Mersana is advancing a robust pipeline of immunoconjugate therapies with the potential to radically improve patients’ lives by increasing survival and quality of life for broader populations of patients in multiple cancers.
XMT-1522, Mersana’s first pipeline product, defines a new class of HER2-targeted therapies. XMT-1522 is based on our Dolaflexin platform and armed with about 15 auristatin molecules per antibody, making it highly potent in tumor models that express relatively low amounts of the HER2 protein. In a model representing HER2 1+ gastric cancer, XMT-1522 achieves complete, durable tumor regressions where ado-trastuzumab emtansine, an antibody drug conjugate approved to treat HER2-positive metastatic breast cancer, is inactive at a 15-fold higher dose. XMT-1522 has the potential to extend HER2-targeted therapy beyond the current “HER2-positive” population into patients with lower levels of HER2 expression.
Mersana discovered the novel human anti-HER2 antibody used in XMT-1522 in collaboration with Adimab. The antibody was optimized to deliver the cytotoxic payload and binds to a unique epitope in the HER2 extracellular domain. XMT-1522 therefore has the potential to be used in combination with approved cancer treatments trastuzumab and/or pertuzumab in patients with HER2-driven tumors to efficiently deliver the cytotoxic payload and inhibit HER2 signaling.
XMT-1522 IND has been accepted by the FDA. Human clinical trials are underway.