Synthesis and antifungal activity of ASP9726, a novel echinocandin with potent Aspergillus hyphal growth inhibition.

The synthesis and antifungal activity of ASP9726, a novel echinocandin with potent Aspergillus hyphal growth inhibition and significantly improved MIC against Candida parapsilosis and echinocandin resistant-Candida is described.

Discovery of highly potent and selective biphenylacylsulfonamide-based beta3-adrenergic receptor agonists and molecular modeling based on the solved X-ray structure of the beta2-adrenergic receptor: part 6.

As an extension of research, we have investigated modification of left-hand side (LHS) of biphenyl analogues containing an acylsulfonamide moiety in the development of potent and selective human beta(3)-adrenergic receptor (AR) agonists. Result of structure-activity relationships (SAR) and cassette-dosing evaluation in dogs showed that the hydroxynorephedrine analogue 16 had an excellent balance of in vitro and in vivo potency with pharmacokinetic profiles. In addition, to facilitate structure-based drug design (SBDD), we also have performed a docking study of biphenyl analogues based on the X-ray structure of the beta(2)-adrenergic receptor.

Structure-activity relationships of cyclic peptide-based chemokine receptor CXCR4 antagonists: disclosing the importance of side-chain and backbone functionalities.

Previously, we have identified a highly potent CXCR4 antagonist 2 [cyclo(-D-Tyr1-Arg2-Arg3-Nal4-Gly5-)] and its Arg2 epimer 3 [cyclo(-D-Tyr1-D-Arg2-Arg3-Nal4-Gly5-)] by the screening of cyclic pentapeptide libraries that were designed based on the structure-activity relationship studies on 14-residue peptidic CXCR4 antagonist 1. In the present study, a new series of analogues of 2 and 3 were synthesized to evaluate the influences of peptide side-chain and backbone modification on bioactivities. Based on the Ala-scanning study, in which each residue in 2 and 3 was replaced with Ala having the identical chirality, substitution of Arg3 and Nal4 [Nal = L-3-(2-naphthyl)alanine] with Ala (compounds 6, 7, 10, 11) led to significant loss of the potency, indicating these amino acids are more important contributors to the bioactivity. For the cyclic peptide backbone, several modifications including d/l-Ala or cyclic amino acids substitution at the Gly5 position and sequential N-methylation on amide nitrogens were conducted. Among the analogues, compounds 13 [cyclo(-D-Tyr1-Arg2-Arg3-Nal4-D-Ala5-)] and 32 [cyclo(-D-Tyr1-D-MeArg2-Arg3-Nal4-Gly5-)] were close in potency to the most potent lead 2. NMR and conformational analysis indicated that both of these analogues favor the same backbone conformation as 2, whereas similar analysis of less potent analogues indicates that an altered backbone conformation is favored. The conformational analysis showed that steric repulsion by a 1,3-allylic strain-like effect across the planar peptide bond might contribute to the conformational preferences of cyclic pentapeptides.

Identification of novel low molecular weight CXCR4 antagonists by structural tuning of cyclic tetrapeptide scaffolds.

A highly potent CXCR4 antagonist, compound 2, was previously found by using two orthogonal cyclic pentapeptide libraries involving conformation-based and sequence-based libraries based on the pharmacophore of a 14-mer peptidic antagonist, 1. Herein, cyclic tetrapeptides derived from replacements of the dipeptide unit (Nal-Gly) with a gamma-amino acid and pseudopeptides cyclized by disulfide and olefin bridges were synthesized to find novel scaffold structures different from that of cyclic pentapeptides. These compounds contain a reduced number of peptide bonds compared to compound 2. Furthermore, several analogues with chemical modification of the side chain of Arg(4) in 2 were also prepared. From these, several new leads possessing high to moderate CXCR4-antagonistic activity were characterized.

Discovery of highly potent and selective biphenylacylsulfonamide-based beta3-adrenergic receptor agonists and evaluation of physical properties as potential overactive bladder therapies: part 5.

As an extension of research conducted on beta(3)-adrenergic receptor agonists as potential drugs for treating overactive bladder (OAB), novel series containing an acylsulfonamide moiety instead of the carboxylic acid moiety were evaluated. These compounds have been identified as potent and selective human beta(3)-AR agonists with improved oral bioavailability compared to the previous series. Results of structure-activity relationship (SAR) studies and cassette dosing evaluation in dogs showed several analogues (namely, 6h, 6j, 6o, 7e, and 9e) to have an excellent balance of in vitro potency and selectivity, pharmacokinetic (PK) profile, and an in vivo OAB model. Here we examined the relaxation response in dog detrusor muscle strips to a KCl induced tonic concentration. Results showed that the potency of in vitro relaxation response was not mirrored in the potency of the cAMP accumulation in CHO cell lines. Surprisingly, the EC(50) values of 6e and 7e found to induce relaxation of isolated bladder strips were over 50-fold higher than the cAMP accumulation in cell line. In general, increased lipophilicity led to decreased potency for the bladder relaxation compared with cAMP accumulation in CHO cell lines, indicating that lipophilicity is crucial for OAB drug candidates to improve beta(3) activity.

Discovery of a novel series of biphenyl benzoic acid derivatives as highly potent and selective human beta3 adrenergic receptor agonists with good oral bioavailability. Part II.

The left-hand side (LHS) and central part of our first generation biphenyl (FGB) series was modified to improve in vitro and in vivo beta3-AR potency without loss of oral bioavailability. First, in this study, we focused our efforts on replacement of the 3-chlorophenyl moiety in the LHS of FGB analogues with 3-pyridyl ring analogues to adjust the lipophilicity. Second, we investigated the replacement of the central part of this series and discovered that introduction of a methyl group into the alpha-position of the phenethylamine moiety greatly enhanced potency keeping good oral availability. Finally, the replacement of the two carbon linker of the central part with an ethoxy-based linker provided improved potency and PK profiles. As a result of these studies, several analogues (i.e., 9h, 9k, 9l, 10g, 10m, 10p, 10r, 11b, and 11l) were identified that displayed an excellent balance of very higher human beta3-AR potency compared to the FGB compounds, high selectivity, and good pharmacokinetic profiles. Furthermore, these several compounds showed high in vivo efficacy in an overactive bladder (OAB) model. These findings suggest that our selected second generation biphenyl (SGB) series compounds may be attractive new successful therapeutic candidates for the treatment of OAB.

Therapeutic potential of the chemokine receptor CXCR4 antagonists as multifunctional agents.

The chemokine receptor CXCR4 possesses multiple critical functions in normal and pathologic physiology. CXCR4 is a G-protein-coupled receptor that transduces signals of its endogenous ligand, the chemokine CXCL12 (stromal cell-derived factor-1, SDF-1). The interaction between CXCL12 and CXCR4 plays an important role in the migration of progenitors during embryologic development of the cardiovascular, hemopoietic, central nervous systems, and so on. This interaction is also known to be involved in several intractable disease processes, including HIV infection, cancer cell metastasis, leukemia cell progression, rheumatoid arthritis (RA), and pulmonary fibrosis. It is conjectured that this interaction may be a critical therapeutic target in all of these diseases, and several CXCR4 antagonists have been proposed as potential drugs. Fourteen-mer peptides, T140 and its analogues, were previously developed in our laboratory as specific CXCR4 antagonists that were identified as HIV-entry inhibitors, anti-cancer-metastatic agents, anti-chronic lymphocytic/acute lymphoblastic leukemia agents, and anti-RA agents. Cyclic pentapeptides, such as FC131 [cyclo(D-Tyr-Arg-Arg-L-3-(2-naphthyl)alanine-Gly)], were also previously found as CXCR4 antagonist leads based on pharmacophores of T140. This review article describes the elucidation of multiple functions of CXCR4 antagonists and the development of a number of low-molecular weight CXCR4 antagonists involving FC131 analogues and other compounds with different scaffolds including linear-type structures.

Structure-activity relationship studies on CXCR4 antagonists having cyclic pentapeptide scaffolds.

Structure-activity relationship studies on CXCR4 antagonists, which were previously found by using cyclic pentapeptide libraries, were performed to optimize side-chain functional groups, involving conformationally constrained analogues. In addition, a new lead of cyclic pentapeptides with the introduction of a novel pharmacophore was developed.