inc. [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of matching contribution to plan			50.00%
Employee earnings subject to employer match			3.00%
Percentage of salary for matching contribution per employee			6.00%
Matching contributions to the plan by employer		$ 100,000
Minimum [Member]
Defined Contribution Plan Disclosure [Line Items]
Percentage of salary for matching contribution per employee on time-based vesting			3.00%

Related Parties - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Research and development expense	$ 17,976,000	$ 8,446,000	$ 34,901,000	$ 14,105,000
Clinical Reference Laboratory, Inc. [Member]
Related Party Transaction [Line Items]
Payments for research and development expense	300,000		400,000
Laboratory services	200,000		200,000		$ 100,000
Clinical Reference Laboratory, Inc. [Member] \| Loan and Security Agreement [Member]
Related Party Transaction [Line Items]
Aggregate borrowings	2,800,000		2,800,000
Debt instrument principal and interest payment	100,000	100,000	100,000	100,000
Principal amount owed under loan agreement	1,400,000		1,400,000		$ 1,500,000
Clinical Reference Laboratory, Inc. [Member] \| Service Agreement [Member]
Related Party Transaction [Line Items]
Research and development expense	300,000	100,000	400,000	200,000
Employees contributions under 401(K) plan		200,000		400,000
Clinical Reference Laboratory, Inc. [Member] \| Maximum [Member]
Related Party Transaction [Line Items]
Payments for research and development expense		100,000		100,000
Clinical Reference Laboratory, Inc. [Member] \| Maximum [Member] \| Clinical Reference Laboratory, Inc. [Member]
Related Party Transaction [Line Items]
Interest expense on borrowings	$ 100,000	$ 100,000	$ 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 common stock holding			5.00%