Multiple Sclerosis Clinical Trials 2026: New DMTs, Remyelination & Progressive MS

MS treatment has been transformed over 30 years — from interferon beta-1b as the only option in 1993 to more than 20 approved disease-modifying therapies across injectable, oral, and infusion categories. The challenge for patients in 2026 isn't the absence of treatment options; it's the complexity of choosing among them, the question of when to escalate to higher-efficacy therapy, and the sobering reality that all these approved drugs work primarily for relapsing MS. For the approximately 15% of patients with primary progressive disease, and the larger group with secondary progressive disease where relapses have stopped but disability continues to accumulate, current DMTs offer little. That's where the trial pipeline is most important — and where the BTK inhibitor data from HERCULES represents what may be the first meaningful advance for progressive MS in years.

BTK Inhibitors: Why This Class Is Different

Bruton's tyrosine kinase inhibitors represent the most conceptually significant new drug class for MS in over a decade — and the reason comes down to biology. Every approved MS DMT works primarily on peripheral immune cells: they reduce circulating lymphocytes, prevent lymphocyte trafficking across the blood-brain barrier, or deplete B cells in the bloodstream. What they don't do well: access CNS-resident immune cells.

BTK inhibitors penetrate the CNS and act directly on two populations that are thought to drive progressive disability: B cells within the brain parenchyma (which standard anti-CD20 antibodies like ocrelizumab don't reach well), and microglia — the brain's resident macrophage-like cells that sustain smoldering neuroinflammation in progressive MS through BTK-dependent activation. This dual peripheral and central action is the theoretical basis for why BTK inhibitors might work where other drugs have failed.

Four BTK inhibitors are in Phase 3 MS trials:

• Tolebrutinib (Sanofi): HERCULES trial for non-relapsing secondary progressive MS — the most important result of this generation of progressive MS trials. Tolebrutinib showed a statistically significant delay in 6-month confirmed disability worsening vs. placebo. This is the first positive Phase 3 result in NRSPMS — a population that has had no meaningful treatment advance. GEMINI trials are testing tolebrutinib in relapsing MS simultaneously. The drug carries a boxed warning for drug-induced liver injury (DILI), which has required close monitoring protocols and temporarily paused enrollment in some trials.
• Fenebrutinib (Roche): FENhance 1 and 2 trials in relapsing MS, PPMS trial ongoing. Fenebrutinib is a non-covalent BTK inhibitor — unlike the covalent ibrutinib-generation inhibitors, it may have a cleaner BTK selectivity profile with less off-target kinase inhibition. Phase 3 results expected 2026.
• Evobrutinib (Merck): Phase 3 in relapsing MS — the Evolution trials. Earlier Phase 2 showed reduced new MRI lesion activity vs. placebo and non-inferiority to teriflunomide at higher doses. Hepatotoxicity signals have been observed across the BTK inhibitor class.
• Orelabrutinib (InnoCare): Phase 3 in RRMS and PPMS. Primarily being developed for Asian markets but with global trial sites.

Remyelination: Repairing What MS Has Broken

This is arguably the most important conceptual advance in MS research — the recognition that reducing new lesion formation isn't enough. Patients accumulate neurological disability from existing demyelinated lesions where axons are exposed and vulnerable, and from progressive axonal loss in chronic lesions. Remyelination therapy aims to activate oligodendrocyte precursor cells (OPCs) to rebuild the myelin sheath around demyelinated axons — potentially restoring function rather than just preventing further loss.

The challenge is that in chronic MS lesions, OPCs are present but fail to differentiate into mature myelinating oligodendrocytes — they're blocked by inhibitory signals in the lesion microenvironment. Several agents target different parts of this block:

• PIPE-307 (Contineum Therapeutics): M1 muscarinic acetylcholine receptor antagonist. Blocking M1 signaling promotes OPC differentiation into mature oligodendrocytes. Phase 2 results reported in 2025 showed MRI magnetization transfer ratio improvements — a validated surrogate for remyelination — in a subset of patients. The effect was modest but the signal was real, and Phase 3 planning is underway.
• Opicinumab (Biogen, anti-LINGO-1 antibody): LINGO-1 is an inhibitory signal that blocks OPC maturation. Completed Phase 2 (SYNERGY trial) showed no significant effect on overall disability outcomes but demonstrated remyelination signals in a specific patient subgroup (early active MS, measured by visual evoked potential latency). Biogen is exploring patient enrichment strategies before Phase 3.
• Clemastine (antihistamine repurposed): Phase 2 data from UCSF showed clemastine improved visual evoked potential latency in patients with chronic optic nerve demyelination — a direct measure of remyelination. An inexpensive, widely available antihistamine that promotes OPC differentiation. Phase 3 planning is ongoing; the challenge is finding a commercial sponsor for a generic drug.

Stem Cell Approaches: HSCT and Mesenchymal Stem Cells

Autologous hematopoietic stem cell transplantation (AHSCT) represents the most aggressive available intervention in MS — harvesting the patient's own stem cells, using high-dose chemotherapy to ablate the pathological immune system, and reinfusing stem cells to allow immune reconstitution. The reconstituted immune system lacks the autoreactive programming of the original, and in highly active relapsing MS, this "immune reset" can produce long-term remission.

The MIST trial (published 2019 in JAMA) was the definitive Phase 3 comparison: AHSCT vs. best available DMT in patients with highly active RRMS who had failed at least one prior DMT. At 5 years, 11% of AHSCT patients vs. 68% of DMT patients had experienced treatment failure. Treatment-related mortality with AHSCT was 0% in this carefully selected trial population at specialized centers. AHSCT is now offered at several specialized centers and is considered standard care for selected highly active RRMS patients who fail high-efficacy DMTs — though access remains highly limited and patient selection (EDSS, organ function, age) is critical.

Mesenchymal stem cell (MSC) therapy is a distinct approach — MSCs are infused IV without the preceding ablative chemotherapy, and the proposed mechanism is immunomodulatory and neuroprotective rather than immune reset. Phase 2 trials (MESEMS) are ongoing; MSC therapy is substantially less toxic than AHSCT and potentially applicable to progressive MS, though its efficacy profile is also substantially less dramatic in current data.

Finding MS Trials in 2026

ClinicalTrials.gov searches for "multiple sclerosis" with Recruiting status return over 300 active studies. The National MS Society (nationalmssociety.org) and MS Society of Canada both maintain trial-matching tools. Key eligibility variables that determine which trials you qualify for: MS subtype (RRMS, SPMS with or without activity, PPMS — these categories are often specifically defined in trial eligibility criteria); EDSS disability score; current and prior DMT use (most trials require a washout period after stopping high-efficacy therapies, particularly after alemtuzumab or AHSCT); time since last relapse; recent MRI lesion activity; and NfL biomarker status (increasingly required for progressive MS trials as an inclusion criterion or stratification variable).