This study is being conducted to evaluate the efficacy and safety of deucrictibant (PHA-022121) in adults with Acquired Angioedema due to C1 Inhibitor Deficiency. This condition is a rare disease that causes episodes of swelling, known as angioedema, which often occur in the face, hands, feet, or digestive tract. The research focuses on two different ways to use the medication: to prevent these swelling attacks from happening and to treat them as they occur.

The study is divided into three different parts. In the first part, participants take an extended-release tablet, which is a type of medication designed to release the drug slowly into the body over time, to see if it can prevent attacks. This part compares the drug to a placebo. The second part looks at using a soft capsule, which is a small, gel-like pill, to provide relief during an active attack. This part also compares the medication to a placebo. In the final part, participants receive the medication during an attack to monitor its safety and how well it is tolerated by the body.