FDA Approves Mosunetuzumab for R/R FL

Yesterday, the FDA approved the bispecific treatment Mosunetuzumab for patients with Relapsed/Refractory Follicular Lymphoma who have had at least 2 prior treatments. The treatment will go by the name Lunsumio (but I'll probably keep calling it Mosunetuzumab anyway).

The approval is based on results from a phase 2 clinical trial, so a phase 3 trial will be necessary to confirm that it works on a larger group of patients. But it will be available in a few weeks while that trial is being run.

It's a big deal. It's the first bispecific approved for FL in the United States (the European Commission approved it using pretty much the same data, back in June). As you know if you've been reading the blog, lymphoma experts have been very excited about bispecifics for a few years. Once data from trials started becoming available, it was pretty clear that bispecifics could be a game-changer -- a non-chemotherapy treatment option that uses the immune system to kill cancer cells. I've been very interested in it for a few years, since I asked my oncologist which treatments he would consider if/when I needed treatment again, and he mentioned this trial.

As a reminder, a bispecific works by targeting two proteins, one on a cancer cell, and the other on a T cell, an immune cell. Mosunetuzumab targets CD20 on the B lymphocyte that turns cancerous in patients with FL (it's the same protein that Rituxan targets), and then targets CD3 on the T cells. It brings them together so the T cell can take out the cancer cell. 

It's very effective. The phase 2 trial that led to FDA (and EC) approval showed an 80% Overall Response Rate, including 60% of patients getting a Complete Response. It was also pretty durable, with the time that the treatment lasted being a median of 22.8 months. The most common side effects were Cytokine Release Syndrome (39% of patients), and fatigue, rash, pyrexia and headache (all more that 20% of patients).

Bispecifics are often talked about at the same time as CAR-T (see my last post, for example). They do have some things in common, including that they work by have T cells go after the cancer cells. They're also different in many ways, including cost (because CAR-T needs to be made specifically for each patient, it can be more expensive). A conversation with your oncologist will help sort out which would be most appropriate. 

As I said above, the approval is for FL patients who have had two or more treatments already, so newly diagnosed patients wouldn't be eligible, and neither would I (not having had a second treatment). But it will benefit a whole lot of FL patients out there.

And of course, it's important to remember that this is a provisional approval, and if the results of the next trial show that, for example, there are some dangerous long-term side effects, then approval would be withdrawn. (It happens, unfortunately.)

But for now, there's lots to be excited about.

More ASH commentary soon.

Stay well.