This just in:
Press release yesterday afternoon from Immunomedics with the results of a phase II trial of Epratuzumab and Rituxin in previously untreated Follicular Lymphoma patients.
Dang good results: 59 patients, 88.2% achieved a response. The breakdown: 25 of them (42.4%) had a complete response, and 27 (45.8%)
had a partial response. Another 6 (10.2%) kept things stable. After 3 years, 60% of patients are still in remission.
Not bad at all.
Epratuzumab, like Rituxan, is a monoclonal antibody (there's that -mab ending again). While Rituxan targets the CD20 protein on a cancer cell, Epratuzumab goes after the CD22 protein. This seems to be why they work well together: if one misses a cell's target, the other might be able to catch it. Another difference is that Epratuzumab is humanized, unlike Rituxan, which is made from mouse cells. So Epratuzumab is likely to result in fewer allergic reactions.
Now, the cold water:
First, it's a phase II trial. I'm guessing the results will hold up in a larger, phase III trial, but it's still a while before FDA approval.
Second. the press release points out that "Although rituximab combined with chemotherapy has improved the survival
of previously untreated patients with FL, many patients are unable or
unwilling to tolerate chemotherapy," and thus this combination might be an alternative. Interesting way of positioning itself. If this is meant for initial therapy (the patients were all previously untreated), it's hard to tell if anyone would be "unable...to tolerate chemotherapy" before they actually had any chemo. I suppose the potential patient could have tried a round or two and then had a rough time and dropped it, and so this is an alternative. As for those "unwilling to tolerate chemotherapy," I can't imagine they wouldn't try straight Rituxan first (though it sounds like they received both MABs at the same time for four weeks; still, why not try just one?).
So, I guess I'm confused about who would use this, given that statement. The results are great, no question. But not all that much better than Rituxan, which has, if I remember correctly, about 75% overall response, and about 50% complete response, with about 24 months of progression free survival. Every little improvement helps, though I wonder how an insurance company will evaluate the additional cost for a few months of PFS.
That's uncharacteristically negative of me. Maybe I'm just hoping we can move beyond antibodies for initial treatments and focus more on some newer combinations? (Jeepers -- am I getting all spoiled by kinase inhibitors? Losing my boyish enthusiasm for every new treatment? I hope not....)
OK, we'll call it good news. Epratuzumab is definitely another arrow in the quiver. But I want to see more.