Updated Phase 2 Data Show Mosunetuzumab Monotherapy Provides Durable Efficacy, Manageable Safety Profile in Relapsed/Refractory Follicular Lymphoma


Expert discusses the updated data for a trial cohort after a median follow-up of 27 months.

Pharmacy Times® interviewed Matthew J. Matasar, MD, MS, chief of blood disorders, Rutgers Cancer Institute of New Jersey and RWJBarnabas Health, on his poster presentation titled “Mosunetuzumab [Lunsumio; Genentech] 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” at the 64th American Society of Hematology (ASH) Annual Meeting and Exhibition in New Orleans, Louisiana.

Pharmacy Times®: How is mosunetuzumab used and for what patient population?

Matthew J. Matasar: So mosunetuzumab is the furthest along of the so-called bispecific antibodies. These are antibodies that target an antigen on the surface of the malignant B cell as well as traditionally CD3 on healthy native T cells, creating an immune synapse, and allowing for T cell activation, proliferation, and T cell mediated tumor killing.

Mosunetuzumab is now approved by European regulatory agencies, not yet FDA approved for the treatment of patients with relapsed or refractory follicular lymphoma. But this year at ASH, we offer updated and extended outcomes for the use of mostly monotherapy in the treatment of patients with follicular lymphoma.

Pharmacy Times®: What did the previously recorded phase 2 trial data show regarding patient response and safety profile for mosunetuzumab?

Matthew J. Matasar: We've previously established mosunetuzumab monotherapy as a highly active treatment in patients with relapsed or refractory follicular lymphoma, [with] overall response rates of approximately 80% and complete response rates of approximately 60%.

The question that has remained for us in the community, however, is what is the durability of these responses. And this is where our data at this year's ASH are the most informative, where we offer now the longest follow up to date of patients treated with mosunetuzumab monotherapy for this indication.

Importantly at a median follow up now of approximately 27 months, the median progression free survival, duration of response, and duration of complete response have not yet been reached with the 24 month medians of these all better than 50%.

Pharmacy Times®: What did the updated data in the same cohort after a median follow-up of 27 months show regarding efficacy and safety of mosunetuzumab?

Matthew J. Matasar: To clarify, the median duration of response, median duration, and complete response, even the median PFS, have not yet been reached at a median follow up of 27 months. As a way to try to get a sense for how the patients are doing, one can look at the 24 month estimates, and the 24 month PFS is just 51%. So just over half of patients have not yet had a PFS event. The median duration of response and complete response are even better with durations of complete response at 24 months, I think approximately 60%, and for duration of complete response at 24 months, approximately 80% that have achieved a CR remaining at CR at the 24 month mark.

Pharmacy Times®: How do these follow-up results compare to the previously recorded treatment response and safety profile data?

Matthew J. Matasar: What I would say is that it certainly affirms our prior perspective and perception of this drug, which is that the responses have so far seemed to be durable. The longer that we're able to follow these patients and the better we can characterize that durability, the better we'll be able to counsel our patients regarding this as an option as compared to other options in the space, including chemotherapy, other targeted therapies, and even potentially comparing it to CAR T cell therapy.

Pharmacy Times®: What are next steps following these results?

Matthew J. Matasar: So my personal expectation is that when the FDA convenes and offers an opinion that it will receive FDA approval, likely at the end of this calendar year, certainly I believe that the clinical data supporting the application is more than justifying the approval.

This of course will not be the end of mosunetuzumab’s story, and there's a lot of ongoing work to try to better develop and characterize its activity as monotherapy or in combination with other agents in number of clinical settings, both aggressive and indolent B cell lymphomas.

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