The Sponsor decided to discontinue development of mRNA-2736 for strategic business reasons.

This study is designed to evaluate the safety and tolerability of mRNA-2736 in participants with RRMM.

This open-label, Phase 1, dose-escalation, first-in-human (FIH) clinical study of mRNA-2736 in participants with RRMM is designed to evaluate the safety and tolerability of escalating doses of mRNA-2736, administered intravenously (IV), to determine maximum tolerated dose and/or recommended Phase 2 dose, pharmacokinetics, pharmacodynamics, and preliminary efficacy of mRNA-2736.

Key Inclusion Criteria:

• RRMM with prior exposure to a proteasome inhibitor, an immunomodulatory drug (IMiD), and an anti-cluster of differentiation (CD38) monoclonal antibody. Participants must have received at least 3 prior lines of therapy or be triple-class refractory. Participants that are intolerant of a proteasome inhibitor, IMiD, or aCD38 are eligible.

• Measurable disease defined as at least 1 of the following:

  • Serum M-protein ≥0.5 grams/deciliter
  • Urine M-protein ≥200 milligrams (mg)/24 hour
  • Involved free light chain (FLC) ≥100 mg/liter and an abnormal FLC ratio
  • Plasmacytoma with a single diameter ≥2 centimeters
  • Bone marrow plasma cells >30%

Key Exclusion Criteria:

• Known central nervous system (CNS) myeloma or clinical signs and symptoms of CNS involvement of myeloma.
• Active plasma cell leukemia, defined as peripheral blood plasma cells ≥20%. History of plasma cell leukemia is allowed.
• Radiotherapy or cytotoxic chemotherapy within 2 weeks prior to Day 1 (Baseline), except palliative radiotherapy of limited field is permissible within 2 weeks after discussion with the Sponsor medical monitor.
• Antibody-based immunotherapy (monoclonal antibody, bispecific antibody, antibody drug conjugate, radioimmunoconjugate) within 21 days prior to Day 1 (Baseline).
• Proteasome inhibitor therapy within 14 days prior to Day 1 (Baseline).
• Immunomodulatory agent therapy within 7 days of Day 1 (Baseline).
• Autologous hematopoietic cell transplant within 100 days prior to Day 1 (Baseline).
• Allogeneic hematopoietic cell transplant within 180 days prior to Day 1 (Baseline). Participants should have no evidence or ongoing treatment for acute or chronic graft versus host disease.
• Genetically modified adoptive cellular therapy (for example, chimeric antigen receptor T cell, chimeric antigen receptor natural killer) within 12 weeks prior to Day 1 (Baseline).
• Corticosteroid therapy ≥140 mg prednisone or equivalent cumulative dose within 14 days prior to Day 1 (Baseline).
• Active hepatitis B or C, or laboratory evidence for a chronic infection with hepatitis B or C at the time of screening. Participants with a past or resolved hepatitis B infection (presence of hepatitis B core antibody and absence of hepatitis B surface antigen) are eligible. Participants positive for hepatitis C virus (HCV) antibody are eligible only if negative for HCV RNA.

Note: Other inclusion and exclusion criteria may apply.