Fenebrutinib

A highly selective, reversible, brain-penetrating BTK inhibitor. It reported positive Phase 3 results in relapsing MS (FENhance 1 and 2) and primary progressive MS (FENtrepid), where it was non-inferior to ocrelizumab. The FDA accepted Roche's application under priority review on September 30, 2026 for both relapsing and primary progressive MS; no decision date has been announced.

Fenebrutinib blocks BTK, an enzyme that activates both B cells and microglia (brain cleanup cells). By targeting both cell types, it reduces acute inflammation causing relapses while also addressing chronic brain inflammation driving long-term disability.

Common side effects include urinary tract infections, sore throat, headache, and nausea. In Phase 3 trials, liver enzyme elevations were more frequent than with ocrelizumab in FENtrepid (13.3% vs 2.9%) but similar to teriflunomide in FENhance 1 and 2, bleeding events were slightly more common (10.2% vs 8.1% in FENtrepid), and more deaths occurred on fenebrutinib, from varied causes still being analysed. Regulators will weigh these findings against the drug's benefits.

In the Phase 3 trials, fenebrutinib was taken by mouth twice a day. It crosses the blood-brain barrier. The dose for any approved use has not been set, pending the FDA's decision.

Fenebrutinib is currently in phase 3 clinical trials for Multiple Sclerosis. It has not yet received FDA approval.

Both are brain-penetrant BTK inhibitors for MS, but they differ in their binding mechanism. Tolebrutinib binds irreversibly to BTK (permanently inactivating each molecule it encounters), while fenebrutinib is a reversible inhibitor (it binds and releases). Reversible binding may offer a different safety profile because the enzyme recovers function once the drug detaches. Fenebrutinib also has higher selectivity for BTK (130-fold over other kinases), which may reduce off-target effects.

Yes. The FENtrepid Phase 3 trial in primary progressive MS showed that fenebrutinib was non-inferior to ocrelizumab on confirmed disability progression over at least 120 weeks, meaning it performed about as well. The 12% lower risk it showed over the whole trial was not statistically significant. In relapsing MS, FENhance 1 reduced the yearly relapse rate by 51.1% versus teriflunomide and FENhance 2 by 58.5%.

Not yet. The FDA accepted Roche's New Drug Application under priority review on September 30, 2026, covering both relapsing and primary progressive MS, based on the FENhance 1, FENhance 2 and FENtrepid trials. Roche has not announced a target decision date. Liver enzyme elevations, bleeding events and a higher number of deaths on fenebrutinib will be part of the safety review^[1].

The only FDA-approved therapy for primary progressive MS is ocrelizumab, given by IV infusion or injection every 6 months. If fenebrutinib is approved, it would offer people with PPMS a daily pill with similar efficacy. Its ability to cross the blood-brain barrier and act on microglia directly may also matter for progressive disease.

Liver enzyme elevations were more common on fenebrutinib than on ocrelizumab in FENtrepid (13.3% vs 2.9%) and similar to teriflunomide in FENhance 1 and 2, bleeding events were slightly more common (10.2% vs 8.1%), and more deaths occurred on fenebrutinib than on the comparison drugs, from varied causes that Roche says are still being analysed. Common side effects included urinary tract infections and sore throat. Regulators will weigh these findings against the drug's benefits.