Pharmacodynamics of ara-C in combination with UCN-01. (A) Cellular accumulation of ara-CTP during therapy. (B) Inhibition of DNA synthesis during therapy. (C) Relationship between cellular concentrations of ara-CTP in circulating leukemic blasts 4 hours after ara-C infusion and extent of DNA synthesis inhibition relative to pretreatment values. ▴ indicates patient 1; ▪, patient 2; ▾, patient 3; ♦, patient 4; •, patient 5; □, patient 6; ⋄, patient 7; ○, patient 8;▵, patient 9; ^*, patient 10; ¦, patient 11; +, patient 12; and ×, patient 13.