Sarepta Therapeutics Inc. (SRPT - Get Report) soared nearly 40% in Tuesday trading after publishing impressive results for a new gene therapy designed to treat a rare form of muscular dystrophy. However, the news pushed shares of rival drugmaker PTC Therapeutics Inc. (PTCT - Get Report)  down by almost the same percentage,

Sarepta rose $38.69 -- or 36.8% -- to $143.93 after results for its drug to treat Duchenne muscular dystrophy outperformed Wall Street's expectations. But PTC Therapeutics Inc. (PTCT - Get Report)  , which makes a drug designed to treat the same disease, tumbled $14.64 -- 30.6% -- to $33.24 on the news.

PTC Therapeutics' fall came just one day after its stock rose 28% after it published positive results for a new spinal muscular atrophy treatment.