BASEL — September 8, 2026

Novartis announced that its global Phase III HARBOR study of delpacibart etedesiran (del-desiran) in people living with myotonic dystrophy type 1 (DM1) did not meet its primary endpoint, representing a setback for the company’s clinical development program in a neuromuscular disease with significant unmet medical need. The randomized, double-blind, placebo-controlled study evaluated del-desiran over 54 weeks in approximately 150 participants, with video hand opening time (vHOT) serving as the primary measure of hand myotonia. Novartis reported that the study did not demonstrate a statistically significant improvement versus placebo on vHOT, although evidence of clinical activity was observed in secondary endpoints and exploratory analyses. Safety findings were generally consistent with previously reported data. The company said it will conduct a comprehensive analysis of the full HARBOR dataset and engage with health authorities before determining the next development steps for del-desiran.

Del-desiran Program Enters Strategic Review

Novartis is now evaluating the complete HARBOR dataset to determine the appropriate development path for del-desiran, maintaining a focus on potential clinical activity observed beyond the primary endpoint. The decision will be important for the company’s broader strategy in DM1, a progressive multisystem neuromuscular disease for which there are currently no approved disease-modifying treatment options. Del-desiran is an investigational antibody oligonucleotide conjugate (AOC) therapy designed to target disease-causing DMPK messenger RNA. The program was obtained as part of Novartis’ acquisition of Avidity Biosciences, which added three AOC therapies to the company’s neuromuscular pipeline. Del-desiran previously received Orphan Drug, Fast Track and Breakthrough Therapy designations from the U.S. FDA, as well as Orphan Medicinal Product Designation in the European Union. The HARBOR outcome will therefore factor into Novartis’ assessment of how the acquired AOC platform should be advanced in DM1 and how additional clinical evidence may inform future regulatory discussions.

AOC Pipeline Advances Beyond DM1

Despite the HARBOR setback, Novartis continues to advance other AOC programs across neuromuscular diseases, providing an important counterpoint to the del-desiran development update. The company said the FDA has granted Priority Review for delpacibart zotadirsen (del-zota) in Duchenne muscular dystrophy patients with mutations amenable to exon 44 skipping, following the company’s accelerated approval filing. Novartis is also planning an FDA meeting regarding delpacibart braxlosiran (del-brax) in facioscapulohumeral muscular dystrophy (FSHD), supported by positive Phase I/II biomarker data. These programs represent key components of Novartis’ strategy to expand its neuromuscular pipeline through AOC-based medicines. The continued regulatory and clinical progress of del-zota and del-brax could help demonstrate the broader potential of the technology even as the company reassesses the next steps for del-desiran following the HARBOR results.

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Novartis Maintains Broader Growth Strategy

Novartis said it remains committed to neuromuscular innovation while maintaining its 5–6% five-year sales CAGR guidance for 2025–2030. The company’s neuroscience strategy spans established areas such as spinal muscular atrophy and multiple sclerosis while expanding into neuroimmunology, neurodegeneration, and neuromuscular diseases. The HARBOR outcome highlights the development risks associated with advancing treatments for complex neurological disorders, but Novartis indicated that it will continue analyzing the available evidence before making a final decision on del-desiran. For the company, the immediate priorities include completing the HARBOR data assessment, engaging regulatory authorities, and progressing programs with clearer development momentum. The Priority Review for del-zota and planned FDA interaction for del-brax provide continued pipeline activity within Novartis’ AOC portfolio, keeping neuromuscular development strategically important despite the Phase III DM1 setback..

Source:Novartis press release