SELLAS Life Sciences Group, a development-stage biopharma company focused on cancer immunotherapies, has entered a clinical trial collaboration and supply agreement with Merck for the conduct of a combination clinical trial targeting multiple cancers. SELLAS’ Wilms tumor-1 (WT1)-targeting peptide immunotherapeutic agent, galinpepimut-S, will be administered in combination with MSD’s anti-PD-1 therapy KEYTRUDA in a Phase 1/2 trial enrolling patients in five cancer indications, including both hematologic malignancies and solid tumors.

The trials aim to determine if the administration of galinpepimut-S in combination with KEYTRUDA has the potential to demonstrate clinical activity in the presence of macroscopic disease, where monotherapy with either agent would have a more limited effect. The study is based upon the presumed immunobiologic and pharmacodynamic synergy between the two agents, whereby the negative influence of tumor microenvironment factors on the immune response is mitigated by PD-1 inhibition (by KEYTRUDA) thus allowing the patients’ own immune cells to invade and destroy cancerous growth deposits specifically sensitized against WT1 (by galinpepimut-S).

The Phase 1/2 trial will study the combination in patients with WT1-positive relapsed or refractory tumors and to explore the following cancer indications: colorectal, ovarian, small cell lung, triple-negative breast, and AML. This study will assess the efficacy and safety of the combination, comparing overall response rates and immune response markers achieved with the combination versus prespecified rates based on those seen with KEYTRUDA alone.

Galinpepimut-S is currently expected to enter a Phase III trial in patients with acute myeloid leukemia (AML) and is also in various development phases in multiple myeloma (MM) and ovarian cancer, while additional indications are expected as a monotherapy or in combination with other immuno-oncology agents.