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Next generation kallikrein inhibitors for HAE

BCX7353 and other 2nd Gen kallikrein inhibitors

BioCryst’s goals for its second-generation kallikrein inhibitor program are to develop and launch a revolutionary treatment for hereditary angioedema patients, consisting of an oral, once-a-day drug that could restore the normal phenotype of kallikrein inhibition – resulting in elimination of angioedema attacks in patients with confirmed Hereditary Angioedema.

In October 2015, BioCryst announced that it’s randomized, placebo-controlled, Phase 1 clinical trial of orally-administered BCX7353 in healthy volunteers successfully met all of its objectives. BCX7353 was generally safe and well tolerated at all doses up to 500 mg once-daily for 7 days and 350 mg once-daily for 14 days in healthy volunteers, with dose-related drug exposure and a half-life supporting a once-daily dosing regimen.

There were no serious adverse events (AEs) and most AEs were mild. No dose-limiting toxicity was identified. The safety, tolerability, drug exposure and on-target plasma kallikrein inhibition results strongly support advancing the development program into a Phase 2 study in hereditary angioedema (HAE) patients.

On August 11th, 2016, BioCryst announced that it dosed the first subject in the APeX-1 clinical trial of BCX7353 for the oral treatment of hereditary angioedema (HAE).  APeX-1 is a two part, Phase 2, randomized, double-blind, placebo-controlled dose ranging trial to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics and efficacy of BCX7353 as a preventative treatment to eliminate or reduce the frequency of angioedema attacks in HAE patients.  Up to approximately 50 eligible subjects with HAE will be enrolled in the study.

In part 1 of APeX-1, subjects with HAE will be randomized in a 1:1 ratio to receive an oral dose of either 350 mg of BCX7353 once daily or placebo once daily for four weeks. An interim analysis will be conducted after the first 24 subjects have completed treatment through study day 28.  If a robust treatment effect is observed at the interim analysis, Part 2 of the study will be initiated. In the event the treatment effect is not well characterized with 24 subjects, a total of up to approximately 36 subjects will be enrolled in part 1. The sample size in Part 1 is being kept flexible to cover a range of response options that would achieve 90% power with an alpha of 0.05, based on reduction of attack rate of at least 70% on BCX7353, placebo response rate of approximately 30%, and standard deviation of approximately 0.45 attacks per week.

To characterize dose-response in part 2 of APeX-1, 14 additional subjects with HAE will be randomized to 250mg of BCX7353 once daily (n=6), 125mg of BCX7353 once daily (n=6) or placebo (n=2).

The primary efficacy endpoint of APeX-1 is the number of angioedema attacks; attack rate per week, counts of attacks, proportion of subjects with no attacks, and number of attack-free days will be analyzed. Efficacy analyses will be conducted for HAE attacks reported over the entire dosing interval (Days 1 through 28) and during the dosing period in which plasma concentrations of BCX7353 should be at steady-state conditions (Days 8 through 28). Secondary efficacy endpoints include severity and duration of angioedema attacks, and measures of health-related quality of life. Safety will be characterized through evaluation of adverse events and laboratory testing. Pharmacokinetics and pharmacodynamic effects will be assessed through measurement of plasma drug levels and kallikrein inhibition.

Additional details regarding the APeX-1 trial design are available at www.clinicaltrials.gov