Sio Gene Therapies (SIOX) 10-Q 12 Nov 21 2022 Q2 Quarterly report Financial data

Cover

Cover - shares	6 Months Ended
	Sep. 30, 2021	Nov. 10, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-37418
Entity Registrant Name	Sio Gene Therapies Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	85-3863315
Entity Address, Address Line One	130 West 42nd St.
Entity Address, Address Line Two	26th Floor
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10036
City Area Code	(877)
Local Phone Number	746-4891
Title of 12(b) Security	Common Stock, par value $0.00001 per share
Trading Symbol	SIOX
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		73,488,721
Entity Central Index Key	0001636050
Amendment Flag	false
Current Fiscal Year End Date	--03-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Mar. 31, 2021
Current assets:
Cash and cash equivalents	$ 101,695	$ 118,986
Restricted cash	1,184	0
Receivable from sale of long-term investment	0	4,343
Prepaid expenses and other current assets	4,321	7,348
Income tax receivable	1,733	1,656
Total current assets	108,933	132,333
Long-term restricted cash	0	1,184
Operating lease right-of-use assets	1,052	1,152
Property and equipment, net	548	478
Total assets	110,533	135,147
Current liabilities:
Accounts payable	2,673	1,341
Accrued expenses	7,366	9,196
Current portion of operating lease liabilities	269	311
Total current liabilities	10,308	10,848
Operating lease liabilities, net of current portion	865	932
Total liabilities	11,173	11,780
Commitments and contingencies
Stockholders’ equity:
Common stock, par value $0.00001 per share, 1,000,000,000 shares authorized, 72,941,507 and 69,377,567 issued and outstanding at September 30, 2021 and March 31, 2021, respectively	1	1
Additional paid-in capital	923,198	914,100
Accumulated deficit	(824,176)	(791,069)
Accumulated other comprehensive income	337	335
Total stockholders’ equity	99,360	123,367
Total liabilities and stockholders’ equity	$ 110,533	$ 135,147

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2021	Mar. 31, 2021
Common stock
Common shares par value (in dollars per share)	$ 0.00001	$ 0.00001
Common shares authorized (in shares)	1,000,000,000	1,000,000,000
Common shares issued (in shares)	72,941,507	69,377,567
Common shares outstanding (in shares)	72,941,507	69,377,567

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating expenses:
Research and development expenses	$ 11,448	$ 5,058	$ 19,506	$ 10,252
General and administrative expenses	9,748	4,491	13,607	9,131
Total operating expenses	21,196	9,549	33,113	19,383
Other (income) expenses:
Interest expense	11	1	12	797
Other expense (income)	30	580	10	(1,486)
Loss before income tax benefit	(21,237)	(10,130)	(33,135)	(18,694)
Income tax benefit	0	(146)	(28)	(116)
Net loss	$ (21,237)	$ (9,984)	$ (33,107)	$ (18,578)
Net loss per share of common stock — basic (in dollars per share)	$ (0.29)	$ (0.21)	$ (0.45)	$ (0.41)
Net loss per share of common stock — diluted (in dollars per share)	$ (0.29)	$ (0.21)	$ (0.45)	$ (0.41)
Weighted-average shares of common stock outstanding — basic (in shares)	72,941,507	46,731,666	72,901,906	45,018,855
Weighted-average shares of common stock outstanding — diluted (in shares)	72,941,507	46,731,666	72,901,906	45,018,855

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Research and development expenses
Stock-based compensation expense	$ 489	$ 458	$ 921	$ 1,021
General and administrative expenses
Stock-based compensation expense	$ 6,809	$ 650	$ 7,698	$ 1,677

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net loss	$ (21,237)	$ (9,984)	$ (33,107)	$ (18,578)
Other comprehensive income:
Foreign currency translation adjustment	0	348	2	392
Total other comprehensive income	0	348	2	392
Comprehensive loss	$ (21,237)	$ (9,636)	$ (33,105)	$ (18,186)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Beginning balance (in shares) at Mar. 31, 2020		39,526,299
Beginning balance at Mar. 31, 2020	$ 61,558	$ 0	$ 820,257	$ (758,644)	$ (55)
Increase (Decrease) in Shareholders' Equity (Deficit)
Shares issued upon settlement of restricted stock units (in shares)		53,653
Shares sold in connection with at-the-market offering, net of brokerage fees and offering expenses (in shares)		1,393,428
Shares sold in connection with at-the-market offering, net of brokerage fees and offering expenses	3,930		3,930
Stock-based compensation expense	1,590		1,590
Capital contribution received from affiliate	53		53
Foreign currency translation adjustment	44				44
Net loss	(8,594)			(8,594)
Ending balance (in shares) at Jun. 30, 2020		40,973,380
Ending balance at Jun. 30, 2020	58,581	$ 0	825,830	(767,238)	(11)
Beginning balance (in shares) at Mar. 31, 2020		39,526,299
Beginning balance at Mar. 31, 2020	61,558	$ 0	820,257	(758,644)	(55)
Increase (Decrease) in Shareholders' Equity (Deficit)
Foreign currency translation adjustment	392
Net loss	(18,578)
Ending balance (in shares) at Sep. 30, 2020		47,249,729
Ending balance at Sep. 30, 2020	69,673	$ 0	846,558	(777,222)	337
Beginning balance (in shares) at Mar. 31, 2020		39,526,299
Beginning balance at Mar. 31, 2020	61,558	$ 0	820,257	(758,644)	(55)
Increase (Decrease) in Shareholders' Equity (Deficit)
Net loss	(32,400)
Ending balance (in shares) at Mar. 31, 2021		69,377,567
Ending balance at Mar. 31, 2021	123,367	$ 1	914,100	(791,069)	335
Beginning balance (in shares) at Jun. 30, 2020		40,973,380
Beginning balance at Jun. 30, 2020	58,581	$ 0	825,830	(767,238)	(11)
Increase (Decrease) in Shareholders' Equity (Deficit)
Shares issued upon settlement of restricted stock units (in shares)		60,676
Shares sold in connection with at-the-market offering, net of brokerage fees and offering expenses (in shares)		6,215,673
Shares sold in connection with at-the-market offering, net of brokerage fees and offering expenses	19,598		19,598
Stock-based compensation expense	1,108		1,108
Capital contribution received from affiliate	22		22
Foreign currency translation adjustment	348				348
Net loss	(9,984)			(9,984)
Ending balance (in shares) at Sep. 30, 2020		47,249,729
Ending balance at Sep. 30, 2020	69,673	$ 0	846,558	(777,222)	337
Beginning balance (in shares) at Mar. 31, 2021		69,377,567
Beginning balance at Mar. 31, 2021	123,367	$ 1	914,100	(791,069)	335
Increase (Decrease) in Shareholders' Equity (Deficit)
Shares issued upon settlement of restricted stock units (in shares)		82,542
Shares sold in connection with at-the-market offering, net of brokerage fees and offering expenses (in shares)		179,400
Shares sold in connection with at-the-market offering, net of brokerage fees and offering expenses	479		479
Stock-based compensation expense	1,321		1,321
Foreign currency translation adjustment	2				2
Net loss	(11,870)			(11,870)
Ending balance (in shares) at Jun. 30, 2021		69,639,509
Ending balance at Jun. 30, 2021	113,299	$ 1	915,900	(802,939)	337
Beginning balance (in shares) at Mar. 31, 2021		69,377,567
Beginning balance at Mar. 31, 2021	123,367	$ 1	914,100	(791,069)	335
Increase (Decrease) in Shareholders' Equity (Deficit)
Foreign currency translation adjustment	2
Net loss	(33,107)
Ending balance (in shares) at Sep. 30, 2021		72,941,507
Ending balance at Sep. 30, 2021	99,360	$ 1	923,198	(824,176)	337
Beginning balance (in shares) at Jun. 30, 2021		69,639,509
Beginning balance at Jun. 30, 2021	113,299	$ 1	915,900	(802,939)	337
Increase (Decrease) in Shareholders' Equity (Deficit)
Shares issued upon exercise of pre-funded warrants (in shares)		3,301,998
Stock-based compensation expense	7,298		7,298
Foreign currency translation adjustment	0
Net loss	(21,237)			(21,237)
Ending balance (in shares) at Sep. 30, 2021		72,941,507
Ending balance at Sep. 30, 2021	$ 99,360	$ 1	$ 923,198	$ (824,176)	$ 337

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Stockholders’ Equity (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020
Statement of Stockholders' Equity [Abstract]
Brokerage fees and offering expenses	$ 0	$ 0.7	$ 0.5

Condensed Consolidated Statem_6

Condensed Consolidated Statement of Cash Flows - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2021
Cash flows from operating activities:
Net loss	$ (21,237)	$ (11,870)	$ (9,984)	$ (8,594)	$ (33,107)	$ (18,578)	$ (32,400)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of operating lease right-of-use assets					100	869
Stock-based compensation expense					8,619	2,698
Depreciation and non-cash amortization					122	672
Gain on long-term investment					0	(2,184)
Change in operating lease liabilities					(109)	(879)
Other					4	399
Changes in operating assets and liabilities:
Prepaid expenses and other current assets					3,027	(2,435)
Income tax receivable					(77)	(40)
Other non-current assets					0	(123)
Accounts payable					1,332	(2,240)
Accrued expenses					(1,830)	(3,482)
Net cash used in operating activities					(21,919)	(25,323)
Cash flows from investing activities:
Cash proceeds from sale of long-term investment					4,343	0
Purchases of property and equipment					(194)	(130)
Net cash provided by (used in) investing activities					4,149	(130)
Cash flows from financing activities:
Payments on long-term debt					0	(15,731)
Capital contributions received from affiliate					0	75
Cash proceeds from issuance of shares of common stock, net of issuance costs					479	23,528
Net cash provided by financing activities					479	7,872
Net change in cash and cash equivalents, restricted cash and long-term restricted cash					(17,291)	(17,581)
Total cash and cash equivalents, restricted cash and long-term restricted cash—beginning of period		120,170		80,752	120,170	80,752	80,752
Total cash and cash equivalents, restricted cash and long-term restricted cash—end of period	102,879		63,171		102,879	63,171	120,170
Cash and cash equivalents—beginning of period		118,986		80,752	118,986	80,752	80,752
Restricted cash included in long-term assets—beginning of period		$ 1,184		$ 0	1,184	0	0
Cash and cash equivalents—end of period	101,695		63,171		101,695	63,171	118,986
Restricted cash included in current assets—end of period	$ 1,184		$ 0		$ 1,184	$ 0	$ 0

Description of Business

Description of Business	6 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Sio Gene Therapies Inc. ("Sio"), together with its wholly owned subsidiaries (the "Company"), is a clinical-stage company focused on developing gene therapies for neurodegenerative diseases. The Company is developing a pipeline of innovative product candidates for the treatment of these debilitating diseases, including GM1 gangliosidosis, GM2 gangliosidosis (including Tay-Sachs and Sandhoff diseases) and Parkinson's disease. The Company is dedicated to realizing the potential of gene therapies to offer transformative patient outcomes in areas of high unmet medical need. Sio is a Delaware corporation, which was originally an exempted limited company incorporated under the laws of Bermuda in October 2014 and was named Axovant Gene Therapies Ltd. ("AGT") from March 2019 until November 2020. During November 2020, the Company completed a corporate transformation, changing its jurisdiction of incorporation from Bermuda to the State of Delaware, changing its name to Sio Gene Therapies Inc., and changing its ticker symbol on The Nasdaq Global Select Market (“Nasdaq”) to “SIOX” (collectively, these events comprise the “Domestication”). The Company continues to be subject to the reporting requirements of the Securities Exchange Act of 1934, as amended, and applicable rules of Nasdaq. Since its initial public offering in 2015, the Company has devoted substantially all of its efforts to raising capital, acquiring product candidates and advancing its product candidates into clinical development. The Company has determined that it has one operating and reporting segment as it allocates resources and assesses financial performance on a consolidated basis. The Company does not expect to generate revenue unless and until it successfully completes development and obtains regulatory approval for one of its product candidates.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies (A) Basis of Presentation: The Company’s fiscal year ends on March 31, and its fiscal quarters end on June 30, September 30 and December 31. These unaudited condensed consolidated financial statements and accompanying notes have been prepared in accordance with accounting principles generally accepted in the United States ("U.S. GAAP") for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements and accompanying notes should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended March 31, 2021 (the "Annual Report"), filed with the SEC on June 9, 2021. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary to present fairly the financial position of the Company and its results of operations and cash flows for the periods presented have been included. Operating results for the three and six-months ended September 30, 2021 are not necessarily indicative of the results that may be expected for the year ending March 31, 2022, for any other interim period, or for any other future year. Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP as found in the Accounting Standards Codification ("ASC"), and as amended by Accounting Standards Updates ("ASU"), issued by the Financial Accounting Standards Board ("FASB"). These unaudited condensed consolidated financial statements and accompanying notes include the accounts of the Company and its wholly owned subsidiaries. The Company has no unconsolidated subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Certain prior period balances have been reclassified to conform to the current period presentation. During November 2020, the historical financial statements and subsidiaries of AGT became the historical financial statements and subsidiaries of Sio upon consummation of the Domestication. As a result, these unaudited condensed consolidated financial statements and accompanying notes reflect (i) the historical operating results of AGT and its subsidiaries prior to the Domestication; (ii) the operating results of the Company following the Domestication; and (iii) the Company’s equity structure for all periods presented. There have been no significant changes in the Company’s accounting policies from those disclosed in its Annual Report. B) Going Concern and Management's Plans: The Company assesses and determines its ability to continue as a going concern in accordance with the provisions of ASC Subtopic 205-40, " Presentation of Financial Statements—Going Concern " ("ASC Subtopic 205-40"), which requires the Company to evaluate whether there are conditions or events that raise substantial doubt about its ability to continue as a going concern within one year after the date that its annual and interim consolidated financial statements and accompanying notes are issued. Certain additional financial statement disclosures are required if such conditions or events are identified. If and when an entity’s liquidation becomes imminent, financial statements should be prepared under the liquidation basis of accounting. Determining the extent, if any, to which conditions or events raise substantial doubt about the Company’s ability to continue as a going concern, or the extent to which mitigating plans sufficiently alleviate any such substantial doubt, as well as whether or not liquidation is imminent, requires judgment by management. The Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the consolidated financial statements and accompanying notes are issued. The Company is currently a development stage company, and thus, has not yet achieved profitability. The Company expects to continue to incur significant operating and net losses, as well as negative cash flows from operations, for the foreseeable future as it continues to develop its gene therapy product candidates and prepares for potential future regulatory approvals and commercialization of its products. The Company has not generated any revenue to date and does not expect to generate product revenue unless and until it successfully completes development and obtains regulatory approval for at least one of its gene therapy product candidates. The Company's current cash and cash equivalents balance will also not be sufficient to complete all necessary development activities and commercially launch its products. For the six months ended September 30, 2021 and the fiscal year ended March 31, 2021, the Company incurred net losses of $33.1 million and $32.4 million, respectively. As of September 30, 2021, the Company’s cash and cash equivalents totaled $101.7 million and its accumulated deficit was $824.2 million. The Company estimates that its current cash and cash equivalents balance is sufficient to support operations into the fourth calendar quarter of 2022, including beyond the expected dates of major upcoming milestones for the Company's AXO-AAV-GM1 gene therapy program for the treatment of GM1 gangliosidosis. In order to continue as a going concern and to meet the Company's long-term operating requirements, the Company will need, among other things, additional capital resources. The Company continually assesses multiple options to obtain additional funding to support its operations, including proceeds from offerings of its equity securities or debt, or transactions involving product development, technology licensing or collaboration arrangements, or other sources of capital to complete its currently planned development programs. Management can provide no assurances that it can raise a sufficient amount of financing for the Company on favorable terms, if at all. Although the Company has successfully obtained financing in the past, future financing activities that are not probable of being implemented and probable of alleviating the conditions that raise substantial doubt are not permitted to be included in the Company's assessment of its liquidity. Due to these uncertainties, there is substantial doubt about the Company’s ability to continue as going concern beyond the twelve-month period following the date that these unaudited condensed consolidated financial statements and accompanying notes were issued. These unaudited condensed consolidated financial statements and accompanying notes have been prepared on the basis that the Company will continue as a going concern, and do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classification of liabilities that may result from the possible inability of the Company to continue as a going concern. (C) Use of Estimates: The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company regularly evaluates estimates and assumptions related to certain assets and liabilities, including its research and development accruals, as well as assumptions used to estimate the fair value of its stock option awards, estimate its income tax expense and estimate its ability to continue as a going concern. Specifically, the Company’s assessment of the completeness of the information for research and development accruals is subject to variability and uncertainty. In addition, in certain circumstances, the determination of the nature and amount of research and development services that have been received during the reporting period requires judgment as the timing and pattern of vendor invoicing does not correspond to the level of services provided. The Company estimates the grant date fair value of stock option awards with only time-based vesting requirements using a Black-Scholes valuation model and uses a Monte Carlo Simulation method under the income approach to estimate the grant date fair value of stock option awards with market-based performance conditions. The Company bases its estimates and assumptions on historical experience and on various other factors that it believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates. Additionally, the Company assessed the impact that the COVID-19 pandemic has had on its operations and financial results as of September 30, 2021 and through the date of issuance of these unaudited condensed consolidated financial statements and accompanying notes. The Company’s analysis was informed by the facts and circumstances as they were known to the Company. This assessment considered the impact COVID-19 may have on financial estimates and assumptions that affect the reported amounts of assets and liabilities and expenses. (D) Net Loss per Share of Common Stock: Basic net loss per share of common stock is computed by dividing the net loss applicable to holders of common stock by the weighted-average number of shares of common stock and 3,301,998 pre-funded warrants (see Note 7(B)) outstanding during the period, without further consideration for potentially dilutive securities. The pre-funded warrants were fully exercised in July 2021 (see Note 7(B)). In accordance with ASC Topic 260, Earnings Per Share , the pre-funded warrants were included in the computation of basic net loss per share because the exercise price was negligible and they were fully vested and exercisable at any time after the original issuance date. Diluted net loss per share of common stock is computed by dividing the net loss applicable to holders of common stock by the diluted weighted-average number of shares of common stock outstanding during the period calculated in accordance with the treasury stock method. In periods in which the Company reports a net loss, all common stock equivalents are deemed anti-dilutive such that basic net loss per share of common stock and diluted net loss per share of common stock are equivalent. Potentially dilutive shares of common stock have been excluded from the diluted net loss per share of common stock computations in all periods presented because such securities have an anti-dilutive effect on net loss per share of common stock due to the Company’s net loss. Restricted Stock Units ("RSUs") and stock options outstanding for totals of 5.5 million and 3.1 million shares of common stock were not included in the calculation of diluted weighted-average shares of common stock outstanding for the three and six- months ended September 30, 2021 and September 30, 2020, respectively, because they were anti-dilutive given the net loss of the Company. (E) Financial Instruments and Fair Value Measurement: The Company utilizes fair value measurement guidance prescribed by accounting standards to value its financial instruments. The guidance establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. Fair value is defined as the exchange price, or exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, the guidance establishes a three-tier fair value hierarchy that distinguishes among the following: • Level 1-Valuations are based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access. • Level 2-Valuations are based on quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active and models for which all significant inputs are observable, either directly or indirectly. • Level 3-Valuations are based on inputs that are unobservable (supported by little or no market activity) and significant to the overall fair value measurement. To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The Company’s financial instruments include cash and cash equivalents and restricted cash. Cash consists of non-interest-bearing deposits denominated in the U.S. dollar, Swiss franc and Euro, while cash equivalents consists of interest-bearing money market fund deposits denominated in the U.S. dollar, which are invested in debt securities issued or guaranteed by the U.S. government and repurchase agreements fully collateralized by U.S. Treasury and U.S. government securities, and restricted cash consists of non-interest-bearing deposits denominated in the U.S. dollar. Cash and restricted cash are stated at their historical carrying amounts, which approximate fair value due to their short-term nature. The carrying values of the Company's money market fund included in cash and cash equivalents of $100.0 million and $114.0 million at September 30, 2021 and March 31, 2021, respectively, approximated their fair values, which are based on quoted prices in active markets for identical securities. The following table summarizes the fair value of the Company's money market fund included in cash equivalents based on the inputs used at September 30, 2021 and March 31, 2021 in determining such values (in thousands): As of September 30, 2021 As of March 31, 2021 Fair Value Price Quotations (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value Price Quotations (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market fund $ 100,000 $ 100,000 $ — $ — $ 114,000 $ 114,000 $ — $ — (F) Recent Accounting Pronouncements: In June 2016, the FASB issued ASU No. 2016-13, “ Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments " ("ASU No. 2016-13"). ASU 2016-13 requires that financial assets measured at amortized cost, such as loans, accounts and trade receivables and investments, be represented net of expected credit losses, which may be estimated based on relevant information such as historical experience, current conditions, and future expectation for each pool of similar financial asset. ASU No. 2016-13 requires enhanced disclosures related to trade receivables and associated credit losses. In May 2019, the FASB issued ASU No. 2019-05, “Financial Instruments — Credit Losses (Topic 326): Targeted Transition Relief ", which allows for a transition election on certain instruments and is effective for Small Reporting Companies for fiscal years beginning after December 15, 2022 and interim periods in those fiscal years. In November 2019, the FASB issued ASU No. 2019-11, " Codification Improvements to Topic 326, Financial Instruments — Credit Losses ", which amends certain aspects of ASU NO. 2016-13, including transition relief for trouble debt restructuring, among other topics. While the Company does not expect the adoption of this guidance to materially impact the Company's consolidated financial statements and accompanying notes because it does not currently have any investments or trade receivables outstanding, the impact on the Company's consolidated financial statements and accompanying notes will depend on the facts and circumstances of any specific future transactions. Other recent accounting pronouncements issued by the FASB (including its Emerging Issues Task Force), the American Institute of Certified Public Accountants, and the SEC did not, or are not, believed by management to have a material impact on the Company’s present or future consolidated financial position, results of operations or cash flows.

License and Collaboration Agree

License and Collaboration Agreements	6 Months Ended
	Sep. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License and Collaboration Agreements	License and Collaboration Agreements (A) The University of Massachusetts Medical School Exclusive License Agreement: In December 2018, the Company entered into an exclusive license agreement (the "UMMS Agreement") with the University of Massachusetts Medical School ("UMMS"), pursuant to which the Company received a worldwide, royalty-bearing, sub-licensable license under certain patent applications and any patents issuing therefrom, biological materials and know-how controlled by UMMS to develop and commercialize gene therapy product candidates, including AXO-AAV-GM1 and AXO-AAV-GM2, for the treatment of GM1 gangliosidosis and GM2 gangliosidosis (including Tay-Sachs disease and Sandhoff disease), respectively. During the three and six-months ended September 30, 2021, the Company incurred a total of $6.9 million and $10.3 million, respectively, of program-specific costs related to its AXO-AAV-GM1 and AXO-AAV-GM2 programs within research and development expenses in its unaudited condensed consolidated statements of operations and $0.4 million and $0.8 million during the three and six-months ended September 30, 2020, respectively. The Company paid UMMS a total of $0.3 million and $1.9 million during the three and six-months ended September 30, 2021, respectively, and $12 thousand during the three and six-months ended September 30, 2020. (B) Oxford Biomedica License Agreement: In June 2018, the Company entered into an exclusive license agreement ("the Oxford Agreement") with Oxford Biomedica (UK) Ltd. ("Oxford"), pursuant to which the Company received a worldwide, exclusive, royalty-bearing, sub-licensable license under certain patents and other intellectual property controlled by Oxford to develop and commercialize AXO-Lenti-PD and related gene therapy products for all diseases and conditions. The Company incurred $0.5 million and $1.0 million of AXO-Lenti-PD program-specific costs within research and development expenses in its unaudited condensed consolidated statement of operations during the three and six-months ended September 30, 2021, respectively, and $1.7 million and $3.4 million during the three and six-months ended September 30, 2020, respectively. The Company paid Oxford a total of $0 and $22 thousand during the three and six-months ended September 30, 2021, respectively, and $0.6 million and $1.1 million during the three and six-months ended September 30, 2020, respectively.

Investment in Arvelle Therapeut

Investment in Arvelle Therapeutics B.V.	6 Months Ended
	Sep. 30, 2021
Investments, All Other Investments [Abstract]
Investment in Arvelle Therapeutics B.V.	Investment in Arvelle Therapeutics B.V.In February 2021, the Company sold its investment of 8.1 million shares of nonredeemable preferred stock (the "Arvelle Shares") of Arvelle Therapeutics B.V. ("Arvelle") to a third party as part of that third party's cash acquisition of all of the outstanding equity of Arvelle. In exchange, the Company received an upfront payment of approximately $11.6 million, in addition to a future payment to be received of approximately $1.2 million that is being held in escrow until August 2022 and that is recorded as restricted cash in the Company's unaudited condensed consolidated balance sheet at September 30, 2021, as well as the right to receive up to an additional total of $7.0 million in potential future regulatory and sales milestone payments (collectively, the "Arvelle Sale"). The Company originally purchased its Arvelle Shares in February 2019 and May 2020 in exchange for €0.00001 per share paid in cash, as well as certain goods and services provided by the Company to Arvelle. The Company recorded a net gain of approximately $4.7 million to other non-operating income in the Company's consolidated statement of operations upon the closing of the Arvelle Sale in February 2021, as well as a gain of approximately $4.3 million recorded to other non-operating income in the Company's consolidated statement of operations and to receivable from sale of long-term investment in its consolidated balance sheet upon the achievement of a regulatory milestone in March 2021 that was collected during the three months ended June 30, 2021.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Sep. 30, 2021
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses As of September 30, 2021, and March 31, 2021, accrued expenses consisted of the following (in thousands): September 30, 2021 March 31, 2021 Research and development expenses $ 4,625 $ 6,091 Bonuses and other compensation expenses 1,893 2,331 Other expenses 848 774 Total accrued expenses $ 7,366 $ 9,196

Long Term Debt

Long Term Debt	6 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Long Term Debt	Long-term DebtIn April 2020, the Company fully prepaid $15.7 million of outstanding principal, together with $0.3 million of accrued interest, fees and other amounts, due under its loan and security agreement (the "Loan Agreement") with Hercules Capital, Inc. ("Hercules"), which was accounted for as an extinguishment of debt with a corresponding loss of approximately $0.5 million recorded to interest expense during the three months ended June 30, 2020. In connection with the prepayment, the credit facility and the Loan Agreement with Hercules were terminated, and all obligations, liens and security interests under the Loan Agreement were released, discharged and satisfied.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Sep. 30, 2021
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders' Equity (A) Overview: Sio's Certificate of Incorporation filed with the State of Delaware on November 12, 2020 authorizes the issuance of up to a total of 1,010,000,000 shares, of which 1,000,000,000 shares are common stock with a par value of $0.00001 per share and 10,000,000 shares are preferred stock with a par value of $0.00001 per share (see Note 1). (B) Transactions: In February 2020, as part of a follow-on public offering, the Company issued and sold pre-funded warrants to purchase up to 3,301,998 shares of common stock at an offering price of $3.74999 and an exercise price of $0.00001 per pre-funded warrant, which were fully exercised in July 2021. The pre-funded warrants were classified as equity and the fair value of the pre-funded warrants was recorded as a credit to additional paid-in capital and was not subject to remeasurement.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Sep. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation (A) Amended and Restated 2015 Equity Incentive Plan: In March 2015, the Company adopted its 2015 Equity Incentive Plan, which was (i) amended and restated in June 2017 by its Board of Directors and became effective upon stockholder approval in August 2017, (ii) further amended and restated in October 2020 by its Board of Directors, and (iii) further amended and restated in August 2021 by its Board of Directors and became effective upon stockholder approval in September 2021 (the "2015 Plan"). In April 2021 and April 2020, the number of shares of common stock authorized for issuance under the 2015 Plan increased automatically by 2.8 million and 1.6 million, respectively, in accordance with the terms of the 2015 Plan. Upon amendment and restatement by the Company's board of directors and stockholder approval of the 2015 Plan in August 2021 and September 2021, respectively, the number of shares of common stock authorized for issuance under the 2015 Plan increased by 5.0 million. At September 30, 2021, totals of 13.4 million shares of common stock were authorized for issuance and 7.4 million shares of common stock were available for future issuance under the 2015 Plan. (B) Stock Options: Time-based stock options granted to the Company's employees vest over a period of either (i) four years with 25% of the shares of common stock underlying the option vesting on the first anniversary of the vesting commencement date and the remainder vesting in 12 equal quarterly installments thereafter for such stock options granted prior to April 2021, or (ii) three years with one-third of the shares of common stock underlying the stock option vesting on the first anniversary of the vesting commencement date and the remainder vesting in 8 equal quarterly installments thereafter for such stock options granted since April 2021, each subject to continuing service. Initial stock options granted to the Company's non-employee directors vest in equal installments on the first, second and third anniversaries of the vesting commencement date, and stock options subsequently granted annually to the Company's non-employee directors vest fully on the first anniversary of the vesting commencement date, each subject to continuous service. Options with market-based performance conditions vest based on the trading price for the Company's shares of common stock exceeding certain closing price thresholds. Stock options granted under the 2015 Plan provide option holders, if provided for by the terms of the option agreement or if approved by the Board of Directors, the right to exercise their options prior to vesting. In the event that an option holder exercises the unvested portion of any option, such unvested portion will be subject to a repurchase option held by the Company at the lower of (i) the fair market value of its common stock on the date of repurchase and (ii) the exercise price of the options. Any shares of common stock underlying such unvested portion will continue to vest in accordance with the original vesting schedule of the option. During the six months ended September 30, 2021 and 2020, the Company granted options to purchase totals of 1.6 million shares and 0.4 million shares, respectively, of its common stock under the 2015 Plan, with weighted-average exercise prices of $2.47 and $3.45, respectively, and estimated aggregate grant date fair values of $3.3 million and $1.1 million, respectively. There were no options with market-based performance conditions granted under the 2015 Plan during the six months ended September 30, 2021 and 2020. At September 30, 2021, options to purchase a total of 3.5 million shares of common stock were outstanding under the 2015 Plan with a weighted-average exercise price of $7.71 per share, including options with market-based performance conditions to purchase 0.4 million shares of common stock at a weighted average exercise price of $8.87 per share. At September 30, 2021, vested options to purchase a total of 1.0 million shares of common stock were outstanding under the 2015 Plan, with no options with market-based performance conditions vested and outstanding. During the six months ended September 30, 2021 and 2020, the aggregate grant date fair values of stock options that vested under the 2015 Plan were $1.5 million and $2.5 million, respectively. (C) Restricted Stock Units: RSUs granted during the six months ended September 30, 2021 and September 30, 2020 vest in three equal annual installments commencing on the first anniversary of the vesting commencement date, subject to continuing service. Of the total number of RSUs granted in September 2019 representing approximately 0.3 million shares of the Company's common stock, one-half vested on January 31, 2020 and the remaining one-half vested on July 31, 2020, subject to continuing service. During the six months ended September 30, 2021 and September 30, 2020, the Company granted RSUs for totals of 1.2 million and 1.0 million shares, respectively, of its common stock to its employees under the 2015 Plan, with aggregate grant date fair values of $3.1 million and $3.4 million, respectively. At September 30, 2021, RSUs for approximately 1.9 million shares of common stock were outstanding, of which approximately 0.2 million were vested. During the six months ended September 30, 2021 and September 30, 2020, the total grant date fair values of RSUs that vested under the 2015 Plan were $0.9 million and $1.0 million, respectively. (D) Stock-based Compensation Expense: The Company recorded total stock-based compensation expense of $1.4 million and $2.7 million for the three and six-months ended September 30, 2021, respectively, and $1.1 million and $2.7 million for the three and six-months ended September 30, 2020, respectively, related to options and RSUs granted to its employees and directors, excluding stock-based compensation expense allocated to the Company from its affiliate, Roivant Sciences Ltd. ("RSL") (see Note 8(E)). This stock-based compensation expense was included in research and development and general and administrative expenses in the Company's unaudited condensed consolidated statements of operations. At September 30, 2021, total unrecognized compensation expense for unvested outstanding option and RSU equity awards of the Company's common stock granted to its employees and directors under the 2015 Plan was $9.4 million, which is expected to be recognized over a remaining weighted-average service period of 2.16 years. (E) RSL Equity Instruments: Certain employees of the Company have been granted RSL equity instruments for which the Company recognized stock-based compensation expense of $5.9 million and $5.9 million during the three and six-months ended September 30, 2021, respectively, and which is recorded to general and administrative expenses in the Company's unaudited condensed consolidated statements of operations. Certain of these RSL equity instruments were granted to the Company's Chief Executive Officer, which will vest upon the achievement of both time-based service requirements and liquidity requirements on or before the grant expiration date of March 31, 2026. The liquidity vesting event requirement was determined to be met upon the closing of RSL's business combination with Montes Archimedes Acquisition Corp., a special purpose acquisition company, on September 30, 2021. Accordingly, the Company commenced recognition of stock-based compensation expense for the RSL equity instruments held by the Company's Chief Executive Officer on September 30, 2021. At September 30, 2021, total unrecognized compensation expense for such unvested outstanding RSL equity instruments granted to the Company's Chief Executive Officer was $1.7 million.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies As of September 30, 2021, the Company had entered into commitments under the UMMS Agreement (see Note 3(A)), the Oxford Agreement (see Note 3(B)), services agreements with certain of RSL's wholly owned subsidiaries and agreements to rent office space. In addition, the Company has entered into services agreements with third parties for pharmaceutical manufacturing and research activities in the normal course of business, which can generally be terminated by the Company with 30- to 60-days' written notice, unless otherwise indicated. Further, certain of the Company's manufacturing agreements could require early termination and wind-down payments due from the Company upon either the termination of its clinical trials or if the Company terminates such agreements for convenience. The Company has the right to terminate the UMMS Agreement at any time upon 90 days' advance written notice to UMMS. Either party may terminate the UMMS Agreement for the other party's uncured material breach upon 60 days' advance written notice, including in the event that UMMS reasonably determines the Company has not fulfilled its diligence obligations.

Subsequent Events

Subsequent Events	6 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Subsequent to September 30, 2021, the Company sold approximately 0.5 million shares of its common stock for total proceeds of approximately $1.1 million, net of brokerage fees, through SVB Leerink LLC as placement agent. In November 2021, the Company entered into a lease agreement that commenced for a research and development facility and related office space in Durham, North Carolina, with an initial term expiring in December 2024. The total amount of undiscounted contractual rent obligations due under this lease agreement is approximately $1.9 million. This lease is classified as an operating lease in accordance with the provisions of ASU No. 2016-02, " Topic 842 — Leases ".

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation: The Company’s fiscal year ends on March 31, and its fiscal quarters end on June 30, September 30 and December 31. These unaudited condensed consolidated financial statements and accompanying notes have been prepared in accordance with accounting principles generally accepted in the United States ("U.S. GAAP") for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements and accompanying notes should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended March 31, 2021 (the "Annual Report"), filed with the SEC on June 9, 2021. In the opinion of management, all adjustments (consisting of normal recurring adjustments) considered necessary to present fairly the financial position of the Company and its results of operations and cash flows for the periods presented have been included. Operating results for the three and six-months ended September 30, 2021 are not necessarily indicative of the results that may be expected for the year ending March 31, 2022, for any other interim period, or for any other future year. Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP as found in the Accounting Standards Codification ("ASC"), and as amended by Accounting Standards Updates ("ASU"), issued by the Financial Accounting Standards Board ("FASB"). These unaudited condensed consolidated financial statements and accompanying notes include the accounts of the Company and its wholly owned subsidiaries. The Company has no unconsolidated subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Certain prior period balances have been reclassified to conform to the current period presentation. During November 2020, the historical financial statements and subsidiaries of AGT became the historical financial statements and subsidiaries of Sio upon consummation of the Domestication. As a result, these unaudited condensed consolidated financial statements and accompanying notes reflect (i) the historical operating results of AGT and its subsidiaries prior to the Domestication; (ii) the operating results of the Company following the Domestication; and (iii) the Company’s equity structure for all periods presented. There have been no significant changes in the Company’s accounting policies from those disclosed in its Annual Report.
Going Concern and Management's Plans	Going Concern and Management's Plans: The Company assesses and determines its ability to continue as a going concern in accordance with the provisions of ASC Subtopic 205-40, " Presentation of Financial Statements—Going Concern " ("ASC Subtopic 205-40"), which requires the Company to evaluate whether there are conditions or events that raise substantial doubt about its ability to continue as a going concern within one year after the date that its annual and interim consolidated financial statements and accompanying notes are issued. Certain additional financial statement disclosures are required if such conditions or events are identified. If and when an entity’s liquidation becomes imminent, financial statements should be prepared under the liquidation basis of accounting. Determining the extent, if any, to which conditions or events raise substantial doubt about the Company’s ability to continue as a going concern, or the extent to which mitigating plans sufficiently alleviate any such substantial doubt, as well as whether or not liquidation is imminent, requires judgment by management. The Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the consolidated financial statements and accompanying notes are issued. The Company is currently a development stage company, and thus, has not yet achieved profitability. The Company expects to continue to incur significant operating and net losses, as well as negative cash flows from operations, for the foreseeable future as it continues to develop its gene therapy product candidates and prepares for potential future regulatory approvals and commercialization of its products. The Company has not generated any revenue to date and does not expect to generate product revenue unless and until it successfully completes development and obtains regulatory approval for at least one of its gene therapy product candidates. The Company's current cash and cash equivalents balance will also not be sufficient to complete all necessary development activities and commercially launch its products. For the six months ended September 30, 2021 and the fiscal year ended March 31, 2021, the Company incurred net losses of $33.1 million and $32.4 million, respectively. As of September 30, 2021, the Company’s cash and cash equivalents totaled $101.7 million and its accumulated deficit was $824.2 million. The Company estimates that its current cash and cash equivalents balance is sufficient to support operations into the fourth calendar quarter of 2022, including beyond the expected dates of major upcoming milestones for the Company's AXO-AAV-GM1 gene therapy program for the treatment of GM1 gangliosidosis. In order to continue as a going concern and to meet the Company's long-term operating requirements, the Company will need, among other things, additional capital resources. The Company continually assesses multiple options to obtain additional funding to support its operations, including proceeds from offerings of its equity securities or debt, or transactions involving product development, technology licensing or collaboration arrangements, or other sources of capital to complete its currently planned development programs. Management can provide no assurances that it can raise a sufficient amount of financing for the Company on favorable terms, if at all. Although the Company has successfully obtained financing in the past, future financing activities that are not probable of being implemented and probable of alleviating the conditions that raise substantial doubt are not permitted to be included in the Company's assessment of its liquidity. Due to these uncertainties, there is substantial doubt about the Company’s ability to continue as going concern beyond the twelve-month period following the date that these unaudited condensed consolidated financial statements and accompanying notes were issued. These unaudited condensed consolidated financial statements and accompanying notes have been prepared on the basis that the Company will continue as a going concern, and do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classification of liabilities that may result from the possible inability of the Company to continue as a going concern.
Use of Estimates	Use of Estimates:The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company regularly evaluates estimates and assumptions related to certain assets and liabilities, including its research and development accruals, as well as assumptions used to estimate the fair value of its stock option awards, estimate its income tax expense and estimate its ability to continue as a going concern. Specifically, the Company’s assessment of the completeness of the information for research and development accruals is subject to variability and uncertainty. In addition, in certain circumstances, the determination of the nature and amount of research and development services that have been received during the reporting period requires judgment as the timing and pattern of vendor invoicing does not correspond to the level of services provided. The Company estimates the grant date fair value of stock option awards with only time-based vesting requirements using a Black-Scholes valuation model and uses a Monte Carlo Simulation method under the income approach to estimate the grant date fair value of stock option awards with market-based performance conditions. The Company bases its estimates and assumptions on historical experience and on various other factors that it believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results could differ from those estimates.Additionally, the Company assessed the impact that the COVID-19 pandemic has had on its operations and financial results as of September 30, 2021 and through the date of issuance of these unaudited condensed consolidated financial statements and accompanying notes. The Company’s analysis was informed by the facts and circumstances as they were known to the Company. This assessment considered the impact COVID-19 may have on financial estimates and assumptions that affect the reported amounts of assets and liabilities and expenses.
Net Loss per Share of Common Stock	Net Loss per Share of Common Stock: Basic net loss per share of common stock is computed by dividing the net loss applicable to holders of common stock by the weighted-average number of shares of common stock and 3,301,998 pre-funded warrants (see Note 7(B)) outstanding during the period, without further consideration for potentially dilutive securities. The pre-funded warrants were fully exercised in July 2021 (see Note 7(B)). In accordance with ASC Topic 260, Earnings Per Share , the pre-funded warrants were included in the computation of basic net loss per share because the exercise price was negligible and they were fully vested and exercisable at any time after the original issuance date. Diluted net loss per share of common stock is computed by dividing the net loss applicable to holders of common stock by the diluted weighted-average number of shares of common stock outstanding during the period calculated in accordance with the treasury stock method. In periods in which the Company reports a net loss, all common stock equivalents are deemed anti-dilutive such that basic net loss per share of common stock and diluted net loss per share of common stock are equivalent. Potentially dilutive shares of common stock have been excluded from the diluted net loss per share of common stock computations in all periods presented because such securities have an anti-dilutive effect on net loss per share of common stock due to the Company’s net loss. Restricted Stock Units ("RSUs") and stock options outstanding for totals of 5.5 million and 3.1 million shares of common stock were not included in the calculation of diluted weighted-average shares of common stock outstanding for the three and six- months ended September 30, 2021 and September 30, 2020, respectively, because they were anti-dilutive given the net loss of the Company.
Financial Instruments and Fair Value Measurement	Financial Instruments and Fair Value Measurement: The Company utilizes fair value measurement guidance prescribed by accounting standards to value its financial instruments. The guidance establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. Fair value is defined as the exchange price, or exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, the guidance establishes a three-tier fair value hierarchy that distinguishes among the following: • Level 1-Valuations are based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access. • Level 2-Valuations are based on quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active and models for which all significant inputs are observable, either directly or indirectly. • Level 3-Valuations are based on inputs that are unobservable (supported by little or no market activity) and significant to the overall fair value measurement. To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.
Recent Accounting Pronouncements	Recent Accounting Pronouncements: In June 2016, the FASB issued ASU No. 2016-13, “ Financial Instruments — Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments " ("ASU No. 2016-13"). ASU 2016-13 requires that financial assets measured at amortized cost, such as loans, accounts and trade receivables and investments, be represented net of expected credit losses, which may be estimated based on relevant information such as historical experience, current conditions, and future expectation for each pool of similar financial asset. ASU No. 2016-13 requires enhanced disclosures related to trade receivables and associated credit losses. In May 2019, the FASB issued ASU No. 2019-05, “Financial Instruments — Credit Losses (Topic 326): Targeted Transition Relief ", which allows for a transition election on certain instruments and is effective for Small Reporting Companies for fiscal years beginning after December 15, 2022 and interim periods in those fiscal years. In November 2019, the FASB issued ASU No. 2019-11, " Codification Improvements to Topic 326, Financial Instruments — Credit Losses ", which amends certain aspects of ASU NO. 2016-13, including transition relief for trouble debt restructuring, among other topics. While the Company does not expect the adoption of this guidance to materially impact the Company's consolidated financial statements and accompanying notes because it does not currently have any investments or trade receivables outstanding, the impact on the Company's consolidated financial statements and accompanying notes will depend on the facts and circumstances of any specific future transactions. Other recent accounting pronouncements issued by the FASB (including its Emerging Issues Task Force), the American Institute of Certified Public Accountants, and the SEC did not, or are not, believed by management to have a material impact on the Company’s present or future consolidated financial position, results of operations or cash flows.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Fair Value of Cash Equivalents	The following table summarizes the fair value of the Company's money market fund included in cash equivalents based on the inputs used at September 30, 2021 and March 31, 2021 in determining such values (in thousands): As of September 30, 2021 As of March 31, 2021 Fair Value Price Quotations (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Fair Value Price Quotations (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Money market fund $ 100,000 $ 100,000 $ — $ — $ 114,000 $ 114,000 $ — $ —

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Sep. 30, 2021
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	As of September 30, 2021, and March 31, 2021, accrued expenses consisted of the following (in thousands): September 30, 2021 March 31, 2021 Research and development expenses $ 4,625 $ 6,091 Bonuses and other compensation expenses 1,893 2,331 Other expenses 848 774 Total accrued expenses $ 7,366 $ 9,196

Description of Business (Detail

Description of Business (Details)	6 Months Ended
	Sep. 30, 2021segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	1
Number of reporting segments	1

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2021	Jul. 31, 2021	Mar. 31, 2020	Feb. 29, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net loss	$ (21,237)	$ (11,870)	$ (9,984)	$ (8,594)	$ (33,107)	$ (18,578)	$ (32,400)
Cash and cash equivalents	101,695		$ 63,171		101,695	$ 63,171	118,986		$ 80,752
(Accumulated deficit) retained earnings	(824,176)				(824,176)		(791,069)
Money Market Funds
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Money market funds	$ 100,000				$ 100,000		$ 114,000
Employee Stock Option and Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in calculation of common shares outstanding (in shares)	5,500,000				5,500,000
Stock Options and RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in calculation of common shares outstanding (in shares)			3,100,000			3,100,000
Public Offering
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Number of securities called by warrants (in shares)								3,301,998		3,301,998

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Money Market Fund (Details) - Money market fund - USD ($) $ in Thousands	Sep. 30, 2021	Mar. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	$ 100,000	$ 114,000
Price Quotations (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	100,000	114,000
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	$ 0	$ 0

License and Collaboration Agr_2

License and Collaboration Agreements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
License Agreement [Line Items]
Research and development expenses	$ 11,448	$ 5,058	$ 19,506	$ 10,252
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | The University of Massachusetts Medical School
License Agreement [Line Items]
Research and development expenses	6,900	400	10,300	800
Payments for license agreement	300	12	1,900	12
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Oxford BioMedica (UK) Ltd.
License Agreement [Line Items]
Research and development expenses	500	1,700	1,000	3,400
Payments for license agreement	$ 0	$ 600	$ 22	$ 1,100

Investment in Arvelle Therape_2

Investment in Arvelle Therapeutics B.V. (Details) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended
	Mar. 31, 2021USD ($)	Feb. 28, 2021USD ($)shares	Nov. 12, 2020$ / shares	May 30, 2020€ / shares	Feb. 28, 2019€ / shares
Schedule of Equity Method Investments [Line Items]
Par value (in EUR per share) | $ / shares			$ 0.00001
Arvelle Therapeutics
Schedule of Equity Method Investments [Line Items]
Maximum shares to be purchased under subscription agreement (in shares) | shares		8.1
Proceeds from sale of investment		$ 11.6
Future payment held in escrow		1.2
Potential future regulatory and sales milestone payments		7
Par value (in EUR per share) | € / shares				€ 0.00001	€ 0.00001
Net gain on sale of investment	$ 4.3	$ 4.7

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Mar. 31, 2021
Payables and Accruals [Abstract]
Research and development expenses	$ 4,625	$ 6,091
Bonuses and other compensation expenses	1,893	2,331
Other expenses	848	774
Total accrued expenses	$ 7,366	$ 9,196

Long Term Debt (Details)

Long Term Debt (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2020	Jun. 30, 2020
Debt Instrument [Line Items]
Extinguishment of debt amount		$ 0.5
Loan and Security Agreement with Hercules Capital, Inc. | Secured Debt
Debt Instrument [Line Items]
Prepayment of outstanding principal due	$ 15.7
Accrued interest, fees and other amounts	$ 0.3

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	6 Months Ended		20 Months Ended
	Nov. 12, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Jul. 31, 2021	Mar. 31, 2021	Nov. 12, 2020	Feb. 29, 2020
Stockholders' Equity
Common shares authorized (in shares)		1,000,000,000		1,000,000,000		1,000,000,000	1,010,000,000
Common shares issued (in shares)		72,941,507		72,941,507		69,377,567	1,000,000,000
Common shares par value (in dollars per share)		$ 0.00001		$ 0.00001		$ 0.00001	$ 0.00001
Preferred stock shares authorized (in shares)							10,000,000
Preferred Stock shares par value (in dollars per share)							$ 0.00001
Stock Offering
Stockholders' Equity
Number of securities called by warrants (in shares)					3,301,998			3,301,998
Warrants issued (in dollars per share)								$ 3.74999
Exercise price (in dollars per share)								$ 0.00001
Private Placement | SVB Leerink LLC
Stockholders' Equity
Percentage of gross proceeds from common stock issuance paid for services								3.00%
Shares sold in common stock issuance (in shares)		200,000	7,600,000	29,800,000
Net proceeds from common stock issued		$ 0.5	$ 24	$ 90.9
Private Placement | SVB Leerink LLC | Subsequent Event
Stockholders' Equity
Shares sold in common stock issuance (in shares)	500,000
Net proceeds from common stock issued	$ 1.1

Stock-Based Compensation (Detai

Stock-Based Compensation (Details) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	2 Months Ended	3 Months Ended		6 Months Ended
	Sep. 30, 2019shares	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2021USD ($)$ / sharesshares	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)installment$ / sharesshares	Sep. 30, 2020USD ($)installment$ / sharesshares	Apr. 30, 2021shares	Apr. 30, 2020shares
Stock-Based Compensation
Fair value of options vested | $					$ 1.5	$ 2.5
Number of shares from vesting (in shares)	0.3
Employees | RSL
Stock-Based Compensation
Stock-based compensation expense | $			$ 5.9		5.9
Chief Executive Officer | RSL
Stock-Based Compensation
Total unrecognized compensation expense, stock options | $		$ 1.7	$ 1.7		$ 1.7
Time-Based Stock Options
Stock-Based Compensation
Number of options vested, outstanding (in shares)		1	1		1
Time-Based Stock Options | Tranche One
Stock-Based Compensation
Vesting period					4 years
RSUs vesting (as a percent)					25.00%
Number of installments | installment					12
Time-Based Stock Options | Tranche Two
Stock-Based Compensation
Vesting period					3 years
RSUs vesting (as a percent)					33.33%
Number of installments | installment					8
Stock Options
Stock-Based Compensation
Total unrecognized compensation expense, stock options | $		$ 9.4	$ 9.4		$ 9.4
Remaining weighted-average service period					2 years 1 month 28 days
Stock Options | Grants to Directors and Employees
Stock-Based Compensation
Stock-based compensation expense | $			$ 1.4	$ 1.1	$ 2.7	$ 2.7
Market-Based Performance Stock Options
Stock-Based Compensation
Number of options granted (in shares)					0	0
Number of options outstanding (in shares)		0.4	0.4		0.4
Weighted average exercise price of options outstanding (in dollars per share) | $ / shares		$ 8.87	$ 8.87		$ 8.87
Number of options vested, outstanding (in shares)		0	0		0
Restricted Stock Units (RSUs)
Stock-Based Compensation
Number of installments | installment					3	3
Fair value of options vested | $					$ 0.9	$ 1
RSUs granted (in shares)					1.2	1
Aggregate grant date fair value of RSUs | $					$ 3.1	$ 3.4
RSUs outstanding (in shares)		1.9	1.9		1.9
RSUs vested (in shares)					0.2
Restricted Stock Units (RSUs) | Tranche One
Stock-Based Compensation
RSUs vesting (as a percent)					50.00%
Restricted Stock Units (RSUs) | Tranche Two
Stock-Based Compensation
RSUs vesting (as a percent)					50.00%
2015 Equity Incentive Plan
Stock-Based Compensation
Shares authorized for issuance (in shares)		13.4	13.4		13.4		2.8	1.6
Share-based compensation , increase in the number of shares authorized (in shares)		5
Number of shares available for future grant (in shares)		7.4	7.4		7.4
2015 Equity Incentive Plan | Stock Options
Stock-Based Compensation
Number of options granted (in shares)					1.6	0.4
Exercise price of options granted (in dollars per share) | $ / shares					$ 2.47	$ 3.45
Estimated grant date fair value of options granted | $					$ 3.3	$ 1.1
Number of options outstanding (in shares)		3.5	3.5		3.5
Weighted average exercise price of options outstanding (in dollars per share) | $ / shares		$ 7.71	$ 7.71		$ 7.71

Commitments and Contingencies (

Commitments and Contingencies (Details) - Collaborative Arrangement, Transaction with Party to Collaborative Arrangement	6 Months Ended
	Sep. 30, 2021
Third Parties for Pharmaceutical Manufacturing and Research Activities | Minimum
Long-term Purchase Commitment [Line Items]
Termination notice term, for uncured material breach from other party	30 days
Third Parties for Pharmaceutical Manufacturing and Research Activities | Maximum
Long-term Purchase Commitment [Line Items]
Termination notice term, for uncured material breach from other party	60 days
The University of Massachusetts Medical School
Long-term Purchase Commitment [Line Items]
Termination notice term	90 days
Oxford BioMedica (UK) Ltd.
Long-term Purchase Commitment [Line Items]
Termination notice term, prior to first commercial sale of product	2 months

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) shares in Millions, $ in Millions	1 Months Ended	6 Months Ended		20 Months Ended
	Nov. 12, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021
Private Placement | SVB Leerink LLC
Subsequent Event [Line Items]
Shares sold in common stock issuance (in shares)		0.2	7.6	29.8
Net proceeds from common stock issued		$ 0.5	$ 24	$ 90.9
Subsequent Event
Subsequent Event [Line Items]
Undiscounted payments	$ 1.9
Subsequent Event | Private Placement | SVB Leerink LLC
Subsequent Event [Line Items]
Shares sold in common stock issuance (in shares)	0.5
Net proceeds from common stock issued	$ 1.1