The CCR5 Receptor-Based Mechanism of Action of 873140, a Potent Allosteric Noncompetitive HIV Entry Inhibitor

Abstract

4-{[4-({(3R)-1-Butyl-3-[(R)-cyclohexyl(hydroxy)methyl]-2,5dioxo-1,4,9-triazaspiro[5.5]undec-9-yl}methyl)phenyl]oxy}benzoic acid hydrochloride (873140) is a potent noncompetitive allosteric antagonist of the CCR5 receptor (pK B ϭ 8.6 Ϯ 0.07; 95% CI, 8.5 to 8.8) with concomitantly potent antiviral effects for HIV-1. In this article, the receptor-based mechanism of action of 873140 is compared with four other noncompetitive allosteric antagonists of CCR5. Although 857), and N, with an allosteric mechanism of action. The blockade of CCR5 by 873140 was extremely persistent with a rate constant for reversal of Ͻ0.004 h Ϫ1 (t 1/2 Ͼ 136 h). Coadministration studies of 873140 with the four other allosteric antagonists yielded data that are consistent with the notion that all five of these antagonists bind to a common allosteric site on the CCR5 receptor. Although these ligands may have a common binding site, they do not exert the same allosteric effect on the receptor, as indicated by their differential effects on the binding of 125 I-RANTES. This idea is discussed in terms of using these drugs sequentially to overcome HIV viral resistance in the clinic.With the discovery that the R5 strain of HIV uses the chemokine C CCR5 receptor for cell infection (Alkhatib et al., 1996;Choe et al., 1996;Doranz et al., 1996; Dragic et al., 1996;Deng et al., 1997;Shieh et al., 1998;Zhang and Moore, 1999) has come the opportunity for a completely new approach to preventing HIV infection: blockade of CCR5 receptor interaction with the viral coat protein gp120. Subsequent reports of potent antagonists of CCR5-mediated HIV entry (Baba et al., 1999;Finke et al., 2001;Strizki et al., 2001;Kazmierski et al., 2003; Demarest et al., 2004a,b, Maeda et al., 2004 have validated this approach and have possibly opened a new era of AIDS therapy. There are data to support the notion that an allosteric mechanism is involved in the antagonism of HIV by low molecular weight antagonists of CCR5 (Kazmierski et al., 2002). The large size of the proteins involved in HIV fusion (i.e., CCR5 and gp120) and the fact that mutational studies indicate that numerous regions of both CCR5 (Atchison et al., 1996;Rucker et al., 1996;Doms and Peiper, 1997;Doranz et al., 1997;Picard et al., 1997 ABBREVIATIONS: MIP-1␣, macrophage inflammatory protein 1-alpha (standard nomenclature CCL3, also known as LD78); CHO, Chinese hamster ovary; SPA, scintillation proximity assay; DMSO, dimethyl sulfoxide; RT, room temperature; HEK, human embryonic kidney; FLIPR, fluorometric imaging plate reader; RANTES, regulated on activation, normal T cell expressed and secreted (standard nomenclature for this chemokine is CCL5); Sch-C (SCH 351125), (Z)-(4-bromophenyl

HIV-1 Resistance to CCR5 Antagonists Associated with Highly Efficient Use of CCR5 and Altered Tropism on Primary CD4 + T Cells

“…Small-molecule CCR5 antagonists bind to a hydrophobic pocket in the transmembrane helices of CCR5 and exert their effects on HIV by altering the position of the ECLs, making them allosteric inhibitors of HIV infection (13,31,32,46,52). The conformational changes in CCR5 that are induced by CCR5 antagonists vary to some degree with different drugs, as evidenced by differential binding of antibodies and chemokines to various drug-bound forms of CCR5 (47,54).…”

Chemokine Receptors as Therapeutic Targets in HIV Infection

“…The results of recent biochemical studies support the noncompetitive and allosteric nature of the mechanism of action of small molecule antagonists of CCR5 [104]. The difference in binding sites between the two ligands also supports the allosteric modulation of the HIV-1 gp120 binding site by this class of drugs; as mentioned above, CCR5 inhibitors bind within the TM helices in the extracellular facet of the coreceptor, whereas HIV gp120 targets the extracellular domains of CCR5 and, more specifically, the negatively-charged Tyr-sulfated amino terminus (Nt) and the ECL2 between TM helices 4 and 5 [103].…”

“…More specifically, the binding "pocket" of such molecules as TAK-779, AD101, and SCH-C is thought to be located between TM helices 1-3, and 7; other TM helices, particularly helix 6, contribute to some compound-specific variations [102,103]. Simultaneous administration of multiple antagonists showed that, indeed, they bind to a common site on CCR5 [104]. A key set of aromatic and aliphatic residues that serve as a hydrophobic core for this ligand binding pocket has also been identified, while a glutamic acid (Glu) in helix 7, E283, appears to be critical for high affinity interaction; this residue probably acts as the counterion for a positively charged nitrogen atom common to TAK-779, AD101, and SCH-C [105].…”

Closing the door to human immunodeficiency virus

“…Chemokine-induced CCR5 signaling is also blocked by Aplaviroc (Maeda et al, 2004). Co-administration of Aplaviroc with other CCR5 allosteric inhibitors in blocking MIP-1α binding showed an antagonistic effect, indicating that they may share a common site of action on CCR5 (Watson et al, 2005). Synergistic anti-HIV-1 activity was observed in the combination of Aplaviroc with reverse transcriptase inhibitors and T-20 (Nakata et al, 2008).…”