Array 10-Q 6 Feb 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Dec. 31, 2017	Jan. 29, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	ARRAY BIOPHARMA INC
Entity Central Index Key	1,100,412
Current Fiscal Year End Date	--06-30
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		207,636,672

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Jun. 30, 2017
Current assets
Cash and cash equivalents	$ 65,051	$ 125,933
Marketable securities	354,221	108,390
Accounts receivable	29,970	31,279
Prepaid expenses and other current assets	4,614	4,575
Total current assets	453,856	270,177
Long-term assets
Marketable securities	1,045	732
Property and equipment, net	7,206	8,132
Other long-term assets	738	104
Total long-term assets	8,989	8,968
Total assets	462,845	279,145
Current liabilities
Accounts payable	10,996	8,636
Accrued outsourcing costs	27,301	31,388
Accrued compensation and benefits	6,772	10,172
Other accrued expenses	1,754	1,575
Deferred rent	671	624
Notes payable at fair value	12,700	0
Deferred revenue	13,419	17,156
Total current liabilities	73,613	69,551
Long-term liabilities
Deferred rent	5,766	5,714
Deferred revenue	46,821	57,325
Long-term debt, net	93,264	121,305
Notes payable at fair value	0	12,600
Other long-term liabilities	1,199	923
Total long-term liabilities	147,050	197,867
Total liabilities	220,663	267,418
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.001 par value; 10,000,000 shares authorized, no shares issued and outstanding	0	0
Common stock, $0.001 par value; 280,000,000 shares authorized, 207,458,268 and 171,307,715 shares issued and outstanding as of December 31, 2017 and June 30, 2017, respectively	207	171
Additional paid-in capital	1,233,359	930,293
Accumulated other comprehensive loss	(676)	(76)
Accumulated deficit	(990,708)	(918,661)
Total stockholders' equity	242,182	11,727
Total liabilities and stockholders' equity	$ 462,845	$ 279,145

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Jun. 30, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	280,000,000	280,000,000
Common stock, issued (in shares)	207,458,268	171,307,715
Common stock, outstanding (in shares)	207,458,268	171,307,715

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Revenue
Reimbursement revenue	$ 22,395	$ 27,948	$ 40,587	$ 59,269
Collaboration and other revenue	8,508	6,030	16,516	12,319
License and milestone revenue	11,315	10,545	14,861	12,206
Total revenue	42,218	44,523	71,964	83,794
Operating expenses
Cost of partnered programs	13,716	9,026	25,475	17,871
Research and development for proprietary programs	42,613	46,469	84,058	93,032
General and administrative	11,607	8,834	23,655	16,696
Total operating expenses	67,936	64,329	133,188	127,599
Loss from operations	(25,718)	(19,806)	(61,224)	(43,805)
Other income (expense)
Loss on extinguishment and conversion of Notes	(6,457)	0	(6,457)	0
Impairment loss related to cost method investment	0	0	0	(1,500)
Change in fair value of notes payable	(300)	(600)	(100)	(800)
Interest income	1,255	212	1,780	282
Interest expense	(2,833)	(3,107)	(6,046)	(6,086)
Total other income (expense), net	(8,335)	(3,495)	(10,823)	(8,104)
Net loss	(34,053)	(23,301)	(72,047)	(51,909)
Change in unrealized loss on marketable securities	(634)	(61)	(600)	(57)
Comprehensive loss	$ (34,687)	$ (23,362)	$ (72,647)	$ (51,966)
Weighted average shares outstanding – basic (in shares)	199,852	168,127	187,312	156,613
Weighted average shares outstanding – diluted (in shares)	199,852	168,127	187,312	156,613
Net loss per share – basic (in dollars per share)	$ (0.17)	$ (0.14)	$ (0.38)	$ (0.33)
Net loss per share – diluted (in dollars per share)	$ (0.17)	$ (0.14)	$ (0.38)	$ (0.33)

Condensed Consolidated Stateme5

Condensed Consolidated Statement of Stockholders' Equity - 6 months ended Dec. 31, 2017 - USD ($) shares in Thousands, $ in Thousands	Total	Market offering	Follow on offering	Common Stock	Common StockMarket offering	Common StockFollow on offering	Additional Paid-in Capital	Additional Paid-in CapitalMarket offering	Additional Paid-in CapitalFollow on offering	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance (in shares) at Jun. 30, 2017				171,308
Balance at Jun. 30, 2017	$ 11,727			$ 171			$ 930,293			$ (76)	$ (918,661)
Increase (Decrease) in Stockholders' Equity
Shares issued for cash under employee share plans, net (in shares)				2,887
Shares issued for cash under employee share plans	14,603			$ 2			14,601
Employee share-based compensation expense	8,819						8,819
Issuance of common stock, net of offering costs (in shares)					324	24,070
Issuance of common stock, net of offering costs		$ 2,830	$ 243,018		$ 1	$ 24		$ 2,829	$ 242,994
Extinguishment of 2020 notes (in shares)				7,956
Extinguishment of 2020 Notes	(15,697)			$ 8			(15,705)
Conversion of 2020 notes (in shares)				913
Conversion of 2020 Notes	5,419			$ 1			5,418
Issuance of 2024 Notes	44,110						44,110
Change in unrealized loss on marketable securities	(600)									(600)
Net loss	(72,047)										(72,047)
Balance (in shares) at Dec. 31, 2017				207,458
Balance at Dec. 31, 2017	$ 242,182			$ 207			$ 1,233,359			$ (676)	$ (990,708)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net loss	$ (72,047)	$ (51,909)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	1,138	971
Non-cash interest expense	3,640	3,439
Share-based compensation expense	8,819	4,008
Loss on extinguishment and conversion of Notes	6,457	0
Impairment loss related to cost method investment	0	1,500
Financing fees on notes payable	0	240
Change in fair value of notes payable	100	800
Changes in operating assets and liabilities:
Accounts receivable	1,309	(3,820)
Prepaid expenses and other assets	(673)	3,993
Accounts payable and other accrued expenses	2,539	(3,594)
Accrued outsourcing costs	(4,087)	9,913
Accrued compensation and benefits	(3,400)	(3,244)
Deferred rent	99	493
Deferred revenue	(14,241)	(5,163)
Other long-term liabilities	171	163
Net cash used in operating activities	(70,176)	(42,210)
Cash flows from investing activities
Purchases of property and equipment	(212)	(1,733)
Purchases of marketable securities	(338,060)	(197,516)
Proceeds from sales and maturities of marketable securities	91,421	99,494
Net cash used in investing activities	(246,851)	(99,755)
Cash flows from financing activities
Net proceeds from notes payable at fair value	0	9,760
Proceeds from employee stock purchases and options exercised	14,603	1,509
Proceeds from Silicon Valley Bank term loan	0	15,000
Repayment of Comerica term loan principal	0	(14,550)
Payment for debt issuance costs	(4,306)	0
Net cash provided by financing activities	256,145	148,152
Net increase (decrease) in cash and cash equivalents	(60,882)	6,187
Cash and cash equivalents at beginning of period	125,933	56,598
Cash and cash equivalents at end of period	65,051	62,785
Supplemental disclosure of cash flow information
Cash paid for interest	2,161	2,243
Change in unrealized loss on marketable securities	(600)	(57)
Follow on offering
Cash flows from financing activities
Net proceeds from the issuance of common stock	258,750	132,250
Offering costs for issuance of common stock	(15,732)	(8,058)
Market offering
Cash flows from financing activities
Net proceeds from the issuance of common stock	2,917	12,572
Offering costs for issuance of common stock	$ (87)	$ (331)

OVERVIEW, BASIS OF PRESENTATION

OVERVIEW, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	6 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
OVERVIEW, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	OVERVIEW, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Organization Array BioPharma Inc. (also referred to as "Array,","we", "us", "our" or "the Company"), incorporated in Delaware on February 6, 1998, is a biopharmaceutical company focused on the discovery, development and commercialization of targeted small molecule cancer therapies. The Company formed Yarra Therapeutics, LLC, a Delaware limited liability company ("Yarra"), in anticipation of the contribution by the Company of certain rights and assets related to ARRY-797, including all patents, patent applications and other intellectual property rights, pre-clinical and clinical data, regulatory submissions, inventory, contracts, equipment and books and records related to its ARRY-797 drug program, to Yarra in December 2017. Yarra is currently a wholly-owned subsidiary of Array. Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC") for interim reporting and, as permitted under those rules, do not include all of the disclosures required by U.S. generally accepted accounting principles ("U.S. GAAP") for complete financial statements. The unaudited condensed consolidated financial statements reflect all normal and recurring adjustments that, in the opinion of management, are necessary to present fairly the Company's financial position, results of operations and cash flows for the interim periods presented. Operating results for an interim period are not necessarily indicative of the results that may be expected for a full year. The Company's management performed an evaluation of its activities through the date of filing of this Quarterly Report on Form 10-Q. These unaudited condensed consolidated financial statements should be read in conjunction with the Company's audited financial statements and the notes thereto for the fiscal year ended June 30, 2017 , included in its Annual Report on Form 10-K filed with the SEC on August 11, 2017, from which the Company derived its balance sheet data as of June 30, 2017 . The Company operates in one reportable segment and, accordingly, no segment disclosures have been presented herein. All of the Company's equipment, leasehold improvements and other fixed assets are physically located within the U.S., and the vast majority of its agreements with its partners are denominated in U.S. dollars. Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires the Company's management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and related disclosure of contingent assets and liabilities. Management bases its estimates on the Company's historical experience and on various other assumptions that it believes are reasonable under the circumstances. These estimates are the basis for the Company's judgments about the carrying values of assets and liabilities, which in turn may impact its reported revenue and expenses. The Company's actual results could differ significantly from these estimates under different assumptions or conditions. The Company believes its condensed consolidated financial statements are most significantly impacted by the following accounting estimates and judgments: (i) identifying deliverables under collaboration and license agreements involving multiple elements and determining whether such deliverables are separable from other aspects of the contractual relationship; (ii) estimating the selling price of deliverables for the purpose of allocating arrangement consideration for revenue recognition; (iii) estimating the periods over which the allocated consideration for deliverables is recognized; (iv) estimating accrued outsourcing costs for clinical trials and preclinical testing; and (v) estimating fair value of the notes payable. Liquidity With the exception of fiscal year 2015, the Company has incurred operating losses and an accumulated deficit as a result of ongoing research and development spending since inception. As of December 31, 2017 , the Company had an accumulated deficit of $990.7 million . The Company had net losses of $34.1 million and $72.0 million for the three and six months ended December 31, 2017 and net losses of $116.8 million and $92.8 million for the fiscal years ended June 30, 2017 and 2016 , respectively. The Company had net income of $9.4 million for the fiscal year ended June 30, 2015. The Company has historically funded its operations from upfront fees, proceeds from research and development reimbursement arrangements, and license and milestone payments received under its drug collaborations and license agreements, the sale of equity securities, and debt provided by convertible debt and other credit facilities. The Company believes that its cash, cash equivalents and marketable securities as of December 31, 2017 will enable it to continue to fund operations in the normal course of business for more than a 12-month period from the date of filing this Quarterly Report on form 10Q. Until the Company can generate sufficient levels of cash from operations, which it does not expect to achieve in at least the next two years, and because sufficient funds may not be available to it when needed from existing collaborations, the Company expects that it will be required to continue to fund its operations in part through the sale of debt or equity securities, and through licensing select programs or partial economic rights that include upfront, royalty and/or milestone payments. The Company's ability to successfully raise sufficient funds through the sale of debt or equity securities or from debt financing from lenders when needed is subject to many risks and uncertainties and, even if it were successful, future equity issuances would result in dilution to its existing stockholders and any future debt or debt securities may contain covenants that limit the Company’s operations or ability to enter into certain transactions. The Company also may not successfully consummate new collaboration and license agreements that provide for upfront fees or milestone payments or on favorable terms to the Company, or the Company may not earn milestone payments under such agreements when anticipated, or at all. The Company's ability to realize milestone or royalty payments under existing agreements and to enter into new arrangements that generate additional revenue through upfront fees and milestone or royalty payments is subject to a number of risks, many of which are beyond the Company's control. The Company's assessment of its future need for funding and its ability to continue to fund its operations is a forward-looking statement that is based on assumptions that may prove to be wrong and that involve substantial risks and uncertainties. The Company's actual future capital requirements could vary as a result of a number of factors. These factors include the risk factors disclosed by the Company under the heading "Item 1A. Risk Factors" under Part II of this Quarterly Report on Form 10-Q and under Part I of its Annual Report on Form 10-K for the fiscal year ended June 30, 2017, and in other reports it files with the SEC. If the Company is unable to generate enough revenue from its existing or new collaboration and license agreements when needed or to secure additional sources of funding and receive related full and timely collections of amounts due, it may be necessary to significantly reduce the current rate of spending through reductions in staff and delaying, scaling back, or stopping certain research and development programs, including more costly late phase clinical trials on its wholly-owned programs. Insufficient liquidity may also require the Company to relinquish greater rights to product candidates at an earlier stage of development or on less favorable terms to the Company and its stockholders than the Company would otherwise choose in order to obtain upfront license fees needed to fund operations. Concentration of Business Risks The following counterparties contributed greater than 10% of the Company's total revenue during at least one of the periods set forth below. The revenue from these counterparties as a percentage of total revenue was as follows: Three Months Ended Six Months Ended December 31, December 31, 2017 2016 2017 2016 Novartis Pharmaceuticals 53.1 % 63.8 % 56.4 % 71.8 % Asahi Kasei 23.0 % 2.2 % 14.9 % 2.2 % Pierre Fabre 10.5 % 7.0 % 11.8 % 6.7 % Loxo Oncology 5.7 % 18.6 % 8.0 % 13.5 % 92.3 % 91.6 % 91.1 % 94.2 % The loss of one or more of the Company's significant partners or collaborators could have a material adverse effect on its business, operating results or financial condition. Although the Company is impacted by economic conditions in the biotechnology and pharmaceutical sectors, management does not believe significant credit risk exists as of December 31, 2017 . Geographic Information The following table details revenue by geographic area based on the country in which the Company's counterparties are located (in thousands): Three Months Ended Six Months Ended December 31, December 31, 2017 2016 2017 2016 North America $ 4,662 $ 9,528 $ 10,163 $ 13,626 Europe 26,852 34,035 49,148 68,341 Asia Pacific 10,704 960 12,653 1,827 Total revenue $ 42,218 $ 44,523 $ 71,964 $ 83,794 Accounts Receivable Novartis Pharmaceutical Ltd. and Novartis Pharma AG (collectively, "Novartis") accounted for 75% and 70% of the Company's total accounts receivable balance as of December 31, 2017 and June 30, 2017 , respectively. Pierre Fabre Medicament SAS ("Pierre Fabre") accounted for 12% and 7% of the Company's total accounts receivable balance as of December 31, 2017 and June 30, 2017 , respectively. Summary of Significant Accounting Policies The Company's significant accounting policies are described in Note 1 to its audited financial statements for the fiscal year ended June 30, 2017 , included in its Annual Report on Form 10-K filed with the SEC. There have been no material changes in the Company’s significant accounting policies as previously disclosed in the 2017 Annual Report. Recent Accounting Pronouncements In May 2014, the FASB issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers , which requires entities to recognize revenue from the transfer of promised goods or services to customers based on the amount of the consideration to which the entity expects to be entitled to receive in exchange for those goods or services. The new guidance also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations . The purpose of ASU No. 2016-08 is to clarify the implementation of guidance relating to principal versus agent considerations. For public entities, the amendments in ASU No. 2016-08 are effective for interim and annual reporting periods beginning after December 15, 2017. The Company is currently evaluating the impact of ASU No. 2016-08 on its condensed consolidated financial statements and related disclosures. The FASB subsequently issued ASU No. 2016-10, Revenue from Contracts with Customer (Topic 606) Identifying Performance Obligations and Licensing, to address issues arising from implementation of the new revenue recognition standard. ASU 2014-09 and ASU 2016-10 are effective for interim and annual periods beginning July 1, 2018, and may be adopted earlier, but not before July 1, 2017. The revenue standards are required to be adopted by taking either a full retrospective or a modified retrospective approach. The Company has not elected early adoption and has not concluded on an adoption method. The Company is continuing to assess the impact of the new guidance on its accounting policies and procedures and is evaluating the new requirements as applied to existing revenue contracts. While this assessment is still in progress, the Company believes the most significant impact will relate to the timing of collaboration revenues, where the recognition of variable consideration such as milestone payments may be accelerated. In conjunction with its continuing assessment of the impact of the new guidance, the Company is also evaluating its method of adoption and reviewing and updating its internal controls over financial reporting to ensure that information required to implement the new standard is appropriately captured and recorded. The Company will implement any changes as required to facilitate adoption of the new guidance beginning in the first quarter of fiscal 2019. In addition, the Company continues to monitor additional changes, modifications, clarifications or interpretations undertaken by the FASB or others, which may impact its current conclusions. In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities . ASU No. 2016-01 requires equity investments to be measured at fair value with changes in fair value recognized in net income; simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; eliminates the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; requires an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; requires separate presentation of financial assets and financial liabilities by measurement category and form of financial assets on the balance sheet or the accompanying notes to the condensed consolidated financial statements and clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. ASU No. 2016-01 is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The Company is currently evaluating the impact that ASU No. 2016-01 will have on its condensed consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) which supersedes FASB ASC Topic 840, Leases (Topic 840) and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than twelve months regardless of classification. Leases with a term of twelve months or less will be accounted for similar to existing guidance for operating leases. The standard is effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted upon issuance. The Company is currently evaluating the impact that ASU 2016-02 will have on its condensed consolidated financial statements and related disclosures. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13). ASU 2016-13 requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. ASU 2016-13 limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The new standard will be effective for the Company on January 1, 2020. Early adoption will be available on January 1, 2019. The Company is currently evaluating the effect that ASU 2016-13 will have on its condensed consolidated financial statements and related disclosures. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) . This amendment will provide guidance on the presentation and classification of specific cash flow items to improve consistency within the statement of cash flows. ASU 2016-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted. The Company is evaluating the effect that ASU 2016-15 will have on its condensed consolidated financial statements and related disclosures. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230) Restricted Cash . The new guidance requires that the reconciliation of the beginning-of-period and end-of-period amounts shown in the statement of cash flows include restricted cash and restricted cash equivalents. If restricted cash is presented separately from cash and cash equivalents on the balance sheet, companies will be required to reconcile the amounts presented on the statement of cash flows to the amounts on the balance sheet. Companies will also need to disclose information about the nature of the restrictions. The guidance is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The Company does not anticipate ASU 2016-18 will have a material impact on its condensed consolidated financial statements upon adoption. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805) Clarifying the Definition of a Business . The amendments in this ASU clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. The guidance is effective for annual periods beginning after December 15, 2017, including interim periods within those periods. The Company does not anticipate ASU 2017-01 will have a material impact on its condensed consolidated financial statements upon adoption. In May 2017, the FASB issued ASU 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting , 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. It is effective prospectively for the annual period ending June 30, 2019 and interim periods within that annual period. Early adoption is permitted. The Company does not expect ASU 2017-09 will have a significant impact on its condensed consolidated financial statements upon adoption. In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480) and Derivatives and Hedging (Topic 815): I. Accounting for Certain Financial Instruments with Down Round Features; II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception . Part I of this update addresses the complexity of accounting for certain financial instruments with down round features. Down round features are features of certain equity-linked instruments (or embedded features) that result in the strike price being reduced on the basis of the pricing of future equity offerings. Current accounting guidance creates cost and complexity for entities that issue financial instruments (such as warrants and convertible instruments) with down round features that require fair value measurement of the entire instrument or conversion option. Part II of this update addresses the difficulty of navigating Topic 480, Distinguishing Liabilities from Equity , because of the existence of extensive pending content in the FASB Accounting Standards Codification. This pending content is the result of the indefinite deferral of accounting requirements about mandatorily redeemable financial instruments of certain nonpublic entities and certain mandatorily redeemable noncontrolling interests. The amendments in Part II of this update do not have an accounting effect. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018. The Company is evaluating the effect that ASU 2017-11 will have on its condensed consolidated financial statements and related disclosures.

MARKETABLE SECURITIES

MARKETABLE SECURITIES	6 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
MARKETABLE SECURITIES	MARKETABLE SECURITIES Marketable securities consisted of the following as of December 31, 2017 and June 30, 2017 (in thousands): December 31, 2017 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Short-term available-for-sale securities: U.S. treasury securities $ 354,577 $ — $ (676 ) $ 353,901 Mutual fund securities 320 — — 320 354,897 — (676 ) 354,221 Long-term available-for-sale securities: Mutual fund securities 1,045 — — 1,045 1,045 — — 1,045 Total $ 355,942 $ — $ (676 ) $ 355,266 June 30, 2017 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Short-term available-for-sale securities: U.S. treasury securities $ 108,174 $ — $ (76 ) $ 108,098 Mutual fund securities 292 — — 292 108,466 — (76 ) 108,390 Long-term available-for-sale securities: Mutual fund securities 732 — — 732 732 — — 732 Total $ 109,198 $ — $ (76 ) $ 109,122 The majority of the mutual fund securities shown in the above tables are securities held under the Array BioPharma Inc. Deferred Compensation Plan. The estimated fair value of the Company's marketable securities, all of which are classified as Level 1 (quoted prices are available), was $355.3 million and $109.1 million as of December 31, 2017 and June 30, 2017 , respectively. The estimated fair value of the Company's marketable securities is determined using quoted prices in active markets for identical assets based on the closing price as of the balance sheet date. As of December 31, 2017 , the amortized cost and estimated fair value of available-for-sale securities by contractual maturity were as follows (in thousands): Amortized Fair Cost Value Due in one year or less $ 354,577 $ 353,901 Total $ 354,577 $ 353,901

COLLABORATION AND OTHER AGREEME

COLLABORATION AND OTHER AGREEMENTS	6 Months Ended
	Dec. 31, 2017
Collaboration and Other Agreements [Abstract]
COLLABORATION AND OTHER AGREEMENTS	COLLABORATION AND OTHER AGREEMENTS The following table summarizes total revenue recognized for the periods indicated (in thousands): Three Months Ended Six Months Ended December 31, December 31, 2017 2016 2017 2016 Reimbursement revenue Novartis (1) $ 22,395 $ 27,948 $ 40,587 $ 59,269 Collaboration and other revenue Pierre Fabre 3,674 2,375 7,023 4,153 Loxo 2,395 1,938 4,653 4,805 Mirati 1,422 875 2,811 1,750 Amgen 500 — 1,000 — Asahi Kasei 262 361 730 628 Cascadian 75 15 106 52 Ono 87 — 87 — Celgene 60 — 68 — Novartis (2) — 450 — 900 Other partners 33 16 38 31 Total collaboration and other revenue 8,508 6,030 16,516 12,319 License and milestone revenue Asahi Kasei 9,437 600 10,000 1,200 Ono 919 — 1,837 — Pierre Fabre 750 750 1,500 1,500 Loxo — 6,362 1,107 6,465 Mirati 209 208 417 416 Roche — 2,500 — 2,500 Other Partners — 125 — 125 Total license and milestone revenue 11,315 10,545 14,861 12,206 Total revenue $ 42,218 $ 44,523 $ 71,964 $ 83,794 (1) Consists of reimbursable expenses incurred and accrued as reimbursement revenue that are receivable under the Transition Agreements with Novartis. (2) Represents the recognition of revenue that was deferred from the consideration received in March 2015 upon the effective date of the Termination and Asset Transfer Agreement with Novartis relating to binimetinib. Deferred revenue balances were as follows for the dates indicated (in thousands): December 31, June 30, 2017 2017 Ono $ 29,392 $ 31,229 Pierre Fabre 23,895 25,395 Asahi Kasei — 9,000 Mirati 2,750 4,167 Loxo 3,203 2,690 Amgen 1,000 2,000 Total deferred revenue 60,240 74,481 Less: Current portion (13,419 ) (17,156 ) Deferred revenue, long-term portion $ 46,821 $ 57,325 Milestone Payments The Development and Commercialization Agreement with Pierre Fabre contains substantive potential milestone payments of up to $25.0 million for achievement of two regulatory milestones relating to European Commission marketing approvals for two specified indications and of up to $390.0 million for achievement of seven commercialization milestones if certain net sales amounts are achieved for any licensed indications. The License, Development and Commercialization Agreement with Ono Pharmaceutical Co., Ltd. ("Ono") contains substantive potential milestone payments of up to ¥1.8 billion ( $16.0 million ) for achievement of four development milestones, ¥5 billion ( $44.5 million ) for the achievement of eight regulatory milestones and ¥10.5 billion ( $93.5 million ) for the achievement of five commercialization milestones if certain annual net sales targets are achieved. As of December 31, 2017 , ¥1.0 billion was the equivalent of approximately $8.9 million (based on the exchange rate published by Oanda). The Drug Discovery Collaboration Option Agreement with Mirati Therapeutics, Inc. ("Mirati") contains substantive potential milestone payments of up to $18.5 million for eight remaining developmental milestones and up to $674.0 million for the achievement of fourteen commercialization milestones if certain net sales amounts are achieved in the United States, the European Union and Japan. The Drug Discovery Collaboration Agreement with Loxo Oncology contains substantive potential milestone payments for certain nominated programs of up to $14.0 million for four remaining developmental milestones and up to $625.0 million for the achievement of twenty-two commercialization milestones if certain net sales amounts are achieved for any licensed drug candidates in the United States, the European Union and Japan. The Collaboration and License Agreement with Asahi Kasei Pharma Corporation ("Asahi Kasei") contains milestone payments of up to $10.0 million related to the achievement of three remaining developmental and regulatory milestones and up to $52.5 million for a milestone payment at the time of the first commercial sale and the achievement of four commercialization milestones if certain net sales amounts are achieved . The Research Collaboration and License Agreement with Amgen contains substantive potential milestone payments of up to $3.0 million for preclinical development services over a two -year period unless Amgen terminates the Agreement with 60 days' written notice to Array in advance of the contracted payment dates. The Research Collaboration and License Agreement with Amgen contains substantive potential milestone payments of up to $14.0 million for two development milestones and up to $140.0 million for the achievement of four commercialization milestones if certain net sales amounts are achieved for any licensed drug candidates. The Collaboration and License Agreement with AstraZeneca, PLC contains substantive potential milestone payments for selumetinib of up to $36.0 million for nine remaining regulatory milestones and up to $34.0 million for the achievement of three commercialization milestones if certain net sales amounts are achieved in the United States, the European Union and Japan. On July 28, 2017, AstraZeneca and Merck announced an agreement to share the development and commercialization costs for selumetinib monotherapy and non-PD-L1/PD-1 combination therapy opportunities. Based on this agreement, Array remains eligible to receive from AstraZeneca milestones and royalties on all future selumetinib sales, and now expects to receive a portion of certain consideration paid by Merck to AstraZeneca. Array has informed AstraZeneca that it is disputing the small consideration that AstraZeneca intends to pay Array related to both upfront and potential future milestones under AstraZeneca's agreement with Merck. Furthermore, prior to the announcement of the AstraZeneca / Merck agreement, Array informed AstraZeneca of its position that the Neurofibromatosis type 1 (NF1) development program is outside the permitted field of its license. Array filed a legal action on December 7, 2017 naming AstraZeneca as the defendant in New York State Court in Manhattan regarding this dispute.

DEBT

DEBT	6 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
DEBT	DEBT Outstanding debt consists of the following (in thousands): December 31, June 30, 2017 2017 Notes Payable at fair value $ 12,700 $ 12,600 2020 convertible senior notes $ — $ 132,250 2024 convertible senior notes 126,060 — Silicon Valley Bank term loan (1) 16,200 16,200 Long-term debt, gross 142,260 148,450 Less: Unamortized debt discount and fees (48,996 ) (27,145 ) Long-term debt, net $ 93,264 $ 121,305 (1) Outstanding debt owed to Silicon Valley Bank includes a $1.2 million final payment fee. Redmile Notes Payable On September 2, 2016, the Company entered into a Note Purchase Agreement (the “Note Purchase Agreement”) with Redmile Capital Offshore Fund II, Ltd. and Redmile Biopharma Investments I, L.P. (collectively, “Redmile”) pursuant to which the Company issued to Redmile Subordinated Convertible Promissory Notes (the “Notes”) in the aggregate original principal amount of $10.0 million . The Notes bear interest at the rate of 5% per annum and, unless converted or otherwise repaid or satisfied as described below, the principal amount and all accrued interest thereon plus an aggregate exit fee (the “Repayment Amount”) is due and payable on maturity. On August 7, 2017, the Company entered into an amendment to the Notes issued to Redmile pursuant to which the maturity date of the Notes was extended to August 6, 2018 and the exit fee of the Notes was increased from $3.0 million to an amount equal to 50% , or $5.0 million , of the principal amount under the Notes. If an event of default specified under the Notes occurs, the Note holders may declare the Repayment Amount, and any other amounts payable under the Notes, immediately due and payable. The Company evaluated its debt amendments under ASC 470 and determined that the amendments do not qualify as a troubled debt restructuring or an extinguishment and therefore the effects of the amendments are reflected as a change in fair value. Conversion of the Notes The Notes contemplate that, solely at the Company’s choice, the Company may elect to form a subsidiary (the “797 Subsidiary”) and contribute certain assets and rights relating to its drug ARRY-797 in exchange for all of the outstanding equity of such 797 Subsidiary. In such event, and if a preferred stock financing of the 797 Subsidiary of at least $10.0 million in aggregate gross proceeds (excluding conversion of the Note) to bona fide institutional investors other than the Note holders (a “Qualified Financing”) closes prior to the Maturity Date, then all outstanding principal and accrued interest under the Notes shall convert automatically into the shares of capital stock issued in the Qualified Financing at a conversion price equal to the lesser of (A) 80% of the purchase price of the securities sold in the Qualified Financing if the closing of the Qualified Financing occurs on or prior to March 1, 2017, or 70% of the purchase price of the securities sold in the Qualified Financing if the closing of the Qualified Financing occurs after March 1, 2017, and (B) the price per share calculated in the same manner as the price per share of equity securities sold in the Qualified Financing, but instead based on a pre-money valuation of the 797 Subsidiary of $75.0 million . If the Company has not formed the 797 Subsidiary by the Maturity Date or, if a 797 Subsidiary was formed and a Qualified Financing has not closed on or prior to the Maturity Date, then the Company shall have the right to convert, on the Maturity Date, the Repayment Amount into shares of a newly established series of the Company's preferred stock, to be designated as Series A Convertible Preferred Stock, at a conversion price equal to the average daily volume-weighted average price per share of the Company’s common stock during the ten ( 10 ) consecutive trading days ending on the trading day immediately preceding the Maturity Date. The shares issued upon any such conversion shall be subject to an aggregate cap equal to 19.99% of the outstanding shares of the Company’s common stock, on an as-converted basis, on the Maturity Date. Other Repayment Provisions If, solely at the Company’s choice, prior to the closing of a Qualified Financing or other conversion or repayment or other satisfaction in full of the Notes, the Company sells or transfers substantially all of the assets and rights relating to ARRY-797 to a third party other than the holders of the Notes or any of its affiliates (a “797 Sale”), then upon the closing of such 797 Sale and in full satisfaction of the Notes, the Company is required to pay to the Note holders an amount equal to the greater in the aggregate of (i) $20.0 million or (ii) 15% of the fair market value of the consideration actually paid to the Company or the 797 Subsidiary (or any of their respective affiliates or stockholders) in the 797 Sale, subject to an aggregate $100.0 million cap. If, solely at the Company’s choice, the Company enters into an agreement with a third party other than the holders of the Notes or any of their affiliates to license ARRY 797 on an exclusive basis for the development and commercialization of ARRY-797 in all fields of use in the United States and any other territories (a “Qualified 797 License”) prior to the closing of a Qualified Financing or other conversion or repayment or other satisfaction in full of the Notes, then upon entering into such Qualified 797 License and in full satisfaction of the Notes, the Company is required to pay to the Note holders an amount in the aggregate equal to 50% of the first $50.0 million in aggregate milestone or royalty payments plus 20% of any subsequent milestone or royalty payments, in each case actually paid to the Company or the 797 Subsidiary (or any of their respective affiliates), as the case may be, pursuant to such Qualified 797 License, subject to an aggregate cap of $100.0 million . In addition, if solely at its choice the Company enters into an exclusive license for the development and commercialization of ARRY-797 to a third party in one or more territories that do not include the United States, the Note holders have the right to elect to treat such license agreement as a “Qualified 797 License” by giving Array written notice of such election with five business days of the effective date of the license agreement. If all or substantially all of the assets of the Company are sold or other change in control of the Company specified in the Notes occurs prior to the closing of a Qualified Financing or other conversion or repayment or other satisfaction in full of the Notes, then upon the closing of such transaction and in full satisfaction of the Notes, at the third party acquirer’s option, the Company is required to either: (i) pay to the Note holders a cash amount in the aggregate equal to $40.0 million ; or (ii) (A) pay to the Note holders a cash amount in the aggregate equal to $25.0 million ; and (B) grant, or cause to be granted, a right of first refusal to the Note holders to acquire the 797 Subsidiary or the 797 Assets, as the case may be. Accounting for the Notes Due to the complexity and number of embedded features within the Notes and as permitted under accounting guidance, the Company elected to account for the Notes and all the embedded features under the fair value option. The Company recognizes the Notes at fair value rather than at historical cost, with changes in fair value recorded in the statements of operations. Direct costs and fees incurred to issue the Notes were recognized in earnings as incurred and were not deferred. On the initial measurement date of September 2, 2016, the fair value of the Notes was estimated at $10.0 million . On August 7, 2017 when the Notes were amended, the fair value of the Notes was estimated at $12.0 million . Upfront costs and fees related to items for which the fair value option was elected was $0.2 million and was recorded as a component of other expenses for the three months ended September 30, 2016. As of December 31, 2017 , the fair value of the Notes was $12.7 million . For more information on the fair value determination of the Notes, see Note 5 - Redmile Notes . Formation of 797 Subsidiary The Company formed the 797 Subsidiary,Yarra Therapeutics, LLC, a Delaware limited liability company ("Yarra"), and contributed certain rights and assets related to ARRY-797, including all patents, patent applications and other intellectual property rights, pre-clinical and clinical data, regulatory submissions, inventory, contracts, equipment and books and records related to its ARRY-797 drug program (the “797 Assets”), to Yarra in December 2017. Yarra is currently a wholly-owned subsidiary of Array and Array has appointed a Chief Executive Officer of Yarra who, among other things, will be seeking equity financing for Yarra to fund further development of the 797 Assets. The establishment of Yarra and the Company's contributions described above did not trigger any obligations under the Other Repayment Provisions or the terms associated with the Notes conversion as the Company has not yet sold or licensed any technology to a third party nor has the Company entered into a Qualified Financing. Registration Rights If the Company elects to convert the Notes into shares of Series A Convertible Preferred Stock as described above, the Company has agreed in the Note Purchase Agreement to register such shares under the Securities Act of 1933, as amended (the “Securities Act”), on a registration statement on Form S-3. In such event, the Company must file the registration statement on the Maturity Date and use commercially reasonable efforts to cause the registration statement to become effective as promptly as possible after such filing, but no later than 75 days after the Maturity Date. The Company may suspend the availability of the registration statement for up to 90 days for no more than 45 days in any 12 -month period for any bona fide reason. If the Company defaults on certain of its obligations relating to the registration of such shares of Series A Preferred Stock, the Company must pay an amount in the aggregate equal to 5% of the purchase price of the Notes to which the affected registered shares relate. The Company has agreed to pay all costs and expenses associated with the registration of the Series A Convertible Preferred Stock and, with certain exceptions, to indemnify the holders of shares registered on any such registration against liabilities relating to any such registration. Silicon Valley Bank Term Loan On December 22, 2016 the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with Silicon Valley Bank (“SVB”) providing for a term loan in the original principal amount of $15.0 million (the “Term Loan Amount”) and a revolving line of credit of up to $5.0 million (“Revolving Line”). The Company may request advances under the revolving line of credit, which may be repaid and reborrowed, or utilize the line of credit for the issuance of letters of credit, foreign exchange contracts or other cash management services. The Company utilized $14.6 million of the proceeds from the term loan to repay in full its outstanding obligations under the Loan and Security Agreement dated June 28, 2005, as amended, with Comerica Bank. The entire Term Loan Amount was loaned on the Effective Date, and the Company has obtained a letters of credit in the aggregate amount of $2.9 million to secure the Company's obligations under its lease agreement for its Boulder, Colorado and Cambridge, Massachusetts facilities. The cost of the term loan approximated its fair value. The outstanding principal amount under the term loan bears interest at a floating per annum rate equal to the Prime Rate minus 2.0% (but not less than 0.0% ) and the principal amount of any advances outstanding under the revolving line bear interest at a floating per annum rate equal to the prime rate. The interest rate was 2.50% as of December 31, 2017 . The Company must make monthly payments of interest under the term loan commencing January 1, 2017 until maturity and, commencing on January 1, 2019 and monthly thereafter, the Company must also make payments of principal under the term loan based on a 36 -month amortization schedule. Payments of accrued interest on any advances outstanding under the revolving line of credit are payable monthly. A final payment of accrued interest and principal due on the term loan and on any outstanding advances is due on the maturity date of December 1, 2021. The Loan Agreement provides for a revolving line commitment fee of $50 thousand , payable in five equal installments from the Effective Date and an unusued revolving line facility fee equal to 0.2% per annum of the average unused portion of the Revolving Line. Upon repayment or acceleration of the term loan, a final payment fee equal to 8.0% of the Term Loan Amount is payable. The final payment fee of $1.2 million is being recognized on a straight line basis over the term of the loan and is being reflected as debt discount. If the term loan is prepaid or accelerated prior to the maturity date, the Company must also pay a fee equal to (i) 2.0% of the Term Loan Amount if such prepayment or acceleration occurs on or prior to the first anniversary of the Effective Date, or (ii) 1.0% of the Term Loan Amount if such prepayment or acceleration occurs after the first anniversary of the Effective Date. If the revolving line is terminated prior to the maturity date for any reason, the Company must pay a termination fee equal to (i) 2.0% of the Revolving Line if such termination occurs on or prior to the first anniversary of the Effective Date, or (ii) 1.0% of the Revolving Line if such termination occurs after the first anniversary of the Effective Date. The Company granted SVB a first priority security interest in all assets other than its intellectual property, provided that accounts and proceeds of the Company’s intellectual property constitutes collateral and the Company has agreed not to encumber its intellectual property without SVB’s consent. The Loan Agreement contains customary covenants, including restrictions on changes in control of the Company, the incurrance of additional indebtedness, future encumbrances on Array’s assets, the payment of dividends or distributions on the Company’s common stock and the sale, lease, transfer or disposition of Binimetinib and Encorafenib outside of certain markets if the Company’s cash and cash equivalents maintained with SVB fall below certain levels. In addition, the Company must maintain a liquidity ratio, defined as (i) the Company’s unrestricted cash and cash equivalents maintained at SVB or its affiliates plus eligible accounts divided by (ii) all outstanding obligations owed to SVB, of at least 2.0 to 1.0, measured monthly. Upon an event of default under the Loan Agreement, SVB is entitled to accelerate and demand payment of all amounts outstanding under the Loan Agreement, including payment of all applicable termination and prepayment fees, demand that the Company deposit at least 105% of the face amount of any letters of credit remaining undrawn to secure all obligations thereunder, and exercise other remedies available to SVB under the Loan Agreement and at law or in equity. 3.00% Convertible Senior Notes Due 2020 On June 10, 2013, through a registered underwritten public offering, the Company issued and sold $132.3 million aggregate principal amount of 3.00% convertible senior notes due 2020 (the "2020 Notes"), resulting in net proceeds to Array of approximately $128.0 million after deducting the underwriting discount and offering expenses. As described below, in December 2017, the Company completed an exchange with certain holders of the 2020 Notes of $126.1 million in principal of the 2020 Notes for an equal principal amount of newly issued 2.625% convertible senior notes due 2024 and for shares of the Company's common stock. The holders of the remaining 2020 Notes elected to convert all remaining outstanding 2020 Notes into shares of the Company's common stock in December 2017. The 2020 Notes were the general senior unsecured obligations of Array. The 2020 Notes bore interest at a rate of 3.00% per year, payable semi-annually on June 1 and December 1 of each year with all principal due at maturity. The 2020 Notes were scheduled to mature on June 1, 2020, unless earlier converted by the holders or redeemed by the Company. Exchange and Conversion of 2020 Notes On November 16 and November 20, 2017, the Company entered into separate, privately negotiated exchange agreements (“Exchange Agreements”) with a limited number of holders (“Noteholders”) of its outstanding 2020 Notes, pursuant to which the Company agreed to exchange (the “Exchanges”) approximately $126.1 million in aggregate principal amount of 2020 Notes held by the Noteholders for (i) an aggregate of 7,955,560 shares of its Common Stock (collectively, the “Exchange Shares”), and (ii) an aggregate of $126.1 million in aggregate principal amount of its newly issued 2.625% Convertible Senior Notes due 2024 (the “2024 Notes”). Upon completion of the Exchanges on December 1, 2017, the aggregate principal amount of the 2020 Notes was reduced to approximately $6.2 million . On December 4, 2017, the Company issued a notice of redemption to the remaining holders of the remaining 2020 Notes, pursuant to which the Company would redeem the outstanding 2020 Notes for cash unless the holders of such 2020 Notes notified the Company of their intention to convert their 2020 Notes into shares of the Company's common stock based on the conversion rate then in effect. As of December 31, 2017, holders of the remaining 2020 Notes had converted such 2020 Notes into an aggregate of 913,368 shares of the Company's common stock. The Company accounted for the exchange of the 2020 Notes for the 2024 Notes and conversion of the 2020 Notes as debt extinguishments in accordance with ASC 470 and as a result recorded a $6.5 million loss on extinguishment for the three months ended December 31, 2017. 2.625% Convertible Senior Notes Due 2024 The 2024 Notes issued on December 1, 2017 in the Exchanges are the Company’s direct unsecured obligations and rank equal in right of payment with all of the Company’s other existing and future unsecured and unsubordinated indebtedness, including the Redmile Notes. The 2024 Notes are effectively subordinated to any of the Company’s existing and future secured indebtedness, including the Company’s indebtedness under its loan and security agreement with Silicon Valley Bank, to the extent of the value of the Company’s assets that secure such indebtedness. The 2024 Notes will mature on December 1, 2024 and bear interest at a rate of 2.625% , payable semiannually in arrears on June 1 and December 1 of each year, beginning on June 1, 2018. Prior to September 1, 2024, holders may convert the 2024 Notes only under the following circumstances: (1) during any fiscal quarter commencing after December 31, 2017, if the last reported sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding fiscal quarter is greater than or equal to 130% of the applicable conversion price on each applicable trading day; (2) during the five consecutive business day period after any five consecutive trading day period (the “measurement period”) in which the trading price per $1,000 principal amount of 2024 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the common stock and the applicable conversion rate on each such trading day; (3) if the Company calls the 2024 Notes for redemption, at any time prior to the close of business on the business day prior to the redemption date; or (4) upon the occurrence of certain corporate events specified in the Indenture dated December 1, 2017 (the "Indenture") with The Bank of New York Mellon Trust Company, N.A., trustee of the 2024 Notes (the "Trustee"). On or after September 1, 2024 until the close of business on the scheduled trading day immediately prior to the maturity date, holders may convert their 2024 Notes at any time, regardless of the foregoing circumstances. Upon conversion, the holders will receive, at the Company’s option, shares of the Company’s common stock, cash or a combination of shares and cash. The 2024 Notes will be convertible at an initial conversion rate of 64.6987 shares per $1,000 in principal amount of 2024 Notes, equivalent to a conversion price of approximately $15.46 per share, subject to certain adjustments set forth in the Indenture. Upon the occurrence of a fundamental change (as defined in the Indenture) involving Array, holders of the 2024 Notes may require Array to repurchase all or a portion of their Notes for cash at a price equal to 100% of the principal amount of the Notes to be purchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. On or after December 8, 2021 and prior to September 1, 2024, the Company may redeem for cash all or part of the outstanding 2024 Notes if the last reported sale price of the Company’s common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which the Company provides notice of redemption. The redemption price will equal 100% of the principal amount of the 2024 Notes to be redeemed, plus all accrued and unpaid interest to, but excluding, the redemption date. The Indenture contains customary terms and covenants and events of default. If an event of default (as defined in the Indenture) occurs and is continuing, the Trustee by notice to the Company, or the holders of at least 25% in aggregate principal amount of the 2024 Notes then outstanding by notice to the Company and the Trustee, may, and the Trustee at the request of such holders shall, declare 100% of the principal of, premium, if any, and accrued and unpaid interest on all the Notes to be due and payable. In the case of an event of default arising out of certain bankruptcy or insolvency events (as set forth in the Indenture), 100% of the principal of, premium, if any, and accrued and unpaid interest on the 2024 Notes will automatically become due and payable. Notwithstanding the foregoing, if Array fails to comply with certain reporting covenants under the Indenture, the Company may elect to pay additional interest on the Notes as the sole remedy for such a default. The Indenture provides that the Company shall not amalgamate or consolidate with or merge with or into another person, or convey, transfer or lease its properties and assets substantially as an entirety to another person, unless (a) the successor person, if any, is a corporation organized and existing under the laws of the United States, any state of the United States or the District of Columbia and expressly assumes by supplemental indenture all of the Company’s obligations under the 2024 Notes and the Indenture; (b) immediately after giving effect to the transaction, no default or event of default shall have occurred and be continuing; (c) the Company shall have undertaken commercially reasonable efforts to restructure the 2024 Notes so that, after any such transaction is given effect, any conversion of the 2024 Notes would be exempt from the registration requirements of the Securities Act of 1933, as amended (the “Securities Act”), pursuant to Section 3(a)(9) thereof; (d) the Company shall have delivered to the Trustee an officers’ certificate and an opinion of counsel, each stating that such transaction and such supplemental indenture (if any) comply with the Indenture; and (e) other conditions specified in the Indenture are met. In accordance with ASC 470-20, the Company used an effective interest rate of 9.75% to determine the liability component of the 2024 Notes. This resulted in the recognition of $80.4 million as the liability component of the 2024 Notes and the recognition of the residual $45.7 million as the debt discount with a corresponding increase to additional paid-in capital for the equity component of the 2024 Notes. The underwriting discount and estimated offering expenses of $4.3 million were allocated between the debt and equity issuance costs in proportion to the allocation of the liability and equity components of the 2024 Notes. Equity issuance costs of $1.6 million were recorded as an offset to additional paid-in capital. Total debt issuance costs of $2.7 million were recorded on the issuance date, and are reflected in the Company's balance sheets for all periods presented on a consistent basis with the debt discount, or as a direct deduction from the carrying value of the associated debt liability. The debt discount and debt issuance costs will be amortized as non-cash interest expense through December 1, 2024. The balance of unamortized debt issuance costs was $2.7 million as of December 31, 2017. The fair value of the 2024 Notes was approximately $144.4 million at December 31, 2017 and was determined using Level 2 inputs based on their quoted market values. Summary of Interest Expense The following table shows the details of the Company's interest expense for all of its debt arrangements outstanding during the periods presented, including contractual interest, and amortization of debt discount, debt issuance costs and loan transaction fees that were charged to interest expense (in thousands). Convertible Senior Notes includes both the 2020 Notes and the 2024 Notes. Three Months Ended Six Months Ended December 31, December 31, 2017 2016 2017 2016 Notes payable Simple interest $ 126 $ 127 $ 252 $ 166 Fees paid — 123 — 241 Total interest expense on the notes payable at fair value 126 250 252 407 Comerica Term Loan (1) Simple interest — 117 — 247 Amortization of prepaid fees for letters of credit — — — 2 Total interest expense on the Comerica term loan — 117 — 249 Silicon Valley Bank Term Loan Simple interest 87 7 180 7 Amortization of prepaid fees for line of credit 44 — 85 — Amortization of debt discount 81 — 162 — Total interest expense on the Silicon Valley Bank term loan 212 7 427 7 Convertible Senior Notes Contractual interest 896 992 1,889 1,984 Amortization of debt discount 1,512 1,648 3,291 3,255 Amortization of debt issuance costs 87 93 187 184 Total interest expense on convertible senior notes 2,495 2,733 5,367 5,423 Total interest expense $ 2,833 $ 3,107 $ 6,046 $ 6,086 (1) Previous term loan that was repaid in December 2016 using proceeds from the Silicon Valley Bank term loan.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	6 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The following tables show the fair value of the Company's financial instruments classified into the fair value hierarchy and measured on a recurring basis on the condensed balance sheets as of December 31, 2017 and June 30, 2017 (in thousands): Fair Value Measurement as of December 31, 2017 Level 1 Level 2 Level 3 Total Assets Current Assets U.S. treasury securities $ 353,901 $ — $ — $ 353,901 Mutual fund securities 320 — — 320 Long-term Assets Mutual fund securities 1,045 — — 1,045 Total assets $ 355,266 $ — $ — $ 355,266 Liabilities Notes payable, at fair value $ — $ — $ 12,700 $ 12,700 Fair Value Measurement as of June 30, 2017 Level 1 Level 2 Level 3 Total Assets Current Assets U.S. treasury securities $ 108,098 $ — $ — $ 108,098 Mutual fund securities 292 — — 292 Long-term Assets Mutual fund securities 732 — — 732 Total assets $ 109,122 $ — $ — $ 109,122 Liabilities Notes payable, at fair value $ — $ — $ 12,600 $ 12,600 The table below provides a rollforward of the changes in fair value of Level 3 financial instruments for the six months ended December 31, 2017 , comprising the Redmile Notes described below (in thousands): Notes Payable at Fair Value Balance at June 30, 2017 $ 12,600 Change in fair value 100 Balance at December 31, 2017 $ 12,700 Redmile Notes To measure the fair value of the principal amount on the Notes issued to Redmile, the Company was required to determine the fair value of the principal amount on the Notes and the conversion feature of the Notes. The Company utilized a Monte Carlo simulation to determine the method of payment of the principal amount by potential outcome and scenario, and applied the income approach to determine the fair value of the Notes, discounting the principal amount due under the Notes by market interest rates under potential scenarios. The Monte Carlo simulation utilized the following assumptions: (i) expected term; (ii) common stock price; (iii) risk-free interest rate; and (iv) expected volatility. The assumptions the Company used in the simulation were based on factors the Company believed that participants would use in pricing the liability components, including market interest rates, credit standing, yield curves, volatilities, and risk-free rates, all of which are defined as Level 3 observable inputs. To measure the fair value of the conversion feature of the Notes issued to Redmile, the Company performed an analysis to estimate the pre-money value of the 797 Subsidiary. The Company then applied the pre-money value of the 797 Subsidiary to the conversion scenarios under the Notes to determine the fair value of the conversion feature. The Company incorporated the estimated volatilities and the risk-free rates on the principal amount of the Notes into the Monte Carlo simulation under each potential scenario and weighted volatility and rates based on the probability of each scenario occurring. Subsequently, the estimated implied interest rates were applied to the principal amount of these Notes under potential scenarios and were weighted based on the probability of each scenario occurring. The fair value of the Notes was impacted by certain unobservable inputs, most significantly management's assumptions regarding the discount rates used, the probabilities of certain scenarios occurring, expected volatility, share price performance, and expected scenario timing. Significant changes to these inputs in isolation or in the aggregate could result in a significantly different fair value measurement.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	6 Months Ended
	Dec. 31, 2017
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS’ EQUITY Common Stock Offering On September 19, 2017, the Company closed an underwritten public offering of 24.1 million shares of its common stock, which included 3.1 million shares of common stock issued upon the exercise in full of the option to purchase additional shares granted to the underwriters in the offering. The shares were sold to the public at an offering price of $10.75 per share. The total net proceeds from the offering were $243.0 million , after underwriting discounts and commissions and offering expenses of approximately $15.7 million . The Company intends to use the net proceeds from this offering to fund research and development efforts, including clinical trials for its proprietary candidates, build and scale its commercial capabilities, and for general working capital and corporate purposes. At-the-Market Equity Offering The Company entered into a Sales Agreement with Cantor Fitzgerald & Co. ("Cantor") dated March 27, 2013, which was subsequently amended to permit the sale by Cantor, acting as its sales agent, of up to $75.0 million in additional shares of the Company's common stock from time to time in an at-the-market offering under the Sales Agreement. All sales of shares have been and will continue to be made pursuant to an effective shelf registration statement on Form S-3 filed with the SEC. The Company pays Cantor a commission of approximately 2% of the aggregate gross proceeds the Company receives from all sales of the Company's common stock under the Sales Agreement. The amended Sales Agreement continues indefinitely until either party terminates the Sales Agreement, which may be done on 10 days prior written notice. The Company received net proceeds on sales under the Sales Agreement of approximately $2.8 million at a weighted average price of $9.02 during the six months ended December 31, 2017 .

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	6 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
SHARE-BASED COMPENSATION	SHARE-BASED COMPENSATION Share-based compensation expense for all equity awards issued pursuant to the Array BioPharma Amended and Restated Stock Option and Incentive Plan (the "Option and Incentive Plan") and for estimated shares to be issued under the Employee Stock Purchase Plan ("ESPP") for the current purchase period was approximately $3.2 million and $2.1 million for the three months ended December 31, 2017 and 2016 , respectively, and $8.8 million and $4.0 million for the six months ended December 31, 2017 and 2016 , respectively, including a $2.5 million charge in the first quarter of fiscal 2018 for accelerated vesting of stock options and RSUs to a departing executive. The Company uses the Black-Scholes option pricing model to estimate the fair value of its share-based awards. In applying this model, the Company uses the following assumptions: • Risk-free interest rate - The Company determines the risk-free interest rate by using a weighted average assumption equivalent to the expected term based on the U.S. Treasury constant maturity rate. • Expected term - The Company estimates the expected term of its options based upon historical exercises and post-vesting termination behavior. • Expected volatility - The Company estimates expected volatility using daily historical trading data of its common stock. • Dividend yield - The Company has never paid dividends and currently have no plans to do so; therefore, no dividend yield is applied. Option Awards The fair value of the Company's option awards were estimated using the assumptions below: Six Months Ended December 31, 2017 2016 Risk-free interest rate 1.6% - 2.04% 1.1% - 2.1% Expected option term in years 3.92 - 4.10 5.5 Expected volatility 66.1% - 67.0% 57.0% - 64.5% Dividend yield 0% 0% Weighted average grant date fair value $5.37 $4.23 The following table summarizes the Company's stock option activity under the Option and Incentive Plan for the six months ended December 31, 2017 : Number of Weighted Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at June 30, 2017 14,844,028 $ 5.57 Granted 3,094,150 $ 10.56 Exercised (2,629,526 ) $ 5.47 Forfeited (388,551 ) $ 7.21 Expired or canceled (10,000 ) $ 11.28 Outstanding balance at December 31, 2017 14,910,101 $ 6.58 7.7 $ 92,791 Vested and expected to vest at December 31, 2017 14,887,879 $ 6.58 7.7 $ 92,652 Exercisable at December 31, 2017 5,906,109 $ 4.83 6.1 $ 47,044 The aggregate intrinsic value in the above table is calculated as the difference between the closing price of the Company's common stock at December 31, 2017 , of $12.80 per share and the exercise price of the stock options that had strike prices below the closing price. The total intrinsic value of all options exercised was $14.8 million during the six months ended December 31, 2017 . The total intrinsic value of all options exercised during the six months ended December 31, 2016 was $0.6 million . As of December 31, 2017 , there was approximately $32.8 million of total unrecognized compensation expense related to the unvested stock options shown in the table above, which is expected to be recognized over a weighted average period of 3.1 years . Restricted Stock Units ("RSUs") The Option and Incentive Plan provides for the issuance of RSUs that each represent the right to receive one share of Array common stock, cash or a combination of cash and stock, typically following achievement of time- or performance-based vesting conditions. The Company's RSU grants that vest subject to continued service over a defined period of time, will typically vest between two to four years, with a percentage vesting on each anniversary date of the grant, or they may be vested in full on the date of grant. Vested RSUs will be settled in shares of common stock upon the vesting date, upon a predetermined delivery date, upon a change in control of Array, or upon the employee leaving Array. All outstanding RSUs may only be settled through the issuance of common stock to recipients, and the Company intends to continue to grant RSUs that may only be settled in stock. RSUs are assigned the value of Array common stock at date of grant, and the grant date fair value is amortized over the applicable vesting period. A summary of the status of the Company's unvested RSUs as of December 31, 2017 and changes during the six months ended December 31, 2017 , is presented below: Number of RSUs Weighted Unvested at June 30, 2017 982,709 $ 6.27 Granted 484,884 $ 10.90 Vested (193,901 ) 7.09 Forfeited (28,952 ) 3.27 Unvested at December 31, 2017 1,244,740 8.02 As of December 31, 2017 , there was $8.2 million of total unrecognized compensation cost related to unvested RSUs granted under the Option and Incentive Plan. The cost is expected to be recognized over a weighted-average period of approximately 3.4 years . The fair market value on the grant date for RSUs that vested during the six months ended December 31, 2017 and 2016 was $1.8 million and $0.5 million , respectively. Employee Stock Purchase Plan The ESPP allows qualified employees (as defined in the ESPP) to purchase shares of the Company's common stock at a price equal to 85% of the lower of (i) the closing price at the beginning of the offering period or (ii) the closing price at the end of the offering period. Effective each January 1, a new 12 -month offering period begins that will end on December 31 of that year. However, if the closing stock price on July 1 is lower than the closing stock price on the preceding January 1, then the original 12 -month offering period terminates, and the purchase rights under the original offering period roll forward into a new six -month offering period that begins July 1 and ends on December 31. As of December 31, 2017 , the Company had 0.9 million shares available for issuance under the ESPP. The Company issued 154 thousand and 282 thousand shares under the ESPP during fiscal 2017 and 2016, respectively.

RELATED PARTY TRANSACTION

RELATED PARTY TRANSACTION	6 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTION	RELATED PARTY TRANSACTIONS The Company is party to a Drug Discovery Collaboration Option Agreement with Mirati pursuant to which the Company is providing certain drug discovery and research activities to Mirati in which the Company has received upfront payments, license fees and reimbursement for research and development services and under which the Company is entitled to receive milestone payments based on achievement of certain milestones, as described in Note 3 - Collaboration and Other Agreements . Dr. Charles Baum, a current member of Array’s Board of Directors, is the President and Chief Executive Officer of Mirati. As described above in Note 4 - Debt - Notes Payable , the Company entered into a Note Purchase Agreement with Redmile and issued Notes to Redmile on September 2, 2016. At that time, affiliates of Redmile held more than 10% of the Company's common stock. As of September 30, 2017, Redmile and its affiliates hold less than 10% of the Company's common stock.

NET LOSS PER SHARE

NET LOSS PER SHARE	6 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
NET LOSS PER SHARE	NET LOSS PER SHARE Basic and diluted loss per common share are computed by dividing net loss by the weighted average number of common shares outstanding during the period. Diluted loss per share includes the determinants of basic net income per share and, in addition, gives effect to the potential dilution that would occur if securities or other contracts to issue common stock were exercised, vested or converted into common stock, unless they are anti-dilutive. Diluted weighted average common shares include common stock potentially issuable under our convertible notes, notes payable at fair value, vested and unvested stock options and unvested RSUs, except where the effect of including them is anti-dilutive. The following table summarizes the net loss per share calculation (in thousands, except per share amount): Three Months Ended Six Months Ended December 31, December 31, 2017 2016 2017 2016 Net loss - basic and diluted $ (34,053 ) $ (23,301 ) $ (72,047 ) $ (51,909 ) Weighted average shares outstanding - basic and diluted 199,852 168,127 187,312 156,613 Per share data: Basic and diluted $ (0.17 ) $ (0.14 ) $ (0.38 ) $ (0.33 ) For the periods where the Company reported losses, all common stock equivalents are excluded from the computation of diluted loss per share, since the result would be anti-dilutive. Common stock equivalents not included in the calculations of diluted loss per share because to do so would have been anti-dilutive, include the following (amounts in thousands): December 31, 2017 2016 2.625% convertible senior notes 8,156 — 3.00% convertible senior notes — 18,762 Stock options 14,910 14,500 RSUs 1,245 1,116 Total anti-dilutive common stock equivalents excluded from diluted loss per share calculation 24,311 34,378

SUBSEQUENT EVENT

SUBSEQUENT EVENT	6 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Event	SUBSEQUENT EVENT On January 3, 2018, the Company entered into a License Agreement (the “License Agreement”) with ASLAN Pharmaceuticals Pte. Ltd., a Singapore corporation (“ASLAN”), pursuant to which the Company granted ASLAN full global rights to develop, manufacture and commercialize varlitinib (ARRY-543), a HER2 / EGFR inhibitor invented by Array. The License Agreement replaces and supersedes the Collaboration and License Agreement dated July 12, 2011, between the Company and ASLAN in which ASLAN was responsible for the development of varlitinib to proof-of-concept and for the identification of a partner to complete phase 3 development and commercialization of varlitinib. The terms of the new License Agreement grant ASLAN exclusive global rights to commercialize and sublicense varlitinib. Array received a $12.0 million upfront payment and is also entitled to receive a further upfront payment of between $11.0 million and $12.0 million within the next 12 months, together with up to $30.0 million of development, $20.0 million of regulatory and $55.0 million of commercial milestone payments, as well as tiered low double-digit royalties as a percentage of any net sales of varlitinib.

OVERVIEW, BASIS OF PRESENTATI17

OVERVIEW, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	6 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC") for interim reporting and, as permitted under those rules, do not include all of the disclosures required by U.S. generally accepted accounting principles ("U.S. GAAP") for complete financial statements. The unaudited condensed consolidated financial statements reflect all normal and recurring adjustments that, in the opinion of management, are necessary to present fairly the Company's financial position, results of operations and cash flows for the interim periods presented. Operating results for an interim period are not necessarily indicative of the results that may be expected for a full year. The Company's management performed an evaluation of its activities through the date of filing of this Quarterly Report on Form 10-Q. These unaudited condensed consolidated financial statements should be read in conjunction with the Company's audited financial statements and the notes thereto for the fiscal year ended June 30, 2017 , included in its Annual Report on Form 10-K filed with the SEC on August 11, 2017, from which the Company derived its balance sheet data as of June 30, 2017 .
Segment Reporting	The Company operates in one reportable segment and, accordingly, no segment disclosures have been presented herein.
Use of Estimates	The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires the Company's management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and related disclosure of contingent assets and liabilities. Management bases its estimates on the Company's historical experience and on various other assumptions that it believes are reasonable under the circumstances. These estimates are the basis for the Company's judgments about the carrying values of assets and liabilities, which in turn may impact its reported revenue and expenses. The Company's actual results could differ significantly from these estimates under different assumptions or conditions. The Company believes its condensed consolidated financial statements are most significantly impacted by the following accounting estimates and judgments: (i) identifying deliverables under collaboration and license agreements involving multiple elements and determining whether such deliverables are separable from other aspects of the contractual relationship; (ii) estimating the selling price of deliverables for the purpose of allocating arrangement consideration for revenue recognition; (iii) estimating the periods over which the allocated consideration for deliverables is recognized; (iv) estimating accrued outsourcing costs for clinical trials and preclinical testing; and (v) estimating fair value of the notes payable.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the FASB issued Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers , which requires entities to recognize revenue from the transfer of promised goods or services to customers based on the amount of the consideration to which the entity expects to be entitled to receive in exchange for those goods or services. The new guidance also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. In March 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations . The purpose of ASU No. 2016-08 is to clarify the implementation of guidance relating to principal versus agent considerations. For public entities, the amendments in ASU No. 2016-08 are effective for interim and annual reporting periods beginning after December 15, 2017. The Company is currently evaluating the impact of ASU No. 2016-08 on its condensed consolidated financial statements and related disclosures. The FASB subsequently issued ASU No. 2016-10, Revenue from Contracts with Customer (Topic 606) Identifying Performance Obligations and Licensing, to address issues arising from implementation of the new revenue recognition standard. ASU 2014-09 and ASU 2016-10 are effective for interim and annual periods beginning July 1, 2018, and may be adopted earlier, but not before July 1, 2017. The revenue standards are required to be adopted by taking either a full retrospective or a modified retrospective approach. The Company has not elected early adoption and has not concluded on an adoption method. The Company is continuing to assess the impact of the new guidance on its accounting policies and procedures and is evaluating the new requirements as applied to existing revenue contracts. While this assessment is still in progress, the Company believes the most significant impact will relate to the timing of collaboration revenues, where the recognition of variable consideration such as milestone payments may be accelerated. In conjunction with its continuing assessment of the impact of the new guidance, the Company is also evaluating its method of adoption and reviewing and updating its internal controls over financial reporting to ensure that information required to implement the new standard is appropriately captured and recorded. The Company will implement any changes as required to facilitate adoption of the new guidance beginning in the first quarter of fiscal 2019. In addition, the Company continues to monitor additional changes, modifications, clarifications or interpretations undertaken by the FASB or others, which may impact its current conclusions. In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities . ASU No. 2016-01 requires equity investments to be measured at fair value with changes in fair value recognized in net income; simplifies the impairment assessment of equity investments without readily determinable fair values by requiring a qualitative assessment to identify impairment; eliminates the requirement for public business entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the balance sheet; requires public business entities to use the exit price notion when measuring the fair value of financial instruments for disclosure purposes; requires an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; requires separate presentation of financial assets and financial liabilities by measurement category and form of financial assets on the balance sheet or the accompanying notes to the condensed consolidated financial statements and clarifies that an entity should evaluate the need for a valuation allowance on a deferred tax asset related to available-for-sale securities in combination with the entity’s other deferred tax assets. ASU No. 2016-01 is effective for financial statements issued for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The Company is currently evaluating the impact that ASU No. 2016-01 will have on its condensed consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) which supersedes FASB ASC Topic 840, Leases (Topic 840) and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than twelve months regardless of classification. Leases with a term of twelve months or less will be accounted for similar to existing guidance for operating leases. The standard is effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted upon issuance. The Company is currently evaluating the impact that ASU 2016-02 will have on its condensed consolidated financial statements and related disclosures. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (ASU 2016-13). ASU 2016-13 requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. ASU 2016-13 limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The new standard will be effective for the Company on January 1, 2020. Early adoption will be available on January 1, 2019. The Company is currently evaluating the effect that ASU 2016-13 will have on its condensed consolidated financial statements and related disclosures. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) . This amendment will provide guidance on the presentation and classification of specific cash flow items to improve consistency within the statement of cash flows. ASU 2016-15 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2017, with early adoption permitted. The Company is evaluating the effect that ASU 2016-15 will have on its condensed consolidated financial statements and related disclosures. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230) Restricted Cash . The new guidance requires that the reconciliation of the beginning-of-period and end-of-period amounts shown in the statement of cash flows include restricted cash and restricted cash equivalents. If restricted cash is presented separately from cash and cash equivalents on the balance sheet, companies will be required to reconcile the amounts presented on the statement of cash flows to the amounts on the balance sheet. Companies will also need to disclose information about the nature of the restrictions. The guidance is effective for fiscal years beginning after December 15, 2017, and interim periods within those fiscal years. The Company does not anticipate ASU 2016-18 will have a material impact on its condensed consolidated financial statements upon adoption. In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805) Clarifying the Definition of a Business . The amendments in this ASU clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. The definition of a business affects many areas of accounting including acquisitions, disposals, goodwill, and consolidation. The guidance is effective for annual periods beginning after December 15, 2017, including interim periods within those periods. The Company does not anticipate ASU 2017-01 will have a material impact on its condensed consolidated financial statements upon adoption. In May 2017, the FASB issued ASU 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting , 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. It is effective prospectively for the annual period ending June 30, 2019 and interim periods within that annual period. Early adoption is permitted. The Company does not expect ASU 2017-09 will have a significant impact on its condensed consolidated financial statements upon adoption. In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480) and Derivatives and Hedging (Topic 815): I. Accounting for Certain Financial Instruments with Down Round Features; II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception . Part I of this update addresses the complexity of accounting for certain financial instruments with down round features. Down round features are features of certain equity-linked instruments (or embedded features) that result in the strike price being reduced on the basis of the pricing of future equity offerings. Current accounting guidance creates cost and complexity for entities that issue financial instruments (such as warrants and convertible instruments) with down round features that require fair value measurement of the entire instrument or conversion option. Part II of this update addresses the difficulty of navigating Topic 480, Distinguishing Liabilities from Equity , because of the existence of extensive pending content in the FASB Accounting Standards Codification. This pending content is the result of the indefinite deferral of accounting requirements about mandatorily redeemable financial instruments of certain nonpublic entities and certain mandatorily redeemable noncontrolling interests. The amendments in Part II of this update do not have an accounting effect. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018. The Company is evaluating the effect that ASU 2017-11 will have on its condensed consolidated financial statements and related disclosures.

OVERVIEW, BASIS OF PRESENTATI18

OVERVIEW, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	6 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of concentration of revenue	The following counterparties contributed greater than 10% of the Company's total revenue during at least one of the periods set forth below. The revenue from these counterparties as a percentage of total revenue was as follows: Three Months Ended Six Months Ended December 31, December 31, 2017 2016 2017 2016 Novartis Pharmaceuticals 53.1 % 63.8 % 56.4 % 71.8 % Asahi Kasei 23.0 % 2.2 % 14.9 % 2.2 % Pierre Fabre 10.5 % 7.0 % 11.8 % 6.7 % Loxo Oncology 5.7 % 18.6 % 8.0 % 13.5 % 92.3 % 91.6 % 91.1 % 94.2 %
Schedule of revenue by geographic area	The following table details revenue by geographic area based on the country in which the Company's counterparties are located (in thousands): Three Months Ended Six Months Ended December 31, December 31, 2017 2016 2017 2016 North America $ 4,662 $ 9,528 $ 10,163 $ 13,626 Europe 26,852 34,035 49,148 68,341 Asia Pacific 10,704 960 12,653 1,827 Total revenue $ 42,218 $ 44,523 $ 71,964 $ 83,794

MARKETABLE SECURITIES (Tables)

MARKETABLE SECURITIES (Tables)	6 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Schedule of marketable securities	Marketable securities consisted of the following as of December 31, 2017 and June 30, 2017 (in thousands): December 31, 2017 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Short-term available-for-sale securities: U.S. treasury securities $ 354,577 $ — $ (676 ) $ 353,901 Mutual fund securities 320 — — 320 354,897 — (676 ) 354,221 Long-term available-for-sale securities: Mutual fund securities 1,045 — — 1,045 1,045 — — 1,045 Total $ 355,942 $ — $ (676 ) $ 355,266 June 30, 2017 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Short-term available-for-sale securities: U.S. treasury securities $ 108,174 $ — $ (76 ) $ 108,098 Mutual fund securities 292 — — 292 108,466 — (76 ) 108,390 Long-term available-for-sale securities: Mutual fund securities 732 — — 732 732 — — 732 Total $ 109,198 $ — $ (76 ) $ 109,122
Schedule of amortized cost and estimated fair value of available-for-sale securities by contractual maturity	As of December 31, 2017 , the amortized cost and estimated fair value of available-for-sale securities by contractual maturity were as follows (in thousands): Amortized Fair Cost Value Due in one year or less $ 354,577 $ 353,901 Total $ 354,577 $ 353,901

COLLABORATION AND OTHER AGREE20

COLLABORATION AND OTHER AGREEMENTS (Tables)	6 Months Ended
	Dec. 31, 2017
Collaboration and Other Agreements [Abstract]
Schedule of total revenue	The following table summarizes total revenue recognized for the periods indicated (in thousands): Three Months Ended Six Months Ended December 31, December 31, 2017 2016 2017 2016 Reimbursement revenue Novartis (1) $ 22,395 $ 27,948 $ 40,587 $ 59,269 Collaboration and other revenue Pierre Fabre 3,674 2,375 7,023 4,153 Loxo 2,395 1,938 4,653 4,805 Mirati 1,422 875 2,811 1,750 Amgen 500 — 1,000 — Asahi Kasei 262 361 730 628 Cascadian 75 15 106 52 Ono 87 — 87 — Celgene 60 — 68 — Novartis (2) — 450 — 900 Other partners 33 16 38 31 Total collaboration and other revenue 8,508 6,030 16,516 12,319 License and milestone revenue Asahi Kasei 9,437 600 10,000 1,200 Ono 919 — 1,837 — Pierre Fabre 750 750 1,500 1,500 Loxo — 6,362 1,107 6,465 Mirati 209 208 417 416 Roche — 2,500 — 2,500 Other Partners — 125 — 125 Total license and milestone revenue 11,315 10,545 14,861 12,206 Total revenue $ 42,218 $ 44,523 $ 71,964 $ 83,794 (1) Consists of reimbursable expenses incurred and accrued as reimbursement revenue that are receivable under the Transition Agreements with Novartis. (2) Represents the recognition of revenue that was deferred from the consideration received in March 2015 upon the effective date of the Termination and Asset Transfer Agreement with Novartis relating to binimetinib.
Schedule of deferred revenue	Deferred revenue balances were as follows for the dates indicated (in thousands): December 31, June 30, 2017 2017 Ono $ 29,392 $ 31,229 Pierre Fabre 23,895 25,395 Asahi Kasei — 9,000 Mirati 2,750 4,167 Loxo 3,203 2,690 Amgen 1,000 2,000 Total deferred revenue 60,240 74,481 Less: Current portion (13,419 ) (17,156 ) Deferred revenue, long-term portion $ 46,821 $ 57,325

DEBT (Tables)

DEBT (Tables)	6 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of debt	Outstanding debt consists of the following (in thousands): December 31, June 30, 2017 2017 Notes Payable at fair value $ 12,700 $ 12,600 2020 convertible senior notes $ — $ 132,250 2024 convertible senior notes 126,060 — Silicon Valley Bank term loan (1) 16,200 16,200 Long-term debt, gross 142,260 148,450 Less: Unamortized debt discount and fees (48,996 ) (27,145 ) Long-term debt, net $ 93,264 $ 121,305 (1) Outstanding debt owed to Silicon Valley Bank includes a $1.2 million final payment fee.
Schedule of interest expense	The following table shows the details of the Company's interest expense for all of its debt arrangements outstanding during the periods presented, including contractual interest, and amortization of debt discount, debt issuance costs and loan transaction fees that were charged to interest expense (in thousands). Convertible Senior Notes includes both the 2020 Notes and the 2024 Notes. Three Months Ended Six Months Ended December 31, December 31, 2017 2016 2017 2016 Notes payable Simple interest $ 126 $ 127 $ 252 $ 166 Fees paid — 123 — 241 Total interest expense on the notes payable at fair value 126 250 252 407 Comerica Term Loan (1) Simple interest — 117 — 247 Amortization of prepaid fees for letters of credit — — — 2 Total interest expense on the Comerica term loan — 117 — 249 Silicon Valley Bank Term Loan Simple interest 87 7 180 7 Amortization of prepaid fees for line of credit 44 — 85 — Amortization of debt discount 81 — 162 — Total interest expense on the Silicon Valley Bank term loan 212 7 427 7 Convertible Senior Notes Contractual interest 896 992 1,889 1,984 Amortization of debt discount 1,512 1,648 3,291 3,255 Amortization of debt issuance costs 87 93 187 184 Total interest expense on convertible senior notes 2,495 2,733 5,367 5,423 Total interest expense $ 2,833 $ 3,107 $ 6,046 $ 6,086 (1) Previous term loan that was repaid in December 2016 using proceeds from the Silicon Valley Bank term loan.

FAIR VALUE MEASUREMENTS FAIR VA

FAIR VALUE MEASUREMENTS FAIR VALUE MEASUREMENTS (Tables)	6 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair value hierarchy, financial instruments measured at fair value on a recurring basis	The following tables show the fair value of the Company's financial instruments classified into the fair value hierarchy and measured on a recurring basis on the condensed balance sheets as of December 31, 2017 and June 30, 2017 (in thousands): Fair Value Measurement as of December 31, 2017 Level 1 Level 2 Level 3 Total Assets Current Assets U.S. treasury securities $ 353,901 $ — $ — $ 353,901 Mutual fund securities 320 — — 320 Long-term Assets Mutual fund securities 1,045 — — 1,045 Total assets $ 355,266 $ — $ — $ 355,266 Liabilities Notes payable, at fair value $ — $ — $ 12,700 $ 12,700
Rollforward of changes in fair value of Level 3 financial instruments	The table below provides a rollforward of the changes in fair value of Level 3 financial instruments for the six months ended December 31, 2017 , comprising the Redmile Notes described below (in thousands): Notes Payable at Fair Value Balance at June 30, 2017 $ 12,600 Change in fair value 100 Balance at December 31, 2017 $ 12,700

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	6 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of fair value assumptions	The fair value of the Company's option awards were estimated using the assumptions below: Six Months Ended December 31, 2017 2016 Risk-free interest rate 1.6% - 2.04% 1.1% - 2.1% Expected option term in years 3.92 - 4.10 5.5 Expected volatility 66.1% - 67.0% 57.0% - 64.5% Dividend yield 0% 0% Weighted average grant date fair value $5.37 $4.23
Summary of stock option activity	The following table summarizes the Company's stock option activity under the Option and Incentive Plan for the six months ended December 31, 2017 : Number of Weighted Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at June 30, 2017 14,844,028 $ 5.57 Granted 3,094,150 $ 10.56 Exercised (2,629,526 ) $ 5.47 Forfeited (388,551 ) $ 7.21 Expired or canceled (10,000 ) $ 11.28 Outstanding balance at December 31, 2017 14,910,101 $ 6.58 7.7 $ 92,791 Vested and expected to vest at December 31, 2017 14,887,879 $ 6.58 7.7 $ 92,652 Exercisable at December 31, 2017 5,906,109 $ 4.83 6.1 $ 47,044
Summary of status of non-vested shares of RSUs	A summary of the status of the Company's unvested RSUs as of December 31, 2017 and changes during the six months ended December 31, 2017 , is presented below: Number of RSUs Weighted Unvested at June 30, 2017 982,709 $ 6.27 Granted 484,884 $ 10.90 Vested (193,901 ) 7.09 Forfeited (28,952 ) 3.27 Unvested at December 31, 2017 1,244,740 8.02

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	6 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Computation of earnings per share	The following table summarizes the net loss per share calculation (in thousands, except per share amount): Three Months Ended Six Months Ended December 31, December 31, 2017 2016 2017 2016 Net loss - basic and diluted $ (34,053 ) $ (23,301 ) $ (72,047 ) $ (51,909 ) Weighted average shares outstanding - basic and diluted 199,852 168,127 187,312 156,613 Per share data: Basic and diluted $ (0.17 ) $ (0.14 ) $ (0.38 ) $ (0.33 )
Anti-dilutive common stock equivalents	Common stock equivalents not included in the calculations of diluted loss per share because to do so would have been anti-dilutive, include the following (amounts in thousands): December 31, 2017 2016 2.625% convertible senior notes 8,156 — 3.00% convertible senior notes — 18,762 Stock options 14,910 14,500 RSUs 1,245 1,116 Total anti-dilutive common stock equivalents excluded from diluted loss per share calculation 24,311 34,378

OVERVIEW, BASIS OF PRESENTATI25

OVERVIEW, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Concentration of Revenue (Details) - Sales - Customer Concentration Risk	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Concentration Risk [Line Items]
Concentration risk, percentage	92.00%	92.00%	91.00%	94.00%
Novartis Pharmaceuticals
Concentration Risk [Line Items]
Concentration risk, percentage	53.00%	64.00%	56.00%	72.00%
Asahi Kasei
Concentration Risk [Line Items]
Concentration risk, percentage	23.00%	2.00%	15.00%	2.00%
Pierre Fabre
Concentration Risk [Line Items]
Concentration risk, percentage	10.00%	7.00%	12.00%	7.00%
Loxo Oncology
Concentration Risk [Line Items]
Concentration risk, percentage	6.00%	19.00%	8.00%	14.00%

OVERVIEW, BASIS OF PRESENTATI26

OVERVIEW, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Concentration Risk [Line Items]
Total revenue	$ 42,218	$ 44,523	$ 71,964	$ 83,794
North America
Concentration Risk [Line Items]
Total revenue	4,662	9,528	10,163	13,626
Europe
Concentration Risk [Line Items]
Total revenue	26,852	34,035	49,148	68,341
Asia Pacific
Concentration Risk [Line Items]
Total revenue	$ 10,704	$ 960	$ 12,653	$ 1,827

OVERVIEW, BASIS OF PRESENTATI27

OVERVIEW, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Additional Information (Details) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2015USD ($)
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Number of reportable segments | segment			1
Accumulated deficit	$ (990,708)		$ (990,708)		$ (918,661)
Net income (loss)	$ (34,053)	$ (23,301)	$ (72,047)	$ (51,909)			$ 9,400
Customer Concentration Risk | Novartis Pharmaceuticals | Accounts Receivable
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Concentration risk, percentage			75.00%		70.00%
Customer Concentration Risk | Pierre Fabre | Accounts Receivable
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Concentration risk, percentage			12.00%		7.00%
Accumulated Deficit
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Net income (loss)			$ (72,047)		$ (116,800)	$ (92,800)

MARKETABLE SECURITIES - Schedul

MARKETABLE SECURITIES - Schedule Of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jun. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 355,942	$ 109,198
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(676)	(76)
Fair value	355,266	109,122
Short-term available-for-sale securities:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	354,897	108,466
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(676)	(76)
Fair value	354,221	108,390
Short-term available-for-sale securities: | U.S. treasury securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	354,577	108,174
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(676)	(76)
Fair value	353,901	108,098
Short-term available-for-sale securities: | Mutual fund securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	320	292
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair value	320	292
Long-term available-for-sale securities:
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,045	732
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair value	1,045	732
Long-term available-for-sale securities: | Mutual fund securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,045	732
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair value	$ 1,045	$ 732

MARKETABLE SECURITIES - Sched29

MARKETABLE SECURITIES - Schedule of Amortized Cost And Estimated Fair Value (Details) $ in Thousands	Dec. 31, 2017USD ($)
Amortized Cost
Due in one year or less	$ 354,577
Amortized Cost	354,577
Fair Value
Due in one year or less	353,901
Fair Value	$ 353,901

MARKETABLE SECURITIES - Additio

MARKETABLE SECURITIES - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jun. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ 355,266	$ 109,122
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ 355,300	$ 109,100

COLLABORATION AND OTHER AGREE31

COLLABORATION AND OTHER AGREEMENTS - Schedule of Total Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Reimbursement revenue	$ 22,395	$ 27,948	$ 40,587	$ 59,269
Collaboration and other revenue	8,508	6,030	16,516	12,319
License and milestone revenue	11,315	10,545	14,861	12,206
Total revenue	42,218	44,523	71,964	83,794
Novartis Pharmaceuticals
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Reimbursement revenue	22,395	27,948	40,587	59,269
Collaboration and other revenue	0	450	0	900
Pierre Fabre
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Collaboration and other revenue	3,674	2,375	7,023	4,153
License and milestone revenue	750	750	1,500	1,500
Loxo Oncology
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Collaboration and other revenue	2,395	1,938	4,653	4,805
License and milestone revenue	0	6,362	1,107	6,465
Mirati
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Collaboration and other revenue	1,422	875	2,811	1,750
License and milestone revenue	209	208	417	416
Amgen
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Collaboration and other revenue	500	0	1,000	0
Asahi Kasei
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Collaboration and other revenue	262	361	730	628
License and milestone revenue	9,437	600	10,000	1,200
Cascadian
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Collaboration and other revenue	75	15	106	52
Ono
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Collaboration and other revenue	87	0	87	0
License and milestone revenue	919	0	1,837	0
Celgene
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Collaboration and other revenue	60	0	68	0
Other partners
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
Collaboration and other revenue	33	16	38	31
License and milestone revenue	0	125	0	125
Roche
Collaborative Arrangements and Non-collaborative Arrangements [Line Items]
License and milestone revenue	$ 0	$ 2,500	$ 0	$ 2,500

COLLABORATION AND OTHER AGREE32

COLLABORATION AND OTHER AGREEMENTS - Schedule of Deferred Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jun. 30, 2017
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 60,240	$ 74,481
Less: Current portion	(13,419)	(17,156)
Deferred revenue, long-term portion	46,821	57,325
Ono
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	29,392	31,229
Pierre Fabre
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	23,895	25,395
Asahi Kasei
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	0	9,000
Mirati
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	2,750	4,167
Loxo Oncology
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	3,203	2,690
Amgen
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 1,000	$ 2,000

COLLABORATION AND OTHER AGREE33

COLLABORATION AND OTHER AGREEMENTS - Additional Information (Details) - 6 months ended Dec. 31, 2017	USD ($)indicationmilestone	JPY (¥)indicationmilestone
Collaboration and Other Agreements, by Type [Line Items]
Number of milestones	8	8
Foreign currency exchange rate translation	112.36	112.36
Pierre Fabre | Regulatory milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 25,000,000
Number of milestones	2	2
Number of specified indications | indication	2	2
Pierre Fabre | Commercial milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 390,000,000
Number of milestones	7	7
Ono | Regulatory milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments	$ 44,500,000	¥ 5,000,000,000
Ono | Commercial milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments	$ 93,450,000	¥ 10,500,000,000
Number of milestones	5	5
Ono | Developmental milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments	$ 16,020,000	¥ 1,800,000,000
Number of milestones	4	4
Mirati | Commercial milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 674,000,000
Number of milestones	14	14
Mirati | Developmental milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 18,500,000
Number of milestones	8	8
Loxo Oncology | Commercial milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 625,000,000
Number of milestones	22	22
Loxo Oncology | Developmental milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 14,000,000
Number of milestones	4	4
Asahi Kasei | Regulatory milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 10,000,000
Number of milestones	3	3
Asahi Kasei | Commercial milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 52,500,000
Number of milestones	4	4
Amgen
Collaboration and Other Agreements, by Type [Line Items]
Potential development services revenue | $	$ 3,000,000
Term of agreement	2 years
Amgen | Commercial milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 140,000,000
Number of milestones	4	4
Amgen | Developmental milestones
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 14,000,000
Number of milestones	2	2
AstraZeneca | Commercial milestones | Selumetinib
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 34,000,000
Number of milestones	3	3
AstraZeneca | Developmental milestones | Selumetinib
Collaboration and Other Agreements, by Type [Line Items]
Potential milestone payments | $	$ 36,000,000
Number of milestones	9	9

DEBT - Schedule of Debt (Detail

DEBT - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jun. 30, 2017	Dec. 22, 2016
Debt Instrument [Line Items]
Notes Payable at fair value	$ 12,700	$ 12,600
Long-term debt, gross	142,260	148,450
Less: Unamortized debt discount and fees	(48,996)	(27,145)
Long-term debt, net	93,264	121,305
Convertible Senior Notes | 2020 convertible senior notes
Debt Instrument [Line Items]
Long-term debt, gross	0	132,250
Convertible Senior Notes | 2024 convertible senior notes
Debt Instrument [Line Items]
Long-term debt, gross	126,060	0
Line of Credit | Term loan | SVB credit facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 16,200	$ 16,200
Line of Credit | Term loan | SVB credit facility | Silicon Valley Bank
Debt Instrument [Line Items]
Exit fee due upon redemption			$ 1,200

DEBT - Notes Payable (Details)

DEBT - Notes Payable (Details) - USD ($)	Aug. 07, 2017	Sep. 02, 2016	Dec. 31, 2016	Dec. 31, 2017	Aug. 06, 2017	Jun. 30, 2017
Short-term Debt [Line Items]
Notes payable, at fair value				$ 12,700,000		$ 12,600,000
Redmile notes payable | Notes payable
Short-term Debt [Line Items]
Exit fee due upon redemption	$ 5,000,000				$ 3,000,000
Exit fee payable upon repayment of notes, percentage	50.00%
Redmile notes payable | Convertible debt
Short-term Debt [Line Items]
Fair value option upfront costs and fees			$ 200,000
Event of default, percentage of purchase price payable		5.00%
Notes payable | Note purchase agreement
Short-term Debt [Line Items]
Aggregate principal amount		$ 10,000,000
Stated interest rate		5.00%
Preferred stock financing gross proceeds threshold		$ 10,000,000
Conversion to shares of capital stock, percentage of purchase price if closed before March 1, 2017		80.00%
Conversion to shares of capital stock, percentage of purchase price if closed after March 1, 2017		70.00%
Pre-money valuation of subsidiary		$ 75,000,000
Conversion price, threshold consecutive trading days		10 days
Shares issues upon conversion, aggregate cap on outstanding shares		19.99%
Event of sale of subsidiary, amount due to note holders		$ 20,000,000
Event of sale of subsidiary, due to note holders, percentage of consideration received		15.00%
Event of sale of subsidiary, aggregate cap on amount due to note holders		$ 100,000,000
Event of license agreement, percentage due to note holders under initial milestone		50.00%
Event of license agreement, initial milestone threshold for amount due to note holders		$ 50,000,000
Event of license agreement, percentage due to note holders under subsequent milestone		20.00%
Event of license agreement, aggregate cap on amount due to note holders		$ 100,000,000
Event of change in control or sale of assets, cash payment due under option one		40,000,000
Event of change in control or sale of asset, cash payment due under option two		25,000,000
Notes payable, at fair value	$ 12,000,000	$ 10,000,000		$ 12,700,000

DEBT - Credit Facilities (Detai

DEBT - Credit Facilities (Details)	Dec. 22, 2016USD ($)installment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Debt terminated, repayment of amount outstanding		$ 0	$ 14,550,000
Term loan | Line of Credit | Comerica Bank | Comerica term loan
Debt Instrument [Line Items]
Debt terminated, repayment of amount outstanding	$ 14,600,000
Term loan | Line of Credit | Silicon Valley Bank | SVB credit facility
Debt Instrument [Line Items]
Maximum borrowing capacity	15,000,000
Exit fee due upon redemption	$ 1,200,000
Fee for prepayment or acceleration if occurs on or prior to the first anniversary of the Effective Date	2.00%
Fee for prepayment or acceleration if occurs after the first anniversary of the Effective Date	1.00%
Term loan | Line of Credit | Silicon Valley Bank | SVB credit facility | Prime Rate
Debt Instrument [Line Items]
Spread on variable interest rate	2.00%
Spread on variable interest rate, floor	0.00%
Interest rate at end of period		2.50%
Term of facility	36 months
Letter of credit | Line of Credit | Silicon Valley Bank | SVB credit facility
Debt Instrument [Line Items]
Amount outstanding	$ 2,900,000
Revolving line of credit | Line of Credit | Silicon Valley Bank | SVB credit facility
Debt Instrument [Line Items]
Maximum borrowing capacity	5,000,000
Commitment fee	$ 50,000
Commitment fee, number of installments | installment	5
Unused revolving line facility fee	0.20%
Final payment fee	8.00%
Fee for prepayment or acceleration if occurs on or prior to the first anniversary of the Effective Date	2.00%
Fee for prepayment or acceleration if occurs after the first anniversary of the Effective Date	1.00%
Minimum liquidity ratio	2
Deposit required in event of default, percent of face amount of undrawn letters of credit	105.00%

DEBT - Convertible Senior Notes

DEBT - Convertible Senior Notes (Details) $ / shares in Units, $ in Thousands	Dec. 01, 2017USD ($)trading_day$ / shares	Jun. 10, 2013USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2017USD ($)shares	Dec. 31, 2016USD ($)	Nov. 20, 2017
Debt Instrument [Line Items]
Proceeds from Silicon Valley Bank term loan					$ 0	$ 15,000
Loss on extinguishment and conversion of Notes			$ 6,457	$ 0	$ 6,457	$ 0
Convertible Senior Notes | 2020 convertible senior notes
Debt Instrument [Line Items]
Aggregate principal amount		$ 132,300
Stated interest rate		3.00%
Proceeds from Silicon Valley Bank term loan		$ 128,000
Extinguishment of 2020 notes (in shares) | shares					7,955,560
Convertible notes, liability component	$ 6,200
Converted shares (in shares) | shares					913,368
Equity issuance costs recorded as an offset to additional paid-in capital		$ 1,600
Convertible Senior Notes | 2024 convertible senior notes
Debt Instrument [Line Items]
Stated interest rate	2.625%						2.625%
Aggregate of principal amount			126,100		$ 126,100
Convertible notes, liability component	$ 80,400
Threshold trading days | trading_day	20
Threshold consecutive trading days | trading_day	30
Threshold percentage of stock price trigger	130.00%
Threshold consecutive trading days, number of days immediately prior to redemption notice date	5 days
Maximum threshold percentage of stock price trigger	98.00%
Conversion ratio	0.0646987
Conversion price (in dollars per share) | $ / shares	$ 15.46
Percentage of principal amount of convertible debt required to be repurchased upon qualifying change in control or termination of trading of common stock	100.00%
Redemption price, percentage of principal amount to be redeemed	100.00%
Minimum percent owned of convertible debt	25.00%
Percentage of convertible note due in default event	100.00%
Percentage of convertible note due in bankruptcy or insolvency event	100.00%
Effective interest rate	9.75%
Convertible notes, equity component	$ 45,700
Underwriting discount and estimated offering expense	4,300
Unamortized debt issuance costs			2,700		2,700
Convertible Senior Notes | 2024 convertible senior notes | Other noncurrent assets
Debt Instrument [Line Items]
Underwriting discount and offering expenses	$ 2,700
Convertible Senior Notes | 2024 convertible senior notes | Level 2
Debt Instrument [Line Items]
Fair value of notes			144,400		$ 144,400
Convertible debt | Convertible Senior Notes | 2020 convertible senior notes
Debt Instrument [Line Items]
Loss on extinguishment and conversion of Notes			$ 6,500

DEBT - Summary of Interest Expe

DEBT - Summary of Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 01, 2017	Nov. 20, 2017
Debt Instrument [Line Items]
Amortization of prepaid fees for letters of credit and debt issuance costs			$ 0	$ 240
Total interest expense	$ 2,833	$ 3,107	6,046	6,086
Line of Credit | Comerica term loan | Term loan
Debt Instrument [Line Items]
Simple and contractual interest	0	117	0	247
Amortization of prepaid fees for letters of credit and debt issuance costs	0	0	0	2
Total interest expense	0	117	0	249
Line of Credit | Silicon Valley Bank Term Loan | Term loan
Debt Instrument [Line Items]
Simple and contractual interest	87	7	180	7
Amortization of prepaid fees for letters of credit and debt issuance costs	44	0	85	0
Amortization of debt discount	81	0	162	0
Total interest expense	212	7	427	7
Convertible Senior Notes
Debt Instrument [Line Items]
Simple and contractual interest	896	992	1,889	1,984
Amortization of prepaid fees for letters of credit and debt issuance costs	87	93	187	184
Amortization of debt discount	1,512	1,648	3,291	3,255
Total interest expense	2,495	2,733	5,367	5,423
Convertible Senior Notes | 2024 convertible senior notes
Debt Instrument [Line Items]
Stated interest rate					2.625%	2.625%
Notes payable | Notes payable
Debt Instrument [Line Items]
Simple and contractual interest	126	127	252	166
Fees paid	0	123	0	241
Total interest expense	$ 126	$ 250	$ 252	$ 407

FAIR VALUE MEASUREMENTS - Sched

FAIR VALUE MEASUREMENTS - Schedule of Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jun. 30, 2017
Current Assets
Marketable securities	$ 354,221	$ 108,390
Long-term Assets
Marketable securities	1,045	732
Total assets	355,266	109,122
Liabilities
Notes payable, at fair value	12,700	12,600
Recurring | Level 1
Long-term Assets
Total assets	355,266	109,122
Liabilities
Notes payable, at fair value	0	0
Recurring | Level 2
Long-term Assets
Total assets	0	0
Liabilities
Notes payable, at fair value	0	0
Recurring | Level 3
Long-term Assets
Total assets	0	0
Liabilities
Notes payable, at fair value	12,700	12,600
U.S. treasury securities
Current Assets
Marketable securities	353,901	108,098
U.S. treasury securities | Recurring | Level 1
Current Assets
Marketable securities	353,901	108,098
U.S. treasury securities | Recurring | Level 2
Current Assets
Marketable securities	0	0
U.S. treasury securities | Recurring | Level 3
Current Assets
Marketable securities	0	0
Mutual fund securities
Current Assets
Marketable securities	320	292
Mutual fund securities | Recurring | Level 1
Current Assets
Marketable securities	320	292
Mutual fund securities | Recurring | Level 2
Current Assets
Marketable securities	0	0
Mutual fund securities | Recurring | Level 3
Current Assets
Marketable securities	0	0
Long-term available-for-sale securities: | Mutual fund securities
Long-term Assets
Marketable securities	1,045	732
Long-term available-for-sale securities: | Mutual fund securities | Level 1
Long-term Assets
Marketable securities	1,045
Long-term available-for-sale securities: | Mutual fund securities | Recurring | Level 1
Long-term Assets
Marketable securities		732
Long-term available-for-sale securities: | Mutual fund securities | Recurring | Level 2
Long-term Assets
Marketable securities	0	0
Long-term available-for-sale securities: | Mutual fund securities | Recurring | Level 3
Long-term Assets
Marketable securities	$ 0	$ 0

FAIR VALUE MEASUREMENTS - Rollf

FAIR VALUE MEASUREMENTS - Rollforward of Change in Level 3 Financial Instruments (Details) $ in Thousands	6 Months Ended
	Dec. 31, 2017USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at June 30, 2017	$ 12,600
Change in fair value	100
Balance at December 31, 2017	$ 12,700

STOCKHOLDERS' EQUITY - Addition

STOCKHOLDERS' EQUITY - Additional Information (Details) - USD ($) $ / shares in Units, shares in Millions	Sep. 19, 2017	Dec. 31, 2017	Dec. 31, 2016	Mar. 27, 2013
Class of Stock [Line Items]
Sales agreement, termination notice period		10 days
Follow on offering
Class of Stock [Line Items]
Issuance of common stock (in shares)	24.1
Offering price (in dollars per share)	$ 10.75
Net proceeds from the issuance of common stock	$ 243,000,000
Offering costs for issuance of common stock	$ 15,700,000	$ 15,732,000	$ 8,058,000
Net proceeds from the issuance of common stock		258,750,000	132,250,000
Underwriters option
Class of Stock [Line Items]
Issuance of common stock (in shares)	3.1
Market offering
Class of Stock [Line Items]
Offering costs for issuance of common stock		87,000	331,000
Net proceeds from the issuance of common stock		$ 2,917,000	$ 12,572,000
Common Stock
Class of Stock [Line Items]
Dollar amount of stock that may be sold under the agreement				$ 75,000,000
Commission under sales agreement, percent		2.00%
Average price per share (in dollars per share)		$ 9.02
Common Stock | Market offering
Class of Stock [Line Items]
Net proceeds from the issuance of common stock		$ 2,800,000

SHARE-BASED COMPENSATION - Fair

SHARE-BASED COMPENSATION - Fair Value Assumptions (Details) - Stock options - $ / shares	3 Months Ended	6 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum (percentage)		1.60%	1.10%
Risk-free interest rate, maximum (percentage)		2.04%	2.10%
Expected option term (in years)	5 years 6 months
Expected volatility, minimum (percentage)		66.10%	57.00%
Expected volatility, maximum (percentage)		67.00%	64.50%
Dividend yield (percentage)		0.00%	0.00%
Weighted average grant date fair value (in dollars per share)		$ 5.37	$ 4.23
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option term (in years)		3 years 11 months 1 day
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option term (in years)		4 years 1 month 6 days

SHARE-BASED COMPENSATION - Summ

SHARE-BASED COMPENSATION - Summary of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Dec. 31, 2017USD ($)$ / sharesshares
Number of Options [Roll Forward]
Number of options outstanding, beginning of period (in shares) | shares	14,844,028
Number of options, granted (in shares) | shares	3,094,150
Number of options, exercised (in shares) | shares	(2,629,526)
Number of options, forfeited (in shares) | shares	(388,551)
Number of options, expired or canceled (in shares) | shares	(10,000)
Number of options outstanding, end of period (in shares) | shares	14,910,101
Number of options, vested and expected to vest at end of period (in shares) | shares	14,887,879
Number of options, exercisable at end of period (in shares) | shares	5,906,109
Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price, beginning of period (in dollars per share) | $ / shares	$ 5.57
Weighted average exercise price, granted (in dollars per share) | $ / shares	10.56
Weighted average exercise price, exercised (in dollars per share) | $ / shares	5.47
Weighted average exercise price, forfeited (in dollars per share) | $ / shares	7.21
Weighted average exercise price, expired or canceled (in dollars per share) | $ / shares	11.28
Weighted average exercise price, end of period (in dollars per share) | $ / shares	6.58
Weighted average exercise price, vested and expected to vest at end of period (in dollars per share) | $ / shares	6.58
Weighted average exercise price, exercisable at end of period (in dollars per share) | $ / shares	$ 4.83
Weighted average remaining contractual term, outstanding at end of period (in years)	7 years 7 months 29 days
Weighted average remaining contractual term, vested and expected to vest at end of period (in years)	7 years 7 months 29 days
Weighted average remaining contractual term, exercisable at end of period (in years)	6 years 1 month
Aggregate intrinsic value, number of options outstanding, end of period | $	$ 92,791
Aggregate intrinsic value, vested and expected to vest at end of period | $	92,652
Aggregate intrinsic value, exercisable at end of period | $	$ 47,044

SHARE-BASED COMPENSATION - Su44

SHARE-BASED COMPENSATION - Summary of RSUs (Details) - RSUs	6 Months Ended
	Dec. 31, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of RSUs, beginning of period (in shares) | shares	982,709
Number of RSUs, granted (in shares) | shares	484,884
Number of RSUs, vested (in shares) | shares	(193,901)
Number of RSUs, forfeited (in shares) | shares	(28,952)
Number of RSUs, end of period (in shares) | shares	1,244,740
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted average grant date fair value, beginning of period (in dollars per share) | $ / shares	$ 6.27
Weighted average grant date fair value, granted (in dollars per share) | $ / shares	10.90
Weighted average grant date fair value, vested (in dollars per share) | $ / shares	7.09
Weighted average grant date fair value, forfeited (in dollars per share) | $ / shares	3.27
Weighted average grant date fair value, end of period (in dollars per share) | $ / shares	$ 8.02

SHARE-BASED COMPENSATION - Addi

SHARE-BASED COMPENSATION - Additional Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock price (in dollars per share)	$ 12.80		$ 12.80
Total intrinsic value of all options exercised			$ 14.8	$ 0.6
Total unrecognized compensation expense	$ 32.8		$ 32.8
Weighted-average period for recognition of unrecognized compensation expense (in years)			3 years 1 month 10 days
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock (as a percent)			85.00%
Original offering period (in months)			12 months
New offering period on termination of original offering period (in months)			6 months
Common shares available for issuance under ESPP (in shares)	900		900
Shares issued under ESPP (in shares)			154	282
Employee and non-employee awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 3.2	$ 2.1	$ 8.8	$ 4
Share-based payment award accelerated compensation cost			2.5
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense	$ 8.2		$ 8.2
Weighted-average period for recognition of unrecognized compensation expense (in years)			3 years 4 months 20 days
Fair market value on grant date, vested			$ 1.8	$ 0.5
RSUs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			2 years
RSUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years

RELATED PARTY TRANSACTION - Add

RELATED PARTY TRANSACTION - Additional Information (Details)	Sep. 30, 2017	Sep. 02, 2016
Redmile | Investor
Related Party Transaction [Line Items]
Common stock ownership percentage by related party (more than)	10.00%	10.00%

NET LOSS PER SHARE - Computatio

NET LOSS PER SHARE - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Net Income (Loss) Attributable to Parent, Diluted [Abstract]
Net loss - basic and diluted	$ (34,053)	$ (23,301)	$ (72,047)	$ (51,909)
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares outstanding – basic and diluted (in shares)	199,852	168,127	187,312	156,613
Per share data:
Basic and diluted (in dollars per share)	$ (0.17)	$ (0.14)	$ (0.38)	$ (0.33)

NET LOSS PER SHARE - Anti-dilut

NET LOSS PER SHARE - Anti-dilutive Common Stock Equivalents (Details) - shares shares in Thousands	6 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 01, 2017	Nov. 20, 2017	Jun. 10, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive common stock equivalents excluded from diluted loss per share calculation	24,311	34,378
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive common stock equivalents excluded from diluted loss per share calculation	14,910	14,500
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive common stock equivalents excluded from diluted loss per share calculation	1,245	1,116
2024 convertible senior notes | Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive common stock equivalents excluded from diluted loss per share calculation	8,156	0
2024 convertible senior notes | Convertible Senior Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate			2.625%	2.625%
2020 convertible senior notes | Convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total anti-dilutive common stock equivalents excluded from diluted loss per share calculation	0	18,762
2020 convertible senior notes | Convertible Senior Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Stated interest rate					3.00%

SUBSEQUENT EVENT (Details)

SUBSEQUENT EVENT (Details) - USD ($)	Jan. 03, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
License and milestone revenue		$ 11,315,000	$ 10,545,000	$ 14,861,000	$ 12,206,000
ASLAN | Subsequent event
Subsequent Event [Line Items]
License and milestone revenue	$ 12,000,000
ASLAN | Subsequent event | Developmental milestones
Subsequent Event [Line Items]
Potential milestone payments	30,000,000
ASLAN | Subsequent event | Regulatory milestones
Subsequent Event [Line Items]
Potential milestone payments	20,000,000
ASLAN | Subsequent event | Commercial milestones
Subsequent Event [Line Items]
Potential milestone payments	55,000,000
ASLAN | Subsequent event | Minimum | Developmental milestones
Subsequent Event [Line Items]
Potential milestone payments	11,000,000
ASLAN | Subsequent event | Maximum | Developmental milestones
Subsequent Event [Line Items]
Potential milestone payments	$ 12,000,000