DP099 | BISPECIFIC ANTIBODIES FOLLOWED BY ALLOGENEIC HEMATOPOIETIC STEM CELL TRANSPLANTATION AS RESCUE THERAPY IN REFRACTORY/RELAPSE NON-HODGKIN LYMPHOMA

Background: Allogeneic stem cell transplantation (HSCT) emerges as a consolidation option in high-risk lymphoma patients (pts) rescued with bispecific antibodies (BiAb) but data on safety and efficacy are still limited. Patients and methods: in this retrospective analysis we evaluate all consecutive HSCT performed between 01/01/2019 and 31/12/2024 after rescue with BiAbs in adult pts, age > = 18 years, affected by relapsed/refractory (RR) lymphoma at our center. Results: eight pts (4 females and 4 males) with RR lymphomas (4 DLBCL, 3 FL and 1 MCL) received HSCT after treatment with glofitamab (4 pts), mosunetuzumab (3 pts) and epcoritamab (1 pts). Median age at transplant was 58(range 42-74) years; Median time from last BiAb was 41(22-122) days and median doses of BiAb before HSCT was 8 (4-12); 6 pts had received previously CAR-T (4Tisa-cel, 2Axi-cel and 1Brexu-cel). Six pts(75%) were in complete remission (CR) at transplant. Most pts (7/8, 87%) received matched unrelated donors’ transplants with TCF (Thiotepa, cyclophosphamide and fludarabine) conditioning regimen and ATG thymoglobuline as GVHD prophylaxis (Table 1). All pts showed full and stable engrafment. Seven pts experience grade II acute GVHD involving skin in 4 pts, intestine in 3 pts and liver in 1 pts. One pts developed atypical aGVHD with central nervous system involvement concomitant to intestinal involvement. The median GVHD onset was 27 (15-46) days. Six pts achieved CR after steroid treatment while one pts progressed and died due to hepatic aGVHD refractory to steroid and ruxolitinib. Seven pts (87%) presented at least one infection until +100: 4sepsis, 2 SARS-CoV-2, 3CMV, 2pneumonia and 1cholangitis. All pts had severe hypogammaglobulinemia needing supplementation. No deaths due to infection occurred in our series. With a median follow up of 6 (3-37) months after HSCT, 87% of pts are alive while 1(12%) pts died due to acute GVHD. One pts with active MCL before transplant, relapsed 2 months after transplant. This pts rapidly suspended immunosuppressive therapy without aGVHD reactivation and is still alive after venetoclax savage therapy. Conclusions: in our experience, bridging with BiAb to HSCT in patients who failed CAR-T or target therapies allow to achieve and maintain CR in 75% of pts at a median of 6 months after transplant. HSCT is safe with only 1 NRM event and manageable early infections. Prospective multicenter studies are needed to better understand efficacy and safety of HSCT consolidation after BiAbs.