Idelalisib for the treatment of chronic lymphocytic leukemia

Idelalisib: A Novel PI3Kδ Inhibitor for Chronic Lymphocytic Leukemia

OBJECTIVE

To review and summarize data on idelalisib, which was approved by the Food and Drug Administration (FDA) in July 2014 for use in combination with rituximab for relapsed chronic lymphocytic leukemia (CLL).

DATA SOURCES

A literature search using PubMed was conducted from January 2011 through May 2015 using the terms idelalisib, GS-101, CAL-101, PI3Kδ, and CLL. Data were also obtained through the FDA briefing documents, American Society of Clinical Oncology, and American Society of Hematology abstracts.

STUDY SELECTION AND DATA EXTRACTION

The literature search was limited to human studies published in English. Priority was placed on trials of idelalisib in CLL.

DATA SYNTHESIS

Idelalisib is a potent, first-in-class selective inhibitor of phosphatidylinositol-3-kinaseδ (PI3Kδ) approved by the FDA in July 2014 for the treatment of relapsed CLL, in combination with rituximab, in patients for whom rituximab monotherapy would be considered appropriate due to other comorbidities. PI3Kδ is hyperactivated in B-cell malignancies and plays a vital role in the B-cell receptor pathway, a key oncogenic driver in various B-cell malignancies, including CLL. Several phase I/II studies have demonstrated clinical activity of idelalisib in CLL, particularly in the setting of relapsed/refractory disease, with overall response rate ranging from 70% to 82%. The FDA approval was based on a phase III, randomized trial of rituximab monotherapy (n = 110) or idelalisib in combination with rituximab (n = 110) in heavily, pre-treated patients (median of 3 prior therapies) with relapsed CLL. Idelalisib was administered as 150 mg orally twice daily. Idelalisib plus rituximab was associated with an overall response rate of 81% and overall survival of 91% at 12 months. The median progression-free survival was not reached in the idelalisib arm at the time of the first interim analysis. The incidence of grade 3 or higher adverse events in the idelalisib plus rituximab arm was as follows: neutropenia (34%), thrombocytopenia (10%), anemia (5%), elevation in transaminases (5%), and diarrhea (4%).

CONCLUSION

Idelalisib in combination with rituximab is a safe and effective new treatment option for patients with relapsed CLL, including those with poor prognostic factors. As the results from various ongoing studies become available, the role of idelalisib will likely continue to expand.

DNA damage response and evasion from immunosurveillance in CLL: new options for NK cell-based immunotherapies

Chronic lymphocytic leukemia (CLL) is the most prominent B cell malignancy among adults in the Western world and characterized by a clonal expansion of B cells. The patients suffer from severe immune defects resulting in increased susceptibility to infections and failure to generate an antitumor immune response. Defects in both, DNA damage response (DDR) pathway and crosstalk with the tissue microenvironment have been reported to play a crucial role for the survival of CLL cells, therapy resistance and impaired immune response. To this end, major advances over the past years have highlighted several T cell immune evasion mechanisms in CLL. Here, we discuss the consequences of an impaired DDR pathway for detection and elimination of CLL cells by natural killer (NK) cells. NK cells are considered to be a major component of the immunosurveillance in leukemia but NK cell activity is impaired in CLL. Restoration of NK cell activity using immunoligands and immunoconstructs in combination with the conventional chemotherapy may provide a future perspective for CLL treatment.