Used to treat activated phosphoinositide 3-kinase delta syndrome (APDS), a rare primary immunodeficiency disorder. It works by selectively inhibiting the PI3K delta enzyme, which plays a key role in the overactivation of immune cells seen in APDS. By modulating this pathway, it helps reduce lymphoproliferation, improves immune function, and decreases the frequency of infections in affected patients. It is taken orally and is designed for long-term management of the condition, particularly in adults and children over 12 years old.