BioCryst's shares halve despite late-stage study success for BCX7353 in hereditary angioedema

Shares in BioCryst Pharmaceuticals fell more than 50 percent Tuesday despite the company reporting that a Phase III study of BCX7353 for the prevention of hereditary angioedema (HAE) attacks achieved its primary endpoint. In the APeX-2 trial, the highest dose of the oral, once-daily kallikrein inhibitor reduced the attack rate in HAE patients by 44 percent compared to placebo. 

Further results showed that 50 percent of patients receiving the highest dose of BCX7353 had at least a 70-percent reduction in their HAE attack rate compared to baseline, versus 15 percent of placebo patients. Meanwhile, in patients with a baseline attack rate of less than two attacks per month, the higher dose of BCX7353 reduced the HAE attack rate by 66 percent compared to placebo. In addition, in those with a baseline attack rate of at least two attacks per month, the attack rate was reduced by 40 percent.

While current treatments for HAE, such as Takeda's Takhzyro (lanadelumab), are either delivered intravenously or subcutaneously, they have demonstrated high reductions in attack rate. Results from the HELP study showed that Takhzyro reduced the number of monthly HAE attacks by an average of 87 percent versus placebo when administered every two weeks and 73 percent compared to placebo when administered every four weeks.

However, BioCryst CEO Jon Stonehouse suggested that "HAE patients around the world desperately want access to a cost-effective, convenient, oral therapy to manage their disease." The executive said "given the profile of the 150 mg dose of BCX7353 in APeX-2…we have a new oral therapy that patients will want to try," adding "we believe BCX7353 is positioned to become a front-line therapy option." The company indicated that it plans to submit a marketing application for BCX7353 to the FDA in the fourth quarter and a submission to the European Medicines Agency in the first quarter of 2020. 

In the study, 121 patients with Type I and II HAE were randomised to receive placebo or one of two doses of BCX7353. The trial's primary efficacy endpoint is the rate of investigator confirmed angioedema attacks over 24 weeks of study drug administration, which BioCryst noted was reduced by 30 percent versus placebo in patients given the lower dose of BCX7353. The company said it plans to submit detailed results from the trial for peer‑reviewed publication and presentation. 

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