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Greater Synergistic Anti-HIV Effects upon Combinations of a CCR5 inhibitor AK602/ONO4128/GW873140 with CXCR4 Inhibitors than with Other Anti-HIV Drugs
Hirotomo Nakata*1, Y Koh1, K Maeda1, Y Takaoka2, H Tamamura3, N Fujii3, and H Mitsuya1,4
1Kumamoto Univ Sch of Med, Japan; 2Ono Pharma Co Ltd, Osaka, Japan; 3Grad Sch of Pharmaceutical Sci, Kyoto Univ, Sakyo-ku, Kyoto,Japan; and 4NCI, NIH, DHHS, Bethesda, MD, USA
Background: CCR5 represents a major chemokine receptor, which R5-HIV exploits in its entry to
target cells, thus serving as an attractive target for possible intervention of
R5-HIV infection. AK602/ONO4128/GW873140, a novel CCR5
inhibitor containing a unique spirodiketopiperazine
group, potently blocks in vitro the
infectivity of R5 HIV with subnanomolar IC50
and this compound is now under the phase II clinical trial. Here we determined
anti-HIV activity upon combinations of AK602 with various anti-HIV agents
including recently reported entry inhibitors.
Methods: PHA-stimulated peripheral
blood mononuclear cells (PBMC) were exposed to R5-HIVBaL or a 50:50 mixture of HIVBaL and X4-HIV104pre (HIVBaL/104pre) and anti-HIV
effects were monitored using p24 amounts. Two reverse transcriptase inhibitors
(zidovudine [AZT] andnevirapine
[NVP]), a protease inhibitor (indinavir [IDV]), a
fusion inhibitor (T-20), entry inhibitor (sCD4), 2 CCR5
inhibitors (TAK-779, Sch-C), and 2 CXCR4 inhibitors (AMD3100, TE14011) were used. Single drugs or
combinations of drugs were added to each well, using a fixed ratio among drugs
and serial dilution. Combination effects were defined to be “synergistic” (or
“antagonistic”) when the activity of drugs A+B was statistically greater (or “lesser”)
than “additive effect” of drug A+A and drug B+B, based on the Bliss
independence method. Statistical analyses were performed by using the
Mann-Whitney U test.
Results: Synergistic effects were
seen when AK602 was combined with AZT, NVP, IDV, sCD4, or T-20 against HIVBaL and HIVBaL/104pre. Mild synergism
was also observed with AK602 + TAK779. Additivism was
seen with AK602 + SCH-C. Most potent synergism was seen when AK602 was combined
with AMD3100 or TE14011 against HIV-1BaL/104pre. No antagonistic
anti-HIV effects or synergistic toxicity was seen in any combinations of 2
agents. Similar results were obtained when we analyzed the data using the
median-effect principle and are expressed as combination indices.
Conclusions: The present data suggest
that AK602 may have favorable anti-HIV interactions with other existing
anti-HIV drugs and the compound may serve as a potent therapeutic for HIV
treatment. Greater synergism with AK602 plus either of the 2 CXCR4 inhibitors
appeared to be explained by the presence of CD4, CCR5, and CXCR4 on target
cells as adjacently apposed homogenous microclusters.
Keywords: CCR5 inhibitor; drug interaction; HIV-1
