Rapamycin, Approved for Other Indications, Potentially Effective for MS, Study Suggests

Treatment with Rapacan (rapamycin) decreased the size and volume of brain lesions in patients with multiple sclerosis (MS), an Iranian study reports.

The study, “Promising effect of rapamycin on multiple sclerosis,” was published in the journal Multiple Sclerosis and Related Disorders.

Rapamycin, or sirolimus, is an immunosuppressive agent approved by the U.S. Food and Drug Administration to prevent organ transplant rejections and to treat a lung disease known as lymphangioleiomyomatosis. It is marketed as Rapacan by Biocon (the therapy used in the study), and in the U.S. and U.K. as Rapamune.

The therapy increases the number of protective T-regulatory cells (Tregs) that express two markers: FoxP3 and GARP. Tregs, in turn, inhibit the proliferation of T-responder cells preventing inflammation.

A previous study showed that the therapy could prevent relapsing-remitting experimental autoimmune encephalitis in mice (a mouse model of human MS).

In this study, researchers in Iran tested the effectiveness of rapamycin to prevent disease progression in patients with relapsing-remitting MS (RRMS).

A total of eight patients were enrolled in the trial (IRCT2012092510936N1). They received two 1 mg tablets of Rapacan daily for six months. Using magnetic resonance imaging (MRI), researchers assessed brain volume alterations and lesion size before and after the treatment.

Results showed that treatment with Rapacan significantly reduced the mean lesion area size. In addition, there was a marked decrease in the volume of these lesions after treatment.

The team also evaluated the expression of the genes FoxP3 and GARP in Tregs isolated from the patient’s peripheral blood before and after treatment. The number of FoxP3-expressing Treg cells markedly increased post-treatment, and while an increase in GARP-expressing Treg cells was also seen, it was not found to be significant.

Treg cells suppress the proliferation of T-responder cells and curb inflammation. A noteworthy decrease in the number of T-responder cells was also seen after treatment with Rapacan.

The Expanded Disability Status Scale was used to measure disability levels in patients before and after treatment. A higher score indicates worse disability. In 50% of the patients (four patients), a reduction in the EDSS score was observed, but it was not statistically significant.

The safety of Rapacan was also assessed at several points during the study. According to the team, no considerable side effects were reported during the treatment.

“Based on our findings, rapamycin might be considered as an effective treatment for RRMS,” the team concluded, adding that “more studies are required to confirm this finding and investigate the therapy with higher doses of rapamycin for longer periods.”