Antibodies for Follicular Lymphoma

The May 2012 issue of Hematologic Malignancies reports on results of a phase II clinical trial comparing Rituxan with Obinutuzumab, and Obinutuzumab wins!


This seems like a pretty big deal. It's the first time the two monoclonal antibodies went head-to-head in a clinical trial. Both antibodies target the CD20 protein on the surface of B-cell lymphocytes, but there are some key differences. Obinutuzumab (also known as GA101) is a humanized antibody, unlike Rituxan, which was derived from mice. It is also glyco-engineered. (Which is apparently important, but honestly, I've read a dozen different explanations of what glyco-engineering is, and I can't get a handle on it. Sorry. We'll just say it's a good thing and leave it at that.) Obinutuzumab also seems to bring on death of cancer cells more directly.


As for results: 149 Follicular Lymphoma patients took part in the study. Of those given Obinutuzumab, 44.6% had a response, compared to 33.3% who were given Rituxan. That seems like a pretty good improvement.

We need to step back a little bit, though.

First of all, these results aren't new; they were presented at the 2011 ASH conference. Even then, they were seen as exciting, but not earth-shattering; in a sample of 149 patients, which is fairly small, an 11 percentage point difference is not statistically significant (which means it can't actually be attributed to Obinutuzumab). 


But what is encouraging is that we have enough data to justify a phase III trial, which will mean a larger sample. 


Rituxan has been a miracle for so many people -- I'll include myself -- but despite a dozen or more attempts at improving on it, there has yet to be a monoclonal antibody that can do much better. Maybe Obinutuzumab will prove to be the one, and the trial will show that. Like Rituxan, it won't be a cure. At best, it might prove to be an alternative for patients who are sensitive to Rituxan, or who become Rituxan-resistant.


At worst, it's another arrow in the quiver. Not too bad.