WO2010060742A1

WO2010060742A1 - Combination of bifeprunox and an antipsychotic drug with d2/5-ht2a receptor antagonistic activity for treating cns disorders

Info

Publication number: WO2010060742A1
Application number: PCT/EP2009/064453
Authority: WO
Inventors: Christina Kurre Olsen; Jørn ARNT
Original assignee: H Lundbeck AS; Solvay Pharmaceuticals BV
Current assignee: H Lundbeck AS; Abbott Healthcare Products BV
Priority date: 2008-11-03
Filing date: 2009-11-02
Publication date: 2010-06-03
Anticipated expiration: 2011-05-03

Abstract

The present invention relates to (a pharmaceutical composition comprising) a combination of bifeprunox (a D₂/5-HT_1A receptor ligand) and at least one D₂/5-HT_2A receptor antagonistic ligand and pharmaceutically acceptable auxiliaries for use in the treatment of various CNS disorders, particularly psychotic disorders like schizophrenia and related psychiatric conditions, including bipolar disorder, bipolar depression, mania and atypical depression.

Description

COMBINATION OF BIFEPRUNOX AND AN ANTIPSYCHOTIC DRUG WITH D2/5-HT_2A RECEPTOR ANTAGONISTIC ACTIVITY FOR TREATING CNS DISORDERS

The present invention relates to a pharmaceutical composition comprising a combination of Bifeprunox (a D2/5-HT1A receptor ligand) and an antipsychotic drug having D2/5-HT2A receptor antagonistic activity and the use of said composition for treating central nervous system (CNS) disorders.

BACKGROUND OF THE INVENTION

CNS disorders, particularly psychotic disorders like schizophrenia and related psychiatric disorders, including bipolar disorder, bipolar depression, mania and atypical depression are a major area of unmet clinical need. As an example, schizophrenia, which is a traumatic and debilitating disorder, is typically characterised by thought disorder, delusional perception and hallucinations (collectively termed the positive symptoms), accompanied by emotional and motor disturbances. Other features of lethargy, apathy, emotional blunting (the negative symptoms) and cognitive impairment generally appear in later stages of the disease. It is estimated that 24 million people worldwide suffer from schizophrenia and that 2-10 people in every 1000 will suffer from the illness at some point in their lives (World Health Organisation, 2004; see www.who.int/mediacentre/factsheets/fs265/en/; National Institute for Clinical Excellence (NICE), UK, 2002; see www.nice.org.uk/page.aspx?o=32929).

The most important drugs used to treat these CNS disorders are the antipsychotics. Most of the currently available can be divided into 2 subgroups, i.e. the "1st generation" or "typical" antipsychotics, and the "2nd generation" or "atypical" antipsychotics. Examples of typical antipsychotics include the well known drugs haloperidol, chlorpromazine, trifluperazine and cis-flupenthixol that are all dopamine D₂ receptor antagonists. The 2nd generation or atypical antipsychotics are differentiated from the 1st generation D₂ antagonist antipsychotics by combining this pharmacological mechanism with high potency 5-HT₂A antagonism. Examples of atypical antipsychotics include clozapine, olanzapine, risperidone, ziprasidone, quetiapine, sertindole, iloperidone, asenapine, blonanserin, cariprazin, lurasidone, and paliperidone. Despite the fact that the 2nd generation antipsychotics are much less prone to cause severe extrapyramidal side-effects, i.e. pseudo-Parkinsonism, dystonia, and tardive dyskinesias, motor disturbances are still relatively frequent with the 2nd generation antipsychotics. Moreover, these drugs nonetheless carry a significant side-effect burden, causing hyperprolactinaemia, sexual dysfunction, weight gain, dyslipidaemia, Type 2 diabetes and postural hypotension. In addition to serious side-effects that limit dosing and lead to poor compliance, many patients suffer from residual symptoms of their disorder that prevent them from functioning normally, and also, several domains of schizophrenia and related psychotic disorders are poorly treated by the atypical antipsychotics, particularly the negative and cognitive symptoms.

A new generation of antipsychotics has recently been conceived which combine attenuation of dopamine D₂ receptor function by (low efficacy) partial agonism together with increased 5-HT_IA receptor function through 5-HT1A partial or full agonism. It is now well established in the art that molecules that are D2/5-HT1A receptor ligands, which combine 5-HT_IA receptor agonism with (low efficacy) D₂ partial agonist activity are effective as monotherapy in the treatment of various CNS disorders, particularly psychotic disorders like schizophrenia and related psychiatric disorders, including bipolar disorder, bipolar depression, mania and atypical depression, with a diminished impact on extrapyrimidal symptoms. The term "ligand" is used to describe any molecule that has affinity for the binding sites on a range of biological proteins, e.g. receptors, ion channels, transporters and enzymes, without reference to functionality. Thus, "D₂/5-HT_IA receptor ligands" are molecules with affinity for both D₂ and 5-HT_IA receptors, and these molecules are (low efficacy) partial agonists of D₂ receptors and either high efficacy partial or full agonists at 5-HT_IA receptors. Examples of D₂/5-HT_IA ligands with proven clinical efficacy include, amongst others, bifeprunox and aripiprazole. Bifeprunox and aripiprazole are both active in animal models that are predictive of antipsychotic activity in man, e.g. the rat conditioned avoidance response (CAR) paradigm in which bifeprunox and aripiprazole have been shown to be active. Although improvements in therapy have been made over time, in the treatment of CNS disorders there is still a need for more effective drugs having less side effects. DESCRIPTION OF THE INVENTION

According to the present invention, it has been found that in the treatment of certain CNS disorders, when bifeprunox is combined with a D2/5-HT2A receptor antagonist, "atypical" or "2nd generation", antipsychotic drug, this combination yields unexpected clinical benefits by providing enhanced antipsychotic efficacy, as predicted by the inhibition of CAR in rat models. At the same time, also a reduction of the extrapyramidal symptoms (EPS) liability (side-effects) was observed, as predicted by the induction of catalepsy in rat models. This finding is especially unexpected because when bifeprunox was combined with an example of a 1st generation antipsychotic (haloperidol), that combination did not deliver the improved clinical benefit in the CAR model of antipsychotic efficacy. On the contrary, the bifeprunox + haloperidol combination in particular delivered less efficacy than haloperidol alone. It was found that bifeprunox shows benefits over aripiprazole, although these compounds have a similar pharmacological profile. Therefore, an embodiment of this invention relates to a pharmaceutical composition comprising a combination of bifeprunox and at least one D2/5-HT2A receptor antagonistic ligand and pharmaceutically acceptable auxiliaries.

In another embodiment of this invention the D2/5-HT2A receptor antagonistic ligand is selected from clozapine, olanzapine, risperidone, ziprasidone, quetiapine, sertindole, iloperidone, asenapine, blonanserin, cariprazin, lurasidone and paliperidone. A preferred D2/5-HT2A receptor antagonistic ligand is risperidone.

A further embodiment of this invention relates to a method for treating a patient suffering from or susceptible to a CNS disorder, in particular selected from psychotic disorders like schizophrenia and related psychiatric conditions, bipolar disorder, bipolar depression, mania and atypical depression, comprising administering to said patient an effective amount of a first component which is bifeprunox in combination with an effective amount of a second component which is at least one D2/5-HT2A receptor antagonistic ligand. In one embodiment, the sequence of administration of the first and second component may be in any consecutive, sequential order, whereas in another embodiment they may be administered concomitantly. In still another embodiment, bifeprunox is administered prior to the D₂/5 -HT₂A receptor antagonistic ligand risperidone.

Bifeprunox and the D₂/5 -HT₂A receptor antagonistic ligand are preferably used in a pharmaceutical formulation that is adapted for oral administration. In an embodiment of this invention, bifeprunox and the D2/5-HT2A receptor antagonistic ligand may conveniently be provided in a package, e.g. a blister package, comprising a first pharmaceutical composition comprising bifeprunox and a second pharmaceutical composition comprising at least one D2/5-HT2A receptor antagonistic ligand. In one embodiment, the package is adapted for sequential administration of the first and second component (in any consecutive, sequential order), whereas in another embodiment the package is adapted for concomitant administration of the first and second component. Also within the ambit of this invention is a pharmaceutical composition as a discrete dosage unit form comprising an effective dose of both bifeprunox and at least one D2/5-HT2A receptor antagonistic ligand, and a package, e.g. a blister package, comprising said pharmaceutical composition.

In one embodiment, a dosage unit of a pharmaceutical composition of the present disclosure comprises bifeprunox in a dosage range of about 0.05 to about 40 mg, about 0.75 to about 35 mg, about 0.1 to about 30 mg or about 0.125 to about 20 mg (calculated on the free base form) per dosage unit. Preferably, a treatment dosage unit comprises about 5 mg to 30 mg of bifeprunox mesylate. In another embodiment, a dosage unit of a pharmaceutical composition of the present disclosure comprises risperidone as the D2/5-HT2A receptor antagonistic ligand in a dosage range of about 0.05 to about 40 mg, about 0.75 to about 35 mg, about 0.1 to about 30 mg or about 0.125 to about 20 mg per dosage unit. Preferably, a treatment dosage unit comprises about 1 mg to 10 mg of risperidone.

In a further embodiment of the present invention, the patient is treated for a long term, in particular three months, six months, a year, or longer.

As used herein, the term "bifeprunox" includes the active ligand 7-[4-([l,l'- biphenyl]-3-ylmethyl)-l-piperazinyl]-2(3H)-benzoxa-zolone (INN bifeprunox), having the general formula

its N-oxide and pharmaceutically acceptable salts, solvates and hydrates thereof. When the N-oxide is considered, the amount to be used in milligrams is the same amount as the amount the person skilled in the art would select for bifeprunox without the oxide. In addition, pharmaceutically acceptable salts of bifeprunox or its N-oxide may be obtained using standard procedures well known in the art, for example, by mixing a compound of the present invention with a suitable acid, for instance an inorganic acid or an organic acid.

A hydrochloric acid salt of bifeprunox is described in WO97/36893 and a monomethanesulfonate salt of bifeprunox is described WO02/066449 (7-[4-([1,T- biphenyl]-3-ylmethyl)- 1 -piperazinyl]-2(3H)-benzoxazolone monomethanesulfonate, INN bifeprunox mesylate). In addition, in WO 2005/016898 is described as different crystalline forms of bifeprunox mesylate, in particular the alpha crystal form. In an embodiment of this invention, bifeprunox mesylate in the alpha form is the preferred bifeprunox compound. The N-oxide of bifeprunox is described in WO 2007/023141. Bifeprunox (earlier known as DU 127090) binds to dopamine U2-like receptors and 5-HTi_A receptors; it is a partial agonist at dopamine D2/3 receptors and also a partial agonist at serotonin 5-HT_IA receptors. See, e.g., Feenstra et al, WO 97/36893; Van Vliet et al., 2000, J Eur Coll Neuropsychopharmacology (ECNP) 10(3), S294; Feenstra et al., 2001, Bioorg. Med. Chem. Lett 11, 2345-2349; Feenstra et al., 2002, Drugs of the Future 27(Suppl. A); Hesselink et al., 2003, Eur J Neural 10, 2151).

Bifeprunox as monotherapy has been suggested to be useful for treatment of several diseases in the central nervous system. For instance in WO08025780 Al, and similarly in WO08/025781 Al, it is disclosed that "bifeprunox's affinity for both the dopamine D₂ and serotonin 5-HT_IA receptors makes it useful for the treatment of schizophrenia and other psychotic disorders. For example, Bifeprunox can be of value for the treatment of affections or diseases of the CNS caused by disturbances in either the dopamine or serotonergic systems, such as Parkinson's disease, aggression, anxiety disorders, autism, vertigo, depression, bipolar disorder, disturbances of cognition or memory, and further for example, schizophrenia and other psychotic disorders".

In WO08025780 Al a suitable titration schedule is described for safe and effective initiation of the treatment with bifeprunox to reduce undesirable adverse events such as nausea, vomiting and orthostatic hypertension which can occur during the initiation of treatment.

In the present context the terms "treatment" and "treating" means the management and care of a patient for the purpose of combating a disease, disorder or condition. The term is intended to include the full spectrum of treatments for a given disease, disorder or condition as described herein from which the patient is suffering, such as administration of the active compound to alleviate or relieve the symptoms or complications, to delay the progression of the disease, disorder or condition, to alleviate or relieve the symptoms and complications, and/or to cure or eliminate the disease, disorder or condition as well as to prevent the disease, disorder or condition, wherein prevention is to be understood as the management and care of a patient for the purpose of combating the disease, condition, or disorder and includes the administration of the active compound to prevent the onset of the symptoms or complications. Nonetheless, prophylactic (preventive) and therapeutic (curative) treatments are two separate aspects of the invention. The patient to be treated is preferably a mammal, in particular a human being.

As used herein, the phrase "effective amount" when applied to a compound of the invention, is intended to denote an amount sufficient to cause an intended biological effect. The phrase "therapeutically effective amount" when applied to a compound of the invention is intended to denote an amount of the compound that is sufficient to ameliorate, palliate, stabilize, reverse, slow or delay the progression of a disease, disorder or condition state, or of a symptom of the disease, disorder or condition.

The combination of the present invention may be administered in any suitable way, e.g. orally or parenterally. The preferred route of administration is the oral route. Mixed with pharmaceutically suitable auxiliaries, e.g. as described in the standard reference "Remington, The Science and Practice of Pharmacy" (21^st edition, Lippincott Williams & Wilkins, 2005, see especially Part 5: Pharmaceutical Manufacturing), the active ingredients (i.e. a D2/5-HT1A receptor ligand; a D2/5-HT2A receptor antagonist) of the present combination, may be compressed into solid dosage units, such as pills or tablets, or be processed into capsules or suppositories. By means of pharmaceutically suitable liquids the compounds can also be applied in the form of a solution, suspension or emulsion. In the preparation of the compositions of the present disclosure, the active ingredients may be mixed with solid, powdered ingredients, such as lactose, saccharose, sorbitol, mannitol, starch, amylopectin, cellulose derivatives, gelatin, or another suitable ingredient, as well as with disintegrating agents and lubricating agents. The mixture may then be processed into granules, pressed into tablets, and/or any other known pharmaceutical form such as suppositories and/or suspensions.

Soft gelatin capsules may be prepared containing a composition comprising a mixture of the active ingredients of the invention, vegetable oil, fat, or other suitable vehicle for soft gelatin capsules. Hard gelatin capsules may contain granules of the active ingredients. Hard gelatin capsules may also contain the active ingredients in combination with solid powdered ingredients such as lactose, saccharose, sorbitol, mannitol, potato starch, corn starch, amylopectin, cellulose derivatives or gelatin.

In addition, compositions of the present disclosure can comprise at least one pharmaceutical excipient. Non-limiting examples of suitable excipients include suspending agents, humectants, solubilizers, surfactants, preservatives, antioxidants , anti-caking agents, coating agents, chelating agents, stabilizers, antimicrobial agents, antifungal or antibacterial agents, isotonic agents, thickening agents, flavoring agents , anti-foaming agents, disintegrants, flow aids, lubricants, adjuvants, colorants, diluents, moistening agents, preservatives, carriers, binders, diluents, disintegrating agents, glidants and water insoluble or water soluble lubricants or lubricating agents.

By "pharmaceutically acceptable" it is meant that the carrier, diluent or excipient must be compatible with the other ingredients of the formulation and not deleterious to the recipient thereof.

In an embodiment of the invention, a pharmaceutical package, or kit, is provided comprising one or more containers filled with one or more pharmaceutical compositions of the invention. Associated with such container(s) can be various written materials such as instructions for use, or a notice in the form prescribed by a governmental agency regulating the manufacture, use or sale of pharmaceuticals products, which notice reflects approval by the agency of manufacture, use, or sale for human or veterinary administration.

LEGENDS TO THE FIGURES

Figure 1 : Protocol and time schedule (Scheme 1) for administration of bifeprunox before haloperidol or risperidone in the CAR test. Figure 2: Protocol and time schedule (Scheme 2) for administration of bifeprunox after haloperidol or risperidone in the CAR test.

Figure 3: Dose-response of risperidone alone, and in combination with bifeprunox on CAR in rats. Bifeprunox was administered 90 min before risperidone. Values are mean + s.e.m. (n = 7) percentage avoidances compared to preceding pre-test, each animal serving as their own control. Statistical analysis was performed by two-way ANOVA followed by Student-Newman-Keuls post hoc test (* P <0.05, ** P <0.01, ***P<0.001).

Figure 4: Dose-response of risperidone alone, and in combination with bifeprunox on CAR in rats. Bifeprunox is administered 30 min after risperidone. Values are mean + s.e.m. (n = 8 - 16) percentage avoidances compared to preceding pre-test, each animal serving as their own control. Statistical analysis was performed by two-way ANOVA followed by Student-Newman-Keuls post hoc test (* P <0.05, ** P <0.01, ***P<0.001).

Figure 5: Dose-response of haloperidol alone, and in combination with bifeprunox on CAR in rats. Bifeprunox was administered 90 min before haloperidol. Values are mean + s.e.m. (n = 6 - 23) percentage avoidances compared to preceding pre-test, each animal serving as their own control. Statistical analysis was performed by two-way ANOVA followed by Student-Newman-Keuls post-hoc test (* P <0.05, ** P <0.01, ***P<0.001).

Figure 6: Dose-response of haloperidol alone, and in combination with bifeprunox on CAR in rats. Bifeprunox is administered 30 min after haloperidol. Values are mean + s.e.m. (n = 7 - 23) percentage avoidances compared to preceding pre-test, each animal serving as their own control. Statistical analysis was performed by two-way ANOVA followed by Student-Newman-Keuls post hoc test (* P <0.05, ** P <0.01, ***P<0.001).

Figure 7: Protocol and time schedule (Scheme 3) for administration of aripiprazole before haloperidol or risperidone in the CAR test. Figure 8: Dose-response of risperidone alone, and in combination with aripiprazole on CAR in rats. Aripiprazole was administered 30 min before risperidone. Values are mean + s.e.m. (n = 6 - 7) percentage avoidances compared to preceding pre-test, each animal serving as their own control. Statistical analysis was performed by two-way ANOVA followed by Student-Newman- Keuls post hoc test (NS = non-significant, * P <0.05, ***P<0.001).

Figure 9: Dose-response of haloperidol alone, and in combination with aripiprazole on CAR in rats. Aripiprazole was administered 30 min before haloperidol. Values are mean + s.e.m. (n = 5 - 6) percentage avoidances compared to preceding pre-test, each animal serving as their own control. Statistical analysis was performed by two-way

ANOVA followed by Student-Newman- Keuls post-hoc test (NS = non-significant,

** P <0.01, ***P<0.001).

Figure 10: Protocol and time schedule (Scheme 4) for administration of bifeprunox before haloperidol or risperidone in the catalepsy test.

Figure 11 : Protocol and time schedule (Scheme 5) for administration of bifeprunox after haloperidol or risperidone in the catalepsy test.

Figure 12: Dose-response of risperidone alone and in combination with bifeprunox on catalepsy in rats. Bifeprunox was administered 90 min before risperidone. Values are mean + sem (n = 4) catalepsy score. Statistical analysis was performed by two-way ANOVA followed by Student-Newman-Keuls post-hoc test (* P <0.05, ** P <0.01, ***P<0.001).

Figure 13: Dose-response of risperidone alone and in combination with bifeprunox on catalepsy in rats. Bifeprunox was administered 90 min after risperidone. Values are mean + sem (n = 3 - 8) catalepsy score. Statistical analysis was performed by two-way ANOVA (** P <0.01, ***P<0.001).

Figure 14: Dose-response of haloperidol alone, and in combination with bifeprunox on catalepsy in rats. Bifeprunox was administered 90 min before haloperidol. Values are mean + s.e.m. (n=4-8) catalepsy score. Statistical analysis was performed by two- way ANOVA followed by Student-Newman-Keuls post hoc test (* P <0.05, ** P <0.01, ***P<0.001).

Figure 15: Dose-response of haloperidol alone and in combination with bifeprunox on catalepsy in rats. Bifeprunox is administered 90 min after haloperidol. Values are mean + s.e.m. (n=4-8) catalepsy score. Statistical analysis was performed by two-way ANOVA (* P <0.05, ***P<0.001).

Figure 16: Protocol and time schedule (Scheme 6) for administration of aripiprazole before haloperidol or risperidone in the catalepsy test.

Figure 17: Dose-response of risperidone alone and in combination with aripiprazole on catalepsy in rats. Aripiprazole was administered 30 min before risperidone. Values are mean + sem (n = 4) catalepsy score. Statistical analysis was performed by two-way ANOVA followed by Student-Newman-Keuls post-hoc test (NS = non-significant; * P <0.05, ***P<0.001).

Figure 18: Dose-response of haloperidol alone, and in combination with aripiprazole on catalepsy in rats. Aripiprazole was administered 30 min before haloperidol. Values are mean + s.e.m. (n = 4) catalepsy score. Statistical analysis was performed by two-way ANOVA followed by Student-Newman-Keuls post-hoc test (NS = non-significant, ***P<0.001).

The invention will be illustrated in the following non-limiting examples.

EXAMPLES

A. Conditioned avoidance responding (CAR)

The CAR paradigm

In the CAR paradigm, rats are placed in a shuttle-box and following the delivery of warning cues, i.e. a light and an audible tone, rats have to move to the other compartment of the apparatus within a fixed time interval ("avoidance"). If a rat fails to enter the other compartment of the shuttle-box after presentation of the light + tone cues, it is given a mild footshock which prompts it to cross into the other compartment ("escape"). If the rat is impaired by the test drug and it still fails to cross into the other compartment after the footshock has been administered, this result is termed an escape failure, and it indicates a non-specific attenuation of CAR responding, e.g. through the induction of sedation. Clinically effective antipsychotic drugs of all classes, ie 1^st, 2^nd, and new generation antipsychotics, all impair CAR without inducing escape failures. The CAR paradigm is widely used as a model to predict the efficacy of antipsychotic drug candidates (Wadenberg and Hicks, 1999, Neurosci Biobehav Rev 23:851-862).

Method:

Test substances: Bifeprunox and aripirazole were dissolved in 10% 2-hydroxy-propyl- β-cyclodextrin. Haloperidol was dissolved in saline to which was added a minimum amount of tartaric acid. Risperidone was dissolved in saline to which was added a minimum amount of diluted HCl acid. Compounds were administered subcutaneously (s.c.) in a volume of 5 ml/kg. All doses are presented as mg/kg active substance.

Subjects: Male Wistar rats (Harlan, Netherlands) weighing 200 g at the beginning of the test were used. Rats were housed under controlled laboratory conditions (temperature: 21±2 °C; humidity: 55±5 % relative) on a 12:12 h light-dark cycle (lights on at 06:00). The animals were kept on a restricted diet in order to keep them to 80% of their free-feeding weight. Water was available ad libitum.

Experimental procedure: Conditioned avoidance behaviour was assessed using four automated shuttle-boxes (42x16x20 cm) (ENV-OlOM, MED-Associates) each placed in a sound-attenuated chamber. The boxes were subdivided into two compartments by a partition with one opening. The position of the animal and movement from one compartment to the other was detected by 8 photocells sensitive to infrared light on each side of the dividing wall. Rats were trained to move into the adjacent compartment (response) within 10 sec upon presentation of the conditioned stimuli (tone and light) in order to avoid the appearance of the unconditioned stimulus, a 0.5 mA scrambled electric shock in the grid floor of 10 sec in maximal duration. The following behavioural variables were recorded: avoidance (response to conditioned stimuli within 10 sec) and escape failures (failure to respond to the unconditioned stimuli within 10 sec).

Rats were habituated to the shuttle-box 3 min before each test session. During training, each test session consisted of 30 trials with inter-trial intervals varied at random between 20 and 30 sec. Training was carried out 5 days/week until the animals had avoidance measures of >80% (24 trials) of the trials on three consecutive days. All experimental sessions consisted of 10 trials with inter-trial intervals varied at random between 20 and 30 sec.

Experimental design: Drug test was preceded by a pre-test (the day before). At least 3 days elapsed between drug injections to prevent cumulative drug effects. Vehicle-treated groups and drug-treated groups were run concurrently. Bifeprunox was administered 120 min prior to test whereas haloperidol and risperidone were either administered 30 min pretest (Scheme 1, Fig. 1) or 150 min in pretest (Scheme 2, Fig 2). Aripiprazole was administered 60 min prior to test, whereas haloperidol and risperidone were either administered 30 min pre-testing (Scheme 3, Fig. 7). Immediately after the test, tail blood samples were taken in order to perform exposure analysis.

Statistics: Data are presented as percentage compared to preceding pre-test, with each animal serving as their own control. Statistical analysis was performed on percentages avoidances and escape failures, respectively using two-way (treatment x dose) analysis of variance (ANOVA) followed by post-hoc Student-Newman-Keuls test. Results were considered statistically significant when P<0.05 and are expressed as means + s.e.m.

Results:

Bifeprunox in combination with risperidone The suppression of CAR behaviour is presented as the mean percentage of avoidances following bifeprunox administered alone or in combination with risperidone given either before risperidone in Figure 3 and after risperidone in Figure 4.

Administering bifeprunox (0.25 mg/kg) before risperidone (0.16 — 0.63 mg/kg) enhanced the effect of risperidone on CAR (Figure 3). A significant interaction between bifeprunox and risperidone treatment was found (F₃^₅ = 4.1, P = 0.011) using two-way ANOVA. Post-hoc analysis revealed significant suppression of CAR by either compound given alone and a significantly enhanced effect of a threshold dose of risperidone (0.16 mg/kg) following addition of bifeprunox (0.25 mg/kg).

Administering bifeprunox (0.25 mg/kg) after risperidone (0.31 - 2.5 mg/kg) resulted in an additive effect on CAR at some doses (Figure 4). A significant interaction between bifeprunox and risperidone treatment was found (F_4i94 = 6.4, P <0.001) using two-way ANOVA. Post-hoc analysis revealed significant suppression of CAR by either compound given alone and a significantly additive effect of risperidone (0.31 and 0.63 mg/kg) and bifeprunox (0.25 mg/kg).

As also shown in Figures 3 and 4, administration of bifeprunox either before or after risperidone did not alter its maximum effect in the CAR model.

Bifeprunox in combination with haloperidol

The suppression of CAR behaviour presented as the mean percentages of avoidances following bifeprunox (0.25 mg/kg) administered alone or in combination with haloperidol given before haloperidol is presented in Figure 5 and after haloperidol in Figure 6. Administering bifeprunox (0.25 mg/kg) before haloperidol (0.02 -

0.16 mg/kg) revealed that the effects of these 2 drugs in CAR are clearly not additive at any of the doses tested, and in addition bifeprunox prevented full suppression of CAR evoked by haloperidol (Figure 5). A significant interaction between bifeprunox and haloperidol treatment was found (F₄^ = 8.6, P <0.001) using two-way ANOVA. Post-hoc analysis revealed significant suppression of CAR by either compound given alone. However, the effect of the two highest doses (0.08 and 0.16 mg/kg) of haloperidol was significantly counteracted by co-administration of bifeprunox. Importantly, the efficacy of the combination of haloperidol + bifeprunox never exceeded the effect level of bifeprunox given alone (Figure 5). Similarly, administering bifeprunox (0.25 mg/kg) after haloperidol (0.04 -

0.31 mg/kg) did not result in a full suppression of CAR (Figure 6). A significant interaction between bifeprunox (0.25 mg/kg) and haloperidol treatment was found

(F_4jl37 = 11.8, P <0.001) using two-way ANOVA. Post-hoc analysis revealed significant suppression of CAR by either compound given alone. Although a significantly enhanced effect of a threshold dose of haloperidol (0.04 mg/kg) was observed following addition of bifeprunox, the overall effect did not exceed the effect level of bifeprunox given alone (Figure 6). Moreover, the effect of the highest dose of haloperidol (0.31 mg/kg) was significantly counteracted by co-administration of bifeprunox (Figure 6).

Aripiprazole in combination with risperidone

The suppression of CAR behaviour is presented in Figure 8 as the mean percentage of avoidances following aripiprazole administered alone or in combination with risperidone when aripiprazole was given 30 min before risperidone.

Administering aripiprazole (10.0 mg/kg) before risperidone (0.16 —

0.63 mg/kg) enhanced the effect of risperidone on CAR (Figure 8). A significant interaction between aripiprazole and risperidone treatment was found (F₃₁₄₁ = 9.17,

P < 0.001) using two-way ANOVA. Post-hoc analysis revealed significant suppression of CAR by either compound given alone and a significantly enhanced effect of a sub-threshold dose of risperidone (0.16 mg/kg) following addition of aripiprazole (10.0 mg/kg).

As also shown in Figure 8, administration of aripiprazole (10.0 mg/kg) before risperidone did not alter its maximum effect in the CAR model.

Aripiprazole in combination with haloperidol

The suppression of CAR behaviour is presented as the mean percentages of avoidances following aripiprazole (10.0 mg/kg) administered alone or in combination with haloperidol. Aripiprazole was given before haloperidol and the results are presented in

Figure 9. A significant interaction between aripiprazole and haloperidol treatment was found (F_3j38 = 12.5, P <0.001) using two-way ANOVA. Post-hoc analysis revealed significant suppression of CAR by either compound given alone. However, administering aripiprazole (10.0 mg/kg) before haloperidol (0.04 - 0.16 mg/kg) revealed that the effects of these 2 drugs in CAR were not additive at any of the doses tested. Thus, the effect of haloperidol + aripiprazole when given in combination did not exceed the effect level of aripiprazole given alone at the lowest dose of haloperidol, and the effect level of the combination did not exceed those of haloperidol given alone at the 2 higher doses of this 1^st generation antipsychotic (Figure 9).

B. Catalepsy

The catalepsy model of EPS

Antipsychotic drugs, particularly the 1st generation or typical antipsychotics, cause motor side-effects, as a result of profound blockade of D₂ receptors in the nigro-striatal system of the brain. The major extrapyramidal motor side-effects are rigidity, slowness of gait, akathisia, dystonia, and after prolonged therapy, tardive dyskinesia. The acute EPS evoked by the antipsychotic drugs is called pseudo-Parkinsonism because Parkinson's disease is also caused by a loss of dopaminergic function in the nigro-striatal system, only in this case, it is due to neurodegeneration rather than dopamine receptor blockade. Antipsychotic drugs cause EPS in animals and in rodents, the potency and severity of antipsychotics to cause these symptoms can be modelled by measuring how long rats or mice will maintain behaviourally abnormal positions, e.g. hanging on a vertical wire grid, sitting with their fore- and hind-paws crossed or with their front paws elevated on a bar.

Method:

Test substances: Bifeprunox and aripiprazole were dissolved in 10% 2-hydroxy- propyl-β-cyclodextrin. Haloperidol was dissolved in saline to which was added a minimum amount of tartaric acid. Risperidone was dissolved in saline to which was added a minimum amount of diluted HCl acid. Compounds were administered subcutaneously (s.c.) in a volume of 5 ml/kg. All doses are presented as mg/kg active substance.

Subjects: Male Wistar rats (Harlan, Netherlands) weighing 170-240 g were used. Rats were housed under controlled laboratory conditions (temperature: 21 ± 2 °C; humidity: 55 ± 5 % relative) on a 12:12 h light-dark cycle (lights on at 06:00). Food and water was available ad libitum.

Experimental procedure: Rats were placed in the middle of a vertical wire netting (50 x 50 cm). Mesh openings are (1 x 1 cm) and mesh diameter is 2 mm. The animals were considered cataleptic when they remained immobile during a period of 15 seconds and given a score 2. Rats, which did not move their paws, but showed head movements were given a score 1 whereas rats either moving around, showing muscle relaxation (i.e. passively sliding down) or active body or head movements were not considered as cataleptic and given a score 0. Prevention studies were performed by testing the rats every hour from 1 to 6 hrs after administration of either haloperidol or risperidone and from 2.5 to 7.5 hours following bifeprunox (Scheme 4, Fig. 10). Reversal studies were performed slightly differently. Catalepsy score was assessed every hour from 2 to 6 hrs after administration of either haloperidol or risperidone and 0.5 to 4.5 hours following bifeprunox (Scheme 5, Fig. 11). Prevention studies were performed by testing the rats every hour from 1 to 6 hrs after administration of either haloperidol or risperidone and from 2.0 to 7.0 hours following aripiprazole (Scheme 6, Fig. 16).

Statistics: Data are presented as mean number of catalepsy scores during a test period where the maximum obtainable score for each rat is 12 in the prevention studies and 10 in the reversal studies. Statistical analysis was performed using two-way (treatment x doses) analysis of variance (ANOVA) or one-way ANOVA where appropriate followed by post-hoc Student-Newman-Keuls test. Results were considered statistically significant when P<0.05 and are expressed as means + s.e.m.

Results:

Bifeprunox in combination with risperidone

Figure 12 and Figure 13 show the induction of catalepsy following bifeprunox (0.25 mg/kg) administered alone or in combination with risperidone, when this D2/5-HT1A receptor partial agonist was given before and after risperidone, respectively.

Adding bifeprunox (0.25 mg/kg) before risperidone (2.5 - 10 mg/kg) reduced risperidone-induced catalepsy (Figure 12). A significant interaction between bifeprunox and risperidone treatment was found (F_3j31 = 4.5, P =0.012) using two-way ANOVA. Post-hoc analysis revealed that when given alone, only risperidone caused significant catalepsy compared with the vehicle-vehicle control group. Moreover, when bifeprunox was given before risperidone, a significant reduction of the catalepsy score was observed for the combination at the highest dose of risperidone (10 mg/kg).

Administering bifeprunox (0.25 mg/kg) after risperidone (1.25 - 10 mg/kg) did not significantly reduce or enhance risperidone-induced catalepsy (Figure 13). Two-way ANOVA revealed no significant interaction between bifeprunox and risperidone treatment (F_4j46 = 2.0, P =0.12), but significant main effects of both bifeprunox (F_{1 j4}6 = 13, P <0.001) and risperidone (F_4^46 = 22, P <0.001) were found.

Thus, when risperidone was given alone, it dose-dependently induced catalepsy in the rats. In this experiment, significant catalepsy was also seen when bifeprunox was given on its own (Figure 13); the magnitude of the effect being similar to that observed in the previous experiment (Figure 12), which just failed to reach statistical significance.

Bifeprunox in combination with haloperidol Figure 14 and Figure 15 reveal the induction of catalepsy following bifeprunox (0.25 mg/kg) administered alone or in combination with haloperidol, given either before or after haloperidol, respectively.

Administering bifeprunox (0.25 mg/kg) before haloperidol (0.16 - 1.3 mg/kg) reduced haloperidol- induced catalepsy (Figure 14). A significant interaction between bifeprunox and haloperidol treatment were found (F_4i63 = 5.2, P <0.011) using two-way ANOVA. Post-hoc analysis revealed that when given alone haloperidol dose-dependently induced catalepsy and bifeprunox also induced moderate catalepsy (Figure 14). Significant reductions of the catalepsy score induced by haloperidol (0.31 and 0.63 mg/kg) were observed when this 1st generation antipsychotic was given in combination with bifeprunox (Figure 14).

Administration of bifeprunox (0.25 mg/kg) after haloperidol (0.08 - 1.3 mg/kg) did not influence haloperidol- induced catalepsy (Figure 15). Two-way ANOVA revealed no significant interaction between bifeprunox and haloperidol treatment (FV₇ = 0.8, P =0.53), nor significant main effect of bifeprunox on catalepsy (Fi₁₄₇ = 3.9, P =0.056), whereas significant dose-dependent effect of haloperidol was observed (F₄,₄₇ = 0.80, P <0.001). Aripiprazole in combination with risperidone

Figure 17 shows the induction of catalepsy following aripiprazole (10.0 mg/kg) administered alone or in combination with risperidone, when this D2/5-HT1A receptor partial agonist was given before risperidone. Adding aripiprazole (10.0 mg/kg) before risperidone (2.5 - 10 mg/kg) increased the catalepsy induced by a low, but not high, doses of risperidone (Figure 17). A significant interaction between aripiprazole and risperidone treatment was found (^3,24 = 4.4, P = 0.013) using two-way ANOVA. Post-hoc analysis revealed that when given alone, only risperidone caused significant catalepsy compared with the vehicle- vehicle control group. When aripiprazole was given before risperidone, it had no influence on the catalepsy scores evoked by the 2 highest doses risperidone, ie 5.0 and 10 mg/kg. However, the combination of sub-threshold doses of aripiprazole (10.0 mg/kg) and risperidone (2.5 mg/kg) did produce significant (P < 0.05) catalepsy in the rats.

Aripiprazole in combination with haloperidol

Figure 18 shows the induction of catalepsy following aripiprazole (10.0 mg/kg) administered alone or in combination with haloperidol, when aripiprazole was given before haloperidol. Administering aripiprazole (10.0 mg/kg) before haloperidol (0.31 -

1.25 mg/kg) clearly had no effect on haloperidol- induced catalepsy (Figure 18). No significant interaction between aripiprazole and haloperidol treatment was found

(^3,24 = 0.287, NS) using two-way ANOVA. Post-hoc analysis revealed that when given alone aripiprazole (10.0 mg/kg) did not induce significant catalepsy when compared with the vehicle- vehicle control (Figure 18) and this finding is consistent with the result obtained in the previous experiment (Figure 17). Haloperidol caused a dose-dependent increase in catalepsy that was statistically different from the vehicle-vehicle control at all doses. The catalepsy scores evoked by each dose of haloperidol were not significantly influenced by co-administration of aripiprazole.

Discussion and conclusion

The clinical value of a drug in the treatment of a disease, e.g. schizophrenia, can be defined by the ratio of the improvement (reduction in severity of the disorder) to risk (side-effects caused). The range of doses where the benefit : risk ratio of a drug is positive defines "therapeutic window" where it can be used in patients. The results provided in the EXAMPLES are summarised in the Table below.

The results above demonstrate that the new generation D2/5-HT1A receptor partial agonist antipsychotics, exemplified by bifeprunox or aripiprazole, and a 2nd generation D2/5-HT2A receptor antagonist antipsychotic, exemplified by risperidone, delivered improved clinical benefit when given in combination. When compared to aripiprazole, bifeprunox unexpectedly showed a favourable side effect profile when given before risperidone.

In contrast, the results also demonstrate that the combination of a new generation D₂/5-HTi_A receptor antipsychotic, exemplified by bifeprunox or aripiprazole, and a 1st generation D₂ receptor antagonist antipsychotic, exemplified by haloperidol, delivered no such improved clinical benefit.

These findings are surprising and unexpected for the following reasons. 1. D₂ receptor antagonism is the common pharmacological mechanism though which the "1st generation" or "typical" antipsychotics and the "2nd generation" antipsychotics produce their therapeutic benefits. Both "1st" and the "2nd" generation antipsychotics are beneficial for treating various CNS disorders, particularly psychotic disorders like schizophrenia and related conditions, including bipolar disorder, bipolar depression, mania and atypical depression. Yet despite having D₂ receptor antagonism as a common mechanism for risperidone and haloperidol, bifeprunox and aripiprazole increased the efficacy of the "2nd generation" antipsychotic, risperidone, but these D₂/5-HT_IA receptor partial agonists fail to increase or actually reduced the efficacy of the "1st generation" or "typical" antipsychotic, haloperidol.

2. These findings do not reflect a dose-order pharmacokinetic effect because the unexpected therapeutic benefit of combining bifeprunox with risperidone was observed irrespective of whether this D₂/5-HT_IA receptor ligand was administered before or after risperidone. Similarly, the lack of benefit of combining bifeprunox with haloperidol was also observed when this D₂/5-HT_IA receptor ligand was administered both before and after the "1st generation" antipsychotic.

3. Bifeprunox was especially advantaged because depending on when it was dosed, this D₂/5-HT_IA receptor partial agonist synergistically increased the efficacy of risperidone, and in addition, it was also able to reduce the EPS liability of high doses of this "2nd" generation antipsychotic.

The pharmacological characteristic that differentiates the 1st generation and 2nd generation D₂ receptor antagonist antipsychotics is that the latter are also 5-HT₂A receptor antagonists. The defining features of the new generation D₂/5-HT_IA antipsychotics are that these compounds, including bifeprunox and aripiprazole, have either low efficacy D₂ partial agonist activity or D₂ antagonism and are 5 -HTi _A receptor agonists with either high partial or full intrinsic efficacy. The results presented in the EXAMPLES demonstrate that the unexpected clinical benefit of the combination of the present invention results from a surprising interaction between D₂ receptor antagonism and powerful 5-HT₂A receptor antagonism together with low efficacy D₂ receptor partial agonism and powerful 5-HT_IA receptor agonism. Furthermore, the unexpected beneficial effects demonstrated with risperidone can be extended to include other 2nd generation D2/5-HT2A receptor antagonist antipsychotics, including clozapine, olanzapine, quetiepine, ziprasidone, sertindole, iloperidone, asenapine, blonanserin, cariprazin, lurasidone and paliperidone.

In summary, the combination of the D2/5-HT1A ligand bifeprunox and a 2nd generation D2/5-HT2A receptor antagonist antipsychotic, exemplified by risperidone, has surprisingly been demonstrated to show improved efficacy for the treatment of various CNS disorders, particularly psychotic disorders like schizophrenia and related psychiatric conditions, including bipolar disorder, bipolar depression, mania and atypical depression by virtue of having a greater therapeutic efficacy (inhibition of CAR). The unexpected benefits extend beyond greater therapeutic efficacy into reduced EPS liability (catalepsy). In contrast, this latter effect was not seen with aripiprazole.

Claims

1. A pharmaceutical composition comprising a combination of bifeprunox and at least one D2/5-HT2A receptor antagonistic ligand and at least one pharmaceutically acceptable auxiliary.

2. The pharmaceutical composition of claim 1, wherein the D2/5-HT2A receptor antagonistic ligand is selected from clozapine, olanzapine, risperidone, ziprasidone, quetiapine, sertindole, iloperidone, asenapine, blonanserin, cariprazin, lurasidone and paliperidone.

3. The pharmaceutical composition of claim 2, wherein the D2/5-HT2A receptor antagonistic ligand is risperidone.

4. The pharmaceutical composition of any one of claims 1-3, wherein the dosage of both bifeprunox and the D₂/5 -HT₂A receptor antagonistic ligand ranges from about 0.05 to about 40 mg.

5. A package comprising a first pharmaceutical composition comprising bifeprunox and a second pharmaceutical composition comprising at least one D2/5 -HT₂A receptor antagonistic ligand.

6. The pharmaceutical composition of any one of claims 1-4 or the package of claim 5 for use in the treatment of CNS disorders selected from psychotic disorders like schizophrenia and related psychiatric conditions, bipolar disorder, bipolar depression, mania and atypical depression.

7. Use of a combination of bifeprunox and at least one D₂/5-HT_2A receptor antagonistic ligand for the preparation of a medicament for the treatment of CNS disorders selected from psychotic disorders like schizophrenia and related psychiatric conditions, bipolar disorder, bipolar depression, mania and atypical depression.

8. The use of claim 7, wherein risperidone is used as the D₂/5-HT_2A receptor antagonistic ligand, and bifeprunox is administered prior to risperidone.

9. A method for treating a patient suffering from or susceptible to a CNS disorder, comprising administering to said patient an effective amount of a first component which is bifeprunox, in combination with an effective amount of a second component which is at least one D₂/5-HT_2A receptor antagonistic ligand.

10. The method of claim 9, wherein risperidone is used as the D₂/5-HT_2A receptor antagonistic ligand, and bifeprunox is administered prior to risperidone.