Evaluation of IGM-2644 in Adults With Relapsed and/or Refractory Multiple Myeloma

Inclusion Criteria: * Adults \> 18 years at time of consent * ECOG performance status of 0 or 1 * Relapsed and/or refractory multiple myeloma after ≥ 3 prior lines; Must have failed treatment with an IMiD, PI, and anti-CD38 therapy * Measurable disease per the IMWG response criteria * Adequate marrow and organ function without transfusion or growth factor support within 7 days prior to screening * Willing and able to undergo bone marrow aspirate and biopsy per protocol Exclusion Criteria: * Inability to comply with study and follow-up procedures * History of clinically significant primary amyloidosis, plasma cell leukemia, Waldenstrom macroglobulinemia or myelodysplastic syndrome * Received chemotherapy, biologics, or small molecule therapy within 21 days or 5 half-lives, whichever is shorter * Use of any non-approved or investigational agent ≤ 4 weeks prior to the first dose of study drug. * Received last prior anti-CD38 monoclonal antibody treatment within 28 days before first planned dose of the study drug * Current Grade \> 1 toxicity, with the exception of Grade 2 peripheral neuropathy, alopecia, or toxicities from prior anti-tumor therapy that are considered irreversible * Large-field radiotherapy within 28 days prior to Day 1 (radiation to a single site as concurrent therapy is allowed) * Prior autologous stem cell transplant within 180 days prior to Day 1 * Prior allogeneic stem cell transplant