BASEL, Switzerland, June 11, 2026
Novartis has announced positive results from the FORTITUDE Phase I/II clinical study evaluating delpacibart braxlosiran (del-brax) in patients with facioscapulohumeral muscular dystrophy (FSHD), a rare and progressive neuromuscular disorder with no approved disease-modifying treatments. The study successfully met its primary biomarker endpoint and key secondary endpoint, reinforcing the potential of del-brax to become the first disease-modifying therapy for FSHD. The findings strengthen Novartis’ expanding neuromuscular disease portfolio and support the ongoing global Phase III development program.
Phase I/II Trial Meets Key Biomarker Endpoints
The biomarker cohort of the FORTITUDE Phase I/II trial demonstrated significant reductions in KHDC1L (cDUX), a biomarker directly linked to DUX4 activity, and creatine kinase, a widely recognized indicator of muscle damage. These results provide strong evidence that del-brax is successfully engaging its intended molecular target while simultaneously reducing muscle injury associated with FSHD progression. According to Novartis, the safety profile observed in the study remained consistent with previously reported findings, further supporting the therapy’s clinical development pathway. The positive outcomes replicate earlier dose-escalation data and validate the dosing strategy selected for the ongoing Phase III study, marking a critical milestone in the pursuit of a transformative treatment option for patients living with this debilitating disease.
Innovative RNA Therapeutic Targets Root Cause of Disease
Del-brax represents a new generation of antibody oligonucleotide conjugate (AOC) therapeutics, combining the targeting precision of monoclonal antibodies with the gene-silencing capabilities of RNA-based medicines. The therapy is specifically designed to suppress DUX4, the aberrantly expressed gene recognized as the underlying driver of FSHD pathology. By enabling targeted delivery of small interfering RNA (siRNA) directly into muscle cells, the AOC platform addresses a longstanding challenge in neuromuscular drug development.
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Novartis highlighted that del-brax is currently the only investigational therapy demonstrating disease-modifying potential in clinical studies for FSHD. The therapy has already received FDA Orphan Drug Designation, FDA Fast Track Designation, and EMA Orphan Drug Designation, underscoring the significant unmet medical need in this patient population and the regulatory recognition of its therapeutic promise.
Phase III Development Advances as Novartis Expands Neuromuscular Pipeline
Building on the encouraging Phase I/II data, Novartis plans to engage with global regulatory authorities while continuing enrollment in the FORTITUDE-3 Phase III trial, a randomized, double-blind, placebo-controlled study evaluating the efficacy and safety of del-brax in approximately 200 patients aged 16 to 70 years. The trial will assess clinically meaningful functional outcomes, including quantitative muscle testing and mobility measures, alongside patient-reported outcomes and biomarker analyses. Del-brax became part of the Novartis neuroscience portfolio through the company’s acquisition of Avidity Biosciences in early 2026, bringing alongside it additional late-stage neuromuscular programs targeting myotonic dystrophy type 1 (DM1) and Duchenne muscular dystrophy (DMD).
Together, these assets significantly strengthen Novartis’ position in neuromuscular medicine and reinforce its commitment to developing innovative therapies for patients affected by rare genetic disorders. With FSHD impacting an estimated 45,000 to 87,000 individuals across the United States and Europe, the successful advancement of del-brax could represent a landmark achievement in the treatment of progressive muscular dystrophies and a major step toward addressing a disease that currently lacks approved therapeutic options.
Source: Novartis press release
