On March 2, 2026, Roche announced that its third and final pivotal Phase III trial of fenebrutinib in multiple sclerosis met its primary endpoint. That means all 3 major studies in the fenebrutinib program (FENhance 1, FENhance 2, and FENtrepid) have now produced positive results. According to the National MS Society, nearly 1 million people living with MS in the United States and 2.9 million worldwide could benefit from developments like these, making this one of the most significant clinical advances in years.
What Is Fenebrutinib, in Plain English?
Multiple sclerosis happens when the immune system mistakenly attacks the protective coating around nerve fibers in the brain and spinal cord. Over time, this damages the nerves themselves, leading to problems with movement, balance, vision, and thinking. There are 2 main ways this damage happens:
Most current MS drugs target only the first problem. They calm down the immune system to reduce relapses, but they do not get inside the brain to address the chronic smoldering damage that drives long-term disability, especially in progressive forms of the disease.
Fenebrutinib is different. It is a BTK inhibitor, meaning it blocks an enzyme called Bruton's tyrosine kinase that both B cells and microglia need to cause damage. Because fenebrutinib can cross the blood-brain barrier, it reaches the microglia inside the brain directly. That dual action on both inflammation and chronic brain damage is what sets it apart from most current MS drugs.
It is also a pill, taken twice daily. Many of the most effective MS treatments right now require IV infusions at a clinic every few months. An oral drug with this level of efficacy would make daily life easier for many patients.
Fenebrutinib Phase 3 Trial Results for Multiple Sclerosis
3 Phase III trials, 2,482 patients, all 3 positive
The FENhance 1 and FENhance 2 trials tested fenebrutinib head-to-head against teriflunomide (a widely used oral MS drug) in 1,497 adults with relapsing MS. Both trials ran for at least 96 weeks. According to Genentech's FENhance trial results, the data was consistent across both studies:
Both studies also showed statistically significant reductions in brain lesions on MRI, and all disability progression endpoints trended in fenebrutinib's favor. Roche presented the full FENhance data at the American Academy of Neurology meeting on April 22, 2026. Compared with teriflunomide, markers of active inflammation on MRI fell by 70.7% in FENhance 1 and 77.6% in FENhance 2. Disability progression was 20% and 13% lower on fenebrutinib, but neither difference was statistically significant.
The FENtrepid trial tested fenebrutinib against Ocrevus (ocrelizumab), which is currently the only approved treatment for primary progressive MS, in 985 patients over at least 120 weeks. According to the FENtrepid trial data, fenebrutinib was non-inferior to Ocrevus in delaying disability progression, meaning it worked about as well. Risk of progression was 12% lower than on Ocrevus, but that difference was not statistically significant, and the trial did not show fenebrutinib to be better than Ocrevus.
Fenebrutinib Safety Profile and Side Effects
No drug is without risks, and transparency matters. The fenebrutinib trials reported some safety signals that deserve attention.
Roche reported 7 deaths (0.9%) in the fenebrutinib arms of FENhance during the reporting period, compared with 1 (0.1%) in the teriflunomide arm, and 1 more death was seen after that period. The causes varied and occurred at different points during treatment. Further analyses are ongoing. In the FENtrepid study, the fatality rate was 1.4% in the fenebrutinib arm versus 0.2% in the Ocrevus arm; investigators assessed all cases as unrelated to treatment. Epidemiological research has established that people with MS already face higher mortality rates than the general population, but these numbers will be scrutinized closely.
On liver safety, there was 1 Hy's Law case (a marker for potential drug-induced liver injury) in the fenebrutinib arm and 1 in the teriflunomide arm of FENhance 1. Both were asymptomatic and resolved after stopping the drug. The FDA placed a partial clinical hold on the program in late 2023 after 2 people in the FENhance trials had liver enzyme rises with raised bilirubin. Both had no symptoms and recovered after stopping the drug. New U.S. enrollment in FENhance 1 was paused. U.S. participants who had taken fenebrutinib for more than 70 days kept taking it, while those with 70 days or less stopped. All 3 trials went on to report results. In FENtrepid, liver enzyme rises were more common on fenebrutinib than on Ocrevus (13.3% vs 2.9%), and all resolved after stopping the drug.
On September 30, 2026, Roche announced that the FDA had accepted its application for fenebrutinib in relapsing MS and primary progressive MS under priority review. Roche did not give a decision date. These safety findings are part of that review. For patients considering future treatment options, these are important conversations to have with a neurologist.
Why BTK Inhibitors Matter for MS Patients
MS treatment has come a long way over the past 2 decades. There are now more than 20 FDA-approved therapies for relapsing MS. Still, treatment has 2 major gaps that fenebrutinib could help fill.
The first is the lack of high-efficacy oral options. The most effective MS drugs currently available, like Ocrevus and Kesimpta, require injections or infusions. Many oral drugs exist, but they tend to be less potent. An oral pill that delivers high efficacy would simplify treatment for a lot of people.
The second is progressive MS. For patients with primary progressive MS, Ocrevus has been the only option since 2017. For the broader population of people whose MS is transitioning from relapsing to progressive, treatment options narrow significantly. Fenebrutinib's ability to cross the blood-brain barrier and target the chronic inflammation behind progression is the kind of mechanism the field has been looking for.
Roche submitted the data from all 3 Phase III studies, and the FDA accepted the application under priority review on September 30, 2026. If approved, fenebrutinib would represent a fundamentally new approach to treating MS, targeting the disease from both outside and inside the brain with a single oral medication.
Quick Reference: MS by the Numbers
MS is most commonly diagnosed between ages 20 and 40, making it one of the leading causes of neurological disability in young adults. According to MS epidemiological data, about 10-15% of people with MS are diagnosed with the primary progressive form, which involves a steady worsening of symptoms from the start rather than the relapse-remission pattern.