Enhanced pharmacokinetic properties of 1,4-benzodiazepine-2,5-dione antagonists of the HDM2-p53 protein-protein interaction through structure-based drug design

Guided by structure-based drug design, modification of the 1,4-benzodiazepin-2,5-dione lead compound 1 resulted in the discovery of 19, a potent and orally bioavailable antagonist of the HDM2-p53 protein-protein interaction (FP IC50 = 0.7 microM, F approximately 100%).     

Enantiomerically pure 1,4-benzodiazepine-2,5-diones as Hdm2 antagonists

The 1,4-benzodiazepine-2,5-dione is a suitable template to disrupt the interaction between p53 and Hdm2. The development of an enantioselective synthesis disclosed the stereochemistry of the active enantiomer. An in vitro p53 peptide displacement assay identified active compounds. These activities were confirmed in several cell-based assays including induction of the p53 regulated gene (PIG-3) and caspase activity.     

Novel 1,4-benzodiazepine-2,5-diones as Hdm2 antagonists with improved cellular activity

The disruption of the p53-Hdm2 protein-protein interaction induces cell growth arrest and apoptosis. We have identified the 1,4-benzodiazepine-2,5-dione scaffold as a suitable template for inhibiting this interaction by binding to the Hdm2 protein. Several compounds have been made with improved potency, solubility, and cell-based activities.     

Discovery and SAR of small molecule PAR1 antagonists

High-throughput screening resulted in the identification of a small molecule inhibitor of PAR1. Optimisation of the initial hit led to the discovery of compounds 34 and 49, which displayed antithrombotic activity in an arteriovenous shunt model in the rat after iv administration.     

1,4-Diazepane-2,5-diones as novel inhibitors of LFA-1

1,4-Diazepane-2,5-diones (2) are found to be a new class of potent LFA-1 inhibitors. The synthesis, structure, and biological evaluation of these 1,4-diazepine-2,5-diones and related derivatives are described.     

Synthesis and SAR of selective small molecule neuropeptide Y Y2 receptor antagonists

Highly potent and selective small molecule neuropeptide Y Y2 receptor antagonists are reported. The systematic SAR exploration of a hit molecule N-(4-ethoxyphenyl)-4-[hydroxy(diphenyl)methyl]piperidine-1-carbothioamide, identified from HTS, led to the discovery of highly potent NPY Y2 antagonists 16 (CYM 9484) and 54 (CYM 9552) with IC(50) values of 19 nM and 12 nM respectively.     

Structure-based design, synthesis, and biological evaluation of novel 1,4-diazepines as HDM2 antagonists

Crystallographic analysis of ligands bound to HDM2 suggested that 7-substituted 1,4-diazepine-2,5-diones could mimic the alpha-helix of p53 peptide and may represent a promising scaffold to develop HDM2-p53 antagonists. To verify this hypothesis, we synthesized and biologically evaluated 5-[(3S)-3-(4-chlorophenyl)-4-[(R)-1-(4-chlorophenyl)ethyl]-2,5-dioxo-7-phenyl-1,4-diazepin-1-yl]valeric acid (10) and 5-[(3S)-7-(2-bromophenyl)-3-(4-chlorophenyl)-4-[(R)-1-(4-chlorophenyl)ethyl]-2,5-dioxo-1,4-diazepin-1-yl]valeric acid (11). Preliminary in vitro testing shows that 10 and 11 substantially antagonize the binding between HDM2 and p53 with an IC(50) of 13 and 3.6 microM, respectively, validating the modeling predictions. Taken together with the high cell permeability of diazepine 11 determined in CACO-2 cells, these results suggest that 1,4-diazepine-2,5-diones may be useful in the treatment of certain cancers.     

Synthesis and amphiphilic properties of glycosyl-1,4-benzodiazepin-2,5-diones

Glycosyl-1,4-benzodiazepin-2,5-diones were prepared by coupling polyhydroxylated groups at N-1 of the corresponding benzodiazepine. The groups include 1-deoxy-D,L-xylit-1-yl, 6-deoxy-D-glucopyranos-6-yl, and 6-deoxy-3-OR-D-glucopyranos-6-yl (R = n-CnH(2n +1); n = 8, 12, and 16). The structural variations of the sugar group allowed comparison of such amphiphilic data as water solubility (Sw), critical micelle concentration (CMC), and corresponding surface tension (gamma) values. At 25 degrees C, unsubstituted benzodiazepines have Sw values from 0.9 to 4.2 10(-3) mol L(-1), whereas xylit-1-yl and 6-deoxy-D-glucopyranos-6-yl derivatives are, respectively, 7.4-25 and 58-204 times more soluble. Also, compounds with R = n-C8H17 are more soluble than corresponding benzodiazepines (1.4-5.8 times) and give micelles with CMC from 2.7 to 5.6 10(-3) mol L(-1) and corresponding gamma from 29 to 37 mN m(-1). In contrast, compounds with R = n-C12H25 and n-C16H33 are not soluble enough to reach the critical micelle concentration.     

Alpha-aminothiazole-gamma-aminobutanoic amides as potent, small molecule CCR2 receptor antagonists

A series of racemic and homochiral alpha-aminothiazole-gamma-aminobutyroamides that display high affinities for human and murine CCR2 and functional antagonism by inhibition of monocyte recruitment are described. A representative example is (2S)-2-[2-(acetylamino)-1,3-thiazol-4-yl]-N-[3-methyl-5-(trifluoromethyl)benzyl]-4-(4-phenylpiperidin-1-yl)butanamide, which shows 5 nM affinity for human monocytes and CHO cells expressing the human CCR2b receptor. It also inhibited MCP-1 initiated chemotaxis of human monocytes with an IC50 of 0.69 nM.     

p53 promotes its own polyubiquitination by enhancing the HDM2 and HDMX interaction

HDM2 and HDMX are two homologs essential for controlling p53 tumor suppressor activity under normal conditions. Both proteins bind different sites on the p53 N‐terminus, and while HDM2 has E3 ubiquitin ligase activity towards p53, HDMX does not. Nevertheless, HDMX is required for p53 polyubiquitination and degradation, but the underlying molecular mechanism remains unclear. Alone, HDMX and HDM2 interact via their respective C‐terminal RING domains but here we show that the presence of p53 induces an N‐terminal interface under normal cellular conditions. This results in an increase in HDM2‐mediated p53 polyubiquitination and degradation. The HDM2 inhibitor Nutlin‐3 binds the N‐terminal p53 binding pocket and is sufficient to induce the HDM2‐HDMX interaction, suggesting that the mechanism depends on allosteric changes that control the multiprotein complex formation. These results demonstrate an allosteric interchange between three different proteins (HDMX‐HDM2‐p53) and help to explain the molecular mechanisms of HDM2‐inhibitory drugs.     

Regulation of the HDM2-p53 pathway by ribosomal protein L6 in response to ribosomal stress

The HDM2-p53 loop is crucial for monitoring p53 level and human pathologies. Therefore, identification of novel molecules involved in this regulatory loop is necessary for understanding the dynamic regulation of p53 and treatment of human diseases. Here, we characterized that the ribosomal protein L6 binds to and suppresses the E3 ubiquitin ligase activity of HDM2, and subsequently attenuates HDM2-mediated p53 polyubiquitination and degradation. The enhanced p53 activity further slows down cell cycle progression and leads to cell growth inhibition. Conversely, the level of p53 is dramatically decreased upon the depletion of RPL6, indicating that RPL6 is essential for p53 stabilization. We also found that RPL6 translocalizes from the nucleolus to nucleoplasm under ribosomal stress, which facilitates its binding with HDM2. The interaction of RPL6 and HDM2 drives HDM2-mediated RPL6 polyubiquitination and proteasomal degradation. Longer treatment of actinomycin D increases RPL6 ubiquitination and destabilizes RPL6, and thereby putatively attenuates p53 response until the level of L6 subsides. Therefore, RPL6 and HDM2 form an autoregulatory feedback loop to monitor the level of p53 in response to ribosomal stress. Together, our study identifies the crucial function of RPL6 in regulating HDM2-p53 pathway, which highlights the importance of RPL6 in human genetic diseases and cancers.     

4-Amino-2-alkyl-butyramides as small molecule CCR2 antagonists with favorable pharmacokinetic properties

A systematic examination of the central aromatic portion of the lead (2S)-N-[3,5-bis(trifluoromethyl)benzyl]-2-(4-fluorophenyl)-4-(1'H-spiro[indene-1,4'-piperidin]-1'-yl)butanamide (9) led to the discovery of a novel class of CCR2 receptor antagonists, which carry small alicyclic groups such as cyclopropyl, cylobutyl, or cyclopropylmethyl attached at C2 of the carbon backbone. The most potent compound discovered, namely (2S)-N-[3,5-bis(trifluoromethyl)benzyl]-2-cyclopropyl-4-[(1R,3'R)-3'-methyl-1'H-spiro[indene-1,4'-piperidin]-1'-yl]butanamide (29), showed very high binding affinity (IC50 = 4 nM, human monocyte) and excellent selectivity toward other related chemokine receptors. The excellent pharmacokinetic profile of this new lead compound allows for extensive in vivo evaluation.     

2,5-Diketopiperazines as potent and selective oxytocin antagonists 1: Identification, stereochemistry and initial SAR

This paper covers efforts to discover orally active potent and selective oxytocin antagonists. Screening pooled libraries identified a novel series of 2,5-diketopiperazine derivatives with antagonist activity at the human oxytocin receptor. We report the initial structure-activity relationship investigations and the determination of the stereochemistry of the most potent compounds.     

Synthesis and SAR of novel di- and trisubstituted 1,4-dihydroquinoxaline-2,3-diones related to licostinel (Acea 1021) as NMDA/glycine site antagonists

A series of novel di- and trisubstituted 1,4-dihydroquinoxaline-2,3-diones (QXs) related to licostinel (Acea 1021) was synthesized and evaluated as antagonists for the glycine site of the N-methyl-D-asparate (NMDA) receptor. The in vitro potency of these antagonists was determined by displacement of the glycine site radioligand [(3)H]-5,7-dichlorokynurenic acid ([(3)H]DCKA) in rat brain cortical membranes. Structure-activity relationship studies indicate that a cyano group is a good replacement for the nitro group in the 5-position of licostinel while 5-carboxy, 5-ester, 5-ketone and 5-amide derivatives showed reduced potency. 5,6-Cyclized analogues of licostinel also showed significantly reduced potency. Among the trisubstituted QXs investigated, 5-cyano-6,7-dichloro QX and 5-cyano-7-chloro-6-methyl QX are the most potent with IC(50) values of 32 nM and 26 nM, respectively.     

Inhibition of human papillomavirus DNA replication by small molecule antagonists of the E1-E2 protein interaction

Human papillomavirus (HPV) DNA replication is initiated by recruitment of the E1 helicase by the E2 protein to the viral origin. Screening of our corporate compound collection with an assay measuring the cooperative binding of E1 and E2 to the origin identified a class of small molecule inhibitors of the protein interaction between E1 and E2. Isothermal titration calorimetry and changes in protein fluorescence showed that the inhibitors bind to the transactivation domain of E2, the region that interacts with E1. These compounds inhibit E2 of the low risk HPV types 6 and 11 but not those of high risk HPV types or of cottontail rabbit papillomavirus. Functional evidence that the transactivation domain is the target of inhibition was obtained by swapping this domain between a sensitive (HPV11) and a resistant (cottontail rabbit papillomavirus) E2 type and by identifying an amino acid substitution, E100A, that increases inhibition by approximately 10-fold. This class of inhibitors was found to antagonize specifically the E1-E2 interaction in vivo and to inhibit HPV DNA replication in transiently transfected cells. These results highlight the potential of the E1-E2 interaction as a small molecule antiviral target.