Shares of BioCryst Pharmaceuticals (BCRX) are plunging in morning trading after the biotechnology company reported disappointing clinical trial results for its potential hereditary angioedema treatment.

What's new: BioCryst this morning announced results from its OPuS-2 trial evaluating avoralstat in treatment of patients with hereditary angioedema, or HAE. BioCryst said either a 500 mg or 300 mg dose of the drug was administered three times daily to patients suffering HAE attacks, but said those patients did not have a lower rate of edema, or swelling, than patients given a placebo. The primary goals of the study were to characterize the efficacy of avoralstat in reducing the frequency of angioedema attacks and to evaluate the safety and tolerability of 12 weeks of avoralstat treatment. The primary efficacy endpoint of the study was angioedema attack frequency, with secondary endpoints including quality of life, attack duration and attack severity.

Executive commentary: President and Chief Executive Officer Jon Stonehouse said that the OPuS-2 trial 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.” Stonehouse also commented that “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.” He said that the company's other opportunity to achieve higher exposure of an oral kallikrein inhibitor is with BCX7353 and the company expects results from the BCX7353 APeX-1 dose ranging study in HAE patients by year end.

Price in action: In morning trading, BioCryst dove 66% to $2.10.