Was Mosunetuzumab/Polatuzumab Vedotin Efficacious in LBCL Subtype?

In patients with autologous stem cell transplant-ineligible relapsed/refractory large B-cell lymphoma, mosunetuzumab-axgb (Lunsumio) in combination with polatuzumab vedotin-piiq (Polivy; M-Pola) achieved a 59% reduction in the risk of progression or death compared with rituximab (Rituxan) plus gemcitabine and oxaliplatin (R-GemOx; HR, 0.41; 95% CI, 0.28-0.61; P <.0001).

The overall response rate (ORR) was 70.3% (95% CI, 61.9%-77.8%) with M-Pola and 40.0% (95% CI, 28.5%-52.4%) with R-GemOx, and the complete response rate was 51.4% and 24.3%, respectively. The 12-month duration of complete response rate was 72.6% (95% CI, 61.4%-83.8%) vs 44.1% (95% CI, 13.2%-74.9%).

These primary results from the phase 3 SUNMO trial (NCT05171647) were most recently presented at the Society of Hematologic Oncology 2025 Annual Meeting by Adam J. Olszewski, MD, an author on the study and an associate professor of medicine at The Warren Alpert Medical School of Brown University. Following the presentation, Olszewski spoke with CancerNetwork® about the efficacy results from the trial.

Transcript:

The trial had, interestingly, a dual primary end point for both ORR and PFS. Both were accounted for statistically, and the trial was terminated early because early analysis of the ORR demonstrated statistically significant improvement. Ultimately, the trial enrollment was terminated by the data safety monitoring boards. Both ORR and the PFS were improved with M-Pola compared with R-GemOx. Most importantly, the PFS was extended from 3.8 months for R-GemOx, which, as we know, is very suboptimal, to 11.5 months [for M-Pola]. It’s tripled or more compared with the control arm. The ORR was 70% with 51% of patients attaining complete response, which is also significantly better than the 40% response rates observed with R-GemOx. Both from the point of view of response rates, complete response rates, and the PFS, the experimental regimen with M-Pola provided benefit for patients.

The primary analysis of PFS was conducted just this year, and there were not enough events for the appropriate power for the OS analysis. The final OS analysis will have to wait until there is a sufficient number of events, but at first look and without statistical testing, there appears to be an improvement in OS by about 8 points at 1 year. Also, the median OS appears to be longer [for M-Pola] than with the control arm. Right now, the HR is 0.8, but the statistical test will have to wait until more events are seen. We remain optimistic that there will be some OS improvement as well, although we have to understand that these patients, compared with some other trials, had access to CAR T cells and bispecific therapy, so demonstrating OS benefits may not be as easy as in the past.

Reference

Westin J, Zhang H, Kim W, et al. Mosunetuzumab plus polatuzumab vedotin is superior R-GemOx in transplant-ineligible patients with R/R LBCL: primary results of the phase III SUNMO trial. Presented at the Society of Hematologic Oncology 2025 Annual Meeting; September 3-6, 2025; Houston, TX. Abstract ABCL-1492.