Novartis's del-desiran misses its endpoint in myotonic dystrophy

Novartis said on 8 September 2026 that the Phase III HARBOR study of delpacibart etedesiran, known as del-desiran, did not demonstrate a statistically significant improvement over placebo on its primary endpoint in myotonic dystrophy type 1.

That endpoint was video hand opening time, a measure of hand myotonia the trial treated as novel. About 150 participants were randomised to del-desiran or placebo, dosed every eight weeks across 54 weeks. Novartis reported evidence of clinical activity in secondary endpoints and exploratory analyses, naming hand grip strength and a quantitative muscle testing total score, the DM1-Activ measure of daily activities, and a ten-metre walk and run test. Safety was described as generally consistent with data reported previously.

Del-desiran is an antibody oligonucleotide conjugate. Novartis says it is one of three therapies of that class added to its neuromuscular pipeline through the company’s acquisition of Avidity Biosciences.

The company says it is evaluating the full HARBOR dataset and will engage health authorities to determine a development path for the drug.