(HealthDay News) — The phosphatidylinositol-3-kinase delta (PI3Kδ) inhibitor idelalisib shows antitumor activity in patients with indolent non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL), according to two studies published in the March 13 issue of the New England Journal of Medicine.

Ajay K. Gopal, MD, from the University of Washington School of Medicine in Seattle, and colleagues conducted a phase 2 study of idelalisib involving 125 patients with previously treated indolent non-Hodgkin lymphomas.

The researchers found that the response rate was 57% overall, and 6% of patients met complete response criteria. The median time to response, duration of response, and progression-free survival were 1.9, 12.5, and 11 months, respectively.

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Response rates were similar across all subtypes of indolent non-Hodgkin’s lymphoma.

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In a second study, Richard R. Furman, MD, from Weill Cornell Medical College in New York City, and colleagues examined the efficacy and safety of idelalisib in combination with rituximab versus rituximab plus placebo for 220 patients with relapsed CLL with clinically significant coexisting medical conditions.

The researchers found that the median progression-free survival was not reached in the idelalisib group and was 5.5 months in the placebo group (hazard ratio for progression or death, 0.15; P < 0.001).

In the idelalisib group, the rates of overall response (81% vs 13%; odds ratio, 29.92) and overall survival at 12 months (92% vs 80%; hazard ratio, 0.28) were significantly increased.

“The emerging success of idelalisib illustrates the clinical translation of basic research studies of PI3K signaling in B cells,” wrote the authors of an accompanying editorial.

Both studies were funded by Gilead Sciences, the manufacturer of idelalisib.


  1. Gopal AK, Kahl BS, de Vos S, et al. PI3Kδ Inhibition by Idelalisib in Patients with Relapsed Indolent Lymphoma. N Engl J Med. 2014; 370:1008-1018.
  2. Furman RR, Sharman JP, Coutre SE, et al. Idelalisib and Rituximab in Relapsed Chronic Lymphocytic Leukemia. N Engl J Med. 2014; 370:997-1007.
  3. Fruman DA, Cantley LC. Idelalisib — A PI3Kδ Inhibitor for B-Cell Cancers. N Engl J Med. 2014; 370:1061-1062.