An experimental gene therapy designed to treat Duchenne muscular dystrophy has produced exciting preliminary results in a Phase 1/2a clinical trial. Sarepta Therapeutics, the company behind the therapy’s development, announced the results. You can read the full article here, at Stat News, and the full press release here, at Globe Newswire.

Duchenne muscular dystrophy (DMD) is a serious genetic disease that mainly affects boys. People with DMD do not have adequate levels of the protein dystrophin, and, as a result, lose muscle strength and function. It is estimated that 300,000 people are affected by the disorder worldwide.

The gene therapy trial produced robust levels of a shortened, micro version of dystrophin in patients. The results also showed a reduction in serum creatine kinase (CK) levels of, on average, over 87% after sixty days. Dr. Mendell, the study’s principle investigator, said

“I have been waiting my entire 49-year career to find a therapy that dramatically reduces CK levels and creates significant levels of dystrophin.”

The clinical trial was carried out on three boys with DMD, aged 4, 5, and 6. Each boy received an injection of a micro-dystrophin gene therapy. Dystrophin is a protein that is necessary for muscle function. People with DMD have low levels of dystrophin, and this contributes to difficulty moving. Since the full dystrophin gene is too large to be delivered through gene therapy (it’s the largest gene in the body), researchers shortened the gene to contain the most important parts for muscle function, creating what they call ‘micro-dystrophin’. The boys have been followed up for three months, and muscle biopsies were taken during follow up so that the effects of the treatment could be better understood.

It was found that the micro-dystrophin levels increased, on average, by 38% based on a Western blot test using Sarepta’s method. However, this figure increased if another technique was used. Stat News reports Doug Ingram, president of Sarepta, as describing this result as about four times better than expected.

In addition, the levels of CK were shown to fall substantially. The mean reduction in CK levels was 87% after sixty days. CK is an enzyme that is released when muscles are damaged and is often used as one method of identifying DMD. According to Stat News, this is the first treatment for DMD to lower CK levels.

However, there are still many questions that need to be answered about this experimental gene therapy, known officially as AAVrh.74.MHCK7.micro-Dystrophin. This study was carried out on just three boys, and it is unclear whether the results will be replicated in more patients. The dystrophy gene therapy also used a shortened form of the gene, and the full effects of that remain poorly understood. Furthermore, a long-term follow-up hasn’t been completed, and it’s not known if the results are stable and will persist. Although more research is needed, at this point, the results are very encouraging.

Sarepta is now planning on expanding the clinical trial to include more patients and implement a placebo condition. The company will discuss with the FDA whether, following this second study, it will be possible to file for marketing approval.

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