Tolebrutinib is an experimental therapy that is still being tested in multiple sclerosis patients in clinical trials. The oral medication is designed to block the activity of Bruton’s tyrosine kinase (BTK), a protein that is essential to the inflammatory activity of certain immune cells, such as B-cells and microglia. This is expected to reduce the inflammation that contributes to progressive nerve cell death in MS. One early study suggests tolebrutinib may be more potent than other therapies in its class.
Testing of tolebrutinib for multiple sclerosis is now ongoing in four Phase 3 clinical trials, which are large studies designed to assess a treatment’s efficacy. There are two studies for relapsing forms of MS, both expected to end in August 2023, and another two trials in progressive types of MS, expected to be completed in August 2024. If results from these studies are positive, they may support regulatory applications seeking the approval of tolebrutinib for MS. However, it currently is too early to know if or when the medication might be approved.
Clinical trials of tolebrutinib have not included, and are not enrolling, pregnant or breastfeeding patients. All participants who have the capacity to reproduce are required to use effective contraception methods to avoid the possibility of conceiving a child while on treatment. Consequently, it is unclear whether tolebrutinib can be safely taken during pregnancy or while nursing.
In one study, patients began seeing benefits of tolebrutinib about 90 days after starting treatment. That Phase 2 clinical trial enrolled people with relapsing forms of multiple sclerosis. A significant reduction in the number of inflammatory brain lesions became evident with tolebrutinib versus a placebo in about three months in the patients treated.
Hair loss has been reported as a side effect of tolebrutinib in a multiple sclerosis Phase 2 trial. Weight gain, however, was not among the adverse events reported in the study. Patients who experience unexpected effects of medications should consult their healthcare teams.
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