According to updated results from the phase 2 Morningsun study, frontline subcutaneous (SC) treatment with fixed-duration mosunetuzumab for patients with low-tumor burden follicular lymphoma (FL) demonstrated efficacy and manageable safety.

These results were presented by John Burke, MD, SCRI at Rocky Mountain Cancer Centers, The US Oncology Network, Aurora, Colorado, at the 66^th ASH Annual Meeting in San Diego, California.

“Mosun SC monotherapy shows encouraging high efficacy as a fixed-duration treatment in first-line low-tumor burden FL. A manageable safety profile was reported, supporting ease of access for patients with drug administration in outpatient settings.”

“Longer follow-up is needed to confirm long-term durability of response and safety,” they added.

Trancript:

I'm John Burke from Rocky Mountain Cancer Centers in Denver, Colorado and I'm a member of the Lymphoma Research Committee of Sarah Cannon Research Institute, talking about the trial of that we did of mosunetuzumab.

What we reported at the ASH meeting this year was a subset of the entire study, that study is what we call a basket study that looked at administration of mosunetuzumab subcutaneously in patients with a variety of B cell lymphomas that had not previously been studied specifically with mosunetuzumab. Current FDA approval for mosunetuzumab is for intravenous administration in patients with follicular lymphoma who've received at least 2 prior therapies and so we were looking at the subcutaneous administration of mosunetuzumab.

And the group that we reported at this meeting is those with follicular lymphoma who had a low tumor burden, meaning they did not have big bulky disease. These are patients who the standard of care is either watchful waiting which most people feel is what's recommended for these folks or those who are not comfortable with the watchful waiting approach to treat them with rituximab, but not to go with say a more intensive chemoimmunotherapy that we might use in somebody with high tumor burden disease that's causing them more problems. And we were interested in investigating the efficacy and safety of mosunetuzumab in this patient population.

We treated about 100 patients, sorry it was about 84 patients, with mosunetuzumab are what we reported here. About 50 of them were treated in community sites, about 30 or so were treated in academic sites and the treatment was administered as an outpatient, hospitalization was not required. Monitoring for cytokine release syndrome was all performed as an outpatient.

In terms of efficacy results, we found a very high level of efficacy. That is the overall response rate was above 90% and the complete response rate also very high, almost all responses were complete and so the efficacy of the product was very high in these patients.

In terms of safety, we feel that the product is reasonably safe, toxicities that we're seeing included injection site reactions in about 70% of patients where they can get an area of redness or irritation at the site where the injection was given. Cytokine release syndrome was seen in about half of patients, always low grade, grade 1 or grade 2 cytokine release syndrome. We saw infections in about half of patients, mostly those were respiratory tract infections, things like sinusitis or URI [upper respiratory tract infection] or pneumonia. And there was only one death and that was a patient who had completed therapy, and the death was reported to be unrelated to the mosunetuzumab.

The product appears to be an effective treatment for sure, reasonably safe treatment in people with low tumor burden FL, so that's the data that that we generated here at this meeting.

As to how to apply this data, there is an ongoing the trial being conducted by the southwest oncology group and a similar patient population that's comparing mosunetuzumab with rituximab as initial therapy for these patients. What we reported here is not a randomized trial, this was just a phase 2 study to establish efficacy and safety.
 

Source:

Burke J M, Flinn I W, Budde L E, et al. Fixed-Duration Subcutaneous Mosunetuzumab Is Active and Has a Manageable Safety Profile in Patients with Previously Untreated, Low-Tumor Burden Follicular Lymphoma: Updated Results from the Phase II Morningsun Study. Dec 7-10, 2024; San Diego, CA. Abstract: 3008