Attenuation of anhedonia by cariprazine in the chronic mild stress model of depression

Cariprazine in the treatment of schizophrenia: a proof-of-concept trial

This 6-week, double-blind, placebo-controlled, proof-of-concept study evaluated the efficacy, safety, and tolerability of low-dose (1.5-4.5 mg/day) and high-dose (6-12 mg/day) cariprazine in patients with acute exacerbation of schizophrenia (NCT00404573). The primary efficacy measure was change in the Positive and Negative Syndrome Scale (PANSS) total score, analyzed using a last observation carried forward approach. Other efficacy measures included the Clinical Global Impression-Severity (secondary) and PANSS subscales (additional). There were no significant differences between the two doses of cariprazine and placebo in PANSS total score change or any other efficacy parameter after multiplicity adjustment. However, low-dose cariprazine versus placebo showed significantly greater reductions in PANSS total (P=0.033) and PANSS negative (P=0.027) scores without multiplicity adjustment. Common treatment-emergent adverse events (incidence≥5% and twice that in the placebo group in either cariprazine dose group) were akathisia, restlessness, tremor, back pain, and extrapyramidal disorder. In this study, the overall cariprazine treatment effect was not statistically significant, but patients treated with low-dose cariprazine showed significantly greater improvement in schizophrenia symptoms relative to placebo-treated patients. Cariprazine was generally well tolerated. Results of this study suggest that cariprazine may be effective in treating schizophrenia and future research is warranted.

The dopamine D₃-preferring D₂/D₃ dopamine receptor partial agonist, cariprazine, reverses behavioural changes in a rat neurodevelopmental model for schizophrenia

Current antipsychotic medication is largely ineffective against the negative and cognitive symptoms of schizophrenia. One promising therapeutic development is to design new molecules that balance actions on dopamine D2 and D3 receptors to maximise benefits and limit adverse effects. This study used two rodent paradigms to investigate the action of the dopamine D3-preferring D3/D2 receptor partial agonist cariprazine. In adult male rats, cariprazine (0.03-0.3 mg/kg i.p.), and the atypical antipsychotic aripiprazole (1-3 mg/kg i.p.) caused dose-dependent reversal of a delay-induced impairment in novel object recognition (NOR). Treating neonatal rat pups with phencyclidine (PCP) and subsequent social isolation produced a syndrome of behavioural alterations in adulthood including hyperactivity in a novel arena, deficits in NOR and fear motivated learning and memory, and a reduction and change in pattern of social interaction accompanied by increased ultrasonic vocalisations (USVs). Acute administration of cariprazine (0.1 and 0.3 mg/kg) and aripiprazole (3 mg/kg) to resultant adult rats reduced neonatal PCP-social isolation induced locomotor hyperactivity and reversed NOR deficits. Cariprazine (0.3 mg/kg) caused a limited reversal of the social interaction deficit but neither drug affected the change in USVs or the deficit in fear motivated learning and memory. Results suggest that in the behavioural tests investigated cariprazine is at least as effective as aripiprazole and in some paradigms it showed additional beneficial features further supporting the advantage of combined dopamine D3/D2 receptor targeting. These findings support recent clinical studies demonstrating the efficacy of cariprazine in treatment of negative symptoms and functional impairment in schizophrenia patients.

Clinical pharmacology study of cariprazine (MP-214) in patients with schizophrenia (12-week treatment)

PURPOSE

Cariprazine is a potent dopamine D3-preferring D3/D2 receptor partial agonist in development for the treatment of schizophrenia, bipolar mania, and depression. Pharmacokinetics of cariprazine and the two clinically relevant metabolites (desmethyl- and didesmethyl-cariprazine) was evaluated in a clinical pharmacology study.

METHODS

This was a multicenter, randomized, open-label, parallel-group, fixed-dose (3, 6, or 9 mg/day) study of 28-week duration (≤4-week observation, 12-week open-label treatment, and 12-week follow-up). Once-daily cariprazine was administered to 38 adult patients with schizophrenia. The pharmacokinetics of cariprazine, metabolites, and total active moieties (sum of cariprazine and two metabolites) was evaluated; efficacy and safety were also assessed.

RESULTS

Steady state was reached within 1-2 weeks for cariprazine and desmethyl-cariprazine, 4 weeks for didesmethyl-cariprazine, and 3 weeks for total active moieties. Cariprazine and desmethyl-cariprazine levels decreased >90% within 1 week after the last dose, didesmethyl-cariprazine decreased ~50% at 1 week, and total active moieties decreased ~90% within 4 weeks. Terminal half-lives of cariprazine, desmethyl-cariprazine, and didesmethyl-cariprazine ranged from 31.6 to 68.4, 29.7 to 37.5, and 314 to 446 hours, respectively. Effective half-life (calculated from time to steady state) of total active moieties was ~1 week. Incidence of treatment-emergent adverse events was 97.4%; 15.8% of patients discontinued due to adverse events. No abnormal laboratory values or major differences from baseline in extrapyramidal symptoms were observed.

CONCLUSION

Cariprazine and its active metabolites reached steady state within 4 weeks, and exposure was dose proportional over the range of 3-9 mg/day. Once-daily cariprazine was generally well tolerated in adult patients with schizophrenia.

Effects of cariprazine, a novel antipsychotic, on cognitive deficit and negative symptoms in a rodent model of schizophrenia symptomatology

Negative symptoms and cognitive impairment associated with schizophrenia are strongly associated with poor functional outcome and reduced quality of life and remain an unmet clinical need. Cariprazine is a dopamine D3/D2 receptor partial agonist with preferential binding to D3 receptors, recently approved by the FDA for the treatment of schizophrenia and manic or mixed episodes associated with bipolar I disorder. The aim of this study is to evaluate effects of cariprazine in an animal model of cognitive deficit and negative symptoms of schizophrenia. Following sub-chronic PCP administration (2mg/kg, IP for 7 days followed by 7 days drug-free), female Lister Hooded rats were administered cariprazine (0.05, 0.1, or 0.25mg/kg, PO) or risperidone (0.16 or 0.1mg/kg, IP) before testing in novel object recognition (NOR), reversal learning (RL), and social interaction (SI) paradigms. As we have consistently demonstrated, sub-chronic PCP significantly impaired behavior in these tests. Deficits were significantly improved by cariprazine, in a dose dependent manner in the operant RL test with efficacy at lower doses in the NOR and SI tests. Locomotor activity was reduced at the highest doses of 0.1mg/kg and 0.25mg/kg in NOR and SI. Risperidone also reversed the PCP-induced deficit in all tests. In conclusion, cariprazine was effective to overcome PCP-induced deficits in cognition and social behavior in a thoroughly validated rat model in tests representing specific symptom domains in schizophrenia patients. These findings support very recent results showing efficacy of cariprazine in the treatment of negative symptoms in schizophrenia patients.

The GAD65 knock out mouse - a model for GABAergic processes in fear- and stress-induced psychopathology

The γ-amino butyric acid (GABA) synthetic enzyme glutamic acid decarboxylase (GAD)65 is critically involved in the activity-dependent regulation of GABAergic inhibition in the central nervous system. It is also required for the maturation of the GABAergic system during adolescence, a phase that is critical for the development of several neuropsychiatric diseases. Mice bearing a null mutation of the GAD65 gene develop hyperexcitability of the amygdala and hippocampus, and a phenotype of increased anxiety and pathological fear memory reminiscent of posttraumatic stress disorder. Although genetic association of GAD65 in human has not yet been reported, these findings are in line with observations of reduced GABAergic function in these brain regions of anxiety disorder patients. The particular value of GAD65(-/-) mice thus lies in modeling the effects of reduced GABAergic function in the mature nervous system. The expression of GAD65 and a second GAD isozyme, GAD67, are differentially regulated in response to stress in limbic brain areas suggesting that by controlling GABAergic inhibition these enzymes determine the vulnerability for the development of pathological anxiety and other stress-induced phenotypes. In fact, we could recently show that GAD65 haplodeficiency, which results in delayed postnatal increase of GABA levels, provides resilience to juvenile-stress-induced anxiety to GAD65(+/-) mice thus foiling the increased fear and anxiety in homozygous GAD65(-/-) mice.

Pharmacological targeting of dopamine D3 receptors: Possible clinical applications of selective drugs

Dopamine D3 receptors have been pharmacologically engaged in humans since the development of the first antipsychotics and ergot-derivative dopamine (DA) agonists, even without knowing it. These agents were generally non-selective, developed primarily to target D2 receptors. In the last 10 years the understanding of the clinical implication of D3 receptors has been progressing also due to the identification of D3 gene polymorphisms, the use of more selective PET ligands such as [(11)C]-(+)-PHNO and the learning regarding the clinical use of the D3-preferential D2/D3 agonists ropinirole and pramipexole. A new specific neuroplasticity role of D3 receptor regarding dendrite arborisation outgrowth in dopaminergic neurons was also proposed to support, at least in part, the slowing of disease observed in subjects with Parkinson׳s Disease treated with DA agonists. Similar mechanisms could be at the basis of the antidepressant-like effects observed with DA agonists when co-administered with standard of care. Severe adverse event occurring with the use of anti-parkinsonian DA agonists in predisposed subjects, i.e., impulse control disorders, are now suggested to be putatively related to overactive D3 receptors. Not surprisingly, blockade of D3 receptors was proposed as treatment for addictive disorders, a goal that could be potentially achieved by repositioning buspirone, an anxiolytic drug with D3-preferential antagonistic features, or with novel selective D3 antagonists or partial agonists currently in development for schizophrenia. At the moment ABT-925 is the only selective D3 antagonist tested in schizophrenic patients in Phase II, showing an intriguing cognitive enhancing effects supported by preclinical data. Finally, exploratory pharmacogenetic analysis suggested that ABT-925 could be effective in a subpopulation of patients with a polymorphism on the D3 receptor, opening to a possible personalised medicine approach.

Efficacy and Safety of Cariprazine in Acute Exacerbation of Schizophrenia: Results From an International, Phase III Clinical Trial

This phase III study evaluated the efficacy and safety of cariprazine, a dopamine D3 and D2 receptor partial agonist with preferential binding to D3 receptors, in patients with acute exacerbation of schizophrenia. Patients were randomized to 6-week double-blind treatment with placebo, cariprazine 3 to 6 mg/d, or cariprazine 6 to 9 mg/d. Primary and secondary efficacy: change from baseline to week 6 in Positive and Negative Syndrome Scale total and Clinical Global Impressions-Severity scores, respectively, analyzed using a mixed-effects model for repeated measures adjusting for multiple comparisons. Safety included treatment-emergent adverse events, clinical laboratory values, vital signs, electrocardiograms, ophthalmologic examination, Columbia-Suicide Severity Rating Scale, and extrapyramidal symptom scales. In the Safety Population (placebo, n = 147; cariprazine 3-6 mg/d, n = 151; cariprazine 6-9 mg/d, n = 148), 60.5% of patients completed the study. At week 6, statistically significant least squares mean differences in favor of cariprazine versus placebo were observed for Positive and Negative Syndrome Scale total score (3-6 mg/d: -6.8, P = 0.003; 6-9 mg/d: -9.9, P < 0.001) and Clinical Global Impressions-Severity (3-6 mg/d: -0.3, P = 0.012; 6-9 mg/d: -0.5, P < 0.001). Common treatment-emergent adverse events (≥5% and twice the rate of placebo) in both cariprazine groups were akathisia, extrapyramidal disorder, and tremor; most were mild to moderate in severity. Mean changes in metabolic parameters were generally small and similar between groups. Prolactin levels decreased in all groups. In conclusion, cariprazine 3 to 6 and 6 to 9 mg/d versus placebo demonstrated significant improvement on primary and secondary efficacy parameters. Cariprazine was generally well tolerated. These results suggest that cariprazine may be a new and effective treatment for schizophrenia.