Swiss pharmaceutical heavyweight Novartis faced a turbulent trading session on Tuesday as its shares tumbled sharply following the disclosure that its experimental drug for muscular dystrophy, del-desiran, failed to meet its primary endpoint in a late-stage trial. The stock, which lost as much as 9.4% during the day, is now on track for what could be its worst single-day performance since going public.

The latest disappointment marks the company's third clinical trial setback within a single week, sparking a wave of investor sell-offs. Just days earlier, another Novartis medication aimed at reducing cardiovascular event risks had also failed in a late-stage study. A week prior, the company announced it had paused eight clinical trials for its experimental cell therapy, rap-cel, following the deaths of three trial participants.

Details of the Muscular Dystrophy Trial

Novartis revealed that the global Phase III HARBOR study, which evaluated del-desiran in patients with myotonic dystrophy type 1, did not demonstrate a statistically significant improvement in hand-opening time compared to a placebo. The trial also confirmed that the therapy failed to significantly accelerate the speed of hand opening relative to the placebo group.

In a press release, the company stated: "We are conducting a thorough evaluation of the full HARBOR study data and will engage with regulatory authorities to determine the most appropriate next steps for the del-desiran development program."

Del-desiran is an antibody-oligonucleotide conjugate therapy. Last year, Novartis acquired Avidity Biosciences for approximately $12 billion, bringing this drug along with two other similar candidates into its neuromuscular disease research pipeline.

Shreeram Aradhye, Novartis' Head of Research and Development and Chief Medical Officer, issued a statement on Tuesday saying: "Developing therapies for complex conditions such as myotonic dystrophy type 1 is inherently challenging, and setbacks are part of the scientific process. We will continue to comprehensively assess all data from the HARBOR study, remain committed to identifying the optimal development pathway for del-desiran, and continue advancing innovative treatment options for patients with myotonic dystrophy and other severe neuromuscular diseases."