Novartis' del-desiran fails primary endpoint in phase 3 Harbor trial for myotonic dystrophy type 1

Novartis announced that its experimental therapy del-desiran did not meet the primary endpoint in the phase 3 Harbor trial, which evaluated improvement in video hand opening time in patients with myotonic dystrophy type 1. The study involved 159 participants and showed no statistically significant benefit over placebo.

The drug was a centerpiece of Novartis' $12 billion acquisition of Avidity Biosciences, and analysts had described success in this trial as crucial for validating the deal. The failure follows a mixed set of readouts for Novartis this year, including a win for Rhapsido in multiple sclerosis and a setback for pelacarsen in a cardiovascular study.

The negative result raises questions about del-desiran's future contribution to Novartis' pipeline and long‑term sales outlook, as investors and analysts had been watching the Harbor readout closely for clues about the company's growth beyond 2030.