Siponimod (BAF312) prevents synaptic neurodegeneration in experimental multiple sclerosis

Mechanism of Siponimod: Anti-Inflammatory and Neuroprotective Mode of Action

Multiple sclerosis (MS) is a neuroinflammatory disorder of the central nervous system (CNS), and represents one of the main causes of disability in young adults. On the histopathological level, the disease is characterized by inflammatory demyelination and diffuse neurodegeneration. Although on the surface the development of new inflammatory CNS lesions in MS may appear consistent with a primary recruitment of peripheral immune cells, questions have been raised as to whether lymphocyte and/or monocyte invasion into the brain are really at the root of inflammatory lesion development. In this review article, we discuss a less appreciated inflammation-neurodegeneration interplay, that is: Neurodegeneration can trigger the formation of new, focal inflammatory lesions. We summarize old and recent findings suggesting that new inflammatory lesions develop at sites of focal or diffuse degenerative processes within the CNS. Such a concept is discussed in the context of the EXPAND trial, showing that siponimod exerts anti-inflammatory and neuroprotective activities in secondary progressive MS patients. The verification or rejection of such a concept is vital for the development of new therapeutic strategies for progressive MS.

The next-generation sphingosine-1 receptor modulator BAF312 (siponimod) improves cortical network functionality in focal autoimmune encephalomyelitis

Autoimmune diseases of the central nervous system (CNS) like multiple sclerosis (MS) are characterized by inflammation and demyelinated lesions in white and grey matter regions. While inflammation is present at all stages of MS, it is more pronounced in the relapsing forms of the disease, whereas progressive MS (PMS) shows significant neuroaxonal damage and grey and white matter atrophy. Hence, disease-modifying treatments beneficial in patients with relapsing MS have limited success in PMS. BAF312 (siponimod) is a novel sphingosine-1-phosphate receptor modulator shown to delay progression in PMS. Besides reducing inflammation by sequestering lymphocytes in lymphoid tissues, BAF312 crosses the blood-brain barrier and binds its receptors on neurons, astrocytes and oligodendrocytes. To evaluate potential direct neuroprotective effects, BAF312 was systemically or locally administered in the CNS of experimental autoimmune encephalomyelitis mice with distinct grey- and white-matter lesions (focal experimental autoimmune encephalomyelitis using an osmotic mini-pump). Ex-vivo flow cytometry revealed that systemic but not local BAF312 administration lowered immune cell infiltration in animals with both grey and white matter lesions. Ex-vivo voltage-sensitive dye imaging of acute brain slices revealed an altered spatio-temporal pattern of activation in the lesioned cortex compared to controls in response to electrical stimulation of incoming white-matter fiber tracts. Here, BAF312 administration showed partial restore of cortical neuronal circuit function. The data suggest that BAF312 exerts a neuroprotective effect after crossing the blood-brain barrier independently of peripheral effects on immune cells. Experiments were carried out in accordance with German and EU animal protection law and approved by local authorities (Landesamt für Natur, Umwelt und Verbraucherschutz Nordrhein-Westfalen; 87-51.04.2010.A331) on December 28, 2010.

Current advancements in promoting remyelination in multiple sclerosis

Current multiple sclerosis (MS) therapies are effective in reducing relapse rate, short-term measures of disability, and magnetic resonance imaging (MRI) measures of inflammation in relapsing remitting MS (RRMS), whereas in progressive/degenerative disease phases these medications are of little or no benefit. Therefore, the development of new therapies aimed at reversing neurodegeneration is of great interest. Remyelination, which is usually a spontaneous endogenous process, is achieved when myelin-producing oligodendrocytes are generated from oligodendrocyte precursor cells (OPCs). Even though these precursor cells are abundant in MS brains, their regeneration capacity is limited. Enhancing the generation of myelin-producing cells is therefore a major focus of MS research. Here we present an overview of the different advancements in the field of remyelination, including suitable animal models for testing remyelination therapies, approved medications with a proposed role in regeneration, myelin repair treatments under investigation in clinical trials, as well as future therapeutics aimed at facilitating myelin repair.

Delayed treatment of MS is associated with high CSF levels of IL-6 and IL-8 and worse future disease course

BACKGROUND

Clinical deterioration of relapsing-remitting MS (RR-MS) patients reflects not only the number and severity of overt inflammatory and demyelinating episodes, but also subtle central damage caused by persistent exposure to inflammatory molecules.

OBJECTIVE

To explore the correlation between levels of CSF inflammatory molecules at the time of diagnosis and both demographic and clinical characteristics of a large sample of RR-MS patients, as well as the predictive value of cytokine levels on their prospective disease course.

METHODS

In 205 patients diagnosed with RR-MS, we measured at the time of diagnosis the CSF levels of inflammatory molecules. Clinical and MRI evaluation was collected at the time of CSF withdrawal and during a median follow-up of 3 years.

RESULTS

The time interval between the first anamnestic episode of focal neurological dysfunction and RR-MS diagnosis was the main factor associated with high CSF levels of IL-6 and IL-8. Furthermore, elevated CSF levels of these cytokines correlated with enhanced risk of clinical and radiological disease reactivation, switch to second-line treatments, and with disability progression in the follow-up.

CONCLUSIONS

Delayed diagnosis and treatment initiation are associated with higher CSF levels of IL-6 and IL-8 in RR-MS, leading to worsening disease course and poor response to treatments.

Siponimod pharmacokinetics, safety, and tolerability in combination with rifampin, a CYP2C9/3A4 inducer, in healthy subjects

PURPOSE

To assess the potential pharmacokinetic (PK) interactions between siponimod and rifampin, a strong CYP3A4/moderate CYP2C9 inducer, in healthy subjects.

METHODS

This was a confirmatory, open-label, multiple-dose two-period study in healthy subjects (aged 18-45 years). In Period 1 (Days 1-12), siponimod was up-titrated from 0.25 to 2 mg over 5 days (Days 1-6) followed by 2 mg once daily on days 7-12. In Period 2, siponimod 2 mg qd was co-administered with rifampin 600 mg qd (Days 13-24). Primary assessments included PK of siponimod (Days 12 and 24; maximum steady-state plasma concentration [C_max,ss], median time to achieve C_max,ss [T_{max, ss}], and area under the curve at steady state [AUC_tau,ss]). Key secondary assessments were PK of M3 and M5 metabolites, and safety/tolerability including absolute lymphocyte count (ALC).

RESULTS

Of the 16 subjects enrolled (age, mean ± standard deviation [SD] 31 ± 8.3 years; men, n = 15), 15 completed the study. In Period 1, siponimod geometric mean C_max,ss (28.6 ng/mL) was achieved in 4 h (median T_max,ss; range, 1.58-8.00) and the geometric mean AUC_tau,ss was 546 h × ng/mL. In Period 2, the siponimod geometric mean C_max,ss and AUC_tau,ss decreased to 15.7 ng/mL and 235 h × ng/mL, respectively; median T_max remained unchanged (4 h). Rifampin co-administration increased M3 C_max,ss by 53% while M5 C_max,ss remained unchanged. The AUC_tau,ss of M3 and M5 decreased by 10% and 37%, respectively. The majority of adverse events reported were mild, with a higher frequency during Period 2 (86.7%) versus Period 1 (50%). The mean ALC increased slightly under rifampin co-administration but remained below 1.0 × 10⁹/L.

CONCLUSIONS

The study findings suggest that in the presence of rifampin, a strong CYP3A4/moderate CYP2C9 inducer, siponimod showed significant decrease in C_max,ss (45%) and AUC_tau,ss (57%) in healthy subjects.

Sphingosine 1-Phosphate Receptor Subtype 1 as a Therapeutic Target for Brain Trauma

Traumatic brain injury (TBI) provokes secondary pathological mechanisms, including ischemic and inflammatory processes. The new research in sphingosine 1-phosphate (S1P) receptor modulators has opened the door for an effective mechanism of reducing central nervous system (CNS) inflammatory lesion activity. Thus, the aim of this study was to characterize the immunomodulatory effect of the functional S1PR1 antagonist, siponimod, in phase III clinical trials for autoimmune disorders and of the competitive sphingosine 1-phosphate receptor subtype 1 (S1PR1) antagonist, TASP0277308, in pre-clinical development in an in vivo model of TBI in mice. We used the well-characterized model of TBI caused by controlled cortical impact. Mice were injected intraperitoneally with siponimod or TASP0277308 (1 mg/kg) at 1 and 4 h post-trauma. Our results demonstrated that these agents exerted significant beneficial effects on TBI pre-clinical scores in term of anti-inflammatory and immunomodulatory effects, in particular, attenuation of astrocytes and microglia activation, cytokines release, and rescue of the reduction of adhesion molecules (i.e., occludin and zonula occludens-1). Moreover, these compounds were able to decrease T-cell activation visible by reduction of CD4⁺ and CD8⁺, reduce the lesioned area (measured by 2,3,5-triphenyltetrazolium chloride staining), and to preserve tissue architecture, microtubule stability, and neural plasticity. Moreover, our findings provide pre-clinical evidence for the use of low-dose oral S1PR1 antagonists as neuroprotective strategies for TBI and broaden our understanding of the underlying S1PR1-driven neuroinflammatory processes in the pathophysiology of TBI. Altogether, our results showed that blocking the S1PR1 axis is an effective therapeutic strategy to mitigate neuropathological effects engaged in the CNS by TBI.

Siponimod versus placebo in secondary progressive multiple sclerosis (EXPAND): a double-blind, randomised, phase 3 study

BACKGROUND

No treatment has consistently shown efficacy in slowing disability progression in patients with secondary progressive multiple sclerosis (SPMS). We assessed the effect of siponimod, a selective sphingosine 1-phosphate (S1P) receptor_1,5 modulator, on disability progression in patients with SPMS.

METHODS

This event-driven and exposure-driven, double-blind, phase 3 trial was done at 292 hospital clinics and specialised multiple sclerosis centres in 31 countries. Using interactive response technology to assign numbers linked to treatment arms, patients (age 18-60 years) with SPMS and an Expanded Disability Status Scale score of 3·0-6·5 were randomly assigned (2:1) to once daily oral siponimod 2 mg or placebo for up to 3 years or until the occurrence of a prespecified number of confirmed disability progression (CDP) events. The primary endpoint was time to 3-month CDP. Efficacy was assessed for the full analysis set (ie, all randomly assigned and treated patients); safety was assessed for the safety set. This trial is registered with ClinicalTrials.gov, number NCT01665144.

FINDINGS

1651 patients were randomly assigned between Feb 5, 2013, and June 2, 2015 (1105 to the siponimod group, and 546 to the placebo group). One patient did not sign the consent form, and five patients did not receive study drug, all of whom were in the siponimod group. 1645 patients were included in the analyses (1099 in the siponimod group and 546 in the placebo). At baseline, the mean time since first multiple sclerosis symptoms was 16·8 years (SD 8·3), and the mean time since conversion to SPMS was 3·8 years (SD 3·5); 1055 (64%) patients had not relapsed in the previous 2 years, and 918 (56%) of 1651 needed walking assistance. 903 (82%) patients receiving siponimod and 424 (78%) patients receiving placebo completed the study. 288 (26%) of 1096 patients receiving siponimod and 173 (32%) of 545 patients receiving placebo had 3-month CDP (hazard ratio 0·79, 95% CI 0·65-0·95; relative risk reduction 21%; p=0·013). Adverse events occurred in 975 (89%) of 1099 patients receiving siponimod versus 445 (82%) of 546 patients receiving placebo; serious adverse events were reported for 197 (18%) patients in the siponimod group versus 83 (15%) patients in the placebo group. Lymphopenia, increased liver transaminase concentration, bradycardia and bradyarrhythmia at treatment initiation, macular oedema, hypertension, varicella zoster reactivation, and convulsions occurred more frequently with siponimod than with placebo. Initial dose titration mitigated cardiac first-dose effects. Frequencies of infections, malignancies, and fatalities did not differ between groups.

INTERPRETATION

Siponimod reduced the risk of disability progression with a safety profile similar to that of other S1P modulators and is likely to be a useful treatment for SPMS.

FUNDING

Novartis Pharma AG.

Environmental training is beneficial to clinical symptoms and cortical presynaptic defects in mice suffering from experimental autoimmune encephalomyelitis

The effect of "prophylactic" environmental stimulation on clinical symptoms and presynaptic defects in mice suffering from the experimental autoimmune encephalomyelitis (EAE) at the acute stage of disease (21 ± 1 days post immunization, d.p.i.) was investigated. In EAE mice raised in an enriched environment (EE), the clinical score was reduced when compared to EAE mice raised in standard environment (SE).Concomitantly, gain of weight and increased spontaneous motor activity and curiosity were observed, suggesting increased well-being in mice. Impaired glutamate exocytosis and cyclic adenosine monophosphate (cAMP) production in cortical terminals of SE-EAE mice were evident at 21 ± 1 d.p.i.. Differently, the 12 mM KCl-evoked glutamate exocytosis from cortical synaptosomes of EE-EAE mice was comparable to that observed in SE and EE-control mice, but significantly higher than that in SE-EAE mice. Similarly, the 12 mM KCl-evoked cAMP production in EE-EAE mice cortical synaptosomes recovered to the level observed in SE and EE-control mice. MUNC-18 and SNAP25 contents, but not Syntaxin-1a and Synaptotagmin 1 levels, were increased in cortical synaptosomes from EE-EAE mice when compared to SE-EAE mice. Circulating IL-1β was increased in the spinal cord, but not in the cortex, of SE-EAE mice, and it did not recover in EE-EAE mice. Inflammatory infiltrates were reduced in the cortex but not in the spinal cord of EE-EAE mice. Demyelination was observed in the spinal cord; EE significantly diminished it. We conclude that "prophylactic" EE is beneficial to synaptic derangements and preserves glutamate transmission in the cortex of EAE mice. This article is part of the Special Issue entitled "Neurobiology of Environmental Enrichment".

Laquinimod ameliorates excitotoxic damage by regulating glutamate re-uptake

Background

Laquinimod is an immunomodulatory drug under clinical investigation for the treatment of the progressive form of multiple sclerosis (MS) with both anti-inflammatory and neuroprotective effects. Excitotoxicity, a prominent pathophysiological feature of MS and of its animal model, experimental autoimmune encephalomyelitis (EAE), involves glutamate transporter (GluT) dysfunction in glial cells.

The aim of this study was to assess whether laquinimod might exert direct neuroprotective effects by interfering with the mechanisms of excitotoxicity linked to GluT function impairments in EAE.

Methods

Osmotic minipumps allowing continuous intracerebroventricular (icv) infusion of laquinimod for 4 weeks were implanted into C57BL/6 mice before EAE induction. EAE cerebella were taken to perform western blot and qPCR experiments. For ex vivo experiments, EAE cerebellar slices were incubated with laquinimod before performing electrophysiology, western blot, and qPCR.

Results

In vivo treatment with laquinimod attenuated EAE clinical score at the peak of the disease, without remarkable effects on inflammatory markers. In vitro application of laquinimod to EAE cerebellar slices prevented EAE-linked glutamatergic alterations without mitigating astrogliosis and inflammation. Moreover, such treatment induced an increase of Slcla3 mRNA coding for the glial glutamate–aspartate transporter (GLAST) without affecting the protein content. Concomitantly, laquinimod significantly increased the levels of the glial glutamate transporter 1 (GLT-1) protein and pharmacological blockade of GLT-1 function fully abolished laquinimod anti-excitotoxic effect.

Conclusions

Overall, our results suggest that laquinimod protects against glutamate excitotoxicity of the cerebellum of EAE mice by bursting the expression of glial glutamate transporters, independently of its anti-inflammatory effects.

Spotlight on siponimod and its potential in the treatment of secondary progressive multiple sclerosis: the evidence to date

Siponimod (BAF312) is a synthetic molecule belonging to the sphingosine-1-phosphate (S1P) modulator family, which has putative neuroprotective properties and well-characterized immunomodulating effects mediated by sequestration of B and T cells in secondary lymphoid organs. Compared to fingolimod (ie, precursor of the S1P modulators commercially available for the treatment of relapsing–remitting [RR] multiple sclerosis [MS]), siponimod exhibits selective affinity for types 1 and 5 S1P receptor, leading to a lower risk of adverse events that are mainly induced by S1P3 receptor activation, such as bradycardia and vasoconstriction. In addition, S1P1 and S1P5 receptors are expressed by neurons and glia and could mediate a possible neuroprotective effect of the drug. A Phase II clinical trial of siponimod for RR MS showed a significant effect of the active drug compared to placebo on reducing gadolinium-enhancing lesions on brain magnetic resonance imaging (MRI) after 3 months of treatment. In a recently completed Phase III trial, treatment with siponimod was associated with a significant reduction in disability progression in secondary progressive (SP) MS patients compared to placebo. In this article, current evidence supporting siponimod efficacy for SP MS is reviewed.

Impact of siponimod on vaccination response in a randomized, placebo-controlled study

OBJECTIVE

To evaluate effects of siponimod on response to T-cell-dependent (influenza) and T-cell-independent (pneumococcal polysaccharide vaccine [PPV-23]) vaccinations in healthy participants.

METHODS

In this double-blind, placebo-controlled, parallel-group study, each participant underwent a 7-week treatment period and received intramuscular injections of influenza and PPV-23 vaccines (day 21). Participants were randomized to 4 treatment groups (N = 30 each) and received placebo or siponimod 2 mg once daily in concomitant, interrupted, or preceding fashion. Individual response to vaccination was defined by a ≥4-fold (influenza) antibody titer increase and by a ≥2-fold increase in serotype-specific immunoglobulin (Ig) G concentrations (PPV-23) on day 28 vs baseline. Responder rates were compared using noninferiority analysis.

RESULTS

Mean influenza titers were similar to placebo in the preceding and interrupted groups but lower in the concomitant group. The proportion of participants with influenza titers ≥40 four weeks after vaccination (seroprotection) was similar to placebo across all groups and antigens. In each treatment group, response criteria were met for 3 of 4 antigens including H1N1 and H3N2. A noninferior response was determined in the context of preceding treatment but not interrupted or concomitant treatment. Regarding PPV-23, approximately 90%-100% of participants exhibited a ≥2-fold increase in IgG concentrations vs baseline. Noninferior responder rates were determined for each siponimod treatment group.

CONCLUSIONS

Siponimod treatment had no relevant effect on antibody response to PPV-23. European Medicines Agency response criteria were essentially met for influenza, but titers were lower on concomitant treatment. Overall, these data suggest that siponimod has limited effect on the efficacy of vaccinations with neoantigens.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that in healthy persons, siponimod had limited effect on the immune response following influenza or pneumococcal vaccinations.

CCL5-Glutamate Cross-Talk in Astrocyte-Neuron Communication in Multiple Sclerosis

The immune system (IS) and the central nervous system (CNS) are functionally coupled, and a large number of endogenous molecules (i.e., the chemokines for the IS and the classic neurotransmitters for the CNS) are shared in common between the two systems. These interactions are key elements for the elucidation of the pathogenesis of central inflammatory diseases. In recent years, evidence has been provided supporting the role of chemokines as modulators of central neurotransmission. It is the case of the chemokines CCL2 and CXCL12 that control pre- and/or post-synaptically the chemical transmission. This article aims to review the functional cross-talk linking another endogenous pro-inflammatory factor released by glial cells, i.e., the chemokine Regulated upon Activation Normal T-cell Expressed and Secreted (CCL5) and the principal neurotransmitter in CNS (i.e., glutamate) in physiological and pathological conditions. In particular, the review discusses preclinical data concerning the role of CCL5 as a modulator of central glutamatergic transmission in healthy and demyelinating disorders. The CCL5-mediated control of glutamate release at chemical synapses could be relevant either to the onset of psychiatric symptoms that often accompany the development of multiple sclerosis (MS), but also it might indirectly give a rationale for the progression of inflammation and demyelination. The impact of disease-modifying therapies for the cure of MS on the endogenous availability of CCL5 in CNS will be also summarized. We apologize in advance for omission in our coverage of the existing literature.