In Monoclonal Antibodies: What Are They? we discussed a little bit about how T-cells and B-cells function within the immune system and how medications have been created to target specific antigens on those same lymphocytes. If you haven’t read it, I recommend that you read that post first and then come back to this one.
What monoclonal antibody treatment for MS is available at this time?
Natalizumab (Tysabri®) is an FDA approved monoclonal antibody treatment targeting T-cells (CD25+ T-cells) for use in patients with relapsing-remitting MS or secondary progressive MS with continued relapses. Efficacy was demonstrated in two multi-center trials where the risk of progressive multi-focal leukoencephalopathy (PML) was first discovered. Tysabri was pulled from the market and later reintroduced in June 2006 in the US under the TOUCH™ program. Since that time 31 patients have developed PML and 5 of those patients have died.
The TOUCH™ program for natalizumab requires multiple provider and facility certifications and persistent monitoring of patients throughout their use of this treatment. Logistics of handling the medication and the cost are substantial with reported reported reimbursements ranging from $2400 to $12,000 per infusion (according to MSers who shared with me this information last year). The medication is administered every four weeks by intravenous infusion (IV) at which time patients are screened for problems and must sign a document acknowledging the risks of therapy prior to receiving the drug. In the US, you can only receive Tysabri if you are enrolled in the TOUCH™ program.
What are some monoclonal antibody treatments in development for MS?
At present, several additional monoclonal antibodies are being studied as investigational treatments for MS. They are not currently available for routine use in the treatment of MS.
Rituximab (Rituxan®) is a monoclonal antibody directed at B-cells (CD20+ B-cells) and has been reported to be effective in the treatment of relapsing-remitting MS. Studies in primary progressive MS did not produce statistically significant results however. This drug is FDA approved for treatment of rheumatoid arthritis and non-Hodgkin’s lymphoma. (Read more about Rituxan in Rituximab Infusion: My First Experience)
[Note: I believe that ocrelizumab and ofatumumab which target CD20+ B-cells, humanized and fully human monoclonal antibodies respectively, already have replaced rituximab in active MS studies. See listing in clinicaltrials.gov.]
Alemtuzumab (Campath®) is another monoclonal antibody directed at lymphocytes (CD52+ B-cells) which is under investigation for treatment in MS. Campath was found to be more effective than Rebif in early relapsing-remitting MS. Both rituximab and alemtuzumab are associated with longer-term immunosuppression (6 to 12 months). Serious immunological and infectious complications have occurred with both these monoclonal antibody therapies.
