C064 | REAL-WORLD EXPERIENCE OF BISPECIFIC ANTIBODIES FOR RELAPSED/REFRACTORY MULTIPLE MYELOMA: SAFETY, EFFICACY AND OUTPATIENT STEP-UP DOSING ADMINISTRATION

Three approved bispecific antibodies (BsAbs), targeting BCMA (teclistamab, Tec, and elranatamab, Elra) or GPRC5D (talquetamab, Tal), represent the new standard-of-care (SOC) for triple-class exposed (TCE) relapsed/refractory multiple myeloma (RRMM). As BsAbs use increases, real-world (RW) safety and efficacy data are fundamental. Also, exploring outpatient step-up dosing (SUD) administration could increase accessibility. To this aim, we report RW data on SOC BsAbs from our Institution (since 2022), with outpatient SUD administration applied in selected patients (pts) from October 2023. The total cohort comprised 27 pts, including 7 pts who received Tec, 8 Tal and 12 Elra. Overall, 11 (41%) pts (Tec/Tal/Elra: 1/3/7) initiated SUD on outpatient setting. All pts received premedication per label recommendation. Also, 1 out of 11 pts treated outpatient received prophylactic tocilizumab, while the other 10 received dexamethasone 20 mg as post-medication after each SUD (3 pts) or after SUD and first full dose (7 pts) to reduce the risk of severe cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS). Median age was 70 (range 49-80) years, median number of prior lines of therapy was 5 (range 3-11), and 26 (96%) pts had triple-class refractory MM. The median follow-up was 5.6 (range 0.7-30.1) months (17.4/17.5/2.7 months for Tec/Tal/Elra). CRS was observed in 20 (74%) pts (Tec/Tal/Elra: 71/75/82%), 19 events were grade 1 and 1 was grade 2. Patients who received outpatient SUD had similar CRS incidence as inpatients (73% vs 75%), as well as the need for treatment with tocilizumab and/or steroids (27% vs 25%). None of the pts treated outpatient required hospitalization for CRS and all events were grade 1. ICANS was observed in only 2 (7%) pts, both treated inpatient (1 Tec and 1 Elra), 1 event was grade 1 and 1 grade 2. At least 1 infection was observed in 19 (70%) pts, and 5 (18.5%) pts experienced grade ≥3 infections. 18 (67%) pts showed hypogammaglobulinemia and received Immunoglobulins replacement. Among the 8 pts who received Tal, skin and/or nail toxicity has been reported in 6 (75%) pts, while dysgeusia in 5 (62.5%). The overall response rate was 88%, and the complete or better response rate was 56%. The 5.6-month progression-free survival rate was 89%. Overall, our RW data confirm the safety and good efficacy of BsAbs in TCE RRMM and support SUD outpatient administration as a safe and feasible option for selected pts.