BTK inhibitors
The major new story in MS this year and for the next few years will be Bruton's tyrosine kinase (BTK) inhibitors. BTK is an enzyme which is important for the activation of B lymphocytes and other types of immune cells such as the microglia that reside in the brain. Inhibitors of BTK could potentially be effective treatments for autoimmune diseases including MS. There has been intense interest from the pharmaceutical industry in testing these agents, with multiple large phase III studies in relapsing and progressive MS from several companies. These studies launched around 2018 and the results are starting to become available.
So far, there are published results from 3 independent studies and press releases for two additional studies. These have mixed, but intriguing results. A study in relapsing MS comparing evobrutinib to teriflunomide (one of the current approved agents for treating relapsing MS) failed to demonstrate that the BTK inhibitor was superior. A second study comparing tolebrutinib to teriflunomide in relapsing MS also did not show any benefit on relapses, but did show a 30% decrease in worsening of disability. A concurrent study in secondary progressive MS comparing tolebrutinib to placebo confirmed the benefit for progression, with a similar 31% reduction in confirmed disability progression.
The most recent results from a third agent, fenebrutinib, are available only as a press release dated November 10, 2025. A study in relapsing MS found that fenebrutinib was significantly better than teriflunomide in preventing relapses, in contrast to the results with evobrutinib and tolebrutinib. The study comparing fenebrutinib to ocrelizumab in primary progressive MS found that the two agents were similar. Ocrelizumab is already demonstrated to reduce progression. More details on these studies will be made public in the near future and additional studies are in progress with results expected in the next year.
BTK inhibitors may have a role in MS treatment, and FDA approval of tolebrutinib is expected in late 2025 or early 2026. The effect on progression is particularly welcome, since we have limited options with demonstrated benefit for progression. More information will be available in the near future, and we will see what role BTK inhibitors will play in MS treatment.