RT Journal Article
SR Electronic
T1 CYP1A-Mediated Metabolism of the Janus Kinase-3 Inhibitor 4-(4′-Hydroxyphenyl)-amino-6,7-<br clear="none"/>dimethoxyquinazoline: Structural Basis for Inactivation by Regioselective <em>O</em>-Demethylation
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 74
OP 85
DO 10.1124/dmd.30.1.74
VO 30
IS 1
A1 Fatih M. Uckun
A1 Jason Thoen
A1 Hao Chen
A1 Elise Sudbeck
A1 Chen Mao
A1 Ravi Malaviya
A1 Xing-Ping Liu
A1 Chun-Lin Chen
YR 2002
UL http://dmd.aspetjournals.org/content/30/1/74.abstract
AB Here we report the phase I metabolism of the rationally designed Janus kinase-3 (JAK) inhibitor 4-(4′-hydroxyphenyl)-amino-6,7-dimethoxyquinazoline (WHI-P131; JANEX-1). JANEX-1 was metabolized by the cytochrome P450 enzymes CYP1A1 and CYP1A2 in a regioselective fashion to form the biologically inactive 7-O-demethylation product 4-(4′-hydroxyphenyl)-amino-6-methoxy-7-hydroxyquinazoline (JANEX-1-M). Our molecular modeling studies indicated that the CYP1A family enzymes bind and demethylate JANEX-1 at the C-7 position of the quinazoline ring since the alternative binding conformation with demethylation at the C-6 position would result in a severe steric clash with the binding site residues. The metabolism of JANEX-1 to JANEX-1-M in pooled human liver microsomes followed Michaelis-Menten kinetics withVmax and Kmvalues (mean ± S.D.) of 34.6 ± 9.8 pmol/min/mg and 107.3 ± 66.3 μM, respectively. α-Naphthoflavone and furafylline, which both inhibit CYP1A2, significantly inhibited the formation of JANEX-1-M in human liver microsomes. There was a direct correlation between CYP1A activities and the magnitude of JANEX-1-M formation in the liver microsomes from different animal species. A significantly increased metabolic rate for JANEX-1 was observed in Aroclor 1254-, β-naphthoflavone-, and 3-methylcholanthrene-induced microsomes but not in clofibrate-, dexamethasone-, isoniazid-, and phenobarbital-induced microsomes. The formation of JANEX-1-M in the presence of baculovirus-expressed CYP1A1 and 1A2 was consistent with Michaelis-Menten kinetics. The systemic clearance of JANEX-1-M was much faster than that of JANEX-1 (5525.1 ± 1926.2 ml/h/kg versus 1458.0 ± 258.6 ml/h/kg). Consequently, the area under the curve value for JANEX-1-M was much smaller than that for JANEX-1 (27.5 ± 8.0 versus 94.8 ± 18.4 μM · h; P &lt; 0.001). The American Society for Pharmacology and Experimental Therapeutics