Discovery of APD334: Design of a Clinical Stage Functional Antagonist of the Sphingosine-1-phosphate-1 Receptor

Synthetic routes and clinical application of new drugs approved by EMA during 2023

In 2023, the European Medicines Agency (EMA) granted approval to 77 new molecular entities (NMEs), consisting of 45 new chemical entities (NCEs) and 32 new biological entities (NBEs). These pharmacological agents encompass a broad spectrum of therapeutic domains, including oncology, cardiology, dermatology, diagnostic medicine, endocrinology, gastroenterology and hepatology, metabolic disorders, and neurology. Among the 77 approved pharmaceuticals, three received accelerated review status, and 17 (22 %) were granted orphan drug designation for the treatment of rare diseases. This review provides an overview of the clinical applications and synthetic routes of 42 newly approved NCEs by the EMA in 2023. The objective is to offer a comprehensive understanding of the synthetic approaches used in the development of these drug molecules, thereby inspiring the creation of novel, efficient, and applicable synthetic methodologies.

Synthesis of Etrasimod (APD334): Al2O3-Promoted Decarboxylative Rearrangements of Cyclopentenones with Stereochemical Inversion

This study presents an efficient synthesis pathway for etrasimod, starting from (+)-cis-4-acetoxy-2-cyclopenten-1-ol, yielding 5.6% overall with 98% enantiomeric excess. The crucial intermediate, (4R)-anilinocyclopent-2-enone, was derived from the (S)-alcohol/isocyanate adduct through a concerted, Al2O3-promoted decarboxylative rearrangement, which inverted the configuration. A tetracyclic fused lactam was formed via a one-pot acylation-Michael addition, followed by keto α-arylation. Subsequent removal of the oxo group facilitated the synthesis of cyclopenta[b]indol-3-ylacetic acid through a series of reactions, including methanolysis, indoline oxidation, and hydrolysis.

The mechanism of action and chemical synthesis of FDA newly approved drug molecules

In 2023, the U.S. Food and Drug Administration has approved 29 small molecule drugs. These newly approved small molecule drugs possess the distinct scaffolds, thereby exhibiting diverse mechanisms of action and binding modalities. Moreover, the marketed drugs have always been an important source of new drug development and creative inspiration, thereby fostering analogous endeavors in drug discovery that potentially extend to the diverse clinical indications. Therefore, conducting a comprehensive evaluation of drug approval experience and associated information will facilitate the expedited identification of highly potent drug molecules. In this review, we comprehensively summarized the relevant information regarding the clinical applications, mechanisms of action and chemical synthesis of 29 small molecule drugs, with the aim of providing a promising structural basis and design inspiration for pharmaceutical chemists.

An Update on the Nitrogen Heterocycle Compositions and Properties of U.S. FDA-Approved Pharmaceuticals (2013-2023)

This Perspective is a continuation of our analysis of U.S. FDA-approved small-molecule drugs (1938-2012) containing nitrogen heterocycles. In this study we report drug structure and property analyses of 321 unique new small-molecule drugs approved from January 2013 to December 2023 as well as information about frequency of important heteroatoms such as sulfur and fluorine and key small nitrogen substituents (CN and NO2). The most notable change is an incredible increase in drugs containing at least one nitrogen heterocycle─82%, compared to 59% from preceding decades─as well as a significant increase in the number of nitrogen heterocycles per drug. Pyridine has claimed the #1 high-frequency nitrogen heterocycle occurrence spot from piperidine (#2), with pyrimidine (#5), pyrazole (#6), and morpholine (#9) being the big top 10 climbers. Also notable is high number of fused nitrogen heterocycles, apparently driven largely by newly approved cancer drugs.

Safety, Pharmacokinetics, and Pharmacodynamics of Etrasimod: Single and Multiple Ascending Dose Studies in Healthy Adults

Etrasimod is an investigational, once-daily, oral, selective sphingosine 1-phosphate receptor 1,4,5 modulator in development for immune-mediated inflammatory diseases (IMIDs). Here, we report the human safety, pharmacokinetics, and pharmacodynamics of etrasimod obtained from both a single ascending dose (SAD; 0.1-5 mg) study and a multiple ascending dose (MAD; 0.35-3 mg once daily) study. Overall, 99 healthy volunteers (SAD n = 40, MAD n = 59) completed the 2 studies. Evaluated single and multiple doses were well tolerated up to 3 mg without severe adverse events (AEs). Gastrointestinal disorders were the most common etrasimod-related AEs. Over the evaluated single- and multiple-dose ranges, dose-proportional and marginally greater-than-dose-proportional etrasimod plasma exposure were observed, respectively. At steady state, etrasimod oral clearance and half-life mean values ranged from 1.0 to 1.2 L/h and 29.7 to 36.4 hours, respectively. Dose-dependent total peripheral lymphocyte reductions occurred following etrasimod single and multiple dosing. Etrasimod multiple dosing resulted in reductions from baseline in total lymphocyte counts ranging from 41.1% to 68.8% after 21 days. Lymphocyte counts returned to normal range within 7 days following treatment discontinuation. Heart rate lowering from pretreatment baseline on etrasimod dosing was typically mild, with mean reductions seen after the first dose of up to 19.5 bpm (5 mg dose). The favorable safety, pharmacokinetic, and pharmacodynamic properties of etrasimod in humans supported its further development and warranted its investigation for treatment of IMIDs.

1-Phosphate receptor agonists: A promising therapeutic avenue for ischemia-reperfusion injury management

Ischemia-reperfusion injury (IRI) - a complex pathological condition occurring when blood supply is abruptly restored to ischemic tissues, leading to further tissue damage - poses a significant clinical challenge. Sphingosine-1-phosphate receptors (S1PRs), a specialized set of G-protein-coupled receptors comprising five subtypes (S1PR1 to S1PR5), are prominently present in various cell membranes, including those of lymphocytes, cardiac myocytes, and endothelial cells. Increasing evidence highlights the potential of targeting S1PRs for IRI therapeutic intervention. Notably, preconditioning and postconditioning strategies involving S1PR agonists like FTY720 have demonstrated efficacy in mitigating IRI. As the synthesis of a diverse array of S1PR agonists continues, with FTY720 being a prime example, the body of experimental evidence advocating for their role in IRI treatment is expanding. Despite this progress, comprehensive reviews delineating the therapeutic landscape of S1PR agonists in IRI remain limited. This review aspires to meticulously elucidate the protective roles and mechanisms of S1PR agonists in preventing and managing IRI affecting various organs, including the heart, kidney, liver, lungs, intestines, and brain, to foster novel pharmacological approaches in clinical settings.

Synthesis and clinical application of new drugs approved by FDA in 2023

In 2023, the U.S. Food and Drug Administration (FDA) granted approval to a total of 55 new drugs, comprising 29 new chemical entities (NCEs) and 25 new biological entities (NBEs). These drugs primarily focus on oncology, the central nervous system, anti-infection, hematology, cardiovascular, ophthalmology, immunomodulatory and other therapeutic areas. Out of the 55 drugs, 33 (60 %) underwent an accelerated review process and received approval, while 25 (45 %) were specifically approved for the treatment of rare diseases. The purpose of this review is to provide an overview of the clinical uses and production techniques of 29 newly FDA-approved NCEs in 2023. Our intention is to offer a comprehensive understanding of the synthetic approaches employed in the creation of these drug molecules, with the aim of inspiring the development of novel, efficient, and applicable synthetic methodologies.

Sphingosine 1-phosphate (S1P) receptor modulators as an induction and maintenance therapy for ulcerative colitis: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVE

One sphingosine-1-phosphate (S1P) receptor modulator is approved (ozanimod) and another (etrasimod) is under investigation for the induction and maintenance of remission of ulcerative colitis (UC). We aim to evaluate the efficacy and safety of S1P modulators in patients with active UC.

METHODS

We conducted a systematic review and meta-analysis synthesizing randomized controlled trials (RCTs), which were retrieved by systematically searching: PubMed, Web of Science, SCOPUS, and Cochrane through May 13th, 2023. We used the fixed-effect model to pool dichotomous data using risk ratio (RR) with a 95% confidence interval (CI).

RESULTS

Five RCTs with a total of 1990 patients were included. S1P receptor modulators were significantly associated with increased clinical response during both the induction (RR 1.71 with 95% CI [1.50, 1.94], P = 0.00001) and maintenance phases (RR 1.89 with 95% CI [1.33, 2.69], P = 0.0004); clinical remission rates during both induction (RR 2.76 with 95% CI [1.88, 4.05], P = 0.00001) and maintenance phases (RR 3.34 with 95% CI [1.41, 7.94], P = 0.006); endoscopic improvement during both induction (RR 2.15 with 95% CI [1.71, 2.70], P = 0.00001) and maintenance phases (RR 2.41 with 95% CI [1.15, 5.05], P = 0.02); and histologic remission during both induction (RR 2.60 with 95% CI [1.89, 3.57] [1.17, 2.10], P = 0.00001) and maintenance phases (RR 2.52 with 95% CI [1.89, 3.37], P = 0.00001). Finally, there was no difference regarding safety outcomes as compared to placebo in both the induction and maintenance phases.

CONCLUSION

S1P receptor modulators are effective in inducing and maintaining remission in patients with moderate to severe UC.

Etrasimod: First Approval

Etrasimod (VELSIPITY™) is an orally available, small-molecule selective sphingosine-1-phosphate (S1P) receptor modulator being developed by Pfizer for the treatment of ulcerative colitis and other immune-mediated inflammatory disorders. Etrasimod is selective for S1P receptor subtypes S1P1, S1P4 and S1P5 while having minimal activity on S1P3 and no activity on S1P2. Etrasimod received its first approval, in the USA, in October 2023 for the treatment of moderately to severely active ulcerative colitis in adults. Subsequently, the European Medicines Agency adopted a positive opinion in December 2023, recommending the granting of marketing authorisation for etrasimod for the treatment of patients aged ≥ 16 years with moderately to severely active ulcerative colitis who have had an inadequate response, lost response, or were intolerant to either conventional therapy, or a biological agent. Etrasimod is also under regulatory review for the treatment of ulcerative colitis in several other countries. Clinical development of etrasimod for use in the treatment of Crohn's disease, atopic dermatitis, eosinophilic oesophagitis and alopecia areata is ongoing worldwide. This article summarises the milestones in the development of etrasimod leading to this first approval for the treatment of ulcerative colitis in adults.

Design and synthesis of etrasimod derivatives as potent antibacterial agents against Gram-positive bacteria

The emergence of multidrug-resistant bacteria along with a declining pipeline of clinically useful antibiotics has led to the urgent need for the development of more effective antibacterial agents. Inspired by our recent report on the antibacterial activity of etrasimod, an immunomodulating drug candidate, we prepared a series of etrasimod derivatives by varying substituents on the phenyl ring, altering the central tricyclic aromatic ring, and modifying the carboxyl group. From this series of compounds, indole derivative 24f was identified as the most potent antibacterial compound, with the minimum inhibitory concentration (MIC) values between 2.5 and 10 μM against various Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), S. epidermidis and enterococci. Moreover, 24f exhibited rapid bactericidal activity against S. aureus, low toxicity and hemolytic activity, and a synergistic effect with gentamicin against S. aureus, MRSA, and Enterococcus faecalis. Furthermore, it was shown that neither etrasimod nor 24f affects S. aureus cell membranes. Importantly, 24f did not induce resistance in S. aureus, representing a significant improvement compared to etrasimod. Finally, the antibacterial activity of etrasimod and 24f against S. aureus and MRSA was confirmed in vivo in a Caenorhabditis elegans infection model. Taken together, our study highlights the value of etrasimod and its derivatives as potential antibacterial candidates for combating infections caused by Gram-positive bacteria.

Attention Mechanism-Based Graph Neural Network Model for Effective Activity Prediction of SARS-CoV-2 Main Protease Inhibitors: Application to Drug Repurposing as Potential COVID-19 Therapy

Compared to de novo drug discovery, drug repurposing provides a time-efficient way to treat coronavirus disease 19 (COVID-19) that is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). SARS-CoV-2 main protease (Mpro) has been proved to be an attractive drug target due to its pivotal involvement in viral replication and transcription. Here, we present a graph neural network-based deep-learning (DL) strategy to prioritize the existing drugs for their potential therapeutic effects against SARS-CoV-2 Mpro. Mpro inhibitors were represented as molecular graphs ready for graph attention network (GAT) and graph isomorphism network (GIN) modeling for predicting the inhibitory activities. The result shows that the GAT model outperforms the GIN and other competitive models and yields satisfactory predictions for unseen Mpro inhibitors, confirming its robustness and generalization. The attention mechanism of GAT enables to capture the dominant substructures and thus to realize the interpretability of the model. Finally, we applied the optimal GAT model in conjunction with molecular docking simulations to screen the Drug Repurposing Hub (DRH) database. As a result, 18 drug hits with best consensus prediction scores and binding affinity values were identified as the potential therapeutics against COVID-19. Both the extensive literature searching and evaluations on adsorption, distribution, metabolism, excretion, and toxicity (ADMET) illustrate the premium drug-likeness and pharmacokinetic properties of the drug candidates. Overall, our work not only provides an effective GAT-based DL prediction tool for inhibitory activity of SARS-CoV-2 Mpro inhibitors but also provides theoretical guidelines for drug discovery in the COVID-19 treatment.

Immune System and Brain/Intestinal Barrier Functions in Psychiatric Diseases: Is Sphingosine-1-Phosphate at the Helm?

Over the past few decades, extensive research has shed light on immune alterations and the significance of dysfunctional biological barriers in psychiatric disorders. The leaky gut phenomenon, intimately linked to the integrity of both brain and intestinal barriers, may play a crucial role in the origin of peripheral and central inflammation in these pathologies. Sphingosine-1-phosphate (S1P) is a bioactive lipid that regulates both the immune response and the permeability of biological barriers. Notably, S1P-based drugs, such as fingolimod and ozanimod, have received approval for treating multiple sclerosis, an autoimmune disease of the central nervous system (CNS), and ulcerative colitis, an inflammatory condition of the colon, respectively. Although the precise mechanisms of action are still under investigation, the effectiveness of S1P-based drugs in treating these pathologies sparks a debate on extending their use in psychiatry. This comprehensive review aims to delve into the molecular mechanisms through which S1P modulates the immune system and brain/intestinal barrier functions. Furthermore, it will specifically focus on psychiatric diseases, with the primary objective of uncovering the potential of innovative therapies based on S1P signaling.

Etrasimod for the treatment of ulcerative colitis

Sphingosine-1-phosphate (S1P) and its receptor (S1PR) are involved in the pathogenesis of multiple immune-mediated inflammatory disorders, including inflammatory bowel disease. The use of S1PR modulators represents a new therapeutic option for ulcerative colitis patients. Etrasimod is an oral selective S1PR1, S1PR4 and S1PR5 modulator that inhibits the trafficking of lymphocytes from the lymph nodes into the blood. Recently, etrasimod has demonstrated efficacy in the phase II OASIS study and its open-label extension for the treatment of ulcerative colitis patients. This article reviews the mechanism of action of etrasimod and summarizes the available clinical efficacy and safety data regarding etrasimod, which is a promising drug in the treatment of patients with moderate to severe ulcerative colitis.

S1PR1 modulators in multiple sclerosis: Efficacy, safety, comparison, and chemical structure insights

Multiple sclerosis (MS) is a neurological disease that leads to severe physical and cognitive disabilities. Drugs used in the treatment of MS vary from small synthetic molecules to large macromolecules such as antibodies. Sphingosine 1-phosphate receptor modulators are frequently used for the treatment of MS. These medicines prevent the egress of lymphocytes from secondary lymphoid organs leading to immune system suppression. Currently, four S1PR modulators are on the market and several potential drug candidates are in clinical trials for the treatment of MS. These compounds differ in chemical structure, adverse effects, and efficacy points of view. The current article reviews the latest studies on S1PR1 modulators and compares them with other MS drugs in terms of efficacy, tolerability, and safety. A special focus was dedicated to discussing the structure-activity relationships of these compounds and performing a three-dimensional quantitative structure-activity relationship (3D-QSAR) analysis to gain better insight into the ligand-receptor interaction mode.

Unveiling the biological role of sphingosine-1-phosphate receptor modulators in inflammatory bowel diseases

Inflammatory bowel disease (IBD) is chronic inflammation of the gastrointestinal tract that has a high epidemiological prevalence worldwide. The increasing disease burden worldwide, lack of response to current biologic therapeutics, and treatment-related immunogenicity have led to major concerns regarding the clinical management of IBD patients and treatment efficacy. Understanding disease pathogenesis and disease-related molecular mechanisms is the most important goal in developing new and effective therapeutics. Sphingosine-1-phosphate (S1P) receptor (S1PR) modulators form a class of oral small molecule drugs currently in clinical development for IBD have shown promising effects on disease improvement. S1P is a sphingosine-derived phospholipid that acts by binding to its receptor S1PR and is involved in the regulation of several biological processes including cell survival, differentiation, migration, proliferation, immune response, and lymphocyte trafficking. T lymphocytes play an important role in regulating inflammatory responses. In inflamed IBD tissue, an imbalance between T helper (Th) and regulatory T lymphocytes and Th cytokine levels was found. The S1P/S1PR signaling axis and metabolism have been linked to inflammatory responses in IBD. S1P modulators targeting S1PRs and S1P metabolism have been developed and shown to regulate inflammatory responses by affecting lymphocyte trafficking, lymphocyte number, lymphocyte activity, cytokine production, and contributing to gut barrier function.

Incorporation of a cyclobutyl substituent in molecules by transition metal-catalyzed cross-coupling reactions

In this review, the incorporation of a cyclobutyl substituent in molecules, by transition metal-catalyzed cross-coupling, is described by only considering the formation of C-C bonds. Three main strategies are used to introduce a cyclobutyl substituent in molecules by involving either electrophilic or nucleophilic cyclobutane derivatives.

Repurposing the Sphingosine-1-Phosphate Receptor Modulator Etrasimod as an Antibacterial Agent Against Gram-Positive Bacteria

New classes of antibiotics are urgently needed in the fight against multidrug-resistant bacteria. Drug repurposing has emerged as an alternative approach to accelerate antimicrobial research and development. In this study, we screened a library of sphingosine-1-phosphate receptor (S1PR) modulators against Staphylococcus aureus and identified five active compounds. Among them, etrasimod (APD334), an investigational drug for the treatment of ulcerative colitis, displayed the best inhibitory activity against S. aureus when growing as free-floating planktonic cells and within biofilms. In follow-up studies, etrasimod showed bactericidal activity and drastic reduction of viable bacteria within 1 h of exposure. It also displayed a potent activity against other Gram-positive bacteria, including penicillin- and methicillin-resistant S. aureus strains, S. epidermidis, and Enterococcus faecalis, with a minimum inhibitory concentration (MIC) ranging from 5 to 10 μM (2.3–4.6 μg/mL). However, no inhibition of viability was observed against Gram-negative bacteria Acinetobacter baumannii, Escherichia coli, and Pseudomonas aeruginosa, showing that etrasimod preferably acts against Gram-positive bacteria. On the other hand, etrasimod was shown to inhibit quorum sensing (QS) signaling in Chromobacterium violaceum, suggesting that it may block the biofilm formation by targeting QS in certain Gram-negative bacteria. Furthermore, etrasimod displayed a synergistic effect with gentamicin against S. aureus, thus showing potential to be used in antibiotic combination therapy. Finally, no in vitro toxicity toward mammalian cells was observed. In conclusion, our study reports for the first time the potential of etrasimod as a repurposed antibacterial compound against Gram-positive bacteria.

Review article: the sphingosine 1 phosphate/sphingosine 1 phosphate receptor axis - a unique therapeutic target in inflammatory bowel disease

BACKGROUND

Ozanimod, a high selective sphingosine 1 phosphate (S1P) receptor (S1PR) 1/5 modulator was approved by the Food and Drug Administration for the treatment of adult patients with moderately to severely active ulcerative colitis. Additional S1PR modulators are being tested in clinical development programmes for both ulcerative colitis and Crohn's disease.

AIM

To provide an overview of advances in understanding S1PRs biology and summarise preclinical and clinical investigations of S1P receptor modulators in chronic inflammatory disease with special emphasis on inflammatory bowel diseases (IBD).

METHODS

We performed a narrative review using PubMed and ClinicalTrials.gov.

RESULTS

Through S1PRs, S1P regulates multiple cellular processes, including proliferation, migration, survival, and vascular barrier integrity. The S1PRs function of regulating lymphocyte trafficking is well known, but new functions of S1PRs expand our knowledge of S1PRs biology. Several S1PR modulators are in clinical development for both ulcerative colitis and Crohn's disease and have shown promise in phase II and III studies with ozanimod now being approved for ulcerative colitis.

CONCLUSIONS

S1P receptor modulators constitute a novel, promising, safe, and convenient strategy for the treatment of IBD.

Emerging therapeutic options in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic disease that requires chronic treatment throughout the evolution of the disease, with a complex physiopathology that entails great challenges for the development of new and specific treatments for ulcerative colitis and Crohn´s disease. The anti-tumor necrosis factor alpha therapy has impacted the clinical course of IBD in those patients who do not respond to conventional treatment, so there is a need to develop new therapies and markers of treatment response. Various pathways involved in the development of the disease are known and the new therapies have focused on blocking the inflammatory process at the gastrointestinal level by oral, intravenous, subcutaneous, and topical route. All these new therapies can lead to more personalized treatments with higher success rates and fewer relapses. These treatments have not only focused on clinical remission, but also on achieving macroscopic changes at the endoscopic level and microscopic changes by achieving mucosal healing. These treatments are mainly based on modifying signaling pathways, by blocking receptors or ligands, reducing cell migration and maintaining the integrity of the epithelial barrier. Therefore, this review presents the efficacy and safety of the new treatments that are currently under study and the advances that have been made in this area in recent years.

Synthesis and Biological Activities of Pyrazino[1,2-a]indole and Pyrazino[1,2-a]indol-1-one Derivatives

This review concerns the synthesis and biological activities of pyrazino[1,2-a]indoles and pyrazino[1,2-a]indol-1-ones reported since 1997 and the discovery of biological activity of pyrazinoindole derivatives. In the first part, we first presented the synthetic routes that have been reported from a methodological point of view to access the pyrazinoindole unit according to cyclization reactions using or not using metal catalysts. Then, syntheses and neuropsychiatric, auto-immune, anti-infectious and anti-cancer properties of pyrazinoindoles were detailed. In the second part, we first reported the main accesses to pyrazinoindol-1-one substrates according to Michael reactions, metal-catalyzed and metal-free cyclization reactions. The syntheses and anti-cancer, anti-infectious, anti-allergenic and neuropsychiatric properties of pyrazinoindolones were next described and discussed.

Targeting Sphingosine-1-Phosphate Signaling in Immune-Mediated Diseases: Beyond Multiple Sclerosis

Sphingosine-1-phosphate (S1P) is a bioactive lipid metabolite that exerts its actions by engaging 5 G-protein-coupled receptors (S1PR1-S1PR5). S1P receptors are involved in several cellular and physiological events, including lymphocyte/hematopoietic cell trafficking. An S1P gradient (low in tissues, high in blood), maintained by synthetic and degradative enzymes, regulates lymphocyte trafficking. Because lymphocytes live long (which is critical for adaptive immunity) and recirculate thousands of times, the S1P-S1PR pathway is involved in the pathogenesis of immune-mediated diseases. The S1PR1 modulators lead to receptor internalization, subsequent ubiquitination, and proteasome degradation, which renders lymphocytes incapable of following the S1P gradient and prevents their access to inflammation sites. These drugs might also block lymphocyte egress from lymph nodes by inhibiting transendothelial migration. Targeting S1PRs as a therapeutic strategy was first employed for multiple sclerosis (MS), and four S1P modulators (fingolimod, siponimod, ozanimod, and ponesimod) are currently approved for its treatment. New S1PR modulators are under clinical development for MS, and their uses are being evaluated to treat other immune-mediated diseases, including inflammatory bowel disease (IBD), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and psoriasis. A clinical trial in patients with COVID-19 treated with ozanimod is ongoing. Ozanimod and etrasimod have shown promising results in IBD; while in phase 2 clinical trials, ponesimod has shown improvement in 77% of the patients with psoriasis. Cenerimod and amiselimod have been tested in SLE patients. Fingolimod, etrasimod, and IMMH001 have shown efficacy in RA preclinical studies. Concerns relating to S1PR modulators are leukopenia, anemia, transaminase elevation, macular edema, teratogenicity, pulmonary disorders, infections, and cardiovascular events. Furthermore, S1PR modulators exhibit different pharmacokinetics; a well-established first-dose event associated with S1PR modulators can be mitigated by gradual up-titration. In conclusion, S1P modulators represent a novel and promising therapeutic strategy for immune-mediated diseases.

The ceramide-S1P pathway as a druggable target to alleviate peripheral neuropathic pain

Introduction: Neuropathic pain disorders are diverse, and the currently available therapies are ineffective in the majority of cases. Therefore, there is a major need for gaining novel mechanistic insights and developing new treatment strategies for neuropathic pain. Areas covered: We performed an in-depth literature search on the molecular mechanisms and systemic importance of the ceramide-to-S1P rheostat regulating neuron function and neuroimmune interactions in the development of neuropathic pain. Expert opinion: The S1P receptor modulator FTY720 (fingolimod, Gilenya®), LPA receptor antagonists and several mechanistically related compounds in clinical development raise great expectations for treating neuropathic pain disorders. Research on S1P receptors, S1P receptor modulators or SPHK inhibitors with distinct selectivity, pharmacokinetics and safety must provide more mechanistic insight into whether they may qualify as useful treatment options for neuropathic pain disorders. The functional relevance of genetic variations within the ceramide-to-S1P rheostat should be explored for an enhanced understanding of neuropathic pain pathogenesis. The ceramide-to-S1P rheostat is emerging as a critically important regulator hub of neuroimmune interactions along the pain pathway, and improved mechanistic insight is required to develop more precise and effective drug treatment options for patients suffering from neuropathic pain disorders.

Small-Molecule Antagonist Targeting Exportin-1 via Rational Structure-Based Discovery

Exportin-1 (also named as CRM1) plays a prominent role in autoimmune disorders and has emerged as a potential therapeutic target for colitis. Here we report on the rational structure-based discovery of a small-molecule antagonist of exportin-1, LFS-829, with low-range nanomolar activities. The co-crystallographic structure, surface plasmon resonance binding assay, and cell-based phenotypic nuclear export functional assay validated that exportin-1 is a key target of LFS-829. Moreover, we demonstrated that the C528S mutation or the knockdown on exportin-1 can abolish the cellular activities of LFS-829. Strikingly, oral administration of LFS-829 can significantly reverse the pathological features of colitis model mice. We revealed that LFS-829 can attenuate dual NF-κB signaling and the Nrf2 cytoprotection pathway via targeting exportin-1 in colitis mice. Moreover, LFS-829 has a very low risk of cardiotoxicity and acute toxicity. Therefore, LFS-829 holds great promise for the treatment of colitis and may warrant translation for use in clinical trials.

Efficacy and Safety of Etrasimod in a Phase 2 Randomized Trial of Patients With Ulcerative Colitis

BACKGROUND & AIMS

Etrasimod (APD334) is an oral, selective sphingosine 1-phosphate receptor modulator in development for immune-mediated inflammatory disorders. We assessed the efficacy and safety of etrasimod in patients with moderately to severely active ulcerative colitis (UC).

METHODS

In a phase 2, proof-of-concept, double-blind, parallel-group study, adult outpatients with modified Mayo Clinic scores (MCSs) (stool frequency, rectal bleeding, and endoscopy findings) of 4-9, endoscopic subscores of 2 or more, and rectal bleeding subscores of 1 or more were randomly assigned to groups given once-daily etrasimod 1 mg (n = 52), etrasimod 2 mg (n = 50), or placebo (n = 54) for 12 weeks. The study was performed from October 15, 2015, through February 14, 2018, at 87 centers in 17 countries. The primary endpoint was an increase in the mean improvement in modified MCS from baseline to week 12. Secondary endpoints included the proportion of patients with endoscopic improvement (subscores of 1 or less) from baseline to week 12. Exploratory endpoints, including clinical remission, are reported in the article, although the study was statistically powered to draw conclusions only on the primary endpoint.

RESULTS

At week 12, the etrasimod 2 mg group met the primary and all secondary endpoints. Etrasimod 2 mg led to a significantly greater increase in mean improvement in modified MCS from baseline than placebo (difference from placebo, 0.99 points; 90% confidence interval, 0.30-1.68; P = .009), and etrasimod 1 mg led to an increase in mean improvement from baseline in modified MCS of 0.43 points more than placebo (90% confidence interval, reduction of 0.24 to increase of 1.11; nominal P = .15). Endoscopic improvement occurred in 41.8% of patients receiving etrasimod 2 mg vs 17.8% receiving placebo (P = .003). Most adverse events were mild to moderate. Three patients had a transient, asymptomatic, low-grade atrioventricular block that resolved spontaneously all patients had evidence of atrioventricular block before etrasimod exposure.

CONCLUSIONS

In patients with moderately to severely active ulcerative colitis, etrasimod 2 mg was more effective than placebo in producing clinical and endoscopic improvements. Further clinical development is warranted. Clinicaltrials.gov, Number: NCT02447302.

Amiselimod (MT-1303), a novel sphingosine 1-phosphate receptor-1 functional antagonist, inhibits progress of chronic colitis induced by transfer of CD4+CD45RBhigh T cells

Amiselimod (MT-1303) is a novel sphingosine 1-phosphate receptor-1 (S1P₁ receptor) modulator with a more favorable cardiac safety profile than other S1P₁ receptor modulators. MT-1303 phosphate (MT-1303-P), an active metabolite of MT-1303, exhibits S1P₁ receptor agonism at a lower EC₅₀ value than other S1P₁ receptor modulators currently being developed. We aimed to evaluate the efficacy of MT-1303 and its mode of action in chronic colitis using an inflammatory bowel disease (IBD) model. Oral administration of MT-1303 (0.3 mg/kg) once daily for 3 days to mice almost completely abolished S1P₁ receptor expression on CD4⁺ T cells from mesenteric lymph nodes, which corresponded to a marked decrease in CD4⁺ T cell count in peripheral blood, indicating that MT-1303-P acts as a functional antagonist of the S1P₁ receptor. The potential benefit of MT-1303 for IBD was assessed using immunodeficient SCID mice with chronic colitis induced by adoptive transfer of CD4⁺CD45RB^high T cells from BALB/c mice. An oral dose of 0.1 and 0.3 mg/kg MT-1303 administered daily one week after the cell transfer inhibited the development of chronic colitis with an efficacy comparable to that of an anti-mTNF-α mAb (250 μg/mouse). In addition, MT-1303 administration significantly reduced the number of infiltrating Th1 and Th17 cells into the lamina propria of the colon in colitis mice. Our results suggest that MT-1303 acts as a functional antagonist of the S1P₁ receptor on lymphocytes, regulates lymphocyte trafficking, and inhibits infiltration of colitogenic Th1 and Th17 cells into the colon to inhibit the development of chronic colitis.

A Functionally Defined In Vivo Astrocyte Population Identified by c-Fos Activation in a Mouse Model of Multiple Sclerosis Modulated by S1P Signaling: Immediate-Early Astrocytes (ieAstrocytes)

Astrocytes have prominent roles in central nervous system (CNS) function and disease, with subpopulations defined primarily by morphologies and molecular markers often determined in cell culture. Here, we identify an in vivo astrocyte subpopulation termed immediate-early astrocytes (ieAstrocytes) that is defined by functional c-Fos activation during CNS disease development. An unbiased screen for CNS cells showing c-Fos activation during experimental autoimmune encephalomyelitis (EAE), a mouse model for multiple sclerosis (MS), was developed by using inducible, TetTag c-Fos reporter mice that label activated cells with a temporally stable, nuclear green fluorescent protein (GFP). Four-dimensional (3D over time) c-Fos activation maps in the spinal cord were produced by combining tissue clearing (iDISCO) and confocal microscopy that identified onset and expansion of GFP+ cell populations during EAE. More than 95% of the GFP+ cells showed glial fibrillary acidic protein (GFAP) immunoreactivity-in contrast to absent or rare labeling of neurons, microglia, and infiltrating immune cells-which constituted ieAstrocytes that linearly increased in number with progression of EAE. ieAstrocyte formation was reduced by either astrocyte-specific genetic removal of sphingosine 1-phosphate receptor 1 (S1P1) or pharmacological inhibition by fingolimod (FTY720), an FDA-approved MS medicine that can functionally antagonize S1P1. ieAstrocytes thus represent a functionally defined subset of disease-linked astrocytes that are the first and predominant CNS cell population activated during EAE, and that track with disease severity in vivo. Their reduction by a disease-modifying agent supports their therapeutic relevance to MS and potentially other neuroinflammatory and neurodegenerative diseases.

Frontiers in Drug Research and Development for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is idiopathic, lifelong, immune-mediated diseases, for which curative therapies are not yet available. In the last 15 years, the introduction of monoclonal antibodies targeting tumor necrosis factor-α, a cytokine playing a key role in bowel inflammation, has revolutionized treatment paradigms for IBD. Despite their proven long-term efficacy, however, many patients do not respond or progressively lose response to these drugs. Major advances of knowledge in immunology and pathophysiology of intestinal inflammatory processes have made possible the identification of new molecular targets for drugs, thus opening several new potential therapeutic opportunities for IBD. The abnormal response of intestinal immunity to unknown antigens leads to the activation of T helper lymphocytes and triggers the inflammatory cascade. Sphingosine 1-phosphate receptor agonists negatively modulate the egress of lymphocytes, inducted by antigen-presenting cells, from secondary lymphoid tissues to intestinal wall. Leukocyte adhesion inhibitors (both anti-integrin and anti-Mucosal Vascular Addressin Cell Adhesion Molecule 1) interfere with the tissue homing processes. Activated T helper lymphocytes increase the levels of pro-inflammatory cytokines, such as interleukin 12, 23, and 6, offering several potential pharmacological interventions. The Janus kinases, intracellular enzymes mediating the transduction of several cytokine signals, are other explored targets for treating immune-mediated diseases. Finally, the impact of modulating Smad7 pathway, which is responsible for the down-regulation of the immunosuppressive cytokine transforming growth factor-β signaling, is currently under investigation. The purpose of this review is to discuss the most promising molecules in late-stage clinical development, with a special emphasis on pharmacological properties.

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.

Identification and Preclinical Pharmacology of BMS-986104: A Differentiated S1P1 Receptor Modulator in Clinical Trials

Clinical validation of S1P receptor modulation therapy was achieved with the approval of fingolimod (Gilenya, 1) as the first oral therapy for relapsing remitting multiple sclerosis. However, 1 causes a dose-dependent reduction in the heart rate (bradycardia), which occurs within hours after first dose. We disclose the identification of clinical compound BMS-986104 (3d), a novel S1P1 receptor modulator, which demonstrates ligand-biased signaling and differentiates from 1 in terms of cardiovascular and pulmonary safety based on preclinical pharmacology while showing equivalent efficacy in a T-cell transfer colitis model.