ZYDELIG, known generically as idelalisib, is a targeted therapy medication used in the treatment of certain blood cancers. Specifically, it is approved for use in patients with chronic lymphocytic leukemia (CLL), follicular lymphoma, and small lymphocytic lymphoma (SLL) who have received at least one prior therapy. As a phosphoinositide 3-kinase (PI3K) inhibitor, ZYDELIG works by blocking a specific protein that cancer cells need to grow and divide, thereby helping to slow the progression of the disease. It is administered orally in tablet form. Like all medications, ZYDELIG can cause side effects, and its use is generally recommended under the guidance of a healthcare professional experienced in treating blood cancers.