Summary of Significant Accounting Policies | Summary of Significant Accounting Policies (A) Basis of Presentation: The Company’s fiscal year ends on March 31, and its first three fiscal quarters end on June 30, September 30 and December 31. The Company has determined that it has one operating and reporting segment as it allocates resources and assesses financial performance on a consolidated basis. The accompanying consolidated financial statements have been prepared in accordance with United States, or U.S., generally accepted accounting principles, or U.S. GAAP. Any reference in these notes to applicable accounting guidance is meant to refer to the authoritative U.S. GAAP included in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, issued by the Financial Accounting Standards Board, or FASB. The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. The Company has no unconsolidated subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. (B) Use of Estimates: The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions in certain circumstances that affect the amounts reported in the consolidated financial statements and accompanying notes. The Company regularly evaluates estimates and assumptions related to assets, liabilities, costs, and expenses, including the evaluation of the Company’s ability to continue as a going concern, compensation and other expenses allocated to the Company under its services agreements with Roivant Sciences, Inc., or RSI, and Roivant Sciences GmbH, or RSG, each a wholly owned subsidiary of the Company’s controlling shareholder, Roivant Sciences Ltd., or RSL, as well as share-based compensation expenses, research and development, or R&D, expenses and accruals, and income taxes. The Company bases its estimates and assumptions on historical experience and on various other factors that it believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses incurred during the reporting period, that are not readily apparent from other sources. Actual results could differ from those estimates. (C) Going Concern and Management’s Plans: The Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the consolidated financial statements are issued. During the year ended March 31, 2019 , the Company incurred net losses of $273.6 million and used $224.1 million of cash and cash equivalents in operations. The Company expects to continue to incur significant and increasing operating losses and negative cash flows as it continues to develop its product candidates and prepares for potential future regulatory approvals and commercialization of relugolix. The Company has not generated any revenue to date and does not expect to generate product revenue unless and until it successfully completes development and obtains regulatory approval for at least one of its product candidates. Based on its current operating plan, the Company expects that its existing cash and cash equivalents will be sufficient to fund its operating expenses and capital expenditure requirements through at least the first quarter of its fiscal year ending March 31, 2020. This estimate is based on the Company’s current assumptions, including assumptions relating to its ability to manage its spend, that might prove to be wrong, and it could use its available capital resources sooner than it currently expects. These funds will not be sufficient to enable the Company to complete all necessary development activities and commercially launch relugolix. The Company anticipates that it will continue to incur net losses for the foreseeable future. To continue as a going concern, the Company will need, among other things, additional capital resources. The Company continually assesses multiple options to obtain additional funding to support its operations, including through financing activities in public or private capital markets, financing arrangements with Roivant Sciences, structured transactions such as royalty financings, collaborations, license or development agreements, or other collaborations and cost containment measures. Management can provide no assurances that any sources of a sufficient amount of financing will be available to the Company on favorable terms, if at all. Although the Company believes that it will continue to raise capital to fund its operations as it has in the past, ASC 240-40, Going Concern , does not allow the Company to consider future financing activities that are not probable of being implemented in its assessment of the Company’s future cash burn for the purpose of its liquidity assessment. Due to these uncertainties, there is substantial doubt about the Company’s ability to continue as a going concern. The consolidated financial statements and footnotes have been prepared on the basis that the Company will continue as a going concern, and do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classification of liabilities that may result from the possible inability of the Company to continue as a going concern. (D) Risks and Uncertainties: The Company is subject to risks common to companies in the biotechnology industry, including, but not limited to, risks of failure or unsatisfactory results of nonclinical studies and clinical trials, the need to obtain additional financing to fund the future development of its product candidates, the need to obtain marketing approval for its product candidates, the need to successfully commercialize and gain market acceptance of its product candidates, dependence on key personnel, protection of proprietary technology, compliance with government regulations, development by competitors of technological innovations, ability to transition from pilot-scale manufacturing to large-scale production of products, and dependence on third-party service providers such as contract research organizations, or CROs, and contract manufacturing organizations, or CMOs. (E) Concentrations of Credit Risk: Financial instruments that potentially subject the Company to concentrations of credit risk include cash and cash equivalents consisting of money market funds and commercial paper. As of March 31, 2019 , cash and cash equivalent balances are diversified between three financial institutions. The Company is exposed to credit risk in the event of default by the financial institutions holding its cash and the issuers of its money market funds and commercial paper. The Company maintains its cash deposits and cash equivalents in highly-rated, federally-insured financial institutions in excess of federally insured limits. The Company has established guidelines relative to diversification and maturities of investments to maintain safety and liquidity. The Company has not experienced any credit losses related to these financial instruments and does not believe that it is exposed to any significant credit risk related to these instruments. (F) Cash, Cash Equivalents, and Restricted Cash: Cash and cash equivalents include cash deposits in banks and all highly liquid investments that are readily convertible to cash. The Company considers all highly liquid investments with a maturity of three months or less at the time of purchase to be cash equivalents. Interest income consists of interest earned on money market funds and the accretion of discounts to maturity for commercial paper. Restricted cash consists of non-interest bearing legally restricted deposits held as compensating balances against the Company’s corporate credit card program and an irrevocable standby letter of credit provided as security for the Company’s office lease. Cash as reported in the consolidated statements of cash flows includes the aggregate amounts of cash, cash equivalents, and restricted cash, and consists of the following (in thousands): March 31, 2019 2018 2017 Cash and cash equivalents $ 156,074 $ 108,624 $ 180,838 Restricted cash (1) 1,125 — — Total cash, cash equivalents and restricted cash $ 157,199 $ 108,624 $ 180,838 (1) Included in other assets on the consolidated balance sheets. (G) Property and Equipment, net: Property and equipment, net consisting of computers, equipment, furniture and fixtures, leasehold improvements, and software, is recorded at cost, less accumulated depreciation. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed to operations as incurred. Upon disposal, retirement or sale, the related cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is included in the results of operations. Depreciation is recorded for property and equipment using the straight-line method over the estimated useful lives of the assets, which range from three to seven years once the asset is installed and placed into service. Leasehold improvements are amortized using the straight-line method over their estimated useful life or the remaining lease term, whichever is shorter. The Company reviews the recoverability of its long-lived assets, including the related useful lives, whenever events or changes in circumstances indicate that the carrying amount of a long-lived asset might not be recoverable, based on undiscounted cash flows. If such assets are considered to be impaired, an impairment loss is recognized and is measured as the amount by which the carrying amount of the assets exceed their estimated fair value, which is measured based on the projected discounted future net cash flows arising from the assets. (H) Operating Leases: At the inception of a lease, the Company evaluates the lease agreement to determine whether the lease is an operating or capital lease. For operating leases, the Company recognizes rent expense on a straight-line basis over the lease term and records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. Where lease agreements contain rent escalation clauses, rent abatements and/or concessions, such as rent holidays and tenant improvement allowances, the Company applies them in the determination of straight-line rent expense over the lease term. Certain lease agreements also require the Company to make additional payments for taxes, insurance, and other operating expenses incurred during the lease period, which are expensed as incurred. (I) Debt Issuance Costs and Debt Discount: Debt issuance costs include the costs of debt financings undertaken by the Company, including legal fees, accounting fees, and other direct costs of the financing. Debt issuance costs related to a recognized debt liability are presented on the consolidated balance sheet as a direct deduction from the carrying amount of the debt liability, consistent with debt discounts, and are amortized to interest expense over the term of the related debt using the effective interest method. Further, debt discounts created as a result of the allocation of proceeds received from a debt issuance to warrants issued in conjunction with the debt issuance are amortized to interest expense under the effective interest method over the life of the recognized debt liability. (J) Contingencies: The Company may be, from time to time, a party to various disputes and claims arising from normal business activities. The Company continually assesses litigation to determine if an unfavorable outcome would lead to a probable loss or reasonably possible loss which could be estimated. In accordance with the guidance of the FASB on accounting for contingencies, the Company accrues for all contingencies at the earliest date at which the Company deems it probable that a liability has been incurred and the amount of such liability can be reasonably estimated. If the estimate of a probable loss is a range and no amount within the range is more likely than another, the Company accrues the minimum amount in the range. In the cases where the Company believes that a material reasonably possible loss exists, the Company discloses the facts and circumstances of the contingency, including an estimable range, if possible. (K) Research and Development Expenses: R&D costs are expensed as incurred. Clinical study costs are accrued over the service periods specified in the contracts and adjusted as necessary based on an ongoing review of the level of effort and costs actually incurred. Milestone payments made in connection with regulatory approvals are capitalized and amortized to cost of revenue over the remaining useful life of the asset. R&D expenses primarily consist of employee-related expenses, such as salaries, share-based compensation, benefits and travel expenses for employees engaged in R&D activities, payments made under third party license agreements, certain costs allocated to the Company for activities performed by RSI and RSG under services agreements with the Company, as well as allocated share-based compensation expense from RSL, and expenses from third parties who conduct R&D activities on behalf of the Company. The Company expenses in-process R&D projects acquired as asset acquisitions which have not reached technological feasibility and which have no alternative future use. (L) Share-Based Compensation: Share-based awards to employees and directors are valued at fair value on the date of grant and that fair value is recognized on a straight-line basis over the requisite service period, which is generally the vesting period of the respective award. The Company recognizes forfeitures in the period in which such forfeiture occurs and records share-based compensation expense as though all awards are expected to vest. The Company estimates the grant date fair value, and the resulting share-based compensation expense, using the Black-Scholes option-pricing model, which requires the use of highly subjective assumptions. These assumptions include: • Expected Term. The expected term represents the period that the Company’s share-based awards are expected to be outstanding and is determined using the simplified method in accordance with the Securities and Exchange Commission, or SEC, Staff Accounting Bulletin, or SAB, No. 107 and No. 110 (based on the mid-point between the vesting date and the end of the contractual term). • Expected Volatility. Because the Company did not have an extended trading history for its common shares, the expected volatility was estimated using weighted average measures of implied volatility and the historical volatility of a peer group of companies for a period equal to the expected life of the stock options. The Company’s peer group of publicly traded biopharmaceutical companies was chosen based on their similar size, stage in the life cycle or area of specialty. • Risk-Free Interest Rate. The risk-free interest rate is based on the interest rates paid on securities issued by the U.S. Treasury with a term approximating the expected life of the stock options. • Expected Dividend. The Company has never paid, and does not anticipate paying, cash dividends on its common shares. Therefore, the expected dividend yield was assumed to be zero . Share-based compensation expense associated with time-vesting restricted share awards and restricted stock units is based on the fair value of the Company’s common shares on the grant date, which equals the closing market price of the Company’s common shares on the grant date. The Company recognizes the share-based compensation expense related to these awards on a straight-line basis over the requisite service period, which is generally the vesting period of the respective awards. Share-based compensation expense associated with restricted share awards subject to market conditions is estimated on the grant date using a Monte Carlo valuation model. The resulting fair value is recognized as share-based compensation expense ratably over the derived service period regardless of whether the market conditions are satisfied. RSL restricted stock units granted to the Company’s Principal Executive Officer vest upon the achievement of both a performance and market condition, if both are achieved by the contractual expiration date and the Principal Executive Officer has remained in continuous service with RSL or any of its subsidiaries. The Company will recognize share-based compensation expense related to this award upon the achievement of the performance and market conditions throughout the requisite service period. Share-based payment awards granted by RSL to RSL, RSI, RSG and the Company’s employees are valued by RSL at fair value on the date of grant and that fair value is recognized as share-based compensation expense over the requisite service period. Significant judgment and estimates were used by RSL to estimate the fair value of these awards, as they are not publicly traded. RSL share-based payment awards are subject to specified vesting schedules and requirements (a mix of time-based and performance-based events). The fair value is based on various corporate event-based considerations, including targets for RSL’s post-IPO market capitalization and future financing events. The fair value of each RSL option is estimated on the date of grant using the Black-Scholes closed-form option-pricing model. Share-based compensation expense has been and will continue to be allocated to the Company over the requisite service period over which these RSL share-based payment awards are expected to vest and based on the relative percentage of time utilized by RSL, RSI and RSG employees on the Company’s matters. No tax benefits for share-based compensation has been recognized in the consolidated statements of shareholders’ equity (deficit) or consolidated statements of cash flows. The Company has not recognized, and does not expect to recognize in the near future, any tax benefits related to share-based compensation as a result of its full valuation allowance on net deferred tax assets and net operating loss carryforwards. (M) Takeda Warrant Liability: The Company recorded the Takeda warrant liability at its estimated fair value in the consolidated balance sheets. The Company remeasured the estimated fair value of the Takeda warrant liability each reporting period in which it was outstanding and recorded the change in the fair value in the consolidated statements of operations and comprehensive loss. The Takeda warrant liability expired on April 30, 2017. (N) Income Taxes: Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and the respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A valuation allowance is recorded when, after consideration of all positive and negative evidence, it is not more likely than not that the Company’s deferred tax assets will be realizable. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. Interest and/or penalties related to income tax matters are recognized as a component of income tax expense as incurred. (O) Net Loss per Common Share: Basic net loss per common share is computed by dividing net loss applicable to common shareholders by the weighted-average number of common shares outstanding during the period, reduced, where applicable, for outstanding yet unvested shares of restricted common stock. The computation of diluted net loss per common share is based on the weighted-average number of common shares outstanding during the period plus, when their effect is dilutive, incremental shares consisting of shares subject to stock options, restricted stock units, restricted share awards, and warrants. In periods in which the Company reports a net loss, all common share equivalents are deemed anti-dilutive such that basic net loss per common share and diluted net loss per common share are equal. Potentially dilutive common shares have been excluded from the diluted net loss per common share computations in all periods presented because such securities have an anti-dilutive effect on net loss per common share due to the Company’s net loss. There are no reconciling items used to calculate the weighted-average number of total shares outstanding for basic and diluted net loss per common share. As of March 31, 2019 , 2018 and 2017 , potentially dilutive securities were as follows: March 31, 2019 2018 2017 Stock options 5,396,465 3,549,405 1,525,857 Restricted share awards (unvested) 916,679 1,198,735 1,128,222 Restricted stock units (unvested) 39,387 15,000 — Warrants 73,710 73,710 — Total 6,426,241 4,836,850 2,654,079 (P) Fair Value Measurements: The Company utilizes fair value measurement guidance prescribed by accounting standards to value its financial instruments. The guidance establishes a fair value hierarchy for financial instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. Fair value is defined as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the reporting date. As a basis for considering market participant assumptions in fair value measurements, the guidance establishes a three-tier fair value hierarchy that distinguishes among the following: • Level 1-Valuations are based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access. • Level 2-Valuations are based on quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active and models for which all significant inputs are observable, either directly or indirectly. • Level 3-Valuations are based on inputs that are unobservable (supported by little or no market activity) and significant to the overall fair value measurement. To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The Company’s financial instruments include cash, cash equivalents consisting of commercial paper and money market funds, accounts payable and debt. Cash, cash equivalents, and accounts payable are stated at their respective historical carrying amounts, which approximate fair value due to their short-term nature. The carrying value of the Company’s debt approximates fair value based on current interest rates for similar types of borrowings and is included in Level 2 of the fair value hierarchy. (Q) Foreign Currency: The results of the Company’s non-U.S. dollar based functional currency operations are translated to U.S. dollars at the average exchange rates during the period. The Company’s assets and liabilities are translated using the current exchange rate as of the balance sheet date and shareholders’ equity (deficit) is translated using historical rates. Adjustments resulting from the translation of the financial statements of the Company’s foreign functional currency subsidiaries into U.S. dollars are excluded from the determination of net loss and are accumulated in a separate component of shareholders’ equity (deficit). Foreign currency exchange transaction gains and losses are included in other expense (income), net in the Company’s consolidated statements of operations. (R) Recently Adopted Accounting Standards: In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (a consensus of the FASB Emerging Issues Task Force , or ASU 2016-18 . The amendments in this update require that amounts generally described as restricted cash and restricted cash equivalents be included within cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 is effective for annual reporting periods beginning after December 15, 2017 and is required to be adopted using a retrospective approach, if applicable, with early adoption permitted. The Company adopted ASU 2016-18 on April 1, 2018. The adoption of ASU 2016-18 did not have a material impact on the Company’s consolidated financial statements and related disclosures. In March 2018, the FASB issued ASU 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 (SAB No. 118), or ASU 2018-05. ASU 2018-05 adds various SEC paragraphs pursuant to the issuance of the December 2017 SEC Staff Accounting Bulletin (SAB) No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act , which was effective immediately. The SEC issued SAB No. 118 to address concerns about reporting entities’ ability to comply timely with the accounting requirements to recognize the effects of the Tax Cuts and Jobs Act in the period of enactment. SAB No. 118 allows disclosure that timely determination of some or all of the income tax effects from the Tax Cuts and Jobs Act are incomplete by the due date of the financial statements and if possible to provide a reasonable estimate. As permitted by SAB No. 118, the Company recorded provisional amounts in the year ended March 31, 2018 and finalized its accounting for these provisional estimates based on guidance, interpretations and all available data in the year ended March 31, 2019. No material adjustments were made to the provisional amounts. In October 2016, the FASB issued ASU 2016-16, Intra-Entity Transfers of Assets Other Than Inventory , or ASU 2016-16. ASU 2016-16 requires the income tax consequences of intra-entity transfers of assets, other than inventory, to be recognized when the transfer occurs. The new standard was effective for the Company on April 1, 2018 and was adopted using a modified retrospective approach. The adoption of this standard resulted in the recognition of a deferred tax asset of $38.7 million with a corresponding valuation allowance of $38.7 million . (S) Recently Issued Accounting Standards Not Yet Adopted: (1) Leases: In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which is a comprehensive new lease standard that amends various aspects of existing accounting guidance for leases. Topic 842 was subsequently amended by ASU 2018-01, Land Easement Practical Expedient for Transition to Topic 842 ; ASU 2018-10, Codification Improvements to Topic 842, Leases ; and ASU 2018-11, Targeted Improvements . The core principle of Topic 842 will require lessees to recognize on the consolidated balance sheets a liability to make lease payments and a right-of-use, or ROU, asset representing its right to use the underlying asset for the lease term for both finance and operating leases with lease terms greater than twelve months. The lease liability will be measured at the present value of the unpaid lease payments and the ROU asset will be derived from the calculation of the lease liability. Lease payments will include fixed and in-substance fixed payments, variable payments based on an index or rate, exercise price of purchase options that are reasonably certain to be exercised, termination penalties, and probable amounts the lessee will owe under a residual value guarantee. Topic 842 also requires lessees to disclose key information about leasing arrangements. Topic 842 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, with early adoption permitted. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application (“Transition Date”). An entity may choose to use either (i) its effective date or (ii) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. The Company plans to adopt the new standard on April 1, 2019 and use the effective date as its date of initial application. The new standard provides a number of optional practical expedients in transition. The Company expects to elect the “package of practical expedients,” which permits it to not reassess under the new standard its prior conclusions about lease identification, lease classification, and initial direct costs. As a result, the Company will in effect, continue to account for existing leases - i.e. leases for which the commencement date is before April 1, 2019 - in accordance with Topic 840 throughout the entire lease term, including periods after the effective date, with the exception that the Company will apply the new balance sheet recognition guidance for operating leases and apply Topic 842 for remeasurements and modifications after the Transition Date. While the Company continues to assess all the effects of adoption, the Company believes the most significant effects relate to the recognition of a ROU asset and corresponding liability on its consolidated balance sheet, primarily related to its existing facility operating lease, and providing new disclosures with regards to the Company’s leasing activities. The Company currently expects that the adoption of the new standard will result in the recording of a ROU asset of approximately $9.0 million to $10.0 million and a lease liability of approximately $10.0 million to $11.0 million . (2) Others: In February 2018, the FASB issued ASU 2018-02, Income Statement- Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income , or ASU 2018-02. ASU 2018-02 allows companies to reclassify stranded tax effects resulting from the newly enacted federal corporate income tax rate under the Tax Cuts and Jobs Act, from accumulated other comprehensive (loss) income to retained earnings. ASU 2018-02 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018 and early adoption is permitted. The Company plans to adopt this new standard on April 1, 2019. The Company does not expect that the adoption of ASU 2018-02 will have a material impact on its consolidated financial statements and related disclosures. In June 2018, the FASB issued ASU 2018-07, Compensation- Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting , or ASU 2018-07. ASU 2018-07 simplifies the accounting for share-based payments to nonemployees by aligning it with the accounting for share-based payments to employees, with certain exceptions. ASU 2018-07 is effective for interim and annual reporting periods beginning after December 15, 2018 and early adoption is permitted. The Company plans to adopt the new standard on April 1, 2019. The Company does not expect that the adoption of ASU 2018-07 will have a material impact on its consolidated financial statements and related disclosures. In August 2018, th |