* Drug, if approved, will be first oral preventive for hereditary angioedema
* Drug to compete with Shire's injectable Cinryze
* We'd like to make Cinryze obsolete - BioCryst's Chief Medical Officer
* U.S launch could be in 2017, peak U.S. sales of $1.2 bln by 2031-analyst
* Shares rise as much as 22 pct, among most heavily traded (Adds details, analyst and executive comment; updates shares)
By Natalie Grover
May 27 (Reuters) - BioCryst Pharmaceuticals Inc's oral drug to prevent a hereditary disorder characterized by abnormal swelling was effective in reducing attacks, sending the drugmaker's shares up as much as 22 percent.
The drug, if approved, will be the first oral preventive for hereditary angioedema (HAE) - a disease characterized by sudden attacks of swelling of the skin or mucous membranes, which can be disfiguring, painful and even fatal.
While Shire Plc's Firazyr, Dyax Corp's Kalbitor and CSL Behring's Berinert are injected to manage attacks after they occur, BioCryst's oral preventive would directly compete with Shire's injectable Cinryze.
"We don't intend to study the drug head to head against Cinryze. We'd like to make Cinryze obsolete because its an IV therapy," BioCryst's Chief Medical Officer William Sheridan told Reuters.
Patients given the drug, BCX4161, in a mid-stage trial had an average rate of 0.82 attacks per week, compared with 1.27 for those given a placebo, BioCryst said in a statement on Tuesday.
"Given the strong patient preference for an oral therapy, it would be hard to see how there wouldn't be significant competitive advantage for BioCryst's drug," H.C. Wainwright & Co analyst Andrew Fein said.
Fein said he expected the drug to be launched in the United States in 2017 and estimated peak U.S. sales of $1.2 billion by 2031.
BioCryst's study tested the safety and efficacy of a 400 mg dose of the drug administered three times a day for 28 days in patients with high frequency HAE.
Patients given the drug went 22 days on average without an attack, compared with 19 days for those given the placebo, the drugmaker said.
The treatment works by suppressing the production of a naturally-occurring peptide called bradykinin, which helps moderates blood pressure by dilating blood vessels. Patients with HAE have high levels of bradykinin.
BioCryst said it plans to conduct a 12-week trial for the drug in the second half of the year, testing its use in a broader patient population.
The company, which is also developing drugs for infectious diseases, currently sells its influenza treatment Peramivir in Japan and Korea.
The Research Triangle Park, North Carolina-based company's shares were up 9.6 percent at $9.87 and with more than 6 million shares changing hands by midday, the stock was one of the most actively traded on the Nasdaq. The stock touched a high of $10.98 earlier. (Additional reporting by Esha Dey in Bangalore; Editing by Savio D'Souza)