A unique experimental treatment for multiple sclerosis is showing promise, though it's still in early phase clinical testing. The medication is branded as Tovaxin, sponsored by PharmaFrontiers Corporation based near Houston, Texas.
Autologous Immunity
Tovaxin, currently in Phase 1 and 2 clinical trials, is described as a T cell therapeutic vaccine that works similar to certain cancer vaccines. Autoreactive T cells that make up this investigational vaccine don't make copies of themselves, but cause an immune response, according to PharmaFrontiers.
This immune response is directed against the T cells within a person that target myelin, a fatty substance that protects nerve fibers in the brain and spinal cord and also helps them communicate with each other.1 As a result of this onslaught, these myelin-targeting T cells are drastically reduced. According to a PharmaFrontiers press release, "Tovaxin has considerable potential because it attacks the underlying cause of MS rather than just addressing its symptoms."
Under Scrutiny
The medication is currently being tested in a pair of Phase 1/2 clinical trials under an Investigational New Drug Application (IND) submitted to the Food and Drug Administration (FDA). PharmFrontiers says the first trial involves nine patients who are being given consecutively escalating doses of the medication to evaluate potential toxicity, whether the patients can tolerate it, and its effectiveness against MS. Enrollment for this study is expected to be completed sometime this year, the company stated.
The second trial is a Phase 2 open label retreatment study of 50 patients who initially were successfully treated with the drug. (Unlike blinded studies, open label trials are those in which both clinical trial staff and patients are aware of the name of the drug being tested). Each patient in this trial has previously been treated with or could not tolerate standard multiple sclerosis therapy. The study is designed to analyze the safety and tolerability of Tovaxin further, to determine the most effective timing of booster doses for future studies, and to evaluate the medicine's effectiveness against MS, PharmaFrontiers reported.
Separate Analyses
In one of the most recent clinical trials to test the efficacy of T cell vaccination,2 researchers in the department of Immunology at Baylor College of Medicine in Houston tested the vaccine in a group of 54 patients with relapsing-remitting or secondary-progressive MS.
All patients were immunized with autologous myelin protein-reactive T cells (those that are activated by a protein produced by myelin), and the researchers then checked for each individual's relapse rate, their level of disability, and brain lesions as seen on MRI scans throughout the 2-year pilot study.
"Depletion of myelin basic protein-reactive T cells correlated with a reduction (40%) in rate of relapse in relapsing-remitting MS patients as compared with the pre-treatment rate in the same cohort," wrote the study team.
While the reduction in disability was "minimal" in the group of individuals with relapsing-remitting MS, disability was "slightly increased" in those with the secondary-progressive form of the illness, they noted. The researchers used the Kurtze Expanded Disability Status Scale (EDSS) to measure disability in this study. The higher the score, the more disabled a patient is.3
The number of brain lesions as seen in magnetic resonance imaging (MRI) stabilized after the vaccine was given, they noted. "The findings suggest some potential clinical benefit of T cell vaccination in MS and encourage further investigations to evaluate the treatment efficacy of T cell vaccination in controlled trials," the research team concluded.
1. National Multiple Sclerosis Society. What Is Multiple Sclerosis? Available at: http://www.nationalmssociety.org/What%20is%20MS.asp. Accessed April 22, 2005.
2. Zhang JZ, Rivera VM, Tejada-Simon MV et al. T cell vaccination in multiple sclerosis: results of a preliminary study. J Neurol 2002 Feb;249(2):212-8.
3. University of California, Irvine. Kurtzke Expanded Disability Status Scale. Available at: http://www.ucihealth.com/ms/kurtzkeedss.htm. Accessed April 22, 2005.
John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include coverage of health news for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.
