Zanubrutinib Plus Obinutuzumab for FL?

The FDA has accepted a supplemental Biologics License for the combination of Zanubrutinib and Obinutuzumab for patients with Relapsed/Refractory Follicular Lymphoma.

Lots to explain here. (And thanks to reader Shelley for sending me the link to this news.)

Zanubrutinib is a BTK Inhibitor. BTK stands for Bruton's Tyrosine Kinase, a protein that is an important part of the pathway that controls B cells (the immune cell turns cancerous in Follicular Lymphoma). As I wrote a few weeks ago, BTK Inhibitors seem like they should be really successful for FL, since they target B cells. But there hasn't been a huge amount of success with them -- at least not what would seem logical. It has already been approved for certain patients with some other B Cell cancers -- Chronic Lymphocytic Leukemia, Waldenström Macroglobulinemia, Mantle Cell Lymphoma, and Marginal Zone Lymphoma. But this combo does seem to have some success, as I'll get into below.

Obinutuzumab, the other half of this combination, is a Monoclonal Antibody, like Rituxan. In fact, of al of the alternatives to Rituxan that have been developed in the last few years, Obinutuzumab has been the most successful.

The FDA will consider giving the combination a Supplemental Biologics License. A Biologics License is given to treatments that are created from living materials (unlike a chemotherapy, which is created from non-living chemicals). 

The application is based on results from the phase 2 ROSEWOOD clinical trial. This trial compared Zanubrutinib and Obinutuzumab to just Obinutuzumab. After a median follow-up of 12.5 months, the 102 patients taking the combination had an Overall Response Rate of 68.3% (with a Complete Response Rate of 37.2%), compared to the O group having an ORR of 45.8% (CRR of 19.4%). The Duration of Respose after 18 months was 70.9% (versus 54.6%). So adding Zanubrutinib clearly improved the results. 

In a follow up, after a median of 20.2 months, the combo ORR was 69% (CRR of 39.3%), versus the O group's ORR of 45.8% (CRR 19.4%). The median Duration was Not Estimable, meaning more than half of the patients were still getting a  response (so a median -- the halfway number -- couldn't be calculated).

(ORR is the primary end point for the clinical trial, which I find interesting. In other words, it's the main thing that they will measure to determine if the trial has been successful. They will also measure other things -- Duration of Response, Progression-Free Survival (PFS), Overall Survival (OS), Time to Next Treatment, and safety. All of them are important, maybe more important than ORR. Response is great, but if it doesn't last and doesn't keep someone alive, it's not that impressive. Just my Cancer Nerd opinion. The FDA will ultimately decide what kind of data it wants to see from them.)

Safety is important, so side effects matter. The most common side effects were diarrhea (combo, 18.2%; O only, 16.9%), fatigue (15.4% vs 14.1%), and fever (13.3% vs 9.7%).

The FDA will probably make a decision about this in early 2024.

Maybe we'll get some more updated data at ASH in December.

It would great to have a treatment that showed that BTK inhibitors might actually work well on Follicular Lymphoma. I'll be sure to share any more news. (And thanks again, Shelley.)