Massachusetts-based clinical-stage biopharmaceutical company Mersana Therapeutics, has partnered with pharma giant GlaxoSmithKline (GSK) to co-develop its antibody drug conjugate (ADC), XMT-2026.  

The selected drug candidate, XMT-2026, was discovered using Mersana’s Immunosynthe platform and designed to treat HER2 (human epidermal growth factor receptor 2) which is a protein that promotes cancer growth. Mersana plans to initiate a phase 1 clinical trial of XMT-2026 to treat breast, gastric, and non-small-cell lung cancers. In May 2022, FDA granted orphan drug designation to XMT-2026 to treat gastric cancer. 

Under the terms of the collaboration, Mersana received USD 100 million upfront cash payment. Upon exercising the option, the drug will be added to GSK’s portfolio of drugs under ADC. In addition, Mersana is eligible to receive upto USD 1.36 billion in milestone payments if GSK exercises its option to commercialize the drug. If commercialized, Mersana has retained options to profit-share and co-promote in the US. When it is exercised, Mersana is eligible to receive tiered royalties on net sales outside the US. If not exercised, it is eligible to receive double-digit tiered royalties of global net sales. 

Mersana Therapeutics uses its proprietary ADC platforms to discover and develop novel ADCs to treat cancer. Mersana’s lead product candidate upifitamab rilsodotin (UpRi) is undergoing trials to treat ovarian cancer. It has four other ADC programs and multiple undisclosed programs in the pipeline. Further, multiple partners are using Mersana’s platforms to advance their ADC pipelines.