A Study to Evaluate the Safety, Pharmacokinetics, and Activity of XmAb24306 in Combination With Cevostamab in Participants With Relapsed/Refractory Multiple Myeloma

The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics, and activity of XmAb24306 in combination with cevostamab in participants with relapsed/refractory multiple myeloma (R/R MM) who have received a minimum of three prior treatments, including at least one immunomodulatory drug (IMiD), one proteasome inhibitor (PI), and one anti-CD38 monoclonal antibody.

Inclusion Criteria: * Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1 * Life expectancy of at least 12 weeks * Participants must have received a minimum of 3 prior lines of therapy, including at least one PI, one IMiD, and an anti-CD38 monoclonal antibody. * Documented evidence of progressive disease on or after the last prior therapy, or participants who were intolerant to the last prior therapy. * Measurable disease, as defined by the protocol * Participants agree to follow contraception or abstinence requirements as defined in the protocol Exclusion Criteria: * Any anti-cancer therapy within 3 weeks prior to initiation of study treatment with exception defined by the protocol * Participants with autologous stem cell transplantation (SCT) within 100 days prior to first dose of study treatment * Participants with prior allogeneic SCT or solid organ transplantation * Known history of hemophagocytic lymphohistiocytosis (HLH) or macrophage activation syndrome (MAS) * Active or history of autoimmune disease * Participants with current or history of Central Nervous System (CNS) disease, or current CNS involvement by Multiple Myeloma (MM) * Significant cardiovascular disease * Participants with known clinically significant liver disease * Symptomatic active pulmonary disease requiring supplemental oxygen * Known active infection requiring intravenous anti-microbial therapy within 14 days prior to first study drug administration * Any episode of active, symptomatic COVID-19 infection, or requiring treatment with IV antivirals for COVID-19 (not including COVID-19 primary prophylaxis) within 14 days, prior to first study treatment * Other protocol defined inclusion/exclusion criteria may apply