Outcomes in patients with B-cell precursor acute lymphoblastic leukemia receiving inotuzumab ozogamicin stratified by body mass index.

6541 Background: Inotuzumab ozogamicin (InO) is approved for the treatment of adults for relapsed/refractory B-cell precursor acute lymphoblastic leukemia (R/R B-ALL). In previous studies, elevated body mass index (BMI) has been associated with worse outcomes in adult patients treated for ALL. We report the efficacy and safety of InO in adult patients with R/R B-ALL, stratified by BMI. Methods: Data from three previous studies, NCT01363297/B1931010 (InO: 0.8–1.8 mg/m 2 /cycle [Ph1], 1.6–1.8 mg/m 2 /cycle [Ph2]) NCT01564784/B1931022 (InO: 1.5–1.8 mg/m 2 /cycle) and, NCT03677596/B1931030 (InO: 0.9–1.2mg/m 2 or 1.5–1.8mg/m 2 per cycle) were pooled, participants (pts) were grouped by formal BMI definitions: <25 kg/m 2 (healthy), 25–30 kg/m 2 (overweight) and >30 kg/m 2 (obese). Data presented as descriptive statistics only. A genAI tool was used with author review to develop the first draft (8 Jan 2025; Pfizer; GPT-4o); authors take full responsibility for the content. Results: Data from 338 pts (18–79 years; median age 44, 41% female) were analyzed, with 155 pts in the <25 kg/m 2 group, 116 pts in the 25–30 kg/m 2 group and 67 pts in the >30 kg/m 2 group. Across the <25, 25–30 and >30 kg/m 2 BMI groups, CR/CRi was achieved in 108 (70%), 88 (76%) and 46 (69%) of pts, and MRD negativity observed in 87 (56%), 73 (63%) and 35 (52%) of pts, respectively. At 24 months, the probability of progression-free survival (95% CI) was 19.9% (13.2, 27.5), 12.8% (7.2, 20.1) and 10.9% (4.2, 21.1), and the probability of survival (95% CI) was 28.1% (21.0, 35.6), 22.1% (14.8, 30.3) and 17.5% (9.2, 27.8) in the <25, 25–30 and >30 kg/m 2 BMI groups, respectively. Most pts experienced TEAEs, and incidence was similar across BMI groups (97%–99%). Common hepatic Grade ≥3 TEAEs were sinusoidal obstruction syndrome (SOS) (10 %, <25 kg/m 2 ; 6%, 25–30 kg/m 2 ; 9%, >30 kg/m 2 ) and GGT increase (7 %, <25 kg/m 2 ; 5%, 25–30 kg/m 2 ; 5%, >30 kg/m 2 ). Overall, 143 pts (42%) proceeded to hematopoietic stem cell transplantation (HSCT) after InO treatment, sixty-seven (43%) in the <25 kg/m 2 group, 49 (42%) in the 25–30 kg/m 2 group, and 27 (40%) in the >30 kg/m 2 group. Post-HSCT, non-relapse mortality within 100 days was estimated to be 22% in the <25 kg/m 2 group, 22% in the 25–30 kg/m 2 group and 19% in the >30 kg/m 2 group. Post-HSCT SOS was observed in 18 pts (27%) in the <25 kg/m 2 group, 7 pts (14%) in the 25–30 kg/m 2 group and 6 pts (22%) in the >30 kg/m 2 group, with grade 3–4 SOS observed in 10 (15%), 7 (14%) and 5 pts (19%), respectively. Conclusions: In this pooled analysis of pts treated with InO for R/R B-ALL, efficacy and safety outcomes were broadly consistent across BMI groups. However, lower PFS and OS rates at 24 months were noted in pts with higher BMI. Summary of outcomes. % <25 kg/m 2 (N=155) 25–30 kg/m 2 (N=116) >30 kg/m 2 (N=67) CR/CRi 70 76 69 CR 33 36 40 CRi 37 40 28 MRD-negativity 56 63 52 PFS (24 months) 20 13 11 OS (24 months) 28 22 18