This clinical trial is focused on studying a condition known as Hereditary Angioedema, which is a rare genetic disorder that causes sudden swelling attacks in various parts of the body, including the face, hands, and throat. The study is specifically looking at patients with Hereditary Angioedema due to a deficiency in a protein called C1-Inhibitor, which can be of Type I or Type II. The treatment being tested is an oral medication called Deucrictibant (PHA-022121), which is designed to be taken during an acute attack to help manage the symptoms.

The purpose of this study is to evaluate the safety of long-term use of Deucrictibant for treating these acute attacks, including those affecting the throat, but without causing breathing difficulties. Participants in the study will take the medication as needed during an attack, and their health will be monitored over time to ensure the treatment is safe. The study will also involve a comparison with a placebo, which is a substance with no active medication, to better understand the effects of Deucrictibant.

Throughout the study, participants will be asked to report any side effects they experience, and regular health checks will be conducted, including monitoring vital signs and performing laboratory tests. The study aims to provide valuable information on how well Deucrictibant works in relieving symptoms and improving the quality of life for those with Hereditary Angioedema. This research is important for developing effective treatments for managing this challenging condition.