CCR5小分子拮抗剂类抗艾滋病药物研究进展

趋化因子受体CCR5是抗艾滋病药物作用的重要靶点之一。目前，已经开发了许多活性强、选择性高的CCR5拮抗剂，其中一部分已进入临床试验阶段。本文对近年来文献报道的CCR5小分子拮抗剂进行综述。     

Beta-diketo acid pharmacophore hypothesis. 1. Discovery of a novel class of HIV-1 integrase inhibitors

HIV-1 Integrase (IN) is an essential enzyme for viral replication. The discovery of beta-diketo acids was crucial in the validation of IN as a legitimate target in drug discovery against HIV infection. In this study, we discovered a novel class of IN inhibitors using a 3D pharmacophore guided database search. We used S-1360 (1), the first IN inhibitor to undergo clinical trials, and three other analogues to develop a common feature pharmacophore hypothesis. Testing this four-featured pharmacophore against a multiconformational database of 150,000 structurally diverse small molecules yielded 1,700 compounds that satisfied the 3D query. Subsequently, all 1,700 compounds were docked into the active site of IN. On the basis of docking scores, Lipinski's rule-of-five, and structural novelty, 110 compounds were selected for biological screening. We found that compounds that contain both salicylic acid and a 2-thioxo-4-thiazolidinone (rhodanine) group (e.g. 5-13) showed significant inhibitory potency against IN, while the presence of either salicylic acid or a rhodanine group alone did not. Although some of the compounds containing only a salicylic acid showed inhibitory potency against IN, none of the compounds containing only rhodanine exhibited considerable potency. Of the 52 compounds reported in this study, 11 compounds (5, 6, 8, 10-13, 32-33, 51, and 53) inhibited 3'-processing or strand transfer activities of IN with IC(50) < or = 25 microM. This is the first reported use of S-1360 and its analogues as leads in developing a pharmacophore hypothesis for IN inhibition and for identification of new compounds with potent inhibition of this enzyme.     

Vicriviroc: a CCR5 antagonist for treatment-experienced patients with HIV-1 infection

Background: Despite the availability of 31 antiretroviral agents or fixed-dose combinations in the United States and European Union, there is a continuing need for antiretroviral agents with high genetic barriers to resistance, simple dosing schedules, and favorable tolerability and safety profiles. Vicriviroc is a small-molecule chemokine receptor antagonist that inhibits the binding of R5-tropic HIV-1 to host cells at the CCR5 co-receptor, thus preventing viral entry. Objective: To present an evidence-based assessment of the clinical efficacy, pharmacokinetics, and safety profile of vicriviroc. Method: We discuss available peer-reviewed publications as well as preliminary data presented at relevant scientific meetings. Results/conclusions: Vicriviroc has a favorable pharmacokinetic profile with a half-life that enables once-daily dosing. Minimal drug interactions have been demonstrated with other available antiretrovirals. Early clinical trials have established the safety of vicriviroc in both treatment-naive and treatment-experienced R5-tropic HIV-1 infected individuals. A Phase II study in treatment-experienced patients demonstrated early efficacy of 30 mg vicriviroc in a regimen containing a ritonavir-boosted protease inhibitor (PI/r). Phase III studies using the 30-mg PI/r dosing paradigm in R5-tropic treatment-experienced patients have completed 48 weeks, but data are not yet available. These results will further elucidate the role of vicriviroc in the treatment of HIV-1 infected individuals.     

5-HT7 receptor antagonists as a new class of antidepressants

It is now admitted that major depression is associated with monoaminergic dysfunctions as well as with functional brain plasticity impairments. Despite the wide variety of medications available to treat such a syndrome, two foremost problems still remain unresolved: one-third of patients do not respond to any treatment and there is an unwanted 2-4 week delay in the onset of therapeutic action of all available antidepressant drugs. These issues draw attention to the need and urgency to develop more efficacious treatments and to accelerate the antidepressant response. The combination of an atypical antipsychotic, known to be a potent 5-HT(7) receptor antagonist, with an antidepressant has been recently proposed as an alternative therapy. Hence, blockade of 5-HT(7) receptors might represent a key determinant for this hastening strategy. This review summarizes recent data that put emphasis on the putative antidepressant properties of selective 5-HT(7) receptor antagonists. The use of such ligands seems very promising to elaborate novel generations of antidepressants that surpass the efficacy and onset of action limitations of existing antidepressants.     

The current status of, and challenges in, the development of CCR5 inhibitors as therapeutics for HIV-1 infection

The discovery of CCR5 as a HIV-1 co-receptor unfolded the cryptic and complicated process of HIV-1 cellular entry and has provided more than a few entry steps as possible modalities for effective viral intervention. The proof-of-principle has already been established for the use of entry inhibitors against HIV-1 and there is a cautious optimism that several CCR5 inhibitors might soon be added to our armamentarium for therapy of HIV-1 infection.     

Transgenic mouse expressing human CCR5 as a model for in vivo assessments of human selective CCR5 antagonists

The species selectivity of receptor antagonists often hinders their preclinical assessment in vivo. In order to evaluate human selective CC chemokine receptor type 5 (CCR5) antagonists in vivo, we generated human CCR5 transgenic mice that expressed the transgene on both peripheral blood leukocytes as well as thymocytes. The selective CCR5 ligand CC chemokine ligand 4 (CCL4)/macrophage inflammatory protein (MIP)-1beta induced the chemotaxis of thymocytes that had been derived from the transgenic mice, but not from littermate mice, suggesting that the human CCR5 expressed in the transgenic mice were functional. The binding of the human CCR5 specific antibody 45531 to peripheral blood granulocytes from the transgenic mice was inhibited by human selective CCR5 antagonist SCH-351125. Using this antibody, we developed an ex vivo assay system that is suitable for the evaluation of a test compound's ability to occupy the human CCR5 receptor on mouse peripheral blood leukocytes. This transgenic mouse model is useful for estimating the pharmacodynamics of human selective CCR5 antagonists in vivo.     

Urea-PETT compounds as a new class of HIV-1 reverse transcriptase inhibitors. 3. Synthesis and further structure-activity relationship studies of PETT analogues.

The further development of allosteric HIV-1 RT inhibitors in the urea analogue series of PETT (phenylethylthiazolylthiourea) derivatives is described here. The series includes derivatives with an ethyl linker (1-5) and racemic (6-16) and enantiomeric (17-20) cis-cyclopropane compounds. The antiviral activity was determined both at the RT level and in cell culture on both wild-type and mutant forms of HIV-1. Most compounds have anti-HIV-1 activity on the wt in the nanomolar range. Resistant HIV-1 was selected in vitro for some of the compounds, and the time for resistant HIV-1 to develop was longer for urea-PETT compounds than it was for reference compounds. Preliminary pharmacokinetics in rats showed that compound 18 is orally bioavailable and penetrates well into the brain. The three-dimensional structure of complexes between HIV-1 RT and two enantiomeric compounds (17 and 18) have been determined. The structures show similar binding in the NNI binding pocket. The propionylphenyl moieties of both inhibitors show perfect stacking to tyrosine residues 181 and 188. The cyclopropyl moiety of the (+)-enantiomer 18 exhibits optimal packing distances for the interactions with leucine residue 100 and valine residue 179.     

Generation of N-methyl-D-aspartate agonist and competitive antagonist pharmacophore models. Design and synthesis of phosphonoalkyl-substituted tetrahydroisoquinolines as novel antagonists.

The preparation and binding affinity of a series of tetrahydroisoquinoline carboxylic acids at the N-methyl-D-aspartate (NMDA) subtype of the glutamate receptor is described, together with a molecular modeling analysis of NMDA agonists and antagonists. Using published NMDA ligands, the active analogue mapping approach was employed in the generation of an agonist pharmacophore model. Although known competitive antagonists such as CPP (1) could be superimposed onto the agonist model, to overcome the assumption that they bind to the same receptor site, an independent modeling approach was used to derive a separate pharmacophore model. Development of a competitive antagonist model involved a stepwise approach that included the definition of a preferred geometry for PO3H2-receptor interactions, multiple conformational searches, and the determination of volume and electronic tolerances. This model, which is described in detail, is consistent with observed affinities of potent NMDA antagonists and has provided an explanation for the observed periodicity in affinities for the known antagonists AP5, AP6, and AP7. The features of the agonist and antagonist models are compared, and hypotheses advanced about the nature of the receptor interactions for these two classes of compounds. The pharmacophore models reported herein are consistent with a single recognition site at the NMDA receptor that can accommodate both agonist and antagonist ligands. To assist in first defining and later exploring the predictive power of the competitive antagonist model, a series of conformationally constrained NMDA antagonist (phosphonoalkyl)tetrahydroisoquinoline-1- and 3-carboxylates was prepared. From this work, 1,2,3,4-tetrahydro-5-(2-phosphonoethyl)-3- isoquinolinecarboxylic acid (89) was identified as the most active lead structure, with an IC50 of 270 nM in [3H]CPP binding. The synthesis and structure-activity relationships of these novel antagonists are described.     

CCR5 chemokine receptors: gatekeepers of HIV-1 infection

With the discovery that CCR5 is the critical protein required for infection by M-tropic HIV, has come huge research efforts, both in academia and industry, to try to exploit this finding. Thus, research advances in the fields of virology, structural protein chemistry, and receptor pharmacology have combined to add a new understanding to the process of HIV fusion and possible mechanisms to prevent HIV entry. This review will approach this field from a receptor pharmacology viewpoint and outline some concepts of receptor allosterism and protein-protein interaction which may be relevant to CCR5 blockade. Many of these ideas may be explored in a practical sense with the advent of new small molecule CCR5 inhibitors currently entering the clinic.     

新型抗艾滋病药物——HIV进入抑制剂的研究进展

HIV与靶细胞融合的过程是药物干预的重要环节。融合过程主要由H IV包被蛋白表面亚基gp120和跨膜亚基gp41介导。H IV gp120与靶细胞上的CD4分子和辅助受体(趋化因子受体CCR5或CXCR4等)结合,导致gp41的构型发生改变,启动病毒包膜与靶细胞膜的融合。在融合过程中,病毒和靶细胞上的这些蛋白和受体均可作为药物的作用靶点,寻找抑制H IV进入靶细胞的药物用来治疗H IV感染和艾滋病。作用于gp41的肽类药物T-20已被美国FDA批准上市,表明继逆转录酶抑制剂和蛋白酶抑制剂后,H IV进入抑制剂作为第3类抗H IV药物开始在临床上应用。作为一种新机制的抗H IV药物,H IV进入抑制剂单独或与逆转录酶抑制剂和蛋白酶抑制剂联合应用,将有助于提高药物的疗效,降低毒副作用,并可望挽救对现有抗H IV药物耐药的艾滋病病人的生命。该文综述了近年来H IV进入抑制剂的研究进展。     

Discovery of a piperidine-4-carboxamide CCR5 antagonist (TAK-220) with highly potent Anti-HIV-1 activity

We incorporated various polar groups into previously described piperidine-4-carboxamide CCR5 antagonists to improve their metabolic stability in human hepatic microsomes. Introducing a carbamoyl group into the phenyl ring of the 4-benzylpiperidine moiety afforded the less lipophilic compound 5f, which possessed both high metabolic stability and good inhibitory activity of HIV-1 envelope-mediated membrane fusion (IC(50) = 5.8 nM). Further optimization to increase potency led to the discovery of 1-acetyl-N-{3-[4-(4-carbamoylbenzyl)piperidin-1-yl]propyl}-N-(3-chloro-4-methylphenyl)piperidine-4-carboxamide (5m, TAK-220), which showed high CCR5 binding affinity (IC(50) = 3.5 nM) and potent inhibition of membrane fusion (IC(50) = 0.42 nM), as well as good metabolic stability. Compound 5m strongly inhibited the replication of CCR5-using HIV-1 clinical isolates in human peripheral blood mononuclear cells (mean EC(50) = 1.1 nM, EC(90) = 13 nM) and exhibited a good pharmacokinetic profile in monkeys (BA = 29%). This compound has been chosen as a clinical candidate for further development.     

An intracellular allosteric site for a specific class of antagonists of the CC chemokine G protein-coupled receptors CCR4 and CCR5

A novel mechanism for antagonism of the human chemokine receptors CCR4 and CCR5 has been discovered with a series of small-molecule compounds that seems to interact with an allosteric, intracellular site on the receptor. The existence of this site is supported by a series of observations: 1) intracellular access of these antagonists is required for their activity; 2) specific, saturable binding of a radiolabeled antagonist requires the presence of CCR4; and 3) through engineering receptor chimeras by reciprocal transfer of C-terminal domains between CCR4 and CCR5, compound binding and the selective structure-activity relationships for antagonism of these receptors seem to be associated with the integrity of that intracellular region. Published antagonists from other chemical series do not seem to bind to the novel site, and their interaction with either CCR4 or CCR5 is not affected by alteration of the C-terminal domain. The precise location of the proposed binding site remains to be determined, but the known close association of the C-terminal domain, including helix 8, as a proposed intracellular region that interacts with transduction proteins (e.g., G proteins and beta-arrestin) suggests that this could be a generic allosteric site for chemokine receptors and perhaps more broadly for class A G protein-coupled receptors. The existence of such a site that can be targeted for drug discovery has implications for screening assays for receptor antagonists, which would need, therefore, to consider compound properties for access to this intracellular site.