Sunday, August 23, 2009

Update on Pescovitz's Rituximab Phase-II trial

Pescovitz (and team from TrialNet) have finished a phase-II human trial of Rituximab, and the results have been accepted for publication at a big-name scientific journal. Unfortunately, that journal has embargoed the result data until publication, so I don't actually know the details of how well it worked. The good news, is that the study's authors did an oral presentation at ADA 2009, and (I'm told) that the results were good, but not as good as with the anti-CD3 monoclonal antibody drugs from Macrogenics or ToleRx. Those drugs preserved beta cell functionality for at least a year after treatment. Basically, untreated people lost half their ability to produce insulin in the year after onset of type-1 diabetes, but treated people retained about 95% of their ability. Rituximab was not as successful as that, but did preserve some insulin production.

Rituximab is a monoclonal antibody, a product of Genetech (now a division of Roche), and already approved by the US FDA for rheumatoid arthritis and several cancers. You can read more about it here:

It works by attacking B cells that have the CD20 marker. These B cells are part of the immune system and completely different that the beta cells (sometimes called B cells) in the pancreas. The immune system has many different types of both B cells and T cells. Most drugs currently being tested to cure type-1 diabetes target T cells. (For example: MacroGenics, ToleRx, Diamyd, Faustman, ATG, Abatacept, etc.) Rituximab is targeting a completely different type of cell (B rather than T). It is thought to work because B cells may interact with T cells influencing their targeting to attack beta cells. So this study is interesting, both because the results are good, but also because it potentially opens up a whole new area to understand as part of the cause of type-1 diabetes, and that means a whole new area where a cure or treatment might be found.

A follow on trial of Rituximab is currently being designed. It will probably involve repeated dosing of the drug. Obviously, I'll post when that clinical trial starts.

Discussion (Why many different treatments might be more effective.)

Right now, we have at least 5 drugs in phase-II or III human trials that, when given during the honeymoon phase, result in the patient loosing only half as much insulin production capacity, as if they were not given the drug. These include Rituximab, Diamyd's GAD65, several different anti-CD3s, and (maybe) Alpha Interferon. There are three ways of looking at these results:

The pessimist: "I don't want five half-way cures. I want one actual cure. Come back when you have something that works."

The engineer: "If it works half way now, then maybe we can improve it a little so it is three quarters working in a year or two, and 90% working a year or two after that and...."

The optimist: "Maybe we don't need a single cure. Maybe the proper combination of the many half cures we have will work right now, or will work for some people."

So if you're an optimist, then having several different treatments for type-1 diabetes which each target a different part of the autoimmune attack, is a good thing. We're used to thinking of a cure as being one pill or one operation or one something. In fact, for many of the more complex diseases (such as cancers, etc.), it is a cocktail of drugs which work together to have the best effect. And type-1 diabetes is surely a complex disease!

Of course "drug cocktails" are harder to test and harder to get approval for, and generally slower to market. In the past there has been discussion of pairing something that stops the autoimmune attack with something that regrows beta cells. That is one type of "drug cocktail", but it also may be that the thing that stops the autoimmune attack with the fewest side effects is itself a mixture of several drugs which target different parts of the autoimmune response.

Thanks to Dr. Gitelman for insightful discussions of this research. All mistakes here are my own.

Clinical Trial Record for the Rituximab trial is here:

Joshua Levy

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