Shares of Sarepta Therapeutics soared more than 50 percent Tuesday after the company presented preliminary data for its experimental treatment for patients with Duchenne muscular dystrophy.

The rare genetic disease causes muscle wasting and can be fatal before patients turn 30. Symptoms usually start in early childhood, usually between 3- and 5-years old. It primarily affects boys. But in rare cases can affect girls.

Sarepta shared results from three children to receive the gene therapy in a phase 1/2a clinical trial.

Creatine kinase is an enzyme found within muscle cells and can leak into the bloodstream when damage has occurred in the muscle. Elevated levels of it can indicate someone has Duchenne muscular dystrophy, or DMD.

Patients that received Sarepta’s drug showed an average reduction of more than 87 percent in their creatine kinase levels on day 60.

The treatment also produced robust levels of dystrophin, a protein found in muscles that’s used for movement. The results “meaningfully beat even the highest of expectations,” J.P. Morgan analyst Anupam Rama wrote in a note to clients.

“I have been waiting my entire 49-year career to find a therapy that dramatically reduces CK levels and creates significant levels of dystrophin,” Dr. Jerry Mendell of Nationwide Children’s Hospital said in a statement. “Although the data are early and preliminary, these results, if they persist and are confirmed in additional patients, will represent an unprecedented advancement in the treatment of DMD.”

Sarepta closed Monday with a market value of $6.9 billion, according to FactSet. That rocketed higher to about $10.6 billion during Tuesday’s surge.

The company’s shares have gained nearly 200 percent this year.

Solid Biosciences is also developing a gene therapy for DMD. Its shares surged 82 percent Tuesday, one day after the Food and Drug Administration took the company’s program off clinical hold.

Solid has treated just one patient and said Monday it expects to have data in the second half of 2019.

The NASDAQ’s biotech index was up almost 1.2 percent on Tuesday, on pace for its best day since June 6 when it gained 1.25 percent.

-CNBC’s Meg Tirrell contributed to this report

A press release summarizing Sarepta’s results follows

CAMBRIDGE, Mass.,June 19, 2018 (GLOBE NEWSWIRE) –Sarepta Therapeutics, Inc. (NASDAQ:SRPT), a commercial-stage biopharmaceutical company focused on the discovery and development of precision genetic medicine to treat rare neuromuscular diseases, announced that at the Company’s R&D Day,Jerry Mendell, M.D. of Nationwide Children’s Hospital presented positive preliminary results from its Phase 1/2a gene therapy clinical trial assessing AAVrh74.MHCK7.micro-Dystrophin in individuals with Duchenne muscular dystrophy (DMD). Dr. Mendell presented the following preliminary data on the first three patients enrolled in the study:

*All patients showed robust expression of transduced micro-dystrophin, which is properly localized to the muscle sarcolemma, as measured by immunohistochemistry. Mean gene expression, as measured by percentage of micro-dystrophin positive fibers was 76.2% and the mean intensity of the fibers was 74.5% compared to normal control.

*All post-treatment biopsies showed robust levels of micro-dystrophin as measured by Western blot, with a mean of 38.2% compared to normal utilizing Sarepta’s method, or 53.7% compared to normal pursuant to Nationwide Children’s quantification of Sarepta’s method that adjusts for fat and fibrotic tissue.

*A mean of 1.6 vector copies per cell nucleus was measured in patients, consistent with the high micro-dystrophin expression levels observed.

*All patients showed significant decreases of serum creatine kinase (CK) levels, with a mean reduction of CK of over 87% at Day 60. CK is an enzyme associated with muscle damage and patients with DMD uniformly exhibit high levels of CK. Indeed, significantly elevated CK is often used as a preliminary diagnosis tool for DMD, which is then followed by confirmatory genetic testing.

*No serious adverse events (SAEs) were observed in the study. Two patients had elevated gamma-glutamyl transferase (GGT) that resolved with increased steroids within a week and returned to baseline levels. There were no other significant laboratory findings. Patients had transient nausea generally during the first week of therapy coincident with increased steroid dosing.

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Sarepta Therapeutics shares soar 50% on positive preliminary results for muscular dystrophy gene therapy