CSB-421

CSB-421 is a preclinical radiotherapeutic (radioimmunotherapy) being developed by CytoSite Bio that targets granzyme B, a protease released by activated T cells and natural killer (NK) cells when they engage tumor cells. Unlike traditional radiopharmaceuticals that target tumor-specific antigens, CSB-421 is designed to bind to extracellular granzyme B within the tumor microenvironment, delivering localized, immunostimulatory radiation directly to sites of active immune response. In preclinical murine models, CSB-421 has demonstrated the ability to achieve complete response rates in rescuing immunotherapy non-responders while sparing healthy tissues. It is currently being investigated for the treatment of solid tumors, including melanoma and non-small cell lung cancer (NSCLC).