Rituximab and Ocrelizumab in Rheumatoid Arthritis and MS

One of the treatment stories was one we heard before in 2010 ISNI meeting in Sitges (SPAIN), the one about Rituximab and MS. Apart from the commercial history of Idec, Biogen, Genentech and so on, the important thing is that it all ended up in an phase II clinical trial. A revolutionary clinical trial.

It was revolutionary because it challenged the “MS-is-(for-sure)-a-T-cell-mediated-disease” dogma showing that a B cell therapy was able to achieve unbelivable results in MS. But most importantly it was revolutionary because it got a striking 91% reduction in new enhancing lessions compared to placebo and, despite being a phase II trial, achieved a 50% reduction in relapse rates compared to placebo in less than a year. These are Natalizumab-level results, but with a quite safer profile than Natalizumab. At least, the experience with other diseases yields a progressive multifocal leukoencephalopathy (PML) rate much lower to that of Natalizumab. Just 6 reumathoid arthritis (in which Rituximab is used routinely) patients have suffered PML over more than 120000 patients treated despite RA patients having used much more frequently concomitant immunessuppresants than MS patients do usually.

The results achieved in the study deserved a NEJM paper and, for sure, a phase III trial. But that won’t happen. At least not in the short term.

It turns out that Rituximab patent expires in the US in 2015. This means that, by the time the phase III is over, the patent will be over too. So, no profit then in doing such an investment. To surpass this inconvenience Genentech invented a new drug, antiCD20 as well, but humanized (Rituximab is chimeric), called Ocrelizumab, and started the whole process again. Then, obviously, we got a phase II trial with ocrelizumab in MS. Results have not been published yet but have been presented at 2010 ECTRIMS meeting and show,as expected, an almost equal efficacy profile to that of rituximab. But a patient died on the ocrelizumab arm from an unexpected “systemic inflammatory syndrome”. That could be chance and still hope larger studies to be assured… but it was not chance. Several rheumatoid arthritis trials with ocrelizumab have been terminated because “the overall benefit to risk profile of ocrelizumab was not favorable in RA” what it really means that 7 patients died unexpectedly in the high ocrelizumab dose arms of the trials.

(via ProHealth)