Cannabidiol and epilepsy: Rationale and therapeutic potential

Accepted Manuscript Title: Cannabidiol and epilepsy: rationale and therapeutic potential Author: Antonio Leo Emilio Russo Maurizio Elia PII: DOI: Reference:

S1043-6618(16)30179-7 http://dx.doi.org/doi:10.1016/j.phrs.2016.03.005 YPHRS 3092

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Pharmacological Research

Received date: Revised date: Accepted date:

1-2-2016 7-3-2016 8-3-2016

Please cite this article as: Leo Antonio, Russo Emilio, Elia Maurizio.Cannabidiol and epilepsy: rationale and therapeutic potential.Pharmacological Research http://dx.doi.org/10.1016/j.phrs.2016.03.005 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Cannabidiol and epilepsy: rationale and therapeutic potential

Antonio Leoa, Emilio Russoa, Maurizio Eliab,*

a

Department Science of Health, School of Medicine and Surgery, University of Catanzaro, Italy;

b

Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Troina (EN), Italy.

Running Title: Cannabidiol as a potential antiepileptic drug

* Author for correspondence: Dr. Maurizio Elia, MD Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), 94018 Troina (EN), ITALY Phone +39 0935 936111/Fax: +39 0935 653327 e-mail: [email protected]

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Graphical abstract

Abstract Despite the introduction of new antiepileptic drugs (AEDs), the quality of life and therapeutic response for patients with epilepsy remains still poor. Unfortunately, besides several advantages, these new AEDs have not satisfactorily reduced the number of refractory patients. Therefore, the need for different other therapeutic options to manage epilepsy is still a current issue. To this purpose, emphasis has been given to phytocannabinoids, which have been medicinally used since ancient time in the treatment of neurological disorders including epilepsy. In particular, the nonpsychoactive compound cannabidiol (CBD) has shown anticonvulsant properties, both in preclinical and clinical studies, with a yet not completely clarified mechanism of action. However, it should be made clear that most phytocannabinoids do not act on the endocannabinoid system as in the case of CBD. In in vivo preclinical studies, CBD has shown significant anticonvulsant effects mainly in acute animal models of seizures, whereas restricted data exist in chronic models of epilepsy as well as in animal models of epileptogenesis. Likewise, clinical evidence seem to indicate that CBD is able to manage epilepsy both in adults and children affected by refractory seizures, with a favourable side effect profile. However, to date, clinical trials are both qualitatively 2

and numerically limited, thus yet inconsistent. Therefore, further preclinical and clinical studies are undoubtedly needed to better evaluate the potential therapeutic profile of CBD in epilepsy, although the actually available data is promising.

Keywords: Cannabidiol; Epilepsy; Seizures; Preclinical studies; Clinical evidence.

1. Introduction Epilepsy is a prevalent and devastating disorder of the central nervous system (CNS) defined as a brain condition that causes spontaneous recurrent seizures, which are sometimes both progressively severe and accompanied by cognitive and behavioural comorbidities [1]. The term ‘seizures’ describes an excessive, paroxysmal change in the electrical activity in a group of neurons. Epileptogenesis (latency period) refers to a scantily understood cascade of events that gradually transmute a non-epileptic brain into one that triggers spontaneous seizures; these events occurr in a specific time-window included between a brain-damaging insult such as stroke, infection or genetic predisposition, and the onset of unprovoked and unpredictable seizures [1,2]. During the silent period a specific treatment might stop or modify the epileptogenic process and thus positively influences the quality of life of an epileptic subject [3,4]. Furthermore, during this specific period of time, the identification of reliable biomarkers of epilepsy could also be helpful to discover new and more effective antiepileptogenic strategies [5]. Nowadays, among the major unmet needs in the treatment of epilepsy there is the identification of disease-modifying drugs that can completely prevent epilepsy or slow its progression. Unfortunately, the newer antiepileptic drugs (AEDs) as well as the older AEDs present solely symptomatic properties, whereas they do not possess antiepileptogenic or disease modifying features. Until now, keeping in mind this urgent need, many preclinical studies conducted on several animal models have been performed [1,2,6,7]. Furthermore, these new AEDs, which have 3

not improved the outcome of refractory epilepsy, show also several side effects influencing the quality of life of epileptic patients as much as seizures [8,9]. Likewise, also the neuropsychiatric comorbidities, which are common in epilepsy, may be often more problematic to patients than the seizures themselves [10-12]. Therefore, based on these evidence, the aim of researchers is the identification of new therapies able to manage epileptogenesis, epilepsy and the issues related to it [5]. Once again, in fact, it has been given much emphasis to phytocannabinoids (terpenophenolic compounds synthesized by several cannabis species). Cannabis has been medicinally used for centuries in the treatment of neurological disorders including epilepsy [13,14]. Actually, despite several evidence suggests that cannabinoids could be useful to treat several diseases, the clinical use of cannabinoid-based therapy remains only limited to spasticity/pain in multiple sclerosis and nausea in chemotherapy [14].

2. Antiseizure effects of CBD: potential molecular targets The pharmacological interest in cannabis compounds was arisen after the identification of two major neuroactive components: 9-tetrahydrocannabinol (THC) and the nonpsychotropic cannabidiol (CBD), as well as after the discovery of an endogenous cannabinoid-signalling pathway [15,16]. CBD, the second most abundant phytocannabinoid extracted mainly from cannabis sativa and cannabis indica, has demonstrated antiseizure activity and a good side-effect profile [17,18]. These CBD’s features together with its lack of psychotropic effects have lead to more detailed studies both preclinically and clinically, some of which are still on-going [19]. Regarding THC, its antiseizure effects are controversial with pro- and anti-convulsant effects being reported; furthermore, THC induces both the development of tolerance and psychotropic effects. These THC’s features have restricted its investigation in clinical trials in comparison to CBD [20,21]. However, regarding CBD, further studies are still needed to better characterize its pharmacokinetic profile, above all the drug-drug interaction between AEDs and CBD as well as to understand the precise molecular mechanism(s) through which CBD exerts its pharmacological effects. Moreover, 4

(see sections 4 and 5) new well-designed clinical trials are needed to clarify its effects in epilepsy [19,22]. As widely reported in literature, the exact molecular target(s) by which CBD exerts its pharmacological properties are still undetermined [23]. However, it has already been demonstrated how CBD, in comparison to THC, does not activate the cannabinoid type 1 (CB1) and type 2 (CB2) receptors. Despite this low affinity for the cannabinoid receptors, CBD is able to antagonize CB1 and CB2 receptor agonists in vitro with unexpectedly high potency [24]. These properties of CBD could explain its lack of psychotropic effects [25,26]. Accordingly, it has been possible to affirm that the CBD’s therapeutic properties in neurological disorders, such as epilepsy, are independent of the endocannabinoid-signalling pathway, whereas, according to Devinsky, et al. [15], these properties could be linked to a “multi-target drug” profile. Among the molecular targets of CBD, currently identified, there are several enzymes, receptors, ion channels, and transporters. Unfortunately, some effects of CBD, on these targets, have been obtained through in vitro assays only at supra-therapeutical doses that are not achieved in vivo (implausible targets). The plausible and implausible CBD’s molecular targets as well as the potential pharmacological effects of CBD in neurological disorders including epilepsy have been recently reviewed by Ibeas Bih, et al. [23]. Briefly, regarding its anticonvulsant activity, it has been reported that CBD might influence neuronal hyperexcitability by several mechanisms: 1) reducing the synaptic release of glutamate as a result of its antagonism on the G protein-coupled receptor (GPR) 55; 2) activating 5-HT1a receptors [27,28]; 3) stimulating and desensitizing transient receptor potential of ankyrin type 1 (TRPA1) channel; 4) stimulating and desensitizing transient receptor potential of vanilloid type 1 (TRPV1) and 2 (TRPV2) channels [29,30]; 5) inhibiting the synaptic uptake of noradrenaline, GABA, adenosine as well as dopamine [31,32]; 6) stimulating the activity of 3 and 1 glycine receptors [33,34]. Likewise, other potential targets of CBD have been hypothesized, however, for some of them including; voltage-dependent anion channel 1 (VDAC1), peroxisome proliferator-activated receptor 5

γ (PPAR-), nitric oxide (NO), cyclooxygenase (COX), tumour necrosis factor (TNF), fatty acid amide hydrolase (FAAH) and G protein-coupled receptor (GPR) 18 the CBD’s potency on these molecular targets as well as the validity of the target in epilepsy needs to be better clarified by further studies. Accordingly, it is not surprising that CBD has also shown antioxidant, antinflammatory and neuroprotective properties [23,35-37], which might be useful to manage also other brain disorders. In fact, recently, it has also been demonstrated that long-term CBD treatment can prevent memory deficits in a transgenic mouse model of Alzheimer's disease [38]. In addition, it has also been suggested that CBD has antipsychotic, antidepressant and anxiolytic properties. The CBD’s effects on cognitive functions as well as mood might be also useful considering epilepsy comorbidities, which represents an important issue in the management of epileptic patients [10,3943]. Nonetheless, antiepileptic activity has also been demonstrated, both in vitro assay and in vivo studies, for several others phytocannabinoids such as cannabidivarin (CBDV), cannabichromene (CBC) and Δ9-tetrahydrocannabidivarin (Δ9-THCV); however, until now, clinical studies have only been performed mainly for CBD [15] (see sections 4 and 5). However, recently, among the cannabis compounds, particular interest has been born around CBDV, which is the propyl variant of cannabidiol [44,45]. In particular, CBDV has also shown anticonvulsant properties via an endocannabinoid receptor-independent mechanism. CBDV’s anticonvulsant effects could be linked to several molecular targets including TRP channels or through the inhibition of diacylglycerol lipase A. For CBDV further studies are needed to better characterize its potential molecular targets as well as to assess its anticonvulsant effects in patients with epilepsy. To this aim clinical trials are ongoing (see section 4

[30,46].

3. Antiseizure effects of CBD: preclinical studies CBD has shown anticonvulsant activity in many acute animal models of seizures, whereas few data and no data are present respectively in animal models of chronic epilepsy and as well as in animal

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models of epileptogenesis [15,35]. In these preclinical experimental studies, CBD has been effective similarly to the AEDs currently used in clinical therapy [47]. Previous studies, in mice, reported how a pre-treatment with CBD was able to prevent tonicseizures induced by GABA inhibitors including picrotoxin, pentylentetrazol (PTZ), bicuculline, isoniazide and by transcorneal electroshock, whereas CBD was not able to prevent seizures induced by the glycine antagonists strychnine [48]. Likewise, CBD (60 mg/kg; i.p.) has not shown effects on focal seizures with secondary generalization, induced by cobalt implantation, whereas THC markedly decreased the occurrences of seizures in this model [49]. Other studies have detected the ability of CBD to stop tonic but not clonic seizures in animal models of epilepsy such as PTZ and maximal electroshock (MES) models. As a result, it has been hypothesized that CBD could act mainly to decrease the spreading of seizures, whereas it partially influences seizures onset [50,51]. Moreover, using animal models of seizures, such as the MES model, it has also been observed that CBD can increase the antiseizure effects of AEDs such as phenytoin but it can also decrease the effects of other AEDs such as clonazepam and ethosuximide [47,52]. This capability of CBD to interact with other AEDs could be related to both pharmacokinetic and pharmacodynamic interactions. In particular, the drug-drug interaction, among AEDs and CBD, could be linked to CBD’s ability to inhibit several isoforms of cytochrome P450 (CYP450) [53]. Very recently, in a clinical study Geffrey, et al. [22] have reported how the drugdrug interaction between CBD and clobazam, which are both catalysed by CYP450 (CYP2C9 and CYP3A4) pathway, could be useful in children with refractory epilepsy (see section 4). Recently, PTZ and MES models of seizure have been used to evaluate the CBD’s effect against generalized convulsion as well as to investigate potential mechanism(s) underlying its antiepileptic effect. In particular, Jones, et al. [54], in the PTZ model of seizures, have observed how a CBD pretreatment (100 mg/Kg; i.p.) has been able to decrease the occurrence of PTZ-seizures as well as the mortality, when compared to control rats. In the same study, through multielectrode array recordings, the antiepileptiform properties of CBD (0.01-

in hippocampal brain slices 7

treated both with Mg2+-free and 4-amynopyridine solutions were demonstrated. Moreover, this study has also confirmed that both the antiepileptiform activity in vitro and antiseizure activity in vivo of CBD are independent from CB1 receptor [54]. Similarly, in another study, Shirazi-zand, et al. [55] have investigated the involvement of BK channels in the CBD’s anticonvulsant effects. To this purpose, in mice, MES and PTZ models of seizures were used. In the PTZ mouse model, CBD pre-treatment (0.2, 2, 20, and 200 ng/mouse; i.c.v.) has shown anticonvulsant effects, which have been diminished by co-administration of paxilline, which is an antagonist of BK channels. Likewise, CBD pre-treatment (20, 100, and 200 ng/mouse; i.c.v.) has also demonstrated anticonvulsant effects in MES induced seizures; however, in this model CBD’s effects have not been modified by co-administration of paxilline. Therefore, according to the authors, these results seem to suggest that the antiseizure effect of CBD, in PTZ model, could be linked to BK channels while this mechanism might not be involved in CBD effects in the MES and possibly other models [55,56]. Very recently, the antiseizure effects of CBD (10, 20 and 50 mg/kg; i.v.) have also been evaluated in a chronic model of epilepsy, which has been obtained by PTZ administration for 28 consecutive days. In particular, CBD pre-treatment (20 and 50 mg/Kg), in rats, has been able to reduce PTZ induced seizures. The epileptic behaviour following PTZ administration has also been evaluated both through morphological changes of the hippocampal neurons and through glial fibrillary acidic protein (GFAP) immunohistochemical study. In particular, CBD treated rats, when compared to control group, have also shown lower neuronal death in CA1 and CA3 hippocampal regions. Likewise, GFAP immunohistochemistry reported that CBD has been able to decrease hippocampal astrocytic hyperplasia after PTZ induced seizures; to date, astrocytes seem to play an important but not completely understood role in the mechanisms underlying epilepsy [57,58]. Furthermore, the hippocampal expression of N-methyl-D-aspartic acid (NMDA) receptor subunit 1, in rats treated with CBD was reduced [59].

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The anticonvulsant properties of CBD have also been assessed in animal models of temporal lobe epilepsy (TLE) as well as in animal models of partial epilepsy. In particular, Jones, et al. [36] have studied the antiepileptic properties of CBD (1, 10 and 100mg/kg; i.p.) in two well-validated preclinical models of epilepsy: the pilocarpine model of TLE and the penicillin model of partial seizures. CBD pre-treatment (1 and 100 mg/kg; i.p.) in the pilocarpine rat model decreased the occurrences of tonic–clonic seizures, whereas did not influence the percentage of mortality. At odds, in the penicillin model of seizures, CBD treatment (≥10 mg/kg; i.p.) reduced both tonic– clonic seizures and mortality. Furthermore, in this study, several behavioural tests such as rotarod test have highlighted how CBD treatment had minimal side effects on motor performances at anticonvulsant doses [36]. In conclusion, these data support the anticonvulsant role of CBD, in several animal models of epilepsy, when it is administered as a pre-treatment. However, very recently, Hosseinzadeh, et al. [60] have also studied the CBD’s antiseizure effects after pilocarpineinduced seizures. In this study, CBD has been administered in two different groups of rats; in the first group, five consecutive days of CBD injections (100 ng; i.c.v.) have been carried out at the onset of the silent phase of pilocarpine induced status epilepticus, whereas in the second group a single injection of CBD (100 ng; i.c.v.) at the beginning of the chronic phase of pilocarpine induced status epilepticus. CBD in each group has been able to reduce seizures’ related behaviour (assessed by Racine scale). Moreover, the repeated administrations of CBD, during the silent phase, have been also able to delay the onset of spontaneous recurrent seizures (SRS). These CBD’s protective effects have been related to both an increased autophagy and an augmented antioxidant defence in hippocampal cells of epileptic rats [60]. As reported above, CBD has also neuroprotective properties that were also evaluated in hypoxic-ischemic newborn pigs. In fact, the administration of CBD (0.1 mg/kg, i.v.) in newborn pigs, after hypoxic-ischemic damage, has been able to prevent oedema as well as seizures onset. In particular, it seems that CBD could exert neuroprotective effects, in newborn pigs, through both CB2 and 5HT1A receptors. In particular, CBD acts as an agonist of 5HT1A receptors, whereas the involvement of CB2 receptors could be linked to an 9

indirect action of CBD. In fact, CBD can influence CB2 receptor increasing the levels of endocannabinoids in the brain [28,61,62]. As reported above, also CBDV, the propyl variant of CBD, has demonstrated anticonvulsant activity both in in vitro assays and in in vivo preclinical studies. In particular, Hill, et al. [63] have reported antiseizure effects of CBDV (1-100 μM) against epileptiform local field potentials (LFPs) provoked in hippocampal slices by administration both of 4-AP and Mg2+-free solutions. According to Iannotti, et al. [30], the antiepileptiform effects of CBDV, in the Mg2+-free model, could be linked to an activation and desensitization of TRPV1 channels. Likewise, in the study performed by Hill, et al. [63], CBDV pre-treatment (1 hour before seizure induction) has also shown antiseizure properties in several animal models of epilepsy including MES (CBDV = 100 mg/kg; i.p.), audiogenic (CBDV = 50 mg/kg; i.p.) and PTZ (CBDV = 100 mg/kg; i.p.) models. At odds, CBDV (200 mg/kg; i.p.) alone has not shown effects against pilocarpine-induced seizures. In fact, CBDV (200 mg/kg; i.p.) has decreased seizures, in pilocarpine model, only when combined with other AEDs such as valproate or phenobarbital [63]. Finally, Amada, et al. [64] have demonstrated significant anticonvulsant effects of CBDV (400 mg/kg, p.o.) on acute PTZ induced seizures in rats related to an augmented expression of epilepsy-related genes including Fos, Egr1, Arc, Ccl4 and BDNF [64].

4. Cannabidiol in epilepsy: clinical studies The available body of evidence for the clinical use of cannabinoids for the treatment of human epilepsy is mainly based on case reports, epidemiological studies, telephone or online surveys of neurologists, general practitioners, care givers or patients, randomized and blinded studies as well as interventional ongoing trials (Table 1) [65]. To date, despite the several potential administration routes for CBD, the majority of clinical trials report CBD per os administration through an oilbased formulation. However, after oral administration, CBD owns variable pharmacokinetics properties, which are the consequence both of its low water solubility and of significant first-pass 10

metabolism of CBD in the liver. Particularly, the oral bioavailability of CBD has been estimated in about 10% [15] with a Tmax of 90-120 minutes. CBD’s distribution volume is about 30L/Kg [45] with a potential of fast accumulation in fat organs such as brain. As a result of this, the CBD’s halflife has been assessed in about 24h. Furthermore, CBD in the plasma is highly bound to proteins (> 99%). The clearance, evaluated after i.v. administration, ranged from 960 to 1560 ml/min. [66,67]. Similarly to other cannabinoids, CBD results mainly metabolized by cytochrome P450 (CYP450) pathway, whereas its metabolites are widely excreted in the faeces [68]. In particular, it has been demonstrated that CBD can inhibit several isoforms of CYP450. As a result of this, drug-drug interactions are possible and worth particular attention [69]. Regarding to this, recently, Geffrey, et al. [22] have demonstrated how the drug-drug interactions between clobazam and CBD might be used to manage refractory epilepsy in children.

4.1 Case series and epidemiological studies Some anecdotal reports suggest that cannabis has antiepileptic properties and would be effective to manage focal epilepsies and generalized tonic-clonic seizures, however, also seizure exacerbation after cannabis use has been observed [17]. In 1949, Davis and Ramsey reported an experience on 5 children with epilepsy and intellectual disability who took tetrahydrocannabinol (THC) isomers up to 4 mg/day; 2 of them improved and 1 worsened [70]. Moreover, 2 other case reports also suggested that marijuana use could reduce seizure frequency [71,72]. However, another young man who had been seizure free for six months smoked marijuana 7 times in 3 weeks and had three tonic–clonic seizures during that time [73], though none of these recurrent seizures occurred during or immediately after consumption. In a more recent paper, 6 children with epilepsy and intellectual disability were exposed to tetrahydrocannabinol (THC) up to 0.12 mg/kg/day; four of them improved [74]. 2 adult patients with focal epilepsy nearly controlled their seizures through regular marijuana smoking use. However, when they stopped marijuana upon admission to the epilepsy monitoring 11

unit they have shown a dramatic increase in seizure frequency documented by video-EEG telemetry [75]. Saade and Joshi [76], for the first time, described the case of a 10-month-old boy affected by malignant migrating partial seizures in infancy (MMPS) who was pharmacoresistant to several AEDs. His parents, autonomously, decided to administer CBD to their child. Parents reported that after two weeks of co-administration with CBD, his sun was a “new baby”. In fact, after adding CBD (25 mg/mL at 10 mg/kg/day divided twice daily, up to 25 mg/kg/day twice daily) to his pharmacological therapy, seizure reduction as well as no side effects were observed. Likewise, the boy has been capable to maintain oral nutrition [76].

4.2 Surveys In order to determine the prevalence of marijuana use in epileptic patients a telephone survey was performed. Of the 136 interviewed subjects, 65 (48%) had consumed marijuana in their lifetime; 28 (21%) were active users. The OR of frequent marijuana use was eight times greater for patients with frequent seizures (95% CI, 0.9 to 69.0). The OR of frequent marijuana use were 10.1 (1.1 to 97.5) times greater for those with a disease duration of 5 to 10 years and 1.6 (95% CI, 0.2 to 14.1) times greater for those with a disease duration of >10 years versus those with a disease duration of <5 years. 32 patients (24%) had heard it was beneficial for epilepsy [77]. Often to manage child's drug-resistant epilepsy, parents try to find alternative pharmacological treatment. Recently, a U.S. survey of 19 parents belonging to a Facebook group dedicated to sharing evidence about the administration of CBD-enriched cannabis in their children was examined. These children were affected by several type of resistant-epilepsy such as Dravet syndrome (13), Doose syndrome (4) and one each presented Lennox–Gastaut syndrome and idiopathic epilepsy. In children, the dosages of CBD reported ranged from less than 0.5 mg/kg/day to 28.6 mg/kg/day, whereas the dosages of THC present within samples ranged from 0 to 0.8 mg/kg/day. 16 of the 19 12

parents (84%) reported a decrease in their child's seizure occurrences during CBD-enriched cannabis administration. Of these, 2 parents reported total seizure freedom, whereas other parents reported a reduction in seizure occurrences from 25% to over 80%. Furthermore, children have shown other positive effects, including improved alertness, better mood as well as restored quality of sleep. The side effects described were sleepiness and fatigue [78]. In another study, 310 outpatients at a tertiary epilepsy clinic in Berlin have been questioned both to evaluate the consumption of illicit drugs among patients with epilepsy and to study the effects of these drugs on epilepsy. 63 of 310 recruited subjects (20.3%) have used cannabis after the diagnosis of epilepsy. Active cannabis consumption has been predicted by sex (male) (OR 5.342, 95% CI, 1.416 – 20.153) and age (OR 0.956; 95% CI, 0.919 – 0.994). Finally, this study affirmed that Cannabis use does not worsen epilepsy, in contradiction to what happened after abuse of other illicit drugs [79]. To better evaluate the role of CBD in pediatric resistant-epilepsy including infantile spasms and Lennox-Gastaut syndrome, a brief online survey has been performed on 117 parents who have administered CBD products to their children affected by epilepsy. Particularly, CBD-enriched oilbased extracts, 2–3 times a day, was mainly used. Only some parents have reported the specific CBD dosage as well as the weight of the patients. The CBD median dosage has been 4.3 mg/kg/day (range = 2.9–7.5), whereas the median duration of CBD treatment has been 6.8 months (range = 3.8–9.8). Overall, 85% of parents have described a significant reduction in seizures occurrence, whereas 14% reported seizures freedom. At odds, 5 parents have referred an increase in seizures occurrence. Moreover, these patients have shown several positive effects including enhanced alertness and better mood, whereas the side effect recorded, after CBD administration, was increased food intake [80]. In another retrospective study performed in Colorado (U.S.), 75 children and adolescents who have been administrated oral cannabis extracts for management of their epilepsy were identified. 43 (57%) parents of these children with several pediatric resistant-epilepsy including Dravet and 13

Lennox–Gastaut syndrome have referred improvement in seizures management, whereas 25 (33%) patients have attested a reduction of 50% of the seizures. 2 patients were seizures free. Furthermore, several other positive effects such as improved language, enhanced motor performance and better mood were reported. The responder rate also varied according to epilepsy type: Dravet 23%, Doose 0%, and Lennox–Gastaut syndrome (LGS) 88.9%. Side effects have been reported in 44% of patients treated with oral cannabis extract [81]. To date, it seems that fewer medical specialists approve clinical use of marijuana and CBD to treat severe epilepsy. Therefore, from May 20 to September 2014, Epilepsia has carried out an online survey concerning the use of medical marijuana and CBD in epileptic patients. The survey was based on 8 questions. Among these questions, four concerned: if data on safety (1) and efficacy (2) of clinical use of marijuana were sufficient, 3) if it was possible to use medical marijuana in severe refractory epilepsy and 4) if compounds containing CBD should be available. Among 776 subjects enrolled in the survey, there were both patients and medical professionals including neurologists who declared that the amount of data concerning the safety (34%) and the efficacy (28%) were sufficient. Moreover, 48% of these professionals would advise clinical use of marijuana to manage epilepsy. At odds, the majority of patients affirm that sufficient safety and efficacy data existed, and 98% would advise clinical marijuana in severe epilepsy. Likewise, the opinions of other health, no medical, professionals were similar to those of patients. In conclusion, this survey confirms that fewer medical professionals, in comparison to patients, endorse using clinical cannabis to manage severe epilepsy [82]. Very recently, a retrospective study was performed to describe the experience of 5 Israeli pediatric clinics in the management of child's refractory epilepsy. In particular, this study reported the experience of 74 subjects (age range 1-18 years) with refractory epilepsy who received, for at least 3 months, cannabis oil containing CBD (dose ranged from 1 to 20 mg/Kg/day) and THC at ratio of 20:1. Overall, 66 subjects have shown a variable reduction in seizure occurrences (from 100% to < 25%), whereas 7 subjects have reported enhancement of seizures. Furthermore, this study reported other beneficial effects such as improved motor performances, 14

language and better mood. Only in 5 patients the side effects observed have been severe enough to determine CBD withdrawal. In conclusion, also this study supports the clinical use of CBD in children with intractable epilepsy [83].

4.3 Controlled trials Today, only four-controlled clinical studies about the therapeutic application of CBD have been published [17]. In the first one, 15 patients affected by temporal lobe epilepsy with secondary generalized seizures, not well controlled by standard AEDs, while continuing to take their regular therapy, were enrolled for a randomized, double-blind, parallel group study. Particularly, 8 patients received CBD (200–300 mg per day, per os), whereas the other 7 subjects received a placebo. Of the 8 CBD treated patients, four became and remained seizure-free during the treatment with CBD (8-18 weeks), three exhibited a clinical improvement, while the other CBD treated patients did not improve. In the placebo group, 6 out of 7 patients remained unchanged and one has shown clinical improvement. Drowsiness was reported by 4 patients on CBD, whereas no severe side effects were reported [84]. In the second study, 12 patients with uncontrolled seizures and intellectual disability have been divided in two groups. In the first one, patients received three capsules of sunflower oil (as placebo), whereas in the second, patients received three capsules of sunflower oil and 100 mg of CBD for the first week. During the following three weeks, patients received two capsules per day. No differences in seizure frequency between the two groups were found, although no other details were provided. The only side effect was mild drowsiness [85]. In the third study, 9 patients with uncontrolled epilepsy were divided in CBD treated group (4) and in placebo group (5). In particular, in the CBD group patients have been treated with 200 mg daily of CBD, in addition to their habitual AEDs therapy. At odds, the second group received placebo, in addition to their habitual AEDs therapy. Study duration was three months. Two of 4 patients treated with CBD achieved seizure freedom, during the three months of treatment; one has only had partial 15

improvement, whereas the last one has not shown beneficial clinical effects. Likewise, none of the 5 patients treated with placebo had clinical improvement. No side effects were detected [86]. The fourth trial was only described in one conference (unpublished abstract). 12 patients were treated with a single-blind placebo for 6 months followed by double-blind 300 mg of CBD or placebo in a cross-over trial lasting an additional 12 months. No statistics were performed, but a preliminary review suggested that there was some reduction in seizure frequency [87]. Unfortunately, these studies, based on poor-quality data, failed to provide strong evidence on the efficacy of the treatment with CBD, due to the small number of patients in each trial, ranging from 9 to 15. Moreover, these trials have not clarified whether CBD is effective per se or through the enhancement of other AEDs’ effects. Recently, a Cochrane review of randomized controlled trials conducted to evaluate both the efficacy and the safety of CBD treatment in epilepsy has affirmed that, at the present, there are not reliable evidence concerning the efficacy of cannabinoids and CBD as a treatment for epilepsy, and have suggested, in agreement with other studies, that a series of well designed double-blind randomized clinical studies for any disorder including epilepsy should be performed. Anyway, there is sufficient evidence that 200-300 mg/daily of CBD in adults is usually well-tolerated, although the safety of long-term treatment could not be determined, due to the short length of the treatment in the studies, ranging from one to 12 months [17,18]. Also in a more recent systematic review, the authors concluded that, on the basis of two evidence Class IV studies [84,85], there is not sufficient evidence to prescribe CBD or recommend self-treatment with smoked marijuana for epilepsy [88].

4.4. Ongoing interventional trials At the moment, several clinical trials, registered in ClinialTrials.gov, regard the use of cannabinoids in epilepsy. Eight of these fifteen studies are using Epidiolex (GWP42003: GWPharmaceuticals), which represents the plant-derived CBD; four are using synthetically produced CBD (Insys Therapeutics), 16

whereas three are using CBDV, which is the propyl variant of CBD (GWP42006: GWPharmaceuticals). Particularly, among the trials planned for CBD oral solution there are one phase I/II open label trial in children with drug-resistant epilepsy, and three phase III clinical trials in subjects affected by Dravet (DS) and Lennox–Gastaut (LGS) syndromes. The studies performed with Epidiolex include children and adults with Dravet, Lennox–Gastaut and Sturge–Weber syndromes and subjects suffering from other forms of pharmacoresistant epilepsy [89]. Very recently, an open-label interventional trial has been carried out in 214 patients (aged 1-30 years) with severe, childhood-onset, pharmacoresistant epilepsy (including Dravet and Lennox– Gastaut) who received oral CBD at 2-5 mg/kg daily, up to a dose of 25 mg/kg or 50 mg/kg per day (depending on the study). During the treatment period, CBD has been able to reduce the occurrence of motor seizures (monthly reduction 36.5%). Moreover, according to this study, CBD could have a favorable safety profile [90]. Considering that CBD and clobazam (CLB) are metabolized by cytochrome P450 (CYP), their potential pharmacological interaction has been studied. In fact, the drug-drug interaction between CBD and CLB could be used to manage refractory epilepsy in children. To this purpose an expanded access investigational new drug trial in 25 subjects was performed. 13 out of 25 patients have been treated with CBD (5mg/Kg/day each week up to 25mg/Kg/day) and CLB (mean doses, 1mg/Kg/day). Elevated levels of CLB and norclobazam (nCLB), the active metabolite of CLB, were found in these patients. Nine out of 13 patients receiving CBD and CLB have shown a significant seizure reduction (>50%). The increased CLB and nCLB levels as well as seizures reduction have also been maintained when CLB doses were decreased for 10 out of 13 patients. Side effects have been reported in 10 of the 13 subjects, but have been improved with CLB dose reduction. Therefore, it has been suggested that the addition of CBD in patients treated with CLB could be useful in the management of refractory epilepsy [22].

5. Conclusion 17

In conclusion, many in vitro and in vivo studies support the role of CBD in the management of epilepsy. In particular, in these studies, CBD has shown several advantages including both its ability to reduce seizures as well as the currently available AEDs and its favourable side effects profile in comparison to currently applied AEDs in therapy [35,47]. Likewise, CBD, in animal models, has also demonstrated effects on cognitive performance as well as in mood disorders. These effects could be useful in the management of psychiatric comorbidities that are often more harmful than seizures themselves. However, regarding the preclinical studies, some issues deserve to be clarified. In fact, to date, the majority of preclinical data concern the effects of CBD in acute animal models of seizures, whereas few data exist in chronic models of epilepsy as well as in animal models of epileptogenesis. Moreover, many of these in vivo studies have only evaluated the anticonvulsant effects of a pre-treatment with CBD, whereas few data are available on a posttreatment with CBD. Likewise, CBD’s pharmacokinetic and pharmacodynamics profile remains also unclear [15]. Similarly, evidence reported anticonvulsant effects of CBD in humans. In particular, anecdotal reports describing dramatic improvements in patients with drug-resistant epilepsies raised a growing interest among neurologists, epileptologists and families in using CBD as a new and safer AED. This need appears particularly compelling in those cases of so-called “catastrophic” infancy and childhood epileptic syndromes, such the above-mentioned MMPS, Dravet and Lennox–Gastaut syndromes. Since conventional AEDs for these disorders are often not helpful and rather toxic, a more favorable solution is strongly required, but evidence on the therapeutical potential of CBD in epilepsy is still weak. Although preclinical data suggest that CBD may be effective in the treatment of epilepsy, however, preliminary data from studies in humans are severely biased by many limitations since they are almost solely based on single cases or small series. Particularly, to date, there is great uncertainty about the different preparations, which may contain different percentages of CBD and THC, the optimal doses, the safety profile especially after long-term use, and the potential serious side-effects, such as impairment of neuropsychological functions, motor dysfunctions, psychiatric disorders, and risk of addiction [13]. 18

In conclusion, only double-blind, placebo-controlled, randomized clinical trials in which consistent preparations of CBD are used to treat patients with homogeneous and well-defined epileptic syndromes may provide reliable scientific and evidence-based information on efficacy and safety of CBD, in order to influence the current restrictive regulatory laws in many countries in the world and accelerate its legal use in clinical practice.

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Table 1. Clinical evidence of CBD treatment in epilepsy Study Type/Patients

Dose

Case report of a 10-month-old boy affected by malignant migrating partial seizures

25 mg/mL at 10 mg/kg/da y divided twice daily, up to 25 mg/kg/da y twice daily

Survey among parents (Facebook group) of children with several type of drug-resistant epilepsy

Survey among 117 parents of children affected by several type of pediatric resistant-epilepsy

Duratio n

Outcome

2 weeks

Seizure frequency reduction was reported

CBD from 0.5 mg/kg/da y up to 28.6 84% of mg/kg/da parents y, Treatmen reported a whereas t ranged decrease in the from 2 their child's dosages of weeks to seizure THC over one occurrences, present year 2 of them within became samples seizure-free ranged from 0 to 0.8 mg/kg/da y. 85% of parents described 4.3 6.8 reduction in mg/kg/da months seizure y (range = (range = occurrence, 2.9–7.5) 3.8–9.8) whereas 14% of parents

Other clinical benefits During the first week of treatment, the boy became more alert and has been able to maintain oral nutrition. After two weeks parents described him as “new baby”

Side effects

Ref s

No side effects

[76]

Improved alertness, better mood as well as restored quality of sleep were reported

Drowsiness and fatigue

[78]

Improved alertness and better mood were reported

Increased food intake

[80]

30

Retrospective case series, 75 children affected by resistant epilepsy, performed in Colorado

Retrospective study, 74 children with refractory epilepsy, in 5 Israeli pediatric clinics

Prospective/placeb o-controlled trial involving 15 patients (8 treated and 7 Placebo) affected by temporal lobe epilepsy with secondary generalized seizures

?

5.6 months (range: 1–24 months)

referred seizure freedom 57% referred improveme nt in seizures managemen t, whereas 33% of patients have attested a reduction of 50% of the seizures

Improved language, Increased enhanced seizures/new motor seizures onset, [81] performanc drowsiness/fatigu e and better e mood were reported

CBD from1 up to 20 mg/kg/da 89% Improved y, the described language, dosages of reduction in enhanced THC seizure At least 3 motor present occurrence, months performanc within 7% patients e and better samples referred mood were not exacerbatio reported exceed n of seizures 0.5 mg/kg/da y 50% became seizure-free, whereas 3 of 8 200-300 described 8-18 mg/ seizures weeks of ? Kg/day, reduction treatment per os and only 1 did not have antiseizure effects

Drowsiness, GI disturbances and irritability

[83]

Sleepiness

[84]

31

Prospective/placeb o-controlled trial involving 12 patients (6 treated and 6 Placebo) with uncontrolled seizures and intellectual disability

Prospective/placeb o-controlled trial involving 9 adults (4 treated and 5 placebo) with uncontrolled epilepsy

Prospectiverandomized/double -blind placebocontrolled trial involving 12 patients with resistant epilepsy

3 weeks

No significant difference in seizure between groups

?

Somnolence

[85]

200 mg/Kg/da y

3 months

2 of 4 became seizure-free 1 reported partial improveme nt in seizure frequency 1 did not show clinical benefit

?

No side effects was detected

[86]

300 mg/Kg/da y

12 patients were treated with a singleblind No statistics placebo were for 6 performed, months but a followed preliminary by review doublesuggested blind 300 that there mg of was not CBD or reduction in placebo seizure in a frequency crossover trial lasting an additiona l 12 months

None

Somnolence

[87]

200-300 mg/ Kg/day, per os

32

Multicentric open- 2-5 mg/kg label trial involving daily, The median 214 patients (aged until a Somnolence, reduction in 1-30 years) with dose of 25 decreased monthly Adequate severe, childhood- mg/kg or appetite, 12 weeks motor safety [90] onset, 50 mg/kg diarrhoea, seizures was profile pharmacoresistant per day fatigue, and 36·5% (IQR epilepsy (including (dependin convulsion 0-64·7) Dravet and g of the Lennox–Gastaut) study) ? = Not known or no details were provided; CBD= cannabidiol; GI = Gastrointestinal; THC: 9tetrahydrocannabinol

33