Plasma FL levels from clinical trial patients. (A) Plasma samples obtained on day 15 of induction therapy for newly diagnosed (left) versus relapsed (right) FLT3 mutant AML patients were assayed for FL by enzyme-linked immunosorbent assay. (B) FL levels from plasma samples obtained from newly diagnosed FLT3 mutant AML patients. Course 1 was induction; and courses 2-4 were consolidation. The course 1 samples correspond to the samples on the left in panel A. For course 1, the mean FL concentration was 488 pg/mL (range, 3-4099 pg/mL); for course 2, the mean was 1196 pg/mL (range, 34-8889 pg/mL); for course 3, the mean was 2298 pg/mL (range, 30-5451 pg/mL); for course 4, the mean was 2145 pg/mL (range, 76-7108 pg/mL). (C) FL plasma levels from individual patients on the Cephalon 204 trial at 3 different time points during therapy. For the baseline samples, there was a single sample measuring 2953 pg/mL. Twenty-two baseline samples had FL levels below the limit of detection for the assay (eg, < 2 pg/mL). These samples were listed as having 2 pg/mL. For the baseline samples, the median was 5 pg/mL, the mean was 57 pg/mL, and the range was from undetectable to 2298 pg/mL. For the day 15 samples, the mean was 1173 pg/mL, the median was 721 pg/mL, and the range was 19 to 3818 pg/mL. For the day 42 samples, the median was 187 pg/mL, the mean was 642 pg/mL, and the range was 4 to 5767 pg/mL.