Initial results from the Phase III trial of del-desiran in Steinert disease

In September 2026, Novartis announced the initial results of the Phase III HARBOR trial evaluating delpacibart andedesiran (del-desiran or AOC 1001) in type 1 myotonic dystrophy (DM1).

  • The trial’s primary endpoint was not met: among the 150 participants aged between 16 and 65, del-desiran did not significantly improve hand myotonia compared with placebo after approximately one year of treatment.
  • Signs of activity were reportedly observed for certain secondary endpoints (grip strength, muscle strength, walking/running over 10 metres, and the DM1-ACTIVc questionnaire on activities of daily living). These data are currently being analysed.
  • The data on the product’s tolerability are generally favourable.

Novartis plans to hold discussions with the health authorities before deciding on the next steps.