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Collaboration and license agreements - Narrative (Details) $ / shares in Units, $ in Thousands						1 Months Ended								3 Months Ended		6 Months Ended
	Sep. 30, 2025 USD ($)	Mar. 01, 2024 USD ($) performanceObligation target	Jan. 04, 2024 USD ($)	Dec. 11, 2023 USD ($)	May 29, 2023 USD ($) $ / shares shares	Feb. 28, 2026 USD ($)	Sep. 30, 2025 USD ($)	Apr. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2023 USD ($) target	Nov. 30, 2020 USD ($) target	Feb. 29, 2020 USD ($) protein	Dec. 31, 2018 USD ($) target performanceObligation	Jun. 30, 2026 USD ($) target performanceObligation	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($) target performanceObligation	Jun. 30, 2025 USD ($)	Apr. 08, 2026 USD ($)	Dec. 31, 2025 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of performance obligations \| performanceObligation													12
Transaction price allocated to performance obligation														$ 23,732		$ 23,732
Contract with customer, liability														40,375		40,375			$ 28,334
Proceeds from issuance of common stock from at-the-market equity offering																33,548	$ 0
Revenue recognized that was included in the contract liability at the beginning of the period														2,820	$ 6,512	6,560	$ 11,821
Discovery, Regulatory, and Commercial Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive		$ 740,000
Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Written notice period for termination of agreement					90 days
Roche Degrader-Antibody Conjugate Collaboration and License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment														20,000
Roche Degrader-Antibody Conjugate Collaboration and License Agreement \| Discovery, Regulatory, and Commercial Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive																		$ 1,000,000
Roche Degrader-Antibody Conjugate Collaboration and License Agreement \| Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Written notice period for termination of agreement		90 days
Roche DAC Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment														20,000
Contract with customer, liability														$ 17,334		$ 17,334
MKDG Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment		$ 16,000
Number of potential research and development targets \| target		2
Regulatory milestone achieved								$ 1,000
Addition to the transaction price								$ 1,000
Number of performance obligations \| performanceObligation		2												1		1
Transaction price allocated to performance obligation														$ 17,000		$ 17,000
Contract with customer, liability														2,153		2,153			3,913
MKDG Agreement \| Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Written notice period for termination of agreement		60 days
Betta Agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment	$ 10,000				$ 10,000
Regulatory milestone achieved										$ 2,000
Contract with customer, liability														14,703		14,703			$ 14,725
Number of shares issued in transaction (in shares) \| shares					5,567,928
Consideration received on transaction					$ 25,000
Price per share (in dollars per share) \| $ / shares					$ 4.49
Stock repurchase program, premium percentage					25.00%
Duration of trading day volume weighted average closing price					60 days
Trading days prior to the effective date of the Stock Purchase Agreement					2 days
Proceeds from issuance of common stock from at-the-market equity offering			$ 20,000
Premium from issuance of common stock			$ 5,000
Estimated transaction price														125,000		125,000
Transaction price from closing of the stock purchase agreement	$ 5,000
Expected consideration to be received from manufactured clinical supply														108,000		108,000
Betta Agreements \| Research and development milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive					$ 357,000
Betta Agreements \| Drug Application Approval
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive					$ 40,000
Restated Roche Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory milestone achieved									$ 2,000
Addition to the transaction price									$ 4,000
Additional upfront consideration received													$ 40,000
Number of potential targets \| target											5		6
Number of targets \| target										2	2
Annual research plan payments receivables											$ 1,000
Option exercise fees											$ 8,000
Restated Roche Agreement \| Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Written notice period for termination of agreement											90 days
Restated Roche Agreement \| Maximum \| Research, development and commercial milestone payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive											$ 273,000
Restated Roche Agreement \| Maximum \| One-time sales-based payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive											150,000
Restated Roche Agreement \| Lead series identification achievement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fees											$ 2,000
Biogen Research and License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Regulatory milestone achieved						$ 2,000	$ 2,000
Research agreement, period												54 months
Nonrefundable upfront payment												$ 45,000
Biogen Research and License Agreement \| Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of targeted protein degradation \| protein												5
Biogen Research and License Agreement \| Maximum \| Research and development milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive												$ 35,000
Biogen Research and License Agreement \| Maximum \| One-time sales-based payments
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount eligible to receive												$ 26,000
Merck Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment				$ 10,000
Restated Roche Agreement And Biogen License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Transaction price allocated to performance obligation														$ 146,600		$ 146,600
Merck, KGaA Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of remaining research and development targets \| target														1		1