Novel S1P1 Receptor Agonists – Part 1: From Pyrazoles to Thiophenes

Rational Design, Synthesis, and Biological Evaluation of Novel S1PR2 Antagonists for Reversing 5-FU-Resistance in Colorectal Cancer

Resistance to 5-FU reduces its clinical efficacy for the treatment of colorectal cancer. Sphingosine-1-phosphate receptor 2 (S1PR2) has emerged as a potential target to reverse 5-FU-resistance by inhibiting the expression of dihydropyrimidine dehydrogenase (DPD). In this study, 38 novel S1PR2 antagonists based on aryl urea structure were designed and synthesized, and the structure-activity relationship was investigated based on the S1PR2 binding assay. Representative compound 43 potently interacts with S1PR2 with a K_D value of 0.73 nM. It displays potent 5-FU resensitizing activity in multiple 5-FU-resistant tumor cell lines, particularly in SW620/5-FU (EC₅₀ = 1.99 ± 0.03 μM) but shows no cytotoxicity in the normal colon cell line NCM460 up to 1000 μM. Moreover, 43 significantly enhances the antitumor efficacy of 5-FU in the SW620/5-FU animal model. These data suggest that 43 could be a novel lead compound for developing a 5-FU resensitizing agent.

One-pot synthesis of 3,5-diaryl substituted-1,2,4-oxadiazoles using gem-dibromomethylarenes

1,2,4-Oxadiazole is one of the most promising heterocyclic ring systems in medicinal chemistry. In the present paper, we report the method for an efficient one-pot synthesis of 3,5-diaryl substituted 1,2,4-oxadiazoles using a two-component reaction of gem-dibromomethylarenes with amidoximes in good yields. In this method, gem-dibromomethylarenes are used as benzoic acid equivalents for the efficient synthesis of aryl-substituted 1,2,4-oxadiazoles. It is anticipated that this methodology will have versatile applications in the practical syntheses of various molecules of both medicinal and material chemistry importance.

Synthesis and Antifungal Activity of Novel 3-Caren-5-One Oxime Esters

A series of novel 3-caren-5-one oxime esters were designed and synthesized by multi-step reactions in an attempt to develop potent antifungal agents. Two E-Z stereoisomers of the intermediate 3-caren-5-one oxime were separated by column chromatography for the first time. The structures of all the intermediates and target compounds were confirmed by UV-Vis, FTIR, NMR, ESI-MS, and elemental analysis. The antifungal activity of the target compounds was preliminarily evaluated by the in vitro method against Fusarium oxysporum f. sp. cucumerinum, Physalospora piricola, Alternaria solani, Cercospora arachidicola, Gibberella zeae,Rhizoeotnia solani, Bipolaris maydis, and Colleterichum orbicalare at 50 µg/mL. The target compounds exhibited best antifungal activity against P. piricola, in which compounds (Z)-4r (R = β-pyridyl), (Z)-4q (R = α-thienyl), (E)-4f′ (R = p-F Ph), (Z)-4i (R = m-Me Ph), (Z)-4j (R = p-Me Ph), and (Z)-4p (R = α-furyl) had inhibition rates of 97.1%, 87.4%, 87.4%, 85.0%, 81.9%, and 77.7%, respectively, showing better antifungal activity than that of the commercial fungicide chlorothanil. Also, compound (Z)-4r (R = β-pyridyl) displayed remarkable antifungal activity against all the tested fungi, with inhibition rates of 76.7%, 82.7%, 97.1%, 66.3%, 74.7%, 93.9%, 76.7% and 93.3%, respectively, showing better or comparable antifungal activity than that of the commercial fungicide chlorothanil. Besides, the E-Z isomers of the target oxime esters were found to show obvious differences in antifungal activity. These results provide an encouraging framework that could lead to the development of potent novel antifungal agents.

Modulators of Sphingosine-1-phosphate Pathway Biology: Recent Advances of Sphingosine-1-phosphate Receptor 1 (S1P1) Agonists and Future Perspectives

The sphingoid base derived class of lipids (sphingolipids) is a family of interconverting molecules that play key roles in numerous structural and signaling processes. The biosynthetic pathway of the sphingolipids affords many opportunities for therapeutic intervention: targeting the ligands directly, targeting the various proteins involved in the interconversion of the ligands, or targeting the receptors that respond to the ligands. The focus of this article is on the most advanced of the sphingosine-related therapeutics, agonists of sphingosine-1-phosphate receptor 1 (S1P₁). The diverse structural classes of S1P₁ agonists will be discussed and the status of compounds of clinical relevance will be detailed. An examination of how potential safety concerns are being navigated with compounds currently under clinical evaluation is followed by a discussion of the novel methods being explored to identify next-generation S1P₁ agonists with improved safety profiles. Finally, therapeutic opportunities for sphingosine-related targets outside of S1P₁ are touched upon.

S1P Signaling and De Novo Biosynthesis in Blood Pressure Homeostasis

Initially discovered as abundant components of eukaryotic cell membranes, sphingolipids are now recognized as important bioactive signaling molecules that modulate a variety of cellular functions, including those relevant to cancer and immunologic, inflammatory, and cardiovascular disorders. In this review, we discuss recent advances in our understanding of the role of sphingosine-1-phosphate (S1P) receptors in the regulation of vascular function, and focus on how de novo biosynthesized sphingolipids play a role in blood pressure homeostasis. The therapeutic potential of new drugs that target S1P signaling is also discussed.

Towards selective lysophospholipid GPCR modulators

G-protein-coupled receptors (GPCRs) that recognize the lysophospholipids (LPLs) are grouped into two phylogenetically distinct families: the endothelial differentiation gene (Edg) and non-Edg GPCRs. Owing to their more recent identification, and hindered by a lack of selective pharmacological tools, our understanding of the functions and signaling pathways of the non-Edg GPCRs is still in its infancy. Targeting the non-conserved allosteric binding sites of the LPL GPCRs shows particular promise for the development of selective modulators by structure-based drug design. However, only one Edg GPCR (S1PR1) structure has been determined to date, and it has low sequence identity with the non-Edg GPCRs (<20%). Thus, a representative structure of a non-Edg GPCR remains a pressing objective for selective structure-based drug design. Obtaining selective modulators targeting the non-Edg receptors would help to unravel the biology behind these novel GPCRs and potentially will support therapeutic treatment of diseases such as cancer, inflammation, and neuropsychiatric disorders.

Novel S1P(1) receptor agonists--part 3: from thiophenes to pyridines

In preceding communications we summarized our medicinal chemistry efforts leading to the identification of potent, selective, and orally active S1P1 agonists such as the thiophene derivative 1. As a continuation of these efforts, we replaced the thiophene in 1 by a 2-, 3-, or 4-pyridine and obtained less lipophilic, potent, and selective S1P1 agonists (e.g., 2) efficiently reducing blood lymphocyte count in the rat. Structural features influencing the compounds' receptor affinity profile and pharmacokinetics are discussed. In addition, the ability to penetrate brain tissue has been studied for several compounds. As a typical example for these pyridine based S1P1 agonists, compound 53 showed EC50 values of 0.6 and 352 nM for the S1P1 and S1P3 receptor, respectively, displayed favorable PK properties, and penetrated well into brain tissue. In the rat, compound 53 maximally reduced the blood lymphocyte count for at least 24 h after oral dosing of 3 mg/kg.