The terms of Sarepta Therapeutics' (SRPT) licensing deal with Roche (RHHBY) suggest that Duchenne muscular dystrophy gene therapy is worth at least $6.5B to Sarepta stock, or at least $90 per share, Bernstein analyst Vincent Chen tells investors in a research note. The analyst's math indicates that the expected value of Roche's payments to Sarepta for its DMD gene therapy outside the U.S., after accounting for probability of success, is likely at least $3B, "most likely more," and the expected value of the U.S. DMD gene therapy is likely at least $3.6B, Chen says. Added together, this means the DMD gene therapy should be worth at least $6.5B to Sarepta's stock, "or at least $90 per share, likely well in excess of that," the analyst adds. Shares of Sarepta closed yesterday up $9.41 to $135.58.