Positive Data from Phase III Study Shows Combination Therapy with Idelalisib Is More Effective Versus Standard of Care in Treatment-Resistant Chronic Lymphocytic Leukemia


Adding idelalisib (Zydelig®) to a standard chemotherapy regimen of bendamustine and rituximab (BR) significantly increases progression-free survival (PFS) and overall survival (OS) in patients with relapsed or treatment-resistant chronic lymphocytic leukemia (CLL) as compared with BR alone, according to new findings presented by a Memorial Sloan Kettering (MSK) investigator on behalf of his international co-investigators. Results from the phase III study were presented as part of the press program at this year’s American Society of Hematology annual meeting.

The study led by medical oncologist Andrew Zelenetz, MD, PhD, Vice Chair of Medical Informatics in the Department of Medicine and an Attending Physician on the Lymphoma Service at MSK, showed that the primary endpoint of PFS was increased by 12 months (23.1 v 11.1 months) when idelalisib was added to BR.

The phase III blinded, randomized controlled clinical trial compared BR plus a placebo with BR plus idelalisib in 416 patients. Trial participants had been treated for relapsed CLL less than 36 months following completion of prior therapy. Eligible patients were randomized to receive six cycles of BR over 24 weeks with either idelalisib or placebo taken orally twice daily until disease progression or unacceptable toxicity. 

Of the 207 patients receiving the combination of idelalisib, there was a 67 percent reduction in the risk of disease progression or death compared with 209 trial participants who received BR alone. Trial results were so impressive that the Independent Data Monitoring Committee recommended immediate discontinuation of the study and release of the information because of overwhelming benefit.

“We believe that based on the improved outcomes in both progression-free and overall survival that we saw in this study, addition of idelalisib to a current standard of care option bendamustine and rituximab represents an important new option for our patients,” said Dr. Zelenetz.  

Idelalisib is a highly selective drug that affects certain blood cells. Specifically, it inhibits one form of a protein called PI3kinase, which is present only in white blood cells and is critical for their survival. Idelalisib received FDA approval last year for the treatment of CLL patients whose disease has relapsed but who cannot tolerate chemotherapy due to other medical conditions. It is also approved to treat certain types of lymphoma.

Abstract #LBA-5:  Idelalisib Plus Bendamustine and Rituximab (BR) Is Superior to BR Alone in Patients with Relapsed/Refractory Chronic Lymphocytic Leukemia: Results of a Phase 3 Randomized Double-Blind Placebo-Controlled Study