Metal ion enhanced binding of AMD3100 to Asp262 in the CXCR4 receptor

The affinity of AMD3100, a symmetrical nonpeptide antagonist composed of two 1,4,8,11-tetraazacyclotetradecane (cyclam) rings connected through a 1,4-dimethylene(phenylene) linker to the CXCR4 chemokine receptor was increased 7, 36, and 50-fold, respectively, by incorporation of the following: Cu2+, Zn2+, or Ni2+ into the cyclam rings of the compound. The rank order of the transition metal ions correlated with the calculated binding energy between free acetate and the metal ions coordinated in a cyclam ring. Construction of AMD3100 substituted with only a single Cu2+ or Ni2+ ion demonstrated that the increase in binding affinity of the metal ion substituted bicyclam is achieved through an enhanced interaction of just one of the ring systems. Mutational analysis of potential metal ion binding residues in the main ligand binding crevice of the CXCR4 receptor showed that although binding of the bicyclam is dependent on both Asp171 and Asp262, the enhancing effect of the metal ion was selectively eliminated by substitution of Asp262 located at the extracellular end of TM-VI. It is concluded that the increased binding affinity of the metal ion substituted AMD3100 is obtained through enhanced interaction of one of the cyclam ring systems with the carboxylate group of Asp262. It is suggested that this occurs through a strong concomitant interaction of one of the oxygen's directly with the metal ion and the other oxygen to one of the nitrogens of the cyclam ring through a hydrogen bond

Optimization of potent inhibitors of P. falciparum dihydroorotate dehydrogenase for the treatment of malaria

Inhibition of dihydroorotate dehydrogenase (DHODH) for P. falciparum potentially represents a new treatment option for malaria, since DHODH catalyzes the rate-limiting step in the pyrimidine biosynthetic pathway and P. falciparum is unable to salvage pyrimidines and must rely on de novo biosynthesis for survival. We report herein the synthesis and structure-activity relationship of a series of 5-(2-methylbenzimidazol-1-yl)-N-alkylthiophene-2-carboxamides that are potent inhibitors against PfDHODH but do not inhibit the human enzyme. On the basis of efficacy observed in three mouse models of malaria, acceptable safety pharmacology risk assessment and safety toxicology profile in rodents, lack of potential drug-drug interactions, acceptable ADME/pharmacokinetic profile, and projected human dose, 5-(4-cyano-2-methyl-1H-benzo[d]imidazol-1-yl)-N-cyclopropylthiophene-2-carboxamide 2q was identified as a potential drug development candidat

The molecular pharmacology of AMD11070: An orally bioavailable CXCR4 HIV entry inhibitor

In order to enter and infect human cells HIV must bind to CD4 in addition to either the CXCR4 or the CCR5 chemokine receptor. AMD11070 was the first orally available small molecule antagonist of CXCR4 to enter the clinic. Herein we report the molecular pharmacology of AMD11070 which is a potent inhibitor of X4 HIV-1 replication and the gp120/CXCR4 interaction. Using the CCRF-CEM T cell line that endogenously expresses CXCR4 we have demonstrated that AMD11070 is an antagonist of SDF-1α ligand binding (IC(50)=12.5±1.3nM), inhibits SDF-1 mediated calcium flux (IC(50)=9.0±2.0nM) and SDF-1α mediated activation of the CXCR4 receptor as measured by a Eu-GTP binding assay (IC(50)=39.8±2.5nM) or a [(35)S]-GTPγS binding assay (IC(50)=19.0±4.1nM), and inhibits SDF-1α stimulated chemotaxis (IC(50)=19.0±4.0nM). AMD11070 does not inhibit calcium flux of cells expressing CXCR3, CCR1, CCR2b, CCR4, CCR5 or CCR7, or ligand binding to CXCR7 and BLT(1), demonstrating selectivity for CXCR4. In addition AMD11070 is able to inhibit the SDF-1β isoform interactions with CXCR4; and N-terminal truncated variants of CXCR4 with equal potency to wild type receptor. Further mechanistic studies indicate that AMD11070 is an allosteric inhibitor of CXCR4.status: publishe