BioCryst shares tank after a PhII for hereditary angioedema flops

BioCryst CEO Jon Stonehouse

BioCryst got the biotech week started with a crash ($BCRX). The Research Triangle Park, NC-based company says its midstage study of their lead drug avoralstat for hereditary angioedema (HAE) flopped, with both doses failing to register a statistically significant improvement for patients compared to a placebo.

Investigators say they picked up enough encouraging signs of a dose response in the higher, 500-mg arm of the study to inspire another look at an even more potent attempt. But investors weren't in a forgiving mood Monday morning, driving down the biotech's shares almost 60% in premarket trading.

The data were bad. In the 500-mg/three times daily arm, 38 patients experienced a 0.63 mean rate of attacks, compared to 0.61 in the placebo arm. The 300-mg dose arm, with 36 patients, came up with a 0.71 rate. The investigators say that there was a statistically significant improvement in the duration of attacks in the 500-mg arm.

Avoralstat was an in-house discovery at BioCryst, and the company has been betting that the oral inhibitor of plasma kallikrein could tamp down on bradykinin production and moderate the acute swelling that afflicts patients who suffer from the rare genetic disease.

BioCryst turned to the drug after it scored a surprise approval for peramivir back in late 2014--after giving up on it following an unimpressive Phase III. Regulators were encouraging, but analysts were left with little to be enthused about in terms of market potential. So the biotech then turned back to the pipeline.

"OPuS-2 was a well-designed and executed trial that gave us a clear answer; this dosage form of avoralstat is not a viable formulation to move forward," said BioCryst CEO Jon Stonehouse. "While we are disappointed in the study results, we learned that meaningfully better exposure is needed for avoralstat to succeed. We expect results from a relative bioavailability study testing a novel solid dosage form of avoralstat by mid-year--the primary goals of this study are to achieve much higher exposures and twice daily dosing. Our other opportunity to achieve higher exposure of an oral kallikrein inhibitor is with BCX7353--we expect results from the BCX7353 APeX-1 dose ranging study in HAE patients by year end."

- here's the release

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