M. Chang et al., METABOLISM OF THE HIV-1 REVERSE-TRANSCRIPTASE INHIBITOR DELAVIRDINE IN MICE, Drug metabolism and disposition, 25(7), 1997, pp. 828-839
Delavirdine mesylate (U-90152T) is a highly specific nonnucleoside HIV
-1 reverse transcriptase inhibitor currently under development for the
treatment of AIDS. The excretion, disposition, brain penetration, and
metabolism of delavirdine were investigated in CD-1 mice after oral a
dministration of [C-14]delavirdine mesylate at single doses of 10 and/
or 250 mg/kg and multiple doses of 200 mg/kg/day. Studies were conduct
ed with C-14-carboxamide and 2-C-14-pyridine labels, as well as C-13(3
)-labeled drug to facilitate metabolite identification. Excretion was
dose dependent with 57-70% of the radioactivity eliminated in feces an
d 25-36% in urine. Pharmacokinetic analyses of delavirdine and its N-d
esisopropyl metabolite (desalkyl delavirdine) in plasma showed that de
lavirdine was absorbed and metabolized rapidly, that it constituted a
minor component in circulation, that its pharmacokinetics were nonline
ar, and that its metabolism to desalkyl delavirdine was capacity limit
ed or inhibitable. Delavirdine did not significantly cross the blood-b
rain barrier; however, its N-isopropylpyridinepiperazine metabolite--a
rising from amide bond cleavage--was present in brain at levels 2- to
3-fold higher than in plasma. The metabolism of delavirdine in the mou
se was extensive and involved amide bond cleavage, N-desalkylation, hy
droxylation at the C-6' position of the pyridine ring, and pyridine ri
ng-cleavage as determined by MS and/or H-1 and C-13 NMR spectroscopies
. N-desalkylation and amide bond cleavage were the primary metabolic p
athways at low drug doses and, as the biotransformation of delavirdine
to desalkyl delavirdine reached saturation or inhibition, amide bond
cleavage became the predominant pathway at higher doses and after mult
iple doses.