During the COVID-19 pandemic, patients with multiple sclerosis and their clinicians have had questions and concerns about whether immunotherapies for MS could influence risk for infection or lead to an unfavorable outcome.

In a new study, an international group of authors, including researchers from Brigham and Women's Hospital, present the cases of five MS patients who developed COVID-19 infection while taking the oral disease-modifying therapy teriflunomide and continued taking the medication. All five patients had favorable outcomes, with their COVID-19 taking a mild course and without experiencing relapse of their MS.

In the current international, multicenter study, researchers report on five patients, ranging in age from 52 to 79, who had been taking teriflunomide for at least six months. The patients continued their teriflunomide therapy after COVID-19 diagnosis and had self-limiting illness without experiencing MS relapse.

Teriflunomide modulates the immune response by selectively reducing the level of activated T and B lymphocytes without suppressing the body's full immune response. One possibility, the authors write, is that teriflunomide could prevent an excessive immune response while maintaining an adequate defense against the virus. The authors also discuss preclinical data suggesting that the drug may reducing viral nucleotide synthesis in infected cells.

The case series was small, retrospective, open-label, uncontrolled, and nonrandomized, and the authors state that future studies are necessary to understand what role, if any, teriflunomide therapy may play in COVID-19 infection because patient recovery may be unrelated to the treatment.

The study was published in the Journal of Neurology.