This study will evaluate the safety, tolerability, pharmacokinetics, and activity of XmAb24306 in combination with a multiple myeloma (MM)-targeting monoclonal antibody capable of inducing antibody-dependent cellular toxicity (ADCC) in participants with relapsed or refractory (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:

• Life expectancy of at least 12 weeks
• Measurable disease, as defined by the protocol
• 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
• Best response of stable disease or better with at least one prior anti-CD38 monoclonal antibody containing line of treatment

Exclusion Criteria:

• Any anti-cancer therapy within 3 weeks prior to initiation of study treatment, with exceptions defined by the protocol
• Prior allogeneic stem cell or solid organ transplantation
• Autologous stem cell transplantation within 100 days prior to initiation of study treatment
• Significant cardiovascular disease
• Known clinically significant liver disease
• Active or history of autoimmune disease or immune deficiency
• Known active infection requiring IV anti-microbial therapy within 14 days prior to first study drug administration
• Primary or secondary plasma cell leukemia
• Current CNS involvement by MM
• Other protocol defined inclusion/exclusion criteria may apply

Qualified researchers may request access to individual patient level data through the clinical study data request platform (www.vivli.org). Further details on Roche's criteria for eligible studies are available here (https://vivli.org/ourmember/roche/). For further details on Roche's Global Policy on the Sharing of Clinical Information and how to request access to related clinical study documents, see here (https://www.roche.com/research\_and\_development/who\_we\_are\_how\_we\_work/clinical\_trials/our\_commitment\_to\_data\_sharing.htm).