RT Journal Article
SR Electronic
T1 In Vitro Evaluation of the Disposition of A Novel Cysteine Protease Inhibitor
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 1343
OP 1351
VO 28
IS 11
A1 Wolfgang Jacobsen
A1 Uwe Christians
A1 Leslie Z. Benet
YR 2000
UL http://dmd.aspetjournals.org/content/28/11/1343.abstract
AB K11777 (N-methyl-piperazine-Phe-homoPhe-vinylsulfone-phenyl) is a potent, irreversible cysteine protease inhibitor. Its therapeutic targets are cruzain, a cysteine protease of the protozoan parasiteTrypanosoma cruzi, and cathepsins B and L, which are associated with cancer progression. We evaluated the metabolism of K11777 by human liver microsomes, isolated cytochrome P450 (CYP) enzymes, and flavin-containing monooxygenase 3 (FMO3) in vitro. K11777 was metabolized by human liver microsomes to three major metabolites:N-oxide K11777 (apparentKm = 14.0 ± 4.5 μM and apparentVmax = 3460 ± 3190 pmol · mg−1 · min−1, n = 4), β-hydroxy-homoPhe K11777 (Km = 16.8 ± 3.5 μM and Vmax = 1260 ± 1090 pmol · mg−1 · min−1, n = 4), andN-desmethyl K11777 (Km = 18.3 ± 7.0 μM and Vmax = 2070 ± 1830 pmol · mg−1 · min−1, n = 4). All three K11777 metabolites were formed by isolated CYP3A and their formation by human liver microsomes was inhibited by the CYP3A inhibitor cyclosporine (50 μM, 54–62% inhibition) and antibodies against human CYP3A4/5 (100 μg of antibodies/100 μg microsomal protein, 55–68% inhibition). CYP2D6 metabolized K11777 to its N-desmethyl metabolite with an apparent Km (9.2 ± 1.4 μM) lower than for CYP3A4 (25.0 ± 4.0 μM) and human liver microsomes. The apparent Km forN-oxide K11777 formation by cDNA-expressed FMO3 was 109 ± 11 μM. Based on the intrinsic formation clearances and the results of inhibition experiments (CYP2D6, 50 μM bufuralol; FMO3 mediated, 100 mM methionine) using human liver microsomes, it was estimated that CYP3A contributes to >80% of K11777 metabolite formation. K11777 was a potent (IC50 = 0.06 μM) and efficacious (maximum inhibition 85%) NADPH-dependent inhibitor of human CYP3A4 mediated 6′β-hydroxy lovastatin formation, suggesting that K11777 is not only a substrate but also a mechanism-based inhibitor of CYP3A4. The American Society for Pharmacology and Experimental Therapeutics