This study looks at KPL-387 as a treatment for recurrent pericarditis, a condition where the sac around the heart, called the pericardium, becomes inflamed again after a previous episode. It's divided into three parts: Phase 2, Phase 3, and Long-Term Extension. Phase 2 tests different doses of KPL-387 to see how well it reduces pain and swelling. Phase 3 checks if it really works and if it can prevent pericarditis from coming back. If you finish either phase, you might join the Long-Term Extension to see how well the treatment works over a long time. Throughout the study, researchers also study the safety and side effects of KPL-387.

• The study involves multiple phases, each with different goals and durations.
• Eligibility requires having recurrent pericarditis and not having certain other medical conditions.
• Participants might need to stop taking other investigational drugs before joining.