Collaboration and license agreements - Narrative (Details)		1 Months Ended					3 Months Ended		9 Months Ended		40 Months Ended
	May 29, 2023 USD ($) $ / shares shares	Aug. 31, 2021 USD ($)	Nov. 30, 2020 USD ($) target	Feb. 29, 2020 USD ($) protein	Dec. 31, 2018 USD ($) performanceObligation target	Mar. 31, 2017 USD ($)	Sep. 30, 2023 USD ($) target performanceObligation	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) performanceObligation target	Sep. 30, 2022 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2022 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of performance obligations | performanceObligation					12
Transaction price							$ 28,047,000		$ 28,047,000			$ 33,513,000
Revenue from collaboration agreements							11,072,000	$ 6,754,000	17,495,000	$ 28,242,000
Revenue recognized that was included in the contract liability at the beginning of the period							11,028,000	$ 5,517,000	16,923,000	$ 24,005,000
Transaction price allocated to performance obligation							67,906,000		$ 67,906,000
Foreign Tax Authority
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payments for tax withholdings							$ 1,000,000
Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Written notice period for termination of agreement	90 days
Restated Roche Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional upfront consideration received					$ 40,000,000
Number of potential targets | target			5		6
Number of targets | target							3		3
Annual research plan payments receivables			$ 1,000,000
Annual research plan payments periods			3 years
Restated Roche Agreement | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise fees			$ 7,000,000
Written notice period for termination of agreement									90 days
Restated Roche Agreement | Minimum | Research, development and commercial milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive			260,000,000
Restated Roche Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise fees			12,000,000
Option exercise fees, through Phase 1 trials			20,000,000
Restated Roche Agreement | Maximum | Research, development and commercial milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive			275,000,000
Restated Roche Agreement | Maximum | One-time sales-based payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive			150,000,000
Restated Roche Agreement | Lead Series Identification Achievement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fees			2,000,000
Restated Roche Agreement | Good Laboratory Practice (“GLP”) Toxicology (“Tox”) Study Phase
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fees			$ 3,000,000
Betta Agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	$ 10,000,000						$ 10,000,000
Number of shares authorized to be repurchased | shares	5,567,928
Stock repurchase program, authorized amount	$ 25,000,000
Share price (in dollars per share) | $ / shares	$ 4.49
Stock Repurchase Program, Premium Percentage	25.00%
Transaction price							10,000,000		$ 10,000,000
Revenue from collaboration agreements							$ 0		$ 0
Betta Agreements | Research and development milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive	$ 357,000,000
Betta Agreements | Drug Application Approval
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive	$ 40,000,000
Biogen License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targets | performanceObligation							5		5
Research agreement, period				54 months
Nonrefundable upfront payment				$ 45,000,000
Number of performance obligation | performanceObligation							1		1
Number of additional targets | target									2
Biogen License Agreement | Research and development services
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized that was included in the contract liability at the beginning of the period									$ 55,000,000
Transaction price allocated to performance obligation							$ 3,700,000		3,700,000
Biogen License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targeted protein degradation | protein				5
Biogen License Agreement | Maximum | Research and development milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received				$ 35,000,000
Biogen License Agreement | Maximum | One-time sales-based payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received				$ 26,000,000
Calico License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment											$ 5,000,000
Research term						5 years
Amount payable for extend research term option		$ 1,000,000
Research extend term		1 year
Annual payments											$ 5,000,000
Calico License Agreement | Research and development services
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized that was included in the contract liability at the beginning of the period									13,000,000
Calico License Agreement | Maximum | One-time sales-based payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received						$ 65,000,000
Calico License Agreement | Maximum | Potential research, development and commercial milestone payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment received						$ 132,000,000
Restated Roche Agreement And Biogen License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price allocated to performance obligation							$ 33,100,000		$ 33,100,000