A Phase 1, First-in-Human, Dose Escalation and Expansion, Multicenter Study of XMT-2056 in Participants with Advanced/Recurrent Solid Tumors that Express HER2

The purpose of the study is to: During the Dose Escalation part, find the most tolerated dose of the Study Drug that may provide potential benefit. During the Enrichment and Expansion parts, further study of the Study Drug to ensure that it can be tolerated and is reasonably safe. Collect more information on how participants respond to receiving the Study Drug. See how long the Study Drug stays in your blood and if the Study Drug causes any changes in your body and at what dose these changes happen. For example, does your body develop proteins (e.g., antibodies) that work against the Study Drug or does your tumor size change after receiving the Study Drug? Explore whether the amount of HER2 expressed on tumor cells or other features of the participant’s cancer or immune system can predict how well the Study Drug works.