A low level of the C1-inhibitor in the blood causes an increased amount of the protein bradykinin, which causes the painful symptoms of HAE swellings. PHVS416 is designed to attempt to prevent some of the effects of bradykinin, which may prevent HAE swellings (acute attacks).
In Part 1 of this clinical research study, PHVS416 is a softgel capsule taken orally that is being compared to a placebo. A placebo is an inactive drug that looks just like the investigational medication being studied but contains no active ingredients. The placebo allows researchers to fully understand the effects of the investigational medication.
Two capsules of PHVS416 or the placebo are taken by mouth twice daily after breakfast and dinner for 12 weeks. Participants will be chosen at random to receive the low dose of PHVS416 (one capsule of PHVS416 and one capsule of the placebo), the high dose of PHVS416 (two capsules of PHVS416), or the placebo (two capsules of the placebo). Neither participants nor the study doctor will know which study treatment has been assigned, but in case of an emergency, the study doctor can find out.
In Part 2 of this clinical research study, the placebo will not be used, and all participants will receive PHVS416. Two capsules of PHVS416 are taken by mouth twice daily after breakfast and dinner for a duration of 50 weeks.