Here's how: Sarepta completed enrollment and dosing of patients within two weeks of the company's mid-August 2011 press release announcing that the trial was underway. Although everyone started active drug after 24 weeks, the company didn't reveal any details about the blinded portion of the study until early April 2012 -- roughly 33 weeks after the first patients were dosed. At that time, management spoke with both the contract research organization conducting the trial and Dr. Jerry Mendell at Nationwide Children's Hospital, the lead investigator. Upon return for the 36-week visit, patients were first directed -- as usual -- to the physical therapist for the 6MWT. Investigators still hadn't told the physical therapists who had received what, thereby eliminating one possible source of bias. Patients learned treatment assignment details upon meeting with the investigator at end of the day. Although the company hasn't rigorously audited each case report, it seems plausible that Sarepta's 36-week data were blinded. That would enhance the quality of the results we've already seen and increase my confidence that the upcoming 48-week data will also be positive. There remain several important risks to the Sarepta story, including the fact that scaling up manufacturing of eteplirsen will delay the start of Phase III studies -- if required by the FDA -- until early 2014. If this happens, FDA approval may not occur until the second half of 2015. Importantly, bulls expect Sarepta to vie for accelerated approval based on the Phase IIb results. That's possible, but it would require an exceedingly tight correlation between 6MWT and dystrophin levels at 48 weeks. Even assuming accelerated approval, expanding eteplirsen manufacturing capacity to commercial scale will take time. In an absolute best-case scenario, eteplirsen could be launched in mid-2014. That puts Sarepta's development and regulatory timeline roughly in-line with Prosensa and GlaxoSmithKline ( GSK), which will report Phase III results for GSK-2402968 -- a similar exon 51 skipping drug for the treatment of DMD -- in the second half of 2013. Sarepta's 48-week data will be a landmark event in the company's long history that will either meaningfully de-risk eteplirsen or debunk the hype. The extended blinding in Sarepta's Phase IIb study increases my confidence that the eteplirsen data are real, although I would still recommend that investors size long positions cautiously. Disclosure: Sadeghi has no positions in any of the stocks mentioned in this article. Follow Nathan Sadeghi-Nejad on Twitter.