Rituxan + Pidilizumab for Follicular Lymphoma

I think most of the main ASH announcements are over now. We'll have to wait for the post-ASH commentary that will likely come over the next few weeks. (I imagine Patient Power, for example, will have a wrap-up video sometime soon.)

But does that mean the Follicular Lymphoma news is over for now? Absolutely not. In the latest issue of The Lancet Oncology is a report on a phase 2 study of Rituxan and Pidilizumab that shows some promise -- good activity against Follicular Lymphoma cells, with side effects that aren't too horrific.

I'll be honest -- I don't know a whole lot about Pidilizumab. From what I can tell, Pidilizumab has been studied as a treatment for solid tumors as well as lymphomas. A phase 2 study of DLBCL patients after auto stem cell transplant was pretty successful. I believe that this is the first phase 2 on Follicular Lymphoma patients.

Pidilizumab seems pretty cool. It is, like Rituxan, a Monoclonal Antibody (which is why it has that -mab ending on the name). Just as Rituxan targets the protein CD20 on B cells, Pidilizumab targets something called PD-1, which stands for Programmed Cell Death 1. PD-1 does a job we don't want it to do: it blocks T cells from killing off the cell. So when a cell has PD-1 on its surface, it signals to T-cells that it should be left alone.

So guess what kind of cells has PD-1 on it? Yeah. Follicular Lymphoma. Grr. The FL cells have other substances within them that trigger PD-1 to block the T cells.

But Pidilizumab seems to do the job. It targets PD-1 and blocks it, thus allowing T cells to come and do their job. (It "unleashes" the T cells, as the article puts it, which sounds much cooler.)

So how successful is Pidilizumab, when combined with our old pal Rituxan? In this small phase 2 study, 29 Follicular Lymphoma patients were given the -mab combo, and 19 of them (66%) had a response, with 15 of those 19 (a little more than half overall) having a Complete Response. That's pretty good.  Rituxan has about a 40% response rate, with 11% CR. So combining the two increases the effectiveness.

More importantly, it does so with about the same side effects as Rituxan alone.

So Pidilizumab certainly seems like a keeper. Obviously, a phase 3 trial, with more participants, is going to be the next step. There's some suggestion that maybe trying it on its own, in a trial with a direct comparison to Rituxan, might also happen in the future.

Certainly something else to keep an eye on. Maybe another arrow in the quiver.