Apellis Pharmaceuticals (NASDAQ:APLS) announced results on Tuesday from its Pegasus late-stage clinical study evaluating experimental drug pegcetacoplan (APL-2) in treating adults with paroxysmal nocturnal hemoglobinuria (PNH), a rare blood disorder. The biotech company stated that pegcetacoplan achieved the primary efficacy endpoint of the study by producing greater improvement in patients' hemoglobin levels than Alexion Pharmaceuticals (NASDAQ:ALXN) Soliris.

This news caused Apellis stock to soar more than 20% Tuesday morning. Alexion's share price opened down more than 3% but later rebounded.

Gloved hands holding two test tubes

Image source: Getty Images.

Digging into the results

The Pegasus study included 41 patients receiving pegcetacoplan and 39 patients receiving Soliris. Apellis reported that pegcetacoplan achieved an improvement in the adjusted means of 3.8 grams per deciliter of hemoglobin at week 16 of the study compared to Soliris with a high level of statistical significance. The company also said that its drug "showed promising results" on key secondary endpoints including avoiding transfusions and reducing fatigue. Pegcetacoplan's safety profile was similar to that of Soliris. 

Those results were better than Apellis anticipated. CEO Cedric Francois stated, "Going into the study, our most optimistic expectation was to see a 2 g/dL or more change in hemoglobin and a trend on the key secondary endpoints. Needless to say, we are thrilled with these results."

Pegcetacoplan is the first drug to beat Soliris in improving hemoglobin levels in patients with PNH. The Pegasus results point to the possibility that Apellis' drug could become the new standard of care in treating the rare blood disorder.

Next steps for Apellis

Apellis plans to present detailed results from the Pegasus study at a future scientific meeting. The company also hopes to meet with regulators in the first half of 2020 to discuss the pathway to approval for pegcetacoplan.