ASH: Ibrutinib Not So Effective for Follicular Lymphoma?

As I promised, I've been trying to make my way through the abstracts for the annual meeting of the American Society for Hematology (ASH). Lots of good stuff comes out at this meeting. Not necessarily stuff that can be used immediately, but good stuff to keep an eye on.

The first one I want to look at (kind of briefly, I'm afraid) is "Ibrutinib Monotherapy in Relapsed/Refractory Follicular Lymphoma (FL): Preliminary Results of a Phase 2 Consortium (P2C) Trial." It has some not-so-good news.

As the title suggests, this one reports the results of a phase 2 trial on Ibrutinib, a BTK inhibitor that has been approved for use in Mantle Cell Lymphoma and CLL. As a BTK inhibitor, Ibrutinib targets a particular enzyme that is necessary for a cell to function properly. In this case, it's a cancer cell. Inhibiting it, or blocking it from doing its job, means keeping the cancer cell from living.

The trial looked at 40 Follicular Lymphoma patients who had already had at least one chemotherapy treatment, and who were need of another treatment of some kind. (The link will take you a breakdown of age, gender, and previous treatments, if you're interested.)

The Overall Response Rate was 30%, but 65% showed some reduction in tumor size. Interestingly, only 2 out of 18 patients who were Rituxan-refractory (that is, Rituxan stopped working for them) showed a response, while 8 out of 19 who were still Rituxan-sensitive showed a response, as did 2/3 of patients who had never had Rituxan before.

So, overall, the numbers aren't great. Their conclusion says, "Single agent ibrutinib is well tolerated with a modest ORR in relapsed/refractory FL at this early assessment. Continued follow-up is warranted to capture late responders and to establish response duration.  Ibrutinib appears less active in FL than in MCL and CLL. Early PET scans (C1D8) do not reliably predict for response."

But I think there is some room in there for hope. The Rituxan connection seems like the best place to look, with some reason to think that straight Ibrutinib might not be so effective, but a combination with Rituxan might work better. (That seems to be a trend -- targeting multiple pathways with multiple agents, recognizing that sneaky cancer can find a way around just one.)

I'm also hopeful that, as they suggest, a longer follow-up might show some better results. This one was pretty quick -- about 6 months. They raise the possibility that Ibritunib might work over the long term.

So I wouldn't count out Ibrutinib as a treatment for Follicular Lymphoma just yet.  More to come, I'm sure.