Structure-activity relationships of pyrazole derivatives as potential therapeutics for immune thrombocytopenias.

Idiopathic or immune thrombocytopenia (ITP) is a serious clinical disorder involving the destruction of platelets by macrophages. Small molecule therapeutics are highly sought after to ease the burden on current therapies derived from human sources. Earlier, we discovered that dimers of five-membered heterocycles exhibited potential to inhibit phagocytosis of human RBCs by macrophages. Here, we reveal a structure-activity relationship of the bis-pyrazole class of molecules with -C-C-, -C-N- and -C-O- linkers, and their evaluation as inhibitors of phagocytosis of antibody-opsonized human RBCs as potential therapeutics for ITP. We have uncovered three potential candidates, 37, 47 and 50, all carrying a different linker connecting the two pyrazole moieties. Among these compounds, hydroxypyrazole derivative 50 is the most potent compound with an IC50 of 14 ± 9 µM for inhibiting the phagocytosis of antibody-opsonized human RBCs by macrophages. None of the compounds exhibited significant potential to induce apoptosis in peripheral blood mononuclear cells (PBMCs). Current study has revealed specific functional features, such as up to 2-atom spacer arm and alkyl substitution at one of the N(1) positions of the bivalent pyrazole core to be important for the inhibitory activity.

Small molecule mimetics of an interferon-α receptor interacting domain.

Small molecules that mimic IFN-α epitopes that interact with the cell surface receptor, IFNAR, would be useful therapeutics. One such 8-amino acid region in IFN-α2, designated IRRP-1, was used to derive 11 chemical compounds that belong to 5 distinct chemotypes, containing the molecular features represented by the key residues Leu30, Arg33, and Asp35 in IRRP-1. Three of these compounds exhibited potential mimicry to IRRP-1 and, in cell based assays, as predicted, effectively inhibited IFNAR activation by IFN-α. Of these, compound 3 did not display cell toxicity and reduced IFN-α-inducible STAT1 phosphorylation and STAT-DNA binding. Based on physicochemical properties' analyses, our data suggest that moieties with acidic pKa on the small molecule may be a necessary element for mimicking the carboxyl group of Asp35 in IRRP-1. Our data confirm the relevance of this strategy of molecular mimicry of ligand-receptor interaction domains of protein partners for small molecule drug discovery.

Guaifenesin derivatives promote neurite outgrowth and protect diabetic mice from neuropathy.

In diabetic patients, an early index of peripheral neuropathy is the slowing of conduction velocity in large myelinated neurons and a lack of understanding of the basic pathogenic mechanisms hindered therapeutics development. Racemic (R/S)-guaifenesin (1) was identified as a potent enhancer of neurite outgrowth using an in vitro screen. Its R-enantiomer (R)-1 carried the most biological activity, whereas the S-enantiomer (S)-1 was inactive. Focused structural variations to (R/S)-1 was conducted to identify potentially essential groups for the neurite outgrowth activity. In vivo therapeutic studies indicated that both (R/S)-1 and (R)-1 partially prevented motor nerve conduction velocity slowing in a mouse model of type 1 diabetes. In vitro microsomal assays suggested that compounds (R)-1 and (S)-1 are not metabolized rapidly, and PAMPA assay indicated moderate permeability through the membrane. Findings revealed here could lead to the development of novel drugs for diabetic neuropathy.

Disulfide linked pyrazole derivatives inhibit phagocytosis of opsonized blood cells.

Immune thrombocytopenia (ITP) is caused by production of an autoantibody to autologous platelets. ITP can be treated either by reducing platelet destruction or by increasing platelet production. Fcγ receptor mediated phagocytosis of the opsonized blood cells is a well-accepted mechanism for the underlying pathogenesis of ITP and inhibition of this phagocytosis process with small molecules is a potential strategy for the development of drugs against ITP. A broad screen indicated that 4-methyl-1-phenyl-pyrazole derivative (1) could inhibit the phagocytosis of opsonized blood cells with weak potency. We reveal here the discovery of the polysulfide products, synthesis of various 1-phenyl-pyrazole derivatives, and the biological evaluation of pyrazole derivatives as inhibitors of phagocytosis for potential use as therapeutics for ITP. Substitution at C4 of the pyrazole moiety in the disulfide-bridged dimers influenced the potency in the increasing order of 10 ~/= 11~/= 16 < 19 < 20. A novel scaffold, 20 with an IC(50) of 100 nM inhibiting opsonized blood cell phagocytosis was identified as a potential candidate for further studies. Confirmation of the disulfide bridge additionally provides clues for the non-thiol or non-disulfide bridge carrying ligands targeting ITP and other similar disorders.

Novel cytidine-based orotidine-5'-monophosphate decarboxylase inhibitors with an unusual twist.

Orotidine-5'-monophosphate decarboxylase (ODCase) is an interesting enzyme with an unusual catalytic activity and a potential drug target in Plasmodium falciparum, which causes malaria. ODCase has been shown to exhibit unusual and interesting interactions with a variety of nucleotide ligands. Cytidine-5'-monophosphate (CMP) is a poor ligand of ODCase, and CMP binds to the active site of ODCase with an unusual orientation and conformation. We designed N3- and N4-modified CMP derivatives as novel ligands to ODCase. These novel CMP derivatives and their corresponding nucleosides were evaluated against Plasmodium falciparum ODCase and parasitic cultures, respectively. These derivatives exhibited improved inhibition of the enzyme catalytic activity, displayed interesting binding conformations and unusual molecular rearrangements of the ligands. These findings with the modified CMP nucleotides underscored the potential of transformation of poor ligands to ODCase into novel inhibitors of this drug target.

Immunological targets in inflammation from the small molecule perspective.

Inflammation and autoimmune disorders have received much greater attention in the recent years due to the elucidation of various molecular mechanisms and the discoveries of various cytokines and other proteins involved in these processes. These discoveries are helping develop novel therapeutics including small molecules and protein therapeutics (biologics) for the treatment of sterile and nonsterile inflammatory disorders. Small molecule drugs have several advantages over protein therapeutics including their affordability for chronic treatments. In this review article, recent successes targeting various inflammatory cytokines and the corresponding receptors such as TLRs, interleukins, p38α as well as recent strategies for developing small molecule antagonists using rational models are discussed.