Mosunetuzumab plus polatuzumab vedotin (Mosun-Pola) versus rituximab, gemcitabine and oxaliplatin (R-GemOx) in patients with relapsed/refractory large B-cell lymphoma (R/R LBCL): Updated efficacy and safety from the phase 3 SUNMO study including in second-line (2L) versus third-line plus (3L+) patient subgroups.

7007 Background: At the primary analysis, Mosun-Pola demonstrated superior efficacy versus R-GemOx, with infrequent cytokine release syndrome (CRS) events and manageable safety in patients (pts) with R/R LBCL in the Phase 3 SUNMO trial (NCT05171647; Budde et al. 2025). We report updated efficacy and safety, including in the 2L setting. Methods: Pts with R/R LBCL ineligible for autologous stem-cell transplant (ASCT) were randomized 2:1 to Mosun (subcutaneous)-Pola or R-GemOx. Dual primary endpoints were IRC-assessed progression-free survival (PFS) and objective response rate (ORR); secondary endpoints included complete response (CR) rate, duration of response (DOR), duration of CR (DOCR), and safety. Overall survival (OS) was not assessed as the data cut-off was prior to the pre-defined final OS analysis. Results: At data cut-off (August 8, 2025), 138 and 70 pts were assigned to Mosun-Pola or R-GemOx, respectively. Overall, 91 pts had 1 prior line of therapy (LOT; 2L; Mosun-Pola, n=61; R-GemOx, n=30) and 117 had ≥2 prior LOT (3L+; Mosun-Pola, n=77; R-GemOx, n=40). With a median follow-up of 28.3 months (mos), Mosun-Pola continued to demonstrate superior PFS benefits over R-GemOx (HR, 0.41; 95% CI: 0.28–0.60; Table). ORRs with Mosun-Pola were 70.3% vs 40.0% with R-GemOx. The observed PFS benefit of Mosun-Pola over R-GemOx was similar in 2L (HR, 0.38; 95% CI: 0.22–0.67) and 3L+ (HR, 0.48; 95% CI: 0.29–0.81) subgroups. With Mosun-Pola vs R-GemOx in 2L, the 2-year PFS rates were 40.3% vs 20.1%, and the 2-year DOCR estimates were 60.8% vs 37.5%, respectively. Median DOCR was not reached with Mosun-Pola in 2L and 3L+ subgroups. ORRs with Mosun-Pola vs R-GemOx were 75.4% vs 36.7% in 2L pts, and 66.2% vs 42.5% in 3L+ pts, respectively. The safety profile was unchanged since the primary analysis. Grade (Gr) ≥2 CRS occurred in 4% of Mosun-Pola-treated pts and no ICANS events occurred. The safety profile was consistent in 2L pts: Gr 2 CRS occurred in 3% of Mosun-Pola-treated pts, with no Gr ≥3 CRS events. Conclusions: Mosun-Pola continues to show notable efficacy with manageable safety in pts with ASCT-ineligible R/R LBCL, particularly in the 2L setting. Clinical trial information: NCT05171647 . Mos (95% CI), unless stated Mosun-Pola (n=138) R-GemOx (n=70) 2L Mosun-Pola (n=61) 2L R-GemOx (n=30) 3L+ Mosun-Pola (n=77) 3L+ R-GemOx (n=40) Median PFS 11.6 (5.6–17.6) 3.8 (2.9–4.1) 17.6 (5.6–NE) 3.6 (2.1–5.3) 8.6 (4.0–16.2) 3.9 (2.1–5.6) Median DOR 18.8 (11.5–NE) 6.0 (3.7–23.9) 18.8 (11.3–NE) 6.0 (3.9–NE) 21.5 (9.5–NE) 5.4 (2.3–18.3) CR, % (95% CI) 51.4 (42.8–60.0) 24.3 (14.8–36.0) 60.7 (47.3–72.9) 20.0 (7.7–38.6) 44.2 (32.8–55.9) 27.5 (14.6–43.9) Median DOCR NE 18.3 (3.9–NE) NE (15.6–NE) 21.4 (3.9–NE) NE (21.5–NE) 7.5 (2.3–NE) NE, not estimable.