This application claims priority of U.S. Provisional Application No. 61/783,730, filed March 14, 2013, U.S. Provisional Application No. 61/625,192, filed April 17, 2012, and U.S. Provisional Application No. 61/620,203, filed April 4, 2012, the entire contents of which are hereby incorporated by reference herein. Throughout this application, various publications are referred to, and disclosures of these publications cited in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art as of the date of the invention described herein.

BACKGROUND OF THE INVENTION

Pridopidine, i.e. 4- (3-Methanesulfonyl-phenyl) -1- propyl-piperidine, is a drug substance currently in clinical development for the treatment of Huntington's disease. This compound was first described in WO 01/46145.

Pridopidine is a dopaminergic stabilizer that displays competitive dopamine D2 receptor antagonism with fast dissociation kinetics (Dyhring, 2010) . In vivo

Pridopidine increases turnover and release of dopamine in the striatum and in the frontal cortex (Poten, 2010; Pettersson

2010) . Behavioural effects include antagonism of psychostimulant induced hyperactivity, suggesting antipsychotic properties, but no inhibitory effects on spontaneous locomotor activity (Ponten, 2010; Natesan 2006;

Nilsson, 2004) .

Tetrabenzine, i.e. {SS, RR) -3-Isobutyl-9, 10-dimethoxy-

1,3,4,6,7,llb-hexahydro-pyrido[2,l-a]isoquinolin-2-one, is a drug substance marketed for the symptomatic treatment of certain movement disorders (FDA Label for XENAZINE (Tetrabenzine) 07/06/2011) . Tetrabenazine, is an inhibitor of the vesicular monoamine transporter type 2 (VMAT) , that blocks the vesicular storage of monoamine neurotransmitters in the brain, thereby leading to reduced synaptic release of dopamine, serotonin and norepinephrin (Paleacu, 2007) . This reduction of monoaminergic neurotransmission is associated with suppression ^* of e.g. dopamine dependent functions, including movement -and reward. The suppression of movements is used therapeutically to ameliorate involuntary movements in e.g. Huntington's disease, tardive dyskinesia, and Tourette's disease. However, treatment with Tetrabenazine is associated with severe side effects. Such side effects include parkinsonism, i.e. rigidity and impaired motor function, depression, and impaired functional capacity.

Involuntary movements such as chorea and dyskinesia, occurring as part of the clinical manifestations of e.g. Huntington's disease, are believed to be related to impaired activity in the indirect cortico-striato-thalamic pathway. Hence, the beneficial effects of Tetrabenazine on such involuntary movements are due to a decreased tone at dopamine D2 receptors on medium spiny neurons of the indirect pathway, occurring as a consequence of the reduction in dopamine transmission engendered by Tetrabenazine. The decreased dopamine D2 receptor tone leads to a reduced inhibition of these medium spiny neurons, and therefore, an increased activity of the indirect pathway, and improved suppression of involuntary movements. Accordingly, dopamine D2 antagonists are also frequently used to alleviate chorea in HD (Steward 2001) . Combination Therapy

The administration of two drugs to treat a given condition, such as a movement disorder, raises a number of potential problems. In vivo interactions between two drugs are complex. The effects of any single drug are related to its absorption, distribution, and elimination. When two drugs are introduced into the body, each drug can affect the absorption, distribution, and elimination of the other and hence, alter the effects of the other. For instance, one drug may inhibit, activate or induce the production of enzymes involved in a metabolic route of elimination of the other drug (Guidance for

Industry, 1999). In one example, combined administration of GA and interferon (IFN) has been experimentally shown to abrogate the clinical effectiveness of either therapy. (Brod 2000) In another experiment, it was reported that the addition of prednisone in combination therapy with IFN-β antagonized its up- egulator effect. Thus, when two drugs are administered to treat the same condition, it is unpredictable whether each will complement, have no effect on, or interfere with, the therapeutic activity of the other in a human subject.

Not only may the interaction between two drugs affect the intended therapeutic activity of each drug, but the interaction may increase the levels of toxic metabolites (Guidance for Industry, 1999) . The interaction may also heighten or lessen the side effects of each drug. Hence, upon administration of two drugs to treat a disease, it is unpredictable what change will occur in the negative side profile of each drug. In one example, the combination of natalizumab and interferon β-la was observed to increase the risk of unanticipated side effects. (Vollmer, 2008; Rudick 2006; Kleinschmidt-DeMasters, 2005; Langer-Gould 2005)

Additionally, it is difficult to accurately predict when the effects of the interaction between the two drugs will become manifest. For example, metabolic interactions between drugs may became apparent upon the initial administration of the second drug, after the two have reached a steady-state concentration or upon discontinuation of one of the drugs (Guidance for Industry, 1999).

Therefore, the state of the art at the time of filing is that the effects of combination therapy of two drugs, in particular Pridopidine and Tetrabenazine, cannot be predicted until the results of combination studies are available.

BRIEF SUMMARY OF THE INVENTION

It has now surprisingly been found that Pridopidine is capable of reversing the behavioural inhibition caused by Tetrabenazine, while maintaining the primary pharmacological effect of Pridopidine, i.e. dopamine D2 receptor blockade. These findings suggest that coadministration of Pridopidine and Tetrabenazine would improve the therapeutically beneficial effects of Tetrabenazine, i.e. further alleviate involuntary movements, as well as reduced the adverse motor and affective effects.

The subject invention provides a method of treating a subject afflicted with a movement disorder comprising periodically administering to the subject an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof, and an amount of Pridopidine or a pharmaceutically acceptable salt thereof.

The subject invention also provides a method of treating a subject afflicted with obesity, an obesity associated disorder, or a cardiovascular side effect of Pridopidine comprising administering to the subject an amount of Pridopidine or a pharmaceutically acceptable salt thereof, and an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof.

The subject invention also provides a method of reducing or preventing one or more side effects of periodically administering of an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof to a subject, comprising periodically administering to the subject an amount of Pridopidine or a pharmaceutically acceptable salt thereof.

The subject invention also provides a package comprising: a) a first pharmaceutical composition comprising an amount of Tetrabenazine or a pharmaceutically ac-ceptable salt thereof and a pharmaceutically ac-ceptable carrier;

b) a second pharmaceutical composition comprising and amount of Pridopidine or pharmaceutical acceptable salt thereof and a pharmaceutically acceptable carrier; and

c) instruction for use for the first and the second pharmaceutical compositions together to treat a subject afflicted a movement disorder.

The subject invention also provides Pridopidine or pharmaceutically acceptable salt thereof for use as an add-on therapy of or in combination with Tetrabenazine or pharmaceutical acceptable salt thereof in treating a subject afflicted with a movement disorder.

The subject invention also provides a pharmaceutical composition comprising an amount of Tetrabenazine or pharmaceutically acceptable salt thereof, an amount of Pridopidine or pharmaceutical acceptable salt thereof, and at least one pharmaceutical acceptable carrier.

The subject invention also provides the use of:

a) an amount of Tetrabenazine or pharmaceutically acceptable salt thereof; and

b) an amount of Pridopidine or pharmaceutically acceptable salt thereof

in the preparation of a combination for treating a subject afflicted with a movement disorder wherein the amount of Tetrabenazine or pharmaceutically acceptable salt thereof and the amount of Pridopidine or pharmaceutically acceptable salt thereof are administered simultaneously or contemporaneously.

The subject invention also provides a pharmaceutical composition comprising an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof for use in treating a subject afflicted with a movement disorder, in combination with an amount of Pridopidine or pharmaceutically acceptable salt thereof, by periodically administering to the subject the pharmaceutical composition and the amount of Pridopidine or pharmaceutically acceptable salt thereof.

The subject invention also provides a pharmaceutical composition comprising an amount of Pridopidine or pharmaceutically acceptable salt thereof for use treating a subject afflicted with a movement disorder, in combination with an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof, by periodically administering to the subject the pharmaceutical composition and the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof.

The subject invention also provides Tetrabenazine or a pharmaceutically acceptable salt thereof and Pridopidine or a pharmaceutically acceptable salt thereof for the treatment of a subject afflicted with a movement disorder, wherein the Tetrabenazine or a pharmaceutically acceptable salt thereof and the Pridopidine or a pharmaceutically acceptable salt thereof are administered simultaneously, separately or sequentially.

The subject invention also provides a product containing an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof and an amount of Pridopidine or a pharmaceutically acceptable salt thereof for simultaneous, separate or sequential use in treating a subject afflicted with a movement disorder.

The subject invention also provides a method of treating a subject afflicted with obesity, an obesity associated disorder or a cardiovascular side effect of Pridopidine comprising administering to the subject a combination of a therapeutically effective amount of Pridopidine or a pharmaceutically acceptable salt thereof, and a therapeutically effective amount of Tetrabenazine or a pharmaceutically acceptable salt thereof, wherein the amounts when taken together are effective to treat the subject.

The subject invention also provides a combination of Pridopidine, or a pharmaceutically acceptable salt thereof; and Tetrabenazine, or a pharmaceutically acceptable salt thereof; for the treatment, prevention or alleviation of obesity, or an obesity associated disorder, and for treatment, prevention or alleviation of the cardiovascular side effects of Pridopidine, in a mammal, including a human.

In another aspect, the invention provides a combination of Pridopidine, or a pharmaceutically acceptable salt thereof, and Tetrabenazine. or a pharmaceutically acceptable salt thereof, for use as a medicament for the treatment, prevention or alleviation of a movement disorder.

in another aspect the invention provides a combination of Pridopidine, or a pharmaceutically acceptable salt thereof, and Tetrabenazine, or a pharmaceutically acceptable salt thereof, for use as a medicament.

In another aspect the invention provides a combination of Pridopidine, or a pharmaceutically acceptable salt thereof; and Tetrabenazine, or a pharmaceutically acceptable salt thereof; for the treatment, prevention or alleviation of obesity, or an obesity associated disorder, and for treatment, prevention or alleviation of the cardiovascular side effects of Pridopidine, in a mammal, including a human.

In another aspect the invention relates to the use of a combination of Pridopidine, or a pharmaceutically acceptable salt thereof; and Tetrabenazine, or a pharmaceutically acceptable salt thereof; for the manufacture of a medicament for the treatment, prevention or alleviation of a movement disorder of a mammal, including a human.

In another aspect the invention provides a pharmaceutical composition comprising Pridopidine, or a pharmaceutically acceptable salt thereof, for use in a combination therapy together with a pharmaceutical composition comprising Tetrabenazine, or a pharmaceutically acceptable salt thereof, for the treatment, prevention or alleviation of a movement disorder.

In another aspect the invention provides a pharmaceutical composition comprising a therapeutically effective amount of Pridopidine, or a pharmaceutically acceptable salt thereof, and a therapeutically effective amount of Tetrabenazine, or a pharmaceutically acceptable salt thereof, together with one or more adjuvants, excipients, carriers and/or diluents.

In another aspect the invention provides a method of treatment, prevention or alleviation of a movement disorder in a living animal body, including a human, which method comprises the step of administering to such a living animal body in need thereof, a therapeutically effective amount of Pridopidine, or a pharmaceutically acceptable salt thereof; in a combination therapy with Tetrabenazine, or a pharmaceutically acceptable salt thereof.

In another aspect the invention provides a kit of parts comprising at least two separate unit dosage forms (A) and (B) , wherein (A) comprises Pridopidine, or a pharmaceutically acceptable salt thereof; and (B) comprises Tetrabenazine, or a pharmaceutically acceptable salt thereof; and optionally (C) instructions for the simultaneous, sequential or separate administration of the Pridopidine of (A) and the Tetrabenazine of (B) , to a patient in need thereof .

in another aspect the invention provides an article of manufacture, comprising (A) a first pharmaceutical dosage form comprising Pridopidine, or a pharmaceutically acceptable salt thereof; and (B) a second pharmaceutical dosage form comprising Tetrabenazine, or a pharmaceutically acceptable salt thereof; wherein the article contains first and second pharmaceutical dosage forms.

In another aspect the invention provides a method of treating a subject afflicted with a movement disorder comprising administering to the subject a combination of a therapeutically effective amount of Pridopidine or a pharmaceutically acceptable salt thereof, and a therapeutically effective amount of Tetrabenazine or a pharmaceutically acceptable salt thereof, wherein the amounts when taken together are effective to treat the human patient.

In another aspect the invention provides a method of treating a mammal, including a human, afflicted with an obesity, or an obesity associated disorder or of the cardiovascular side effects of Pridopidine comprising administering to the subject a combination of a therapeutically effective amount of Pridopidine or a pharmaceutically acceptable salt thereof, and a therapeutically effective amount of Tetrabenazine or a pharmaceutically acceptable salt thereof, wherein the amounts when taken together are effective to treat the mammal.

Other objects of the invention will be apparent to the person skilled in the art from the following detailed description and examples.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The present invention is further illustrated by reference to the accompanying drawings.

Fig. 1. Spontaneous locomotor activity (LMA) expressed as a percentage of the mean control group value for Tetrabenazine. Activity is shown by dose for each recorded time period. Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle (Glucose 5.5% v/w) and Tetrabenazine tested at three doses (0.37; 0.64 and 1.1 umol/kg) . All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 2. The effect of Tetrabenazine on striatal DOPAC (3,4-Dihydroxyphenylacetic acid). Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of vehicle (Glucose 5.5% v/w) and Tetrabenazine tested at three doses (0.37; 0.64 and 1.1 umol/kg). All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 3. Arc gene expression (Arc mRNA levels or Arc) expressed as a percentage of the mean control group value, following treatment with Tetrabenazine. Expression is shown by dose and by region (striatal arc (arcs) or frontal cortex arc (arcF) ) . Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle (Glucose 5.5% v/w) and Tetrabenazine tested at three doses (0.37; 0.64 and 1.1 umol/kg). All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 4. Spontaneous locomotor activity expressed as a percentage of the mean control group value for Pridopidine. Activity is shown by dose for each recorded time period. Animals were allocated into four different treatment groups, n=5. The treatment groups consisted of Vehicle (saline; NaCl 0.9% v/w) and Pridopidine tested at three doses (11; 33 and 100 umol/kg) . All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 5. The effect of Pridopidine (NS30016) on striatal DOPAC. Animals were allocated into four different treatment groups, n=5. The treatment groups consisted of Vehicle (saline; NaCl 0.9% v/w) and Pridopidine tested at three doses (11; 33 and 100 umol/kg) . All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 6. Arc gene expression expressed as a percentage of the mean control group value, following treatment with Pridopidine. Expression is shown by dose and by region (striatal arc (arcs) or frontal cortex arc (arcF) ) . Animals were allocated into four different treatment groups, n=5. The treatment groups consisted of Vehicle (saline; NaCl 0.9% v/w) and Pridopidine tested at three doses (11; 33 and 100 umol/kg). All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 7. Spontaneous locomotor activity expressed as a percentage of the mean control group value for haloperidol. Activity is shown by dose for each recorded time period. Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle (Glucose 5.5% v/w) and Haloperidol tested at three doses (0.12; 0.37 and 1.1 umol/kg) . All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 8. Spontaneous locomotor activity expressed as a percentage of the mean control group value for haloperidol. Animals were allocated into five different treatment groups, n = 4. The treatment groups consisted of Vehicle (Glucose 5.5% v/w) and Haloperidol tested at four doses (0.04; 0.12; 0.37 and 1.1 umol/kg). All compounds were injected e.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 9. The effect of Haloperidol on striatal DOPAC. Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle (Glucose 5.5% v/w) and Haloperidol tested at three doses (0.12; 0.37 and 1.1 umol/kg). All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 10 Arc gene expression expressed as a percentage of the mean control group value, following treatment with haloperidol. Expression is shown by dose and by region (striatal arc (arcs) or frontal cortex arc (arcF)). Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle (Glucose 5.5% v/w) and Haloperidol tested at three doses (0.12; 0.37 and 1.1 umol/kg) . All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 11. Spontaneous locomotor activity expressed as a percentage of the mean control group value for Tetrabenazine + Pridopidine. Activity is shown by dose for each recorded time period. This experiment was completed in one of two ways: (1) "Process BS81* in which the animals were allocated into four different treatment groups, n = 5, the treatment groups consisted of vehicle 1:1 (saline; NaCl 0.9% v/w+ 5.5% glukos with a few drops of HAc) the second group consisted of a single dose of Tetrabenazine (0.64 mg/kg) and the third and fourth groups consisted of Pridopidine tested in two doses (33 and 100 umol/kg together with Tetrabenazine in one dose (0.64 mg/kg) or (2) "Process TA284" in which the animals were allocated into four different treatment groups, n = 10, the treatment groups consisted of vehicle 1:1 (saline; NaCl 0.9% v/w+ 5.5% glukos with a few drops of HAc) the second group consisted of a single dose of Tetrabenazine (0.64 mg/kg) and the third and fourth groups consisted of Pridopidine tested in two doses (33 and 100 umol/kg together with Tetrabenazine in one dose (0.64 mg/kg). No brain tissue was collected from this experiment. All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 12. The effect of Pridopidine on Tetrabenazine induced striatal dopamine increase. Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle 1:1 (saline; NaCl 0.9% v/w+ 5.5% glukos with a few drops of HAc) the second group consisted of a single dose of Tetrabenazine (0.64 mg/kg) and the third and fourth groups consisted of Pridopidine (NS30016) tested in two doses (33 and 100 umol/kg together with Tetrabenazine in one dose (0.64 mg/kg). All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 13. Arc gene expression expressed as a percentage of the mean control group value, following treatment with Tetrabenazine + Pridopidine. Expression is shown by dose and by region (striatal arc (arcS) or frontal cortex arc (arcF) ) . Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle 1:1 (saline; NaCl 0.9% v/w+ 5.5% glukos with a few drops of HAc) the second group consisted of a single dose of Tetrabenazine (0.64 mg/kg) and the third and fourth groups consisted of Pridopidine tested in two doses (33 and 100 umol/kg together with Tetrabenazine in one dose (0.64 mg/kg All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 14. Spontaneous locomotor activity expressed as a percentage of the mean control group value for Tetrabenazine + haloperidol . Activity is shown by dose for each recorded time period. Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle 1:1 (saline; NaCl 0.9% v/w+ 5.5% glukos with a few drops of HAc) the second group consisted of a single dose of Tetrabenazine (0.64 mg/kg) and the third and fourth groups consisted of Haloperidol tested in two doses (0.04 and 0.12 mg/kg together with Tetrabenazine in one dose (0.64 mg/kg). All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 15. The effect of Haloperidol on Tetrabenazine induced striatal dopamine increase. Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle 1:1 (saline; NaCl 0.9% v/w+ 5.5% glukos with a few drops of HAc) the second group consisted of a single dose of Tetrabenazine (0.64 mg/kg) and the third and fourth groups consisted of Haloperidol tested in two doses (0.04 and 0.12 mg/kg together with Tetrabenazine in one dose (0.64 mg/kg). All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

Fig. 16. Arc gene expression expressed as a percentage of the mean control group value, following treatment with Tetrabenazine + haloperidol. Expression is shown by dose and by region (striatal arc (arcs) or frontal cortex arc (arcF) ) . Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle 1:1 (saline; NaCl 0.9% v/w+ 5.5% glukos with a few drops of HAc) the second group consisted of a single dose of Tetrabenazine (0.64 mg/kg) and the third and fourth groups consisted of Haloperidol tested in two doses (0.04 and 0.12 mg/kg together with Tetrabenazine in one dose (0.64 mg/kg). All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a combination therapy using Pridopidine and Tetrabenazine for the treatment, prevention or alleviation of a movement disorder.

The effects of Pridopidine when given in combination with Tetrabenazine suggest, firstly, that the primary pharmacological effect of Pridopidine, i.e. dopamine D2 receptor blockade, is still present under coadministration with Tetrabenazine. This is reflected by the additional increase in stratital DOPAC induced by Pridopidine in Tetrabenazine treated rats. Given that a reduced tone at striatal D2 receptors is the proposed mechanism by which Tetrabenazine can alleviate involuntary movements in e.g. Huntington's disease, Tourettes disorder and tardive dyskinesia, this suggests that combining Tetrabenazine with Pridopidine could give additional clinical benefit in these disorders .

Secondly, Pridopidine reversed the behavioural inhibition caused by Tetrabenazine. This behavioural inhibition is a preclinical correlate of some troublesome dopamine related side effects limiting the use of Tetrabenazine, especially the clear-cut motor side effects, such as parkinsonism, i.e. reduced motility, but also possibly depressed mood. It should be noted that this reversal of the behavioural inhibition induced by Tetrabenazine is not to be expected from a compound acting as a pure antagonist at dopamine D2 receptors, such as Pridopidine, and was not observed in a similar study performed with the dopamine D2 antagonist Haloperidol. Rather, co-treatment with Haloperidol further reduced locomotor activity. Hence, these preclinical behavioural data implies that Pridopidine might counteract the adverse motor and affective effects of Tetrabenazine.

The subject invention provides a method of treating a subject afflicted with a movement disorder comprising periodically administering to the subject an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof, and an amount of Pridopidine or a pharmaceutically acceptable salt thereof.

The subject invention also provides a method of treating a subject afflicted with obesity, an obesity associated disorder, or a cardiovascular side effect of Pridopidine comprising administering to the subject an amount of Pridopidine or a pharmaceutically acceptable salt thereof, and an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof.

In an embodiment, the amounts when taken together are more effective to treat the subject than when each agent at the same amount is administered alone.

In an embodiment, either the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof when taken alone, and the amount of Pridopidine or a pharmaceutically acceptable salt thereof when taken alone, or each such amount when taken alone is not effective to treat the subject.

The subject invention also provides a method of reducing or preventing one or more side effects of periodically administering of an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof to a subject, comprising periodically administering to the subject an amount of Pridopidine or a pharmaceutically acceptable salt thereof .

In an embodiment, the one or more side effects are selected from depression, suicidality, akathisia, restlessness, agitation, parkinsonism, sedation, somnolence, and dysphagia.

In an embodiment, the side effect is parkinsonism.

In an embodiment, the subject is afflicted with a movement disorder.

In an embodiment, the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof is administered via oral administration.

In an embodiment, the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof is administered daily.

In an embodiment, the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof is administered twice daily.

In an embodiment, the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof is administered three times daily.

In an embodiment, the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof is 0.05 mg/kg per day to 0.20 mg/kg per day.

in an embodiment, the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof is 5-100 mg/day.

In an embodiment, the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof is 12.5 mg/day, 25 mg/day, 37.5 mg/day, 50 mg/day, 75 mg/day, or 100 mg/day.

In an embodiment, the amount of Pridopidine or a pharmaceutically acceptable salt thereof is administered via oral administration.

In an embodiment, the amount of Pridopidine or a pharmaceutically acceptable salt thereof is administered daily.

In an embodiment, the amount of Pridopidine or a pharmaceutically acceptable salt thereof is administered twice daily. In an embodiment, the amount of Pridopidine or a pharmaceutically acceptable salt thereof is 1.5 umol/kg per day to 20 umol/kg per day.

In an embodiment, the amount of Pridopidine or a pharmaceutically acceptable salt thereof is 10-100 mg/day.

In an embodiment, the amount of Pridopidine or a pharmaceutically acceptable salt thereof is 10 mg/day, 20 mg/day, 22.5 mg/day, 45 mg/day, or 90 mg/day.

In an embodiment, the movement disorder is Huntington's disease, Tourette's syndrome, or tardive dyskinesia.

In an embodiment, the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof and the amount of Pridopidine or a pharmaceutically acceptable salt thereof is effective to alleviate a symptom of the movement disorder.

In an embodiment, the symptom is chorea.

In an embodiment, the subject is receiving Tetrabenazine therapy prior to initiating administration of Pridopidine or a pharmaceutically acceptable salt thereof.

In an embodiment, the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof and the amount of Pridopidine or a pharmaceutically acceptable salt thereof are administered simultaneously.

In an embodiment, the subject is a human patient. The subject invention also provides a package comprising :

a) a first pharmaceutical composition comprising an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier;

b) a second pharmaceutical composition comprising and amount of Pridopidine or pharmaceutical acceptable salt thereof and a pharmaceutically acceptable carrier; and c) instruction for use for the first and the second pharmaceutical compositions together to treat a subject afflicted a movement disorder.

In an embodiment, the package is for use in treating a subject afflicted with a movement disorder.

In an embodiment, the movement disorder is Huntington's disease, Tourette's syndrome, or tardive dyskinesia.

The subject invention also provides Pridopidine or pharmaceutically acceptable salt thereof for use as an add-on therapy of or in combination with Tetrabenazine or pharmaceutical acceptable salt thereof in treating a subject afflicted with a movement disorder.

In an embodiment, the movement disorder is Huntington's disease, Tourette's syndrome, or tardive dyskinesia.

The subject invention also provides a pharmaceutical composition comprising an amount of Tetrabenazine or pharmaceutically acceptable salt thereof, an amount of

Pridopidine or pharmaceutical acceptable salt thereof, and at least one pharmaceutical acceptable carrier.

in an embodiment, the amount of Tetrabenazine or pharmaceutically acceptable salt thereof is 5-100 mg.

In an embodiment, the amount of Tetrabenazine or pharmaceutically acceptable salt thereof is 5 mg, 6.25 mg,

12.5 mg, 25 mg, 37.5 mg, 50 mg, 75 mg, or 100 mg.

In an embodiment, the amount of Pridopidine or pharmaceutical acceptable salt thereof is 10-100 mg.

in an embodiment, the amount of Pridopidine or pharmaceutical acceptable salt thereof is 10 mg, 22.5 mg, 45 mg, or 90 mg. In an embodiment, the pharmaceutical composition is for use in treating a subject afflicted with a movement disorder.

In an embodiment, the movement disorder is Huntington's disease, Tourette's syndrome, or tardive dyskinesia.

In an embodiment, the pharmaceutical composition is for use in treating, preventing or alleviating a subject afflicted with obesity, an obesity associated disorder, or a cardiovascular side effects of Pridopidine.

The subject invention also provides the use of:

a) an amount of Tetrabenazine or pharmaceutically acceptable salt thereof; and

b) an amount of Pridopidine or pharmaceutically acceptable salt thereof

in the preparation of a combination for treating a subject afflicted with a movement disorder wherein the amount of Tetrabenazine or pharmaceutically acceptable salt thereof and the amount of Pridopidine or pharmaceutically acceptable salt thereof are administered simultaneously or contemporaneously.

In an embodiment, the movement disorder is Huntington's disease, Tourette's syndrome, or tardive dyskinesia.

The subject invention also provides a pharmaceutical composition comprising an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof for use in treating a subject afflicted with a movement disorder, in combination with an amount of Pridopidine or pharmaceutically acceptable salt thereof, by periodically administering to the subject the pharmaceutical composition and the amount of Pridopidine or pharmaceutically acceptable salt thereof.

The subject invention also provides a pharmaceutical composition comprising an amount of Pridopidine or pharmaceutically acceptable salt thereof for use treating a subject afflicted with a movement disorder, in combination with an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof, by periodically administering to the subject the pharmaceutical composition and the amount of Tetrabenazine or a pharmaceutically acceptable salt thereof.

In an embodiment, the movement disorder is Huntington's disease, Tourette's syndrome, or tardive dyskinesia.

The subject invention also provides Tetrabenazine or a pharmaceutically acceptable salt thereof and Pridopidine or a pharmaceutically acceptable salt thereof for the treatment of a subject afflicted with a movement disorder, wherein the Tetrabenazine or a pharmaceutically acceptable salt thereof and the Pridopidine or a pharmaceutically acceptable salt thereof are administered simultaneously, separately or sequentially.

In an embodiment, the movement disorder is Huntington's disease, Tourette's syndrome, or tardive dyskinesia.

The subject invention also provides a product containing an amount of Tetrabenazine or a pharmaceutically acceptable salt thereof and an amount of Pridopidine or a pharmaceutically acceptable salt thereof for simultaneous, separate or sequential use in treating a subject afflicted with a movement disorder.

In an embodiment, the movement disorder is Huntington's disease, Tourette's syndrome, or tardive dyskinesia.

The subject invention also provides a method of treating a subject afflicted with obesity, an obesity associated disorder or a cardiovascular side effect of Pridopidine comprising administering to the subject a combination of a therapeutically effective amount of Pridopidine or a pharmaceutically acceptable salt thereof, and a therapeutically effective amount of Tetrabenazine or a pharmaceutically acceptable salt thereof, wherein the amounts when taken together are effective to treat the subject.

In an embodiment, the subject is a human patient.

The subject invention also provides a combination of Pridopidine, r a pharmaceutically acceptable salt thereof; and Tetrabenazine, or a pharmaceutically acceptable salt thereof; for the treatment, prevention or alleviation of obesity, or an obesity associated disorder, and for treatment, prevention or alleviation of the cardiovascular side effects of Pridopidine, in a mammal, including a human.

In another aspect, the present invention relates to a combination therapy in which a pharmaceutically effective amount of Pridopidine, or a pharmaceutically acceptable salt thereof, is administered together with a therapeutically effective amount of Tetrabenazine, or a pharmaceutically acceptable salt thereof, for the treatment, prevention or alleviation of a movement disorder.

In a preferred embodiment the hyperkinetic movement disorder is an involuntary hyperkinetic movement disorder arising from Huntington's disease, Gilles de la Tourette's syndrome, or tardive dyskinesia, and in particular an involuntary hyperkinetic movement disorder arising from Huntington's disease.

Viewed from another aspect, the invention provides a combination of Pridopidine, or a pharmaceutically acceptable salt thereof, and Tetrabenazine, or a pharmaceutically acceptable salt thereof, for use as a medicament.

In another aspect, the invention relates to the use of a combination of

(i) Pridopidine, or a pharmaceutically acceptable salt thereof; and (ii) Tetra enazine, or a pharmaceutically acceptable salt thereof;

for the manufacture of a medicament for the treatment, prevention or alleviation of a movement disorder of a mammal, including a human.

In another aspect, the invention provides pharmaceutical compositions comprising Pridopidine, or a pharmaceutically acceptable salt thereof, for use in a combination therapy together with Tetrabenazine, or a pharmaceutically acceptable salt thereof, for the treatment, prevention or alleviation of a hyperkinetic movement disorder.

In another aspect the invention provides a method for the treatment, prevention or alleviation of a hyperkinetic movement disorder in a living animal body, which method comprises the step of administering to such animal bodies in need thereof, a therapeutically effective amount of Pridopidine, or a pharmaceutically acceptable salt thereof; in a combination therapy with Tetrabenazine, or a pharmaceutically acceptable salt thereof.

In another aspect the invention provides a pharmaceutical composition comprising a therapeutically effective amount of Pridopidine, or a pharmaceutically acceptable salt thereof, and a therapeutically effective amount of Tetrabenazine, or a pharmaceutically acceptable salt thereof.

In a further aspect the invention provides for a kit of parts comprising at least two separate unit dosage forms (A) and (B) , wherein (A) comprises Pridopidine, or a pharmaceutically acceptable salt thereof; and (B) comprises Tetrabenazine, or a pharmaceutically acceptable salt thereof, and optionally (C) , instructions for the simultaneous, sequential or separate administration of the Pridopidine of (A) and the Tetrabenazine of (B) , to a patient in need thereof .

In a further aspect the invention provides an article of manufacture, comprising (A) a first pharmaceutical dosage form comprising Pridopidine, or a pharmaceutically acceptable salt thereof; and (B) a second pharmaceutical dosage form comprising Tetrabenazine, or a pharmaceutically acceptable salt thereof; wherein the article contains first and second pharmaceutical dosage forms.

In a further aspect the invention provides a method of treating a subject afflicted with a movement disorder comprising administering to the subject a combination of a therapeutically effective amount of Pridopidine or a pharmaceutically acceptable salt thereof, and a therapeutically effective amount of Tetrabenazine or a pharmaceutically acceptable salt thereof, wherein the amounts when taken together are effective to treat the human patient.

In an embodiment, the movement disorder is an involuntary hyperkinetic movement disorder arising from Huntington's disease, Gilles de la Tourette's syndrome, or tardive dyskinesia.

In an embodiment, the movement disorder is an involuntary hyperkinetic movement disorder arising from Huntington's disease

In a further aspect the invention provides a method of treating a mammal, including a human, afflicted with an obesity, or an obesity associated disorder or of the cardiovascular side effects of Pridopidine comprising administering to the subject a combination of a therapeutically effective amount of Pridopidine or a pharmaceutically acceptable salt thereof, and a therapeutically effective amount of Tetrabenazine or a pharmaceutically acceptable salt thereof, wherein the amounts when taken together are effective to treat a mammal. In an embodiment, the therapeutically effective amount of Pridopidine or the pharmaceutically acceptable salt thereof, and the therapeutically effective amount of Tetrabenazine or the pharmaceutically acceptable salt thereof are administered orally.

In an embodiment, the therapeutically effective amount of Pridopidine or the pharmaceutically acceptable salt thereof, and the therapeutically effective amount of Tetrabenazine or the pharmaceutically acceptable salt thereof are administered intravenously.

in an embodiment, the therapeutically effective amount of Pridopidine or the pharmaceutically acceptable salt thereof, and the therapeutically effective amount of Tetrabenazine or the pharmaceutically acceptable salt thereof are administered by direct penetration of the drug through the stratum corneum.

The Pridopidine containing medicament may be applied simultaneously with Tetrabenazine, in a sequential manner, or by separate administration. Preferably Pridopidine is given at the same time as Tetrabenazine.

It is currently believed that Pridopidine may be used (co-administered with Tetrabenazine) in a therapeutically effective amount in the range of about 0.01 - 1000 mg ΛΡΙ daily, more preferred in the range of about 1 - 500 mg API daily, even more preferred in the range of about 10 - 200 mg API daily.

It is currently believed that Tetrabenazine may be used (co-administered with Pridopidine) in a therapeutically effective amount in the range of about 0.01 - 1000 mg API daily, more preferred in the range of about 1 - 500 mg API daily, even more preferred in the range of about 10 - 200 mg API daily. Pridopidine and Tetrabenazine may be co-administered by any conventional route. In a preferred embodiment Pridopidine and Tetrabenazine are administered either orally, intravenously, intravascularly, intraperitoneally, sub- cutaneously, intramuscularly, inhalatively, topically, by patch, or by suppository.

In a more preferred embodiment Pridopidine and Tetrabenazine are administered orally (p.o.).

In another more preferred embodiment Pridopidine and Tetrabenazine are administered intravenously (i.v. ).

In another embodiment Pridopidine and Tetrabenazine are administered by subcutaneous (s.c.) injection.

Any combination of two or more of the embodiments described herein is considered within the scope of the present invention.

Pharmaceutically Acceptable Salts

The active compounds for use according to the invention may be provided in any form suitable for the intended administration. Suitable forms include pharmaceutically (i.e. physiologically) acceptable salts, and pre- or prodrug forms of the compound of the invention.

Examples of pharmaceutically acceptable addition salts include, without limitation, the non-toxic inorganic and organic acid addition salts such as the hydrochloride, the hydrobromide, the nitrate, the perchlorate, the phosphate, the sulphate, the formate, the acetate, the aconate, the ascorbate, the benzenesulphonate, the benzoate, the cinnamate, the citrate, the embonate, the enantate, the fuma- rate, the glutamate, the glycolate, the lactate, the maleate, the malonate, the mandelate, the methanesulphonate, the naphthalene-2-sulphonate, the phthalate, the salicylate, the sorbate, the stearate, the succinate, the tartrate, the toluene-p-sulphonate, and the like. Such salts may be formed by procedures well known and described in the art.

Pharmaceutical Compositions

While the compounds for use according to the invention may be administered in the form of the raw compound, it is preferred to introduce the active ingredients, optionally in the form of physiologically acceptable salts, in a pharmaceutical composition together with one or more adjuvants, excipients, carriers, buffers, diluents, and/or other customary pharmaceutical auxiliaries.

In a preferred embodiment, the invention provides pharmaceutical compositions comprising the active compounds or pharmaceutically acceptable salts or derivatives thereof, together with one or more pharmaceutically acceptable carriers therefore, and, optionally, other therapeutic and/or prophylactic ingredients know and used in the art. The carrier (s) must be "acceptable" in the sense of being compatible with the other ingredients of the formulation and not harmful to the recipient thereof.

The pharmaceutical composition of the invention may be administered by any convenient route, which suits the desired therapy. Preferred routes of administration include oral administration, in particular in tablet, in capsule, in drage, in powder, or in liquid form, and parenteral administration, in particular cutaneous, subcutaneous, intramuscular, or intravenous injection. The pharmaceutical composition of the invention can be manufactured by the skilled person by use of standard methods and conventional techniques appropriate to the desired formulation. When desired, compositions adapted to give sustained release of the active ingredient may be employed.

Further details on techniques for formulation and administration may be found in the latest edition of Remington's Pharmaceutical Sciences (Maack Publishing Co., Easton, PA) .

The actual dosage of each of the active ingredients depends on the nature and severity of the disease being treated, the exact mode of administration, form of administration and is within the discretion of the physician, and may be varied by titration of the dosage to the particular circumstances of this invention to produce the desired therapeutic effect. However, the below dosages for the compound and the anti-obesity compound are considered suitable.

The dosage of the compound is determined as the API (Active Pharmaceutical Ingredient), i.e. calculated as the free base.

A daily dosage in the range of about 0.1-2 mg API daily, preferably of about 0.25-1 mg API daily, especially 0.25, 0.5 or 1.0 mg API daily, is suitable for therapeutic treatments. The daily dosage of the compound may be administered in one or several doses, such as two, per day.

In one embodiment, the daily dosage is administered in one dose.

The daily dosage of the anti-obesity compound is presently contemplated to be in the range of about 0.1-500 mg of active ingredient depending on the actual compound. More specific dosage intervals may be in the range of about 0.1-2 mg, about 1-10 mg, about 10-50 mg, about 25-100 mg, about 50- 200 mg and about 100-500 mg daily. The daily dosage of the anti-obesity compound may be administered in one or several doses, such as two, per day. In one embodiment, the daily dosage is administered in one dose.

AS used herein, "effective* as in an amount effective to achieve an end means the quantity of a component that is sufficient to yield an indicated therapeutic response without undue adverse side effects (such as toxicity, irritation, or allergic response) commensurate with a reasonable benefit/risk ratio when used in the manner of this disclosure. For example, an amount effective to treat a movement disorder. The specific effective amount will vary with such factors as the particular condition being treated, the physical condition of the patient, the type of mammal being treated, the duration of the treatment, the nature of concurrent therapy (if any) , and the specific formulations employed and the structure of the compounds or its derivatives .

As used herein, to "treat" or "treating" encompasses, e.g., inducing inhibition, regression, or stasis of the disorder and/or disease. As used herein, "inhibition" of disease progression or disease complication in a subject means preventing or reducing the disease progression and/or disease complication in the subject.

As used herein, "combination" means an assemblage of reagents for use in therapy either by simultaneous or contemporaneous administration. Simultaneous administration refers to administration of an admixture (whether a true mixture, a suspension, an emulsion or other physical combination) of the Pridopidine and the Tetrabenazine. In this case, the combination may be the admixture or separate containers of the Pridopidine and the Tetrabenazine that are combined just prior to administration. Contemporaneous administration refers to the separate administration of the Pridopidine and the Tetrabenazine at the same time, or at times sufficiently close together that a synergistic activity or an activity that is additive or more than additive relative to the activity of either the Pridopidine or the Tetrabenazine alone is observed.

As used herein, "DOPAC" is 3, -Dihydroxyphenylacetic acid. As used herein, "LMA" is Locomotor activity.

As used herein, *TBZ" is Tetrabenazine.

Pharmaceutical Kits of Parts

According to the invention there is also provided a kit of parts comprising at least two separate unit dosage forms (A) and (B) , wherein

(A) comprises Pridopidine, or a pharmaceutically acceptable salt thereof; and

(B) comprises Tetrabenazine, or a pharmaceutically acceptable salt thereof; and optionally

(C) instructions for the simultaneous, sequential or separate administration of the Pridopidine of (A) and the Tetrabenazine of (B) , to a patient in need thereof.

Pridopidine for use according to the invention and

Tetrabenazine for use according to the invention may preferably be provided in a form that is suitable for administration in conjunction with the other. This is intended to include instances where one or the other of two formulations may be administered (optionally repeatedly) prior to, after, and/or at the same time as administration with the other component.

Also, Pridopidine for use according to the invention and Tetrabenazine for use according to the invention may be administered in a combined form, or separately or separately and sequentially, wherein the sequential administration is close in time or remote in time. This may in particular include that two formulations are administered (optionally repeatedly) sufficiently closely in time for there to be a beneficial effect for the patient, that is greater over the course of the treatment of the relevant condition than if either of the two formulations are administered (optionally repeatedly) alone, in the absence of the other formulation, over the same course of treatment. Determination of whether a combination provides a greater beneficial effect in respect of, and over the course of treatment of, a particular condition, will depend upon the condition to be treated or prevented, but may be achieved routinely by the person skilled in the art.

When used in this context, the terms "administered simultaneously" and "administered at the same time as" include that individual doses of Pridopidine and Tetrabenazine are administered within 48 hours, e.g. 24 hours, of each other.

Bringing the two components into association with each other, includes that components (A) and (B) may be provided as separate formulations (i.e. independently of one another) , which are subsequently brought together for use in conjunction with each other in combination therapy; or packaged and presented together as separate components of a "combination pack" for use in conjunction with each other in combination therapy.

According to the invention there is also provided an article of manufacture, comprising (A) a first pharmaceutical dosage form comprising Pridopidine, or a pharmaceutically acceptable salt thereof; and (B) a second pharmaceutical dosage form comprising Tetrabenazine, or a pharmaceutically acceptable salt thereof; wherein the article contains first and second pharmaceutical dosage forms.

Methods of Therapy

In another aspect the invention provides methods of treatment, prevention or alleviation of a hyperkinetic movement disorder in a living animal body, including a human, which method comprises the step of administering to such a living animal body in need thereof, a therapeutically effective amount of Pridopidine, or a pharmaceutically acceptable salt thereof; in a combination therapy with Tetrabenazine, or a pharmaceutically acceptable salt thereof.

The hyperkinetic movement disorder may in particular be an involuntary movement disorder arising from Huntington's disease, Gilles de la Tourette's syndrome, or tardive dyskinesia .

In a preferred embodiment, the hyperkinetic movement disorder is an involuntary movement disorder arising from Huntington's disease.

Introduction to the Example

Motor function is controlled by a complex circuitry connecting the cerebral cortex with subcortical structures including the basal ganglia and the thalamus. One major pathway within this circuitry is the so called "indirect pathway" forming a closed feed-back loop connecting the cortex, the striatum, and the thalamus via a population of striatal GABA-ergic, medium spiny neurons expressing dopamine D2 type receptors. This pathway functions as a negative regulator of movements, and is important for the suppression of excessive movements. Dopamine modulates the indirect pathway by inhibitory dopamine D2 receptors in such a way that increased dopamine tone at these receptors leads to a reduced activity of the indirect pathway, and therefore a reduced ability to suppress movements. On the other hand, a diminished dopamine tone leads to increased activity of the indirect pathway associated with stronger suppression of movements .

Another important cortico-striato-thalamic pathway involved in motor control is the so called "direct pathway", forming a closed, positive feed-back loop via striatal GABA- ergic, medium spiny neurons expressing dopamine Dl type receptors. The direct pathway is a positive modulator of motor function, involved in the selection and enabling of voluntary movements. Dopamine, acting at Dl type receptors, stimulates the striatal GABA-ergic neurons in the direct pathway, thereby enhancing movements. Conversely, a reduction in dopamine tone at these Dl receptors leads to a reduced ability to perform voluntary movements.

The general reduction in dopamine transmission resulting from treatment with Tetrabenazine also reduces other dopamine dependent functions. In particular, the dopamine tone at the direct pathway, with striatal neurons expressing dopamine Dl receptors, is also reduced, leading to a weakening of the direct pathway and therefore to a reduced capacity to perform voluntary movements. Furthermore, the dopamine depletion induced by Tetrabenazine is likely to impair dopamine dependent motivation and reward, which is hypothesised to underlie the pro-depressant adverse effects of Tetrabenazine.

Given that Pridopidine is a pure antagonist at dopamine D2 receptors, with no agonist activity, it was expected that a therapeutic combination of Pridopidine and Tetrabenazine would lead to further reduced tone at dopamine D2 receptors, and therefore to a further reduction in overall locomotor activity, compared to treatment with Tetrabenazine only. Example

The invention is further illustrated with reference to the following examples, which are not intended to be in any way limiting to the scope of the invention as claimed.

The examples below explore the interaction between Pridopidine and Tetrabenazine with respect to locomotor activity. Striatal levels of dopamine and DOPAC were also determined. Tetrabenazine reduces tissue levels of dopamine as a direct consequence of the inhibition of VMAT. Both compounds increase striatal DOPAC levels in a dose-dependent manner in vivo, reflecting decreased tone at the dopamine D2 receptor (Ponten 2010; Reches, 1983). Furthermore, the effect on expression of the immediate-early gene Arc (activity- regulated cytoskeleton-associated protein/activity-regulated gene 3.1) was measured in the frontal cortex and striatum. Arc gene expression is a biomarker reflecting synaptic activity (Steward, 2001; Kawashima 2009). Interaction experiments with Tetrabenazine and the dopamine D2 antagonist haloperidol were also performed in order to compare the effects of Pridopidine with those of a classical dopamine D2 receptor antagonist

1) Effect of Tetrabenazine on locomotor activity, striatal DOPAC, and Arc

Tetrabenazine was given sc at 0.37, 0.64 and 1.1 mg/kg. LMA was recorded for 60 minutes after dosing. Thereafter rats were sacrificed and brains were collected. Analyses of brain tissues included DOPAC in the striatum, and Arc mRNA in the frontal cortex and striatum.

Tetrabenazine reduced locomotor activity. (Fig. 1) .

Tetrabenazine dose dependently inhibited spontaneous locomotor activity. When the full hour of recording was considered, the 1.1 mg/kg Tetrabenazine dose group displayed a significant reduction to 40% of the vehicle control group mean (P<0.01) . During the initial 15 min significant reductions (P<0.05) were seen both for the 1.1 and 0.37 mg/kg Tetrabenazine dose groups, whereas for the period 15-60 minutes post dosing significant effects (P<0.05) were observed at 0.64 and 1.1 mg/kg. The reduction in locomotor activity reflects the decreased dopamine transmission caused by inhibition of VMAT2.

Tetrabenazine dose dependently increases striatal DOPAC, with statistically significant effects at all doses tested. The increase in DOPAC is a neuronal marker of reduced tone at dopamine D2 receptors, due to the decreased dopamine transmission in rats treated with Tetrabenazine. See Table 1 and Fig. 1-2.

Arc in striatum and cortex: Tetrabenazine increased striatal Arc and reduced frontal cortex Arc. Tetrabenazine dose dependently increased Arc mRNA in the striatum, reaching 147% of the vehicle control group mean (P<0.01) at the highest dose tested (1.1 mg/kg) . In the frontal cortex, a significant reduction of Arc mRNA down to 66% of the vehicle control group mean was observed at Tetrabenazine dose of 1.1 mg/kg (P<0.05). At Tetrabenazine dose of 0.64 mg/kg, there was a trend towards a reduction in frontal cortex mRNA (83% of control group mean, p=0.14). See Fig. 3. The Arc increase in the striatum is most likely due to reduced tone at dopamine D2 receptors. The Arc decrease in the frontal cortex is likely to be related to decreased dopamine transmission in the cortex leading to a reduced tone at dopamine Dl receptors. 2) Effect of Pridopidine on locomotor activity, striatal DOPAC, and Arc

Pridopidine was given sc at 11, 33 and 100 umol/kg. Pridopidine displayed no inhibitory effect on spontaneous locomotor activity. A slight increase in locomotor activity was observed at the mid dose, 33 umol/kg, over the full 60 minute recording period. See Fig. 4. When the full hour of recording was examined, a significant increase in locomotor activity to 138% of the vehicle control group mean was observed for the 33 umol/kg Pridopidine dose group (P<0.05) . During the initial 15 min a significant increase (P<0.05) was seen for the 11 umol/kg Pridopidine dose group, whereas for the period 15-60 minutes post dosing no significant effects were observed. Pridopidine dose dependently increases striatal DOPAC, with statistically significant effects at all doses tested. The increase in DOPAC is a neuronal marker of reduced tone at dopamine D2 receptors, due to dopamine D2 receptor antagonism exerted by Pridopidine. See Fig. 5 and Table 1.

Pridopidine dose-dependently increased striatal and cortical arc gene expression, reaching statistical significance at the highest doses tested. Pridopidine increased Arc mRNA levels in the frontal cortex in a dose- dependent manner, up to 149% (p < 0.01) and 222% {p < 0.001) of the vehicle control group mean at doses of 33 umol/kg and 100 umol/kg, respectively (Fig. €) . Pridopidine increased Arc mRNA levels in the striatum in a dose-dependent manner. Compared with the relevant control group means, levels reached 168% and 253% (p < 0.01 for both doses at Pridopidine 33 umol/kg and 100 umol/kg, respectively). (Fig. 6) .The Arc increase in the striatum is most likely due to reduced tone at dopamine D2 receptors. The Arc increase in the frontal cortex is likely to be related to increased dopamine transmission in the cortex leading to an increased tone at dopamine Dl receptors.

3) Effect of haloperidol on locomotor activity, striatal DOPAC, and Arc

Haloperidol was given sc at 0.12, 0.37 and 1.1 mg/kg

(See Fig. 7) . In an additional experiment assessing effects at lower doses, 0.04, 0.12. 0.37 and 1.1 mg was given (See Fig. 302) . Haloperidol displayed a dose-dependent inhibitory effect on spontaneous locomotor activity. Statistically significant effects were observed at 0.12 mg/kg and higher doses, but not at the lowest dose tested, 0.04 mg/kg.

More specifically, when the full hour of recording was considered, the 0.37 and l.lmg/kg haloperidol dose groups displayed significant reductions to about 35% of the vehicle control group mean (P<0.05). During the initial 15 min, significant reductions (P<0.05) were seen both for the 0.37 and 1.1 mg/kg haloperidol dose groups, whereas for the period 15-60 minutes post dosing a significant effect (P<0.05) was observed for the 1.1 mg/kg dose group only.

Haloperidol dose dependently increases striatal DOPAC, with statistically significant effects at all doses tested. The increase in DOPAC is a neuronal marker of reduced tone at dopamine D2 receptors, due to dopamine D2 receptor antagonism. See Table 1 and Fig. 9.

Haloperidol dose dependently increased Arc mRNA in the striatum, reaching 262% <P<0.01), 331% (P<0.001), 409% (P<0.01), respectively, of the vehicle control group mean at the 0.12 mg/kg, 0.37 mg/kg and 1.1 mg/kg doses. The Arc increase in the striatum is most likely due to reduced tone at dopamine D2 receptors. There was no significant effect of Haloperidol on cortical Arc gene expression. See Fig. 10.

In summary, while all three antidopaminergic compounds produced increased striatal DOPAC, and increased striatal arc gene expression, both effects most likely related to decreased tone at dopamine D2 receptors, Pridopidine was unique in that it did not inhibit locomotor activity. Another feature differentiating Pridopidine from Haloperidol or Tetrabenazine, is that it increased cortical Arc gene expression. Combination Experiments

To test the effect of dopamine D2 antagonist when administered to partially dopamine depleted animals, Haloperidol and Pridopidine were combined with Tetrabenazine at a dose that produced submaximal but significant effects on striatal dopac and locomotor activity.

4) Effect of Pridopidine on Tetrabenazine induced locomotor activity reduction, striatal dopamine increase, and Arc

In the interaction experiment with Pridopidine and

Tetrabenazine, Pridopidine was given at 33 and 100 umol/kg, combined with Tetrabenazine at 0.64 mg/kg. See Fig. 11. The locomotor recordings demonstrated that Pridopidine reversed the behavioural inhibition induced by Tetrabenazine. However, the effects on striatal DOPAC were additive, i.e. coadministration of Pridopidine further increased striatal DOPAC.

For the locomotor inhibition, there was a significant decrease in the Tetrabenazine control group vs. vehicle treated controls for the full hour of recording (P<0.001), as well for both the 0-15 min period (P<0.01) and the 15-60 min period (P<0.01) . Considering the full hour of recording, Pridopidine reversed the locomotor inhibition induced by Tetrabenazine at both the 33 and the 100 umol/kg dose groups, reaching 135% (P<0.05) and 137% (P<0.01), respectively of Tetrabenazine control mean. During the 0-15 min as well as for the 15-60 min periods this reversing effect reached significance for the Pridopidine 100 umol/kg dose group. This implies that the tone at striatal D2 receptors is further reduced when adding Pridopidine to monoamine depleted animals. See Fig. 11.

In the interaction experiment where Tetrabenazine 0.64 mg/kg was combined with either Pridopidine 33 umol/kg or 100 umol/kg, Tetrabenazine induced a significant increase in striatal DOPAC levels was seen compared with the vehicle- treated control group (p < 0.01; Table 1) . Pridopidine further increased DOPAC levels in striatum, reaching 155% of the Tetrabenazine control group mean at the 100 umol/kg dose (p < 0.01). See Table 1 and Fig. 12.

Likewise, striatal Arc expression was further increased by adding Pridopidine. In contrast, the Arc decrease induced by Tetrabenazine was counteracted by Pridopidine.

Pridopidine reversed the decrease in frontal cortex

Arc induced by Tetrabenazine as shown in Fig. 13. More specifically, Tetrabenazine had no significant effect on striatal Arc mRNA at the 0.64 mg/kg dose used in the interaction experiment. Pridopidine, when coadministered with Tetrabenazine, dose dependently increased striatal Arc, reaching 144% (P<0.05) and 207% (P<0.01), respectively, of the Tetrabenazine control group mean at the 33 umol/kg, and the 100 umol/kg doses of Pridopidine.

Tetrabenazine induced a significant decrease (P<0.05) in frontal cortex Arc mRNA, which is in accordance with the trend towards a decrease of frontal cortex Arc mRNA at the 0.64 mg/kg dose observed in the dose response experiment with Tetrabenazine (Fig. 3). Pridopidine dose dependently reversed the decrease in frontal cortex Arc mRNA induced by Tetrabenazine. At 33 umol/kg and 100 umol/kg of Pridopidine, Arc mRNA was increased to 125% <P<0.05) and 193% (P<0.05), respectively, of the Tetrabenazine control group mean

5) Effect of Haloperidol on Tetrabenazine induced locomotor activity reduction, striatal dopamine increase, and Arc

In the interaction experiment with Haloperidol and Tetrabenazine, Haloperidol was given at 0.04 and 0.12 mg/kg, combined with Tetrabenazine at 0.64 mg/kg. The locomotor recordings showed that Haloperidol further reduced locomotor activity in animals treated with Tetrabenazine. More specifically, the locomotor recording over the full hour demonstrated that haloperidol significantly (P<0.01) reduced locomotor activity in rats treated with Tetrabenazine both at the 0.04 and 0.12 mg/kg doses, down to 51% and 41% of Tetrabenazine control group mean, respectively. For the first 15 min of recording this reducing effect was significant at both the 0.04 mg/kg (P<0.01) and the 0.12 mg/kg (P<0.05) doses, whereas for the 15-60 min period the reduction was significant for the 0.12 mg/kg dose only (P<0.05). See Fig. 14.

The effects on striatal DOPAC were additive, i.e. coadministration of Haloperidol with Tetrabenazine caused additional increases in striatal DOPAC. In the interaction experiment where Tetrabenazine 0.64 mg/kg was combined with haloperidol 0.04 mg/kg or 0.12 mg/kg, Tetrabenazine induced a significant increase in striatal DOPAC levels compared with the vehicle-treated control group (p < 0.001; Table 1) . Haloperidol further increased DOPAC levels in striatum, reaching 187% and 218% of the Tetrabenazine control group mean at the 0.04 mg/kg and 0.12 mg/kg doses, respectively (p < 0.001 for both doses). See Table 1 and Fig. 15.

There was no significant effect of Haloperidol on cortical Arc gene expression in rats co-treated with Tetrabenazine. Haloperidol further increases striatal Arc in Tetrabenazine treated animals (Fig. 16) . Tetrabenazine had no significant effect on striatal Arc mR A at the 0.64 mg/kg dose used in the interaction experiment. Haloperidol, when coadministered with Tetrabenazine, dose dependently increased striatal Arc, reaching 272% (P<0.001) and 400% (P<0.001), respectively, of the Tetrabenazine control group mean at the 0.04 mg/kg, and the 0.12 mg/kg doses of haloperidol. Tetrabenazine tended to decrease frontal cortex Arc mRNA (P=0.08), which is in accordance with the trend towards a decrease of frontal cortex Arc mRNA at the 0.64 mg/kg dose observed in the dose response experiment with Tetrabenazine (Fig. 3), and the significant decrease observed in the interaction experiment with Pridopidine and Tetrabenazine (Fig. 13) . There was no significant effect of haloperidol on frontal cortex Arc mRA in Tetrabenazine treated animals. Test methods

The following tests are used for evaluation of the compounds for use according to the invention.

Animals

Male Sprague-Dawley rats from B&K Scanbur

(Sollentuna, Sweden) (IBBS58) , Charles River (Κδΐη, Germany) (KR104, BS31) or Taconic (Ejby, Denmark) (BS85, BS81, KR219, TA284) were used. Rats weighed 160-180g at the time of arrival. Rats weighed 220-260g at the time of the locomotor and tissue neurochemistry studies. Animals were housed five animals per cage with lights on between 06:00 and 18:00. All experiments were carried out in accordance with Swedish animal protection legislation and with the approval of the local Animal Ethics Committee in Gothenburg.

Dosing

IBBS58: Animals were allocated into four different treatment groups, n=5. The treatment groups consisted of Vehicle (saline; NaCl 0.9% v/w) and ACR16 tested at three doses (11; 33 and 100 umol/kg) .

BS31: Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of vehicle (Glucose 5.5% v/w) and Haloperidol tested at three doses (0.12; 0.37 and 1.1 umol/kg). R104: Animals were allocated into five different treatment groups, n = 4. The treatment groups consisted of Vehicle (Glucose 5.5% v/w) and Haloperidol tested at four doses (0.04; 0.12; 0.37 and 1.1 umol/kg) .

KR219: Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle (Glucose 5.5% v/w) and Tetrabenazine tested at three doses (0.37; 0.64 and 1.1 umol/kg).

BS81: Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle 1:1 (saline; NaCl 0.9% v/w+ 5.5% glukos with a few drops of HAc) the second group consisted of a single dose of Tetrabenazine (0.64 mg/kg) and the third and fourth groups consisted of NS30016 tested in two doses (33 and 100 umol/kg together with Tetrabenazine in one dose (0.64 mg/kg).

TA284: Animals were allocated into four different treatment groups, n = 10. The treatment groups consisted of Vehicle 1:1 (saline; NaCl 0.9% v/w+ 5.5% glukos with a few drops of HAc) the second group consisted of a single dose of Tetrabenazine (0.64 mg/kg) and the third and fourth groups consisted of NS30016 tested in two doses (33 and 100 umol/kg together with Tetrabenazine in one dose (0.64 mg/kg). No brain tissue was collected from this experiment.

BS85: Animals were allocated into four different treatment groups, n = 5. The treatment groups consisted of Vehicle 1:1 (saline; NaCl 0.9% v/w+ 5.5% glukos with a few drops of HAc) the second group consisted of a single dose of Tetrabenazine (0.64 mg/kg) and the third and fourth groups consisted of Haloperidol tested in two doses (0.04 and 0.12 mg/kg together with Tetrabenazine in one dose (0.64 mg/kg).

All compounds were injected s.c. four minutes before start of locomotor activity recording at a volume of 5 ml/kg.

In vivo test: Behaviour Behavioural activity is measured using eight Digiscan activity monitors (RXYZM (16) TAO, Omnitech Electronics, Columbus, OH, USA) , connected to an Omnitech Digiscan analyzer and an Apple Macintosh computer equipped with a digital interface board (NB DIO-24, National Instruments, USA) . Each activity monitor consists of a quadratic metal frame equipped with photobeam sensors. During measurements of behavioural activity, a rat is put in a transparent acrylic cage with matted black floor (WxLxH, 41 x 41 x 30 cm) which in turn is placed in the activity monitor. Each activity monitor is equipped with three rows of infrared photobeam sensors, each row consisting of 16 sensors. Two rows are placed along the front and the side of the floor of the cage, at a 90 degree angle, and the third row is placed 10 cm above the floor to measure vertical activity. Photobeam sensors are spaced 2.5 cm apart. Each activity monitor is fitted in an identical sound and light attenuating box (WXLxH - 55 x 55 x 45) containing a weak house light and a fan.

The computer software is written using object oriented programming (LabVIEW" ¹ , National instruments, Austin, TX, USA) .

Behavioural data from each activity monitor, representing the position (horizontal center of gravity and vertical activity) of the animal at each time, are recorded at a sampling frequency of 25 Hz and collected using a custom written LABView™ application. The data from each recording session are stored and analyzed with respect to distance travelled. Each behavioural recording session lasts 60 min, starting approximately 4 min after the injection of test compound. The results are presented as counts/60 minutes, counts/45 minutes or counts/15 minutes, in arbitrary length units. Statistical comparisons are carried out using Student's t-test against the control group. In vivo test: Neurochemistry

Immediately after the behavioural activity sessions, the rats are decapitated and their brains rapidly taken out and put on an ice-cold petri-dish.

Brains were dissected into striatum, limbic region

(containing the nucleus accumbens - both core and shell, amygdala, most parts of the olfactory tubercle and ventral pallidum), frontal cortex and hippocampus. Tissue samples were immediately frozen and stored at -80°C until it was homogenized with perchloric acid (PCA) (0.1M), ethylene- diamine-tetraacetic acid (EDTA) (5,37 mH) , glutathione (GSH) (0.65 KIM) and alpha-methyl-dopamine (0.25 UM) as internal standard. A digital sonifier (Branson Digital Sonifier 250-D) was used to homogenise tissue from the striatum and limbic region. Cortex tissue was homogenised using an Ultra Turrax T25 hotmogeniser . All samples were centrifuged at 10.000 rpm for 10 minutes at +4°C. Cortex tissue was filtered in Munktell filter paper 5.5 cm quality IF. Tissue eluates were analysed with respect to tissue concentrations (ng/g tissue) of the monoamine transmitter substances (Norepinephrine (NA) , dopamine (DA) , 5-hydroxytryptamine (5-HT) ) as well as their amine metabolites (normetanephrine (N ) , 3-methoxytyramine (3-MT)) and acid metabolites (3, 4-dihydroxyphenylalanine (DOPAC) , 5-hydrocyindoleacetic acid (5-HIAA), homovanillic acid (HVA) ) by HPLC separations and electrochemical detection (HPLC/EC) . Stock Standards (DA, NA, 5-HT, 3-MT, DOPAC, HVA, HIAA, 500ug/ml) and internal standard (AMDA 500ug/ml) are prepared once every three months. 5-HT and 5HIAA are dissolved in milliQ water. DA, NA, DOPAC, MM, 3-MT and HVA are dissolved in 0.01 M HCl. 5-HT, 5-HIAA, NM and HVA are kept in fridge; DA, DOPAC, NA and 3-MT are kept in freezer. Standard solution for analyses containing standards diluted in homogenising solution to a concentration of 0.05 ug/ml is prepared daily. The analytical method is based on two chromatographic separations dedicated for amines or acids. Two chromatographic systems share a common auto injector with a 10-port valve and two sample loops for simultaneous injection on the two systems. Both systems are equipped with a reverse phase column (Luna C18(2), dp 3 urn, 50 x 2 mm i.d. , Phenomenex) and electrochemical detection is accomplished at two potentials on glassy carbon electrodes ( F-1000, Bioanalytical Systems, Inc.). The column effluent is passed via a T-connection to the detection cell or to a waste outlet. This is accomplished by two solenoid valves, which block either the waste or detector outlet. By preventing the chromatographic front from reaching the detector, better detection conditions are achieved. The aqueous mobile phase (0.4 ml/min) for the acid system contains citric acid 14 mM, sodium citrate 10 xnM, MeOH 15% (v/v) and EDTA 0.1 xnM. Detection potentials relative to Ag/AgCl reference are 0.45 and 0.60V. The aqueous ion pairing mobile phase (0.5 ml/min) for the amine system contains citric acid 5 mM, sodium citrate 10 mM, MeOH 9% (v/v), MeCN 10.5% v/v), decane sulfonic acid 0.45 mM, and EDTA 0.1 mM. Detection potentials relative to Ag/AgCl reference are 0.45 and 0.65V.

PCR

The following methods were used for the data shown in Fig. 3, Fig. 13, and Fig. 16:

Total RNA is prepared by the guanidin isothiocyanate method (Chomczynski, 1987} . RNA pellets are solved in MQ water and stored at -80°C. The sample concentration is determined spectrophotometrically by a NanoDrop D-1000. A quality indicator number and an integrity number of r-RNA are measured with an Experion (Bio-Rad) on random samples. Ά two-step reversed transcription is performed by using a Superscript III kit (Invitrogen) . 1 ug of total RNA is reversed transcribed with 5 μΐ 2x RT Reaction Mix, 1 μΐ RT Enzyme Mix, volume adjusted to 10 μΐ with OEPC-treated water. 1 U of E.coli R ase H is added. cDNA is diluted 40 times and stored at -20°C.

Three sequences (one gene of interest and two reference genes) are amplified together in a triplex PCR- reaction. For real-time PCR measurements: 5 μΐ of the cDNA reaction is amplified in a 20 μΐ reaction mixture containing 10 μΐ Quanta buffer, 3.5 μΐ Q, 0.15 uM of each primer and 0.1 uH of each probe. Real-time PCR is measured on CFX96 (Biorad) using the following settings for all genes: 3 min pre-incubation at 95 degrees C followed by 40 cycles of denaturation at 95 degrees C for 15s, annealing and elongation at 60 degrees C for 1 minut.

Reference genes are HPRT and cyclophilin.

The primer and probe sequences are as follows for measuring of arc:

Activity-regulated gene (Arc) (Accession Number U19866)

Sense: 5'- GGA GTT CAA GAA GGA GTT TC-3'

Antisense: 5'- CCA CAT ACA GTG TCT GGT A -3' Probe: CCG CTT ACG CCA GAG GAA CT

Dye: 5'FAM

Quencher : 3 ¹ BHQ1

Product size: 149

Hypoxantine phosphoribosyl transferase (HPRT) (Accession Number AF001282)

Sense: 5'- AGG GAT TTG AAT CAT GTT TG -3'

Antisense: 5'- CTG CTA GTT CTT TAC TGG C -3' Probe: TGT AGA TTC AAC TTG CCG CTG TC

Dye: 5'HEX Quencher: 3 ¹ BHQ1

Product size: 121

Cyclophilln A (Accession Number M19533)

Sense: 5'- CTG GAC CAA ACA CAA ATG-3 '

Antisense: 5'- ATG CCT TCT TTC ACC TTC -3'

Probe: T G CCA TCC AGC CAC TCA GT

Dye: 5 'Texas red

Quencher: 3 ' BHQ2

Product size: 100

Correct PCR products are confirmed by agarose gel electroforesis (2%) PCR products are purified with PCR purification kit from Qiagen (Valencia, CA, USA) . All genes are sequenced at MWG, Germany. The amounts of gene of interests are normalised with the two reference genes HPRT and cyclophilln A.

For the data shown in Fig 6, the reverse transcription and PCR were performed as follows:

Reversed transcription is performed by using a

ThermoScript kit (Invitrogen) . lug of total RNA is reverse transcribed with 25 pmol oligo (dT) , 62.5 ng random hexamers, 7.5U Thermoscript RT, 10U RNaseOut, 2μ1 5x cDNA Synthesis buffer, lmM dNTP, 0.05 M DTT, adjust volume to 10 μΐ with DEPC- reated water. Then cDNA is diluted 40 times and stored at -20°C.

For real-time singleplex PCR measurements: 0.7 μΐ of the cDNA reaction is amplified in a 25 μΐ reaction mixture containing 1 x per buffer, 0.2 mM dNTP, 3.7 mM MgCl2, 0.15 mM SYBR green, 0.4 uH of primer and 1 U Taq polymerase. Realtime PCR is measured on Icycler (Biorad) using the following settings for all genes: 60s pre-incubation at 95°C followed by 40 cycles of denaturation at 95°C for 20 s, annealing at 56°C for 20 s, elongation at 72°C for 30 s.

Analysis of Arc mRNA: dose-response and interaction studies for Tetrabenazine, Pridopidine, and haloperidol

Total RNA was prepared by the guanidine isothiocyanate method (Schaefer 1984). RNA pellets were dissolved in ultrapure water and stored at -80°C. RNA concentration was determined spectrophotometrically using a NanoDrop ND-1000 (Thermo Scientific, Waltham, Massachusetts, USA) . A quality indicator number and an integrity number of ribosomal RNA were determined for random samples using an Experion electrophoresis system (Bio-Rad Laboratories, Hercules, California, USA) . Reverse transcription was performed using a Superscript III kit or a ThermoScript kit {both from Life Technologies Europe BV, Stockholm, Sweden} . For Tetrabenazine dose-response and interaction studies, 1 ug RNA was reverse-transcribed with 5 μΐ 2x RT Reaction Mix and 1 ul RT Enzyme Mix (Superscript III kit); for studies with Pridopidine and haloperidol, 1 ug RNA was reverse-transcribed using a ThermoScript kit with 25 pmol oligo(dT), 62.5 ng random hexamers, 7.5 U ThermoScript reverse transcriptase, 10 U RNaseOut, 2 μΐ 5x cDNA Synthesis Buffer, 1 mM dNTPs and 0.05 M dithiothreitol . In all studies, cDNA volume was adjusted to 10 μΐ with diethylpyrocarbonate-treated water. Escherichia coli RNase H (1 U) was added, then cDNA was diluted 40 times and stored at -20°C.

cDNA of Arc and two reference genes, hypoxanthine- guanine phosphoribosyltransferase (HPRT) and cyclophilin A, was amplified by real-time PCR in either a triplex reaction (Tetrabenazine studies) or three singleplex reactions (studies with Pridopidine and haloperidol) . For the triplex real-time PCR, 5 μΐ cDNA was amplified in a 20 μΐ reaction mixture containing 10 μΐ Quanta buffer (Quanta Biosciences

Inc., Gaithersburg, Maryland, USA), 3.5 μΐ ultrapure water, 0.15 uM of each primer and 0.1 uM of each probe (the primer and probe sequences used are detailed in Table 3) . Products of the triplex real-time PCR were detected on a CFX96 system (Bio-Rad Laboratories, Hercules, California, USA) using the following settings for all genes: 3 minutes pre-incubation at 95°C, followed by 40 cycles of denaturation at 95°C for 15 seconds, and annealing and elongation at 60°C for 1 minute. For singleplex real-time PCR measurements, 0.7 μΐ cD A was amplified in a 25 μΐ reaction mixture containing 1* PCR buffer, 0.2 mtf dNTPs, 3.7 mM MgCl ₂ , 0.15 mH SYBR Green, 0.4 μΜ of primer (Table 2) and 1 U Tag polymerase. An Icycler detection system (Bio-Rad Laboratories, Hercules, California, USA) was used, with the following settings for all genes: 60 seconds pre-incubation at 95°C, followed by 40 cycles of denaturation at 95°C for 20 seconds, annealing at 56°C for 20 seconds, elongation at 72°C for 30 seconds. Correctly sized PCR products were confirmed by electrophoresis in agarose gel (2%); the products were then purified with a PCR purification kit from Qiagen (Valencia, CA, USA) . All genes were sequenced at M G Biotech (Ebersberg, Germany) . The quantity of Arc mRA was normalized to those of the two reference genes by a standard curve constructed for every gene using six serial four-fold dilutions of purified PCR products.

Primers :

Hypoxantine phosphoribosyl transferase (HPRT) (Accession Number AF001282)

Sense: 5 ' -GGC CAG ACT TGT TGG ATT TG-3'

Antisense: 5'-CCG CTG TCT TTT AGG CTT TG-3'

Cyclophilin A (Accession Number M19533) Sense: 5'-GTC TCT TTT CGC CGC TTG CT-3 ' Antisense: 5' -TCT GCT GTC TTT GGA ACT TTG TCT G-3'

Activity-regulated gene (Arc) (Accession Number U19866)

Sense: 5'- GTC CCA GAT CCA GAA CCA CA-3'

Antisense: 5'- CCT CCT CAG CGT CCA CAT AC-3'

Initial DNA amounts are quantified by a standard curve constructed for every gene using 6 serial 4-fold dilutions of purified PCR products.

For the data shown in Fig. 10, the same methods were applied as for the data in Fig. 6, except that the PCR was run on a MylQ thermal cycler (Biorad) . Discussion of Examples:

It was demonstrated that Pridopidine reversed the behavioural inhibition induced by Tetrabenazine. This effect was not shared by haloperidol, which decreased locomotor activity in Tetrabenazine treated animals. The interaction experiments further showed that both Pridopidine and haloperidol retained their characteristic neurochemical effects, ie increases in striatal DOPAC, when co-administered with Tetrabenazine. Likewise, the accompanying increases in striatal arc mRNA levels induced by Pridopidine and haloperidol were maintained in the interaction experiments with Tetrabenazine.

In addition to locomotor depression and increased striatal DOPAC levels, Tetrabenazine produced a dose-dependent decrease in striatal dopamine levels, which was not affected by co-administration of Pridopidine or haloperidol. Moreover, Tetrabenazine produced a dose-dependent increase in frontal cortex Arc mRNA levels. This effect was counteracted in a dose-dependent manner by Pridopidine, but not by haloperidol. Pridopidine counteracted behavioural depression induced by Tetrabenazine. Consistent with previous data both Tetrabenazine and haloperidol were distinctly inhibitory on spontaneous locomotor activity (Satou 2001, Schaefer 1984), whereas Pridopidine displayed no such effects. This lack of inhibitory effects on spontaneous locomotor activity in rats is part of the characteristic pharmacological profile of Pridopidine (Ponten 2010).

The pharmacological effect of Pridopidine at dopamine D2 receptors was present also when co-administered with Tetrabenazine. The neurochemical analysis demonstrated that all three compounds tested produced a dose dependent increase in striatal DOPAC, reaching around 250-300% of control levels at the top doses applied, in line with previous results. An increase in striatal DOPAC is a common feature of dopamine D2 antagonists, as well as compounds in general producing a reduced tone at central dopamine D2 receptors, including partial agonists with low intrinsic activity, and monoamine depleting drugs (Jordan, 2004; Roffler-Tarlov 1971) . The increase seen in striatal DOPAC thus represents a core pharmacological effect of each of the compounds tested. In the interaction experiments, both haloperidol and Pridopidine produced an additional increase in striatal DOPAC, when coadministered with Tetrabenazine. This strongly suggests that the primary effect of Pridopidine and haloperidol was still present in partially monoamine depleted rats. Furthermore, despite the fact that Pridopidine reversed the locomo or- suppressant effect of Tetrabenazine when they were coadministered, the decrease in tissue levels of dopamine induced as a signature effect of Tetrabenazine was unaffected by Pridopidine, suggesting that it did not abolish the pharmacological effects of Tetrabenazine as such. .

Overall, the typical neurochemical effects of all three compounds on DOPAC, but also dopamine levels were present throughout the studies indicating that the core effects of each compound on dopaminergic transmission were retained.

The increased Arc mRNA in cortex by Pridopidine co- treatment may help to explain reversal of etrabenazine induced locomotor depression. As an additional biomarker of relevance especially for the differentiation of Pridopidine and haloperidol, Arc mRNA was measured in the frontal cortex and the striatum. Arc is an early gene associated with synaptic activation and MDA receptor signalling, and has previously been reported to increase in the striatum in response to several dopamine D2 antagonists, as well as dopaminergic stabilizers. However there are no previous reports on the effects of Tetrabenazine on Arc gene expression. As demonstrated in the examples, Tetrabenazine induced a significant increase in striatal Arc. Albeit somewhat smaller in magnitude than the effects of Pridopidine and haloperidol, this effect may be related to reduced striatal dopamine transmission also in Tetrabenazine treated animals. As was the case for DOPAC, both Tetrabenazine and Pridopidine produced similar effects on striatal Arc in naive as in Tetrabenazine treated rats.

In the frontal cortex, Tetrabenazine reduced Arc gene expression dose dependently, with significant effects at and above the dose used for the interaction experiments. The dose response studies of Pridopidine and haloperidol, demonstrated a dose dependent increase in frontal cortex Arc gene expression by Pridopidine, but no effects of haloperidol. The ability of Pridopidine to increase frontal cortex Arc gene expression was also evident in Tetrabenazine treated rats. Thus, this pharmacological effect, which distinguishes Pridopidine from haloperidol and other classic dopamine D2 antagonists, was maintained upon partial monoamine depletion. It is conceivable that it represents some degree of cortical synaptic activation that could contribute to the ability of Pridopidine to counteract the behavioural inhibition in Tetrabenazine treated rats. In support of this interpretation, Pridopidine has been shown to increase firing of spontaneously active pyramidal cells in the frontal cortex.

While the examples clearly indicate that the effects of Pridopidine are retained when Pridopidine is coadministered with Tetrabenazine, the combination of Pridopidine and Tetrabenazine did not give rise to any signs of adverse effects, in contrast, combining haloperidol and Tetrabenazine produced pronounced behavioural depression, which would suggest a risk of excessive anti-dopaminergic motor side effects with such a combination in humane, in line with current recommendations on caution regarding co-treatment of patients with Huntington's disease with Tetrabenazine and neuroleptic drugs.

Summary of Dopamine levels in striatum

The effects of the different treatments on striatal tissue levels of dopamine are given in Table 1. Tetrabenazine induced a dose dependent reduction in striatal dopamine. At the dose used in the interaction experiments, 0.64 mg/kg, Tetrabenazine reduced striatal dopamine significantly, reaching approximately 50% of vehicle control group mean, throughout the studies performed. Pridopidine and haloperidol both produced smaller decreases in striatal dopamine, at the highest doses tested. In the interaction experiments, the effect of Tetrabenazine on striatal dopamine was essentially unaffected by cotreatment with Pridopidine or haloperidol.

In summary, Pridopidine reversed the behavioural inhibition induced by the monoamine depleting compound Tetrabenazine, while retaining Pridopidine' s core neurochemical effects related to dopamine D2 receptor antagonism. Thus, the locomotor depressant effects of Tetrabenazlne are alleviated by Pridopidine, despite that the tone at striatal dopamine D2 receptor is further reduced when Pridopidine is administered in addition to Tetra enazine. Pridopidine also reversed the decrease in frontal cortex Arc gene expression induced by Tetrabenazine. Tentatively, this reflects an activation of cortical neuronal activity that might contribute to the locomotor stimulatory effects of Pridopidine in partially monamine depleted, hypoactive rats.

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FDA Label for XENAZINE (Tetrabenzine) 07/06/2011