Idelalisib Products | Cleanchem - Idelalisib is a phosphoinositide 3-kinase (PI3K) inhibitor used to treat certain types of blood cancers, such as chronic lymphocytic leukemia (CLL) and follicular lymphoma. By blocking PI3K, it inhibits the signaling pathways that promote cancer cell survival and proliferation, leading to cancer cell death. It is usually administered orally.