Ambulatory teclistamab administration in patients with relapsed/refractory multiple myeloma.

11146 Background: Teclistamab (Tec) is the first B-Cell Maturation antigen (BCMA)xCD3 bispecific antibody FDA approved for the treatment of relapsed or refractory multiple myeloma (RRMM) in patients who have received ≥4 prior lines of therapy. The phase 1-2 MajesTec-1 study raised concerns for cytokine release syndrome (CRS)/immune effector cell-associated neurotoxicity syndrome (ICANS). 48-hour inpatient observation is recommended for step-up dosing, which imposes financial and logistical burdens. We report our institutional experience with ambulatory Tec administration. Methods: Our inpatient/outpatient (IPOP) hybrid nursing unit is staffed with specialized nurses, advanced practice providers, and attending physicians. Our patients treated in IPOP must live within 1 hour of the hospital and have a 24-hour caregiver. Patients were treated with the recommended step-up dosing schedule. CRS grading and ICE scoring were performed daily. Both CRS and ICANS were graded according to the ASTCT grading systems. We collected toxicities until the second full treatment dose, at which point hospitalization is no longer recommended. Results: In total, 25 patients were treated with Tec between January 2023 to December 2023. The median age was 70 years old (range 59-89), with a median of 6 prior lines of therapy. One patient was dialysis dependent prior to starting Tec. All patients were triple class refractory. Thirteen patients (52%) received prior bone marrow transplant. One (4%) patient received prior anti-BCMA CAR-T therapy. Seventeen patients (68%) required admission during the Tec ramp-up period. CRS was observed in 15 (60 %) patients, all of which were grade I/II events. Fourteen of these patients were hospitalized for CRS. They were admitted for median number of 2 hospital days (range 1-6). Tocilizumab was administered for Grade 2 CRS in 3 patients (12%). ICANS was reported in 4 (16%) patients. Two of those patients developed Grade 2 ICANS which completely resolved with dexamethasone. The median number of admitted hospital days for these patients was 3 days (range 2-49). Neutropenia with ANC < 500 was seen in only 1 (4%) patient. Grade 3/4 infections were seen in 3 (12%) patients during the ramp-up period. Conclusions: Tec administration through an inpatient/outpatient hybrid model is safe and feasible. CRS was common but low grade and short lived. ICANS was observed, but remained low grade and may be attributable to our older patient population. As our center gained experience with the Tec management, we noticed lower rates of admission for low grade CRS. Lower incidences of infections and neutropenia demonstrate that these complications emerge in the months after starting therapy. Future studies will help identify patients who are higher risk for CRS and ICANS during ramp-up treatment and may pave the way for prophylactic interventions and outpatient administration.