Phase 3 SUNMO Data Show Mosun-Pola Cuts Progression Risk Over R-GemOx in Large B-Cell Lymphoma: Elizabeth Budde, MD, PhD

Updated results from the phase 3 SUNMO trial presented at ASCO 2026 reinforce mosunetuzumab plus polatuzumab vedotin (Mosun-Pola) as a compelling chemotherapy-free option for patients with relapsed/refractory large B-cell lymphoma (R/R LBCL) who are ineligible for autologous stem-cell transplant (ASCT), particularly those receiving the combination as second-line therapy. Elizabeth Budde, MD, PhD, hematologist oncologist at City of Hope and coauthor of the study, explains the importance of the results in this interview with The American Journal of Managed Care^® ahead of the 2026 annual meeting of the American Society of Clinical Oncology.

Updated Efficacy at 28 Months

At a median follow-up of 28.3 months, Mosun-Pola continued to demonstrate superior progression-free survival (PFS) over R-GemOx across the full trial population (HR, 0.41; 95% CI, 0.28-0.60). The overall response rate (ORR) was 70.3% with Mosun-Pola vs 40.0% with R-GemOx.

The second-line subgroup data are particularly striking. Among the 91 patients who had received 1 prior line of therapy, including those who were primary refractory or experienced early relapse, the ORR with Mosun-Pola was 75.4% vs 36.7% with R-GemOx, and the CR rate was 60.7% vs 20.0%. The 2-year PFS rate was 40.3% ves 20.1%—effectively double—and the 2-year duration of CR estimate was 60.8% vs 37.5%. Median duration of CR was not reached in either the second line or third line+ Mosun-Pola subgroups. The PFS benefit was consistent across both second-line (HR, 0.38) and third-line+ (HR, 0.48) subgroups.

The Mechanistic Case for Combination

Budde emphasized that the 2 agents work through distinct and complementary mechanisms. Mosunetuzumab is a bispecific antibody that recruits endogenous T cells and redirects them to CD20-positive lymphoma cells. Polatuzumab vedotin is an antibody-drug conjugate (ADC) targeting CD79b that delivers a cytotoxic warhead directly into the tumor cell independent of T-cell effector function. Preclinical data suggest polatuzumab vedotin also upregulates CD20 surface expression on target cells, potentially sensitizing them to mosunetuzumab-mediated killing—a synergistic interaction rather than simple dual coverage.

Safety and Real-World Feasibility

The safety profile was unchanged from the primary analysis. Grade 2 or greater cytokine release syndrome (CRS) occurred in just 4% of Mosun-Pola patients overall, and no immune effector cell–associated neurotoxicity syndrome (ICANS) events were observed. In the second-line subgroup, grade 2 CRS occurred in 3% and no grade 3 or greater CRS events were recorded. Budde noted that Mosun-Pola carries the lowest CRS incidence among bispecific antibody-based regimens and that most CRS events are low grade, self-limited, and manageable with acetaminophen or ibuprofen in the outpatient setting.

Critically, the regimen requires no hospitalization by default. This distinguishes it from chimeric antigen receptor T-cell therapy, which is a standard option for transplant-eligible patients in second line that demands inpatient administration and carries a significantly higher CRS and ICANS risk profile.