Sarepta Therapeutics (SRPT) went from the front-runner to “basically a standalone” in the Duchenne muscular dystrophy gene therapy race after this morning’s data from Pfizer (PFE) showed “serious safety signals” that led to hospitalization in two of six patients dosed, Piper Jaffray analyst Danielle Brill tells investors in a research note. And while Pfizer believes complement activation was driven by a high presence of neutralizing antibodies, the serious adverse event was also observed with Solid Biosciences’ (SLDB) gene therapy, which employs the same vector as Pfizer, adds the analyst. As a result, Brill thinks complement activation may be AAV9 related, especially since no such signal has been seen with Sarepta’s AAVrh74 vector. In addition, Pfizer has no edge over Sarepta on efficacy either, says the analyst. She thinks it will be “almost impossible” for Pfizer to compete moving forward and reiterates an Overweight rating on Sarepta with a $208 price target. The stock in afternoon trading is up 16%, or $20.61, to $150.37.