OVERVIEW, BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	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 our 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. Our management performed an evaluation of our 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 our audited financial statements and the notes thereto for the fiscal year ended June 30, 2018 included in our Annual Report on Form 10-K from which we derived our balance sheet data as of June 30, 2018.
Segment Reporting	We operate in one reportable segment and, accordingly, no segment disclosures have been presented herein.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires our 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. We base our estimates on our historical experience and on various other assumptions that we believe are reasonable under the circumstances. Our actual results could differ significantly from these estimates under different assumptions or conditions. On an ongoing basis, we evaluate our estimates, including our most significant estimates related to revenue recognition, gross-to-net product sales adjustments, and estimating accrued outsourcing costs for clinical trials and preclinical testing.
Concentration of Business Risks	The loss of one or more of our significant partners or collaborators could have a material adverse effect on our business, operating results or financial condition.
Product Sales, Net	Product Sales, Net We received approval from the FDA on June 27, 2018 to market BRAFTOVI + MEKTOVI in the U.S. for the treatment of patients with unresectable or metastatic melanoma with a BRAFV^600E or BRAF^V600K mutation. We began selling BRAFTOVI + MEKTOVI in the U.S. in July 2018. We distribute our products principally through a limited number of specialty distributor and specialty pharmacy providers (collectively, our "Customers"). Our Customers subsequently sell our products to patients and health care providers. Separately, we enter into arrangements with third parties that provide for government-mandated and privately-negotiated rebates, chargebacks and discounts. Revenue from product sales is recognized when our performance obligations are satisfied, which is when Customers obtain control of our product and occurs upon delivery. Reserves for Variable Consideration Revenues from product sales are recorded at the net sales price (transaction price), which includes estimates of variable consideration, including rebates, chargebacks, discounts, patient assistance programs, estimated product returns and other allowances that are offered within contracts between us and our Customers. These estimates are based on the amounts earned or to be claimed for related sales and are classified as reductions of accounts receivable if the amount is payable to our Customers or a current liability if the amount is payable to a party other than a Customer. Where appropriate, these estimates take into consideration a range of possible outcomes which are probability-weighted for relevant factors such as industry data and forecasted customer buying and payment patterns, our historical experience, current contractual and statutory requirements, specific known market events and trends. Overall, these reductions to gross sales reflect our best estimates of the amount of consideration to which we are entitled based on the terms of the contract. Variable consideration is included in the transaction price only to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. Actual amounts of consideration ultimately received may differ from our estimates. If actual results in the future vary from our estimates, we adjust these estimates, which would affect product revenue and earnings in the period such variances become known. Rebates: Rebates include mandated discounts under the Medicaid Drug Rebate Program ("Medicaid") and the Medicare Coverage Gap Program ("Medicare"). Rebates are amounts owed after the final dispensing of products to a benefit plan participant and are based upon contractual agreements or legal requirements with the public-sector benefit providers. These estimates for rebates are recorded in the same period the related gross revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included in accrued expenses on the consolidated balance sheet. We estimate our Medicaid and Medicare rebates based upon a range of possible outcomes that are probability-weighted for the estimated payor mix. The accrual for rebates is based on statutory discount rates and known sales to specialty pharmacy patients or expected utilization for specialty distributor sales to healthcare providers. As we gain more historical experience, estimates will be based on the expected utilization from historical data we have accumulated since the BRAFTOVI + MEKTOVI product launch. Rebates are generally invoiced and paid quarterly in arrears. Chargebacks: Chargebacks are discounts that occur when contracted purchasers purchase directly from our specialty distributors at a discounted price. The specialty distributor, in turn, charges back the difference between the price initially paid to us by the specialty distributor and the discounted price paid to the specialty distributor by the contracted purchaser. Amounts for estimated chargebacks are established in the same period that the related gross revenue is recognized, resulting in a reduction of product revenue and accounts receivable. The accrual for specialty distributor chargebacks is estimated based on known chargeback rates, known sales to specialty distributors, and estimated utilization by types of contracted purchasers. Discounts and Fees: Our payment terms are generally 45 days. Specialty distributors and specialty pharmacies are offered various forms of consideration, including service fees and prompt pay discounts for payment within a specified period. We expect these Customers will earn prompt pay discounts and therefore, we deduct the full amount of these discounts and service fees from product sales when revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Other Reserves: Patients who have commercial insurance and meet certain eligibility requirements may receive co-pay assistance. We estimate the amount of co-pay assistance provided to eligible patients based on the terms of the program when product is dispensed by specialty pharmacies to patients. These estimates are based on redemption information provided by third-party claims processing organizations and are recorded in accounts payable, accrued expenses and other liabilities on the unaudited condensed consolidated balance sheet. We are offering a quick start program in the form of vouchers to eligible patients. We record amounts for estimated voucher redemptions in the same period that the related gross revenue is recognized, resulting in a reduction of product revenue, and these amounts are recorded in accounts payable, accrued expenses and other liabilities on the unaudited condensed consolidated balance sheet. Our accrual for voucher redemptions is estimated based on observed voucher redemption rates.
Cost of goods sold	Cost of Goods Sold Cost of goods sold consists of the cost of goods sold to Customers, international partners under product supply agreements, and royalty expense based on net sales of BRAFTOVI. We capitalize inventory costs associated with the production of our products after regulatory approval or when, based on management’s judgment, future commercialization is considered probable and the future economic benefit is expected to be realized. Otherwise, such costs are expensed as research and development.
Recent Accounting Pronouncements	Recently Adopted Accounting Standards In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09, "Revenue from Contracts with Customers (Topic 606)" ("ASU 2014-09") and has subsequently issued a number of amendments to ASU 2014-09 (collectively, "ASC 606"). The new standard, as amended, 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 standard was effective for us on July 1, 2018, prior to our first commercial product sale, and we elected to adopt it using a modified retrospective transition method applied only to contracts that were not completed as of July 1, 2018. Our adoption of ASU 2014-09 did not require any cumulative effect adjustment to opening accumulated deficit as of July 1, 2018 and did not have a material impact on our unaudited condensed consolidated financial statements. We have examined our revenue recognition policies and contracts related to our collaboration, co-development and product revenue streams to determine the impact of the new standard using the five-step process prescribed by ASC 606 and recognize revenue for our categories of revenue as follows: Product sales: Revenue from product sales is recognized when our performance obligations are satisfied, which is when customers obtain control of our product and occurs at a point in time, typically upon delivery. Licenses of intellectual property: If the license granted to our intellectual property is determined to be a discrete performance obligation from the other performance obligations identified in the arrangement, we recognize revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the licensee and the recipient of the license is able to use and benefit from the license. For licenses that are determined to not be distinct from other performance obligations, such as development activities, we recognize revenue over time, using an input method as the related performance obligations are satisfied. Upfront payments are recorded as deferred revenue upon receipt and are recognized as revenue during subsequent periods as our performance obligations are met. Milestone payments: Developmental and regulatory milestone payments generally relate to performance obligations that have been completed in the past and are recognized as revenue in the period in which the milestone is achieved and material risk of reversal of revenue has passed. Due to the uncertainty of drug development and the high historical failure rates generally associated with drug development, we may not receive any additional milestone payments under our agreements. We reevaluate the likelihood of achieving future milestones at the end of each reporting period. If the risk of significant reversal is resolved, future milestone revenue from an arrangement will be recognized as revenue in the period the risk is relieved. Adoption of ASC 606 has the effect of accelerating recognition of revenue for certain commercial milestone payments as compared to the legacy accounting guidance. Product royalty and commercial milestone revenue: We have entered into arrangements that include sales-based royalties or commercial milestone payments for which the license is deemed to be the predominant item to which the royalties or milestones relate. We recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty was allocated has been satisfied (or partially satisfied). In August 2016, the FASB issued ASU No. 2016-15, "Statement of Cash Flows (Topic 230)" ("ASU 2016-15"). This amendment provides 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. We adopted the new standard on July 1, 2018 and did not have a material impact on our consolidated financial statements. In May 2017, the FASB issued ASU 2017-09, "Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting" ("ASU 2017-09"), which clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. ASU 2017-19 is effective prospectively for the annual period ending June 30, 2019 and interim periods within that annual period. Early adoption is permitted. We adopted the new standard on July 1, 2018 and did not have a material impact on our consolidated financial statements. Recently Issued Accounting Standards In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)" ("ASU 2016-02") 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. In July 2018, the FASB issued ASU 2018-11, “Leases (Topic 842): Targeted Improvements” and ASU 2018-10, “Codification Improvements to Topic 842, Leases.” ASU 2016-02 and the subsequent modifications are identified as “ASC 842.” 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 fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018, with early adoption permitted upon issuance. We are currently evaluating the impact that ASU 2016-02 will have on our unaudited condensed consolidated financial statements and related disclosures and plan to adopt the new standard on July 1, 2019. We expect to record new right of use assets and lease liabilities, but do not expect the new standard to have a material impact on our consolidated financial statements.