Sarepta Therapeutics Inc. shares rocketed 55.6% in extremely heavy Tuesday morning trade after the company reported positive early results from a phase 1/2a gene therapy clinical trial for three patients with the rare disease Duchenne muscular dystrophy. The three patients, the first ones enrolled in the study, showed “robust” expression of micro-dystrophin, a shortened version of the dystrophin gene used in gene therapy, Sarepta said. Individuals with DMD have a mutation on their dystrophin gene and thus cannot produce the protein dystrophin, which is critical for muscular development. Robust levels of micro-dystrophin were also seen in all three post-treatment biopsies, the company said, and patients had significant decreases in an enzyme connected to muscle damage and typically seen in high levels among DMD patients. If the results continue, Sarepta’s gene therapy, called AAVrh74.MHCK7, could “represent an unprecedented advancement in the treatment of DMD,” said Dr. Jerry Mendell, the study’s principal investigator. “I have been waiting my entire 49-year career to find a therapy that dramatically reduces CK levels and creates significant levels of dystrophin,” he said, referring to serum creatine kinase, the enzyme associated with muscle damage. The biotech, which is best known for its DMD therapy Exondys 51, announced big ambitions in gene therapy and gene editing earlier this year, and has four such programs in the works. Sarepta shares have surged 104% over the last three months, compared with a 1.4% rise in the S&P 500 and a 0.2% rise in the Dow Jones Industrial Average .