"An experimental drug preserved and even improved the walking ability of boys with Duchenne muscular dystrophy httphealth.nytimes.comhealthguidesdiseaseduchennemusculardystrophyoverview.htmlinlinenytclassifier in a clinical trial raising hopes that the first effective treatment for the disease may be on the horizon. Boys with the disease who received the highest dose of the drug had a slightly improved ability to walk after  weeks of treatment the drugs developer Sarepta Therapeutics announced httpinvestorrelations.sareptatherapeutics.comphoenix.zhtmlcpirolnewsArticleIDhighlight Wednesday. By contrast the boys who received a placebo suffered a sharp decline in how well they could walk. The drug called eteplirsen also appeared to restore levels of the crucial protein that muscular dystrophy httphealth.nytimes.comhealthguidesdiseasemusculardystrophyoverview.htmlinlinenytclassifier patients lack to about half of normal levels Sarepta said. I think this changes the entire playing field for muscular dystrophy said Dr. Jerry R. Mendell director of the gene therapy and muscular dystrophy programs at Nationwide Childrens Hospital in Columbus Ohio and the lead investigator in the trial. There are many caveats. The trial had only  patients with only four receiving the high dose and four the placebo and the data has not been reviewed by experts. It is also unclear how long the effects of the drug would last or if safety issues would arise with longer treatment. Also eteplirsen would be appropriate for only about  percent to  percent of Duchenne patients those with the particular genetic mutation the drug is meant to counteract. However a similar approach might work for some other mutations. Duchenne which affects as many as  Americans mainly boys and young men is the most severe common form of muscular dystrophy a disease made more prominent by years of Jerry Lewis telethons. Those with the disease make barely any dystrophin a protein necessary for muscles to function. Patients typically lose the ability to walk as teenagers and die by age . While steroids httptopics.nytimes.comtopnewshealthdiseasesconditionsandhealthtopicssteroidsindex.htmlinlinenytclassifier which reduce inflammation can slow progression of the disease they have undesirable side effects. Eteplirsen which Sarepta says has shown no side effects so far is vying with a similar drug being developed by GlaxoSmithKline to become the first medicine that works by directly countering the cause of the disease. Eteplirsen could also be the first drug to reach the market for Sarepta since it was founded  years ago. It changed its name recently from AVI BioPharma httptopics.nytimes.comtopnewsbusinesscompaniesavibiopharmaincindex.htmlinlinenytorg to distance itself from its underachieving past. Shares of Sarepta nearly tripled on Wednesday closing at .. And the stock had already roughly quadrupled since July when Sarepta announced some interim results from the study. The study measured how far the boys could walk in six minutes. Those who received the higher dose walked an average of  meters farther after  weeks of treatment than at the beginning of the trial a gain of about  percent. The boys in the placebo group walked  fewer meters at the end than at the beginning a decline of about  percent. One possible reason for skepticism is that two of the boys on a lower dose of the drug rapidly lost the ability to walk even though the level of dystrophin in their muscles increased substantially. Our columnist Andrew Ross Sorkin and his Times colleagues help you make sense of major business and policy headlines  and the powerbrokers who shape them. Top of Form Bottom of Form Top of Form While the company excluded those boys from its analysis as outliers the Food and Drug Administration might not do so. That could make it harder for the Sarepta to win approval for the drug based only on this small trial something the company hopes to do. If you wait and require this company to do another twoyear study a lot of these boys are going to be in a wheelchair Christopher Garabedian the Sarepta chief executive said in an interview. Patient groups may also put some pressure on the Food and Drug Administration to approve the drug quickly. But some also want Sarepta to make the drug available to more patients on a compassionate basis even before approval. Tenyearold Max Leclaire of Saxtons River Vt. who has been receiving the highest dose in the trial can now walk up stairs without having to pull himself up by the handrail according to his mother Jenn McNary. Hes no longer riding the handicap bus to school she said. But Ms. McNary said Sarepta had refused to provide the drug to Maxs yearold brother Austin who could not be in the trial because he already could not walk. Mr. Garabedian said Sarepta did not have the money or the manufacturing capacity to make the drug available outside of clinical trials. That would be the quickest path to insolvency he said. If eteplirsen gets to market it would come nearly three decades after the  discovery of the gene responsible for Duchenne. It would also represent a success after decades of setbacks for the technology eteplirsen uses called antisense which is a way of turning off specific genes. Eteplirsen actually turns off just one part of the dystrophin gene known as exon  which contains a mutation that in some patients stops production of dystrophin. By skipping over this exon muscle cells can produce an imperfect form of dystrophin that nonetheless is at least partly functional."