XMT-1522

XMT-1522 is an investigational antibody-drug conjugate (ADC) designed to target tumors expressing the human epidermal growth factor receptor 2 (HER2). It consists of a novel anti-HER2 monoclonal antibody conjugated via Mersana Therapeutics’ Fleximer/Dolaflexin platform to approximately 10–15 molecules of a proprietary auristatin payload (AF-HPA), a tubulin inhibitor. The design enables effective tumor cell killing even in cancers with low HER2 expression, potentially overcoming resistance seen with other HER2-targeted therapies such as trastuzumab emtansine (T-DM1). Preclinical and early clinical studies have shown activity in breast cancer, gastric cancer, and non-small cell lung cancer models, including those resistant to existing HER2-targeted agents[1][3][7][8].