ASH Review: Mosunetuzumab for Untreated FL

 Another ASH presentation that has some lymphoma experts excited:

604: Subcutaneous Mosunetuzumab As First-Line Therapy for Patients with High Tumor-Burden Follicular Lymphoma (FL): First Results of a Multicenter Phase 2 Study.

 As you probably know, Mosunetuzumab is a bi-specific antibody. It's a lot like Rituxan, in that it attaches to the same CD20 protein on the surface of a cancer cell. But it also attaches itself to a protein on a T cell, an immune cell that can eliminate the cancer cell when it gets close to it. Bi-secifics are one of those newer treatments that get lymphoma specialists very excited. Mosunetuzumab is already approved by the FDA for FL patients with Relapsed/Refractory disease (just about a year ago). 

This research looks at a different population -- untreated patients, though those with high tumor burden (about 72% had stage 4 disease). There was also a different delivery method -- subcutaneous, an injection, rather than intravenous. 

The study looked at 43 patients. The title says "First Results," and these are indeed very early results -- some patients in the study haven't even been evaluated yet for how effective the treatment has been for them.

Of the 26 patients that have been evaluated so far, the Overall Response Rate has been 96%, with the Complete Response Rate at 81% ( that's 22 out of 26, and all 22 were seen at the first response assessment, meaning the treatment worked very quickly). Responses were also durable. At 6 months, 2 patients had disease that progressed (one of them transformed to DLBCL), but the rest of the group had remained stable or in remission.

A larger group were able to be evaluated for safety -- 39 patients. In this group, the most common side effects were problems at the injection site (72%), Cytokine Release Syndrome (51%), fatigue (33%), dry skin (33%), and skin rash (26%). More serious neutropenia (low white blood cells count) occurred in 10% and infections occurred in 26%. One patient died of cardiac arrhythmia while being treated for COVID19-associated pneumonia. Only 2 patients needed to be hospitalized with CRS. 

So overall, this is really great data to make the case for Mosunetuzumab for untreated FL. One of the researchers pointed out that more data is needed to show that it is effective over the long term. 

An article in Healio called it "remarkable" and  "highly encouraging" (though it doesn't say who exactly is being quoted). 

Lots of good news lately in the world of bi-specifics. I'm sure we'll be seeing even more in the near future.