Metabolism of 3-cyanomethyl-4-methyl-DCK, a new anti-HIV candidate, in human intestinal microsomes

The biotransformation, CYP reaction phenotyping, the impact of CYP inhibitors and enzyme   kinetics of 3-cyanomethyl-4-methyl-DCK (CMDCK), a new anti-HIV preclinical candidate belonging to DCK analogs, were investigated in human intestinal microsomes and recombinant cytochrome P450 (CYP) enzymes.  CMDCK (4 μmol·L⁻¹) was incubated with a panel of rCYP enzymes (CYP1A2, 2C9, 2C19, 2D6 and 3A4) in  vitro.  The remaining parent drug in incubates was quantitatively analyzed by a LC-MS method.  CYP3A4 was identified as the principal CYP isoenzyme responsible for its metabolism in intestinal microsomes.  The major metabolic pathway of CMDCK was oxidation and a number of oxidative metabolites were screened with LC-MS.  The K_m, V_max, CL_int and T_1/2 of CMDCK obtained from human intestinal microsome were 45.6 μmol·L⁻¹, 0.33 μmol·L⁻¹·min⁻¹, 12.1 mL·min⁻¹·kg⁻¹ and 25.7 min, respectively.  Intestinal clearance of CMDCK was estimated from in vitro data to be 3.3 mL·min⁻¹·kg⁻¹, and was almost equal to the intestinal blood flow rate (4.6 mL·min⁻¹·kg⁻¹).  The selective CYP3A4 inhibitors, ketoconazole, troleandomycin and ritonavir demonstrated significant inhibitory effects on CMDCK intestinal metabolism, which suggested that co-administration of CMDCK with potent CYP3A inhibitors, such as ritonavir, might decrease its intestinal metabolic clearance and subsequently improve its bioavailability in body.