Roche Holding AG shares dropped after a trial of its gene therapy for Duchenne muscular dystrophy did not meet the main goal in a study, a setback for the Swiss drugmaker and its partner Sarepta Therapeutics Inc.

The stock fell as much as 2.9% in Zurich trading. Sarepta disclosed the findings late Monday, saying patients improved in an ambulatory assessment, yet the change wasn’t great enough to hit the clinical trial’s target.

Disappointments are inevitable in scientific research, but Roche has had an unusual number of clinical-trial stumbles lately, including high-profile projects in cancer and Alzheimer’s disease.

The trial results show the medicine called Elevidys modifies the trajectory of the disease across age groups, according to Sarepta.

The therapy secured accelerated US approval in June, a regulatory shortcut that allows companies to market medications before completing definitive trials in cases where patients have few or no treatment options.

The US Food and Drug Administration cleared the medicine only for patients between the ages of 4 and 5, the group that saw the biggest benefit in clinical trials. The decision struck a middle ground after questions arose about the treatment’s effectiveness.

The approval was the first ever for a gene therapy for Duchenne muscular dystrophy. The inherited condition primarily affects boys, causing their muscles to weaken over time. Most people with the condition die by their early 20s.

Sarepta on Monday said it plans to ask the FDA to expand the labeled indication to treat older patients. The stock was halted after US markets closed.

The company plans to charge $3.2 million for the one-time treatment, but it has said the net price will likely be about 20% lower after discounts. Roche holds the rights to sell the drug outside of the US.