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Development of Novel Orally Bioavailable CXCR4 Antagonists, KRH-3955 and KRH-3140: Binding Specificity, Pharmacokinetics and Anti-HIV-1 Activity in vivo and in vitro
Yuetsu Tanaka*1, K Okuma1, R Tanaka1, S Kumakura2, A Shimoyamada2, K Hirose2, M Yanaka2, T Murakami3, and N Yamamoto3
1Univ of the Ryukyus, Okinawa, Japan; 2Kureha Corp. Tokyo, Japan; and 3Natl Inst of Infectious Diseases, Tokyo, Japan
Background: In the late
stage of HIV-1 infection, HIV-1 with phenotype of CXCR4 co-receptor tropism has
been linked to a rapid progression to AIDS. Thus, an ART in combination with a
CXCR4 antagonist that can interfere with the X4 HIV-1 infection may be advantageous
in preventing AIDS. In this study, we have generated 2 orally bioavailable CXCR4 antagonists, KRH-3955 and KRH-3140, that
showed extremely long and normal remaining time in vivo HH,
respectively. Using a hu-PBL-SCID mouse model, we
found that single oral administration with KRH-3955 or daily administration
with KRH-3140 in drinking water was capable of protecting the animals from X4
HIV-1 infection.
Methods: Antagonist activity
and specificity of the drugs were determined using various chemokine
receptor-expressing cells and their ligands. The
binding sites of the antagonists on CXCR4 were estimated using a library of
anti-human CXCR4 monoclonal antibodies. Their pharmacokinetic properties were
determined in rats by ARG. Preliminary in
vitro anti-X4 HIV-1 activity was determined by
using MT-4 cells and HIV-1IIIB. For in vivo study, C.B-17 SCID mice reconstituted with human peripheral
blood mononuclear cells (PBMC) were used. KRH-3955 was administrated by mouth. once (10
mg/kg), while KRH-3140 was administrated daily by mouth in drinking water (15
to 20 mg/kg/day). The drug-treated hu-PBL-SCID mice
were challenged with 5000 IU HIV-1NL4-3/animal intraperitoneally. 1 day after PBMC reconstitution. After
7 days from infection, cells were obtained from peritoneal lavage
and cultured in vitro in
IL-2-containing medium for determination of HIV-1 infection by p24 ELISA.
Results: KRH-3955 and
KRH-3140 specifically inhibited the binding of SDF-1 to CXCR4-exressing cells
but not those of the other chemokines to their
receptors. The binding sites of KRH-3955 and KRH-3140
were localized to first, second, and/or third, and first and/or second extracellular loops, respectively. EC50 of
KRH-3955 and KRH-3140 against X4 HIV-1 infection in vitro were 0.2 nM and 2.2 nM, respectively. The in vivo remaining time after oral
administration of KRH-3955 was very long and that of KRH-3140 was normal. Single or daily administration of KRH-3955 and KRH-3140,
respectively, efficiently protected hu-PBL-SCID mice
from X4 HIV-1 infection.
Conclusions: KRH3955 and
KRH-3140 are orally bioavailable CXCR4 antagonists
with potent anti-X4 HIV-1 activities in
vivo, indicating that these drugs may be desirable additives to an
anti-HIV-1 therapy.
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