Organization and Description of Business	6 Months Ended
Jun. 30, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Instil Bio, Inc. (the “Company”) is a clinical-stage biopharmaceutical company focused on developing a pipeline of novel therapies. The Company is advancing the development of its lead product candidate, AXN-2510/IMM2510, a bispecific antibody targeting both programmed death-ligand 1 (“PD-L1”) and vascular endothelial growth factor (“VEGF”) in solid tumor cancers, and seeks to in-license or acquire and develop additional novel therapeutic candidates in diseases with significant unmet medical need. In August 2024, the Company’s wholly owned subsidiary, Axion Bio, Inc. (“Axion Bio”), in-licensed certain bispecific antibodies, including AXN-2510/IMM2510 and AXN-27M/IMM27M, a monoclonal antibody targeting cytotoxic T-lymphocyte associated antigen 4 (“CTLA-4”), from ImmuneOnco Biopharmaceuticals (Shanghai) Inc. (“ImmuneOnco”). AXN-2510/IMM2510, the lead in-licensed product candidate, is a novel and differentiated PD-L1xVEGF bispecific antibody in development for the treatment of multiple solid tumor cancers. Pursuant to the license and collaboration agreement with ImmuneOnco (the “IO Collaboration Agreement”), Axion Bio has an exclusive license to research, develop, manufacture and commercialize these product candidates globally, including in the United States, Europe and Japan, excluding mainland China, Hong Kong, Macau and Taiwan (“Greater China”). ImmuneOnco retains development and commercialization rights in Greater China.

Organization and Description of Business

6 Months Ended

Jun. 30, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization and Description of Business

Instil Bio, Inc. (the “Company”) is a clinical-stage biopharmaceutical company focused on developing a pipeline of novel therapies. The Company is advancing the development of its lead product candidate, AXN-2510/IMM2510, a bispecific antibody targeting both programmed death-ligand 1 (“PD-L1”) and vascular endothelial growth factor (“VEGF”) in solid tumor cancers, and seeks to in-license or acquire and develop additional novel therapeutic candidates in diseases with significant unmet medical need.

In August 2024, the Company’s wholly owned subsidiary, Axion Bio, Inc. (“Axion Bio”), in-licensed certain bispecific antibodies, including AXN-2510/IMM2510 and AXN-27M/IMM27M, a monoclonal antibody targeting cytotoxic T-lymphocyte associated antigen 4 (“CTLA-4”), from ImmuneOnco Biopharmaceuticals (Shanghai) Inc. (“ImmuneOnco”). AXN-2510/IMM2510, the lead in-licensed product candidate, is a novel and differentiated PD-L1xVEGF bispecific antibody in development for the treatment of multiple solid tumor cancers. Pursuant to the license and collaboration agreement with ImmuneOnco (the “IO Collaboration Agreement”), Axion Bio has an exclusive license to research, develop, manufacture and commercialize these product candidates globally, including in the United States, Europe and Japan, excluding mainland China, Hong Kong, Macau and Taiwan (“Greater China”). ImmuneOnco retains development and commercialization rights in Greater China.