Use of the phytocannabinoid cannabidiol (CBD) in combination with a standard anti-epileptic drug (SAED) in the treatment of epilepsy

Abstract

The invention relates to the use of cannabidiol (CBD), at a dose of greater than 300 mg/day, in combination with a standard anti-epileptic drug (SAED) which acts via sodium or calcium channels, for use in the treatment of epilepsy. The SAED is preferably one which •modities low-threshold or transient neuronal calcium currents, or •reduces high-frequency neuronal firing and sodium-dependent action potentials and enhances GABA effects. Preferred SAEDs are ethosuximide and valproate.

Description

This Invention relates to the use of the phytocannabinoid cannabidiol (CBD) in combination with a standard anti-epileptic drug (SAED). Preferably the CBD is used in combination with a SAED with a mechanism of action which acts via sodium or calcium channels, more preferably one which:

• • modifies low-threshold or transient neuronal calcium currents, as exemplified by ethosuximide; or
  • reduces high-frequency neuronal firing and sodium-dependent action potentials and may additionally enhance GABA effects, as exemplified by valproate.

BACKGROUND

Epilepsy is a chronic neurological disorder presenting a wide spectrum of diseases that affect approximately 50 million people worldwide (Sander, 2003). Advances in the understanding of the body's internal ‘endocannabinoid’ system has lead to the suggestion that cannabis-based medicines may have the potential to treat this disorder of hyperexcitability in the central nervous system (Mackie, 2006, Wingerchuk, 2004, Alger, 2006).

Cannabis has been ascribed both pro-convulsant (Brust et al., 1992) and anti-convulsant effects. Therefore, it remains to determine whether cannabinoids represent a yet to be unmasked therapeutic anticonvulsant or, conversely, a potential risk factor to recreational and medicinal users of cannabis (Ferdinand et al., 2005).

In 1975 Consroe et al. described the case of young man whose standard treatment (phenobarbitol and phenytoin), didn't control his seizures. When he began to smoke cannabis socially he had no seizures. However when he took only cannabis the seizures returned. They concluded that ‘marihuana may possess an anti-convulsant effect in human epilepsy’.

A study by Ng (1990) involved a larger population of 308 epileptic patients who had been admitted to hospital after their first seizure. They were compared to a control population of 294 patients who had not had seizures, and it was found that using cannabis seemed to reduce the likelihood of having a seizure. However this study was criticized in an Institute of Medicine report (1999) which claimed it was ‘weak’, as ‘the study did not include measures of health status prior to hospital admissions and differences in their health status might have influenced their drug use’ rather than the other way round.

Three controlled trials have investigated the anti-epilepsy potential of cannabidiol. In each, cannabidiol was given in oral form to sufferers of generalised grand mal or focal seizures.

Cunha et al (1980) reported a study on 16 grand mal patients who were not doing well on conventional medication. They received their regular medication and either 200-300 mg of cannabidiol or a placebo. Of the patients who received CBD, 3 showed complete improvement, 2 partial, 2 minor, while 1 remained unchanged. The only unwanted effect was mild sedation. Of the patients who received the placebo, 1 improved and 7 remained unchanged.

Ames (1986) reported a less successful study in which 12 epileptic patients were given 200-300 mg of cannabidiol per day, in addition to standard antiepileptic drugs. There seemed to be no significant improvement in seizure frequency.

Trembly et al (1990) performed an open trial with a single patient who was given 900-1200 mg of cannabidiol a day for 10 months. Seizure frequency was markedly reduced in this single patient.

In addition to the disclosures suggesting CBD may be beneficial there is a report (Davis & Ramsey) of tetrahydrocannabinol (THC) being administered to 5 institutionalized children who were not responding to their standard treatment (phenobarbital and phenoytin). One became entirely free of seizures, one became almost completely free of seizures, and the other three did no worse than before.

In WO 2006/054057 it is suggested that the cannabinoid Tetrahydrocannabivarin (THCV) may behave as anti epileptic, something confirmed by Thomas et al 2005.

In addition WO 2009/007697 describes a THCV and CBD pharmaceutical formulation. Such a formulation is suggested to be of use in many different types of diseases including epilepsy.

However, there are more than forty recognisable types of epileptic syndrome partly due to seizure susceptibility varying from patient to patient (McCormick and Contreras, 2001, Lutz, 2004) and a challenge is finding drugs effective against these differing types.

Neuronal activity is a prerequisite for proper brain function. However, disturbing the excitatory—inhibitory equilibrium of neuronal activity may induce epileptic seizures. These epileptic seizures can be grouped into two basic categories:

• • a. Partial, and
  • b. Generalised seizures.Partial seizures originate in specific brain regions and remain localised—most commonly the temporal lobes (containing the hippocampus), whereas generalised seizures appear in the entire forebrain as a secondary generalisation of a partial seizure (McCormick and Contreras, 2001, Lutz, 2004). This concept of partial and generalised seizure classification did not become common practice until the International League Against Epilepsy published a classification scheme of epileptic seizures in 1969 (Merlis, 1970, Gastaut, 1970, Dreifuss et al., 1981).

The International League Against Epilepsy further classified partial seizures, separating them into simple and complex, depending on the presence or the impairment of a consciousness state (Dreifuss et al., 1981).

The league also categorized generalised seizures into numerous clinical seizure types, some examples of which are outlined below:

Absence seizures occur frequently, having a sudden onset and interruption of ongoing activities. Additionally, speech is slowed or impeded with seizures lasting only a few seconds (Dreifuss et al., 1981).

Tonic-clonic seizures, often known as “grand mal”, are the most frequently encountered of the generalised seizures (Dreifuss et al., 1981). This generalised seizure type has two stages: tonic muscle contractions which then give way to a clonic stage of convulsive movements. The patient remains unconscious throughout the seizure and for a variable period of time afterwards.

Atonic seizures, known as “drop attacks”, are the result of sudden loss of muscle tone to either a specific muscle, muscle group or all muscles in the body (Dreifuss et al., 1981).

The onset of epileptic seizures can be life threatening with sufferers also experiencing long-term health implications (Lutz, 2004). These implications may take many forms:

• • mental health problems (e.g. prevention of normal glutamatergic synapse development in childhood);
  • cognitive deficits (e.g. diminishing ability of neuronal circuits in the hippocampus to learn and store memories); and
  • morphological changes (e.g. selective loss of neurons in the CA1 and CA3 regions of the hippocampus in patients presenting mesial temporal lobe epilepsy as a result of excitotoxicity) (Swann, 2004, Avoll et al., 2005)

It is noteworthy that epilepsy also greatly affects the lifestyle of the sufferer—potentially living in fear of consequential injury (e.g. head injury) resulting from a grand mal seizure or the inability to perform daily tasks or the inability to drive a car unless having had a lengthy seizure-free period (Fisher et al., 2000).

There are many different standard anti-epileptic drugs available at the present time including: acetozolamide, carbamazepine, clobazam, clonazepam, ethosuximide, eslicarbazepine acetate, gabapentin, lacosamide, lamotriquine, levetiracetam, oxcarbazepine, Phenobarbital, phenytoin, pregabalin, primidone, rufinamide, sodium valproate, tiagabine, topiramate, valproate, vigabatrin, and zonisamide.

The mode of action of some of these is understood and for others is unknown. Some modes of action are set out in Table 1 below: (Adapted from: Schachter S C. Treatment of seizures. In: Schachter S C, Schomer D L, eds. The comprehensive evaluation and treatment of epilepsy. San Diego, CA: Academic Press; 1997. p. 61-74)

TABLE 1
		Sodium
		or calcium
		channel
Antiepileptic drug	Mechanism of action	involvement
Barbiturates: primidone	Enhances GABAergic
(Mysoline), phenobarbital	inhibition
Carbamazepine (Tegretol,	Inhibits voltage-dependent	Sodium
Tegretol-XR, Carbatrol)	sodium channels
Ethosuximide (Zarontin)	Modifies low-threshold or	Calcium
	transient neuronal calcium
	currents
Felbamate (Felbatol)	Unknown
Gabapentin (Neurontin)	Unknown
Lamotrigine (Lamictal)	Inhibits voltage-dependent	Sodium
	sodium channels, resulting
	in decreased release of the
	excitatory neurotransmitters
	glutamate and aspartate
Phenytoin (Dilantin,	Blocks sodium-dependent	Sodium/
Phenytek)	action potentials; reduces	Calcium
	neuronal calcium uptake
Valproate (Depakote,	Reduces high-frequency	Sodium
Depakote ER, Depakene,	neuronal firing and sodium-
valproic acid)	dependent action potentials;
	enhances GABA effects

Three well-established and extensively used in vivo mode is of epilepsy are:

• • pentylenetetrazole-induced (PTZ) model of generalised seizures (Obay et al., 2007, Rauca et al., 2004);
  • pilocarpine-induced model of temporal lobe (i.e. hippocampus) seizures (Pereira et al., 2007); and
  • penicillin-induced model of partial seizures (Bostanci and Bagirici, 2006).These provide a range of seizure and epilepsy models, essential for therapeutic research in humans.

The application WO 02/064109 describes a pharmaceutical formulation where the cannabinoids THC and CBD are used. The application goes on to state that the propyl analogs of these cannabinoids may also be used in the formulation. Since this application was written it has been shown that THCV behaves in a very different manner to THC and therefore the assumption that the propyl analogs of cannabinoids behave in a similar manner to their pentyl counterparts is now not valid.

The application GB0911580.9 describes the use of THCV for the treatment of generalised seizures, also described is the use of the cannabinoid CBD in combination with the THCV.

It is an object of the present invention to identify novel drug combinations which will enhance or otherwise offer benefits in the use of SAED's. The use of a combination may allow for lower doses of SAED's to be used then is conventional.

BRIEF SUMMARY OF THE DISCLOSURE

In accordance with a first aspect of the present invention there is provided cannabidiol, (CBD), at a dose of greater than 300 mg/day, in combination with a standard anti-epileptic drug (SAED) which acts via sodium or calcium channels, for use in the treatment of epilepsy.

The SAED which acts via sodium or calcium channels may be exemplified by a drug which:

• • modifies low-threshold or transient neuronal calcium currents, such as, ethosuximide; or
  • reduces high-frequency neuronal firing and sodium-dependent action potentials (and may additionally enhance GABA effects), such as, valproate;In contrast, a SAED which (solely) enhances GABAergic inhibition (as opposed to acting via sodium or calcium channels), such as, phenobarbital, does not appear to provide benefits in combination with CBD, when tested in a pilocarpine model. Thus, the selective benefits of CBD with e.g. ethosuximide and valporate (SAED's with defined and distinct mechanisms of actions involving calcium and sodium channels) could not be anticipated.

In accordance with a second aspect of the present invention there is provided the use of cannabidiol (CBD), at a dose of greater than 300 mg/day, in combination with a standard anti-epileptic drug (SAED) which acts via sodium or calcium channels, in the manufacture of a medicament for use in the treatment of epilepsy.

In accordance with a third aspect of the present invention there is provided a method for the treatment of epilepsy, which comprises administering to a subject in need thereof cannabidiol (CBD), at a dose of greater than 300 mg/day, in combination with a standard anti-epileptic drug (SAED) which acts via sodium or calcium channels.

In accordance with a forth aspect of the present invention there is provided a combination product comprising cannabidiol (CBD), at a dose of greater than 300 mg/day, and a standard anti-epileptic drug (SAED) which acts via sodium or calcium channels.

The respective drugs may be packaged separately with instructions to be taken in combination or may be formulated as a single use product.

Preferably the standard anti-epileptic drug acting via sodium or calcium channels is taken from the group consisting of: ethosuximide and valproate.

Preferably the type of epilepsy to be treated is a generalised seizure or a temporal lobe seizure.

The combination may prove beneficial in one or more of the following:

• • a. reducing the incidence of tonic-clonic seizures;
  • b. Increasing the amount of time a patient is seizure free;
  • c. increasing the latency to onset of seizure;
  • d. decreasing the overall duration of the seizure; and
  • e. reducing the severity and mortality of the seizures.Thus, the combinations are particularly well suited in the treatment of conditions generally considered refractory to existing medication. The combinations would also appear to allow for the use of lower doses of the SAED's than would be used were the SAED to be used alone.

In one embodiment the CBD is used with one or more therapeutically effective other phytocannabinoid(s).

Preferably the one or more therapeutically effective other phytocannabinoid is THCV and/or CBDV.

In one embodiment the CBD is in an isolated form.

In a further embodiment the CBD is in the form of a botanical drug substance.

BRIEF DESCRIPTION OF THE DRAWINGS

By way of example only, a number of embodiments of the invention are described hereinafter with reference to the accompanying drawings, in which

FIG. 1 A-C shows the effect of CBD at 100 mg/kg in combination with valproate on PTZ-induced seizures;

FIG. 2 A-C shows the effect of CBD and valproate on latency, duration and severity of PTZ-induced seizures;

FIG. 3 A-C shows the effect of CBD at 100 mg/kg and ethosuximide on PTZ-induced seizures;

FIG. 4 A-C shows the anti-convulsant effects of 100 mg/kg CBD in combination with valproate on the development of pilocarpine-induced seizures; and

FIG. 5 A-C shows the effect of 100 mg/kg CBD in combination with valproate on the development of pilocarpine-induced seizure and mortality incidence.

Legend to FIG. 1: A: % mortality with (black bars) and without 100 mg/kg CBD (white bars). B: % seizure free with (black bars) and without 100 mg/kg CBD (white bars). C: % of animals that developed the most severe (tonic-clonic) seizures with (black bars) and without 100 mg/kg CBD (white bars).

Legend to FIG. 2: A: latency to seizure onset; B: duration of seizure activity of those animals that survived; C: median seizure severity.

Legend to FIG. 3: A: latency to onset of seizures at different doses of ethosuximide without (black) or with (grey unfilled) 100 mg/kg CBD. B: Seizure severity. C: Percentage mortalities, key as in A.

Legend to FIG. 4: Mean latency to onset (A). development of bilateral seizures (B) and tonic-clonic seizures (C).

Legend to FIG. 5: A: Proportion (%) of animals in each dose group that exhibited fully developed tonic-clonic seizures. B: Proportion (%) of animals in each dose group that died. C: Proportion (%) of animals in each dose group that were seizure free.

DETAILED DESCRIPTION

The examples below describe the use of isolated CBD in combination with standard anti-epileptic drugs (SAEDs) in two different models of epilepsy, namely the PTZ-induced seizure model and the pilocarpine-induced seizure model. The SAEDs used in these examples are ethosuximide, valproate and Phenobarbital (Pilocarpine model only). It is important to note that there are many different SAEDs available and the drugs chosen for these experiments provide a general overview of how the phytocannabinoid CBD is able to work in combination with different classes of drugs used in the treatment of epilepsy.

Example 1

The Use of the Phytocannabinoid CBD in Combination with a Standard Anti-Epileptic Drug (SAED) in the PTZ-Model of Epilepsy

Methodology:

Animals:

Male Wistar rats (P24-29; 75-110 g) were used to assess the effects of the phytocannabinoid CBD in combination with SAEDs in the PTZ model of generalised seizures. Animals were habituated to the test environment, cages, injection protocol and handling prior to experimentation. Animals were housed in a room at 21° C. on a 12 hour light: dark cycle (lights on 0900) in 50% humidity, with free access to food and water.

The human dose equivalent (HED) can be estimated using the following formula:

$HED=\mathrm{Animal}\mathrm{dose}\left(\mathrm{mg}/\mathrm{kg}\right)\mathrm{multiplied}\mathrm{by}\frac{\mathrm{Animal}{K}_m}{\mathrm{Human}{K}_m}$ The K_m for a rat is 6 and the K_m for a human is 37.Thus, for a human of approx 60 Kg a 100 mg/Kg dose in rat would equate to a human dose of about 1000 mg. Human doses of greater than 300 mg/day, through 400 mg/day in 100 mg intervals (namely through 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300 and 1400 mg) to as much as 2000 mg/day are envisaged based on dose escalating studies with CBD (Example 2).Experimental Setup:

Five 6 L Perspex tanks with lids were placed on a single bench with dividers between them. Closed-circuit television (CCTV) cameras were mounted onto the dividers to observe rat behaviour. Sony Topica CCD cameras (Bluecherry, USA) were linked via BNC cables to a low-noise PC via Brooktree digital capture cards (Bluecherry, USA). Zoneminder (http://www.zoneminder.com) software was used to monitor rats, start and end recordings and manage video files. In-house Linux scripts were used to encode video files into a suitable format for further offline analysis using The Observer (Noldus Technologies).

PTZ Model:

A range of doses of PTZ (50-100 mg/kg body weight) were used to determine the best dose for induction of seizures (data not shown). As a result, a dose of 80 mg/kg injected intra-peritoneally (IP; stock solution 50 mg/ml in 0.9% saline) were used to screen the CBD/SAEDs combinations.

Experimental Protocols

On the day of testing, isolated CBD was administered via intra-peritoneal (i.p.) injection at a dose of 100 mg/kg alongside animals that were injected with a matched volume of the cannabinoid vehicle (2:1:17 ethanol:Cremophor: 0.9% w/v NaCl solution), which served as the negative control group. Animals were then observed for 1 hour, after which time they received an IP injection of 80 mg/kg PTZ. Negative vehicle controls were performed in parallel with cannabinoid-dosed subjects. After receiving a dose of PTZ, animals were observed and videoed to determine the severity of seizure and latency to several seizure behaviour types (see In vivo analysis, below). Animals were filmed for half an hour after last sign of seizure, and then returned to their cage.

In Vivo Analysis:

Animals were observed during experimental procedures, but all analysis was performed offline on recorded video files using The Observer behavioural analysis software (Noldus, Netherlands). A seizure severity scoring system was used to determine the levels of seizure experienced by subjects (Pohl & Mares, 1987). All signs of seizure were detailed for all animals.

TABLE 1.1
Seizure severity scoring scale, adapted from Pohl & Mares, 1987.
Seizure score	Behavioural expression	Righting reflex
0	No changes to behaviour	Preserved
0.5	Abnormal behaviour (sniffing, excessive	Preserved
	washing, orientation)
1	Isolated myoclonic jerks	Preserved
2	Atypical clonic seizure	Preserved
3	Fully developed bilateral forelimb clonus	Preserved
3.5	Forelimb clonus with tonic component	Preserved
	and body twist
4	Tonic-clonic seizure with suppressed	Lost
	tonic phase
5	Fully developed tonic-clonic seizure	Lost
6	Death

Latency from injection of PTZ to Specific Indicators of Seizure Development:

The latency (in seconds) from injection of PTZ to first myoclonic jerk (FMJ; score of 1), and to the animal attaining “forelimb clonus with tonic component and body twist” (score of 3.5) were recorded. FMJ is an indicator of the onset of seizure activity, whilst >90% of animals developed scores of 3.5, and so is a good marker of the development of more severe seizures. Data are presented as the mean±S.E.M. within an experimental group.

Maximum Seizure Severity:

This is given as the median value for each experimental group based on the scoring scale below.

Percentage Mortality:

The percentage of animals within an experimental group that died as a result of PTZ-induced seizures. Note that the majority of animals that developed tonic-clonic seizures (scores of 4 and 5) died as a result, and that a score of 6 (death) automatically denotes that the animal also experienced tonic-clonic seizures.

Seizure Duration:

The time (in seconds) from the first sign of seizure (typically FMJ) to either the last sign of seizure or, in the case of subjects that died, the time of death—separated into animals that survived and those that did not. This is given as the mean f S.E.M. for each experimental group.

Statistics

For measures of latency and severity, one way analysis of variance (ANOVA) was performed on the test groups to detect overall combinational effects of CBD and SAEDs (p≤0.05 considered significant).

Significant ANOVA results were followed by post hoc tests to test differences between vehicle and drug groups (Tukey's test, p≤0.05 considered significant).

Results

From FIG. 1 it can be seen that the addition of CBD to the SAED valproate has an effect on reducing the percentage mortality and the incidence of tonic-clonic seizures. It is also shown that the combination of CBD and the higher dose of valproate is more effective at increasing the amount of time that the animal was seizure free.

FIG. 2 demonstrates that the combination of CBD and valproate was able to increase the latency to onset of seizure at all dose ranges, in addition it decreased the overall duration of the seizure.

The data shown in FIG. 3 demonstrates that the combination of CBD with the SAED ethosuximide was also effective at reducing the severity and mortality of the seizures. It also at the higher dose of ethosuximide was able to increase the latency to onset of the seizures.

Conclusion

The data demonstrated in this Example clearly shows that the combination of CBD with a SAED which has a mechanism of action involving sodium or calcium channels is of value when treating generalised seizures.

Example 2

The Use of the Phytocannabinoid CBD in Combination with a Standard Anti-Epileptic Drug (SAED) in the Pilocarpine Model of (Temporal Lobe) Epilepsy

Methodology

Isolated CBD was injected intra-peritoneally (IP) in the standard vehicle (1:1:18 ethanol:Cremophor:0.9% w/v NaCl) at doses of 50, 100 and 200 mg/kg alongside animals that received vehicle alone at a matched volume. 15 minutes later methylscopolamine (1 mg/kg; to reduce peripheral muscarinic effects of pilocarpine) was administered followed, 45 minutes later by pilocarpine (380 mg/kg, IP) administration.

Results

FIG. 4 demonstrates the anti-convulsant effects of a combination of CBD and valproate in the pilocarpine model of epilepsy. These data show that the combination of the CBD and valproate was able to increase the latency of onset of the seizure.

It can be seen from the data illustrated in FIG. 5 that in addition to increasing the latency of onset of the seizure the combination of CBD and valproate was able to decrease mortality and the percentage of tonic-clonic seizures.

Table 2.1 below describes the data in more detail.

TABLE 2.1
Anti-convulsant effects of CBD and valproate
in the pilocarpine model of epilepsy
				CBD in
				Combination
				with
		CBD	Valproate	Valproate
	Seizure Measure	Effects	Effects	Effects
ALL	Mean number of episodes		**	#
EPI-	Mean time spent in		*
SODES	episodes
	Mean duration of		*
	episodes
	Mean severity of episodes	*	**
	Percentage ≥3 episodes		#
	Percentage episode free		**
EPI-	Latency		**
SODE 1	Duration
	Severity		*
EPI-	Latency		#
SODE 2	Duration		#
	Severity	*
Key: # = p < 0.01;
* = p < 0.05;
** = p < 0.01

The table above clearly shows some of the advantages of using a combination of the two compounds.

Table 2.2 below describes the effect of using the phytocannabinoid CBD in combination with yet a further SAED, phenobarbital, in the pilocarpine model of epilepsy.

TABLE 2.2
Effects of CBD and phenobarbital on
the pilocarpine model of epilepsy
CBD	Phenobarbitol
(mg/kg)	(mg/kg)	Seizure free (%)	Onset latency (s)
0	0	0	750
100	0	0	500
0	10	25	800
100	10	25	750
0	20	55	900
100	20	55	930
0	40	75	1800
100	40	85	900

In contrast to the valproate combination data, this result demonstrate the selective nature of the combinations which is likely attributed to the different mechanisms of actions of these SAED's.

OVERALL CONCLUSION

The data demonstrated in the above Examples shows that the combination of CBD with standard anti-epileptic drugs acting via sodium or calcium channels may be beneficial in the treatment of different types of epilepsy. This finding is of great significance to the many epilepsy sufferers whose condition is refractory to existing medication.

Claims

1. A method for treating epilepsy in a subject in need thereof, comprising: administering to the subject cannabidiol (CBD), at a dose of greater than 300 mg/day, in combination with valproate.

2. The method of claim 1, wherein the epilepsy is a generalized seizure or a temporal lobe seizure.

3. The method of claim 1, wherein the epilepsy is refractory to existing medication.

4. The method of claim 1, wherein the CBD is administered with one or more other therapeutically effective phytocannabinoids.

5. The method of claim 4, wherein the one or more other therapeutically effective phytocannabinoids is THCV and/or CBDV.

6. The method of claim 1, wherein the CBD is an isolated phytocannabinoid.

7. The method of claim 1, wherein the CBD is in a form of a botanical drug substance.

8. The method of claim 1, wherein CBD and valproate are administered in a ratio of valproate to CBD of at least 1:1.

9. The method of claim 1, wherein CBD and valproate are administered in a ratio of valproate to CBD of no more than 3.5:1.

10. The method of claim 1, wherein CBD and valproate are administered in a ratio of valproate to CBD in the range of 3.5:1 to 1:1.

11. The method of claim 1, wherein the administration of CBD and valproate results in a lower percentage of tonic-clonic seizures compared to the administration of either CBD or valproate alone.

12. The method of claim 1, wherein the administration of CBD and valproate results to a patient population results in a higher percentage of seizure-free patients compared to the administration of either CBD or valproate alone.