Cellular pharmacokinetics and pharmacodynamics of the deoxycytidine analog2'-C-cyano-2'-deoxy-1-beta-D-arabino-pentofuranosylcytosine (CNDAC)

The pharmacokinetics and pharmacodynamics of the novel clinical candidate 2 '-C-cyano-2'-deoxy-1-beta -D-arabino-pentofuranosylcytosine (CNDAC) were in vestigated in human lymphoblastoid CCRF-CEM cells and human myeloblastic le ukemia ML-1 cells. Formation of CNDAC 5'-mono-, di-, and triphosphate (CNDA CTP) was concentration-dependent; nucleotide accumulation was greater in th e lymphoid cells than in the myeloid cells. The nucleotides were eliminated with linear kinetics from both lines, but were retained more effectively b y the ML-1 cells. DNA synthesis was selectively inhibited by a 4-hr treatme nt with CNDAC in CCRF-CEM and ML-1 cells; the Ic,, values were 1 and 0.8 mu M, respectively. Evaluation of the polymerization reaction of a primer on a n M13mp19(+) template by human DNA polymerase alpha indicated that CNDACTP was incorporated effectively (K-m = 0.22 muM) opposite a complementary dGMP in the template strand. CNDACTP competed with the normal substrate, dCTP, for incorporation, and the two nucleotides showed similar substrate efficie ncies (V-max/K-m: dCTP = 0.91; CNDACTP = 0.77). Primer extension was potent ly inhibited by CNDAC triphosphate (Ki = 23 nM); once the analog had been i ncorporated, further extension was not observed in vitro, suggesting that p rimers containing a 3'-terninal nucleotide analog were high K, substrates f or polymerase cu. Thus, the ability of human leukemia cells to effectively accumulate and retain CNDACTP, coupled with the favorable kinetics of compe tition for incorporation into DNA, and the relatively strong ability of the analog to terminate further extension, are likely to contribute to the cyt otoxic action of CNDAC. (C) 2001 Elsevier Science Inc. All rights reserved.