Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Mar. 31, 2019	Jun. 21, 2019	Sep. 28, 2018
Document And Entity Information
Entity Registrant Name	REPLIMUNE GROUP, INC.
Entity Central Index Key	0001737953
Document Type	10-K
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--03-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 184
Entity Small Business	false
Entity Shell Company	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		31,663,701
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Current assets:
Cash and cash equivalents	$ 25,704	$ 17,583
Short-term investments	109,107	43,968
Research and development incentives receivable	2,474	2,389
Prepaid expenses and other current assets	3,696	763
Total current assets	140,981	64,703
Property and equipment, net	12,159	370
Restricted cash	1,186	78
Total assets	154,326	65,151
Current liabilities:
Accounts payable	7,084	1,993
Accrued expenses and other current liabilities	2,801	3,171
Total current liabilities	9,885	5,164
Deferred rent, net of current portion	24	52
Warrant liability	0	1,642
Financing obligation	6,561
Total liabilities	16,470	6,858
Commitments and contingencies (Note 13)
Convertible preferred stock (Series Seed, A and B), $0.001 par value; 0 and 1,975,968 shares authorized as of March 31, 2019 and 2018, respectively; 0 and 1,925,968 shares issued and outstanding as of March 31, 2019 and 2018, respectively		86,361
Stockholders' Equity (Deficit)
Common stock, $0.001 par value; 150,000,000 and 27,314,288 shares authorized (inclusive of 0 and 26,258 shares of common A stock) as of March 31, 2019 and 2018, respectively; 31,656,950 and 5,007,485 shares issued and outstanding (inclusive of 0 and 26,258 shares of common A stock) as of March 31, 2019 and 2018, respectively	32	5
Additional paid-in capital	198,645	1,097
Accumulated deficit	(59,766)	(28,932)
Accumulated other comprehensive loss	(1,055)	(238)
Total stockholders' equity (deficit)	137,856	(28,068)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$ 154,326	$ 65,151

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2019	Mar. 31, 2018
Convertible preferred stock (series seed, A and B), par value (in dollars per share)	$ 0.001	$ 0.001
Convertible preferred stock (series seed, A and B), authorized	0	1,975,968
Convertible preferred stock (series seed, A and B), issued	0	1,925,968
Convertible preferred stock (series seed, A and B), outstanding	0	1,925,968
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized	150,000,000	27,314,288
Common stock, issued	31,656,950	5,007,485
Common stock, outstanding	31,656,950	5,007,485
Common A stock
Common stock, authorized	0	26,258
Common stock, issued	0	26,258
Common stock, outstanding	0	26,258

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Operating expenses:
Research and development	$ 22,173	$ 13,516	$ 6,936
General and administrative	8,773	5,713	2,711
Total operating expenses	30,946	19,229	9,647
Loss from operations	(30,946)	(19,229)	(9,647)
Other income (expense):
Research and development incentives	2,528	2,267	1,442
Investment income	2,585	288	25
Change in fair value of warrant liability	(5,452)	(972)	(150)
Other income (expense), net	451	(2,056)	626
Total other income (expense), net	112	(473)	1,943
Net loss	(30,834)	(19,702)	(7,704)
Net loss attributable to common shareholders	$ (30,834)	$ (19,702)	$ (7,704)
Net loss per share attributable to common shareholders, basic and diluted (in dollars per share)	$ (1.33)	$ (3.96)	$ (1.55)
Weighted average common shares outstanding-basic and diluted (in shares)	23,198,400	4,978,539	4,973,439

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS
Net loss	$ (30,834)	$ (19,702)	$ (7,704)
Other comprehensive income (loss):
Foreign currency translation gain (loss)	(897)	2,376	(1,437)
Net unrealized gain (loss) on short-term investments, net of tax	80	(65)
Comprehensive loss	$ (31,651)	$ (17,391)	$ (9,141)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Convertible preferred stock (as converted to common stock)	Series B convertible Preferred Stock	Common A stock Common stock	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive loss	Total
Balance at Mar. 31, 2017	$ 31,609
Balance (in shares) at Mar. 31, 2017	1,064,553
Increase (decrease) in Temporary Equity
Issuance of series convertible preferred stock, net of issuance costs		$ 54,752
Issuance of series convertible preferred stock, net of issuance costs (in shares)		861,415
Balance at Mar. 31, 2018	$ 86,361							$ 86,361
Balance (in shares) at Mar. 31, 2018	1,925,968							1,925,968
Balance at Mar. 31, 2017				$ 5	$ 259	$ (9,230)	$ (2,549)	$ (11,515)
Balance (in shares) at Mar. 31, 2017				4,973,439
Increase (decrease) in Stockholders' Equity
Issuance of common stock upon closing of initial public offering, net of issuance costs and underwriter fees of $9,935 (shares)			26,258
Foreign currency translation adjustment							2,376	2,376
Unrealized gain (loss) on shortterm investments, net of tax							(65)	(65)
Stock options in exchange for consulting services					26			26
Stock options in exchange for consulting services (in shares)				7,788
Stock-based compensation expense					812			812
Net loss						(19,702)		(19,702)
Balance at Mar. 31, 2018				$ 5	1,097	(28,932)	(238)	$ (28,068)
Balance (in shares) at Mar. 31, 2018				5,007,485
Balance (in shares) at Mar. 31, 2019								0
Increase (decrease) in Stockholders' Equity
Conversion of convertible preferred stock into common stock upon closing of initial public offering	$ (86,361)			$ 19	86,342			$ 86,361
Conversion of convertible preferred stock into common stock upon closing of initial public offering (in shares)	(1,925,968)			19,157,360
Conversion of convertible preferred stock warrants into common stock warrants					7,094			7,094
Repurchase of class A common stock upon closing of initial public offering (in shares)				(26,258)
Issuance of common stock upon closing of initial public offering, net of issuance costs and underwriter fees of $9,935				$ 7	101,177			101,184
Issuance of common stock upon closing of initial public offering, net of issuance costs and underwriter fees of $9,935 (shares)				7,407,936
Exercise of stock options				$ 1	205			$ 206
Exercise of stock options (in shares)				110,427				110,427
Foreign currency translation adjustment							(897)	$ (897)
Unrealized gain (loss) on shortterm investments, net of tax							80	80
Stock-based compensation expense					2,730			2,730
Net loss						(30,834)		(30,834)
Balance at Mar. 31, 2019				$ 32	$ 198,645	$ (59,766)	$ (1,055)	$ 137,856
Balance (in shares) at Mar. 31, 2019				31,656,950

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net loss	$ 30,834	$ 19,702	$ 7,704
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	2,730	812	208
Depreciation and amortization	148	109	122
Change in fair value of warrant liability	5,452	972	150
Stock options in exchange for consulting services		26
Net amortization of premiums and discounts on shortterm investments	(1,715)	(123)
Non-cash rent expense	93
Changes in operating assets and liabilities:
Research and development incentives receivable	(255)	(767)	(1,210)
Prepaid expenses and other current assets	(801)	(305)	(325)
Accounts payable	120	1,596	203
Accrued expenses and other current liabilities	(292)	1,393	1,406
Deferred rent	(24)	(25)	73
Net cash used in operating activities	(25,378)	(16,014)	(7,077)
Cash flows from investing activities:
Purchases of property, plant and equipment	(2,600)	(136)	(238)
Purchase of short-term investments	(189,931)	(52,463)
Proceeds from sales and maturities of short-term investments	126,587	8,553
Net cash used in investing activities	(65,944)	(44,046)	(238)
Cash flows from financing activities:
Proceeds from issuance of common stock in initial public offering, net of underwriting fees and discounts	103,341
Exercise of stock options	206
Payment of issuance costs	(2,157)
Net cash provided by financing activities	101,390	54,752	15,000
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(839)	2,297	(1,419)
Net increase in cash, cash equivalent and restricted cash	9,229	(3,011)	6,266
Cash, cash equivalents and restricted cash at beginning of period	17,661	20,672	14,406
Cash, cash equivalents and restricted cash at end of period	26,890	17,661	20,672
Supplemental disclosure of non-cash investing and financing activities:
Net unrealized gain (loss) on short term investments	80	(65)
Purchases of property and equipment included in accounts payable	5,047
Conversion of preferred stock into common stock	86,361
Conversion of convertible preferred stock warrants into common stock warrants	7,094
Amounts capitalized under build-to-suit lease transaction	$ 4,292
Series A convertible Preferred Stock
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net of issuance costs			$ 15,000
Series B convertible Preferred Stock
Cash flows from financing activities:
Proceeds from issuance of convertible preferred stock, net of issuance costs		54,752
Payment of issuance costs		$ (198)

Nature of the business	12 Months Ended
Nature of the business	Mar. 31, 2019
Nature of the business
Nature of the business	1. Nature of the business Replimune Group, Inc. (the “Company”) is a clinical‑stage biotechnology company focused on the development of oncolytic immunotherapies to treat cancer. Replimune Limited (“Replimune UK”) was incorporated in 2015 under the laws of England, and was the sole shareholder of Replimune, Inc. (“Replimune US”), a Delaware corporation. On July 5, 2017, Replimune Group, Inc., a Delaware corporation, was incorporated and on July 10, 2017 the shareholders of Replimune UK effected a share‑for‑share exchange pursuant to which they exchanged their outstanding shares in Replimune UK for shares in Replimune Group, Inc., on a one‑for‑one basis. In addition, the holders of warrants and stock options to purchase Replimune UK capital stock canceled their warrants to purchase shares of series seed preferred stock and stock options in Replimune UK and were issued replacement warrants to purchase shares of series seed preferred stock and stock options to acquire Replimune Group, Inc. capital stock on a one‑for‑one basis. These transactions are collectively referred to as the reorganization. Upon completion of the reorganization, the historical consolidated financial statements of Replimune UK became the historical consolidated financial statements of Replimune Group, Inc. because the reorganization was accounted for similar to a reorganization of entities under common control due to the high degree of common ownership of Replimune UK and Replimune Group, Inc. and lack of economic substance to the transaction. The Company concluded that the reorganization resulted in no change in the material rights and preferences of each respective class of equity interests and no change in the fair value of each respective class of equity interests before and after the reorganization. On December 8, 2017, Replimune UK transferred all outstanding shares of its wholly owned subsidiary, Replimune US to Replimune Group, Inc. Replimune Group. Inc., a Delaware corporation, is the sole shareholder of Replimune UK, Replimune US and Replimune Securities Corporation, a Massachusetts corporation that was incorporated in November 2017. The Company is subject to risks and uncertainties common to early‑stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. 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 require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance and reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. Forward stock split On July 9, 2018, the Company effected a 1‑for‑9.94688 forward stock split of its issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for each series of the Company’s Preferred Stock (see Note 7). Accordingly, all share and per share amounts for all periods presented in the accompanying consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect this forward stock split and adjustment of the preferred stock conversion ratios. Further, on July 9, 2018, the Company’s authorized shares of common stock were increased to 27,314,288. Accordingly, the authorized shares of common stock presented in the accompanying consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect the newly authorized shares of common stock. Initial public offering On July 24, 2018, the Company completed an initial public offering (“IPO”) of its common stock and issued and sold 6,700,000 shares of common stock at a public offering price of $15.00 per share, resulting in net proceeds of $93,465 after deducting underwriting discounts and commissions but before deducting offering costs of $2,157. Upon closing of the IPO, the Company’s outstanding convertible preferred stock automatically converted into shares of common stock (see Note 7). Upon conversion of the convertible preferred stock, the Company reclassified the carrying value of the convertible preferred stock to common stock and additional paid-in capital. The warrant to purchase shares of the Company’s series seed convertible preferred stock was converted into a warrant to purchase shares of the Company’s common stock upon the closing of the IPO. As a result, the warrant liability was remeasured a final time on the closing date of the IPO and reclassified to stockholders’ equity (deficit). Additionally, the Company repurchased 26,258 shares of class A common stock at a price equal to its par value upon the closing of the IPO. On July 30, 2018, the Company issued and sold an additional 707,936 shares of its common stock at the IPO price of $15.00 per share pursuant to the underwriters’ partial exercise of their option to purchase additional shares of common stock, resulting in additional net proceeds of $9,876 after deducting discounts and commissions and other offering expenses. Also, in connection with the completion of its IPO on July 24, 2018, the Company filed an amended and restated certificate of incorporation with the Secretary of State of the State of Delaware to authorize the issuance of up to 150,000,000 shares of common stock, par value $0.001 per share, and 10,000,000 shares of undesignated preferred stock, par value $0.001 per share. Basis of presentation The accompanying consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company has incurred recurring losses since its inception, including net losses of $30,834, $19,702 and $7,704 for the years ended March 31, 2019, 2018 and 2017, respectively. In addition, as of March 31, 2019, the Company had an accumulated deficit of $59,766. The Company expects to continue to generate operating losses for the foreseeable future. As of June 28, 2019, the issuance date of these consolidated financial statements, the Company expects that its cash and cash equivalents and short-term investments will be sufficient to fund its operating expenses and capital expenditure requirements through at least 12 months from the issuance of the consolidated financial statements. The future viability of the Company beyond that point is dependent on its ability to raise additional capital to finance its operations. If the Company is unable to obtain funding it could be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects, or it may be unable to continue operations. Although management continues to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations, if at all.

Summary of significant accounting policies

12 Months Ended

Mar. 31, 2019

Summary of significant accounting policies

Summary of significant accounting policies

2. Summary of significant accounting policies

Principles of consolidation

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP, and include the accounts of the Company and its wholly owned subsidiaries, Replimune UK, Replimune US and Replimune Securities Corporation, after elimination of all intercompany accounts and transactions. The consolidated financial statements reflect the capital as if Replimune Group, Inc. had been in existence for all periods presented.

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 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 stock and stock‑based awards. The Company bases its estimates on historical experience, known trends and other market‑specific or other relevant factors that it believes to be reasonable under the circumstances. Estimates are periodically reviewed in light of reasonable 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 or assumptions.

Foreign currency and currency translation

The functional currency for the Company’s wholly owned foreign subsidiary, Replimune UK, is the British pound. Assets and liabilities of Replimune UK are translated into United States dollars at the exchange rate in effect on the balance sheet date. Revenues and expenses are translated at the average exchange rate in effect during the period. Unrealized translation gains and losses are recorded as a cumulative translation adjustment, which is included in the consolidated statements of convertible preferred stock and stockholders’ equity (deficit) as a component of accumulated other comprehensive loss. Adjustments that arise from exchange rate changes on transactions denominated in a currency other than the local currency are included in other income (expense), net in the consolidated statements of operations as incurred.

Concentrations of credit risk and of significant suppliers

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and cash equivalents as well as short‑term investments. The Company deposits its cash in financial institutions in amounts that may exceed federally insured limits, and has not experienced any losses on such accounts and does not believe it is exposed to any unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

The Company relies, and expects to continue to rely, on a small number of vendors to manufacture supplies and raw materials for its development programs. These programs could be adversely affected by a significant interruption in these manufacturing services or the availability of raw materials.

Cash and cash equivalents

The Company considers all highly liquid investments with original maturities of three months or less at date of purchase to be cash equivalents. Cash equivalents consisted of money market funds, US Treasury bonds, and US Government Agency bonds at March 31, 2019. Cash equivalents consisted of money market funds at March 31, 2018. As of March 31, 2019 and 2018, cash equivalents totaled $10,664 and $4,130, respectively.

Restricted Cash

The Company maintains certain minimum balances in segregated bank accounts in connection with its corporate credit cards and a letter of credit for the benefit of the landlords in connection with an operating lease. As of March 31, 2019 and 2018, restricted cash consisted of $0 and $78, respectively, held in connection with the Company’s corporate credit cards and $1,186 and $0, respectively, held for the benefit of the landlords in connection with an operating lease. These amounts have been classified as non-current assets on the Company’s consolidated balance sheets.

Short‑term investments

The Company’s short‑term debt security investments are classified as available‑for‑sale and are carried at fair value, with the unrealized gains and losses reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity (deficit). Realized gains and losses and declines in value determined to be other than temporary are based on the specific identification method and are included as a component of other income (expense), net in the consolidated statements of operations.

The Company evaluates its short-term debt security investments with unrealized losses for other-than-temporary impairment. When assessing short-term debt security investments for other-than-temporary declines in value, the Company considers such factors as, among other things, how significant the decline in value is as a percentage of the original cost, how long the market value of the investment has been less than its original cost, the Company’s ability and intent to retain the short-term debt security investment for a period of time sufficient to allow for any anticipated recovery in fair value and market conditions in general. If any adjustment to fair value reflects a decline in the value of the short-term debt security investment that the Company considers to be “other than temporary,” the Company reduces the short-term debt security investment to fair value through a charge to the consolidated statements of operations. No such adjustments were necessary during the periods presented.

The Company’s short‑term debt security investments as of March 31, 2019 and 2018 had original maturities of less than one year.

Deferred offering costs

The Company capitalizes certain legal, professional accounting and other third‑party fees that are directly associated with in‑process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ equity (deficit) as a reduction of proceeds generated as a result of the offering. Should an in‑process equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statements of operations. The Company did not record any deferred offering costs as of March 31, 2018. As of March 31, 2019, the Company recorded $2,157 of deferred offering costs in stockholders’ equity (deficit) as a reduction of proceeds generated as a result of the IPO.

Property, plant and equipment

Property, plant and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight‑line method over the estimated useful lives of the respective assets as follows:


		Estimated Useful life
Office equipment		5 years
Computer equipment		3 years
Plant and laboratory equipment		5 years
Leasehold improvements		Lesser of lease term or 10 years

Costs for capital assets not yet placed into service are capitalized as construction‑in‑progress and depreciated in accordance with the above guidelines once placed into service. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred.

Impairment of long‑lived assets

Long‑lived assets consist of property, plant and equipment. Long‑lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long‑lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long‑lived asset group to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value, determined based on discounted cash flows. To date, the Company has not recorded any impairment losses on long‑lived assets.

Deferred rent

The Company recognizes rent expense on a straight‑line basis over the respective lease terms and has recorded deferred rent for rent expense incurred but not yet paid.

Fair value measurements

Certain assets and liabilities 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 short‑term investments, cash equivalents and warrant liability are carried at fair value, determined according to the fair value hierarchy described above (see Note 3). The carrying values of research and development incentives receivable, other current assets, accounts payable and accrued expenses and other current liabilities approximate their fair values due to the short‑term nature of these assets and liabilities.

Warrant liability

Upon the closing of the IPO, the warrants to purchase shares of the Company’s series seed convertible preferred stock were converted into warrants to purchase shares of the Company’s common stock. As a result, the warrant liability was remeasured a final time on the closing date of the IPO and reclassified to stockholders’ equity (deficit).

Prior to the IPO, the Company classified warrants to purchase shares of series seed preferred stock (see Note 8) as a liability on its consolidated balance sheets as these warrants to purchase shares of series seed preferred stock were free-standing financial instruments that could require the Company to transfer assets upon exercise. The warrant liability was initially recorded at fair value upon the date of the warrants’ issuance and was subsequently remeasured to fair value at each reporting date. Changes in the fair value of the warrant liability were recognized as a component of total other income (expense), net in the consolidated statements of operations.

The Company utilized the Black-Scholes option-pricing model, which incorporated assumptions and estimates, to value the warrant liability. The Company assessed these assumptions and estimates on a quarterly basis as additional information impacting assumptions was obtained. Estimates and assumptions impacting the fair value measurement included the expected stock price volatility, the expected term of the warrant, the risk-free interest rate for a period that approximated the expected term of the warrant, and the Company’s expected dividend yield (see Note 3).

Segment information

The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions. The Company’s current focus is on developing oncolytic immunotherapies for the treatment of cancer.

Research and development costs

Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred in performing research and development activities, including salaries, stock‑based compensation and benefits, facilities costs and laboratory supplies, depreciation and external costs of outside vendors engaged to conduct preclinical development, clinical development activities and clinical trials as well as to manufacture clinical trial materials. Non‑refundable prepayments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized. Such amounts are recognized as an expense as the goods are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered or the services rendered.

Research contract costs and accruals

The Company has entered into various research and development‑related contracts with companies both inside and outside of the United States. These agreements are generally cancelable, and related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent costs

All patent‑related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Stock‑based compensation

The Company measures all stock‑based awards granted to employees and directors based on the fair value on the date of the grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award. The fair value of each stock option grant is estimated on the date of grant using the Black‑Scholes option‑pricing model, which requires inputs based on certain subjective assumptions, including the expected stock price volatility, the expected term of the option, the risk‑free interest rate for a period that approximates the expected term of the option, and the Company’s expected dividend yield (see Note 10). Forfeitures are accounted for as they occur. To date, the Company has issued stock‑based awards with only service‑based vesting conditions and records the expense for these awards using the straight‑line method.

For stock‑based awards granted to consultants and non‑employees, compensation expense is recognized over the shorter of the vesting period or the period during which services are rendered by such consultants and non‑employees until completed. At the end of each financial reporting period prior to completion of the service, the fair value of these awards is remeasured using the then‑current fair value of the Company’s common stock and updated assumption inputs in the Black‑Scholes option‑pricing model.

The Company classifies stock‑based compensation expense in its consolidated statements of operations in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

Research and development incentives and receivable

The Company, through its subsidiary in the United Kingdom, receives reimbursements of certain research and development expenditures as part of a United Kingdom government’s research and development tax reliefs program. Under the program, a percentage of qualifying research and development expenses incurred by the Company’s subsidiary in the United Kingdom are reimbursed up to 14.5%.

Management has assessed the Company’s research and development activities and expenditures to determine which activities and expenditures are likely to be eligible under the research and development incentive program described above. At each period end, management estimates the reimbursement available to the Company based on available information at the time.

The Company recognizes income from the research and development incentives when the relevant expenditure has been incurred, the associated conditions have been satisfied and there is reasonable assurance that the reimbursement will be received. The Company records these research and development incentives as other income. The research and development incentives receivable represents an amount due in connection with the above program. The Company recorded other income from research and development incentives of $2,528, $2,267 and $1,442 during the years ended March 31, 2019, 2018 and 2017, respectively, in the consolidated statements of operations and a research and development incentives receivable of $2,474 and $2,389 as of March 31, 2019 and 2018, respectively, on the consolidated balance sheets.

Comprehensive loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity (deficit) that result from transactions and economic events other than those with stockholders. For the year ended March 31, 2019, comprehensive loss included $(897) of foreign currency translation adjustments and $80 of unrealized gains on short-term investments, net of tax. For the year ended March 31, 2018, comprehensive loss included $2,376 of foreign currency translation adjustments and $(65) of unrealized losses on short‑term investments, net of tax. For the year ended March 31, 2017, comprehensive loss included $(1,437) of foreign currency translation adjustments.

Income taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred tax assets and liabilities are determined on the basis of the differences between the consolidated financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two‑step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more‑likely‑than‑not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Net income (loss) per share

The Company follows the two‑class method when computing net income (loss) per share as the Company has issued shares that meet the definition of participating securities. The two‑class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two‑class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed.

Basic net income (loss) per share attributable to common stockholders is computed by dividing the net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net income (loss) attributable to common stockholders is computed by adjusting net income (loss) attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share attributable to common stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents.

The Company’s convertible preferred stock contractually entitled the holders of such shares to participate in dividends but contractually did not require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reported a net loss, such losses were not allocated to such participating securities. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.

Recently Adopted Accounting Pronouncements

In May 2017, the FASB issued ASU No. 2017-09, Compensation—Stock Compensation (Topic 718): Scope of Modification Accounting (“ASU 2017-09”), which clarifies when to account for a change to the terms or conditions of a share-based payment award as a modification. Under the new guidance, modification accounting is required only if the fair value, the vesting conditions, or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The standard is effective for annual periods beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. The Company adopted ASU 2017-09 as of the required effective date of April 1, 2018 and will apply to any changes to the terms or conditions of share-based payment awards prospectively. The adoption of ASU 2017-09 did not have a material impact on the Company’s financial position, results of operations, or cash flows.

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (“ASU 2016-18”), which requires restricted cash to be presented with cash and cash equivalents on the consolidated statements of cash flows and disclosure of how the consolidated statements of cash flows reconciles to the balance sheet if restricted cash is shown separately from cash and cash equivalents on the balance sheet. The standard is effective for annual periods beginning after December 15, 2017, including interim periods within those fiscal years. Early adoption is permitted. The Company adopted ASU 2016-18 as of April 1, 2018. Restricted cash is now included as a component of cash, cash equivalents and restricted cash on the Company’s consolidated statement of cash flows. Upon the adoption of ASU 2016-18, the amount of cash and cash equivalents previously presented on the consolidated statements of cash flows reflects the inclusion of restricted cash in the amount reported for changes in cash, cash equivalents and restricted cash. Additionally, as a result of the adoption, transfers between restricted and unrestricted cash are no longer presented as a component of the Company’s investing activities. The adoption of ASU 2016-08 did not have a material impact on the Company’s financial position, results of operations, or cash flows. On the statement of cash flows for the years ended March 31, 2018 and 2017, the Company reclassified restricted cash of $78 and $75, respectively, to be included in Cash, cash equivalents and restricted cash at beginning of year and Cash, cash equivalents and restricted cash at end of year.

In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfer of Assets Other than Inventory (“ASU 2016-16”), which requires the recognition of the income tax consequences of an intra-entity transfer of an asset, other than inventory, when the transfer occurs. The standard is effective for annual periods beginning after December 15, 2017, including interim periods within those fiscal years. The Company adopted ASU 2016-16 as of the required effective date of April 1, 2018. The adoption of ASU 2016-16 did not have a material impact on the Company’s financial position, results of operations or cash flows.

In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments (“ASU 2016-15”), to address diversity in practice in how certain cash receipts and cash payments are presented and classified in the consolidated statements of cash flows. The standard is effective for annual periods beginning after December 15, 2017, including interim periods within those fiscal years. The Company adopted ASU 2016-16 as of the required effective date of April 1, 2018. The adoption of ASU 2016-15 did not have a material impact on the Company’s financial position, results of operations or cash flows.

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes existing revenue recognition guidance under GAAP. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. The standard defines a five-step process to achieve this principle, and will require companies to use more judgment and make more estimates than under the current guidance. The Company expects that these judgments and estimates will include identifying performance obligations in the customer contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, which delays the effective date of ASU 2014-09 such that the standard is effective for public entities for annual periods beginning after December 15, 2017 and for interim periods within those fiscal years. Early adoption of the standard is permitted for annual periods beginning after December 15, 2016. The Company adopted ASU 2014-09 on a full retrospective basis effective April 1, 2018. The adoption of ASU 2014-09 did not have an impact on the Company’s consolidated financial statements as the Company does not currently have any revenue-generating arrangements.

Recently Issued Accounting Pronouncements

In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (“ASU2018-18”), which clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under Topic 606 when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all the guidance in Topic 606 should be applied, including recognition, measurement, presentation, and disclosure requirements. The standard adds unit-of-account guidance in Topic 808 to align with the guidance in Topic 606 (that is, a distinct good or service) when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of Topic 606, and requires that in a transaction with a collaborative arrangement participant that is not directly related to sales to third parties, presenting the transaction together with revenue recognized under Topic 606 is precluded if the collaborative arrangement participant is not a customer. The standard is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted, including adoption in any interim period for public business entities for periods in which financial statements have not been issued. Amendments in the standard should be applied retrospectively to the date of initial application of Topic 606, but entities may elect to apply the amendments in this Update retrospectively either to all contracts or only to contracts that are not completed at the date of initial application of Topic 606, and should disclose the election. An entity may also elect to apply the practical expedient for contract modifications that is permitted for entities using the modified retrospective transition method in Topic 606. The Company is in the process of evaluating the impact of ASU 2018-18 on its consolidated financial statements and disclosures.

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”). The amendments in this ASU require certain existing disclosure requirements in Topic 820 to be modified or removed, and certain new disclosure requirements to be added to the Topic. In addition, this ASU allows entities to exercise more discretion when considering fair value measurement disclosures. ASU 2018-13 is effective after December 15, 2019 with early adoption permitted. The Company is in the process of evaluating the impact of ASU 2018-13 on its consolidated financial statements and disclosures.

In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting (“ASU 2018-07”). ASU 2018-07 expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. ASU 2018-07 also clarifies that Topic 718 does not apply to share-based payments used to effectively provide (1) financing to the issuer or (2) awards granted in conjunction with selling goods or services to customers as part of a contract accounted for under Revenue from Contracts with Customers (Topic 606). The guidance is effective for fiscal years beginning after December 15, 2018, including interim periods within that fiscal year. Early adoption is permitted. The Company is currently assessing the effect that ASU 2018-07 will have on its consolidated financial statements and disclosures.

In July 2017, the FASB issued ASU No. 2017‑11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815) I. Accounting for Certain Financial Instruments with Down Round Features II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception (“ASU 2017‑11”). Part I applies to entities that issue financial instruments such as warrants, convertible debt or convertible preferred stock that contain down‑round features. Part II replaces the indefinite deferral for certain mandatorily redeemable noncontrolling interests and mandatorily redeemable financial instruments of nonpublic entities contained within Accounting Standards Codification (“ASC”) Topic 480 with a scope exception and does not impact the accounting for these mandatorily redeemable instruments. ASU 2017‑11 is required to be adopted for annual periods beginning after December 15, 2018, including interim periods within those fiscal years. The adoption of ASU 2017‑11 is not expected to have a material impact on the Company’s consolidated financial statements.

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which supersedes FASB Topic 840, Leases (Topic 840) and provides principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. The new standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease, respectively. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of classification. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. In January 2018, the FASB issued ASU No. 2018-01, Leases (Topic 842): Land Easement Practical Expedient for Transition to Topic 842, which amends ASU 2016-02 to provide entities an optional transition practical expedient to not evaluate under Topic 842 existing or expired land easements that were not previously accounted for as leases under the current leases guidance in Topic 842. An entity that elects this practical expedient should evaluate new or modified land easements under Topic 842 beginning at the date that the entity adopts Topic 842. In July 2018, the FASB also issued ASU No. 2018-11, Leases (Topic 842): Targeted Improvements, which provides an optional transition method that allows entities to elect to apply the standard prospectively at its effective date, versus recasting the prior periods presented. The standard will be effective for annual and interim periods beginning after December 15, 2018, with early adoption permitted upon issuance. The Company expects to elect the option to not restate comparative periods presented in the financial statements, using a cumulative-effect adjustment on the effective date of the standard, with comparative periods presented in accordance with the existing guidance in ASC 840. The Company will adopt the new standard effective April 1, 2019 and will use the effective date as the date of initial application.

The Company currently expects to elect the available package of practical expedients which allows the Company to not reassess previous accounting conclusions around whether arrangements are or contain leases, the classification of leases, and the treatment of initial direct costs. The Company also expects it will make an accounting policy election to utilize the short-term lease exemption, whereby leases with a term of twelve months or less will not follow the recognition and measurement requirements of the new standard.

The Company is currently evaluating the impact of pending adoption on its consolidated financial statements and disclosures, including the impact on the Company’s build-to-suit lease for which the accounting may change under Topic 842.

Fair value of financial assets and liabilities

12 Months Ended

Mar. 31, 2019

Fair value of financial assets and liabilities

Fair value of financial assets and liabilities

3. Fair value of financial assets and liabilities

The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis:


	Fair Value Measurements
	as of March 31, 2019 Using:
	Level 1		Level 2		Level 3		Total
Assets
Money market funds	$	—	$	2,676	$	—	$	2,676
Commercial paper		—		46,687		—		46,687
US Government Agency bonds		—		20,884		—		20,884
US Treasury bonds		—		41,057		—		41,057
Corporate debt securities		—		8,467		—		8,467
	$	—	$	119,771	$	—	$	119,771


	Fair Value Measurements
	as of March 31, 2018 Using:
	Level 1		Level 2		Level 3		Total
Assets
Money market funds	$	—	$	4,130	$	—	$	4,130
Commercial paper		—		27,998		—		27,998
Corporate debt securities		—		15,970		—		15,970
	$	—	$	48,098	$	—	$	48,098
Liabilities:
Warrant liability	$	—	$	—	$	1,642	$	1,642
	$	—	$	—	$	1,642	$	1,642

During the years ended March 31, 2019 and 2018, there were no transfers between levels.

Valuation of cash equivalents and short‑term investments

Money market funds, commercial paper, US Treasury bonds, US Government Agency bonds and corporate debt securities were valued by the Company using quoted prices in active markets for similar securities, which represent a Level 2 measurement within the fair value hierarchy.

Valuation of Warrant Liability

The warrant liability is related to the warrants to purchase shares of series seed preferred stock (see Note 8). The fair value of the warrant liability was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. Upon the closing of the IPO in July 2018, the warrant to purchase shares of the Company’s series seed convertible preferred stock was converted into a warrant to purchase shares of the Company’s common stock. As a result, the warrant liability was remeasured a final time on the closing date of the IPO and reclassified to stockholders’ equity (deficit).

The Company used the Black‑Scholes option‑pricing model, which incorporated assumptions and estimates, to value the warrant liability. Key estimates and assumptions impacting the fair value measurement include (i) the expected term of the warrants, (ii) the risk‑free interest rate, (iii) the expected dividend yield, (iv) expected volatility of the price of the underlying series seed preferred stock and (v) the fair value of the series seed preferred stock on the valuation date. The Company estimated the fair value per share of the underlying series seed preferred stock based, in part, on the results of third‑party valuations and additional factors deemed relevant. The risk‑free interest rate was determined by reference to the U.S. Treasury yield curve for time periods approximately equal to the remaining contractual term of the warrants. The Company estimated a 0% expected dividend yield based on the fact that the Company has never paid or declared dividends and does not intend to do so in the foreseeable future. Prior to July 2018, the Company was a private company and accordingly, lacked company‑specific historical and implied volatility information of its stock, the expected stock volatility was based on the historical volatility of publicly traded peer companies for a term equal to the remaining expected term of the warrants.

As of March 31, 2018, the warrant liability was valued at $1,642 and classified as a non-current liability on the consolidated balance sheet. The following assumptions were used in valuing the warrant liability:


	March 31,
	2018
Risk-free interest rate	2.69	%
Expected term (in years)	7.5
Expected volatility	65.8	%
Expected dividend yield	0	%

Based on the terms and conditions of the warrant, upon closing of the Company’s IPO in July 2018, the warrant to purchase shares of the Company’s series seed convertible preferred stock was converted into a warrant to purchase shares of the Company’s common stock. On that date, the Company remeasured the warrant liability to fair value and reclassified the total carrying value to additional paid-in capital. The Company performed the final remeasurement of the warrant liability using the IPO price of $15.00 per share and recorded the change in fair value as a component of total other income (expense), net in the consolidated statement of operations.

The following assumptions were used to measure the fair market value of the warrant liability upon the conversion date:


Risk-free interest rate	2.81	%
Expected term (in years)	7.2
Expected volatility	64.4	%
Expected dividend yield	0	%

The following table presents a roll forward of the warrant liability:


	Warrant
	Liability
Balance at March 31, 2018	$	1,642
Change in fair value		5,452
Conversion of convertible preferred stock warrant into common stock warrant		(7,094)
Balance at March 31, 2019	$	—

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Short-term investments

12 Months Ended

Mar. 31, 2019

Short-term investments

Short-term investments

4. Short‑term investments

Short‑term investments by investment type consisted of the following:


	March 31, 2019
			Gross		Gross
	Amortized		unrealized		unrealized
	cost		gains		losses		Fair value
Commercial paper	$	46,687	$	2	$	(2)	$	46,687
US Government agency bonds		15,889		4		—		15,893
US Treasury bonds		38,047		13		—		38,060
Corporate debt securities		8,469		—		(2)		8,467
	$	109,092	$	19	$	(4)	$	109,107


	March 31, 2018
			Gross		Gross
	Amortized		unrealized		unrealized
	cost		gains		losses		Fair value
Commercial paper	$	28,028	$	2	$	(32)	$	27,998
Corporate debt securities		16,005		—		(35)		15,970
	$	44,033	$	2	$	(67)	$	43,968

Property, plant and equipment, net

12 Months Ended

Mar. 31, 2019

Property, plant and equipment, net

Property, plant and equipment, net

5. Property, plant and equipment, net

Property, plant and equipment, net consisted of the following:


	March 31,
	2019		2018
Leasehold improvements	$	154	$	154
Construction in progress		124		—
Build-to-suit lease asset		11,514		—
Office equipment		49		49
Computer equipment		138		87
Plant and laboratory equipment		584		336
	$	12,563	$	626
Less: Accumulated depreciation and amortization		(404)		(256)
	$	12,159	$	370

Depreciation and amortization expense was $148, $109 and $122 for the years ended March 31, 2019, 2018 and 2017, respectively, and recorded within research and development and general and administrative expenses in the consolidated statement of operations.

Build-to-suit lease asset, as of March 31, 2019, includes $11,514 capitalized in connection with the Company’s build-to-suit lease accounting (see Note 13).

Accrued expenses and other current liabilities

12 Months Ended

Mar. 31, 2019

Accrued expenses and other current liabilities

Accrued expenses and other current liabilities

6. Accrued expenses and other current liabilities

Accrued expenses and other current liabilities consisted of the following:


	March 31,
	2019		2018
Accrued research and development costs	$	530	$	949
Accrued compensation and benefits costs		1,510		949
Accrued professional fees		464		1,094
Deferred rent		24		26
Other		273		153
	$	2,801	$	3,171

Convertible preferred stock

12 Months Ended

Mar. 31, 2019

Convertible preferred stock

Convertible preferred stock

7. Convertible preferred stock

The Company previously issued series seed convertible preferred stock (the “series seed preferred stock”), series A convertible preferred stock (the “series A preferred stock”) and series B convertible preferred stock (the “series B preferred stock”). The series seed preferred stock, series A preferred stock and series B preferred stock are collectively referred to as the “preferred stock.” In connection with the closing of the IPO, the preferred stock converted into 19,157,360 shares of common stock on a 1:9.94688 basis. There was no preferred stock outstanding as of March 31, 2019.

As of March 31, 2018, preferred stock consisted of the following (in thousands, except share amounts):


	March 31, 2018
		Preferred
	Preferred	Shares					Common Stock
	Shares	Issued and	Carrying		Liquidation		Issuable Upon
	Authorized	Outstanding	Value		Preference		Conversion
Series seed preferred stock	250,000	200,000	$	1,609	$	2,000	1,989,376
Series A preferred stock	864,553	864,553		30,000		30,000	8,599,601
Series B preferred stock	861,415	861,415		54,752		54,950	8,568,383
	1,975,968	1,925,968	$	86,361	$	86,950	19,157,360

Prior to the closing of the IPO, the holders of the preferred stock had the following rights and preferences:

The holders of the Preferred Stock have the following rights and preferences:

Voting

The holders of the preferred stock were entitled to vote, together with the holders of common stock, on all matters submitted to the stockholders for a vote and were entitled to the number of votes equal to the number of whole shares of common stock into which such holders of preferred stock could convert on the record date of for determination of stockholders entitled to vote. The holders of preferred stock and common stock, voting as a single class, were entitled to elect two directors of the Company. Additionally, the holders of the series seed preferred stock were entitled to elect two directors of the Company, the holders of the series A preferred stock were entitled to elect one director of the Company and the holders of at least 55% of the outstanding series B preferred stock were entitled to elect two directors of the Company.

Conversion

Each share of preferred stock was convertible into common stock, at any time, at the option of the holder, and without the payment of additional consideration, at the applicable conversion ratio then in effect for each series of preferred stock and subject to adjustment in accordance with anti‑dilution provisions. In addition, each share of preferred stock was convertible into common stock at the applicable conversion ratio then in effect for each series of preferred stock upon the earlier of (i) the closing of a firm commitment underwritten public offering of the Company’s common stock with gross proceeds to the Company of at least $30,000 and at a price per share of not less than $9.62, subject to appropriate adjustment in the event of any stock split, stock dividend, combination or other similar recapitalization, or (ii) a date specified by vote or written consent of the holders of 75% of the outstanding preferred stock (voting together as a single class on an as‑converted basis). For any events of deemed liquidation (as defined below) in which series B preferred stock investors would receive less than their full liquidation preference, a further approval of holders of 55% of the outstanding series B preferred stock was required. As of March 31, 2018, each share of preferred stock was convertible into 9.94688 share of common stock.

The conversion ratio for each series of preferred stock was determined by dividing the original issue price of each series of preferred stock by the conversion price of each series (as defined below). As of March 31, 2018, the series seed preferred stock original issue price and series seed preferred stock conversion price were $1.01 per share and $10.00 per share, respectively. As of March 31, 2018, the series A preferred stock original issue price and series A preferred stock conversion price were $3.49 per share and $34.70 per share, respectively. As of March 31, 2018, the series B preferred stock original issue price and series B preferred stock conversion price were $6.41 per share and $63.79 per share, respectively. Such series seed preferred stock original issue price, series A preferred stock original issue price and series B preferred stock original issue price and series seed preferred stock conversion price, series A preferred stock conversion price and series B preferred stock conversion price, and the rate at which each series of preferred stock may be converted into common stock, were subject to appropriate adjustment from time to time in the event of any stock dividend, stock split, combination or other similar recapitalization with respect to the preferred stock. The series seed preferred stock conversion price, series A preferred stock conversion price and series B preferred stock conversion price were also subject to adjustments based on weighted‑average anti‑dilution provisions set forth in the Company’s certificate of incorporation, as amended and restated, in the event that additional securities were issued at a purchase price less than the series seed preferred stock conversion price, series A preferred stock conversion price or series B preferred stock conversion price then in effect.

Dividends

The holders of the preferred stock were entitled to be paid noncumulative dividends if and when declared by the Company’s board of directors. The Company could not pay any dividends on shares of common stock of the Company unless the holders of preferred stock then outstanding simultaneously receive dividends at the same rate and same time as dividends paid with respect to common stock. Dividends were to accrue on a daily basis assuming a 365‑day year, and were to be paid in cash. Through the date of the IPO, when preferred shares converted to common shares, no dividends had been declared or paid.

Liquidation preference

In the event of any voluntary or involuntary liquidation event, dissolution, winding up of the Company or an event of deemed liquidation, each holder of the then outstanding series B preferred stock would have been entitled to receive, prior and in preference to any distributions to the holders of series A preferred stock, series seed preferred stock and common stock, an amount equal to the greater of (i) the applicable original issue price, plus any declared but unpaid dividends thereon, or (ii) the amount such holder would have received if such holder had converted its shares into common stock immediately prior to such liquidation event.

After the payment of all preferential amounts to the holders of series B preferred stock, each holder of the then outstanding series A preferred stock would have been entitled to receive, prior and in preference to any distributions to the holders of series seed preferred stock and common stock, an amount equal to the greater of (i) the applicable original issue price, plus any declared but unpaid dividends thereon, or (ii) the amount such holder would have received if such holder had converted its shares into common stock immediately prior to such liquidation event.

After the payment of all preferential amounts to the holders of series A preferred stock, each holder of the then outstanding series seed preferred stock would have been entitled to receive, prior and in preference to any distributions to the holders of common stock, an amount equal to the greater of (i) the applicable original issue price, plus any declared but unpaid dividends thereon or (ii) the amount such holder would have received if such holder had converted its shares into common stock immediately prior to such liquidation event.

After payments have been made in full to the holders of preferred stock, then, to the extent available, the remaining amounts would have been distributed among the holders of the shares of common stock, the holders of series B preferred stock and the holders of series A preferred stock, pro rata based on the number of shares held by each holder, assuming full conversion of all such preferred stock.

The holders of series B preferred stock and series A preferred stock were subject to a participation cap (as defined below) for remaining amounts that would have been distributed, which was $127.58 per share for the series B preferred stock and $69.40 per share for the series A preferred stock.

To the extent available, the remaining amounts greater than the total of the participation caps would have been distributed among the holders of the shares of common stock, pro rata based on the number of shares held by each holder.

Unless a majority of the holders of the then outstanding preferred stock, on an as‑if‑converted basis voting together as a single class, elect otherwise, an event of deemed liquidation shall include a merger or consolidation (other than one in which stockholders of the Company own a majority by voting power of the outstanding shares of the surviving or acquiring corporation), sale, transfer or exclusive license of substantially all of the assets of the Company. The preferred stock was conditionally redeemable upon an event of deemed liquidation, which was defined as any (i) merger, consolidation or acquisition, involving the Company or its Subsidiary Undertaking, in which the Company or its subsidiary undertaking was not the surviving entity, (ii) an asset sale, (iii) a share sale, (iv) an initial public offering, (v) the occurrence of a change of control in respect of the Company, (vi) a winding up (vii) or any other a return of capital to stockholders (other than a conversion, redemption or repurchase of shares made in accordance with the applicable governing documents).

Redemption

The Company’s certificate of incorporation, as amended and restated, did not provide redemption rights to the holders of preferred stock.

The holders of shares of convertible preferred stock had liquidation rights in the event of a deemed liquidation that, in certain situations, were not solely within the control of the Company. Therefore, convertible preferred stock was classified outside of stockholders’ equity (deficit).

Upon issuance of each class of preferred stock, the Company assessed the embedded conversion and liquidation features of the securities. The Company determined that each class of preferred stock did not require the Company to separately account for the liquidation features. The Company also concluded that no beneficial conversion feature existed upon the issuance date of the series A preferred stock or series B preferred stock as of March 31, 2018. However, the Company did conclude that a beneficial conversion feature existed upon the issuance date of the series seed preferred stock. As the series seed preferred stock was convertible into common stock, at any time, at the option of the holder, and without the payment of additional consideration, at the applicable conversion ratio then in effect, the Company recognized the accretion of the beneficial conversion feature as a deemed dividend immediately upon the issuance of the series seed preferred stock.

Preferred stock warrants	12 Months Ended
Preferred stock warrants	Mar. 31, 2019
Preferred stock warrants
Preferred stock warrants	8. Preferred stock warrants In connection with the issuance of the series seed preferred stock, the Company issued to the holders of the series seed preferred stock warrants for the purchase of 50,000 shares of series seed preferred stock, which became fully vested and exercisable in the year of issuance. The warrants to purchase shares of series seed preferred stock were issued at an exercise price of $10.00 per share and expire on the earlier of September 16, 2025 or a qualified change of control event. The issuance date fair value of the warrants to purchase shares of series seed preferred stock was $391 and was recorded as a liability with a corresponding reduction in the carrying value of the series seed preferred stock. As of March 31, 2019 and 2018, the fair value of the warrant liability was $0 and $1,642, respectively. The Company recognized a loss of $5,452, $972 and $150 within total other income (expense), net in the consolidated statements of operations for the years ended March 31, 2019, 2018 and 2017, respectively, related to the change in fair value of the warrant liability. Upon the closing of the Company’s IPO in July 2018, all outstanding preferred stock was converted into common stock and the series seed preferred stock warrants became exercisable for common stock instead of series seed preferred stock. As a result, the warrant liability was remeasured a final time on the closing date of the IPO and reclassified to stockholders’ equity (deficit).

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Mar. 31, 2019
Stockholders' Equity
Stockholders' Equity	9. Stockholders’ Equity Common Stock As of March 31, 2019, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue up to 150,000,000 shares of common stock, par value $0.001 per share. As of March 31, 2018, the Company was authorized to issue 27,314,288 shares of par value $0.001 per share common stock (including 26,258 authorized shares of common A stock). In July 2017, the Company issued and sold 26,258 shares of par value $0.001 per share common A stock for nominal cash proceeds. In July 2018, the Company repurchased 26,258 shares of par value $0.001 per share common A stock for nominal cash proceeds. The voting, dividend and liquidation rights of the holders of the Company’s common stock is subject to and qualified by the rights, powers and preferences of the holders of the preferred stock as set forth above. As of March 31, 2019, the Company had reserved 6,873,744 shares of common stock for the exercise of outstanding stock options, the number of shares remaining available for grant under the Company’s 2018 Omnibus Incentive Compensation Plan and the Company’s Employee Stock Purchase Plan (see Note 10) and the exercise of the outstanding warrants to purchase shares of common. As of March 31, 2018, the Company had reserved 22,306,801 shares of common stock for the conversion of outstanding shares of preferred stock (see Note 7), the exercise of outstanding stock options, the number of shares remaining available for grant under the Company’s 2017 Equity Compensation Plan (see Note 10) and the exercise of the outstanding warrants to purchase shares of series seed preferred stock (see Note 8), assuming all warrants to purchase shares of series seed preferred stock became warrants to purchase shares of common stock at the applicable conversion ratio. Voting Each share of common stock, including common A stock, entitles the holder to one vote, together with the holders of preferred stock, on all matters submitted to the stockholders for a vote. The holders of common stock, together with the holders of preferred stock and voting as a single class, are entitled to elect two directors of the Company by vote of a majority of such shares. Dividends Common stockholders are entitled to receive dividends, as may be declared by the Company’s board of directors, if any, subject to the preferential dividend rights of the preferred stock. Through March 31, 2019, no cash dividends have been declared or paid. Each share of common A stock is entitled to receive dividends, as may be declared by the Company’s board of directors, if any, equal to a maximum of 100% of each share’s par value. Upon an event of deemed liquidation, common A stock is entitled to receive dividends equal to a maximum of 300% of each share’s par value. Undesignated Preferred Stock As of March 31, 2019, the Company’s certificate of incorporation, as amended and restated, authorized the Company to issue up to 10,000,000 shares of undesignated preferred stock, par value $0.001 per share. There were no undesignated preferred shares issued or outstanding as of March 31, 2019.

Stock-Based Compensation

12 Months Ended

Mar. 31, 2019

Stock-Based Compensation

Stock-Based Compensation

10. Stock‑Based Compensation

2015 Enterprise Management Incentive Share Option Plan

The 2015 Enterprise Management Incentive Share Option Plan of Replimune UK (the “2015 Plan”) provided for Replimune UK to grant incentive stock options, non‑statutory stock options, stock awards, stock units, stock appreciation rights and other stock‑based awards. Incentive stock options are granted only to the Company’s employees, including officers and directors who are also employees. Non‑statutory stock options are granted to employees, members of the board of directors, outside advisors and consultants of the Company.

2017 Equity Compensation Plan

In July 2017, in conjunction with the Reorganization, the 2015 Plan was terminated, and all awards were cancelled with replacement awards issued under the 2017 Equity Compensation Plan (the “2017 Plan”). Subsequent to the Reorganization, no additional grants will be made under the 2015 Plan and any outstanding awards under the 2015 Plan will continue with their original terms. The Company concluded that the cancellation of the 2015 Plan and issuance of replacement awards under the 2017 Plan was a modification with no change in the material rights and preferences and therefore no recorded change in the fair value of each respective award.

The Company’s 2017 Plan provides for the Company to grant incentive stock options or non‑statutory stock options, stock awards, stock units, stock appreciation rights and other stock‑based awards. Incentive stock options may be granted only to the Company’s employees, including officers and directors who are also employees. Restricted stock awards and non‑statutory stock options may be granted to employees, officers, members of the board of directors, advisors and consultants of the Company. The maximum number of common shares that may be issued under the 2017 Plan was 2,659,885 as of March 31, 2019, of which 0 remained available for future grants as of March 31, 2019. Shares with respect to which awards have expired, terminated, surrendered or cancelled under the 2017 Plan without having been fully exercised will be available for future awards under the 2017 Plan. In addition, shares of common stock that are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for the grant of awards.

2018 Omnibus Incentive Compensation Plan

On July 9, 2018, the Company’s board of directors adopted, and the Company’s stockholders approved the 2018 Omnibus Incentive Compensation Plan (the “2018 Plan”), which became effective immediately prior to the effectiveness of the registration statement for the Company’s initial public offering. The 2018 Plan provides for the issuance of incentive stock options, non‑qualified stock options, stock awards, stock units, stock appreciation rights and other stock‑based awards. The number of shares initially reserved for issuance under the 2018 Plan is 3,617,968 shares. If any options or stock appreciation rights, including outstanding options and stock appreciation rights granted under the 2017 Plan (up to 2,520,247 shares), terminate, expire, or are canceled, forfeited, exchanged, or surrendered without having been exercised, or if any stock awards, stock units or other stock‑based awards, including outstanding awards granted under the 2017 Plan, are forfeited, terminated, or otherwise not paid in full in shares of common stock, the shares of the Company’s common stock subject to such grants will be available for purposes of our 2018 Plan. As of March 31, 2019, 2,306,004 shares remained available for future grants under the 2018 Plan.

The 2015 Plan, the 2017 Plan and the 2018 Plan was administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. However, the board of directors shall administer and approve all grants made to non‑employee directors. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, except that the exercise price per share of incentive stock options may not be less than 100% of the fair market value of the common stock on the date of grant (or 110% of fair value in the case of an award granted to employees who hold more than 10% of the total combined voting power of all classes of stock at the time of grant) and the term of stock options may not be greater than five years for an incentive stock option granted to a 10% stockholder and greater than ten years for all other options granted. Stock options awarded under both plans expire ten years after the grant date, unless the board of directors sets a shorter term. Vesting periods for both plans are determined at the discretion of the board of directors. Incentive stock options granted to employees and non‑statutory options granted to employees, officers, members of the board of directors, advisors, and consultants of the Company typically vest over four years.

Employee Stock Purchase Plan

On July 9, 2018, the Company’s board of directors adopted and the Company’s stockholders approved the Employee Stock Purchase Plan (the “ESPP”), which became effective immediately prior to the effectiveness of the registration statement for the Company’s initial public offering. The total shares of common stock initially reserved for issuance under the ESPP is limited to 348,612 shares. In addition, as of the first trading day of each fiscal year during the term of the ESPP (excluding any extensions), an additional number of shares of the Company’s common stock equal to 1% of the total number of shares outstanding on the last trading day in the immediately preceding fiscal year or 697,224 shares, whichever is less (or such lesser amount as determined by the Company’s board of directors) will be added to the number of shares authorized under the ESPP. If the total number of shares of common stock to be purchased pursuant to outstanding purchase rights on any particular date exceed the number of shares then available for issuance under the ESPP, then the plan administrator will allocate the available shares pro‑rata and refund any excess payroll deductions or other contributions to participants.

The following table presents, on a weighted‑average basis, the assumptions that the Company used to determine the grant‑date fair value of stock options granted to employees and directors:


	Year Ended
	March 31,
	2019		2018		2017
Risk-free interest rate	2.81	%	2.01	%	1.67	%
Expected term (in years)	6.1		6.0		6.0
Expected volatility	62.0	%	75.0	%	75.0	%
Expected dividend yield	0	%	0	%	0	%

The following table presents the assumptions that the Company used to determine the grant‑date fair value of stock options granted to a non‑employee:


	Year Ended
	March 31, 2018
Risk-free interest rate	2.29	%
Expected term (in years)	10.0
Expected volatility	75.0	%
Expected dividend yield	0	%

All outstanding non-employee options granted during the year ended March 31, 2018 have vested, and there were no options granted to non-employees during the year ended March 31, 2019 or 2017.

Stock option valuation

The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. The Company lacks company-specific historical and implied volatility information. Therefore, it estimated its expected stock volatility based on the historical volatility of a publicly traded set of peer companies. For options with service-based vesting conditions, the expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The expected term of stock options granted to non-employees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

Stock options

The following table summarizes the Company’s stock option activity:


		Weighted		Weighted Average
	Number of	Average		Contractual Term	Aggregate
	Shares	Exercise Price		(Years)	Intrinsic Value
Outstanding as of March 31, 2018	2,520,247	$	2.72	8.91	$	2,808
Granted	1,371,500		14.92	9.78
Exercised	(110,427)		1.87
Cancelled	(59,536)		8.65
Outstanding as of March 31, 2019	3,721,784	$	7.14	8.61	$	30,150
Options exercisable as of March 31, 2018	592,349	$	1.84	8.22	$	1,184
Options exercisable as of March 31, 2019	1,278,330	$	2.51	7.75	$	16,249

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock.

The weighted average grant‑date fair value per share of stock options granted during the years ended March 31, 2019 and 2018 was $8.82 and $1.92, respectively.

The total fair value of options vested during the years ended March 31, 2019 and 2018 was $1,298 and $398, respectively.

As of March 31, 2019, there were no outstanding unvested service‑based stock options held by non‑employees.

Stock‑Based Compensation Expense

Stock‑based compensation expense was classified in the consolidated statements of operations as follows:


	Year Ended
	March 31,
	2019		2018		2017
Research and development	$	1,488	$	335	$	65
General and administrative		1,242		477		143
	$	2,730	$	812	$	208

As of March 31, 2019, total unrecognized compensation cost related to the unvested stock‑based awards was $11,807, which is expected to be recognized over a weighted average period of 2.36 years.

Net loss per share

12 Months Ended

Mar. 31, 2019

Net loss per share

Net loss per share

11. Net loss per share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Year Ended March 31,
	2019		2018		2017
Numerator:
Net loss attributable to common stockholders	$	(30,834)	$	(19,702)	$	(7,704)
Denominator:
Weighted average common shares outstanding, basic and diluted		23,198,400		4,978,539		4,973,439
Net loss per share attributable to common stockholders, basic and diluted	$	(1.33)	$	(3.96)	$	(1.55)

The Company’s potentially dilutive securities, which include stock options, preferred stock and warrants to purchase shares of series seed preferred stock, have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Common A stock has been excluded from the computation of diluted net loss per share because the shares have nominal economic participation rights. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders 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 stockholders for the periods indicated because including them would have had an anti‑dilutive effect:


	Year Ended March 31,
	2019	2018	2017
Options to purchase common stock	3,721,784	2,520,247	930,027
Convertible preferred stock (as converted to common stock)	—	19,157,360	10,588,977
Warrants to purchase convertible preferred stock (as converted to common stock)	497,344	497,344	497,344
	4,219,128	22,174,951	12,016,348

Significant agreements	12 Months Ended
Significant agreements	Mar. 31, 2019
Significant agreements
Significant agreements	12. Significant agreements Agreement with Bristol-Myers Squibb Company In February 2018, the Company entered into an agreement with Bristol-Myers Squibb Company (“BMS”). Pursuant to the agreement, BMS will provide to the Company, at no cost, a compound for use in the Company’s ongoing clinical trial. Under the agreement, the Company will sponsor, fund and conduct the clinical trial in accordance with an agreed-upon protocol. BMS granted the Company a non-exclusive, non-transferrable, royalty-free license (with a right to sublicense) under its intellectual property to its compound in the clinical trial and agreed to supply its compound, at its cost and for no charge to the Company, for use in the clinical trial. Unless earlier terminated, the agreement will remain in effect until (i) the completion of the clinical trial, (ii) all related clinical trial data have been delivered to both parties and (iii) the completion of any statistical analyses and bioanalyses contemplated by the clinical trial protocol or any analysis otherwise agreed upon by the parties. The agreement may be terminated by either party (i) in the event of an uncured material breach by the other party, (ii) in the event the other party is insolvent or in bankruptcy proceedings or (iii) for safety reasons. Upon termination, the licenses granted to the Company to use BMS’s compound in the clinical trial will terminate. As of March 31, 2019, the Company had not incurred any costs and does not expect to incur future costs in connection with this agreement. Agreement with Regeneron Pharmaceuticals, Inc. In May 2018, the Company entered into an agreement with Regeneron Pharmaceuticals, Inc. (“Regeneron”). The Company and Regeneron are each independently developing compounds for the treatment of certain tumor types. Pursuant to the agreement, the Company and Regeneron will undertake one or more clinical trials using a combination of the compounds being developed by each entity. Under the agreement, each study will be conducted under terms set out in a separately agreed upon study plan that will identify the name of the sponsor and which party will manage the particular clinical trial, and include the protocol, the budget and a schedule of clinical obligations. In June 2018, under the terms of the agreement between the Company and Regeneron, the parties agreed to the first study plan. The Company and Regeneron have agreed to the protocol, budget, sample testing and clinical obligations schedule under the study plan. Development and supply costs associated with the study plan will be split equally between the Company and Regeneron. Pursuant to the terms of the agreement, each party granted the other party a non‑exclusive license under its respective intellectual property and agreed to contribute the necessary resources needed to fulfill its respective obligations, in each case, under the terms of the agreed-upon or to‑be agreed upon study plans. Development costs of a particular clinical trial will be split equally between the Company and Regeneron. The agreement may be terminated by either party if (i) there is no active study plan for which a final study report has not been completed, (ii) the parties have not entered into a study plan for an additional clinical trial within a period of time after the delivery of the most recent final study report or (iii) in the event of a material breach. The Company will account for costs incurred as part of the study, including costs to supply compounds for use in the study, as research and development expenses within the consolidated statement of operations. The Company will recognize any amounts received from Regeneron in connection with this agreement as an offset to research and development expense within the consolidated statement of operations. Under the terms of the agreement, on a quarterly basis the Company and Regeneron true-up costs of the study and make corresponding payments to the party that incurred the majority of the costs. During the year ended March 31, 2019, the Company did not receive or make any payments under the terms of the agreement to Regeneron. As of March 31, 2019, the Company recorded $337 of receivables from Regeneron in connection with this agreement in prepaid expenses and other current assets in the consolidated balance sheet.

Commitments and contingencies

12 Months Ended

Mar. 31, 2019

Commitments and contingencies

Commitments and contingencies

13. Commitments and contingencies

Lease agreements

In December 2015, the Company entered into a lease agreement for office space in Woburn, Massachusetts, which expires on March 30, 2021. The Company has the option to extend the lease agreement for successive periods of five years. Monthly lease payments, inclusive of base rent and ancillary charges, total $7. Monthly base rent is subject to increase each year in proportion to the Consumer Price Index.

In April 2016, the Company entered into a lease agreement for office and laboratory space in Abingdon, England, which expires on April 3, 2026. The Company has the right to terminate the lease as of April 4, 2021 upon at least nine months’ prior written notice. Monthly lease payments are inclusive of base rent, ancillary charges, non‑rent shared tenant occupancy costs and the respective value added tax to be paid. Monthly lease payments include base rent of approximately $23 through December 3, 2016 and $31 thereafter. Monthly base rent is subject to increase after April 2021 in proportion to the Retail Price Index.

Build-to-suit lease

In June 2018, the Company entered into an agreement to lease approximately 63,000 square feet of office, manufacturing and laboratory space within a previously occupied building with approximately 106,000 square feet of rentable space in Framingham, Massachusetts. Pursuant to the lease agreement, the lease term commenced in November 2018, subject to the landlord completing certain agreed upon landlord improvements. The rent commencement date is estimated to be August 2019. The initial lease term is ten years from the rent commencement date and includes two optional five year extensions. Annual lease payments during the first year are $2,373 with increases of 3.0% each year.

The Company is not the legal owner of the leased space. However, in accordance with ASC 840, Leases, the Company is deemed to be the owner of the leased space during the construction period because of certain indemnification provisions within the lease agreement. As a result, as of March 31, 2019, the Company capitalized $4,993 (equal to the estimated fair value of its leased portion of the premises) as build-to-suit lease asset within property and equipment. The Company has engaged a third party to develop the leased space to the Company’s specifications as office, manufacturing and laboratory space. The Company has capitalized costs of construction of $6,521 to build-to-suit lease asset within property, plant and equipment on its consolidated balance sheet. Of the $6,521 of capitalized costs, $1,474 had been paid, $5,047 remained payable and $2,174 was reimbursable by the landlord as of March 31, 2019. The construction is expected to be completed in September 2019, at which time the Company will assess and determine if the assets and corresponding liability should be de-recognized.

The Company recorded the following for the lease agreement for its new office, manufacturing and laboratory space during the construction period:


	Year Ended
	March 31, 2019
Rent expense	$	556
Amounts capitalized as build-to-suit lease	$	11,514

The Company recorded total rent expense of $556, $430 and $282 during the years ended March 31, 2019, 2018 and 2017, respectively, and recorded within research and development and general and administrative expenses in the consolidated statement of operations. Rent expense for the year ended March 31, 2019 included $93 of ground rent associated with the build-to-suit lease.

The following table summarizes the future minimum lease payments due under the Company’s operating leases as of March 31, 2019:


2020	$	2,062
2021		2,901
2022		2,493
2023		2,568
2024		2,645
2025		2,725
Thereafter		12,770
	$	28,164

Manufacturing commitments

The Company has entered into an agreement with a contract manufacturing organization to provide clinical trial products. As of March 31, 2019, the Company had committed to minimum payments under these arrangements totaling $4,694 through March 31, 2020. As of March 31, 2018, the Company had committed to minimum payments under these arrangements totaling $2,938 through March 31, 2019.

Indemnification agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company is not aware of any claims under indemnification arrangements, and therefore it has not accrued any liabilities related to such obligations in its consolidated financial statements as of March 31, 2019 or 2018.

Legal Proceedings

The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities.

Income taxes

12 Months Ended

Mar. 31, 2019

Income taxes

Income taxes

15. Income Taxes

U.S. Tax Reform

On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the “Tax Reform Act”), which significantly reforms the Internal Revenue Code of 1986, as amended (the “Code”). The Tax Reform Act, among other things, contains significant changes to corporate taxation, including reduction of the corporate tax rate from the existing top marginal rate of 35% to a flat rate of 21%, effective as of January 1, 2018; limitation of the deduction for net operating losses to 80% of annual taxable income and elimination of net operating loss carrybacks, in each case, for losses arising in taxable years beginning after December 31, 2017 (though any such tax losses may be carried forward indefinitely); and modifying or repealing many business deductions and credits.

The staff of the Securities and Exchange Commission issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Reform Act. In connection with the initial analysis of the impact of the Tax Reform Act, the Company remeasured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21%. The remeasurement of the Company’s deferred tax assets and liabilities was offset by a corresponding change in the Company’s valuation allowance.

We completed our final determination of the remeasurement of our deferred tax assets and liabilities for the year ended March 31, 2019 under SEC Staff Accounting Bulletin No. 118 and we have not recorded any adjustments to the provisional amounts recorded at March 31, 2018.

Income taxes

During the years ended March 31, 2019, 2018 and 2017, the Company recorded no income tax benefits for the net operating losses incurred and capitalized start‑up costs generated during the years then ended, due to its uncertainty of realizing a benefit from those items. The Company’s net loss before income taxes were generated in the United States and the United Kingdom.

Net loss before income taxes for the years ended March 31, 2019, 2018 and 2017 were as follows:


	Year Ended March 31,
	2019		2018		2017
United States	$	(9,483)	$	(8,992)	$	(3,450)
Foreign (United Kingdom)		(21,351)		(10,710)		(4,254)
	$	(30,834)	$	(19,702)	$	(7,704)

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate for the years ended March 31, 2019, 2018 and 2017 is as follows:


	March 31,
	2019		2018		2017
U.S. Federal statutory income tax rate	(21.00)	%	(21.00)	%	(34.00)	%
State taxes, net of federal benefit	(1.5)		(2.6)		(2.4)
Research and development expenses	3.1		3.8		7.1
Remeasurement of deferred taxes as a result of tax reform	—		2.6		—
Foreign tax rate differential	2.4		2.2		8.8
Change in valuation allowance	15.5		14.0		19.2
Other	1.5		1.0		1.3
Effective income tax rate	0.00	%	0.00	%	0.00	%

Components of the Company’s deferred tax assets as of March 31, 2019 and 2018 were as follows:


	March 31,
	2019		2018
Deferred tax assets:
Foreign net operating loss carryforwards	$	4,079	$	1,405
Federal net operating loss carryforwards		2,223		—
State net operating loss carryforwards		684		15
Capitalized start-up costs		1,886		3,340
Stock compensation		573		—
Accrued expenses		1,793		—
Other		—		1
Total deferred tax assets		11,238		4,761
Deferred tax liabilities:
Property, plant and equipment		(1,842)		(37)
Total deferred tax liabilities		(1,842)		(37)
Valuation allowance		(9,396)		(4,724)
Net deferred tax assets	$	—	$	—

As of March 31, 2019, the Company had federal and foreign net operating loss carryforwards of approximately $10,587 and $23,993 respectively, which can be carried forward indefinitely. As of March 31, 2019, the Company had state net operating loss carryforwards of $10,822 which will expire between 2038 and 2039.

Utilization of the U.S. federal and state net operating loss carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986, as amended, and corresponding provisions of state law, due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of net operating loss carryforwards that can be utilized annually to offset future taxable income and tax liabilities, respectively. The Company has not completed a study to assess whether a change of ownership has occurred, or whether there have been multiple ownership changes since its formation, due to the significant cost and complexity associated with such a study. Any limitation may result in expiration of a portion of the net operating loss carryforwards before utilization. Further, until a study is completed by the Company and any limitation is known, no amounts are being presented as an uncertain tax position.

Changes in the valuation allowance for deferred tax assets during the years ended March 31, 2019 and 2018 related primarily to the increase in net operating loss carryforwards and capitalized start‑up costs in 2018, and were as follows:


	March 31,
	2019		2018
Valuation allowance as of beginning of year	$	4,724	$	1,887
Increases recorded to income tax provision		4,672		3,347
Remeasurement of deferred taxes as a result of tax reform		—		(510)
Valuation allowance as of end of year	$	9,396	$	4,724

As of March 31, 2019 and 2018, the Company had not recorded any amounts for unrecognized tax benefits. The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision. As of March 31, 2019 and 2018, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts had been recognized in the Company’s consolidated statements of operations and comprehensive loss.

The Company files income tax returns in the United States, Massachusetts and the United Kingdom as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by U.S. federal, state and foreign jurisdictions, where applicable. There are currently no pending tax examinations. The Company is open to future tax examination in the U.S. under statute from 2017 to the present and in the United Kingdom from 2016 to the present.

Geographic Information

12 Months Ended

Mar. 31, 2019

Geographic Information

Geographic Information

16. Geographic Information

The Company operates in two geographic regions: the United States (Massachusetts) and the United Kingdom (Oxfordshire). Information about the Company’s long‑lived assets held in different geographic regions is presented in the tables below:


	March 31,
	2019		2018
United States	$	11,648	$	20
United Kingdom		511		350
	$	12,159	$	370

Quarterly Financial Data (Unaudited)

12 Months Ended

Mar. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited)

17. Quarterly Financial Data (Unaudited)

The following information has been derived from unaudited consolidated financial statements that, in the opinion of management, include all recurring adjustments necessary for a fair statement of such information.


	For the Quarter Ended
	March 31, 2019	December 31, 2018	September 30, 2018	June 30, 2018
Operating expenses	7,825	10,137	7,104	5,879
Net loss	(6,656)	(7,673)	(6,461)	(10,044)
Net loss per share attributable to common
shareholders, basic and diluted	(0.29)	(0.24)	(0.26)	(2.02)


	For the Quarter Ended
	March 31, 2018	December 31, 2017	September 30, 2017	June 30, 2017
Operating expenses	7,065	4,732	4,256	3,176
Net loss	(7,136)	(4,354)	(4,660)	(3,552)
Net loss per share attributable to common
shareholders, basic and diluted	(1.43)	(0.87)	(0.94)	(0.71)

Subsequent Events	12 Months Ended
Subsequent Events	Mar. 31, 2019
Subsequent Events
Subsequent Events	18. Subsequent Events For its consolidated financial statements as of March 31, 2019 and for the year then ended, the Company evaluated subsequent events through the date on which those financial statements were issued. Lease agreement In June 2019, the Company entered into an agreement to lease approximately 18,700 square feet of office space in Woburn, Massachusetts. Pursuant to the lease agreement, the lease term is estimated to commence in July 2019. The rent commencement date is to be one month after the commencement of the lease term. The initial lease term is ten years from the rent commencement date and includes an optional five year extension. Annual lease payments during the first year are $488 with increases of approximately 1.6% each year. Increase in Shares Available for Issuance under the 2018 Plan In April 2019, the Company effected an increase in the total number of shares of the Company’s common stock reserved for issuance under the 2018 Plan from 3,617,968 shares to 4,884,338 shares.

Summary of significant accounting policies (Policies)

12 Months Ended

Mar. 31, 2019

Summary of significant accounting policies

Principles of consolidation

Use of estimates

Foreign currency and currency translation

Concentrations of credit risk and of significant suppliers

Cash and cash equivalents

Restricted Cash

Short-term investments

Short‑term investments

The Company’s short‑term debt security investments as of March 31, 2019 and 2018 had original maturities of less than one year.

Deferred offering costs

Property, plant and equipment


		Estimated Useful life
Office equipment		5 years
Computer equipment		3 years
Plant and laboratory equipment		5 years
Leasehold improvements		Lesser of lease term or 10 years

Impairment of long-lived assets

Impairment of long‑lived assets

Deferred rent

The Company recognizes rent expense on a straight‑line basis over the respective lease terms and has recorded deferred rent for rent expense incurred but not yet paid.

Fair value measurements

Level 1—Quoted prices in active markets for identical assets or liabilities.

Warrant liability

Segment information

Research and development costs

Research contract costs and accruals

Patent costs

Stock-based compensation

Stock‑based compensation

Research and development incentives and receivable

Comprehensive loss

Income taxes

Net income (loss) per share

Recently Adopted Accounting Pronouncements

Recently Issued Accounting Pronouncements

Fair value of financial assets and liabilities (Tables)

12 Months Ended

Mar. 31, 2019

Fair value of financial assets and liabilities

Schedule of company's financial assets and liabilities measured at fair value on a recurring basis


	Fair Value Measurements
	as of March 31, 2019 Using:
	Level 1		Level 2		Level 3		Total
Assets
Money market funds	$	—	$	2,676	$	—	$	2,676
Commercial paper		—		46,687		—		46,687
US Government Agency bonds		—		20,884		—		20,884
US Treasury bonds		—		41,057		—		41,057
Corporate debt securities		—		8,467		—		8,467
	$	—	$	119,771	$	—	$	119,771


	Fair Value Measurements
	as of March 31, 2018 Using:
	Level 1		Level 2		Level 3		Total
Assets
Money market funds	$	—	$	4,130	$	—	$	4,130
Commercial paper		—		27,998		—		27,998
Corporate debt securities		—		15,970		—		15,970
	$	—	$	48,098	$	—	$	48,098
Liabilities:
Warrant liability	$	—	$	—	$	1,642	$	1,642
	$	—	$	—	$	1,642	$	1,642

Schedule of unobservable inputs of the warrant liability


	March 31,
	2018
Risk-free interest rate	2.69	%
Expected term (in years)	7.5
Expected volatility	65.8	%
Expected dividend yield	0	%

Schedule of unobservable inputs of the warrant liability upon the conversion date


Risk-free interest rate	2.81	%
Expected term (in years)	7.2
Expected volatility	64.4	%
Expected dividend yield	0	%

Schedule of roll forward of the warrant liability


	Warrant
	Liability
Balance at March 31, 2018	$	1,642
Change in fair value		5,452
Conversion of convertible preferred stock warrant into common stock warrant		(7,094)
Balance at March 31, 2019	$	—

Short-term investments (Tables)

12 Months Ended

Mar. 31, 2019

Short-term investments

Schedule of short-term investments


	March 31, 2019
			Gross		Gross
	Amortized		unrealized		unrealized
	cost		gains		losses		Fair value
Commercial paper	$	46,687	$	2	$	(2)	$	46,687
US Government agency bonds		15,889		4		—		15,893
US Treasury bonds		38,047		13		—		38,060
Corporate debt securities		8,469		—		(2)		8,467
	$	109,092	$	19	$	(4)	$	109,107


	March 31, 2018
			Gross		Gross
	Amortized		unrealized		unrealized
	cost		gains		losses		Fair value
Commercial paper	$	28,028	$	2	$	(32)	$	27,998
Corporate debt securities		16,005		—		(35)		15,970
	$	44,033	$	2	$	(67)	$	43,968

Property, plant and equipment, net (Tables)

12 Months Ended

Mar. 31, 2019

Property, plant and equipment, net

Schedule of property, plant and equipment, net


	March 31,
	2019		2018
Leasehold improvements	$	154	$	154
Construction in progress		124		—
Build-to-suit lease asset		11,514		—
Office equipment		49		49
Computer equipment		138		87
Plant and laboratory equipment		584		336
	$	12,563	$	626
Less: Accumulated depreciation and amortization		(404)		(256)
	$	12,159	$	370

Accrued expenses and other current liabilities (Tables)

12 Months Ended

Mar. 31, 2019

Accrued expenses and other current liabilities

Schedule of accrued expenses and other current liabilities


	March 31,
	2019		2018
Accrued research and development costs	$	530	$	949
Accrued compensation and benefits costs		1,510		949
Accrued professional fees		464		1,094
Deferred rent		24		26
Other		273		153
	$	2,801	$	3,171

Convertible preferred stock (Tables)

12 Months Ended

Mar. 31, 2019

Convertible preferred stock

Schedule of convertible preferred stock


	March 31, 2018
		Preferred
	Preferred	Shares					Common Stock
	Shares	Issued and	Carrying		Liquidation		Issuable Upon
	Authorized	Outstanding	Value		Preference		Conversion
Series seed preferred stock	250,000	200,000	$	1,609	$	2,000	1,989,376
Series A preferred stock	864,553	864,553		30,000		30,000	8,599,601
Series B preferred stock	861,415	861,415		54,752		54,950	8,568,383
	1,975,968	1,925,968	$	86,361	$	86,950	19,157,360

Stock-Based Compensation (Tables)

12 Months Ended

Mar. 31, 2019

Stock-Based Compensation

Summary of stock option activity


		Weighted		Weighted Average
	Number of	Average		Contractual Term	Aggregate
	Shares	Exercise Price		(Years)	Intrinsic Value
Outstanding as of March 31, 2018	2,520,247	$	2.72	8.91	$	2,808
Granted	1,371,500		14.92	9.78
Exercised	(110,427)		1.87
Cancelled	(59,536)		8.65
Outstanding as of March 31, 2019	3,721,784	$	7.14	8.61	$	30,150
Options exercisable as of March 31, 2018	592,349	$	1.84	8.22	$	1,184
Options exercisable as of March 31, 2019	1,278,330	$	2.51	7.75	$	16,249

Schedule of stock-Based Compensation expense


	Year Ended
	March 31,
	2019		2018		2017
Research and development	$	1,488	$	335	$	65
General and administrative		1,242		477		143
	$	2,730	$	812	$	208

Employees stock options

Stock-Based Compensation

Schedule of assumptions used to determine the grant-date fair value of stock options granted


	Year Ended
	March 31,
	2019		2018		2017
Risk-free interest rate	2.81	%	2.01	%	1.67	%
Expected term (in years)	6.1		6.0		6.0
Expected volatility	62.0	%	75.0	%	75.0	%
Expected dividend yield	0	%	0	%	0	%

Non employee stock options

Stock-Based Compensation

Schedule of assumptions used to determine the grant-date fair value of stock options granted


	Year Ended
	March 31, 2018
Risk-free interest rate	2.29	%
Expected term (in years)	10.0
Expected volatility	75.0	%
Expected dividend yield	0	%

Net loss per share (Tables)

12 Months Ended

Mar. 31, 2019

Net loss per share

Schedule of calculation of basic and diluted net loss per share attributable to common stockholders


	Year Ended March 31,
	2019		2018		2017
Numerator:
Net loss attributable to common stockholders	$	(30,834)	$	(19,702)	$	(7,704)
Denominator:
Weighted average common shares outstanding, basic and diluted		23,198,400		4,978,539		4,973,439
Net loss per share attributable to common stockholders, basic and diluted	$	(1.33)	$	(3.96)	$	(1.55)

Schedule of anti-dilutive securities excluded from the computation of diluted net loss per share attributable to common shareholders


	Year Ended March 31,
	2019	2018	2017
Options to purchase common stock	3,721,784	2,520,247	930,027
Convertible preferred stock (as converted to common stock)	—	19,157,360	10,588,977
Warrants to purchase convertible preferred stock (as converted to common stock)	497,344	497,344	497,344
	4,219,128	22,174,951	12,016,348

Commitments and contingencies (Tables)

12 Months Ended

Mar. 31, 2019

Commitments and contingencies

Schedule of lease agreement for its new office, manufacturing and laboratory space


	Year Ended
	March 31, 2019
Rent expense	$	556
Amounts capitalized as build-to-suit lease	$	11,514

Schedule of future minimum lease payments under non cancelable operating lease commitments


2020	$	2,062
2021		2,901
2022		2,493
2023		2,568
2024		2,645
2025		2,725
Thereafter		12,770
	$	28,164

Income taxes (Tables)

12 Months Ended

Mar. 31, 2019

Income taxes

Schedule of net loss before income taxes


	Year Ended March 31,
	2019		2018		2017
United States	$	(9,483)	$	(8,992)	$	(3,450)
Foreign (United Kingdom)		(21,351)		(10,710)		(4,254)
	$	(30,834)	$	(19,702)	$	(7,704)

Schedule of reconciliation of the U.S federal statutory income tax rate


	March 31,
	2019		2018		2017
U.S. Federal statutory income tax rate	(21.00)	%	(21.00)	%	(34.00)	%
State taxes, net of federal benefit	(1.5)		(2.6)		(2.4)
Research and development expenses	3.1		3.8		7.1
Remeasurement of deferred taxes as a result of tax reform	—		2.6		—
Foreign tax rate differential	2.4		2.2		8.8
Change in valuation allowance	15.5		14.0		19.2
Other	1.5		1.0		1.3
Effective income tax rate	0.00	%	0.00	%	0.00	%

Schedule of components of deferred tax assets and liabilities


	March 31,
	2019		2018
Deferred tax assets:
Foreign net operating loss carryforwards	$	4,079	$	1,405
Federal net operating loss carryforwards		2,223		—
State net operating loss carryforwards		684		15
Capitalized start-up costs		1,886		3,340
Stock compensation		573		—
Accrued expenses		1,793		—
Other		—		1
Total deferred tax assets		11,238		4,761
Deferred tax liabilities:
Property, plant and equipment		(1,842)		(37)
Total deferred tax liabilities		(1,842)		(37)
Valuation allowance		(9,396)		(4,724)
Net deferred tax assets	$	—	$	—

Schedule of valuation allowance for deferred tax assets


	March 31,
	2019		2018
Valuation allowance as of beginning of year	$	4,724	$	1,887
Increases recorded to income tax provision		4,672		3,347
Remeasurement of deferred taxes as a result of tax reform		—		(510)
Valuation allowance as of end of year	$	9,396	$	4,724

Geographic Information (Tables)

12 Months Ended

Mar. 31, 2019

Geographic Information

Summary of company's long-lived assets held in different geographic regions


	March 31,
	2019		2018
United States	$	11,648	$	20
United Kingdom		511		350
	$	12,159	$	370

Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Mar. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information


	For the Quarter Ended
	March 31, 2019	December 31, 2018	September 30, 2018	June 30, 2018
Operating expenses	7,825	10,137	7,104	5,879
Net loss	(6,656)	(7,673)	(6,461)	(10,044)
Net loss per share attributable to common
shareholders, basic and diluted	(0.29)	(0.24)	(0.26)	(2.02)


	For the Quarter Ended
	March 31, 2018	December 31, 2017	September 30, 2017	June 30, 2017
Operating expenses	7,065	4,732	4,256	3,176
Net loss	(7,136)	(4,354)	(4,660)	(3,552)
Net loss per share attributable to common
shareholders, basic and diluted	(1.43)	(0.87)	(0.94)	(0.71)

Nature of the business (Details) $ / shares in Units, $ in Thousands					3 Months Ended								12 Months Ended
	Jul. 30, 2018 USD ($) $ / shares shares	Jul. 24, 2018 USD ($) $ / shares shares	Jul. 09, 2018 shares	Jul. 10, 2017	Mar. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2019 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) $ / shares shares	Mar. 31, 2017 USD ($)
Shares issued in exchange of shares in Replimune Group, Inc				1
Ratio of replacement warrants to capital stock				1
Forward stock split ratio for each common stock			9.94688
Common stock, authorized \| shares			27,314,288		150,000,000				27,314,288				150,000,000	27,314,288
Proceeds from issuance of common stock in initial public offering, net of underwriting fees and discounts													$ 103,341
Payment of initial public offering costs													$ 2,157
Common stock, par value (in dollars per share) \| $ / shares					$ 0.001				$ 0.001				$ 0.001	$ 0.001
Repurchase of class A common stock upon closing of initial public offering (in shares) \| shares		26,258
Net loss					$ (6,656)	$ (7,673)	$ (6,461)	$ (10,044)	$ (7,136)	$ (4,354)	$ (4,660)	$ (3,552)	$ (30,834)	$ (19,702)	$ (7,704)
Accumulated deficit					$ (59,766)				$ (28,932)				$ (59,766)	$ (28,932)
IPO
Shares issued \| shares	707,936	6,700,000
Shares issued price (in dollars per share) \| $ / shares	$ 15.00	$ 15.00
Proceeds from issuance of common stock in initial public offering, net of underwriting fees and discounts	$ 9,876	$ 93,465
Payment of initial public offering costs		$ 2,157
Common stock, par value (in dollars per share) \| $ / shares		$ 0.001
Undesignated preferred stock, authorized \| shares		10,000,000			10,000,000								10,000,000
Preferred stock, Par Value (in dollars per share) \| $ / shares		$ 0.001			$ 0.001								$ 0.001
IPO \| Maximum
Common stock, authorized \| shares		150,000,000

Summary of significant accounting policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Summary of significant accounting policies
Cash equivalents	$ 10,664	$ 4,130
Restricted cash	1,186	78
Deferred offering costs	2,157
Research and development incentives	2,528	2,267	$ 1,442
Research and development incentives receivable current	2,474	2,389
Foreign currency translation gain (loss)	(897)	2,376	(1,437)
Net unrealized gain (loss) on short-term investments, net of tax	$ 80	(65)
Minimum percentage of benefit recognized is being realized upon ultimate settlement	50.00%
Lease, Practical Expedients, Package	true
Credit cards
Summary of significant accounting policies
Restricted cash	$ 0	78
Operating lease
Summary of significant accounting policies
Restricted cash	$ 1,186	0
ASU 2016-18
Summary of significant accounting policies
Restricted cash		$ 78	$ 75
Maximum \| United Kingdom
Summary of significant accounting policies
Percentage of qualifying research and development expenses reimbursed by government	14.50%
Office equipment
Summary of significant accounting policies
Estimated Useful life's of property, plant and equipment (in years)	5 years
Computer equipment
Summary of significant accounting policies
Estimated Useful life's of property, plant and equipment (in years)	3 years
Plant and laboratory equipment
Summary of significant accounting policies
Estimated Useful life's of property, plant and equipment (in years)	5 years
Leasehold improvements
Summary of significant accounting policies
Estimated Useful life's of property, plant and equipment (in years)	10 years

Fair value of financial assets and liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair value of financial assets and liabilities
Transfer from Leve 1 to Level 2, assets	$ 0	$ 0
Transfer from Leve 2 to Level 1, assets	0	0
Transfers into Level 3, assets	0	0
Transfer out of Level 3, assets	0	0
Transfer from Leve 1 to Level 2, liabilities	0	0
Transfer from Leve 2 to Level 1, liabilities	0	0
Transfers into Level 3, liabilities	0	0
Transfer out of Level 3, liabilities	0	0
Recurring
Fair value of financial assets and liabilities
Assets fair value	119,771	48,098
Liabilities fair value		1,642
Level 2 \| Recurring
Fair value of financial assets and liabilities
Assets fair value	119,771	48,098
Level 3 \| Recurring
Fair value of financial assets and liabilities
Liabilities fair value		1,642
Money market funds \| Recurring
Fair value of financial assets and liabilities
Assets fair value	2,676	4,130
Money market funds \| Level 2 \| Recurring
Fair value of financial assets and liabilities
Assets fair value	2,676	4,130
Commercial paper \| Recurring
Fair value of financial assets and liabilities
Assets fair value	46,687	27,998
Commercial paper \| Level 2 \| Recurring
Fair value of financial assets and liabilities
Assets fair value	46,687	27,998
US Government Agency bonds \| Recurring
Fair value of financial assets and liabilities
Assets fair value	20,884
US Government Agency bonds \| Level 2 \| Recurring
Fair value of financial assets and liabilities
Assets fair value	20,884
US Treasury bonds \| Recurring
Fair value of financial assets and liabilities
Assets fair value	41,057
US Treasury bonds \| Level 2 \| Recurring
Fair value of financial assets and liabilities
Assets fair value	41,057
Corporate debt securities \| Recurring
Fair value of financial assets and liabilities
Assets fair value	8,467	15,970
Corporate debt securities \| Level 2 \| Recurring
Fair value of financial assets and liabilities
Assets fair value	$ 8,467	15,970
Warrant liability \| Recurring
Fair value of financial assets and liabilities
Liabilities fair value		1,642
Warrant liability \| Level 3 \| Recurring
Fair value of financial assets and liabilities
Liabilities fair value		$ 1,642

Fair value of financial assets and liabilities - Unobservable inputs of the warrant liability (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2019 USD ($) item $ / shares	Mar. 31, 2018 USD ($) item
Unobservable inputs of the warrant liability
Warrant liability \| $	$ 0	$ 1,642
Warrant liability fair value of series seed preferred stock (in dollars per share) \| $ / shares	$ 15.00
Risk-free interest rate
Unobservable inputs of the warrant liability
Warrant liability inputs	2.81	2.69
Expected dividend yield
Unobservable inputs of the warrant liability
Warrant liability inputs	0	0
Expected term
Unobservable inputs of the warrant liability
Warrant liability expected term (in years)	7 years 2 months 12 days	7 years 6 months
Expected volatility
Unobservable inputs of the warrant liability
Warrant liability inputs	64.4	65.8

Fair value of financial assets and liabilities - Roll forward of the warrant liability (Details) - Warrant liability $ in Thousands	12 Months Ended
	Mar. 31, 2019 USD ($)
Roll forward of the warrant liability
Balance at beginning of the period	$ 1,642
Change in fair value	5,452
Conversion of convertible preferred stock warrant into common stock warrant	$ (7,094)

Short-term investments (Details) - Short-term investments - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Short-term investments
Amortized cost	$ 109,092	$ 44,033
Gross unrealized gains	19	2
Gross unrealized losses	(4)	(67)
Fair value	109,107	43,968
Commercial paper
Short-term investments
Amortized cost	46,687	28,028
Gross unrealized gains	2	2
Gross unrealized losses	(2)	(32)
Fair value	46,687	27,998
US Government Agency bonds
Short-term investments
Amortized cost	15,889
Gross unrealized gains	4
Fair value	15,893
US Treasury bonds
Short-term investments
Amortized cost	38,047
Gross unrealized gains	13
Fair value	38,060
Corporate debt securities
Short-term investments
Amortized cost	8,469	16,005
Gross unrealized losses	(2)	(35)
Fair value	$ 8,467	$ 15,970

Property, plant and equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Property, plant and equipment, net
Property, plant and equipment , gross	$ 12,563	$ 626
Less: Accumulated depreciation and amortization	(404)	(256)
Property, plant and equipment , net	12,159	370
Depreciation and amortization expense	148	109	$ 122
Leasehold improvements
Property, plant and equipment, net
Property, plant and equipment , gross	154	154
Construction in Progress
Property, plant and equipment, net
Property, plant and equipment , gross	124
Build-to-suit lease asset
Property, plant and equipment, net
Property, plant and equipment , gross	11,514
Lease capitalized asset	11,514
Office equipment
Property, plant and equipment, net
Property, plant and equipment , gross	49	49
Computer equipment
Property, plant and equipment, net
Property, plant and equipment , gross	138	87
Plant and laboratory equipment
Property, plant and equipment, net
Property, plant and equipment , gross	$ 584	$ 336

Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Accrued expenses and other current liabilities
Accrued research and development costs	$ 530	$ 949
Accrued compensation and benefits costs	1,510	949
Accrued professional fees	464	1,094
Deferred rent	24	26
Other	273	153
Total	$ 2,801	$ 3,171

Convertible preferred stock (Details) $ in Thousands		12 Months Ended
Convertible preferred stock (Details) $ in Thousands	Jul. 25, 2018 shares	Mar. 31, 2019 USD ($) shares	Mar. 31, 2018 USD ($) shares	Mar. 31, 2017 shares
Convertible preferred stock
Conversion ratio	9.94688
Preferred stock outstanding \| $		$ 0
Preferred shares authorized (in shares)		0	1,975,968
Preferred shares issued (in shares)		0	1,925,968
Preferred shares outstanding (in shares)		0	1,925,968
Common stock
Convertible preferred stock
Conversion of convertible preferred stock warrants into common stock warrants (in shares)	19,157,360
Common stock issuable upon conversion (in shares)			9.94688
Convertible preferred stock (as converted to common stock)
Convertible preferred stock
Conversion of convertible preferred stock warrants into common stock warrants (in shares)		(1,925,968)
Preferred shares authorized (in shares)			1,975,968
Preferred shares issued (in shares)			1,925,968
Preferred shares outstanding (in shares)			1,925,968	1,064,553
Carrying value \| $			$ 86,361
Liquidation preference \| $			$ 86,950
Common stock issuable upon conversion (in shares)			19,157,360
Series Seed preferred stock
Convertible preferred stock
Preferred shares authorized (in shares)			250,000
Preferred shares issued (in shares)			200,000
Preferred shares outstanding (in shares)			200,000
Carrying value \| $			$ 1,609
Liquidation preference \| $			$ 2,000
Common stock issuable upon conversion (in shares)			1,989,376
Series A preferred stock
Convertible preferred stock
Preferred shares authorized (in shares)			864,553
Preferred shares issued (in shares)			864,553
Preferred shares outstanding (in shares)			864,553
Carrying value \| $			$ 30,000
Liquidation preference \| $			$ 30,000
Common stock issuable upon conversion (in shares)			8,599,601
Series B preferred stock
Convertible preferred stock
Preferred shares authorized (in shares)			861,415
Preferred shares issued (in shares)			861,415
Preferred shares outstanding (in shares)			861,415
Carrying value \| $			$ 54,752
Liquidation preference \| $			$ 54,950
Common stock issuable upon conversion (in shares)			8,568,383

Convertible preferred stock rights and preferences (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2019 USD ($) director $ / shares	Mar. 31, 2018 $ / shares shares
Voting
Number of directors to be elected \| director	2
Convertible preferred stock (as converted to common stock)
Conversion
Outstanding preferred stock held for conversion (as a percent)	75.00%
Conversion ratio (in shares) \| shares		19,157,360
Dividends
Dividends declared (in dollars per share)	$ 0.00
Dividends paid \| $	$ 0
Series Seed preferred stock
Voting
Number of directors to be elected \| director	2
Conversion
Share price (in dollars per share)		$ 1.01
Conversion ratio (in shares) \| shares		1,989,376
Conversion price (in dollars per share)		$ 10.00
Series A preferred stock
Voting
Number of directors to be elected \| director	1
Conversion
Share price (in dollars per share)		$ 3.49
Conversion ratio (in shares) \| shares		8,599,601
Conversion price (in dollars per share)		$ 34.70
Liquidation preference
Liquidation preference (in dollars per share)	$ 69.40
Series B preferred stock
Voting
Number of directors to be elected \| director	2
Outstanding preferred stock held (as a percent)	55.00%
Conversion
Share price (in dollars per share)		$ 6.41
Outstanding preferred stock held relating to liquidation preference (as a percent)	55.00%
Conversion ratio (in shares) \| shares		8,568,383
Conversion price (in dollars per share)		$ 63.79
Liquidation preference
Liquidation preference (in dollars per share)	$ 127.58
Common stock
Conversion
Conversion ratio (in shares) \| shares		9.94688
Common stock \| IPO
Conversion
Gross proceeds \| $	$ 30,000
Share price (in dollars per share)	$ 9.62

Preferred stock warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Preferred stock warrants
Fair value of the warrant liability	$ 0	$ 1,642
Loss from change in fair value of the warrant liability	$ 5,452	972	$ 150
Series Seed preferred stock
Preferred stock warrants
Number of preferred stock warrants issued	50,000
Exercise price (in dollars per share)	$ 10.00
Fair value of the warrants to purchase shares of series seed preferred stock	$ 391
Other income (expense), net
Preferred stock warrants
Loss from change in fair value of the warrant liability	$ 5,452	$ 972	$ 150

Stockholders' Equity (Details) $ / shares in Units, $ in Thousands		1 Months Ended		12 Months Ended
	Jul. 24, 2018 $ / shares shares	Jul. 31, 2018 $ / shares shares	Jul. 31, 2017 $ / shares shares	Mar. 31, 2019 USD ($) director Vote $ / shares shares	Jul. 09, 2018 shares	Mar. 31, 2018 $ / shares shares
Stockholders' equity
Shares authorized (in shares)				150,000,000	27,314,288	27,314,288
Par value (in dollars per share) \| $ / shares				$ 0.001		$ 0.001
Repurchase of class A common stock upon closing of initial public offering (in shares)	26,258
IPO
Stockholders' equity
Par value (in dollars per share) \| $ / shares	$ 0.001
Undesignated preferred stock, authorized	10,000,000			10,000,000
Preferred stock, Par Value (in dollars per share) \| $ / shares	$ 0.001			$ 0.001
Undesignated preferred shares issued				0
Common stock
Stockholders' equity
Shares authorized (in shares)				150,000,000		27,314,288
Par value (in dollars per share) \| $ / shares				$ 0.001		$ 0.001
Common stock reserved for the conversion of outstanding shares of preferred stock				6,873,744		22,306,801
Number of vote per share \| Vote				1
Number of directors to be elected \| director				2
Cash dividends declared (in dollars per share) \| $ / shares				$ 0
Cash dividends paid \| $				$ 0
Common A stock
Stockholders' equity
Shares authorized (in shares)				0		26,258
Par value (in dollars per share) \| $ / shares		$ 0.001	$ 0.001
Issuance of common stock upon closing of initial public offering, net of issuance costs and underwriter fees of $9,935 (shares)			26,258
Repurchase of class A common stock upon closing of initial public offering (in shares)		26,258
Maximum \| IPO
Stockholders' equity
Shares authorized (in shares)	150,000,000
Maximum \| Common A stock
Stockholders' equity
Dividends to be received upon declaration (as a percent)				100.00%
Dividends to be received upon deemed liquidation (as a percent)				300.00%

Stock Based Compensation (Details) - shares		12 Months Ended
Stock Based Compensation (Details) - shares	Jul. 09, 2018	Mar. 31, 2019
2017 Plan
Share based payments
Total number of common shares authorized to issue		2,659,885
Number of shares available for grant		0
2017 Plan \| Maximum
Share based payments
Number of shares available for grant	2,520,247
2018 Plan
Share based payments
Total number of common shares authorized to issue	3,617,968
Number of shares available for grant		2,306,004
ESPP
Share based payments
Common stock reserved for issuance	348,612
Share based payment award percentage of outstanding shares	1.00%
Additional number of common shares authorized to issue	697,224
Stock options
Share based payments
Exercise price for persons holding ten percent of voting power (as a percent)		100.00%
Exercise price for persons holding more than ten percent of voting power (as a percent)		110.00%
Share based payment award expiration period		10 years
Share based payment award vesting period		4 years
Stock options \| Minimum
Share based payments
Expiration period for persons holding more than ten percent of voting power		10 years
Stock options \| Maximum
Share based payments
Expiration period for persons holding ten percent of voting power		5 years

Stock Based Compensation - Assumptions to determine grant-date fair value of stock options (Details)	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Employees stock options
Stock-Based Compensation
Risk-free interest rate	2.81%	2.01%	1.67%
Expected term (in years)	6 years 1 month 6 days	6 years	6 years
Expected volatility	62.00%	75.00%	75.00%
Expected dividend yield	0.00%	0.00%	0.00%
Non employee stock options
Stock-Based Compensation
Risk-free interest rate		2.29%
Expected term (in years)		10 years
Expected volatility		75.00%
Expected dividend yield		0.00%

Stock Based Compensation - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Number of Shares
Outstanding at beginning of the period (in shares)	2,520,247
Granted (in shares)	1,371,500
Exercised (in shares)	(110,427)
Cancelled (in shares)	(59,536)
Outstanding at end of the period (in shares)	3,721,784	2,520,247
Options exercisable (in shares)	1,278,330	592,349
Weighted Average Exercise Price
Outstanding at beginning of the period (in dollars per share)	$ 2.72
Granted (in dollars per share)	14.92
Exercised (in dollars per share)	1.87
Cancelled (in dollars per share)	8.65
Outstanding at end of the period (in dollars per share)	7.14	$ 2.72
Options exercisable (in dollars per share)	$ 2.51	$ 1.84
Weighted Average Contractual Term (Years)
Outstanding (years)	8 years 7 months 10 days	8 years 10 months 28 days
Granted (years)	9 years 9 months 11 days
Options exercisable (years)	7 years 9 months	8 years 2 months 19 days
Aggregate Intrinsic Value
Outstanding at beginning of the period	$ 2,808
Outstanding at end of the period	30,150	$ 2,808
Options exercisable	$ 16,249	$ 1,184
Weighted average grant-date fair value per share of stock options granted	$ 8.82	$ 1.92
Total fair value of options vested	$ 1,298	$ 398
Outstanding unvested service-based stock options	0

Stock Based Compensation - Classification of expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Share-Based Compensation
Total share based compensation expense	$ 2,730	$ 812	$ 208
Total unrecognized compensation cost	$ 11,807
Expenses expected to be recognized over a weighted average remaining period	2 years 4 months 10 days
Research and development expenses
Share-Based Compensation
Total share based compensation expense	$ 1,488	335	65
General and administrative expenses
Share-Based Compensation
Total share based compensation expense	$ 1,242	$ 477	$ 143

Net loss per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net loss attributable to common stockholders									$ (30,834)	$ (19,702)	$ (7,704)
Denominator:
Weighted average common shares outstanding basic and diluted									23,198,400	4,978,539	4,973,439
Net loss per share attributable to common stockholders, basic and diluted	$ (0.29)	$ (0.24)	$ (0.26)	$ (2.02)	$ (1.43)	$ (0.87)	$ (0.94)	$ (0.71)	$ (1.33)	$ (3.96)	$ (1.55)

Net loss per share - Computation of diluted net loss per share attributable to common stockholders (Details) - shares	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of diluted weighted average shares outstanding	4,219,128	22,174,951	12,016,348
Options to purchase common stock
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of diluted weighted average shares outstanding	3,721,784	2,520,247	930,027
Convertible preferred stock (as converted to common stock)
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of diluted weighted average shares outstanding		19,157,360	10,588,977
Warrants to purchase convertible preferred stock (as converted to common stock)
Diluted net loss per share attributable to common stockholders
Antidilutive securities excluded from computation of diluted weighted average shares outstanding	497,344	497,344	497,344

Significant agreements (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Significant agreements
Prepaid expenses and other current assets	$ 3,696	$ 763
Agreement with Regeneron Pharmaceuticals, Inc
Significant agreements
Prepaid expenses and other current assets	$ 337

Commitments and contingencies - Lease agreements (Details) $ in Thousands	1 Months Ended			8 Months Ended	12 Months Ended			28 Months Ended
	Jun. 30, 2018 USD ($) ft² Option	Apr. 30, 2016	Dec. 31, 2015 USD ($)	Dec. 03, 2016 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2019 USD ($)
Lease agreements
Number of options to extend lease agreement (in years)			5 years
Monthly lease payments, inclusive of base rent and ancillary charges			$ 7
Prior notice period upon termination of lease		9 months
Base rent of monthly lease payments				$ 23				$ 31
Leased office space \| ft²	63,000
Rentable office space \| ft²	106,000
Lease term	10 years
Number of options to renewal the lease \| Option	2
Renewal period of lease	5 years
Annual rental payment	$ 2,373
Percentage of annual increase in lease rental expenses	3.00%
Operating lease, paid					$ 1,474			1,474
Operating lease, remained payable					5,047
Operating lease, reimbursable by the landlord					2,174			$ 2,174
Ground rent					93
Rent expense					556	$ 430	$ 282
Amounts capitalized as build-to-suit lease					4,993
new office, manufacturing and laboratory space
Lease agreements
Rent expense					556
Amounts capitalized as build-to-suit lease					11,514
office, manufacturing and laboratory space
Lease agreements
Amounts capitalized as build-to-suit lease					$ 6,521

Commitments and contingencies - Future minimum lease payments due under the Company's operating leases (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Future minimum lease payments due under the Company's operating leases
2020	$ 2,062
2021	2,901
2022	2,493
2023	2,568
2024	2,645
2025	2,725
Thereafter	12,770
Total	$ 28,164

Income taxes (Details) - USD ($) $ in Thousands			12 Months Ended
Income taxes (Details) - USD ($) $ in Thousands	Jan. 01, 2018	Dec. 22, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Income taxes
Corporate tax rate	21.00%	35.00%	21.00%	21.00%	34.00%
Percentage of limitation on deduction for net operating losses		80.00%
Income tax benefit			$ 0	$ 0	$ 0
Net loss before income taxes
United States			(9,483)	(8,992)	(3,450)
Foreign (United Kingdom)			(21,351)	(10,710)	(4,254)
Net loss before income taxes			$ (30,834)	$ (19,702)	$ (7,704)

Income taxes - Reconciliation of the U.S federal statutory income tax rate (Details)			12 Months Ended
	Jan. 01, 2018	Dec. 22, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Reconciliation of the U.S federal statutory income tax rate
U.S. Federal statutory income tax rate	(21.00%)	(35.00%)	(21.00%)	(21.00%)	(34.00%)
State taxes, net of federal benefit			(1.50%)	(2.60%)	(2.40%)
Research and development expenses			3.10%	3.80%	7.10%
Remeasurement of deferred taxes as a result of tax reform				2.60%
Foreign tax rate differential			2.40%	2.20%	8.80%
Change in valuation allowance			15.50%	14.00%	19.20%
Other			1.50%	1.00%	1.30%
Effective income tax rate			0.00%	0.00%	0.00%

Income taxes - Components of deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Deferred tax assets:
Foreign net operating loss carryforwards	$ 4,079	$ 1,405
Federal net operating loss carryforwards	2,223
State net operating loss carryforwards	684	15
Capitalized start-up costs	1,886	3,340
Stock compensation	573
Accrued expenses	1,793
Other		1
Total deferred tax assets	11,238	4,761
Deferred tax liabilities:
Property, plant and equipment	(1,842)	(37)
Total deferred tax liabilities	(1,842)	(37)
Valuation allowance	(9,396)	$ (4,724)	$ (1,887)
Deferred tax assets operating loss carryforwards
Federal net operating loss carryforwards having indefinite expiration period	10,587
Foreign net operating loss carryforwards having indefinite expiration period	23,993
State net operating loss carryforwards, expires between 2038 and 2039	$ 10,822

Income taxes - Valuation allowance for deferred tax assets (Details)	12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)
Deferred tax assets, Valuation allowance
Valuation allowance as of beginning of year	$ 4,724,000	$ 1,887,000
Increases recorded to income tax provision	4,672,000	3,347,000
Remeasurement of deferred taxes as a result of tax reform		(510,000)
Deferred Tax Assets, Valuation Allowance	4,724,000	1,887,000	$ 1,887,000	$ 9,396,000	$ 4,724,000
Accrued interest or penalties related to uncertain tax positions				$ 0	$ 0
Income tax benefit	$ 0	$ 0	$ 0
Number of pending tax examination	0

Geographic Information (Details) $ in Thousands	12 Months Ended
Geographic Information (Details) $ in Thousands	Mar. 31, 2019 USD ($) item	Mar. 31, 2018 USD ($)
Geographic Information
Number of operating geographic regions \| item	2
Long-lived assets	$ 12,159	$ 370
United States
Geographic Information
Long-lived assets	11,648	20
United Kingdom
Geographic Information
Long-lived assets	$ 511	$ 350

Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Operating expenses	$ 7,825	$ 10,137	$ 7,104	$ 5,879	$ 7,065	$ 4,732	$ 4,256	$ 3,176	$ 30,946	$ 19,229	$ 9,647
Net loss	$ (6,656)	$ (7,673)	$ (6,461)	$ (10,044)	$ (7,136)	$ (4,354)	$ (4,660)	$ (3,552)	$ (30,834)	$ (19,702)	$ (7,704)
Net loss per share attributable to common shareholders, basic and diluted (in dollars per share)	$ (0.29)	$ (0.24)	$ (0.26)	$ (2.02)	$ (1.43)	$ (0.87)	$ (0.94)	$ (0.71)	$ (1.33)	$ (3.96)	$ (1.55)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Subsequent Events (Details) $ in Thousands	1 Months Ended
Subsequent Events (Details) $ in Thousands	Jun. 30, 2019 USD ($) ft²	Jun. 30, 2018 USD ($) ft²	Apr. 30, 2019 shares	Jul. 09, 2018 shares
Lease agreements
Leased office space \| ft²		63,000
Lease term		10 years
Renewal period of lease		5 years
Annual rental payment \| $		$ 2,373
Percentage of annual increase in lease rental expenses		3.00%
2018 Plan
Share based payments
Total number of common shares authorized to issue				3,617,968
Subsequent events
Lease agreements
Leased office space \| ft²	18,700
Lease term	10 years
Renewal period of lease	5 years
Annual rental payment \| $	$ 488
Percentage of annual increase in lease rental expenses	1.60%
Subsequent events \| 2018 Plan \| Minimum
Share based payments
Total number of common shares authorized to issue			3,617,968
Subsequent events \| 2018 Plan \| Maximum
Share based payments
Total number of common shares authorized to issue			4,884,338

Benefit Plans	12 Months Ended
Benefit Plans	Mar. 31, 2019
Benefit Plans
Benefit Plans	14. Benefit Plans The Company established a defined‑contribution savings plan under Section 401(k) of the Code (the “401(k) Plan”). The 401(k) Plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre‑tax basis. Matching contributions to the 401(k) Plan may be made at the discretion of the Company’s board of directors. During the years ended March 31, 2019, 2018 and 2017, the Company made contributions totaling $102, $49 and $8, respectively, to the 401(k) Plan. We provide a pension contribution plan for our employees in the United Kingdom, pursuant to which we match our employees’ contributions each year in amounts up to 8% of their annual base salary.

Commitments and contingencies - Manufacturing commitments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Commitments and contingencies
Minimum payments committed to manufacturing organization	$ 2,938	$ 4,694

Benefit Plans (Details) - USD ($) $ in Thousands	12 Months Ended
Benefit Plans (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
401(k) Plan
Benefit Plans
Contributions to the plan	$ 102	$ 49	$ 8
Pension Plan
Benefit Plans
Maximum percentage of contribution by employee of their annual base salary	8.00%