Phase 1/2 Study of REGN5458 in Patients With Relapsed or Refractory Multiple Myeloma

Key Inclusion Criteria:

Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1
Confirmed diagnosis of active Multiple Myeloma (MM) by International Myeloma Working Group (IMWG) diagnostic criteria
Patients must have myeloma that is response-evaluable according to the 2016 IMWG response criteria as defined in the protocol.

Phase 1 Dose Escalation: Patients with MM who have exhausted all therapeutic options that are expected to provide meaningful clinical benefit, either through disease relapse, treatment refractory disease or intolerance of the therapy and including either:

Progression on or after at least 3 lines of therapy, or intolerance of therapy, including a proteasome inhibitor, an Immunomodulatory agent (IMiD), and an anti-CD38 antibody, OR
Progression on or after an anti-CD38 antibody and have disease that is "double refractory" to a proteasome inhibitor and an IMiD, or intolerance of therapy. The anti-CD38 antibody may have been administered alone or in combination with another agent such as a proteasome inhibitor (PI). Refractory disease is defined as lack of response or relapse within 60 days of last treatment.

Phase 2:

Progression on or after at least 3 prior lines of therapy including a(n) PI, IMiD, and anti-CD38 antibody, OR
Patients must be triple-refractory, defined as being refractory to prior treatment with at least 1 anti-CD38 antibody, a proteasome inhibitor, and an IMiD.

Refractory disease is defined as progression during treatment or within 60 days after completion of therapy, or less than 25% response to therapy.

Key Exclusion Criteria:

Diagnosis of plasma cell leukemia, primary systemic light-chain amyloidosis, (excluding myeloma-associated amyloidosis), Waldenström macroglobulinemia (lymphoplasmacytic lymphoma), or POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes)
Patients with known MM brain lesions or meningeal involvement
Cardiac ejection fraction <40% by echocardiogram or multi-gated acquisition scan (MUGA)
Prior treatment with BCMA-directed immunotherapies, including BCMA bispecific antibodies and BiTEs, and BCMA CAR T cells. Note: BCMA antibody-drug conjugates are not excluded
History of allogeneic stem cell transplantation at any time, or autologous stem cell transplantation within 12 weeks of the start of study treatment

Note: Other protocol defined inclusion / exclusion criteria apply