Updates on the Safety, Efficacy of Mosunetuzumab Therapy for Patients With R/R Follicular Lymphoma

Matthew Matasar, MD, Rutgers Cancer Institute of New Jersey, New Brunswick, New Jersey, shares updated results from a pivotal phase 2 study on the efficacy and safety of mosunetuzumab monotherapy among patients with relapsed/refractory (R/R) follicular lymphoma (FL). 

Transcript: 

I'm Dr. Matt Matasar. I'm the chief of blood disorders here at Rutgers Cancer Institute of New Jersey, and it's my pleasure day to talk to you about our updates for mosunetuzumab monotherapy in the treatment of patients with multiple relapsed or refractory follicular lymphoma.

We recently expanded and updated our results for mosunetuzumab monotherapy, a treatment that has since achieved FDA approval for this indication, demonstrating ongoing results in terms of efficacy and durability of mosunetuzumab monotherapy.

As a reminder, we treated 90 patients with relapsed or refractory follicular lymphoma in the third line or beyond with Mosun monotherapy, given in a step-up dosing and then continued on an every 3-week basis until up to 8 cycles, at which point patients in a complete response (CR) discontinued treatment, whereas patients enjoying ongoing clinical benefit but not yet having achieved a CR went on to complete a total of 17 cycles, still fixed duration therapy.

We've seen that the results continue to be very positive for this treatment approach. Complete response rates of approximately 60%, [and] overall response rates of approximately 80%, but we're gaining greater insight into the duration of response. And now with over 2 years of follow-up, we're seeing that the median duration of response has not yet been reached with the median progression-free survival approximately 24 months.

Interestingly, we performed an analysis looking at the response to mosunetuzumab compared to the immediately preceding line of therapy. It's long been recognized that for patients with follicular lymphoma, typically with each subsequent line of therapy responses are inferior, both in terms of overall response rate and duration of response, each time going back to the well getting inferior results regardless of the treatment associated.

Here, however, with mosunetuzumab, we've seen that pattern reverse, and the duration of response and duration of complete response far exceeded that of the previous line of therapy, regardless of what that treatment was. Again, affirming that mosunetuzumab treatment really does have the opportunity and potential to change the anticipated natural history of multiple relapsed follicular lymphoma.

Encouragingly, we see no new safety signals, and the majority of cytokine release [syndrome] really was grade 1 in severity, with very few cases of grade 2, and no new grade 3 plus cases, or no new fatal or grade 5 serious adverse events recorded in this study.

In summary, I would say that the maturing of the data from GO29781, the pivotal study of mosunetuzumab monotherapy in patients with relapsed or refractory follicular lymphoma, affirms our previous understanding that mosun[etuzumab] monotherapy is safe and effective in this patient population.

The more we learn about the durability of these responses, the more encouraged I am in our understanding of mosun[etuzumab] as an appropriate treatment for these high-risk patients. Thank you for your attention today.

Source: 

Bartlett N, Sehn L, Matasar M, et al. Mosunetuzumab monotherapy demonstrates durable efficacy with a manageable safety profile in patients with relapsed/refractory follicular lymphoma who received ≥2 prior therapies: updated results from a pivotal phase II study. HemaSphere 2023; doi: 10.1016/S2152-2650(23)01361-7