Optimization of a Potent, Orally Active S1P1 Agonist Containing a Quinolinone Core

A green and efficient synthetic methodology towards the synthesis of 1-allyl-6-chloro-4-oxo-1,4-dihydroquinoline-3-carboxamide derivatives

Quinolone is a privileged scaffold in medicinal chemistry and 4-Quinolone-3-Carboxamides have been reported to harbor vast therapeutic potential. However, conversion of N-1 substituted 4-Quinolone 3-Carboxylate to its corresponding carbamates is highly restrictive. This motivated us to adopt a much simpler, scalable and efficient methodology for the synthesis of highly pure N-1 substituted 4- Quinolone-3-Carboxamides with excellent yields. Our adopted methodology not only provides a robust pathway for the convenient synthesis of N-1 substituted 4- Quinolone-3-Carboxamides which can then be explored for their therapeutic potential, this may also be adaptable for the derivatization of other such less reactive carboxylate species.

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.

Electronic Relaxation Dynamics in 2-Quinolinones with Extended Conjugation

The 2-quinolinone family of molecules, also known as carbostyrils, have been proposed as light absorbing donor molecules in energy transfer based sensing schemes and as possible photocatalysts. Both of these applications make use of electronic excited states, but the photophysics of 2-quinolinones have not yet been examined closely. This study applies static and dynamic spectroscopy, with supporting density functional theory calculations, to reveal the electronic relaxation dynamics of a family of five 2-quinolinones with extended conjugated rings. These modifications lead to red-shifted absorbance and emission maxima, relative to unmodified 2-quinolinone. Optical excitation of these molecules with near UV light resulted in transitions with strong π → π* and HOMO → LUMO character. Time-correlated single photon counting measurements yielded fluorescence lifetimes ranging from 849.3 (±0.6) ps to 4.586 (±0.002) ns. Transient absorption spectroscopy revealed relaxation dynamics of the S₁ excited state formed by photoexcitation at 350 nm, along with formation of a long-lived signal assigned as excited state absorption by a triplet excited state. Vibrational relaxation in the S₁ state was also characterized in some compounds. Overlapping signals of S₁ decay and triplet growth in the transient absorption data set could not be fully disentangled. These results demonstrate a highly competitive relaxation scheme following multiple simultaneous pathways, a promising situation for establishing chemical control of electronic relaxation in the 2-quinolinone family.

An update on sphingosine-1-phosphate receptor 1 modulators

Sphingolipids represent an essential class of lipids found in all eukaryotes, and strongly influence cellular signal transduction. Autoimmune diseases like asthma and multiple sclerosis (MS) are mediated by the sphingosine-1-phosphate receptor 1 (S1P₁) to express a variety of symptoms and disease patterns. Inspired by its natural substrate, an array of artificial sphingolipid derivatives has been developed to target this specific G protein-coupled receptor (GPCR) in an attempt to suppress autoimmune disorders. FTY720, also known as fingolimod, is the first oral disease-modifying therapy for MS on the market. In pursuit of improved stability, bioavailability, and efficiency, structural analogues of this initial prodrug have emerged over time. This review covers a brief introduction to the sphingolipid metabolism, the mechanism of action on S1P₁, and an updated overview of synthetic sphingosine S1P₁ agonists.

Modulators of the Sphingosine 1-phosphate receptor 1

The Sphingosine 1-phosphate receptor (S1P-R) signaling system has proven to be of biological and medical importance in autoimmune settings. S1P1-R is a validated drug target for multiple sclerosis (MS) for which FTY720 (Fingolimod), a S1P1,3-5-R pan-agonist, was recently approved as the first orally active drug for the treatment of relapsing-remitting MS. Transient bradycardia and long half-life are the FTY720 critical pitfalls. This review provides the latest advances on next-generation S1P1-R modulators from 2012 up to date, with an overview of the chemical structures, structure-activity relationships, and relevant biological and clinical properties.

Predictability of Peripheral Lymphocyte Reduction of Novel S1P1 Agonists by In Vitro GPCR Signaling Profile

Surrogate readouts of G-protein–coupled receptor signaling pathways using highly engineered systems are often employed in the drug discovery process. However, accumulating data have demonstrated the importance of selecting relevant biological activity rather than technically facile assays to support high-throughout screening and subsequent structure-activity relationship studies. Here we report a case study using sphingosine-1-phosphate receptor 1 (S1P1) as the model system to compare compound activity in six different in vitro assays with their ability to predict in vivo efficacy. S1P1 has long been validated as a therapeutic target for autoimmune diseases. In this article, in vivo and in vitro studies on 19 S1P1 agonists are reported. In vitro activities of these S1P1 agonists, together with S1P and FTY720p, on Ca2+ mobilization, adenylyl cyclase inhibition, extracellular signal-related kinase (ERK) phosphorylation, β-arrestin recruitment, and receptor internalization, were determined. The in vitro potency of these compounds was correlated with their ability to induce peripheral lymphocyte reduction. The results revealed that inhibition of adenylyl cyclase and induction of β-arrestin recruitment and receptor internalization are good indicators to predict in vivo efficacy, whereas induction of Ca2+ mobilization through Gqi/5 coupling and ERK phosphorylation is irrelevant. This study demonstrated the importance of identifying an appropriate in vitro assay to predict in vivo activity based on the biological relevance in the drug discovery setting.

Discovery of BAF312 (Siponimod), a Potent and Selective S1P Receptor Modulator

A novel series of alkoxyimino derivatives as S1P1 agonists were discovered through de novo design using FTY720 as the chemical starting point. Extensive structure-activity relationship studies led to the discovery of (E)-1-(4-(1-(((4-cyclohexyl-3-(trifluoromethyl)benzyl)oxy)imino)ethyl)-2-ethylbenzyl)azetidine-3-carboxylic acid (32, BAF312, Siponimod), which has recently completed phase 2 clinical trials in patients with relapsing-remitting multiple sclerosis.

Integrating the puzzle pieces: the current atomistic picture of phospholipid-G protein coupled receptor interactions

A compelling question of how phospholipids interact with their target receptors has been of interest since the first receptor-mediated effects were reported. The recent report of a crystal structure for the S1P(1) receptor in complex with an antagonist phospholipid provides interesting perspective on the insights that had previously been gained through structure-activity studies of the phospholipids, as well as modeling and mutagenesis studies of the receptors. This review integrates these varied lines of investigation in the context of their various contributions to our current understanding of phospholipid-receptor interactions. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.