**2. Treating neurodegeneration in multiple sclerosis**

MS is an autoimmune disease in which elements of the neuronal myelin sheath are recognized as antigens by the immune system. Focal inflammatory and immune actions against neuronal cover cause a neurodegenerative process that leads to neurological impairment. The difficulty to characterize the neurodegenerative process supports the hypothesis that MS is a complex disease, with high variations among individuals. In any case, as a consequence of the immune aggression, an axonal loss progresses with the disease and represents the principal driver of disability in the chronic course of MS [1]. In this context, multiple mechanisms could contribute to demyelination and axonal injury including energy imbalance, ion accumulation, neuroin‐ flammation and astroglial response to oxidative and metabolic stress.

#### **2.1. Chronic neurodegenerative processes in multiple sclerosis**

About 85% of MS patients present the so-called relapsing-remitting (RR) form, characterized by unpredictable relapses related to inflammatory activity, followed by periods of months to years of relative quietness. During the remitting period, patients present no new signs of disease activity and, occasionally, partial remissions of symptoms associated with reparative processes are observed [2]. Progressive forms are less frequent forms of initial MS, but about 55–65% of relapsing-remitting multiple sclerosis (RRMS) patients develop a secondary progressive course [1].

At the pathophysiological level, the neurological impairment develops due to focal inflam‐ matory and immune attacks against the neuronal cover, which cause a chronic neurodege‐ nerative process. The reason why and where these focal demyelinating inflammatory lesions appear within the central nervous system (CNS) remains unknown. Current hypothesis establish that CD4-positive T lymphocytes are mainly responsible for the initial autoimmune attack, but with a secondary role in chronic neuronal damage [3]. Resident microglia and astrocytes, and infiltrated macrophages, B lymphocytes, natural killer (NK)-positive and CD8 positive T cells would be the major players in the neurodegenerative process [4, 5].

At the subcellular level, a plethora of inflammatory effectors mediating myelin and neuronal damage have been described. These effectors include molecules such as nitric oxide (NO), reactive oxygen species (ROS), tumour necrosis factor α (TNF-α), interferon γ (IFNγ), gran‐ zymes, perforin and matrix metalloproteinases, and also molecular processes such as activa‐ tion of the complement, antibody secretion and phagocytosis [4, 6, 7]. Furthermore, as a concomitant event, glutamate release from damaged axons will trigger excitotoxicity, which leads to ion imbalance and mitochondrial metabolic stress, feeding neuronal damage and neuroinflammation [8, 9]. Thus, inflammatory damage leads to oligodendrocyte death, axon demyelination, axonal damage, neuronal death and the formation of glial scars. Progressive axonal injury and neuronal loss increase with the course of MS and represent the principal driver of disability.

neuroprotective mechanism of action has been recently approved, broadening and improv‐

In this chapter, we review new drugs with proposed neuroprotective or neuroregenerative effects that are currently approved or in clinical trials for MS treatment. Although we highlight the diazoxide action on neuroinflammation and the results of a clinical trial with this drug, the

The articles analysed for this review were selected using PubMed database filtered by English language. Clinical trials were selected at the ClinicalTrials.gov database. Studies in the database labelled as "unknown status" were excluded. The initial search was done in Decem‐

MS is an autoimmune disease in which elements of the neuronal myelin sheath are recognized as antigens by the immune system. Focal inflammatory and immune actions against neuronal cover cause a neurodegenerative process that leads to neurological impairment. The difficulty to characterize the neurodegenerative process supports the hypothesis that MS is a complex disease, with high variations among individuals. In any case, as a consequence of the immune aggression, an axonal loss progresses with the disease and represents the principal driver of disability in the chronic course of MS [1]. In this context, multiple mechanisms could contribute to demyelination and axonal injury including energy imbalance, ion accumulation, neuroin‐

About 85% of MS patients present the so-called relapsing-remitting (RR) form, characterized by unpredictable relapses related to inflammatory activity, followed by periods of months to years of relative quietness. During the remitting period, patients present no new signs of disease activity and, occasionally, partial remissions of symptoms associated with reparative processes are observed [2]. Progressive forms are less frequent forms of initial MS, but about 55–65% of relapsing-remitting multiple sclerosis (RRMS) patients develop a secondary

At the pathophysiological level, the neurological impairment develops due to focal inflam‐ matory and immune attacks against the neuronal cover, which cause a chronic neurodege‐ nerative process. The reason why and where these focal demyelinating inflammatory lesions appear within the central nervous system (CNS) remains unknown. Current hypothesis establish that CD4-positive T lymphocytes are mainly responsible for the initial autoimmune attack, but with a secondary role in chronic neuronal damage [3]. Resident microglia and astrocytes, and infiltrated macrophages, B lymphocytes, natural killer (NK)-positive and CD8-

positive T cells would be the major players in the neurodegenerative process [4, 5].

review also includes other molecules with oral or parenteral administration.

**2. Treating neurodegeneration in multiple sclerosis**

flammation and astroglial response to oxidative and metabolic stress.

**2.1. Chronic neurodegenerative processes in multiple sclerosis**

ing the therapeutic landscape against MS.

308 Trending Topics in Multiple Sclerosis

ber 2015.

progressive course [1].

Key elements that mediate inflammation in MS are microglial cells. Microglia are often considered to be macrophages of the CNS, but a series of recent findings in the mouse have established that they are a unique cell population distinct from macrophages [10]. In normal conditions, microglia present a surveillance state and important roles in normal development, connectivity and plasticity of the CNS. However, they are transformed and activated by a range of signals, such as neuronal death, mechanical injury and toxins [11]. Once activated, they form the first line of defense against infection or injury to the CNS [12]. As a consequence, microglia mediate and trigger a neuroinflammatory response to injury. In MS, this microglial reaction is an early event that often precedes and triggers demyelination and neurodegeneration [13].

**Figure 1.** Dual role of microglia in MS. Reactive microglia mediate different pro-inflammatory (red arrows) and neuro‐ protective processes (green arrows) according to the diversity of signals from the lesioned axons and oligodendrocytes. OG, oligodendrocytes; OP, oligodendrocyte precursors; ROS, reactive oxygen species. (Cell drawings are from SERVI‐ ER Medical Art.)

Perivascular microglia are the antigen-presenting cells that recruit myelin-specific T cells and promote the inflammatory process inside the CNS. This process then activates parenchymal microglia by secreting pro-inflammatory and neurotoxic factors such as TNF-α, prostaglan‐ dins, interleukin-6 (IL-6), NO or ROS, which elicit myelin damage and neurodegeneration [11, 14]. Whether microglia adopt a phenotype that mostly exacerbates tissue injury or one that promotes brain repair is likely to depend on the diversity of signals from the lesion environ‐ ment and the response capacity of the cell (**Figure 1**).

As a response to the inflammatory aggression, reparative and regenerative processes are activated and originate MS remissions. This neuroprotective response is led by the activation of microglia and TH2-IL-10 lymphocyte pathways, and results in inhibition of the inflamma‐ tory process, up-regulation of antioxidant mechanisms, and secretion of neurotrophic factors. These processes promote remyelination by surviving oligodendrocytes and precursors [15– 17]. According to this, the progression of MS symptoms depends on a delicate balance between neuroinflammation and the regenerative process. However, neuronal regeneration is not an easy and common process within the CNS, especially for large myelinated neurons. Although myelin sheath can be partially restored, oligodendrocytes regenerated and axons repaired, and if the inflammatory insult persists, the degenerative damage becomes chronic and cannot be counteracted.

According to these processes, the therapeutic approaches for MS should follow three different but not exclusive strategies: (a) to suppress the autoimmune reaction by inhibiting the initial immune response and lymphocyte infiltration into the CNS, (b) to prevent neurodegenerative chronic damage by inhibiting neuroinflammation and fostering neuronal survival or (c) to promote myelin repair and neuroregeneration.

#### **2.2. Molecules with proposed neuroprotective and antioxidative activity**

Until recently, MS pharmacotherapy has been dominated by immunomodulatory drugs, which were developed on the basis that the disease was primarily an autoimmune disease. This hypothesis postulates that T lymphocytes specific for myelin antigens initiate an inflam‐ matory reaction in the CNS, which ultimately leads to demyelination and subsequent neuronal loss. However, since the approval of oral dimethyl fumarate to treat RRMS, with a proposed antioxidative neuroprotective mechanism of action, the therapeutic landscape for MS is rapidly evolving. Currently, the development of drugs with primarily CNS neuroprotective effects is a pharmaceutical priority.

Pursuit of neuroprotective therapies in MS provides new valid alternatives that could significantly impact on disease progression and neurodegenerative changes, including the promotion of myelin sheath restoration through the remyelination process [18]. Thus, fingo‐ limod, laquinimod, Anti-LINGO antibody, (-)-epigallotechin-3-gallate (EGCG) and diazoxide emerge as neuroprotective drugs for the treatment of MS (**Table 1**). Nevertheless, the neuro‐ protective effect of these compounds has not been fully established and requires further investigation.

Neuroprotection: A New Therapeutic Approach of Relapsing Remitting Multiple Sclerosis http://dx.doi.org/10.5772/63730 311


**Table 1.** Neuroprotective drugs for the treatment of RRMS.

Perivascular microglia are the antigen-presenting cells that recruit myelin-specific T cells and promote the inflammatory process inside the CNS. This process then activates parenchymal microglia by secreting pro-inflammatory and neurotoxic factors such as TNF-α, prostaglan‐ dins, interleukin-6 (IL-6), NO or ROS, which elicit myelin damage and neurodegeneration [11, 14]. Whether microglia adopt a phenotype that mostly exacerbates tissue injury or one that promotes brain repair is likely to depend on the diversity of signals from the lesion environ‐

As a response to the inflammatory aggression, reparative and regenerative processes are activated and originate MS remissions. This neuroprotective response is led by the activation of microglia and TH2-IL-10 lymphocyte pathways, and results in inhibition of the inflamma‐ tory process, up-regulation of antioxidant mechanisms, and secretion of neurotrophic factors. These processes promote remyelination by surviving oligodendrocytes and precursors [15– 17]. According to this, the progression of MS symptoms depends on a delicate balance between neuroinflammation and the regenerative process. However, neuronal regeneration is not an easy and common process within the CNS, especially for large myelinated neurons. Although myelin sheath can be partially restored, oligodendrocytes regenerated and axons repaired, and if the inflammatory insult persists, the degenerative damage becomes chronic and cannot be

According to these processes, the therapeutic approaches for MS should follow three different but not exclusive strategies: (a) to suppress the autoimmune reaction by inhibiting the initial immune response and lymphocyte infiltration into the CNS, (b) to prevent neurodegenerative chronic damage by inhibiting neuroinflammation and fostering neuronal survival or (c) to

Until recently, MS pharmacotherapy has been dominated by immunomodulatory drugs, which were developed on the basis that the disease was primarily an autoimmune disease. This hypothesis postulates that T lymphocytes specific for myelin antigens initiate an inflam‐ matory reaction in the CNS, which ultimately leads to demyelination and subsequent neuronal loss. However, since the approval of oral dimethyl fumarate to treat RRMS, with a proposed antioxidative neuroprotective mechanism of action, the therapeutic landscape for MS is rapidly evolving. Currently, the development of drugs with primarily CNS neuroprotective

Pursuit of neuroprotective therapies in MS provides new valid alternatives that could significantly impact on disease progression and neurodegenerative changes, including the promotion of myelin sheath restoration through the remyelination process [18]. Thus, fingo‐ limod, laquinimod, Anti-LINGO antibody, (-)-epigallotechin-3-gallate (EGCG) and diazoxide emerge as neuroprotective drugs for the treatment of MS (**Table 1**). Nevertheless, the neuro‐ protective effect of these compounds has not been fully established and requires further

**2.2. Molecules with proposed neuroprotective and antioxidative activity**

ment and the response capacity of the cell (**Figure 1**).

promote myelin repair and neuroregeneration.

effects is a pharmaceutical priority.

counteracted.

310 Trending Topics in Multiple Sclerosis

investigation.

#### *2.2.1. Dimethyl fumarate*

Fumaric acid esters (FAEs) are a group of simple low-molecular structured compounds that has been used for long time in the treatment of moderate to severe psoriasis [19]. Due to their immunomodulatory potential, FAEs were also evaluated as a potential treatment for RRMS. At preclinical stages, FAEs showed promising results in myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (MOG-EAE) mice, ameliorat‐ ing the disease course [20]. In vivo, the mechanism of action of dimethyl fumarate is not completely understood. For some authors, fumarate treatment induces IL-4-producing Th2 dendritic cells [21]. In the human and mice, type II dendritic cells subsequently produce the anti-inflammatory cytokines IL-10 and IL-4 instead of pro-inflammatory IL-12 and IL-23 [21]. This anti-inflammatory activity also causes apoptosis of activated T cells preserving the CNS from influx of activated lymphocytes.

Regarding the neuroprotective role of fumarate, other authors found in vitro and in vivo effects, potentially via up-regulation of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Dimethyl fumarate also exerts protective effects on oligodendrocytes, myelin, axons and neurons, and reduces oxidative stress as measured by protein nitrosylation [22]. Nonetheless, as recently shown, the protective effect of dimethyl fumarate could depend on pre-existing tissue expression of Nrf2. Actually, Nrf2 is intrinsically higher in astrocytes and macrophages from active MS lesions and increased Nrf2 levels have been recently reported in oligodendro‐ cytes from active MS lesions [23].

Two randomized, placebo- and active-controlled, double-blind, parallel-group Phase III studies (DEFINE and CONFIRM) of dimethyl fumarate (Code name BG-12) have been conducted (funded by Biogen Idec). The primary end point of these studies was the proportion of patients who had a 2-year relapse. Secondary end points included the annualized relapse rate (ARR), the time to confirmed progression of disability as measured by Expanded Disa‐ bility Status Scale (EDSS), and findings on brain magnetic resonance imaging scan (MRI) such as the number of gadolinium-enhancing lesions. Both studies described highly significant superiority of BG-12 to placebo on almost all end points in patients with RRMS [24]. In the DEFINE and CONFIRM extension study (ENDORSE), a minimum of 5 years of treatment with the drug was associated with continued benefit and no new/worsening tolerability signals. Thus, in March 2013, the Food and Drug Administration (FDA) approved dimethyl fumarate as a new first-line oral treatment for patients with RRMS. In September 2013, it was also approved in Canada and Australia and, in 2014, the European Commission has approved the use of the drug for the treatment of RRMS in Europe.

#### *2.2.2. Fingolimod*

Fingolimod became the first drug approved for relapsing forms of MS in the USA in 2010. However, some safety issues were identified during the drug development process, after completion of trials and in the first months of clinical use in the United States. These issues led to the approval of fingolimod as a second-line drug by the European Medicines Agency (EMA) after the FDA had licensed it as a first-line agent. In addition, contradictory results regarding efficacy on progression of disability in MS patients were found in the two pivotal Phase III trials that allowed fingolimod marketing in most countries [18].

Although fingolimod was primarily believed to be a pure immunosuppressive compound, recent findings revealed direct effects on the CNS [25]. When incorporated to the organism, fingolimod is rapidly phosphorylated by sphingosine kinases [26] and the product of this phosphorylation, phosphofingolimod, is a potent modulator of S1P receptors. Administration of fingolimod and similar S1P1 modulators produce marked beneficial effects on different animal models of MS, especially when administered preventively. The proposed mechanism of action for fingolimod is the inhibition of encephalitogenic T-cell responses and/or their migration into the CNS [27, 28]. According to this, EAE animals treated with fingolimod showed a dramatic decrease of T lymphocytes infiltrated in the CNS and even a reversible peripheral lymphocytopaenia. These animals also showed better myelin preservation and decrease of pro-inflammatory cytokine production [29].

In the CNS, both neurons and glia profusely express S1P receptors. Some of the beneficial effects of fingolimod in EAE and MS could be attributed to SP1 receptor modulation in these cells and result in neuroprotection. Activation of neuronal S1P1 and S1P3 receptors promotes neurogenesis and increases neurite outgrowth, although high and continuous activation of neuronal S1P receptors could lead to overactivation of the glutamatergic system with delete‐ rious effects [30]. In microglia, fingolimod promotes anti-inflammatory and neuroprotective phenotypes, but the exact mechanism of action involved remains unclear [31]. Furthermore, one of the most discussed direct effects of fingolimod on the CNS is on myelin repair and oligodendrocyte regeneration [32, 33].

One Phase II study, followed by an active extension, and two clinical Phase III placebocontrolled and active comparator-controlled clinical trials (named TRANSFORMS and FREEDOMS, sponsored by Novartis) have been performed with fingolimod in patients with RRMS. These studies have demonstrated the efficacy of fingolimod in treating RRMS [34, 35]. More recently, FREEDOMS II, a third Phase III trial of fingolimod, was conducted predomi‐ nantly in USA and Canada. The trial replicated the findings of FREEDOMS regarding the ARR and MRI outcomes, but the significant effect on reducing EDSS score progression was not confirmed. On the other hand, disability showed a statistically significant change in favour of fingolimod treatment in the FREEDOMS II study [36]. Finally, the recently completed IN‐ FORMS trial showed no significant benefit of fingolimod on neurological disability in primary progressive MS patients treated for at least 3 years [37].

#### *2.2.3. Laquinimod*

*2.2.1. Dimethyl fumarate*

312 Trending Topics in Multiple Sclerosis

from influx of activated lymphocytes.

cytes from active MS lesions [23].

*2.2.2. Fingolimod*

use of the drug for the treatment of RRMS in Europe.

Fumaric acid esters (FAEs) are a group of simple low-molecular structured compounds that has been used for long time in the treatment of moderate to severe psoriasis [19]. Due to their immunomodulatory potential, FAEs were also evaluated as a potential treatment for RRMS. At preclinical stages, FAEs showed promising results in myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (MOG-EAE) mice, ameliorat‐ ing the disease course [20]. In vivo, the mechanism of action of dimethyl fumarate is not completely understood. For some authors, fumarate treatment induces IL-4-producing Th2 dendritic cells [21]. In the human and mice, type II dendritic cells subsequently produce the anti-inflammatory cytokines IL-10 and IL-4 instead of pro-inflammatory IL-12 and IL-23 [21]. This anti-inflammatory activity also causes apoptosis of activated T cells preserving the CNS

Regarding the neuroprotective role of fumarate, other authors found in vitro and in vivo effects, potentially via up-regulation of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Dimethyl fumarate also exerts protective effects on oligodendrocytes, myelin, axons and neurons, and reduces oxidative stress as measured by protein nitrosylation [22]. Nonetheless, as recently shown, the protective effect of dimethyl fumarate could depend on pre-existing tissue expression of Nrf2. Actually, Nrf2 is intrinsically higher in astrocytes and macrophages from active MS lesions and increased Nrf2 levels have been recently reported in oligodendro‐

Two randomized, placebo- and active-controlled, double-blind, parallel-group Phase III studies (DEFINE and CONFIRM) of dimethyl fumarate (Code name BG-12) have been conducted (funded by Biogen Idec). The primary end point of these studies was the proportion of patients who had a 2-year relapse. Secondary end points included the annualized relapse rate (ARR), the time to confirmed progression of disability as measured by Expanded Disa‐ bility Status Scale (EDSS), and findings on brain magnetic resonance imaging scan (MRI) such as the number of gadolinium-enhancing lesions. Both studies described highly significant superiority of BG-12 to placebo on almost all end points in patients with RRMS [24]. In the DEFINE and CONFIRM extension study (ENDORSE), a minimum of 5 years of treatment with the drug was associated with continued benefit and no new/worsening tolerability signals. Thus, in March 2013, the Food and Drug Administration (FDA) approved dimethyl fumarate as a new first-line oral treatment for patients with RRMS. In September 2013, it was also approved in Canada and Australia and, in 2014, the European Commission has approved the

Fingolimod became the first drug approved for relapsing forms of MS in the USA in 2010. However, some safety issues were identified during the drug development process, after completion of trials and in the first months of clinical use in the United States. These issues led to the approval of fingolimod as a second-line drug by the European Medicines Agency (EMA) after the FDA had licensed it as a first-line agent. In addition, contradictory results regarding

Laquinimod (N-ethyl-N-phenyl-5-chloro-1,2-dihydroxy-1-methyl-2-oxo-quinoline-3-carbox‐ amide) is structurally related to linomide, which was tested for efficacy in MS more than one decade ago, and discontinued after serious adverse events occurred in a Phase III trial [38, 39]. After an extensive screening of a large number of chemically modified quinoline-3 carboxamides, laquinimod was selected to have less toxicity and better efficacy than linomide in various experimental autoimmune inflammatory-mediated animal models, including experimental autoimmune neuritis in Lewis rats [40].

The precise mechanism by which laquinimod induces these beneficial effects is yet to be fully elucidated. Preclinical studies in EAE mice have shown that laquinimod might protect myelin and axons by decreasing pro-inflammatory cytokines such as IL-17 by T cells [41]. In addition, suppression of the nuclear factor-kappaB (NF-κB) pathway that concordantly led to the activation of apoptosis of immunocompetent cells was also induced by laquinimod, proving the anti-inflammatory potency of the drug [42]. Regarding the effects in the CNS, laquinimod treatment prevented the loss of brain-derived neurotrophic factor (BDNF) induced by the disease process. In EAE mice, laquinimod induced an elevation of BDNF expression in various brain regions to reach similar BDNF concentration as that of naïve controls [43]. In the human, a Phase II study undergoing laquinimod treatment showed a significant and specific elevation of serum BDNF levels compared to the placebo group after 3 months of treatment [44]. Whether laquinimod directly affects BDNF expression within the neurons, or induces bystander mechanisms that arrest the inflammatory progression and facilitates neuroprotection, needs to be further clarified.

Two Phase III clinical trials of laquinimod in RRMS (the ALLEGRO and BRAVO trial spon‐ sored by TEVA) have been completed. In the first one, treatment with laquinimod as compared with placebo was associated with a modest reduction in ARR, decreased the risk of disability progression and reduced the number of gadolinium-enhancing lesions detected by MRI. However, the failure to meet primary end point in the BRAVO study led the manufacturer to delay requesting FDA approval. On May 2013, laquinimod was approved in Russia as a treatment for RRMS.

Nevertheless, in 2013 Teva Pharmaceutical and Active Biotech started the third Phase III trial of laquinimod in patients with RRMS. The study is designed to evaluate the safety and efficacy of laquinimod with a primary end point of time to confirmed disability progression, as measured by the EDSS (CONCERTO trial, ClinicalTrials.gov Identifier: NCT01707992). CONCERTO results are expected to be available towards mid-2017.

#### *2.2.4. Anti-LINGO antibody*

Nogo receptor-interacting protein (LINGO-1) is a transmembrane signal-transducing mole‐ cule, selectively expressed by oligodendrocytes and neurons and that associates with the Nogo-66 receptor (NgR1) complex [45]. NgR1 binds myelin-associated inhibitors of axonal regeneration such as Nogo-A, myelin-associated glycoprotein and oligodendrocyte myelin glycoprotein [46]. In response to CNS injury and demyelination, oligodendrocyte precursor cells and stem cells from the white matter become activated, migrate to the demyelinated area, proliferate and differentiate into oligodendrocytes that will remyelinate damaged axons. In chronic MS lesions, despite the presence of oligodendrocyte precursors in demyelinated plaques and the close proximity between pre-myelinating oligodendrocytes and demyelinated axons, axonal remyelination failed. This suggests that the differentiation process may be locally blocked by inhibitory factors [47].

In animal models, LINGO-1 expression is up-regulated in rat spinal cord injury, experimental EAE, 6-hydroxydopamine neurotoxic lesions and glaucoma models [48, 49]. Several works have reported the blockade of Nogo signalling as a therapeutic approach for neurological disorders such as spinal cord injury, traumatic brain injury, stroke, schizophrenia, amyotro‐ phic lateral sclerosis and MS [50]. Animal models provide evidence that LINGO-1 is a potent inhibitor of axonal remyelination and regeneration in vivo. For example, transgenic mice overexpressing full-length LINGO-1 under the neuronal promoter of synapsin showed a significant reduction in the number of myelinated axons in the spinal cord and brain at P8 [51]. Other authors showed that neurite outgrowth inhibitor Nogo-A is involved in autoimmunemediated demyelination in vivo [52].

BIIB033 is a monoclonal antibody that inhibits LINGO-1 and promotes axonal integrity/ remyelination in MOG-EAE mice [49]. In preclinical experiments, LINGO-1 antagonist antibodies did not alter EAE onset but did significantly mitigate disease severity across all stages of disease progression. This functional recovery in EAE correlates with improved axonal integrity as determined by magnetic resonance diffusion tensor imaging, and with newly formed myelin sheaths as determined by electron microscopy [53].

Biogen Idec Inc. started two different human studies with BIIB033 in 2010 (ClinicalTrials.gov Identifier: NCT01244139 and NCT01052506, respectively). Both studies finished in 2012 and BIIB033 showed favourable safety profile, desirable pharmacokinetic in healthy adults and MS patients and predicted brain penetration [53]. Based on these promising results, in 2013, Biogen started a Phase II dose-response study to assess the efficacy, safety, tolerability and pharma‐ cokinetics of BIIB033 in 400 RRMS patients when used concurrently with Interferon β-1a (Avonex®) (SYNERGY, ClinicalTrials.gov Identifier: NCT01864148). SYNERGY results are expected to be available along 2016.

#### *2.2.5. (−)-Epigallotechin-3-gallate*

in various experimental autoimmune inflammatory-mediated animal models, including

The precise mechanism by which laquinimod induces these beneficial effects is yet to be fully elucidated. Preclinical studies in EAE mice have shown that laquinimod might protect myelin and axons by decreasing pro-inflammatory cytokines such as IL-17 by T cells [41]. In addition, suppression of the nuclear factor-kappaB (NF-κB) pathway that concordantly led to the activation of apoptosis of immunocompetent cells was also induced by laquinimod, proving the anti-inflammatory potency of the drug [42]. Regarding the effects in the CNS, laquinimod treatment prevented the loss of brain-derived neurotrophic factor (BDNF) induced by the disease process. In EAE mice, laquinimod induced an elevation of BDNF expression in various brain regions to reach similar BDNF concentration as that of naïve controls [43]. In the human, a Phase II study undergoing laquinimod treatment showed a significant and specific elevation of serum BDNF levels compared to the placebo group after 3 months of treatment [44]. Whether laquinimod directly affects BDNF expression within the neurons, or induces bystander mechanisms that arrest the inflammatory progression and facilitates neuroprotection, needs

Two Phase III clinical trials of laquinimod in RRMS (the ALLEGRO and BRAVO trial spon‐ sored by TEVA) have been completed. In the first one, treatment with laquinimod as compared with placebo was associated with a modest reduction in ARR, decreased the risk of disability progression and reduced the number of gadolinium-enhancing lesions detected by MRI. However, the failure to meet primary end point in the BRAVO study led the manufacturer to delay requesting FDA approval. On May 2013, laquinimod was approved in Russia as a

Nevertheless, in 2013 Teva Pharmaceutical and Active Biotech started the third Phase III trial of laquinimod in patients with RRMS. The study is designed to evaluate the safety and efficacy of laquinimod with a primary end point of time to confirmed disability progression, as measured by the EDSS (CONCERTO trial, ClinicalTrials.gov Identifier: NCT01707992).

Nogo receptor-interacting protein (LINGO-1) is a transmembrane signal-transducing mole‐ cule, selectively expressed by oligodendrocytes and neurons and that associates with the Nogo-66 receptor (NgR1) complex [45]. NgR1 binds myelin-associated inhibitors of axonal regeneration such as Nogo-A, myelin-associated glycoprotein and oligodendrocyte myelin glycoprotein [46]. In response to CNS injury and demyelination, oligodendrocyte precursor cells and stem cells from the white matter become activated, migrate to the demyelinated area, proliferate and differentiate into oligodendrocytes that will remyelinate damaged axons. In chronic MS lesions, despite the presence of oligodendrocyte precursors in demyelinated plaques and the close proximity between pre-myelinating oligodendrocytes and demyelinated axons, axonal remyelination failed. This suggests that the differentiation process may be locally

CONCERTO results are expected to be available towards mid-2017.

experimental autoimmune neuritis in Lewis rats [40].

to be further clarified.

314 Trending Topics in Multiple Sclerosis

treatment for RRMS.

*2.2.4. Anti-LINGO antibody*

blocked by inhibitory factors [47].

Green tea consumption has been associated to differences in the incidence of some diseases such as different kinds of cancer or cardiovascular pathologies [54]. Its composition includes, among other bioactive molecules, vitamins, pro-vitamins and antioxidants. Some of the more abundant components are tea polyphenols, also known as catechins, especially the (-) epigallotechin-3-gallate (EGCG) [55]. EGCG has been profusely studied as an anticancer compound, as long as it can cause apoptosis and arrest cell cycle of tumoural cells [56]. As long as EGCG presents antioxidative properties, it can act as a chelator of neurotoxic metals and inhibit pro-inflammatory processes [57].

Efficacy studies in the EAE models for MS have shown that, alone or in combination with approved treatments for MS, oral EGCG ameliorated disease course and decreases EAE severity, preventing and reversing disability. This positive effect has been mainly attributed to the inhibition of NF-κB-mediated inflammation, cell proliferation, TNF-α secretion and Th1/ Th2 response. EGCG enhanced axonal preservation and inhibited neuronal apoptosis in treated animals [58]. The neuroprotective profile of EGCG has been attributed to its activity as a free radical scavenger [58]. Although this effect may be related with the inhibition of NF- κB pathway and glial reactivity, this indirect neuroprotection is also of main interest for the treatment of MS and other neurodegenerative diseases.

Several epidemiologic studies and clinical trials have been performed to test the preventive and therapeutic effects of EGCG in neurodegenerative diseases such as Alzheimer's, Parkin‐ son's or Huntington's diseases [59]. In general, these studies show no EGCG-related preven‐ tion of neuronal and glial cell death in patients [59]. In 2013, a multicentric Phase II national study to investigate the anti-inflammatory and neuroprotective effects of EGCG in 120 RRMS patients was started (SuniMS Study, ClinicalTrials.gov identifier: NCT00525668, sponsored by Charite University, Berlin, Germany). At the moment, no results are available for this study.

Finally, to analyse the metabolic effects of EGCG and to assess the importance of lipid oxidation in fuel muscle's energy metabolism and its relationship with muscle weakness and fatigue in RRMS patients, the same institution completed a clinical research trial in 2013 (ClinicalTri‐ als.gov identifier: NCT01417312). Results showed that EGCG given to MS patients over 12 weeks improves muscle metabolism during moderate exercise to a greater extent in men than in women, possibly because of sex-specific effects on autonomic and endocrine control. These results indicate that EGCG could be a promising treatment for MS, with a good- and wellknown safety profile and an interesting combinability with other treatments. However, as the EGCG pass through the blood-brain barrier in humans is still controversial, its bioavailability remains to be characterized [60].
