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US-based biotechnology company Gilead Sciences plans to stop its Phase III study (Study 116) of idelalisib for the treatment of chronic lymphocytic leukemia (CLL), following the recommendation by an independent data monitoring committee (DMC).

The Phase III study is evaluating the efficacy and safety of idelalisib, an inhibitor of phosphoinositide 3-kinase (PI3K) delta, in combination with rituximab in previously-treated CLL patients who are not fit for chemotherapy.

The DMC recommended the company to stop its Phase III study based on positive interim results, demonstrating highly statistically significant efficacy for the primary endpoint of progression-free survival in patients receiving idelalisib plus rituximab, when compared with those receiving rituximab alone.

Gilead Sciences’ research and development executive vice-president Dr Norbert W Bischofberger said: "This is the first Phase 3 study to report positive results for a new class of targeted therapies that inhibit B-cell receptor signalling as a major component of their mechanism of action, an important area of focus in the development of chemotherapy-free regimens in CLL and other B-cell malignancies.

"We extend thanks to the investigative sites and to the other research collaborators participating in this study, as well as to the patients who volunteered, and we look forward to sharing these data with the hematology community."

Patients who are randomised to idelalisib in the Phase III study will continue receiving idelalisib and patients in the control arm (placebo plus rituximab) will be eligible to receive open-label idelalisib therapy in an extension study.

"We extend thanks to the investigative sites and to the other research collaborators participating in this study, as well as to the patients who volunteered, and we look forward to sharing these data with the hematology community."

Participants who progressed on Phase III study will be eligible to receive active idelalisib therapy in a double-blind extension study (Study 117).

The company is planning an expanded access programme for recurrent CLL patients who are not fit for chemotherapy and require treatment.

Following the DMC’s recommendation, Gilead Sciences notified the US Food and Drug Administration of its plan to end the study early.

Gilead Sciences is developing idelalisib as a single agent and in combination with approved and investigational therapies.

In September 2013, Gilead Sciences submitted a new drug application (NDA) for idelalisib for refractory indolent non-Hodgkin’s lymphoma.

The company also plans to seek EU regulatory approval for idelalisib later 2013.


Image: Wright’s stained peripheral blood smear showing chronic lymphocytic leukemia (CLL). Photo: courtesy of Bibi Saint-Pol.