Subsequent Events	12 Months Ended
Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	16. Subsequent Events In January 2024, the board of directors approved a reduction in the Company's workforce by approximately 95% of the Company's current employee base in order to reduce costs and preserve capital in light of the announcement on December 22, 2023 that the Company is discontinuing its three global Phase 3 posoleucel studies. This workforce reduction will take place primarily during the first quarter of 2024 and expected to be substantially completed by April 15, 2024. As a result of these actions, the Company expects to incur personnel-related restructuring charges, excluding bonuses accrued as of December 31, 2023, of approximately $10 million in connection with one-time employee termination cash expenditures, including severance and other benefits. The Company had previously granted certain of the terminated employees restricted stock units (“RSUs”) that vest in annual installments based on continued service to the Company, as well as options to purchase shares of the Company’s common stock that typically vest over a period of four years. In connection with the reduction in workforce, the Company agreed to accelerate the vesting of a portion of the RSUs that were unvested as of the employees’ termination dates. In February 2024, the Company entered into a new SOW ("2024 SOW under the DMS Agreement") that terminated the 2022 SOW under the DMS Agreement with a third-party supplier (see Note 5), resulting in a decrease in lease payments of $5.7 million in 2024. In Q1 2024, the Company paid all remaining lease obligations of $2.9 million.

Subsequent Events

12 Months Ended

Dec. 31, 2023

16. Subsequent Events

In January 2024, the board of directors approved a reduction in the Company's workforce by approximately 95% of the Company's current employee base in order to reduce costs and preserve capital in light of the announcement on December 22, 2023 that the Company is discontinuing its three global Phase 3 posoleucel studies. This workforce reduction will take place primarily during the first quarter of 2024 and expected to be substantially completed by April 15, 2024. As a result of these actions, the Company expects to incur personnel-related restructuring charges, excluding bonuses accrued as of December 31, 2023, of approximately $10 million in connection with one-time employee termination cash expenditures, including severance and other benefits. The Company had previously granted certain of the terminated employees restricted stock units (“RSUs”) that vest in annual installments based on continued service to the Company, as well as options to purchase shares of the Company’s common stock that typically vest over a period of four years. In connection with the reduction in workforce, the Company agreed to accelerate the vesting of a portion of the RSUs that were unvested as of the employees’ termination dates.

In February 2024, the Company entered into a new SOW ("2024 SOW under the DMS Agreement") that terminated the 2022 SOW under the DMS Agreement with a third-party supplier (see Note 5), resulting in a decrease in lease payments of $5.7 million in 2024. In Q1 2024, the Company paid all remaining lease obligations of $2.9 million.