The approved lymphoma therapy Rituxan (rituximab) has shown promise as a treatment for multiple sclerosis.
A new study indicates the Genentech treatment is effective and safe against neurological diseases like MS for up to seven years.
The research, “Long-term safety of rituximab induced peripheral B-cell depletion in autoimmune neurological diseases,” was published in the journal PLOS One.
Rituxan targets a protein called CD20 in immune B-cells, which are responsible for the production of antibodies. The U.S. Food and Drug Administration (FDA) approved Rituxan as a treatment for lymphoma and rheumatoid arthritis.
The antibody in Rituxan leads to a depletion of certain B-cells. It is currently being investigated as a potential therapy for relapsing–remitting multiple sclerosis.
In fact, “rituximab is often used as an off-label therapy in patients with immune-mediated neurological disorders (PIMND), including multiple sclerosis,” the researchers wrote.
Off-label use means Rituxan is prescribed as a therapy for diseases other than those for which it was approved.
While open-label and randomized controlled studies have shown promising results for Rituxan in disorders other than lymphoma or rheumatoid arthritis, scientists have had long-term safety concerns about it. Those concerns are particularly important because Rituxan can be prescribed for years.
A team of researchers decided to examine the “long-term safety, incidence of infections, and malignancies in subjects receiving continuous therapy with the B-cell-depleting agent rituximab over at least three years or longer.”
They looked at the records of multiple sclerosis who had received Rituxan a minimum of 18 months. The analysis included patients with neuromyelitis optica and myasthenia gravis treated with Rituxan for the same period.
The primary endpoint of the study was to assess rituxan’s long-term safety — in terms of adverse and serious adverse events — in patients treated between three and seven years without interruption.
Patients received Rituxan intravenously in 1,000 mg doses administered twice a year or every six to nine months. The number of B-cells in their blood was determined at baseline and before each treatment cycle, and a medical evaluation was performed every three months.
The analysis included 29 patients — 22 women and seven men. Five patients had multiple sclerosis, three myasthenia gravis, and 21 neuromyelitis optica.
“We observed complete depletion of circulating B-cells in the majority of the patients and marked depletion in some of the patients throughout the treatment period,” the researchers wrote.
Rituxan was well tolerated, and the rate of adverse and serious adverse events was low. Also, “there were no cases of progressive multifocal leukoencephalopathy (PML) or malignancies observed throughout the observation period,” the team wrote.
PML is a rare brain infection that has been associated with long-term use of some therapies.
“This study demonstrates that long-term depletion of peripheral B-cells appears safe and efficacious in treating PIMND. Longer and larger prospective studies with rituximab are needed to carefully ascertain risks associated with chronic B-cell depletion, including malignancies,” researchers wrote.
They emphasized that although this was a small study, the results “complement the growing literature [scientific studies] documenting the safety and tolerability of B-cell-depleting agents in neurological diseases.”