- Neuromyelitis optica spectrum disorder (NMOSD) is a group of autoimmune diseases where the body’s immune system attacks the optic nerve, the spinal cord and specific locations in the brain. There is a lack of treatments specifically for NMOSD and current treatments are general immunosuppressants.
- In this new study, 37 people with NMOSD were given rituximab and followed for an average of 4.5 years.
- Lower doses of rituximab than what are usually administered appear effective in reducing disability severity and the rate of relapse in people with NMOSD and with mild side effects.
- More research is needed to find the most effective and safe dose of rituximab for treating NMOSD.
What is NMOSD and why is rituximab used to treat it?
Neuromyelitis optica spectrum disorder (NMOSD) is a group of autoimmune diseases where the body’s immune system attacks the optic nerve, the spinal cord and specific locations in the brain. In its early stages, NMOSD can easily be mistaken for MS. Unlike MS, people with NMOSD have antibodies in their blood which attack the aquaporin-4 (AQP4) water channel in astrocytes (a type of brain cell) causing damage to the nerve cells in the optic nerve.
This is a lack of treatments specifically for NMOSD and current treatments are general immunosuppressants for acute attacks and to prevent relapses.
Rituximab is a disease modifying treatment (DMT) that targets the CD20 protein on B cells, a type of immune cell that produces antibodies. By binding to the CD20 protein, rituximab reduces the level of B cells in the bloodstream temporarily. It is normally used for autoimmune disorders and some types of cancers.
By reducing the number B cells circulating in the bloodstream, rituximab reduces the level of antibodies and reduces the attacks and damage to the optic nerve.
There is evidence from small clinical trials and observational studies supporting the use of rituximab as a first-line therapy for NMOSD. However, the optimal dose remains unclear. Initial doses of rituximab for the treatment of NMOSD were based on lymphoma treatment, which were high, quite expensive and resulted in serious side effects.
Several studies have suggested that a lower dose of rituximab is effective at lowering relapse rate and reducing disability, although large clinical trial data is lacking.
What did the researchers to?
An Australian team of researchers including Professor Pamela McCombe and Dr Stefan Blum investigated the medical records of 37 people with NMOSD who were treated with rituximab. Of these, 27 people were positive for AQP4 antibodies (seropositive for AQP4) and 10 were negative (seronegative).
The researchers studied the frequency of relapses before and after rituximab treatment and the level of disability. The participants’ medical records had an average of 4.5 years of information after the start of rituximab for analysis.
What did the researchers find?
Published in the journal Multiple Sclerosis Journal – Experimental, Translational and Clinical, the researchers found that the relapse rate in people with NMOSD after treatment with rituximab was much lower compared to the rate before treatment.
Interestingly, the reduction was significant in participants who were seropositive for AQP4, but not for those who were seronegative.
The treatment was safe, although about a third of participants developed infections during follow-up after receiving rituximab. Most of these infections were mild.
Why is this important?
In this study, rituximab was given as two 500mg infusions two weeks apart followed by single 500mg doses every four to nine months, which is a lower dose of rituximab than is currently used. The current dose has a higher risk of unwanted side effects.
The fact that this lower dose of rituximab appears to be effective in reducing disability and people who were seropositive for AQ4 antibodies had fewer relapses per year is welcome news.
While more research is needed to find the optimal dose of rituximab for treating NMOSD, effective treatment with a lower dose can enhance safety and reduce side effects, and ultimately improve outcomes for those living with NMOSD.
