VA-613

VA-613 is a dual-payload antibody-drug conjugate (ADC) being developed by Sutro Biopharma in collaboration with Velo-CT. It is engineered using Sutro's proprietary XpressCF cell-free protein synthesis platform, which enables the site-specific conjugation of two distinct cytotoxic payloads to a single antibody. VA-613 targets CD70 (also known as TNFSF7), a cell surface antigen that is highly expressed in various malignancies, including renal cell carcinoma (RCC), certain lymphomas, and other solid tumors, while maintaining restricted expression in normal tissues. By delivering two distinct payloads—typically a microtubule inhibitor and a DNA-damaging agent—VA-613 is designed to maximize tumor cell killing and reduce the potential for the development of drug resistance. As of late 2025, the program is in the preclinical stage of development.