A phase II study of elacytarabine in combination with idarubicin and of human equilibrative nucleoside transporter 1 expression in patients with acute myeloid leukemia and persistent blasts after the first induction course.

Unlike cytarabine, cellular entry of Elacytarabine, the elaidic acid ester derivative of cytarabine, is independent of the human equilibrative nucleoside transporter 1 (hENT1). This phase II study tested whether the hENT1 blast expression level can be used as a predictive marker for cytarabine response and if the efficacy of elacytarabine is independent of hENT1 expression. A total of 51 patients with acute myeloid leukemia (AML) induction failure were given elacytarabine-idarubicin as a second induction course. The hENT1 expression level was analyzed prior to first induction and/or prior to treatment with elacytarabine. The overall response rate (ORR) was 41% and the safety profile was manageable. There is a trend suggesting that hENT1 expression influences response to cytarabine, but not sufficient to support it as a biomarker for guiding treatment. Further, we conclude that the activity of elacytarabine is not significantly predicted by the hENT1 expression level.