A trial of the drug ocrelizumab has demonstrated a measurable slowing of the primary progressive form of multiple sclerosis (MS). The effect is not very large, but for a disease that has proven so resistant to treatment in the past, any benefits mark a big step forward. In a separate trial, ocrelizumab outperformed existing drugs for patients with the more common relapsing remitting MS.
All forms of MS occur when the immune system malfunctions, attacking the myelin sheaths that protect nerves and interfering with the transmission of impulses in the neural system. Patients with primary progressive MS almost always get continuously worse, while, as the name suggests, the relapsing remitting form can give sufferers some relief between attacks.
Immunotherapy has been shown to reduce the frequency and severity of attacks for people with relapsing remitting MS, but it is not generally recommended for people with the primary progressive form of the disease.
A paper in the New England Journal of Medicine reports a trial of ocrelizumab given to almost 500 people with primary progressive MS. Ocrelizumab depletes CD20-expressing B cells, which represent at least part of the immune system's attack on myelin. Although this potentially leaves the body less able to fend off the infections B cells are meant to fight, that may be a price worth paying for people with MS.
Of the 488 primary progressive MS patients given ocrelizumab, 101 died or withdrew before the end of the trial, but this was still a significantly lower proportion than among the 244 given a placebo, a third of whom did not finish the trial. Those on the drug did better on a number of tests for the progression of the disease than those in the control group.