Subsequent events	12 Months Ended
Subsequent events	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent events	Subsequent events Regeneron Transaction On January 29, 2024, the Company entered into an asset purchase agreement (the “Purchase Agreement”) with Regeneron. Subject to the terms and conditions of the Purchase Agreement, the Company has agreed to sell to Regeneron (the “Asset Sale”) substantially all of the assets related to its solid tumor and other oncology and autoimmune cell therapy programs (collectively, the “Programs” and such assets, the “Transferred Assets”). Pursuant to the Purchase Agreement, in consideration for the Transferred Assets, at the closing of the Asset Sale (the “Closing”), which is expected in the first half of 2024, Regeneron will make an upfront payment to the Company of $5.0 million in cash and also assume certain liabilities of the Company arising after Closing, including liabilities related to the conduct of the Programs, under transferred contracts and with respect to certain of the Company’s employees (collectively, the “Assumed Liabilities”). Regeneron also agreed to sublease the Company’s facilities in Seattle, Washington and a portion of the Company’s facilities in Cambridge, Massachusetts. In addition to the upfront consideration, Regeneron has agreed to pay the Company a one-time $10.0 million milestone payment upon receipt of regulatory approval for the first product candidate within the Transferred Assets in certain specified countries and agreed-upon royalty payments based on net sales of the product candidates if commercialized. The Purchase Agreement contains customary representations, warranties and covenants of each of the Company and Regeneron. The Purchase Agreement further provides that, subject to certain limitations, the Company and Regeneron will each indemnify the other for certain losses arising from such breaches of representations, warranties and covenants and liabilities allocated to such party pursuant to the terms of the Purchase Agreement. Effective as of the Closing, the Regeneron Collaboration Agreement will terminate. The Closing is subject to customary closing conditions, including, among others: (a) the absence of laws enjoining, making illegal or otherwise prohibiting the Asset Sale; (b) the accuracy of the other party’s representations and warranties, subject to certain customary materiality standards; (c) compliance in all material respects by the other party with its obligations under the Purchase Agreement; and (d) no Material Adverse Effect (as defined in the Purchase Agreement) having occurred with respect to the Transferred Assets and Assumed Liabilities, taken as a whole, since the date of the Purchase Agreement. Upon the Closing, the parties will enter into certain ancillary agreements, including a transition services agreement, a license agreement and sublease agreements for the Company’s facilities as described above. Corporate Restructuring The Board approved a strategic realignment and workforce reduction of approximately 14% on January 29, 2024 in connection with the Asset Sale. The workforce reduction is expected to be substantially complete by the end of the second quarter of 2024. In connection with the workforce reduction and restructuring, the Company expects to incur one-time cash costs of approximately $8.0 million to $10.0 million, primarily in the first half of 2024, relating to severance and retention packages and related benefits. Non-cash expenses associated with the restructuring are not yet estimable. The estimates of non-cash expenses and cash costs that the Company expects to incur, and the timing thereof, are subject to a number of assumptions and actual results may differ. The Company may also incur additional costs not currently contemplated due to events that may occur as a result of, or that are associated with, the actions described above.