PDCD1 and plasma cell myeloma: This Phase 1/2 trial (NCT03194867) was designed to determine whether cemiplimab (anti‐PD‐1) enhances the anti‐myeloma activity of isatuximab (anti‐CD38) in patients with relapsed and refractory multiple myeloma (RRMM), to confirm the feasibility of the combination, determine its efficacy, and further evaluate its safety.