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

The efficacy of the recently approved drug fingolimod (FTY720) in multiple sclerosis patients results from the action of its phosphate metabolite on sphingosine-1-phosphate S1P1 receptors, while a variety of side effects have been ascribed to its S1P3 receptor activity. Although S1P and phospho-fingolimod share the same structural elements of a zwitterionic headgroup and lipophilic tail, a variety of chemotypes have been found to show S1P1 receptor agonism. Here we describe a study of the tolerance of the S1P1 and S1P3 receptors toward bicyclic heterocycles of systematically varied shape and connectivity incorporating acidic, basic, or zwitterionic headgroups. We compare their physicochemical properties, their performance in in vitro and in vivo pharmacokinetic models, and their efficacy in peripheral lymphocyte lowering. The campaign resulted in the identification of several potent S1P1 receptor agonists with good selectivity vs S1P3 receptors, efficacy at <1 mg/kg oral doses, and developability properties suitable for progression into preclinical development.

Oral ponesimod in patients with chronic plaque psoriasis: a randomised, double-blind, placebo-controlled phase 2 trial

BACKGROUND

We assessed the efficacy, safety, and tolerability of ponesimod, an oral, selective, reversible modulator of sphingosine 1-phosphate receptor 1, in patients with moderate to severe chronic plaque psoriasis.

METHODS

Between Sept 22, 2010, and Oct 24, 2012, patients with psoriasis area and severity index (PASI) scores higher than 10 were enrolled into this multicentre double-blind, phase 2 study. They received 20 mg or 40 mg ponesimod or placebo once daily for 16 weeks. Those with at least 50% reduction in PASI score at 16 weeks and who were receiving ponesimod were rerandomised to receive maintenance ponesimod therapy or placebo until week 28. The primary endpoint was reduction in PASI score from baseline of at least 75% (PASI75) at week 16. This study is registered with ClinicalTrials.gov, number NCT01208090.

FINDINGS

Of 326 patients initially randomised (20 mg ponesimod n=126, 40 mg ponesimod n=133, and placebo n=67) PASI75 was achieved at week 16 in 58 (46·0%), 64 (48·1%), and nine (13·4%), respectively. The treatment effect was significant for the two ponesimod doses (both p<0·0001). Of 219 patients who entered the maintenance period, PASI75 was achieved by week 28 in 35 (71·4%) of 49 who continued on 20 mg ponesimod and 41 (77·4%) of 53 on 40 mg ponesimod, and in 19 (42·2%) of 45 who swapped from 20 mg to placebo and 19 (40·4%) of 47 from 40 mg to placebo. Ponesimod was associated with dyspnoea, raised liver enzyme concentrations, and dizziness.

INTERPRETATION

Significant clinical benefit was seen at week 16 that increased with maintenance therapy.

FUNDING

Actelion Pharmaceuticals.

Oral ponesimod in relapsing-remitting multiple sclerosis: a randomised phase II trial

OBJECTIVE

This double-blind, placebo-controlled, dose-finding phase IIb study evaluated the efficacy and safety of ponesimod, an oral selective S1P1 receptor modulator, for the treatment of patients with relapsing-remitting multiple sclerosis (RRMS).

METHODS

464 patients were randomised to receive once-daily oral ponesimod 10, 20 or 40 mg, or placebo for 24 weeks. The primary endpoint was the cumulative number of new T1 gadolinium-enhanced (T1 Gd+) lesions per patient recorded every 4 weeks from weeks 12 to 24 after study drug initiation. Secondary endpoints were the annualised confirmed relapse rate (ARR) and time to first confirmed relapse. Safety and tolerability were also evaluated.

RESULTS

The mean cumulative number of new T1 Gd+ lesions at weeks 12-24 was significantly lower in the ponesimod 10 mg (3.5; rate ratio (RR) 0.57; p=0.0318), 20 mg (1.1; RR 0.17; p<0.0001) and 40 mg (1.4; RR 0.23; p<0.0001) groups compared with placebo (6.2). The mean ARR was lower with 40 mg ponesimod versus placebo, with a maximum reduction of 52% (0.25 vs 0.53; p=0.0363). The time to first confirmed relapse was increased with ponesimod compared with placebo. The proportion of patients with ≥ 1 treatment-emergent adverse events (AEs) was similar across ponesimod groups and the placebo group. Frequently reported AEs with higher incidence in the three ponesimod groups compared with placebo were anxiety, dizziness, dyspnoea, increased alanine aminotransferase, influenza, insomnia and peripheral oedema.

CONCLUSIONS

Once-daily treatment with ponesimod 10, 20 or 40 mg significantly reduced the number of new T1 Gd+ lesions and showed a beneficial effect on clinical endpoints. Ponesimod was generally well tolerated, and further investigation of ponesimod for the treatment of RRMS is under consideration.

TRIAL REGISTRATION NUMBER

NCT01006265.

Mass balance, pharmacokinetics and metabolism of the selective S1P1 receptor modulator ponesimod in humans

1. Ponesimod [(R)-5-[3-chloro-4-(-2,3-dihydroxy-propoxy)-benzylidene]-2-propylimino-3-o-tolyl-thiazolidin-4-one] is an orally administered, selective S1P1 receptor modulator that blocks the egress of lymphocytes from lymphoid organs and reduces the availability of circulating effector T/B-cells. 2. The mass balance, pharmacokinetics and metabolism of 40 mg (14)C-ponesimod were investigated in six healthy male subjects. The total radioactivity in whole blood, plasma, urine, faeces and expired CO2 was determined by liquid scintillation counting. Metabolite profiling was performed by high-performance liquid chromatography and detection by mass spectrometry. 3. The majority of the radioactivity (% of administered dose) was recovered in faeces (57.3-79.6%), followed by urine (10.3-18.4%) and a small proportion in CO2 from expired air (0.6-1.9%). The average cumulative recovery (mass balance) of (14)C-associated radioactivity in faeces and urine was 77.9% of the administered dose. Unchanged ponesimod made up 25.9% of total radioactivity in faeces; none was detected in urine. Ponesimod was extensively metabolised and two pharmacologically inactive metabolites, M12 (ACT-204426) and M13 (ACT-338375), were detected in the circulation. M12 corresponded to 8.1% and M13 to 25.7% of the total drug-related radioactive exposure (AUC0-∞) in plasma. M12 was highly abundant in faeces (22.3% of total radioactivity) and to a smaller extent in urine (2.5% of total radioactivity).

Pharmacokinetics and pharmacodynamics of ponesimod, a selective S1P1 receptor modulator, in the first-in-human study

AIMS

This study investigated the tolerability, safety, pharmacokinetics and pharmacodynamics of ponesimod, a novel oral selective sphingosine-1-phosphate (S1P1) receptor modulator in development for the treatment of auto-immune diseases.

METHODS

This was a double-blind, placebo-controlled, ascending, single-dose study. Healthy male subjects received doses of 1-75 mg or placebo control.

RESULTS

Ponesimod was well tolerated. Starting with a dose of 8 mg, transient asymptomatic reductions in heart rate were observed. Ponesimod pharmacokinetics were dose proportional. The median time to maximal concentration ranged from 2.0 to 4.0 h, and ponesimod was eliminated with a mean half-life varying between 21.7 and 33.4 h. Food had a minimal effect on ponesimod pharmacokinetics. Doses of ≥8 mg reduced total lymphocyte count in a dose-dependent manner. Lymphocyte counts returned to normal ranges within 96 h. A pharmacokinetic/pharmacodynamic model was developed that adequately described the observed effects of ponesimod on total lymphocyte counts.

CONCLUSIONS

Single doses of ponesimod up to and including 75 mg were well tolerated. The results of this ascending single-dose study indicate an immunomodulator potential for ponesimod and a pharmacokinetic/pharmacodynamic profile consistent with once-a-day dosing.

Population pharmacokinetics and pharmacodynamics of ponesimod, a selective S1P1 receptor modulator

Ponesimod (ACT-128800), a reversible, orally active, selective S1P1 receptor modulator, prevents the egress of lymphocytes from the lymph node into the systemic circulation. It is currently in clinical development for the treatment of relapsing multiple sclerosis. Modulation of circulating lymphocytes serves as biomarker of efficacy and safety, such that the quantitative characterization of the pharmacokinetic/pharmacodynamic (PK/PD) relationship guides the clinical development of the compound. The availability of a variety of doses, dosing regimens, and treatment durations permitted estimation of the pharmacokinetics characterized by an absorption lag time followed by a sequential zero/first-order absorption and two compartments with first-order elimination. The PD are modeled as an indirect-effect model with rates of appearance and disappearance of lymphocytes in blood with a circadian rhythm and a drug effect on the rate of appearance. The model suggests a circadian variation of 9% and a maximum inhibition of 86% of total lymphocyte count with high doses at steady state. It was instrumental for the selection of doses for subsequent studies that confirmed the effect plateau in total lymphocyte count at approximately 0.5 × 10(9) counts/L.

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.

Chemical and genetic tools to explore S1P biology

The zwitterionic lysophospholipid Sphingosine 1-Phosphate (S1P) is a pleiotropic mediator of physiology and pathology. The synthesis, transport, and degradation of S1P are tightly regulated to ensure that S1P is present in the proper concentrations in the proper location. The binding of S1P to five G protein-coupled S1P receptors regulates many physiological systems, particularly the immune and vascular systems. Our understanding of the functions of S1P has been aided by the tractability of the system to both chemical and genetic manipulation. Chemical modulators have been generated to affect most of the known components of S1P biology, including agonists of S1P receptors and inhibitors of enzymes regulating S1P production and degradation. Genetic knockouts and manipulations have been similarly engineered to disrupt the functions of individual S1P receptors or enzymes involved in S1P metabolism. This chapter will focus on the development and utilization of these chemical and genetic tools to explore the complex biology surrounding S1P and its receptors, with particular attention paid to the in vivo findings that these tools have allowed for.

Multiple-dose tolerability, pharmacokinetics, and pharmacodynamics of ponesimod, an S1P1 receptor modulator: favorable impact of dose up-titration

This multiple-ascending-dose study investigated the safety, tolerability, pharmacokinetics, and pharmacodynamics of ponesimod, an S1P1 receptor modulator and a potential new treatment for autoimmune diseases. In part A, 10 healthy male and female subjects received once daily oral doses of ponesimod (5, 10, or 20 mg) or placebo for 7 days. Sinus bradycardia and, in some subjects, atrioventricular (AV) block occurred primarily on the first day of dosing, as desensitization developed to ponesimod-induced heart rate (HR) reduction and PR-prolongation. This elicited the design of an up-titration schedule in 17 subjects to a dose of 40 mg in part B. The up-titration regimen reduced HR and PQ/PR effects. Reported adverse events were mainly related to the cardiac and respiratory systems. Respiratory effects increased with higher doses. Ponesimod multiple-dose pharmacokinetics were slightly more than dose-proportional and characterized by a time to maximum concentration and an elimination half-life varying from 2.5 to 4.0 hours and 30.9 to 33.5 hours, respectively, and an accumulation of about 2.3-fold. Ponesimod caused a dose-dependent sustained decrease in total lymphocyte count, reversible within 7 days of discontinuation. A pharmacokinetic-pharmacodynamic model enabled comparing day 1 and steady-state conditions. These results warrant further investigation of ponesimod in patients.

The organization of the sphingosine 1-phosphate signaling system

The understanding of the role of the sphingosine 1-phosphate signaling system in immunology and host defense has deepened exponentially over the past 12 years since the discovery that lymphocyte egress was reversibly modulated by sphingosine 1-phosphate receptors, and with the development of fingolimod, a prodrug of a nonselective S1P receptor agonist, for therapeutic use in the treatment of relapsing, remitting multiple sclerosis. Innovative genetic and chemical approaches, together with structural biology, now provide a more detailed molecular understanding of a regulated lysophospholipid ligand with a variety of autocrine, paracrine, and systemic effects in physiology and pathology, based upon selective interactions with a high affinity and selective evolutionary cluster of G-protein-coupled receptors.

Effects of ponesimod, a selective S1P1 receptor modulator, on the pharmacokinetics of a hormonal combination contraceptive

PURPOSE

To determine the effects of steady-state concentrations of the selective S1P1 receptor modulator ponesimod on the pharmacokinetics (PK) of a single dose of a combined oral contraceptive, containing 1 mg norethisterone (NET) and 35 μg ethinyl estradiol (EE) and to investigate the effects on heart rate at different ponesimod doses within an up-titration regimen prior to co-administration of the contraceptive.

METHODS

Twenty-two healthy women (age: 29-60 years) received twice a single oral dose of the combined oral contraceptive, alone or in combination with multiple doses of 40 mg ponesimod attained by an up-titration regimen. Heart rate (HR) effects were assessed on the first day of each up-titration level. PK parameters of NET and EE were determined by non-compartmental analysis.

RESULTS

Geometric mean ratios (ponesimod and contraceptive / contraceptive alone) of Cmax and AUC0-24 of NET were 0.87 (90 % CI: 0.80, 0.94) and 0.84 (90 % CI: 0.76, 0.93), respectively. Geometric mean ratios of Cmax and AUC0-24 of EE were 0.94 (90 % CI: 0.86, 1.03) and 0.95 (90 % CI: 0.89, 1.01), respectively. The maximum mean HR reduction after the first dose of 10 mg ponesimod was 12.4 bpm (SD ± 6.2) at 2.5 h post-dose. On Day 4 (first dose of 20 mg) and Day 7 (first dose of 40 mg) the maximum mean HR reduction was 4.3 bpm (SD ± 5.7) and 1.4 (SD ± 6.4), respectively, at 2.5 h post-dose compared to baseline.

CONCLUSION

No clinically relevant PK interactions between ponesimod and the combined oral contraceptive were observed, therefore, efficacy of hormonal contraceptives is not expected to be affected by concomitant administration of ponesimod. The up-titration regimen showed that HR reductions are diminished upon repeated ponesimod administration.

Novel therapeutic options for multiple sclerosis

Multiple sclerosis (MS) is considered as an autoimmune disorder of the CNS with neuro-inflammatory and neurodegenerative components. We review here the innovative drugs recently registered and those in clinical development for MS. Immunomodulation has been the preferred therapeutic approach for MS since the first IFN-β was registered in the 1990s. Several immunomodulators are now available, which show a high efficacy in reducing the number of relapses in patients with the relapsing-remitting form of MS (RRMS). The high efficacy of most immunomodulators is, however, associated with substantial safety risks, notably concerning infections or cancers. Recently oral drugs have been approved for RRMS; however, biologics, and notably, monoclonal antibodies are still well represented in the development pipelines. An unmet medical need remains the treatment of the primary and secondary forms of MS or chronic progressive MS (CPMS). Half a dozen immunomodulators with proven efficacy in RRMS are now undergoing evaluation in Phase III trials in the CPMS indication. Neuroprotective drugs that prevent demyelination and/or improve remyelination would be interesting for CPMS, but these drugs are currently in the early development phase and their efficacy has not been demonstrated yet.

Second generation S1P pathway modulators: research strategies and clinical developments

Multiple Sclerosis (MS) is a chronic autoimmune disorder affecting the central nervous system (CNS) through demyelination and neurodegeneration. Until recently, major therapeutic treatments have relied on agents requiring injection delivery. In September 2010, fingolimod/FTY720 (Gilenya, Novartis) was approved as the first oral treatment for relapsing forms of MS. Fingolimod causes down-modulation of S1P1 receptors on lymphocytes which prevents the invasion of autoaggressive T cells into the CNS. In astrocytes, down-modulation of S1P1 by the drug reduces astrogliosis, a hallmark of MS, thereby allowing restoration of productive astrocyte communication with other neural cells and the blood brain barrier. Animal data further suggest that the drug directly supports the recovery of nerve conduction and remyelination. In human MS, such mechanisms may explain the significant decrease in the number of inflammatory markers on brain magnetic resonance imaging in recent clinical trials, and the reduction of brain atrophy by the drug. Fingolimod binds to 4 of the 5 known S1P receptor subtypes, and significant efforts were made over the past 5 years to develop next generation S1P receptor modulators and determine the minimal receptor selectivity needed for maximal therapeutic efficacy in MS patients. Other approaches considered were competitive antagonists of the S1P1 receptor, inhibitors of the S1P lyase to prevent S1P degradation, and anti-S1P antibodies. Below we discuss the current status of the field, and the functional properties of the most advanced compounds. This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.

Therapeutic use of a selective S1P1 receptor modulator ponesimod in autoimmune diabetes

In the present study, we investigated the therapeutic potential of a selective S1P₁ receptor modulator, ponesimod, to protect and reverse autoimmune diabetes in non-obese diabetic (NOD) mice. Ponesimod was administered orally to NOD mice starting at 6, 10, 13 and 16 weeks of age up to 35 weeks of age or to NOD mice showing recent onset diabetes. Peripheral blood and spleen B and T cell counts were significantly reduced after ponesimod administration. In pancreatic lymph nodes, B lymphocytes were increased and expressed a transitional 1-like phenotype. Chronic oral ponesimod treatment efficiently prevented autoimmune diabetes in 6, 10 and 16 week-old pre-diabetic NOD mice. Treatment withdrawal led to synchronized disease relapse. Ponesimod did not inhibit the differentiation of autoreactive T cells as assessed by adoptive transfer of lymphocytes from treated disease-free NOD mice. In addition, it did not affect the migration, proliferation and activation of transgenic BDC2.5 cells into the target tissue. However, ponesimod inhibited spreading of the T cell responses to islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP). Treatment of diabetic NOD mice with ponesimod induced disease remission. However, here again, upon treatment cessation, the disease rapidly recurred. This recurrence was effectively prevented by combination treatment with a CD3 antibody leading to the restoration of self-tolerance. In conclusion, treatment with a selective S1P₁ modulator in combination with CD3 antibody represents a promising therapeutic approach for the treatment of autoimmune diabetes.

Desensitization by progressive up-titration prevents first-dose effects on the heart: guinea pig study with ponesimod, a selective S1P1 receptor modulator

Ponesimod, a selective S1P₁ receptor modulator, reduces the blood lymphocyte count in all tested species by preventing egress of T and B cells from thymus and peripheral lymphoid organs. In addition, ponesimod transiently affects heart rate and atrioventricular (AV) conduction in humans, effects not observed in mice, rats, and dogs with selective S1P₁ receptor modulators, suggesting that the regulation of heart rate and rhythm is species dependent. In the present study, we used conscious guinea pigs implanted with a telemetry device to investigate the effects of single and multiple oral doses of ponesimod on ECG variables, heart rate, and blood pressure. Oral administration of ponesimod did not affect the sinus rate (P rate) but dose-dependently induced AV block type I to III. A single oral dose of 0.1 mg/kg had no effect on ECG variables, while a dose of 3 mg/kg induced AV block type III in all treated guinea pigs. Repeated oral dosing of 1 or 3 mg/kg ponesimod resulted in rapid desensitization, so that the second dose had no or a clearly reduced effect on ECG variables as compared with the first dose. Resensitization of the S1P₁ receptor in the heart was concentration dependent. After desensitization had been induced by the first dose of ponesimod, the cardiac system remained desensitized as long as the plasma concentration was ≥75 ng/ml. By using a progressive up-titration regimen, the first-dose effect of ponesimod on heart rate and AV conduction was significantly reduced due to desensitization of the S1P₁ receptor. In summary, conscious guinea pigs implanted with a telemetry device represent a useful model to study first-dose effects of S1P₁ receptor modulators on heart rate and rhythm. This knowledge was translated to a dosing regimen of ponesimod to be tested in humans to avoid or significantly reduce the first-dose effects.

Targeting the sphingosine-1-phosphate axis in cancer, inflammation and beyond

The bioactive lipid sphingosine-1-phosphate (S1P) is involved in multiple cellular signalling systems and has a pivotal role in the control of immune cell trafficking. As such, S1P has been implicated in disorders such as cancer and inflammatory diseases. This Review discusses the ways in which S1P might be therapeutically targeted - for example, via the development of chemical inhibitors that target the generation, transport and degradation of S1P and via the development of specific S1P receptor agonists. We also highlight recent conflicting results observed in preclinical studies targeting S1P and discuss ongoing clinical trials in this field.

Sphingosine kinase and sphingosine-1-phosphate: regulators in autoimmune and inflammatory disease

Sphingolipids and their metabolizing enzymes are beginning to be recognized as critical mediators in biological processes, specifically in inflammation and autoimmunity. Sphingosine kinases (SKs) and their lipid product sphingosine-1-phosphate (S1P) play essential roles in inflammatory signaling processes, as well as disease development and progression. SKs can be activated by numerous growth factors and cytokines, including TNF-α and IL-1β, leading to the generation of S1P. S1P exerts its biological effects on intracellular and extracellular targets, such as S1P receptors. In addition to roles in inflammatory signaling pathways SKs, S1P and S1P receptors have been implicated in immune cell function and trafficking, specifically in lymphocytes. This review will discuss the contribution of the bioactive sphingolipid S1P, its generating enzyme SK, and its cell surface receptors in the inflammatory and autoimmune diseases systemic lupus erythematosus, arthritis and inflammatory bowel disease.

Sphingosine 1-phosphate (S1P) receptor agonists mediate pro-fibrotic responses in normal human lung fibroblasts via S1P2 and S1P3 receptors and Smad-independent signaling

Synthetic sphingosine 1-phosphate receptor 1 modulators constitute a new class of drugs for the treatment of autoimmune diseases. Sphingosine 1-phosphate (S1P) signaling, however, is also involved in the development of fibrosis. Using normal human lung fibroblasts, we investigated the induction of fibrotic responses by the S1P receptor (S1PR) agonists S1P, FTY720-P, ponesimod, and SEW2871 and compared them with the responses induced by the known fibrotic mediator TGF-β1. In contrast to TGF-β1, S1PR agonists did not induce expression of the myofibroblast marker α-smooth muscle actin. However, TGF-β1, S1P, and FTY720-P caused robust stimulation of extracellular matrix (ECM) synthesis and increased pro-fibrotic marker gene expression including connective tissue growth factor. Ponesimod showed limited and SEW2871 showed no pro-fibrotic potential in these readouts. Analysis of pro-fibrotic signaling pathways showed that in contrast to TGF-β1, S1PR agonists did not activate Smad2/3 signaling but rather activated PI3K/Akt and ERK1/2 signaling to induce ECM synthesis. The strong induction of ECM synthesis by the nonselective agonists S1P and FTY720-P was due to the stimulation of S1P2 and S1P3 receptors, whereas the weaker induction of ECM synthesis at high concentrations of ponesimod was due to a low potency activation of S1P3 receptors. Finally, in normal human lung fibroblast-derived myofibroblasts that were generated by TGF-β1 pretreatment, S1P and FTY720-P were effective stimulators of ECM synthesis, whereas ponesimod was inactive, because of the down-regulation of S1P3R expression in myofibroblasts. These data demonstrate that S1PR agonists are pro-fibrotic via S1P2R and S1P3R stimulation using Smad-independent pathways.

The selective sphingosine 1-phosphate receptor modulator BAF312 redirects lymphocyte distribution and has species-specific effects on heart rate

BACKGROUND AND PURPOSE

BAF312 is a next-generation sphingosine 1-phosphate (S1P) receptor modulator, selective for S1P₁ and S1P₅ receptors. S1P₁ receptors are essential for lymphocyte egress from lymph nodes and a drug target in immune-mediated diseases. Here, we have characterized the immunomodulatory potential of BAF312 and the S1P receptor-mediated effects on heart rate using preclinical and human data.

EXPERIMENTAL APPROACH

BAF312 was tested in a rat experimental autoimmune encephalomyelitis (EAE) model. Electrophysiological recordings of G-protein-coupled inwardly rectifying potassium (GIRK) channels were carried out in human atrial myocytes. A Phase I multiple-dose trial studied the pharmacokinetics, pharmacodynamics and safety of BAF312 in 48 healthy subjects.

KEY RESULTS

BAF312 effectively suppressed EAE in rats by internalizing S1P₁ receptors, rendering them insensitive to the egress signal from lymph nodes. In healthy volunteers, BAF312 caused preferential decreases in CD4⁺ T cells, T_naïve, T_{central memory} and B cells within 4–6 h. Cell counts returned to normal ranges within a week after stopping treatment, in line with the elimination half-life of BAF312. Despite sparing S1P₃ receptors (associated with bradycardia in mice), BAF312 induced rapid, transient (day 1 only) bradycardia in humans. BAF312-mediated activation of GIRK channels in human atrial myocytes can fully explain the bradycardia.

CONCLUSION AND IMPLICATIONS

This study illustrates species-specific differences in S1P receptor specificity for first-dose cardiac effects. Based on its profound but rapidly reversible inhibition of lymphocyte trafficking, BAF312 may have potential as a treatment for immune-mediated diseases.

Fingolimod: direct CNS effects of sphingosine 1-phosphate (S1P) receptor modulation and implications in multiple sclerosis therapy

Fingolimod is the first oral disease-modifying therapy approved for relapsing forms of multiple sclerosis (MS). Following phosphorylation in vivo, the active agent, fingolimod phosphate (fingolimod-P), acts as a sphingosine 1-phosphate (S1P) receptor modulator, binding with high affinity to four of the five known S1P receptors (S1P1, S1P3, S1P4 and S1P5). The mechanism of action of fingolimod in MS has primarily been considered as immunomodulatory, whereby fingolimod-P modulates S1P1 on lymphocytes, selectively retaining autoreactive lymphocytes in lymph nodes to reduce damaging infiltration into the central nervous system (CNS). However, emerging evidence indicates that fingolimod has direct effects in the CNS in MS. For example, in the MS animal model of experimental autoimmune encephalomyelitis (EAE), fingolimod is highly efficacious in both a prophylactic and therapeutic setting, yet becomes ineffective in animals selectively deficient for S1P1 on astrocytes, despite maintained normal immunologic receptor expression and functions, and S1P-mediated immune activities. Here we review S1P signaling effects relevant to MS in neural cell types expressing S1P receptors, including astrocytes, oligodendrocytes, neurons, microglia and dendritic cells. The direct effects of fingolimod on these CNS cells observed in preclinical studies are discussed in view of the functional consequences of reducing neurodegenerative processes and promoting myelin preservation and repair. The therapeutic implications of S1P modulation in the CNS are considered in terms of the clinical outcomes of MS, such as reducing MS-related brain atrophy, and other CNS disorders. Additionally, we briefly outline other existing and investigational MS therapies that may also have effects in the CNS.

Efficacy and immunomodulatory actions of ONO-4641, a novel selective agonist for sphingosine 1-phosphate receptors 1 and 5, in preclinical models of multiple sclerosis

ONO-4641 is a next-generation sphingosine 1-phosphate (S1P) receptor agonist selective for S1P receptors 1 and 5. The objective of the study was to characterize the immunomodulatory effects of ONO-4641 using preclinical data. ONO-4641 was tested in both in-vitro pharmacological studies as well as in-vivo models of transient or relapsing-remitting experimental autoimmune encephalomyelitis (EAE). In vitro, ONO-4641 showed highly potent agonistic activities versus S1P receptors 1 and 5 [half maximal effective concentration (EC(50) ) values of 0·0273 and 0·334 nM, respectively], and had profound S1P receptor 1 down-regulating effects on the cell membrane. ONO-4641 decreased peripheral blood lymphocyte counts in rats by inhibiting lymphocyte egress from secondary lymphoid tissues. In a rat experimental autoimmune encephalomyelitis (EAE) model, ONO-4641 suppressed the onset of disease and inhibited lymphocyte infiltration into the spinal cord in a dose-dependent manner at doses of 0·03 and 0·1 mg/kg. Furthermore, ONO-4641 prevented relapse of disease in a non-obese diabetic mouse model of relapsing-remitting EAE. These observations suggest that ONO-4641 may provide therapeutic benefits in the treatment of multiple sclerosis.

Pharmacology of the sphingosine-1-phosphate signalling system

The recent success of FTY720 (Fingolimod, Gilenya(®)), which has been approved for the treatment of relapsing-remitting multiple sclerosis and is the first-in-class sphingosine-1-phosphate (S1P) receptor modulating drug, has boosted the interest in further drug development in this area. Several selective S1P1 receptor-modulating drugs are being investigated in clinical trials for the treatment of diverse autoimmune disorders. Sphingosine kinase inhibitors are under development for the treatment of cancer, aberrant angiogenesis and inflammatory diseases; an inhibitor of SK2 with relatively low affinity is being analysed in patients with advanced solid tumours. While an indirect S1P lyase inhibitor has just failed the proof of concept in patients with rheumatoid arthritis, S1P lyase is still a promising target for the treatment of inflammatory and autoimmune diseases. Another approach is the development of S1P-scavenging or -clearing agents, including a monoclonal S1P antibody that has successfully passed phase I clinical trials and will be further developed for age-related macular degeneration.

Sphingolipids as new biomarkers for assessment of delayed-type hypersensitivity and response to triptolide

Background

Hypersensitivity diseases are associated with many severe human illnesses, including leprosy and tuberculosis. Emerging evidence suggests that the pathogenesis and pathological mechanisms of treating these diseases may be attributable to sphingolipid metabolism.

Methods

High performance liquid chromatography-tandem mass spectrometry was employed to target and measure 43 core sphingolipids in the plasma, kidneys, livers and spleens of BALB/c mice from four experimental groups: control, delayed-type hypersensitivity (DTH) model, DTH+triptolide, and control+triptolide. Orthogonal partial least squares discriminant analysis (OPLS-DA) was used to identify potential biomarkers associated with variance between groups. Relationships between the identified biomarkers and disease markers were evaluated by Spearman correlation.

Results

As a treatment to hypersensitivity disease, triptolide significantly inhibit the ear swelling and recover the reduction of splenic index caused by DTH. The sphingolipidomic result revealed marked alterations in sphingolipid levels between groups that were associated with the effects of the disease and triptolide treatment. Based on this data, 23 potential biomarkers were identified by OPLS-DA, and seven of these biomarkers correlated markedly with the disease markers (p<0.05) by Spearman correlation.

Conclusions

These data indicate that differences in sphingolipid levels in plasma and tissues are related to DTH and treatment with triptolide. Restoration of proper sphingolipid levels may attribute to the therapeutic effect of triptolide treatment. Furthermore, these findings demonstrate that targeted sphingolipidomic analysis followed by multivariate analysis presents a novel strategy for the identification of biomarkers in biological samples.

An oral sphingosine 1-phosphate receptor 1 (S1P(1)) antagonist prodrug with efficacy in vivo: discovery, synthesis, and evaluation

A prodrug approach to optimize the oral exposure of a series of sphingosine 1-phosphate receptor 1 (S1P(1)) antagonists for chronic efficacy studies led to the discovery of (S)-2-{[3'-(4-chloro-2,5-dimethylphenylsulfonylamino)-3,5-dimethylbiphenyl-4-carbonyl]methylamino}-4-dimethylaminobutyric acid methyl ester 14. Methyl ester prodrug 14 is hydrolyzed in vivo to the corresponding carboxylic acid 15, a potent and selective S1P(1) antagonist. Oral administration of the prodrug 14 induces sustained peripheral blood lymphocyte reduction in rats. In a rat cardiac transplantation model coadministration of a nonefficacious dose of prodrug 14 with a nonefficacious dose of sotrastaurin (19), a protein kinase C inhibitor, or everolimus (20), an mTOR inhibitor, effectively prolonged the survival time of rat cardiac allografts. This demonstrates that clinically useful immunomodulation mediated by the S1P(1) receptor can be achieved with an S1P(1) antagonist generated in vivo after oral administration of its prodrug.

Sphingosine kinase and sphingosine-1-phosphate receptors: novel therapeutic targets of rheumatoid arthritis?

Rheumatoid arthritis (RA) is a chronic, destructive, autoimmune joint disease characterized by elevated levels of proinflammatory cytokine production. Sphingosine kinase (SphK) phosphorylates sphingosine into sphingosine-1-phosphate. Synovial fluid of RA patients exhibits significantly higher levels of S1P than their non-inflammatory osteoarthritis counterparts. SphK blockade suppresses cytokines and MMP-9 release in RA peripheral blood mononuclear cells. In addition, downregulation of SphK1 either through a specific siRNA approach or transgenic human TNF-α SphK1-deficient mice (hTNF-α/SphK1(-/-)) exhibit significantly less synovial inflammation and joint pathology. By contrast, SphK2 modulation leads to disease exacerbation. These results clearly demonstrate that such anti- and proinflammatory potential of SphK1/2 modulation may alter the outcome in RA synovitis and raises the possibility that drugs that specifically target SphK1 activity may play a beneficial role in the treatment of RA and other autoimmune rheumatic diseases.

G protein-coupled receptors as therapeutic targets for multiple sclerosis

G protein-coupled receptors (GPCRs) mediate most of our physiological responses to hormones, neurotransmitters and environmental stimulants. They are considered as the most successful therapeutic targets for a broad spectrum of diseases. Multiple sclerosis (MS) is an inflammatory disease that is characterized by immune-mediated demyelination and degeneration of the central nervous system (CNS). It is the leading cause of non-traumatic disability in young adults. Great progress has been made over the past few decades in understanding the pathogenesis of MS. Numerous data from animal and clinical studies indicate that many GPCRs are critically involved in various aspects of MS pathogenesis, including antigen presentation, cytokine production, T-cell differentiation, T-cell proliferation, T-cell invasion, etc. In this review, we summarize the recent findings regarding the expression or functional changes of GPCRs in MS patients or animal models, and the influences of GPCRs on disease severity upon genetic or pharmacological manipulations. Hopefully some of these findings will lead to the development of novel therapies for MS in the near future.

Fused tricyclic indoles as S1P₁ agonists with robust efficacy in animal models of autoimmune disease

Two series of fused tricyclic indoles were identified as potent and selective S1P(1) agonists. In vivo these agonists produced a significant reduction in circulating lymphocytes which translated into robust efficacy in several rodent models of autoimmune disease. Importantly, these agonists were devoid of any activity at the S1P(3) receptor in vitro, and correspondingly did not produce S1P(3) mediated bradycardia in telemeterized rat.