This is an open-label phase 2 study of elranatamab in combination with isatuximab administered subcutaneously in patients with relapsed and refractory multiple myeloma (RRMM) who have received at least two prior lines of therapy and who have had previous treatment with both immunomodulatory drugs (IMiDs) and a proteasome inhibitor (PI). The subcutaneous injection method of isatuximab administration, including the device used to administer isatuximab, is investigational.