Optimization of sphingosine-1-phosphate-1 receptor agonists: effects of acidic, basic, and zwitterionic chemotypes on pharmacokinetic and pharmacodynamic profiles

Exploration of Tetrahydroisoquinoline- and Benzo[c]azepine-Based Sphingosine 1-Phosphate Receptor 1 Agonists for the Treatment of Multiple Sclerosis

Because of the wide use of Fingolimod for the treatment of multiple sclerosis (MS) and its cardiovascular side effects such as bradycardia, second-generation sphingosine 1-phosphate receptor 1 (S1P1) agonist drugs for MS have been developed and approved by FDA. The issue of bradycardia is still present with the new drugs, however, which necessitates further exploration of S1P1 agonists with improved safety profiles for next-generation MS drugs. Herein, we report a tetrahydroisoquinoline or a benzo[c]azepine core-based S1P1 agonists such as 32 and 60 after systematic examination of hydrophilic groups and cores. We investigated the binding modes of our representative compounds and their molecular interactions with S1P1 employing recent S1P1 cryo-EM structures. Also, favorable ADME properties of our compounds were shown. Furthermore, in vivo efficacy of our compounds was clearly demonstrated with PLC and EAE studies. Also, the preliminary in vitro cardiovascular safety of our compound was verified with human iPSC-derived cardiomyocytes.

Discovery of Novel Sphingosine-1-Phosphate-1 Receptor Agonists for the Treatment of Multiple Sclerosis

The sphingosine-1-phosphate-1 (S1P₁) receptor agonists have great potential for the treatment of multiple sclerosis (MS) because they can inhibit lymphocyte egress through receptor internalization. We designed and synthesized triazole and isoxazoline derivatives to discover a novel S1P₁ agonist for MS treatment. Of the two scaffolds, the isoxazoline derivative was determined to have excellent in vitro efficacy and drug-like properties. Among them, compound 21l was found to have superior drug-like properties as well as excellent in vitro efficacies (EC₅₀ = 7.03 nM in β-arrestin recruitment and EC₅₀ = 11.8 nM in internalization). We also confirmed that 21l effectively inhibited lymphocyte egress in the peripheral lymphocyte count test and significantly improved the clinical score in the experimental autoimmune encephalitis MS mouse model.

Approaches to the Synthesis of Dicarboxylic Derivatives of Bis(pyrazol-1-yl)alkanes

Carboxylation of bis(pyrazol-1-yl)alkanes by oxalyl chloride was studied. It was found that 4,4'-dicarboxylic derivatives of substrates with electron-donating methyl groups and short linkers (from one to three methylene groups) can be prepared using this method. Longer linkers lead to significantly lower product yields, which is probably due to instability of the intermediate acid chlorides that are initially formed in the reaction with oxalyl chloride. Thus, bis(pyrazol-1-yl)methane gave only monocarboxylic derivative even with a large excess of oxalyl chloride and prolonged reaction duration. An alternative approach involves the reaction of ethyl 4-pyrazolecarboxylates with dibromoalkanes in a superbasic medium (potassium hydroxide-dimethyl sulfoxide) and is suitable for the preparation of bis(4-carboxypyrazol-1-yl)alkanes with both short and long linkers independent of substitution in positions 3 and 5 of pyrazole rings. The obtained dicarboxylic acids are interesting as potential building blocks for metal-organic frameworks.

Therapeutic Strategies and Pharmacological Tools Influencing S1P Signaling and Metabolism

During the last two decades the study of the sphingolipid anabolic, catabolic, and signaling pathways has attracted enormous interest. Especially the introduction of fingolimod into market as first p.o. therapeutic for the treatment of multiple sclerosis has boosted this effect. Although the complex regulation of sphingosine-1-phosphate (S1P) and other catabolic and anabolic sphingosine-related compounds is not fully understood, the influence on different (patho)physiological states from inflammation to cytotoxicity as well as the availability of versatile pharmacological tools that represent new approaches to study these states are described. Here, we have summarized various aspects concerning the many faces of sphingolipid function modulation by different pharmacological tools up to clinical candidates. Due to the immense heterogeneity of physiological or pharmacological actions and complex cross regulations, it is difficult to predict their role in upcoming therapeutic approaches. Currently, inflammatory, immunological, and/or antitumor aspects are discussed.

Inhibitors of sphingosine-1-phosphate metabolism (sphingosine kinases and sphingosine-1-phosphate lyase)

Sphingolipids (SLs) are essential structural and signaling molecules of eukaryotic cells. Among them, sphingosine 1 phosphate (S1P) is a recognized promoter of cell survival, also involved, inter alia, in inflammation and tumorigenesis processes. The knowledge and modulation of the enzymes implicated in the biosynthesis and degradation of S1P are capital to control the intracellular levels of this lipid and, ultimately, to determine the cell fate. Starting with a general overview of the main metabolic pathways involved in SL metabolism, this review is mainly focused on the description of the most relevant findings concerning the development of modulators of S1P, namely inhibitors of the enzymes regulating S1P synthesis (sphingosine kinases) and degradation (sphingosine 1 phosphate phosphatase and lyase). In addition, a brief overview of the most significant agonists and antagonists at the S1P receptors is also addressed.