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with its design, was set up to enroll 19 boys into six different dose groups. As I mentioned, the results from the first four dose groups arrived in December—from the boys who got the AVI drug in concentrations of 0.5, 1, 2, and 4 milligrams per kilogram of body weight. Since the drug appeared safe at those low doses, AVI is now proceeding to study how well patients perform at two much higher doses—10 and 20 milligrams per kilogram of body weight.
That first batch of results will be important scientifically, but won’t mean a whole lot for patients who are suffering from the disease. That’s because the findings will focus on how patients did after they got weekly infusions of the AVI drug for just 12 weeks. Two weeks after that, biopsies will be taken from their bicep muscles to see how well a certain gene is being expressed, and how much dystrophin protein they are producing. Safety is the main goal.
The next step in analyzing the data will be even more important for AVI. By the end of September, AVI expects to have full results on how all 19 patients did after about six months (26 weeks) following their initial dose. Those longer-term results will include precious information about safety, how long the drug lasts in the body, and importantly, a measurement of how far the patients can walk in six minutes.
That six-minute walk test is considered the gold standard measurement of success for a muscular dystrophy treatment, says AVI chief medical officer Steve Shrewbury. So if AVI can show these boys are able to walk longer distances than they otherwise could, or at least that increasing doses appear correlated with better walking, this could be very valuable information for the company as it considers how to design the next round of trials. It’s likely that a pivotal clinical trial would have six-minute walk as one of the main goals, so the initial small study could serve as a valuable template for the bigger one.
“It would be pretty good if we can get a positive readout on the six-minute walk test,” Shrewsbury says. “We might only get a positive result at one or two of the doses if we’re lucky at the end of six months. The numbers will be small. We’ll have to see what the data says.”