An open-label, multicenter, dose escalation study to evaluate the safety, tolerability and PK/pharmacodynamics of AO-176 in adults with relapsed/refractory multiple myeloma whose disease has progressed following at least 3 prior systemic lines of treatment and must have progressed on the final line of therapy received before being considered for this study. The study will be conducted in 2 phases; Phase 1 is an ascending-dose study of AO-176 monotherapy utilizing the classic 3+3 design, with enrollment of 3 patients per cohort and expansion of the cohort in the event of a dose-limiting toxicity (DLT). Following the dose escalation portion and determination of the monotherapy recommended phase 2 dose (RP2D), an ascending dose escalation study of AO-176 and dexamethasone combined with bortezomib will be evaluated utilizing the same 3+3 dose escalation design. Phase 2 will evaluate the clinical activity of AO-176 plus dexamethasone and bortezomib at the RP2D as determined in Phase 1 Part 2.