Shares of Zogenix Inc. (ZGNX) jumped 143.9% to $31.40 in morning trading on Friday, Sept. 29, after the Emeryville, Calif.-based firm said its first Phase 3 study of  ZX008 in Dravet syndrome achieved its primary endpoint. Dravet syndrome is a form of epilepsy.

 ZX008 also showed statistically significant improvements versus placebo in all key secondary measures, the company said.

"These results are truly exciting and demonstrate, in a large multicenter controlled trial, the impressive efficacy of low-dose fenfluramine for patients with Dravet syndrome," said Joseph Sullivan M.D., director of the Pediatric Epilepsy Center in UCSF Benioff Children's Hospital San Francisco and principal investigator of Study 1 in the U.S., in a statement.

GW Pharmaceuticals plc's (GWPH) American depository receipts were down 12.6% to $98.15 on the heels of the Zogenix announcement. London-based GW in March of last year announced positive results from a Phase 3 study of Epidiolex for the treatment of Dravet syndrome.

Among the other biotech stock movers was Prothena Corporation plc (PRTA - Get Report) . Shares were down 2.6% to $66 in the wake of word that the Dublin firm was not advancing PRX003 into mid-stage clinical development.

Prothena on Thursday unveiled the results of a Phase 1b multiple ascending dose study of PRX003 in patients with psoriasis. "While the primary objectives of the study were achieved, advancing PRX003 into mid-stage clinical development required a well-defined relationship between biological activity and meaningful clinical effects, and these prerequisites were not met," the company said.

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