BioCryst Reports Additional Positive Results From the Second Interim Analysis of Its APeX-1 Trial

BioCryst Pharmaceuticals announced results from a second interim analysis of its Phase 2 APeX-1 clinical trial in hereditary angioedema (HAE). APeX-1 is a 3-part dose ranging trial designed to evaluate the efficacy, safety, tolerability, pharmacokinetics and pharmacodynamics of orally administered once-daily (QD) BCX7353 for 28 days, as a preventative treatment to reduce the frequency of attacks in HAE patients. This second interim analysis evaluated data from all patients in Parts 1 and 2 of the trial. The first interim analysis evaluated data from 28 of 36 patients in Part 1.

“These data support our hypothesis regarding the initial findings seen from the first interim analysis,” said Jon Stonehouse, Chief Executive Officer & President of BioCryst. “We are delighted to see that a daily dose of 125 mg of BCX7353 results in a high level of efficacy with an improved tolerability profile compared to the 350 mg dose observed in the first interim analysis. We look forward to completing Part 3 of the trial to select appropriate doses for our pivotal program.”

This second interim analysis of pooled data from Parts 1 and 2 evaluated doses of BCX7353 125 mg (n=7), 250 mg (n=6) and 350 mg (n=18) QD versus placebo (n=20) for 28 days. The baseline attack rate was approximately 1/week. Baseline characteristics were generally well balanced between the treatment groups. Compliance with study drug dosing was excellent (≥ 98%).

The pre-specified per-protocol (PP) interim analysis included data on a total of 44 subjects with confirmed Type 1 or Type 2 HAE completing 28 days of treatment. The percentage reductions by treatment group in the mean rate of independently-adjudicated angioedema attacks for the pre-defined effective dosing period (weeks 2 through 4) in BCX7353 treated subjects were: 125 mg QD, 73% (p=0.002); 250 mg QD, 37% (p=0.128) and 350 mg QD, 58% (p=0.001) compared to placebo. In the intent-to-treat (ITT) population, corresponding reductions by treatment group were: 125 mg QD, 73% (p=0.004); 250 mg QD, 44% (p=0.090) and 350 mg QD, 45% (p=0.014) compared to placebo.

A pre-planned analysis of peripheral and abdominal attacks showed reductions in peripheral attacks of 74% (125 mg QD), 54% (250 mg QD) and 90% (350 mg QD) compared with placebo (PP analysis, weeks 2 through 4) and reductions in abdominal attacks of 72% (125 mg QD), 10% (250 mg QD) and 8% (350 mg QD) compared with placebo (PP analysis, weeks 2 through 4). Based on this distribution, it is likely that subjects in the 250 mg and 350 mg arms recorded transient abdominal adverse events (AEs) as HAE attack symptoms in their diary. In contrast, a consistent reduction in attacks regardless of anatomical location was observed in the 125 mg arm.

Oral BCX7353 once-daily for 28 days was generally safe and well tolerated in subjects with HAE. There were no serious AEs and no severe AEs. Three subjects in the BCX7353 350 mg treatment arm, two of which were previously reported, discontinued study drug before day 28. A third subject in this arm discontinued study drug due to vomiting and abdominal cramps concurrent with menses. The most common treatment-emergent adverse events were the common cold and diarrhea. The gastrointestinal AEs previously observed in the 350 mg arm were not seen at the 125 mg dose. Additionally, no significant laboratory abnormalities were observed in the two lower dose groups.

Steady state BCX7353 plasma levels and kallikrein inhibition levels in HAE subjects were similar to those seen in healthy subjects administered the same doses in a previously completed Phase 1 trial. Steady state trough drug levels (24 hours after dosing) greatly exceeded the target therapeutic range at the 250 mg and 350 mg dose levels. Trough levels for the 125 mg dose were generally within the target range.

The efficacy, safety and tolerability profile of BCX7353 observed in this interim analysis strongly supports its continued investigation as a prophylactic treatment for HAE. Enrollment into Part 3 of the trial is progressing well. Completion of Part 3 will enable a full evaluation of the dose response necessary to select doses for a pivotal program.