P-233 Physician Perspectives Regarding Conventional Marrow Testing and MRD Assessments to Guide Decision-Making in Myeloma

dose of to both onset and to resolution; no events were life-threatening or fatal.Neutropenia (37%) and anemia (29%) were the most common hematological AEs.Step-up dosing strategies, where a lower initial dose is given prior to the full dose, have been effectively utilized for other T-cell targeting therapeutics in myeloma as well as other diseases to lower the risk of severe CRS.The intent with this Phase 1b trial, which is currently enrolling, is to evaluate step-up dosing of ABBV-383 in Cycle 1 as a mitigation strategy for CRS.Methods: The primary objective is to assess frequency and severity of CRS in patients with RRMM treated with ABBV-383 monotherapy with step-up dosing.Primary and secondary endpoints are Grade ≥2 CRS during Cycle 1 and any CRS during the study, respectively.Secondary objectives are to assess safety and tolerability of ABBV-383 in these patients.Exploratory efficacy endpoints are clinical activity as defined by IMWG 2016 criteria, including objective response rates, time to response, duration of response, and progression-free survival.Eligible patients are aged ≥18 years with ECOG status 0-2 and RRMM with documented progression after last treatment.Patients must be BCMA-targeted therapy-naïve and have received ≥3 lines of therapy, including a proteasome inhibitor, an immunomodulatory drug, and an anti-CD38 monoclonal antibody.The study consists of 2 phases: step-up dose optimization and dose expansion.In the dose optimization phase, patients receive the stepup dose on Day 1 of treatment Cycle 1 and the target dose on Day 4 of Cycle 1.In Cycle 2 and all subsequent cycles, patients receive the target dose on Day 1. Therapy continues until disease progression, withdrawal, or discontinuation.Patients are hospitalized for 24 hours during both step-up and target dosing in Cycle 1.In the dose expansion phase, patients will receive the optimum step-up dose on Day 1 and the target dose on Day 4 of Cycle 1. Patients receive the target dose on Day 1 of subsequent cycles.This trial is currently enrolling at 34 sites in 7 countries: US, Canada, Denmark, France, Israel, Spain, and the UK.