In biotech, what goes around comes around.Yesterday, PTC Therapeutics (NASDAQ: PTCT) jumped 27.5% following positive data for its spinal muscular atrophy drug, risdiplam, which sent shares of competitors Biogen and Ionis Pharmaceuticals down on the news.Today, it was PTC Therapeutics' turn to take a hit, falling 30.6% today, after competitor Sarepta Therapeutics (NASDAQ: SRPT) presented data for its gene therapy to treat Duchenne muscular dystrophy (DMD).Continue reading