Rituximab, developed by Genentech (part of the Roche group) and marketed under the brand name Rituxan in the United States and Mabthera in Europe, treats certain blood cancers like non-Hodgkin’s lymphoma and autoimmune diseases like rheumatoid arthritis.
It is also being investigated as a potential therapy for myasthenia gravis (MG).
How rituximab works
MG is an autoimmune disease in which the body’s immune system mistakenly attacks and damages healthy cells and tissues. This disrupts the transmission of signals between nerve cells and muscles, leading to weakness and a lack of muscle control. By curtailing the immune system, rituximab aims to slow the damage caused to the nervous system.
It is an antibody, or protein designed to interact with a specific target, against a protein called CD-20 that is present in B-cells. A type of immune cell that plays a role in the inflammatory immune response, B-cells are harmful in myasthenia gravis. When rituximab binds to CD-20, it lowers levels of B-cells. This may slow progression of MG and improve disease symptoms, reducing the need for other medications.
Rituximab in clinical trials
A Phase 2 clinical trial (NCT02110706) called BeatMG, sponsored by Yale University, is assessing the its effect in 50 patients with MG. During the trial, they receive two four-week cycles of either a rituximab or placebo infusion separated by a six-month break. The aim is to determine whether it is safe and well tolerated in MG patients and to gain a preliminary assessment of patient benefit, defined by a reduction in their daily dose of prednisone compared to the placebo-treated group. The trial is still ongoing at 26 U.S sites.
A randomized, double-blind, placebo-controlled Phase 3 study (NCT02950155), called Rinomax, is now recruiting up to 60 participants in Sweden to assess its safety and efficacy in people with new onset generalized MG. The trial will compare the change in quantitative myasthenia gravis (QMG) score and daily prednisone dose between the rituximab and placebo-treated groups after 16 weeks.
The results of additional clinical trials not listed on clinicaltrials.gov as well as the analysis of off-label rituximab usage have also been published. For example, a retrospective analysis of the effect of rituximab on six MG patients, published in the Porto Biomedical Journal, suggests that rituximab can improve patients’ quality of life.
An open-label clinical study conducted at Canada’s University of Alberta assessed the effect of rituximab in 14 MG patients. The results, published in the Annals of Clinical and Translational Neurology, reported that patients showed an improvement in muscle control (determined by an improvement in Manual Muscle Testing score) and a decrease in the need for other treatments.
It is given as an infusion into a vein.
Because it suppresses part of the immune system, rituximab treatment may increase the risk of serious infections. People who take high blood pressure medications may have to stop treatment before using rituximab, because blood pressure may drop during infusions.
Common rituximab side effects include fever, chills, aches, tiredness, joint pain and cold symptoms (stuffy nose, sneezing and sore throat).
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