License, Collaboration and Service Agreements - Additional Information (Detail) $ / shares in Units, £ in Millions		1 Months Ended							3 Months Ended				12 Months Ended
	Jan. 15, 2021 USD ($)	Jun. 30, 2021 USD ($)	Feb. 28, 2021 USD ($) shares	Nov. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2016 GBP (£)	May 31, 2016 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Oct. 31, 2017 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized													$ 3,070,000	$ 258,000
Proceeds from sale of common stock to related party													7,831,000	13,166,000
Common stock issued, aggregate fair value													7,831,000	77,929,000
Pfizer Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of common stock and preferred stock net of offering costs, shares | shares			2,362,348
Common stock issued, aggregate fair value			$ 27,500
Remaining Transaction Price Allocated To Performance Obligations													12,500,000
Cantab Related Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payment upon achievement of specified clinical and regulatory milestones						$ 5,800,000
Potential milestone payment upon achievement of specified commercial milestone							£ 5.0						6,700,000
License agreement research and development expense related to achievement of regulatory milestones													$ 0	0
Contract termination period						10 years	10 years
Vertex License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contract termination period													10 years
Nonrefundable upfront payments								$ 500,000
Potential milestone payment upon achievement of specified clinical, regulatory and commercial milestones								$ 80,200,000
License agreement payment of research and development expense related to achievement of regulatory milestones													$ 0	900,000
Contract termination period if no material development or commercialization occurs													1 year
Meiji License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Nonrefundable upfront payments					$ 600,000
Sublicense fee payable to counter party													$ 7,500,000
Potential milestone payments upon achievement of specified condition																$ 1,000,000.0
License agreement fixed assets related payments												$ 1,600,000
Potential milestone payments upon completion and delivery of results of a clinical study													1,000.0
Future milestone payments													$ 1,000.0
Everest License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Period of option granted on an agreement													12 months
Upfront payment received											$ 3,000,000.0
Potential milestone payments upon completion and delivery of results of a clinical study									$ 2,000,000.0
Upfront license fee													$ 2,000,000.0
Transaction price allocated to the performance obligations													5,000,000.0
Performance obligations exclusive option to negotiate license													1,000,000.0
Performance obligations related to research and development services milestone													2,000,000.0
Revenue recognized													1,300,000	300,000
Everest License Agreement [Member] | SPR206 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment received		$ 800,000									2,000,000.0
Potential milestone payments upon completion and delivery of results of a clinical study	$ 1,500,000	$ 700,000
milestones payment received	$ 1,300,000
Everest License Agreement [Member] | SPR 741 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License agreement research and development expense related to achievement of regulatory milestones										$ 100,000					$ 3,600,000
License agreement payment of research and development expense related to achievement of regulatory milestones										$ 1,300
Upfront payment received											$ 1,000,000.0
Everest License Agreement [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Agreement termination period upon written notice	180 days
Everest License Agreement [Member] | Maximum [Member] | SPR206 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Receivable amount upon achievement of certain milestone	$ 38,000,000.0												59,500,000
Everest License Agreement [Member] | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Agreement termination period upon written notice	90 days
Pfizer License and Share Purchase Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized													$ 1,800,000
Issuance of common stock and preferred stock net of offering costs, shares | shares													2,362,348
Common stock issued, aggregate fair value													$ 27,500,000
Associated premium as a freestanding equity-linked instrument under ASC 815													12,500,000
Remaining Transaction Price Allocated To Performance Obligations													10,600,000
Pfizer License and Share Purchase Agreements [Member] | SPR206 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment received													$ 0
Issuance of common stock and preferred stock net of offering costs, shares | shares													2,362,348
Share price | $ / shares													$ 16.93
Proceeds from sale of common stock to related party													$ 40,000,000.0
Receivable amount upon achievement of certain milestone													80,000,000.0
Gates MRI [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reduction to research and development expense													1,500,000	$ 2,100,000
Savior Service Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Supervision fee amortization service period				34 months
Savior Service Agreement [Member] | Prepaid Expenses and Other Current Assets [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-refundable supervision fee related to commercial manufacturing facility				$ 2,000,000.0
Savior Service Agreement [Member] | Long-term Asset [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Service agreement additional payment related to facility build out costs													$ 5,200,000