Sarepta Pharmaceuticals Inc (NASDAQ: SRPT) stock is plummeting down, down 31.4% at $16.77 at last glance. Though the biotech company reported an impressive revenue beat, a wider-than-expected loss per share and disappointing trial data for two gene-therapy treatments for Duchenne muscular dystrophy weighed.SRPT is no stranger to outsized moves, having experienced several bear gaps this year. The shares had been creeping higher since their July 24, nine-year low of$10.41 -- with help from the company's rest ...