Biohaven Pharmaceutical Holding 10-Q 9 Aug 19 2019 Q2 Quarterly report Financial data

COVER PAGE

COVER PAGE - shares	6 Months Ended
	Jun. 30, 2019	Aug. 07, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	001-38080
Entity Registrant Name	Biohaven Pharmaceutical Holding Co Ltd.
Entity Central Index Key	0001689813
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Incorporation, State or Country Code	D8
Entity Address, Address Line One	c/o Biohaven Pharmaceuticals, Inc.
Entity Address, Address Line Two	215 Church Street
Entity Address, City or Town	New Haven
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06510
City Area Code	203
Local Phone Number	404-0410
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Shares, no par value
Trading Symbol	BHVN
Security Exchange Name	NYSE
Entity Common Stock, Shares Outstanding		52,154,296

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash	$ 465,739	$ 264,249
Prepaid expenses and other current assets	8,613	8,090
Total current assets	474,352	272,339
Property and equipment, net	7,433	6,248
Equity method investment	9,099	11,414
Other assets	24	11
Total assets	490,908	290,012
Current liabilities:
Accounts payable	13,502	10,752
Accrued expenses	31,167	8,782
Total current liabilities	44,669	19,534
Liability related to sale of future royalties	129,487	117,515
Mandatorily redeemable preferred shares, net	94,890	0
Derivative liability	35,078	0
Other long-term liabilities	43	2,043
Total liabilities	304,167	139,092
Commitments and contingencies
Shareholders’ equity:
Common shares, no par value; 200,000,000 shares authorized as of June 30, 2019 and December 31, 2018; 51,501,614 and 44,197,549 shares issued and outstanding as of June 30, 2019 and December 31, 2018, respectively	844,966	554,384
Additional paid-in capital	58,717	40,104
Accumulated deficit	(716,942)	(443,568)
Total shareholders’ equity	186,741	150,920
Total liabilities and shareholders’ equity	$ 490,908	$ 290,012

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Common shares, par value (in dollars per share)	$ 0	$ 0
Common shares, authorized (shares)	200,000,000	200,000,000
Common shares, issued (shares)	51,501,614	44,197,549
Common shares, outstanding (shares)	51,501,614	44,197,549

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating expenses:
Research and development	$ 175,977	$ 29,052	$ 216,980	$ 104,631
General and administrative	23,235	9,064	36,697	16,921
Total operating expenses	199,212	38,116	253,677	121,552
Loss from operations	(199,212)	(38,116)	(253,677)	(121,552)
Other income (expense):
Non-cash interest expense on mandatorily redeemable preferred shares	(3,955)	0	(3,955)	0
Non-cash interest expense on liability related to sale of future royalties	(5,151)	(501)	(11,964)	(501)
Change in fair value of warrant liability	0	0	0	(1,182)
Change in fair value of derivative liability	(1,263)	0	(1,263)	0
Loss from equity method investment	(1,415)	(641)	(2,315)	(1,369)
Other	(16)	14	(33)	(15)
Total other expense, net	(11,800)	(1,128)	(19,530)	(3,067)
Loss before provision for income taxes	(211,012)	(39,244)	(273,207)	(124,619)
Provision for income taxes	58	25	167	112
Net loss and comprehensive loss	$ (211,070)	$ (39,269)	$ (273,374)	$ (124,731)
Net loss per share - basic and diluted (in dollars per share)	$ (4.67)	$ (1.01)	$ (6.11)	$ (3.29)
Weighted average common shares outstanding - basic and diluted (shares)	45,226,434	38,942,545	44,736,971	37,873,755

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net loss	$ (211,070)	$ (39,269)	$ (273,374)	$ (124,731)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash share-based compensation expense			24,884	8,696
Non-cash interest expense on mandatorily redeemable preferred shares	3,955	0	3,955	0
Non-cash interest expense on liability related to sale of future royalties	5,151	501	11,964	501
Change in fair value of derivative liability	1,263	0	1,263	0
Change in fair value of warrant liability	0	0	0	1,182
Loss from equity method investment	1,415	641	2,315	1,369
Other non-cash items			271	53
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			(523)	(4,953)
Other assets			(13)	(11)
Accounts payable			2,117	(694)
Accrued expenses			22,385	3,643
Other long-term liabilities			(2,000)	(44)
Net cash used in operating activities			(206,756)	(114,989)
Cash flows from investing activities:
Purchases of property and equipment			(1,448)	(1,501)
Purchase of equity method investment			0	(1,375)
Net cash used in investing activities			(1,448)	(2,876)
Cash flows from financing activities:
Proceeds from issuance of common shares			282,000	55,000
Proceeds from sale of future royalties			0	106,047
Proceeds from issuance of common stock related to sale of future royalties			0	43,953
Proceeds from issuance of mandatorily redeemable preferred shares			125,000	0
Proceeds from exercise of warrants			1,998	0
Payments of issuance costs			(517)	(2,987)
Proceeds from exercise of stock options			1,213	1,836
Net cash provided by financing activities			409,694	203,849
Net increase in cash			201,490	85,984
Cash at beginning of period			264,249	131,468
Cash at end of period	$ 465,739	$ 217,452	465,739	217,452
Supplemental disclosure of cash flow information:
Cash paid for interest			0	0
Cash paid for income taxes			428	23
Supplemental disclosure of non-cash investing and financing activities:
Offering costs included in accounts payable and accrued expenses			$ 633	$ 377

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	Nature of the Business and Basis of Presentation Biohaven Pharmaceutical Holding Company Ltd. (“we,” “us” or the “Company”) was incorporated in Tortola, British Virgin Islands in September 2013. We are a clinical-stage biopharmaceutical company with a portfolio of innovative, late-stage product candidates targeting neurological diseases, including rare disorders. Our product candidates are based on multiple mechanisms —calcitonin gene-related peptide (“CGRP”) receptor antagonists, glutamate modulators and myeloperoxidase inhibition—which we believe have the potential to significantly alter existing treatment approaches across a diverse set of neurological indications with high unmet need in both large and orphan indications. The most advanced product candidate from the Company’s CGRP receptor antagonist platform is rimegepant, which the Company is developing for the acute and preventive treatment of migraine. During the second quarter of 2019, the Company submitted new drug applications ("NDA") to the United States Food and Drug Administration ("FDA") for the Zydis ® Orally Dissolving Tablet ("ODT") and tablet formulations of rimegepant. The NDA submission of rimegepant Zydis ODT was submitted using a FDA priority review voucher, purchased in April 2019, providing for an expedited 6-month review. The Company is subject to risks and uncertainties common to clinical-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Product candidates currently under development will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval, prior to commercialization. These efforts may require additional capital, additional personnel and infrastructure, and further regulatory and other capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize revenue from product sales. Through June 30, 2019 , the Company has funded its operations primarily with proceeds from sales of equity and other financing transactions. Subsequent to its May 2017 initial public offering, the Company has primarily raised funds through sales of equity in private placements and public offerings, as well as through the sale of a revenue participation right related to potential future royalties. The Company has incurred recurring losses since its inception, had an accumulated deficit as of June 30, 2019 , and expects to continue to generate operating losses for the foreseeable future. To execute its business plans, the Company will continue to require additional funding to support its continuing operations and pursue its growth strategy. The accompanying condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company and its subsidiaries after elimination of all significant intercompany accounts and transactions. Investments in companies in which the Company owns less than a 50% equity interest and where it exercises significant influence over the operating and financial policies of the investee are accounted for using the equity method of accounting.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of income and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual for research and development expenses and the valuation of common shares, stock options, warrants, derivative instruments, contingent equity instruments, and non-cash interest expense on liability related to sale of future royalties. In addition, management’s assessment of the Company’s ability to continue as a going concern involves the estimation of the amount and timing of future cash inflows and outflows. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates. Fair Value Measurements Certain assets of the Company are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1— Quoted prices in active markets for identical assets or liabilities. • Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. • Level 3—Unobservable inputs that are supported by little or no market activity that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The Company’s derivative liability is carried at fair value, determined according to the fair value hierarchy described above (see Note 3 ). Unaudited Interim Condensed Consolidated Financial Information The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information. The accompanying unaudited condensed consolidated financial statements do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for complete consolidated financial statements. The accompanying year-end condensed consolidated balance sheet was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of June 30, 2019 and the results of its operations for the three and six months ended June 30, 2019 and 2018 and its cash flows for the six months ended June 30, 2019 and 2018 . The results for the three and six months ended June 30, 2019 are not necessarily indicative of results to be expected for the year ending December 31, 2019 , any other interim periods or any future year or period. The financial information included herein should be read in conjunction with the financial statements and notes in the Company's Annual Report on Form 10-K for the year ended December 31, 2018 . Recently Adopted Accounting Pronouncements Effective January 1, 2019, the Company adopted ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., 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 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. In July of 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases (“ASU 2018-10”) , and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements (“ASU 2018-11”), both of which clarified and enhanced the certain amendments made in ASU 2016-02 and were adopted by the Company in conjunction with ASU 2016-02. The adoption requires a modified retrospective transition approach, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (1) its effective date or (2) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. The Company has elected to adopt the standard using the effective date, January 1, 2019, as its date of initial application. Consequently, financial information will not be updated, and the disclosures required under the new standard will not be provided for dates and periods before January 1, 2019. Given that the Company had no material outstanding leases as of the date of the adoption, the adoption of ASU 2016-02 did not have a material impact on the Company's financial position or results of operations.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	Fair Value of Financial Assets and Liabilities The Company held no financial assets measured at fair value on a recurring basis as of June 30, 2019 , and no financial assets or liabilities measured at fair value on a recurring basis as of December 31, 2018 . The following tables present information about the Company's financial liability measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair value: Fair Value Measurement as of June 30, 2019 Using: Level 1 Level 2 Level 3 Total Liabilities: Derivative liability $ — $ — $ 35,078 $ 35,078 $ — $ — $ 35,078 $ 35,078 The following table provides a roll forward of the aggregate fair value of the Company’s derivative liability for which fair value is determined by Level 3 inputs: Derivative Transaction date balance $ 33,815 Change in fair value 1,263 Balance at June 30, 2019 $ 35,078 Valuation of Derivative Liability The fair value of the derivative liability recognized in connection with the Series A preferred shares agreement with RPI Finance Trust ("RPI"), as described in Note 8 , was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The fair value of the derivative liability relates to certain scenarios outlined in the agreement that would result in accelerated payments as compared to the agreement's host instrument. The with-and-without valuation method was used to determine the fair value of the embedded derivatives within the agreement. As inputs into the valuation, the Company considered the type and probability of occurrence of certain events, the amount of the payments, the expected timing of certain events, and a risk-adjusted discount rate. In accordance with ASC 815, Derivatives and Hedging, the fair value of the derivative was recorded on the balance sheet as a derivative liability with changes in fair value recorded in other income (expense) in the condensed consolidated statements of operations and comprehensive loss. If factors change and different assumptions are used, the fair value of the derivative liability and related gains or losses could be materially different in the future. Valuation of Liability Related to Sale of Future Royalties In June 2018, and as described in Note 7 , the Company entered into a funding agreement with RPI, accounted for as a liability financing. As of June 30, 2019 , the fair value of the liability related to sale of future royalties, used in determining the effective interest rate of the liability, is based on the Company's current estimates of future royalties expected to be paid to RPI over the life of the arrangement, which is considered Level 3.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	6 Months Ended
	Jun. 30, 2019
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following: As of June 30, 2019 As of December 31, 2018 Prepaid clinical trial costs $ 7,271 $ 7,210 Prepaid insurance 1,208 393 Other 134 487 $ 8,613 $ 8,090

Equity Method Investment

Equity Method Investment	6 Months Ended
	Jun. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investment	Equity Method Investment On August 29, 2016, the Company executed a stock purchase agreement with Kleo Pharmaceuticals, Inc. (“Kleo”), a privately held Delaware corporation, to purchase 3,000,000 shares of Kleo’s common stock at an initial closing, with a commitment to purchase an aggregate of 5,500,000 additional shares of common stock, in each case at a share price of $1.00 per share. Kleo is a development-stage biopharmaceutical company focused on advancing the field of immunotherapy by developing small molecules that emulate biologics. The Company purchased 3,000,000 shares upon the initial closing on August 31, 2016, and the remaining 5,500,000 shares were purchased in four equal tranches of 1,375,000 shares beginning six months from the initial closing and then every three months thereafter. In connection with the initial investment, the Company received the right to designate two of the members of Kleo’s board of directors. The Company completed all four of the remaining tranche purchases in March, June and October 2017 and January 2018, with each tranche purchase consisting of 1,375,000 shares for cash consideration of $1,375 . In March 2017, the Company purchased 500,000 shares of Kleo common stock directly from a co-founder of Kleo for consideration of $250 in cash and 32,500 common shares of the Company. In addition to these purchases, in October 2017, the Company purchased an additional aggregate of 2,049,543 shares for cash consideration of $2,253 which allowed the Company to maintain its relative ownership interest in Kleo. In November 2018, the Company participated in Kleo's Series B financing. The Company purchased 1,420,818 shares for cash consideration of $5,000 . As of the close of the Series B financing, the Company's ownership interest in the outstanding stock of Kleo was 41.9% . The Company has a variable interest in Kleo through its equity investment. Kleo is a variable interest entity due to the equity investment at risk being insufficient to finance its activities. An assessment of whether or not the Company has the power to direct activities that most significantly impact Kleo’s economic performance and to identify the party that obtains the majority of the benefits of the investment was performed as of June 30, 2019 and December 31, 2018 , and will be performed as of each subsequent reporting date. After each of these assessments, the Company concluded that the activities that most significantly impact Kleo’s economic performance are the ability to direct the research activities, the ability to select vendors to perform the research, the ability to maintain research staff and the ability to raise additional funds, each of which are directed by Kleo. Based on the outcome of these assessments, the Company concluded that the investment should be accounted for under the equity method. The Company has recorded its investments in Kleo to date based on the costs of those investments, as adjusted for the Company’s proportional share of Kleo’s net income or loss in each period. The Company records future adjustments to the carrying value of its investment at each reporting date equal to its proportionate share of Kleo’s net loss for the corresponding period. The Company recorded other expense and a corresponding reduction in the carrying value of its investment in Kleo as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Proportionate share of Kleo's net loss $ 1,415 $ 641 $ 2,315 $ 1,369 The carrying value of the Company’s investment in Kleo was $9,099 and $11,414 as of June 30, 2019 and December 31, 2018 , respectively, and is reported as equity method investment on the condensed consolidated balance sheet. The carrying value of the investment represents the Company’s maximum loss exposure as of the balance sheet date. The following table provides a roll-forward of the carrying value of the Company’s equity method investment: Carrying Value Balance at December 31, 2018 $ 11,414 Loss recognized in connection with equity method investment (2,315 ) Balance at June 30, 2019 $ 9,099 Balance at December 31, 2017 $ 7,847 Purchases of Kleo common stock 1,375 Loss recognized in connection with equity method investment (1,369 ) Balance at June 30, 2018 $ 7,853

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2019
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses consisted of the following: As of June 30, 2019 As of December 31, 2018 Accrued development milestones payable (Note 13) $ 13,500 $ — Accrued employee compensation and benefits 2,147 108 Accrued clinical trial costs 8,145 6,753 Accrued professional fees 6,767 1,636 Other 608 285 $ 31,167 $ 8,782

Liability Related to Sale of Fu

Liability Related to Sale of Future Royalties, net	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Liability Related to Sale of Future Royalties, net	Liability Related to Sale of Future Royalties, net In June 2018, the Company entered into a funding agreement (the "Funding Agreement") to sell tiered, sales-based royalty rights on global net sales of pharmaceutical products containing the compounds rimegepant or BHV-3500 and certain derivative compounds thereof ("Products") to RPI , a Delaware statutory trust. The Company issued to RPI the right to receive certain revenue participation payments, subject to certain reductions, based on the future global net sales of the Products for each calendar quarter during the royalty term contemplated by the Funding Agreement ("Revenue Participation Right"), in exchange for $100,000 in cash. Concurrent with the Funding Agreement, the Company entered into a common stock purchase agreement (the "Purchase Agreement") with RPI. Pursuant to the Purchase Agreement, the Company sold 1,111,111 common shares of the Company to RPI at a price of $45.00 per share, for gross proceeds of $50,000 . The Company concluded that there were two units of accounting for the consideration received comprised of the liability related to sale of future royalties and the common shares. The Company allocated the $100,000 from the Funding Agreement and $50,000 from the Purchase Agreement among the two units of accounting on a relative fair value basis at the time of the transaction. The Company allocated $106,047 in transaction consideration to the liability, and $43,953 to the common shares. The Company determined the fair value of the common shares based on the closing stock price on the transaction date, adjusted for the trading restrictions. The transaction costs of $377 were allocated in proportion to the allocation of total consideration to the two units of accounting. The effective interest rate under the Funding Agreement, including transaction costs, is approximately 22% as of June 30, 2019 . Biohaven recognized $5,151 and $501 in non-cash interest expense in the three months ended June 30, 2019 and 2018 , respectively, and $11,964 and $501 in non-cash interest expense in the six months ended June 30, 2019 and 2018

Mandatorily Redeemable Preferre

Mandatorily Redeemable Preferred Shares, net	6 Months Ended
	Jun. 30, 2019
Other Liabilities Disclosure [Abstract]
Mandatorily Redeemable Preferred Shares, net	Mandatorily Redeemable Preferred Shares, net In April 2019, the Company sold 2,495 Series A preferred shares (the "Series A Preferred Shares") to RPI at a price of $50,100 per preferred share pursuant to a Series A preferred share purchase agreement (the "Preferred Share Agreement"). The gross proceeds from the transaction with RPI were $125,000 , with $105,000 of the proceeds used to purchase a priority review voucher ("PRV") issued by the United States Secretary of Health and Human Services to potentially expedite the regulatory review of the new drug application ("NDA") for the ODT formulation of rimegepant and the remainder of the proceeds to be used for other general corporate purposes. Pursuant to the Preferred Share Agreement, the Company may issue additional Series A Preferred Shares to RPI in up to three additional closings for an aggregate amount of $75,000 subject to the acceptance by the FDA of both NDAs with respect to the tablet formulation of rimegepant and the NDA with respect to the ODT formulation of rimegepant. As a condition for the issuance of additional Series A Preferred Shares, one NDA must be accepted under the priority review designation pathway. The issuance of additional Series A Preferred Shares is also subject to customary closing conditions. Subject to the satisfaction of the applicable conditions under the Preferred Share Agreement, the issuance of additional Series A Preferred Shares is entirely at the Company’s option, and the Company is not obligated to issue any additional Series A Preferred Shares, subject to a fee up to $3,000 if not issued in total. The fee is reduced proportionally by the amount of additional Series A Preferred Shares issued up to the aggregate $75,000 , in which the fee is reduced to zero . The holders of the Company's outstanding Series A Preferred Shares, will have the right to require redemption of the shares in certain circumstances. If a Change of Control (as defined in the Company's memorandum and article of association) occurs on or before October 5, 2019, the Company will have the option to redeem the Series A Preferred Shares for one point five times ( 1.5 x) the original purchase price of the Series A Preferred Shares upon the closing of the Change of Control. If the Company does not elect to redeem the Series A Preferred Shares for 1.5 x the original purchase price at the closing of such Change of Control, then it would be required to redeem the Series A Preferred Shares for two times ( 2 x) the original purchase price, payable in equal quarterly installments following closing of the Change of Control through December 31, 2024. If a Change of Control occurs after October 5, 2019 and the Series A Preferred Shares have not previously been redeemed, the Company must redeem the Series A Preferred Shares for two times ( 2 x) the original purchase price of the Series A Preferred Shares payable in a lump sum at the closing of the Change of Control or in equal quarterly installments following the closing of the Change of Control through December 31, 2024. If an NDA for rimegepant is not approved by December 31, 2021, the holders of the Series A Preferred Shares have the option at any time thereafter to require the Company to redeem the Series A Preferred Shares for one point two times ( 1.2 x) the original purchase price of the Series A Preferred Shares. If no Change of Control has occurred, the Series A Preferred Shares have not previously been redeemed and (i) rimegepant is approved on or before December 31, 2024, following approval and starting one-year after approval, the Company must redeem the Series A Preferred Shares for two times ( 2 x) the original purchase price, payable in a lump sum or in equal quarterly installments through December 31, 2024 (provided that if rimegepant is approved in 2024, the entire redemption amount must be paid by December 31, 2024) or (ii) rimegepant is not approved by December 31, 2024, the Company must redeem the Series A Preferred Shares for two times ( 2 x) the original purchase price on December 31, 2024. The Company may redeem the Series A Preferred Shares at our option at any time for two times ( 2 x) the original purchase price, which redemption price may be paid in a lump sum or in equal quarterly installments through December 31, 2024. In the event that the Company defaults on any obligation to redeem Series A Preferred Shares when required, the redemption amount shall accrue interest at the rate of eighteen percent ( 18% ) per annum. If any such default continues for at least one year, the holders of such shares shall be entitled to convert, subject to certain limitations, such Series A Preferred Shares into common shares, with no waiver of their redemption rights. Under all circumstances, the Series A Preferred Shares are required to be redeemed by December 31, 2024. Accordingly, the Company has concluded the Series A Preferred Shares are mandatorily redeemable instruments and classified as a liability. The Company initially measured the liability at fair value, and will subsequently accrete the carrying value to the redemption value through interest expense using the effective interest rate method. The effective interest rate under the Preferred Share Agreement, including transaction costs, was determined to be approximately 18% , and the Company recognized $3,955 in interest expense for the three and six months ended June 30, 2019 . The Company had 2,495 and no Series A preferred shares issued and outstanding as of June 30, 2019 and December 31, 2018 , respectively. The following table shows the activity within the preferred share liability for the six months ended June 30, 2019 : Carrying Value Transaction date balance $ 91,185 Non-cash interest expense recognized, net of transaction cost amortization 3,945 Balance at June 30, 2019 95,130 Less: Unamortized transaction costs (240 ) Balance at June 30, 2019 $ 94,890 Certain scenarios as described in the Preferred Share Agreement were determined by the Company to result in a derivative liability . The with-and-without valuation method was used to determine the fair value of the embedded derivatives within the agreement. As inputs into the valuation, the Company considered the type and probability of occurrence of certain events, the amount of the payments, the expected timing of certain events, and a risk-adjusted discount rate. In accordance with ASC 815, Derivatives and Hedging, the fair value of the derivative was recorded on the balance sheet as a derivative liability with changes in fair value recorded in other income (expense) in the condensed consolidated statements of operations and comprehensive loss (see Note 3 for details on the fair value measurement). If factors change and different assumptions are used, the fair value of the derivative liability and related gains or losses could be materially different in the future. The Company recorded the payment for the PRV as research and development expense in the condensed consolidated statements of operations and comprehensive loss, and as an operating cash outflow in the condensed consolidated statements of cash flows for the six months ended June 30, 2019.

Warrants

Warrants	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Warrants	Warrants Guarantor and Co-Guarantor Warrants On August 30, 2016, the Company entered into a one-year credit agreement (the “Credit Agreement”) with Wells Fargo Bank, National Association. In connection with entering into the Credit Agreement, the Company issued warrants to purchase common shares to two of the Company’s directors in connection with a guarantee of its obligations under the agreement. The Company previously classified the warrants as a liability on its condensed consolidated balance sheet because each warrant represented a freestanding financial instrument that was not indexed to the Company’s own shares. The warrant liability was initially recorded at fair value upon entering into the Credit Agreement and was subsequently remeasured to fair value at each reporting date. On January 26, 2018, the anti-dilution price protection provisions contained within the warrants issued to each of the guarantor and co-guarantor of the Credit Agreement expired. Changes in the fair value of the warrant liability, until expiration of the anti-dilution price protection provisions, were recognized as a component of other income (expense), net, in the Company’s condensed consolidated statement of operations and comprehensive loss. Upon expiration of the provision, the Company discontinued classification of these warrants as a liability and has accordingly reclassified the fair value of $5,203 to additional paid-in capital within shareholders’ equity. The fair value of the warrant liability was $4,021 at December 31, 2017. The Company recorded expense of $1,182 related to the warrant liability within other income (expense) in the condensed consolidated statements of operations and comprehensive loss for the six months ended June 30, 2018 . Both warrants were exercised in March 2019. Fox Chase Chemical Diversity Center Inc. In May 2019, the Company entered into an agreement with Fox Chase Chemical Diversity Center Inc. ("FCCDC") for FCCDC's TDP-43 assets (the "FCCDC Agreement"). The FCCDC Agreement provides the Company with a plan and goal to identify one or more new chemical entity candidates for preclinical development for eventual clinical evaluation for the treatment of one or more TDP-43 proteinopathies. As consideration, Biohaven issued 100,000 of its common shares to FCCDC valued at $5,646 . As the shares were not settled during the second quarter of 2019, the Company recorded the payment in accounts payable, and research and development expense. In addition, Biohaven is obligated to pay FCCDC milestone payments totaling up to $4,500 with $1,000 for each additional NDA filing (See Note 12). The Company also issued a warrant to FCCDC, granting FCCDC the option to purchase up to 100,000 Biohaven common shares, at a strike price of $56.46 per share, subject to vesting upon achievement of certain milestones in development of TD-43. The warrant has standard terms and conditions for exercise and has accelerated vesting in the event of a change of control of Biohaven.

Shareholders' Equity

Shareholders' Equity	6 Months Ended
	Jun. 30, 2019
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Shareholders' Equity Changes in shareholders’ equity for the three and six months ended June 30, 2019 was as follows: Common Shares Shares Amount Additional Paid-in Capital Accumulated Deficit Total Shareholders' Equity (Deficit) Balances as of December 31, 2018 44,197,549 $ 554,384 $ 40,104 $ (443,568 ) $ 150,920 Exercise of stock options 85,445 1,961 (896 ) — 1,065 Non-cash share-based compensation expense — — 7,330 — 7,330 Net loss — — — (62,304 ) (62,304 ) Balances as of March 31, 2019 44,282,994 556,345 46,538 (505,872 ) 97,011 Issuance of common shares upon completion of equity offering, net of offering costs 6,976,745 281,100 — — 281,100 Exercise of related party warrants 215,000 7,201 (5,203 ) — 1,998 Exercise of stock options 26,875 320 (172 ) — 148 Share-based compensation expense — — 17,554 — 17,554 Net loss — — — (211,070 ) (211,070 ) Balances as of June 30, 2019 51,501,614 $ 844,966 $ 58,717 $ (716,942 ) $ 186,741 Changes in shareholders’ equity for the three and six months ended June 30, 2018 was as follows: Common Shares Shares Amount Additional Paid-in Capital Accumulated Deficit Total Shareholders' Equity (Deficit) Balances as of December 31, 2017 36,057,748 $ 311,061 $ 23,556 $ (202,646 ) $ 131,971 Issuance of common shares upon completion of equity offering, net of offering costs 2,000,000 52,013 — — 52,013 Exercise of ALS Biopharma warrants, net settlement of shares 228,219 — — — — Reclassification of warrant liability to equity — — 5,203 — 5,203 Exercise of stock options 321,050 4,656 (3,653 ) — 1,003 Non-cash share-based compensation expense — — 3,088 — 3,088 Net loss — — — (85,462 ) (85,462 ) Balances as of March 31, 2018 38,607,017 $ 367,730 $ 28,194 $ (288,108 ) $ 107,816 Issuance of common shares upon completion of equity offering, net of offering costs 1,111,111 43,842 — — 43,842 Exercise of ALS Biopharma warrants, net settlement of shares 261,140 — — — — Exercise of stock options 115,023 1,653 (820 ) — 833 Share-based compensation expense — — 5,608 — 5,608 Net loss — — — (39,269 ) (39,269 ) Balances as of June 30, 2018 40,094,291 $ 413,225 $ 32,982 $ (327,377 ) $ 118,830 Issuance of Common Shares for the June 2019 Offering In June 2019, the Company issued and sold 6,976,745 common shares at a public offering price of $ 43.00 per share for net proceeds of approximately $281,100 after deducting underwriting discounts and commissions of approximately $18,000 and other offering expenses of approximately $900 . In addition, in July 2019, the underwriters of the follow-on offering partially exercised their option to purchase additional shares, and the Company issued and sold 525,000 common shares for net proceeds of approximately $21,221 after deducting underwriting discounts and commissions of approximately $1,354 . Thus, the aggregate net proceeds to the Company from the follow-on offering, after deducting underwriting discounts and commissions and other offering costs, were approximately $302,321 . Exercise of Related Party Warrants In connection with a guarantee of its obligations under the Credit Agreement, the Company issued warrants, each to purchase 107,500 common shares at an exercise price of $9.2911 per share, to two of its directors. Both warrants were exercised in March 2019, and common shares settled in the second quarter of 2019 (See Note 9 ). Private Placement In March 2018, the Company sold an aggregate of 2,000,000 common shares in a private placement at a price of $27.50 per share, for net proceeds of $52,013 after deducting underwriting discounts and commissions of $2,800 and other offering expenses of $187 . Subsequent to the closing of the private placement, the Company paid Bristol-Myers Squibb Company ("BMS") the $50,000 upfront payment under an amendment (the "BMS Amendment") to the Company's July 2016 license agreement with BMS (the "BMS Agreement").See Note 12 for additional details. ALS Biopharma, LLC Warrant Exercise In January 2018, ALS Biopharma, LLC exercised a warrant for the purchase of 275,000 common shares through a net share settlement, resulting in an issuance of 228,219 common shares. In April 2018, ALS Biopharma exercised a warrant for the purchase of 325,000 common shares through a net share settlement, resulting in an issuance of 261,140 common shares.

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic and diluted net loss per share attributable to common shareholders of Biohaven Pharmaceutical Holding Company Ltd. was calculated as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Numerator: Net loss $ (211,070 ) $ (39,269 ) $ (273,374 ) $ (124,731 ) Denominator: Weighted average common shares outstanding—basic and diluted 45,226,434 38,942,545 44,736,971 37,873,755 Net loss per share attributable to common shareholders of Biohaven Pharmaceutical Holding Company Ltd.—basic and diluted $ (4.67 ) $ (1.01 ) $ (6.11 ) $ (3.29 ) The Company’s potential dilutive securities, which include stock options and warrants to purchase common shares, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common shareholders of the Company is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common shareholders for the periods indicated because including them would have had an anti-dilutive effect: As of June 30, 2019 2019 2018 Options to purchase common shares 8,306,459 6,019,570 Warrants to purchase common shares 106,751 221,751 8,413,210 6,241,321

License and Other Agreements

License and Other Agreements	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License and Other Agreements	License and Other Agreements Catalent Agreements for Rimegepant In January 2018, the Company entered into an exclusive world-wide license and development agreement with Catalent U.K. Swindon Zydis Limited, a subsidiary of Catalent , Inc. ("Catalent") pursuant to which the Company obtained certain license rights to the Zydis ODT technology for use with rimegepant. If the Company obtains regulatory approval or launches a rimegepant product that utilizes the Zydis ODT technology, the Company is obligated to pay Catalent up to $1,500 upon the achievement of specified regulatory and commercial milestones. If the Company commercializes a rimegepant product that utilizes the Zydis ODT technology, the agreement permits the Company to purchase the commercial product from Catalent at a fixed price, inclusive of a royalty. Under the agreement, Catalent will not develop or manufacture a formulation of any oral CGRP compound using Zydis ODT technology for itself or a third party until 2031, subject to certain minimum commercial revenues. Under this agreement, the Company is responsible for conducting clinical trials and preparing and filing regulatory submissions. The Company has the right to sublicense its rights under the agreement subject to Catalent’s prior written consent. Catalent has the right to enforce the patents covering the Zydis technology and to defend any allegation that a formulation using Zydis technology, such as rimegepant, infringes a third party’s patent. This agreement terminates on a country-by-country basis upon the later of (i) 10 years after the launch of the most recently launched product in such country and (ii) the expiration of the last valid claim covering each product in such country, unless earlier voluntarily terminated by the Company or by Catalent. This agreement automatically extends for one-year terms unless either party gives advance notice of intent to terminate. In addition, Catalent may terminate the agreement either in its entirety or terminate the exclusive nature of the agreement on a country-by-country basis if, among other things, the Company fails to meet specified development timelines, which the Company may extend in certain circumstances. Amendment to License Agreement with BMS In March 2018, the Company entered into the BMS Amendment. Under the BMS Amendment, the Company paid BMS an upfront payment of $50,000 in return for a low single-digit reduction in the royalties payable on net sales of rimegepant and a mid single-digit reduction in the royalties payable on net sales of BHV-3500, recorded in research and development expense in the condensed consolidated statements of operations and comprehensive loss. Under the original license agreement, the Company had been obligated to make tiered royalty payments based on annual worldwide net sales of licensed products upon their approval and commercialization, with percentages in the low- to mid-teens. The BMS Amendment also removed BMS’s right of first negotiation to regain its intellectual property rights or enter into a license agreement with the Company following the Company’s receipt of topline data from its Phase 3 clinical trials of rimegepant, and clarified that antibodies targeting CGRP are not prohibited as competitive compounds under the non-competition clause of the BMS Agreement. The BMS Agreement continues to provide the Company with exclusive global development and commercialization rights to rimegepant, BHV-3500 and related CGRP molecules, as well as related know-how and intellectual property. The Company’s obligations to make development and commercial milestone payments to BMS under the original license agreement remain unchanged. Biotech Value Advisors Agreement In March 2019, the Company entered into a master services agreement with Biotech Value Advisors, LLC related to the commercial preparation for several of the Company's late-stage product candidates. In addition to fixed quarterly consulting expenses under the agreement, the Company agreed to pay up to $2,000 upon achievement of specified commercial milestones. Fox Chase Chemical Diversity Center Inc. Agreement In May 2019, Biohaven entered into the FCCDC Agreement in which the Company purchased certain intellectual property relating to the TDP-43 protein from FCCDC. The FCCDC Agreement provides the Company with a plan and goal to identify one or more new chemical entity candidates for preclinical development for eventual clinical evaluation for the treatment of one or more TDP-43 proteinopathies. As consideration, Biohaven issued 100,000 of its common shares to FCCDC valued at $5,646 . As the shares were not settled during the second quarter of 2019, the Company recorded the share issuance in accounts payable and research and development expense. In addition, Biohaven is obligated to pay FCCDC milestone payments totaling up to $4,500 with $1,000 for each additional NDA filing. The Company also issued a warrant to FCCDC, granting FCCDC the option to purchase up to 100,000 Biohaven common shares, at a strike price of $56.46 per share, subject to vesting upon achievement of certain milestones in development of TD-43 (see Note 9). In connection with the FCCDC Agreement, Biohaven and FCCDC have established a TDP-43 Research Plan that provides for certain milestones to be achieved by FCCDC, and milestone payments to be made by the Company up to $1,500 over a period of up to 30 months as success fees for research activities by FCCDC. In addition to the milestone payments, the Company will pay FCCDC an earned royalty equal to zero to ten percent of net sales of any TD-43 patent products with a valid claim as defined in the FCCDC Agreement. The Company may also license the rights developed under the FCCDC Agreement and, if it does so, will be obligated to pay a portion of any payments received from such licensee to FCCDC in addition to any milestones payments it would otherwise be obligated to pay. The Company is also responsible for the prosecution and maintenance of the patents related to the TDP-43 assets. The FCCDC Agreement can be terminated on a country-by-country basis and product-by-product basis upon expiration of the royalty term for such product in such country. Each royalty term begins on the date of the first commercial sale of the licensed product in the applicable country and ends on the expiration of the last to expire of the applicable patents in that country. The FCCDC Agreement may be terminated earlier in specified situations, including termination for uncured material breach of the FCCDC Agreement by either party, termination by FCCDC in specified circumstances, termination by the Company on a country-by-country basis with advance notice and termination upon a party's insolvency or bankruptcy. Amendment to License Agreement with Yale In September 2013, the Company entered into an exclusive license agreement with Yale (the "Yale Agreement") to obtain a license to certain patent rights for the commercial development, manufacture, distribution, use and sale of products and processes resulting from the development of those patent rights, related to the use of riluzole in treating various neurological conditions, such as general anxiety disorder, post-traumatic stress disorder and depression. As part of the consideration for this license, the Company issued Yale 250,000 common shares and granted Yale the right to purchase up to 10% of the securities issued in specified future equity offerings by the Company, in addition to the obligation to issue shares to prevent anti-dilution. The obligation to contingently issue equity to Yale was no longer outstanding as of December 31, 2018. The Yale Agreement was amended and restated in May 2019. As amended, the Company agreed to pay Yale up to $2,000 upon the achievement of specified regulatory milestones and annual royalty payments of a low single-digit percentage based on net sales of riluzole-based products from the licensed patents or from products based on troriluzole. Under the amended and restated agreement, the royalty rates are reduced as compared to the original agreement. In addition, under the amended and restated agreement, the Company may develop products based on riluzole or troriluzole. The amended and restated agreement retains a minimum annual royalty of up to $1,000 per year, beginning after the first sale of product under the agreement. If the Company grants any sublicense rights under the Yale Agreement, it must pay Yale a low single-digit percentage of sublicense income that it receives. To date, no milestone or royalty payments have been made under this agreement. The Yale Agreement, as amended and restated, requires the Company to meet certain due diligence requirements based upon specified milestones relating to riluzole or troriluzole based products. The Company can elect to extend the deadline for its compliance with the due diligence requirements by a maximum of one year upon the payment to Yale of up to $150 . The Company is also required to reimburse Yale for any fees that Yale incurs related to the filing, prosecution, defending and maintenance of patent rights licensed under the Yale Agreement. In the event that the Company fails to make any payments, commits a material breach, fails to maintain adequate insurance or challenges the patent rights of Yale, Yale can terminate the Yale Agreement. The Company can terminate the Yale Agreement (i) upon 90 days' notice to Yale, (ii) if Yale commits a material breach of the Yale Agreement or (iii) as to a specific country if there are no valid patent rights in such country. The Yale Agreement expires on a country-by-country basis upon the later of the date on which the last patent rights expire in such country or ten years from the date of the first sale of a product incorporating the licensed patents or the Company’s patents relating to troriluzole. Termination of MGH Agreement In September 2014, the Company entered into a license agreement (the "MGH Agreement") with The General Hospital Corporation d/b/a Massachusetts General Hospital ("MGH"), pursuant to which MGH granted the Company a license to certain patent rights for the commercial development, manufacture, distribution and use of any products or processes resulting from development of those patent rights, related to treating depression with a combination of ketamine and scopolamine. The Company was obligated to pay MGH annual license maintenance fees and future milestone payments of up to $750 upon the achievement of specified clinical and regulatory milestones and up to $2,500 upon the achievement of specified commercial milestones. The Company had also agreed to pay MGH royalties between zero and ten percent based on net sales of products licensed under the agreement. In July 2019, the Company elected to terminate the agreement. Upon termination, the Company is no longer subject to future milestone or royalty payments under the MGH Agreement.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Summarized below are the matters previously described in Note 16 of the Notes to the Consolidated Financial Statements in the Company's Form 10-K for the year ended December 31, 2018, updated as applicable. Lease Agreements In August 2017, the Company entered into a lease agreement for office space and the related property for its headquarters in New Haven, Connecticut which it began occupying during the fourth quarter of 2018. The lease commenced on January 1, 2018 and had a term of 85 months, with the ability to extend to 120 months. The Company had the option to purchase the property for $2,700 and executed that option in December 2018 and therefore has no remaining lease obligation related to the building. The Company recorded the following for the lease agreement for its new headquarters during the construction period: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Rent expense $ 4 $ 36 Capitalized costs 814 1,379 License Agreements The Company has entered into license agreements with various parties under which it is obligated to make contingent and non-contingent payments. License agreements generally require the Company to pay annual maintenance fees and future payments upon the attainment of agreed upon development and/or commercial milestones. These agreements may also require minimum royalty payments based on sales of products developed from the applicable technologies, if any. Administration of intranasal BHV-3500 in a Phase 1 clinical trial was initiated in October 2018 and has achieved targeted therapeutic exposures. The compound advanced into a Phase 2/3 trial to evaluate efficacy for the acute treatment of migraine in the first quarter of 2019. Pursuant to the BMS Agreement, the Company is required to pay $2,000 to BMS on commencement of a Phase 1 clinical trial, and $4,000 on commencement of a Phase 2 clinical trial, and accordingly, the Company has recognized these liabilities as of December 31, 2018 and June 30, 2019 , respectively, in accrued expenses within the condensed consolidated balance sheets. The payment obligations under the agreement are deferred until the earlier of the first approval, or the discontinuation, of the development of rimegepant . Pursuant to the BMS Agreement, the Company is required to pay $7,500 to BMS in relation to the NDA filing for rimegepant, and accordingly, the Company has recognized this liability as of June 30, 2019 in accrued expenses within the condensed consolidated balance sheet. The Company expects to make this payment in the third quarter of 2019. Research Commitments The Company has entered into agreements with several contract research organizations to provide services in connection with its preclinical studies and clinical trials. The Company commits to minimum payments under these arrangements. Indemnification Agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with certain executive officers and members of its board of directors that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company’s amended and restated memorandum and articles of association also provide for indemnification of directors and officers in specified circumstances. To date, the Company has not incurred any material costs as a result of such indemnification provisions. The Company does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its condensed consolidated financial statements as of June 30, 2019 or December 31, 2018 . Legal Proceedings From time to time, in the ordinary course of business, the Company is subject to litigation and regulatory examinations as well as information gathering requests, inquiries and investigations. As of June 30, 2019 , there were no matters which would have a material impact on the Company’s financial results.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Guarantor and Co-Guarantor Warrants The guarantor and co-guarantor of the Credit Agreement with Wells Fargo are each shareholders and members of the board of directors of the Company. The Company issued warrants to the guarantor and co-guarantor in exchange for their respective guarantees (see Note 9 and 10 ). On January 26, 2017, each of these two directors received a warrant to purchase 107,500 common shares at an exercise price of $9.2911 per share. Both warrants were exercised in March 2019 and common shares settled in the second quarter of 2019.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of income and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the accrual for research and development expenses and the valuation of common shares, stock options, warrants, derivative instruments, contingent equity instruments, and non-cash interest expense on liability related to sale of future royalties. In addition, management’s assessment of the Company’s ability to continue as a going concern involves the estimation of the amount and timing of future cash inflows and outflows. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.
Fair Value Measurements	Fair Value Measurements Certain assets of the Company are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1— Quoted prices in active markets for identical assets or liabilities. • Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. • Level 3—Unobservable inputs that are supported by little or no market activity that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.
Unaudited Interim Condensed Consolidated Financial Information	Unaudited Interim Condensed Consolidated Financial Information The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America for interim financial information. The accompanying unaudited condensed consolidated financial statements do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America for complete consolidated financial statements. The accompanying year-end condensed consolidated balance sheet was derived from audited financial statements, but does not include all disclosures required by accounting principles generally accepted in the United States of America. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of June 30, 2019 and the results of its operations for the three and six months ended June 30, 2019 and 2018 and its cash flows for the six months ended June 30, 2019 and 2018 . The results for the three and six months ended June 30, 2019 are not necessarily indicative of results to be expected for the year ending December 31, 2019 , any other interim periods or any future year or period. The financial information included herein should be read in conjunction with the financial statements and notes in the Company's Annual Report on Form 10-K for the year ended December 31, 2018 .
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements Effective January 1, 2019, the Company adopted ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., 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 12 months regardless of their classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. In July of 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases (“ASU 2018-10”) , and ASU No. 2018-11, Leases (Topic 842): Targeted Improvements (“ASU 2018-11”), both of which clarified and enhanced the certain amendments made in ASU 2016-02 and were adopted by the Company in conjunction with ASU 2016-02. The adoption requires a modified retrospective transition approach, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (1) its effective date or (2) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. The Company has elected to adopt the standard using the effective date, January 1, 2019, as its date of initial application. Consequently, financial information will not be updated, and the disclosures required under the new standard will not be provided for dates and periods before January 1, 2019. Given that the Company had no material outstanding leases as of the date of the adoption, the adoption of ASU 2016-02 did not have a material impact on the Company's financial position or results of operations.

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Schedule of financial liability measured at fair value on a recurring basis	The following tables present information about the Company's financial liability measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair value: Fair Value Measurement as of June 30, 2019 Using: Level 1 Level 2 Level 3 Total Liabilities: Derivative liability $ — $ — $ 35,078 $ 35,078 $ — $ — $ 35,078 $ 35,078
Schedule of aggregate fair value of derivative liability determined by Level 3 inputs	The following table provides a roll forward of the aggregate fair value of the Company’s derivative liability for which fair value is determined by Level 3 inputs: Derivative Transaction date balance $ 33,815 Change in fair value 1,263 Balance at June 30, 2019 $ 35,078

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	6 Months Ended
	Jun. 30, 2019
Prepaid Expense and Other Assets, Current [Abstract]
Schedule of prepaid expenses and other current assets	Prepaid expenses and other current assets consisted of the following: As of June 30, 2019 As of December 31, 2018 Prepaid clinical trial costs $ 7,271 $ 7,210 Prepaid insurance 1,208 393 Other 134 487 $ 8,613 $ 8,090

Equity Method Investment (Table

Equity Method Investment (Tables)	6 Months Ended
	Jun. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Schedule of proportionate share of equity investment net loss	The Company recorded other expense and a corresponding reduction in the carrying value of its investment in Kleo as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Proportionate share of Kleo's net loss $ 1,415 $ 641 $ 2,315 $ 1,369
Schedule of carrying value of equity method investment	The following table provides a roll-forward of the carrying value of the Company’s equity method investment: Carrying Value Balance at December 31, 2018 $ 11,414 Loss recognized in connection with equity method investment (2,315 ) Balance at June 30, 2019 $ 9,099 Balance at December 31, 2017 $ 7,847 Purchases of Kleo common stock 1,375 Loss recognized in connection with equity method investment (1,369 ) Balance at June 30, 2018 $ 7,853

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2019
Payables and Accruals [Abstract]
Schedule of accrued expenses	Accrued expenses consisted of the following: As of June 30, 2019 As of December 31, 2018 Accrued development milestones payable (Note 13) $ 13,500 $ — Accrued employee compensation and benefits 2,147 108 Accrued clinical trial costs 8,145 6,753 Accrued professional fees 6,767 1,636 Other 608 285 $ 31,167 $ 8,782

Mandatorily Redeemable Prefer_2

Mandatorily Redeemable Preferred Shares, net (Tables)	6 Months Ended
	Jun. 30, 2019
Other Liabilities Disclosure [Abstract]
Schedule of activity within the preferred share liability	The following table shows the activity within the preferred share liability for the six months ended June 30, 2019 : Carrying Value Transaction date balance $ 91,185 Non-cash interest expense recognized, net of transaction cost amortization 3,945 Balance at June 30, 2019 95,130 Less: Unamortized transaction costs (240 ) Balance at June 30, 2019 $ 94,890

Shareholders' Equity (Tables)

Shareholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2019
Stockholders' Equity Note [Abstract]
Schedule of changes in shareholders' equity	Changes in shareholders’ equity for the three and six months ended June 30, 2019 was as follows: Common Shares Shares Amount Additional Paid-in Capital Accumulated Deficit Total Shareholders' Equity (Deficit) Balances as of December 31, 2018 44,197,549 $ 554,384 $ 40,104 $ (443,568 ) $ 150,920 Exercise of stock options 85,445 1,961 (896 ) — 1,065 Non-cash share-based compensation expense — — 7,330 — 7,330 Net loss — — — (62,304 ) (62,304 ) Balances as of March 31, 2019 44,282,994 556,345 46,538 (505,872 ) 97,011 Issuance of common shares upon completion of equity offering, net of offering costs 6,976,745 281,100 — — 281,100 Exercise of related party warrants 215,000 7,201 (5,203 ) — 1,998 Exercise of stock options 26,875 320 (172 ) — 148 Share-based compensation expense — — 17,554 — 17,554 Net loss — — — (211,070 ) (211,070 ) Balances as of June 30, 2019 51,501,614 $ 844,966 $ 58,717 $ (716,942 ) $ 186,741 Changes in shareholders’ equity for the three and six months ended June 30, 2018 was as follows: Common Shares Shares Amount Additional Paid-in Capital Accumulated Deficit Total Shareholders' Equity (Deficit) Balances as of December 31, 2017 36,057,748 $ 311,061 $ 23,556 $ (202,646 ) $ 131,971 Issuance of common shares upon completion of equity offering, net of offering costs 2,000,000 52,013 — — 52,013 Exercise of ALS Biopharma warrants, net settlement of shares 228,219 — — — — Reclassification of warrant liability to equity — — 5,203 — 5,203 Exercise of stock options 321,050 4,656 (3,653 ) — 1,003 Non-cash share-based compensation expense — — 3,088 — 3,088 Net loss — — — (85,462 ) (85,462 ) Balances as of March 31, 2018 38,607,017 $ 367,730 $ 28,194 $ (288,108 ) $ 107,816 Issuance of common shares upon completion of equity offering, net of offering costs 1,111,111 43,842 — — 43,842 Exercise of ALS Biopharma warrants, net settlement of shares 261,140 — — — — Exercise of stock options 115,023 1,653 (820 ) — 833 Share-based compensation expense — — 5,608 — 5,608 Net loss — — — (39,269 ) (39,269 ) Balances as of June 30, 2018 40,094,291 $ 413,225 $ 32,982 $ (327,377 ) $ 118,830

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Schedule of basic and diluted net loss per share	Basic and diluted net loss per share attributable to common shareholders of Biohaven Pharmaceutical Holding Company Ltd. was calculated as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Numerator: Net loss $ (211,070 ) $ (39,269 ) $ (273,374 ) $ (124,731 ) Denominator: Weighted average common shares outstanding—basic and diluted 45,226,434 38,942,545 44,736,971 37,873,755 Net loss per share attributable to common shareholders of Biohaven Pharmaceutical Holding Company Ltd.—basic and diluted $ (4.67 ) $ (1.01 ) $ (6.11 ) $ (3.29 )
Schedule of potentially anti-dilutive securities excluded from calculation of diluted net loss per share	The Company excluded the following potential common shares, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common shareholders for the periods indicated because including them would have had an anti-dilutive effect: As of June 30, 2019 2019 2018 Options to purchase common shares 8,306,459 6,019,570 Warrants to purchase common shares 106,751 221,751 8,413,210 6,241,321

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Schedule of lease agreement during construction period	The Company recorded the following for the lease agreement for its new headquarters during the construction period: Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Rent expense $ 4 $ 36 Capitalized costs 814 1,379

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Narrative (Details) - Recurring - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Financial assets at fair value	$ 0	$ 0
Financial liabilities at fair value	$ 35,078,000	$ 0

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Financial Liability Measured at Fair Value on Recurring Basis (Details) - Recurring - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Liabilities:
Derivative liability	$ 35,078,000
Financial liabilities at fair value	35,078,000	$ 0
Level 1
Liabilities:
Derivative liability	0
Financial liabilities at fair value	0
Level 2
Liabilities:
Derivative liability	0
Financial liabilities at fair value	0
Level 3
Liabilities:
Derivative liability	35,078,000
Financial liabilities at fair value	$ 35,078,000

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities - Roll Forward of Aggregate Fair Value Determined by Level 3 Inputs (Details) - USD ($) $ in Thousands	2 Months Ended
	Jun. 30, 2019	Apr. 30, 2019
Fair Value Disclosures [Abstract]
Transaction date balance		$ 33,815
Change in fair value	$ 1,263
Balance at end of period	$ 35,078

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid clinical trial costs	$ 7,271	$ 7,210
Prepaid insurance	1,208	393
Other	134	487
Total prepaid expenses and other current assets	$ 8,613	$ 8,090

Equity Method Investment - Stoc

Equity Method Investment - Stock Purchase Agreement with Kleo (Details) $ / shares in Units, $ in Thousands	Aug. 31, 2016shares	Aug. 29, 2016tranchedirector$ / sharesshares	Nov. 30, 2018USD ($)shares	Jan. 31, 2018USD ($)shares	Oct. 31, 2017USD ($)shares	Jun. 30, 2017USD ($)shares	Mar. 31, 2017USD ($)shares	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jan. 31, 2018shares
Equity Method Investment
Cash payment for purchase of equity method investment | $								$ 0	$ 1,375
Kleo
Equity Method Investment
Shares of Kleo common stock purchased (shares)			1,420,818		2,049,543
Cash payment for purchase of equity method investment | $			$ 5,000		$ 2,253
Shares of Kleo common stock purchased from co-founder (shares)							500,000
Cash payment for purchase of Kleo officer and stockholder shares | $							$ 250
Issuance of common shares for purchase of Kleo office and stockholder shares (shares)							32,500
Ownership percentage (percent)			41.90%
Kleo | Kleo Stock Purchase Agreement
Equity Method Investment
Shares to be purchased per stock purchase agreement (shares)		3,000,000
Additional shares to be purchased per stock purchase agreement (shares)		5,500,000
Price per share (in dollars per share) | $ / shares		$ 1
Shares of Kleo common stock purchased (shares)	3,000,000			1,375,000	1,375,000	1,375,000	1,375,000			5,500,000
Cash payment for purchase of equity method investment | $				$ 1,375	$ 1,375	$ 1,375	$ 1,375
Number of equal tranches of shares to be purchased | tranche		4
Shares to be purchased in equal tranches (shares)		1,375,000
Period of time shares begin to be purchased in equal tranches after initial closing		6 months
Period of time shares are purchased after initial purchase		3 months
Number to designate to Kleo's board of directors | director		2

Equity Method Investment - Expe

Equity Method Investment - Expense and Carrying Amount of Investment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Proportionate share of Kleo's net loss	$ 1,415	$ 641	$ 2,315	$ 1,369

Equity Method Investment - Roll

Equity Method Investment - Roll-forward of Carrying Value (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Carrying value of equity method investment
Beginning balance			$ 11,414	$ 7,847
Purchases of Kleo common stock			0	1,375
Loss recognized in connection with equity method investment	$ (1,415)	$ (641)	(2,315)	(1,369)
Ending balance	$ 9,099	$ 7,853	$ 9,099	$ 7,853

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accrued expenses
Accrued development milestones payable	$ 13,500	$ 0
Accrued employee compensation and benefits	2,147	108
Accrued clinical trial costs	8,145	6,753
Accrued professional fees	6,767	1,636
Other	608	285
Total accrued expenses	$ 31,167	$ 8,782

Liability Related to Sale of _2

Liability Related to Sale of Future Royalties, net - Narrative (Details) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2018USD ($)unit_of_accounting$ / sharesshares	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)$ / shares	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)$ / shares
Liability For Sale of Future Royalties [Line Items]
Proceeds from sale of common stock				$ 282,000	$ 55,000
Non-cash interest expense on liability related to sale of future royalties		$ (5,151)	$ (501)	$ (11,964)	(501)
RPI Agreement
Liability For Sale of Future Royalties [Line Items]
Units of accounting related to consideration received | unit_of_accounting	2
Transaction consideration allocated to liability	$ 106,047		106,047		106,047
Transaction consideration allocated to equity	43,953		43,953		43,953
Transaction costs	377		$ 377		$ 377
RPI Funding Agreement
Liability For Sale of Future Royalties [Line Items]
Proceeds from royalty agreement	$ 100,000
Effective interest rate (percent)		22.00%		22.00%
RPI Purchase Agreement
Liability For Sale of Future Royalties [Line Items]
Common stock issued (shares) | shares	1,111,111
Common stock sold, price per share (in dollars per share) | $ / shares	$ 45		$ 45		$ 45
Proceeds from sale of common stock	$ 50,000

Mandatorily Redeemable Prefer_3

Mandatorily Redeemable Preferred Shares, net - Narrative (Details)	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2019USD ($)closing$ / sharesshares	Jun. 30, 2019USD ($)shares	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)shares	Jun. 30, 2018USD ($)	Dec. 31, 2018shares
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Interest expense		$ 3,955,000	$ 0	$ 3,955,000	$ 0
Series A Preferred Shares
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Number of shares sold in transaction (in shares) | shares	2,495
Issuance price per share (in dollars per share) | $ / shares	$ 50,100
Gross proceeds from transaction	$ 125,000,000
Payment for priority review voucher	$ 105,000,000
Number of additional closings per share agreement, maximum | closing	3
Aggregate value of additional closings available per share agreement	$ 75,000,000
Maximum fee per share agreement for nonissuance of shares	3,000,000
Fee required per share agreement if all shares issued	$ 0
Redemption relative to original purchase price upon optional redemption	2
Annual interest rate upon default of redemption (percent)	18.00%
Effective interest rate (percent)		18.00%		18.00%
Interest expense		$ 3,955,000		$ 3,955,000
Mandatorily redeemable shares issued (in shares) | shares		2,495		2,495		0
Mandatorily redeemable shares outstanding (in shares) | shares		2,495		2,495		0
Series A Preferred Shares | Change of control on or before October 5, 2019
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Redemption relative to original purchase price upon optional redemption	1.5
Redemption relative to original purchase price upon required redemption	2
Series A Preferred Shares | Change of control after October 5, 2019
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Redemption relative to original purchase price upon required redemption	2
Series A Preferred Shares | NDA for rimegepant approved by December 31, 2021
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Redemption relative to original purchase price upon optional redemption	1.2
Series A Preferred Shares | No change of control and NDA for rimegepant approved on or before December 31, 2024
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Redemption relative to original purchase price upon required redemption	2
Series A Preferred Shares | NDA for rimegepant not approved by December 31, 2024
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Redemption relative to original purchase price upon required redemption	2

Mandatorily Redeemable Prefer_4

Mandatorily Redeemable Preferred Shares, net - Activity Within the Preferred Share Liability (Details) - USD ($) $ in Thousands	2 Months Ended
	Jun. 30, 2019	Apr. 30, 2019	Dec. 31, 2018
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Mandatorily redeemable preferred shares, net	$ 94,890		$ 0
Series A Preferred Shares
Financial Instruments Subject to Mandatory Redemption by Settlement Terms [Line Items]
Mandatorily redeemable preferred shares, transaction date balance		$ 91,185
Non-cash interest expense recognized, net of transaction cost amortization	3,945
Mandatorily redeemable preferred shares, gross	95,130
Less: Unamortized transaction costs	(240)
Mandatorily redeemable preferred shares, net	$ 94,890

Warrants - Narrative (Details)

Warrants - Narrative (Details) $ / shares in Units, $ in Thousands	Jan. 26, 2018USD ($)	Aug. 30, 2016director	May 31, 2019USD ($)$ / sharesshares	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Mar. 31, 2018USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2017USD ($)
Warrants
Reclassification of fair value of warrant liability to shareholders' equity	$ 5,203					$ 5,203
Fair value of warrant liability									$ 4,021
Expense related to warrant liability				$ 0	$ 0		$ 0	$ 1,182
Value of common stock issued				$ 281,100	$ 43,842	$ 52,013
Credit Agreement | Wells Fargo Term Loan
Warrants
Credit agreement term		1 year
Directors
Warrants
Number of directors to whom the Company agreed to issue warrants | director		2
FCCDC Warrants
Warrants
Number of securities called by warrants (shares) | shares			100,000
Exercise price of warrants (in dollars per share) | $ / shares			$ 56.46
FCCDC Agreement | Collaborative arrangement
Warrants
Common stock issued (shares) | shares			100,000
Value of common stock issued			$ 5,646
Development milestone payment to be paid			4,500
Development milestone payments to be paid per each additional NDA filing			$ 1,000

Shareholders' Equity - Changes

Shareholders' Equity - Changes in Shareholders' Equity (Details) - USD ($) $ in Thousands	Jan. 26, 2018	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 97,011	$ 150,920	$ 107,816	$ 131,971	$ 150,920	$ 131,971
Issuance of common shares upon completion of equity offering, net of offering costs		281,100		43,842	52,013
Exercise of warrants, net settlement of shares		1,998
Reclassification of warrant liability to equity	$ 5,203				5,203
Exercise of stock options		148	1,065	833	1,003
Non-cash share-based compensation expense		17,554	7,330	5,608	3,088
Net loss		(211,070)	(62,304)	(39,269)	(85,462)	(273,374)	(124,731)
Ending balance		186,741	97,011	118,830	107,816	186,741	118,830
Common Shares
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 556,345	$ 554,384	$ 367,730	$ 311,061	$ 554,384	$ 311,061
Beginning balance (in shares)		44,282,994	44,197,549	38,607,017	36,057,748	44,197,549	36,057,748
Issuance of common shares upon completion of equity offering, net of offering costs		$ 281,100		$ 43,842	$ 52,013
Issuance of common shares upon completion of equity offering, net of offering costs (in shares)		6,976,745		1,111,111	2,000,000
Exercise of warrants, net settlement of shares (in shares)		215,000		261,140	228,219
Exercise of warrants, net settlement of shares		$ 7,201
Exercise of stock options		$ 320	$ 1,961	$ 1,653	$ 4,656
Exercise of stock options (in shares)		26,875	85,445	115,023	321,050
Ending balance		$ 844,966	$ 556,345	$ 413,225	$ 367,730	$ 844,966	$ 413,225
Ending balance (in shares)		51,501,614	44,282,994	40,094,291	38,607,017	51,501,614	40,094,291
Additional Paid-in Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		$ 46,538	$ 40,104	$ 28,194	$ 23,556	$ 40,104	$ 23,556
Exercise of warrants, net settlement of shares		(5,203)
Reclassification of warrant liability to equity					5,203
Exercise of stock options		(172)	(896)	(820)	(3,653)
Non-cash share-based compensation expense		17,554	7,330	5,608	3,088
Ending balance		58,717	46,538	32,982	28,194	58,717	32,982
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance		(505,872)	(443,568)	(288,108)	(202,646)	(443,568)	(202,646)
Net loss		(211,070)	(62,304)	(39,269)	(85,462)
Ending balance		$ (716,942)	$ (505,872)	$ (327,377)	$ (288,108)	$ (716,942)	$ (327,377)

Shareholders' Equity - Narrativ

Shareholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended					2 Months Ended	6 Months Ended
	Jul. 31, 2019	Jun. 30, 2019	Apr. 30, 2018	Mar. 31, 2018	Jan. 31, 2018	Jul. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019
Common Shares [Line Items]
Other offering expenses							$ 517	$ 2,987
Public Offering
Common Shares [Line Items]
Common stock issued (shares)		6,976,745
Issuance price per share (in dollars per share)		$ 43					$ 43
Net proceeds from private placement stock issuance		$ 281,100
Underwriting discounts and commissions		18,000
Other offering expenses		$ 900
Private Placement
Common Shares [Line Items]
Common stock issued (shares)				2,000,000
Issuance price per share (in dollars per share)				$ 27.50
Net proceeds from private placement stock issuance				$ 52,013
Underwriting discounts and commissions				2,800
Other offering expenses				187
BMS Agreement
Common Shares [Line Items]
Upfront payment under the BMS Amendment				$ 50,000
ALS Biopharma
Common Shares [Line Items]
Exercise of warrants, net settlement of shares (shares)			325,000		275,000
Number of shares issued for exercise of warrants (in shares)			261,140		228,219
Subsequent Event | June 2019 Offering
Common Shares [Line Items]
Net proceeds from private placement stock issuance						$ 302,321
Subsequent Event | Over-Allotment Option
Common Shares [Line Items]
Common stock issued (shares)	525,000
Net proceeds from private placement stock issuance	$ 21,221
Underwriting discounts and commissions	$ 1,354
Credit Agreement Warrants [Member]
Common Shares [Line Items]
Number of securities called by warrants (shares)									107,500
Exercise price of warrants (in dollars per share)									$ 9.2911

Net Loss per Share - Calculatio

Net Loss per Share - Calculation of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net loss	$ (211,070)	$ (62,304)	$ (39,269)	$ (85,462)	$ (273,374)	$ (124,731)
Denominator:
Weighted average common shares outstanding - basic and diluted (shares)	45,226,434		38,942,545		44,736,971	37,873,755
Net loss per share attributable to common shareholders of Biohaven Pharmaceutical Holding Company Ltd - basic and diluted (in dollars per share)	$ (4.67)		$ (1.01)		$ (6.11)	$ (3.29)

Net Loss per Share - Antidiluti

Net Loss per Share - Antidilutive Securities Excluded from Computation of Net Loss per Share (Details) - shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Securities excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from calculation of diluted net loss per share	8,413,210	6,241,321
Options to purchase common shares
Securities excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from calculation of diluted net loss per share	8,306,459	6,019,570
Warrants to purchase common shares
Securities excluded from computation of diluted net loss per share
Anti-dilutive securities excluded from calculation of diluted net loss per share	106,751	221,751

License and Other Agreements (D

License and Other Agreements (Details) - USD ($) $ / shares in Units, $ in Thousands	May 09, 2019	May 31, 2019	Mar. 31, 2019	Mar. 31, 2018	Jan. 31, 2018	Sep. 30, 2014	Sep. 30, 2013	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2018
License and other agreements
Value of common stock issued								$ 281,100	$ 43,842	$ 52,013
FCCDC Warrants
License and other agreements
Number of securities called by warrants (shares)		100,000
Exercise price of warrants (in dollars per share)		$ 56.46
Catalent Agreement | Collaborative arrangement
License and other agreements
Last patent right expiration period (in years)					10 years
Automatic extension period (in years)					1 year
Catalent Agreement | Collaborative arrangement | Maximum
License and other agreements
Milestone payment to be paid upon regulatory achievement					$ 1,500
BMS Agreement
License and other agreements
Upfront payment under the BMS Amendment				$ 50,000
Biotech Value Advisors Agreement | Collaborative arrangement | Maximum
License and other agreements
Commercial milestone payment to be paid			$ 2,000
FCCDC Agreement | Collaborative arrangement
License and other agreements
Common stock issued (shares)		100,000
Value of common stock issued		$ 5,646
Development milestone payment to be paid		4,500
Development milestone payments to be paid per each additional NDA filing		1,000
Performance milestone payment to be paid		$ 1,500
Time period for payment of performance milestone		30 months
FCCDC Agreement | Collaborative arrangement | Minimum
License and other agreements
Earned royalty payment per agreement (percent)		0.00%
FCCDC Agreement | Collaborative arrangement | Maximum
License and other agreements
Earned royalty payment per agreement (percent)		10.00%
Yale Agreement | Collaborative arrangement
License and other agreements
Milestone payment to be paid upon regulatory achievement	$ 2,000
Common stock issued (shares)							250,000
Right to purchase securities in specified future equity offering (as a percent)							10.00%
Minimum annual royalty payment to be paid upon sale of product	$ 1,000
Notice period to terminate agreement	90 days
Yale Agreement | Collaborative arrangement | Maximum
License and other agreements
Extension of due diligence requirements (in years)	1 year
Amount of payment subject to due diligence extension	$ 150
MGH Agreement | Collaborative arrangement | Minimum
License and other agreements
Royalties to be paid per agreement (percent)						0.00%
MGH Agreement | Collaborative arrangement | Maximum
License and other agreements
Upfront payment under the BMS Amendment						$ 750
Commercial milestone payment to be paid						$ 2,500
Royalties to be paid per agreement (percent)						10.00%

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jan. 01, 2018
Other Commitments [Line Items]
Accrued clinical trial costs	$ 8,145	$ 6,753
New Headquarters, New Haven, CT
Other Commitments [Line Items]
Lease agreement, term (in months)			85 months
Renewal term (in months)			120 months
Value of property with option to purchase			$ 2,700
BMS Agreement | Required payment on commencement of Phase 1 clinical trial
Other Commitments [Line Items]
Accrued clinical trial costs	2,000	2,000
BMS Agreement | Required payment on commencement of Phase 2 clinical trial
Other Commitments [Line Items]
Accrued clinical trial costs	4,000	$ 4,000
BMS Agreement | Required payment related to Rimegepant NDA filing
Other Commitments [Line Items]
Accrued clinical trial costs	$ 7,500

Commitments and Contingencies_2

Commitments and Contingencies - Rent Expense and Capitalized Costs (Details) - New Headquarters, New Haven, CT - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018
Other Commitments [Line Items]
Rent expense	$ 4	$ 36
Capitalized costs	$ 814	$ 1,379

Related Party Transactions - Na

Related Party Transactions - Narrative (Details) - Directors	Jan. 26, 2017director$ / sharesshares
Related Party Transactions
Number of directors to whom the Company agreed to issue warrants | director	2
Guarantor and Co-Guarantor Warrants
Related Party Transactions
Number of securities called by warrants (shares) | shares	107,500
Exercise price of warrants (in dollars per share) | $ / shares	$ 9.2911