Novartis has reported strong Phase 3 results for remibrutinib, an oral multiple sclerosis pill — and the data may defuse a safety problem that has dogged its entire drug class.
In two large Phase 3 trials in relapsing MS, remibrutinib showed superiority over Aubagio (teriflunomide), a widely used oral MS drug, reducing annual relapse rates and inflammatory brain lesions with a “clinically meaningful” effect on disability progression. Novartis shares rose more than 4%.
Why BTK inhibitors matter in MS
Bruton’s tyrosine kinase is a signalling enzyme inside B cells, and B-cell-depleting antibodies are among the most effective MS therapies available — so a drug acting on B cells has an established rationale.
What makes BTK inhibitors distinctive is a second target. BTK is also active in microglia, the brain’s resident immune cells, and small-molecule BTK inhibitors can cross into the central nervous system. Antibody therapies cannot meaningfully do this — they deplete B cells in the circulation but have limited access to the brain itself.
The problem the class is aimed at
That distinction matters because of what current MS drugs fail to address.
Existing therapies are effective at preventing relapses — discrete attacks of new inflammation. But many patients accumulate disability steadily even when relapses stop, driven by chronic low-grade inflammation within the central nervous system, in which microglia are heavily implicated. This smouldering process, rather than relapses, increasingly appears to determine long-term outcomes.
A drug reaching microglia inside the brain could in principle address the part of MS that current treatments largely do not touch. That is why the class attracted so much investment, and why its repeated setbacks were so disappointing.
The safety problem
Crucially, remibrutinib was not associated with the liver-related side effects that other BTK inhibitors in MS have encountered — a problem that has stalled or sunk competing drugs.
Liver injury has been the class’s recurring obstacle. One competitor programme was placed under regulatory restriction after cases of liver injury emerged; another failed to demonstrate efficacy in Phase 3 outright. For a chronic therapy taken for decades by patients who are often young and otherwise well, hepatotoxicity is close to disqualifying — it demands ongoing monitoring and creates a risk that is hard to justify against alternatives that do not carry it.
Remibrutinib arrives with a relevant advantage: it is already approved for chronic hives, meaning a body of human safety experience exists outside MS.
The comparator question
One caveat should temper enthusiasm. The trials compared remibrutinib against teriflunomide, which is widely used and convenient but is not among the most effective MS therapies available.
The highly effective end of the field consists of B-cell-depleting antibodies and similar agents that substantially outperform teriflunomide on relapse rates. Beating teriflunomide establishes that a drug works; it does not establish where it sits relative to the treatments many neurologists now reach for first.
This is a common and defensible design choice — an active comparator trial against a marketed oral drug is ethically straightforward and regulatorily sufficient. But the clinically interesting question, unanswered here, is how remibrutinib compares with a B-cell-depleting antibody, particularly on the disability progression it is theoretically better placed to address.
The disability signal
The reported “clinically meaningful” effect on disability progression is the most consequential element, and the least specified.
Relapse reduction is comparatively easy to achieve and easy to measure. Disability progression is the harder endpoint, requires longer follow-up, and is what patients care about most. Whether that effect reflects preventing relapse-driven disability or genuinely slowing the independent progression that BTK inhibitors are meant to target is the question the full data will need to answer.
Commercial stakes
Analysts project peak MS sales could exceed $3 billion. That reflects both the size of the MS market and the value of an oral drug in a category where the most effective options require infusion or injection.
Convenience matters more in MS than in many diseases: patients are frequently diagnosed young and treated for decades, and a daily pill with comparable efficacy to an infused antibody would be commercially formidable.
What remains
These are topline results. Full data have not been presented, and the absence of liver signals in a trial is not the same as absence in a broad population over years — hepatotoxicity in this class has sometimes emerged with wider exposure.
What an oral option changes for patients
Beyond efficacy, route of administration carries unusual weight in multiple sclerosis, and it explains much of the commercial interest.
MS is typically diagnosed in people in their twenties and thirties who will be treated for the rest of their lives. The most effective current therapies are given by infusion, requiring periodic visits to an infusion centre, or by regular injection. Over decades, that is a substantial and permanent imposition on the working and family lives of people who are often otherwise well.
Access matters too. Infused therapies require infrastructure that is unevenly distributed, particularly outside major centres and outside wealthy health systems, and they carry administration costs on top of drug costs. A daily tablet with comparable efficacy removes those constraints entirely — which is why an oral drug that could genuinely compete with B-cell-depleting antibodies would reshape treatment patterns rather than simply adding another option.
Novartis plans to take the results to regulators. If the liver profile holds and the disability effect proves real, remibrutinib would be the first BTK inhibitor to deliver what the class has promised for years. Clinical and business news, not medical or investment advice.