Abstract
Idelalisib is a first-in-class, oral, selective phosphatidylinositol 3-kinase δ inhibitor that offers a chemotherapy-free option for patients with relapsed or refractory (R/R) indolent non-Hodgkin lymphoma (iNHL). Clinical trials in iNHL have evaluated idelalisib as monotherapy and as combination therapy with rituximab, bendamustine, and rituximab + bendamustine. When administered to heavily pretreated patients with R/R iNHL, idelalisib monotherapy or combination therapy showed durable antitumor activity accompanied by sustained or improved quality-of-life outcomes. Idelalisib has an acceptable safety profile; however, serious or fatal diarrhea/colitis, hepatoxicity, pneumonitis, and intestinal perforation have occurred in treated patients. Selective inhibition of phosphatidylinositol 3-kinase δ with idelalisib is a valuable addition to available treatment options for patients with iNHL, many of whom do not respond to or cannot tolerate chemoimmunotherapy. Two Phase III, randomized, placebo-controlled trials of idelalisib as combination therapy with rituximab or bendamustine + rituximab and a Phase I trial of idelalisib in combination with the Bruton's tyrosine kinase inhibitor ONO/GS-4059 in R/R B-cell malignancies are currently ongoing. A Phase III monotherapy trial in previously treated follicular lymphoma or small lymphocytic lymphoma is planned. The development of other kinase inhibitors for the treatment of iNHL raises the potential for new treatment combinations. Additional research is needed to determine optimal therapy (monotherapy vs combination regimens), treatment sequencing, and long-term management.