Novartis shares plunge 10% after experimental neuromuscular drug fails late-stage trial

Novartis shares plunged over 10% on September 8, 2026, after its experimental drug del-desiran failed the Phase 3 HARBOR trial for myotonic dystrophy type 1. The drug, acquired in a $12 billion deal for Avidity Biosciences, failed to improve hand-opening times compared to a placebo. This setback is Novartis's third major clinical blow in a week, following the failure of cardiovascular drug pelacarsen and the suspension of its rap-cel cell therapy trials due to patient deaths, casting doubt on its 2030 growth targets.

Del-desiran trial failure

• ▪Novartis announced on September 8, 2026, that its experimental drug del-desiran failed to meet its primary endpoint in the Phase 3 HARBOR clinical trial.
• ▪Novartis stated it is evaluating the full HARBOR dataset and will engage with health authorities to determine the development path for del-desiran.
• ▪The Phase 3 HARBOR trial of del-desiran failed to show a significant improvement compared with a placebo in video hand opening time for patients with myotonic dystrophy type 1.

Recent Novartis setbacks

• ▪Novartis announced in September 2026 that a late-stage trial of its experimental multiple sclerosis drug remibrutinib delivered a clinically meaningful delay in disability progression.
• ▪Novartis announced in September 2026 that its cardiovascular drug pelacarsen failed to reduce the risk of cardiovascular events in a late-stage clinical trial.
• ▪Novartis paused eight clinical trials of its experimental cell therapy rap-cel in September 2026 after three patients died.

Avidity Biosciences acquisition

• ▪Barclays analysts stated that the failure of del-desiran casts doubt on the Avidity Biosciences acquisition and Novartis's ability to offset upcoming patent expiries through mergers and acquisitions.
• ▪Novartis acquired Avidity Biosciences for approximately $12 billion in 2025, adding three antibody oligonucleotide conjugate therapies, including del-desiran, to its neuromuscular pipeline.

Stock price decline

• ▪The stock drop on September 8, 2026, put Novartis shares on track for their worst trading day since March 2020.
• ▪Novartis shares dropped by as much as 10% to 10.5% on September 8, 2026, following the announcement of the del-desiran trial failure.

Growth outlook doubts

• ▪Barclays analysts noted that del-desiran and pelacarsen represented approximately $5 billion in risk-adjusted peak sales opportunities for Novartis.
• ▪Novartis stated on September 8, 2026, that it still expects its average annual sales to grow by 5% to 6% until 2030.
• ▪Jefferies analysts stated that Novartis's 5% to 6% growth target will likely be perceived as unattainable without further mergers and acquisitions.

Myotonic dystrophy type 1

• ▪Myotonic dystrophy type 1 symptoms include difficulty relaxing muscles, which clinical trials measure by timing how long it takes patients to open their hands after gripping.
• ▪Myotonic dystrophy type 1 is a rare genetic neuromuscular condition and muscle-wasting disorder that causes progressive muscle stiffness and weakness.