Pharmacologic profile of ITI-333: a novel molecule for treatment of substance use disorders.

RATIONALE: Medications are urgently needed to treat symptoms of drug withdrawal and mitigate dysphoria and psychiatric comorbidities that drive opioid abuse and relapse. ITI-333 is a novel molecule in development for treatment of substance use disorders, psychiatric comorbidities, and pain. OBJECTIVE: Characterize the preclinical profile of ITI-333 using pharmacological, behavioral, and physiological assays. METHODS: Cell-based assays were used to measure receptor binding and intrinsic efficacy of ITI-333; animal models were employed to assess effects on opioid reinstatement, precipitated oxycodone withdrawal, and drug abuse liability. RESULTS: In vitro, ITI-333 is a potent 5-HT2A receptor antagonist (Ki = 8 nM) and a biased, partial agonist at µ-opioid (MOP) receptors (Ki = 11 nM; lacking ß-arrestin agonism) with lesser antagonist activity at adrenergic α1A (Ki = 28 nM) and dopamine D1 (Ki = 50 nM) receptors. In vivo, ITI-333 blocks 5-HT2A receptor-mediated head twitch and MOP receptor-mediated effects on motor hyperactivity in mice. ITI-333 alone is a naloxone-sensitive analgesic (mice) which suppresses somatic signs of naloxone-precipitated oxycodone withdrawal (mice) and heroin cue-induced reinstatement responding without apparent tolerance or physical dependence after chronic dosing (rats). ITI-333 did not acutely impair gastrointestinal or pulmonary function (rats) and was not intravenously self-administered by heroin-maintained rats or rhesus monkeys. CONCLUSIONS: ITI-333 acts as a potent 5-HT2A receptor antagonist, as well a biased MOP receptor partial agonist with low intrinsic efficacy. ITI-333 mitigates opioid withdrawal/reinstatement, supporting its potential utility as a treatment for OUD.

Adjunctive lumateperone (ITI-007) in the treatment of bipolar depression: Results from a randomized placebo-controlled clinical trial.

OBJECTIVE: This phase 3, randomized, double-blind, placebo-controlled study (NCT02600507) evaluated the efficacy and safety of lumateperone adjunctive therapy to lithium or valproate in patients with bipolar depression. METHODS: Patients (18-75 years) with bipolar I or bipolar II disorder experiencing a major depressive episode (MDE), with inadequate therapeutic response to lithium or valproate, were randomized 1:1:1 to 6 weeks adjunctive therapy with lumateperone 28 mg (n = 176), lumateperone 42 mg (n = 177), or placebo (n = 176). The primary and key secondary efficacy endpoints were change from baseline to Day 43 in Montgomery-Åsberg Depression Rating Scale (MADRS) Total score and the Clinical Global Impression Scale-Bipolar Version-Severity Scale (CGI-BP-S) depression subscore. Safety assessments included adverse events, laboratory evaluations, vital signs, extrapyramidal symptoms (EPS), and suicidality. RESULTS: Patients treated with adjunctive lumateperone 42 mg showed significantly greater improvement compared with adjunctive placebo in MADRS Total score (LS mean difference vs placebo [LSMD], -2.4; p = 0.02) and CGI-BP-S depression subscore (LSMD, -0.3; p = 0.01), while adjunctive lumateperone 28 mg showed numerical improvement in MADRS Total score (LSMD, -1.7; p = 0.10) and improvement in the CGI-BP-S depression subscore (LSMD, -0.3; p = 0.04). Adjunctive lumateperone treatment was well tolerated; treatment-emergent adverse events reported at rates >5% and twice placebo for lumateperone 42 mg were somnolence (11.3%), dizziness (10.7%), and nausea (8.5%), with minimal risk of EPS, metabolic abnormalities, or increased prolactin. CONCLUSIONS: Lumateperone 42-mg treatment adjunctive to lithium or valproate significantly improved depression symptoms and was generally well tolerated in patients with MDEs associated with either bipolar I or bipolar II disorder.

Single doses of a highly selective inhibitor of phosphodiesterase 1 (lenrispodun) in healthy volunteers: a randomized pharmaco-fMRI clinical trial.

Lenrispodun is a potent and highly selective inhibitor of phosphodiesterase (PDE) type 1, which is thought to prolong intracellular second messenger signaling within cortical and subcortical dopaminergic brain regions. This is the first study of a PDE1 inhibitor in healthy volunteers using behavioral and neuroimaging approaches to examine its effects on neural targets and to provide a safety and tolerability assessment. The primary objectives were to determine whether lenrispodun induces changes in BOLD fMRI signals in the inferior frontal gyrus (IFG) during the stop signal task, and the dorsal anterior insula (dAI) during the extinction phase of a fear conditioning/extinction task. Using a double-blind, placebo-controlled, within-subjects design, 26 healthy individuals (22 completed all fMRI sessions) received in random order a single oral dose of placebo, lenrispodun 1.0 milligram (mg) or lenrispodun 10.0 mg and completed several tasks in the scanner including the stop signal (n = 24) and fear conditioning/extinction tasks (n = 22). Prespecified region-of-interest analyses for the IFG and dAI were computed using linear mixed models. Lenrispodun induced increases in IFG activity during the stop signal task at 1.0 mg (Cohen's d = 0.63) but not 10.0 mg (Cohen's d = 0.07) vs. placebo. Lenrispodun did not induce changes in dAI activity during fear extinction at either dose. Exploratory outcomes revealed changes in cardiac interoception. Lenrispodun administration was well-tolerated. These results provide evidence that 1.0 mg lenrispodun selectively improved neural inhibitory control without altering fear extinction processing. Future investigations should determine whether lenrispodun improves inhibitory control in target populations such as individuals with attention deficit hyperactivity disorder. Trial registration: ClinicalTrials.gov identifier: NCT03489772.

Efficacy and Safety of Lumateperone for Major Depressive Episodes Associated With Bipolar I or Bipolar II Disorder: A Phase 3 Randomized Placebo-Controlled Trial.

OBJECTIVE: In a phase 3 randomized double-blind placebo-controlled study, the authors investigated the efficacy and safety of 42 mg/day of lumateperone in patients with bipolar I or bipolar II disorder experiencing a major depressive episode. METHODS: Patients 18-75 years old with a clinical diagnosis of bipolar I or bipolar II disorder and experiencing a major depressive episode were eligible for the study. Patients were randomized in a 1:1 ratio to receive 42 mg/day of lumateperone (N=188) or placebo (N=189), administered orally once daily in the evening for 6 weeks. The primary and key secondary efficacy endpoints were change from baseline to day 43 in score on the Montgomery-Åsberg Depression Rating Scale (MADRS) and total score on the Clinical Global Impressions Scale-Bipolar Version severity scale (CGI-BP-S), respectively. Safety assessments included treatment-emergent adverse events, laboratory parameters, vital signs, extrapyramidal symptoms, and suicidality. RESULTS: At day 43, lumateperone treatment was associated with significantly greater improvement from baseline in MADRS score compared with placebo (least squares mean difference compared with placebo, -4.6 points; effect size=-0.56) and CGI-BP-S total score (least squares mean difference compared with placebo, -0.9; effect size=-0.46). Significant MADRS superiority for lumateperone over placebo was observed both in patients with bipolar I and bipolar II disorders. Somnolence and nausea were the only treatment-emergent adverse events that occurred with lumateperone at a clinically meaningful greater rate than placebo. The incidence of extrapyramidal symptom-related treatment-emergent adverse events was low and similar to that for placebo. Minimal changes were observed in weight, vital signs, or metabolic or endocrine assessments. CONCLUSIONS: Lumateperone at 42 mg/day significantly improved depression symptoms and was generally well tolerated in patients with major depressive episodes associated with both bipolar I and bipolar II disorders.

Safety and tolerability of lumateperone for the treatment of schizophrenia: a pooled analysis of late-phase placebo- and active-controlled clinical trials.

Lumateperone, an antipsychotic that is US Food and Drug Administration-approved for the treatment of schizophrenia, has a novel mechanism of action that may confer beneficial effects with improved tolerability. This pooled analysis of three randomized, double-blind, placebo-controlled trials was conducted to evaluate the safety and tolerability of lumateperone 42 mg. The pooled population comprised 1073 patients with an acute exacerbation of schizophrenia randomized to placebo (n = 412), lumateperone 42 mg (n = 406) or risperidone 4 mg (n = 255). Treatment-emergent adverse events (TEAEs) were predominantly mild and rates of discontinuation due to TEAEs with lumateperone 42 mg (0.5%) were similar to placebo (0.5%) and lower than risperidone (4.7%). The only TEAEs that occurred at a rate of ≥5% and twice placebo for lumateperone were somnolence/sedation and dry mouth. Mean change from baseline in metabolic parameters and prolactin were similar to or reduced in lumateperone 42 mg relative to placebo-treated patients and were smaller than risperidone. Mean change in weight and rates of extrapyramidal symptoms-related TEAEs were similar for lumateperone 42 mg and placebo-treated patients and less than for risperidone-treated patients. This pooled analysis demonstrates the safety and favorable tolerability profile of lumateperone 42 mg.

A review of the pharmacology and clinical profile of lumateperone for the treatment of schizophrenia.

Schizophrenia is associated with a tremendous individual and societal burden. The disease is characterized by a complex set of symptoms including psychosis, hallucinations, delusions and related positive symptoms combined with social function deficits, cognitive disturbances and, often, devastating mood disorder, such as comorbid depression. Management of the disease often requires lifelong pharmacotherapy. However, many pharmacotherapies do not improve all symptoms (e.g., social withdrawal, depression, cognitive deficits) and can be associated with intolerable side effects such as weight gain and metabolic disturbances, motor dysfunction and endocrine dysregulation. Lumateperone (ITI-007, CAPLYTA™) is a novel antipsychotic agent, discovered and developed by Intra-Cellular Therapies, Inc. (ITCI) and approved for treatment of schizophrenia in adults in December 2019. Lumateperone simultaneously modulates serotonin, dopamine and glutamate neurotransmission, three key neurotransmitters implicated in schizophrenia. It achieves efficacy with a favorable safety profile. The clinical development program included 20 clinical trials with over 1900 individuals exposed to lumateperone. The program demonstrated the efficacy for lumateperone in two positive well controlled trials in patients with schizophrenia. The unique pharmacology of lumateperone supports the observed benefits across a wide range of symptoms, including social function and depression, and supports its favorable safety profile. Here, we review the discovery of lumateperone's unique biological effects and its clinical actions in the treatment of schizophrenia.

Safety and tolerability of lumateperone 42 mg: An open-label antipsychotic switch study in outpatients with stable schizophrenia.

BACKGROUND: Lumateperone is a mechanistically novel agent FDA-approved for the treatment of schizophrenia. Efficacy and favorable tolerability of lumateperone were demonstrated in 2 short-term placebo-controlled studies in patients with schizophrenia. This open-label study investigated the short-term safety/tolerability of lumateperone in outpatients with stable schizophrenia switched from previous antipsychotic treatment. METHODS: Adult outpatients with stable schizophrenia were switched from previous antipsychotics to lumateperone 42 mg once daily for six weeks, then patients were switched back to previous or another approved antipsychotic for 2 weeks. The primary objective assessed adverse events (AE), vital signs, laboratory tests, and extrapyramidal symptoms (EPS). Schizophrenia symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). RESULTS: Among 301 patients switched to lumateperone (study completion=71.2%), treatment-emergent AEs (TEAEs) occurred in 137 patients (45.5%), with 92 (30.6%) experiencing a drug-related TEAE. The most common drug-related TEAEs were somnolence (6.6%), headache (5.3%), and dry mouth (5.3%). Most TEAEs were mild or moderate in severity. EPS-related TEAEs were rare (1.0%). There were significant decreases from previous antipsychotics baseline in total cholesterol (P<.01), low-density lipoprotein cholesterol (P<.05), body weight (P<.01), and prolactin (P<.01); most of these parameters worsened within 2 weeks of resuming other antipsychotic treatment. PANSS Total scores remained stable relative to previous antipsychotics baseline during lumateperone treatment. CONCLUSIONS: In outpatients with stable schizophrenia, lumateperone was well tolerated with low risk of cardiometabolic and EPS adverse effects and stably maintained or improved schizophrenia symptoms. These data further support the safety, tolerability, and effectiveness of lumateperone in patients with schizophrenia.

Efficacy and Safety of Lumateperone for Treatment of Schizophrenia: A Randomized Clinical Trial.

Importance: Individuals living with schizophrenia are affected by cardiometabolic, endocrine, and motor adverse effects of current antipsychotic medications. Lumateperone is a serotonin, dopamine, and glutamate modulator with the potential to treat schizophrenia with few adverse effects. Objective: To examine the efficacy and safety of lumateperone for the short-term treatment of schizophrenia. Design, Setting, and Participants: This randomized, double-blind, placebo-controlled, phase 3 clinical trial was conducted from November 13, 2014, to July 20, 2015, with data analyses performed from August 13 to September 15, 2015. Patients with schizophrenia who were aged 18 to 60 years and were experiencing an acute exacerbation of psychosis were enrolled from 12 clinical sites in the United States. Interventions: Patients were randomized 1:1:1 (150 patients in each arm) to receive lumateperone tosylate, 60 mg; lumateperone tosylate, 40 mg (equivalent to 42 or 28 mg, respectively, of the active moiety lumateperone); or placebo once daily for 4 weeks. Main Outcomes and Measures: The prespecified primary efficacy end point was mean change from baseline to day 28 in the Positive and Negative Syndrome Scale (PANSS) total score vs placebo. The key secondary efficacy measure was the Clinical Global Impression-Severity of Illness (CGI-S) score. The PANSS subscale scores, social function, safety, and tolerability were also assessed. Results: The study comprised 450 patients (mean [SD] age, 42.4 [10.2] years; 346 [77.1%] male; mean [SD] baseline PANSS score, 89.8 [10.3]; mean [SD] baseline CGI-S score, 4.8 [0.6]). In the prespecified modified intent-to-treat efficacy analysis (n = 435), 42 mg of lumateperone met the primary and key secondary efficacy objectives, demonstrating a statistically significant improvement vs placebo from baseline to day 28 on the PANSS total score (least-squares mean difference [LSMD], -4.2; 95% CI, -7.8 to -0.6; P = .02; effect size [ES], -0.3) and the CGI-S (LSMD, -0.3; 95% CI, -0.5 to -0.1; P = .003; ES, -0.4). For 28 mg of lumateperone, the LSMD from baseline to day 28 was -2.6 (95% CI, -6.2 to 1.1; P = .16; ES, -0.2) on the PANSS total score and -0.2 (95% CI, -0.5 to 0.0; P = .02; ES, -0.3) on the CGI-S. Both lumateperone doses were well tolerated without clinically significant treatment-emergent motor adverse effects or changes in cardiometabolic or endocrine factors vs placebo. Conclusions and Relevance: Lumateperone demonstrated efficacy for improving the symptoms of schizophrenia and had a favorable safety profile. Trial Registration: ClinicalTrials.gov identifier: NCT02282761.

Dopamine D2 receptor occupancy of lumateperone (ITI-007): a Positron Emission Tomography Study in patients with schizophrenia.

Dopamine D2 receptor occupancy (D2RO) is a key feature of all currently approved antipsychotic medications. However, antipsychotic efficacy associated with high D2RO is often limited by side effects such as motor disturbances and hyperprolactinemia. Lumateperone (ITI-007) is a first-in-class selective and simultaneous modulator of serotonin, dopamine and glutamate in development for the treatment of schizophrenia and other disorders. The primary objective of the present study was to determine D2RO at plasma steady state of 60 mg ITI-007, a dose that previously demonstrated antipsychotic efficacy in a controlled trial, administered orally open-label once daily in the morning for two weeks in patients with schizophrenia (N = 10) and after at least a two-week washout period from standard of care antipsychotics. D2RO was determined using positron emission tomography with 11C-raclopride as the radiotracer. Mean peak dorsal striatal D2RO was 39% at 60 mg ITI-007 occurring 1 h post-dose. Lumateperone was well-tolerated with a favorable safety profile in this study. There were no clinically significant changes in vital signs, ECGs, or clinical chemistry laboratory values, including prolactin levels. There were no adverse event reports of akathisia or other extrapyramidal motor side effects; mean scores on motor function scales indicated no motor disturbances with lumateperone treatment. This level of occupancy is lower than most other antipsychotic drugs at their efficacious doses and likely contributes to the favorable safety and tolerability profile of lumateperone with reduced risk for movement disorders and hyperprolactinemia. If approved, lumateperone may provide a new and safe treatment option for individuals living with schizophrenia.

PDE Inhibitors for the Treatment of Schizophrenia.

Schizophrenia is a pervasive neuropsychiatric disorder affecting over 1% of the world's population. Dopamine system dysfunction is strongly implicated in the etiology of schizophrenia. Data support the long-standing concept of schizophrenia as a disease characterized by hyperactivity within midbrain (striatal D2) dopamine systems. In addition, there is now considerable evidence that glutamate neurotransmission, mediated through NMDA-type receptors, is deficient in patients with schizophrenia and that hypoactivity in cortical dopamine and glutamate pathways is a key feature of this serious mental disorder. While current antipsychotic medications-with a common mechanism involving dopamine D2 receptor antagonism or pre-synaptic partial agonism-adequately address positive symptoms of the disease, such as the acute hallucinations and delusions, they fail to substantially improve negative features, such as social isolation, and can further compromise poor cognitive function associated with schizophrenia. In fact, cognitive impairment is a core feature of schizophrenia. The treatment of cognitive impairment and other residual symptoms associated with schizophrenia, therefore, remains a significant unmet medical need. With current cell-surface receptor-based pharmacology falling short of addressing these core cognitive symptoms, more recent approaches to treatment development have focused on processes within the cell. In this review, we discuss the importance of cyclic nucleotide (cNT) phosphodiestereases (PDEs)-intracellular enzymes that control the activity of key second messenger signaling pathways in the brain-which have been proposed as targets for new schizophrenia therapies. We also discuss the challenge facing those developing drugs to target specific PDE enzymes involved in psychopathology without involving other systems that produce concomitant side effects.

Dopamine Targeting Drugs for the Treatment of Schizophrenia: Past, Present and Future.

Schizophrenia is a chronic and debilitating neuropsychiatric disorder affecting approximately 1% of the world's population. This disease is associated with considerable morbidity placing a major financial burden on society. Antipsychotics have been the mainstay of the pharmacological treatment of schizophrenia for decades. The traditional typical and atypical antipsychotics demonstrate clinical efficacy in treating positive symptoms, such as hallucinations and delusions, while are largely ineffective and may worsen negative symptoms, such as blunted affect and social withdrawal, as well as cognitive function. The inability to treat these latter symptoms may contribute to social function impairment associated with schizophrenia. The dysfunction of multiple neurotransmitter systems in schizophrenia suggests that drugs selectively targeting one neurotransmission pathway are unlikely to meet all the therapeutic needs of this heterogeneous disorder. Often, however, the unintentional engagement of multiple pharmacological targets or even the excessive engagement of intended pharmacological targets can lead to undesired consequences and poor tolerability. In this article, we will review marketed typical and atypical antipsychotics and new therapeutic agents targeting dopamine receptors and other neurotransmitters for the treatment of schizophrenia. Representative typical and atypical antipsychotic drugs and new investigational drug candidates will be systematically reviewed and compared by reviewing structure-activity relationships, pharmacokinetic properties, drug metabolism and safety, pharmacological properties, preclinical data in animal models, clinical outcomes and associated side effects.

Preclinical profile of ITI-214, an inhibitor of phosphodiesterase 1, for enhancement of memory performance in rats.

RATIONALE: Therapeutic agents for memory enhancement in psychiatric disorders, such as schizophrenia, are urgently needed. OBJECTIVE: The aim of this study is to characterize the preclinical profile of ITI-214, a potent inhibitor of phosphodiesterase 1 (PDE1). METHODS: ITI-214 was assayed for inhibition of PDE1 versus other PDE enzyme families using recombinant human PDE enzymes and for off-target binding to 70 substrates (General SEP II diversity panel; Caliper Life Sciences). Effects of ITI-214 (0.1-10 mg/kg, po) on memory performance were assayed in rats using the novel object recognition (NOR) paradigm, with drug given at specified time points prior to or following exposure to objects in an open field. ITI-214 was evaluated for potential drug-drug interaction with risperidone in rats using conditioned avoidance response (CAR) and pharmacokinetic assessments. RESULTS: ITI-214 inhibited PDE1A (K i = 33 pmol) with >1000-fold selectivity for the nearest other PDE family (PDE4D) and displayed minimal off-target binding interactions in a 70-substrate selectivity profile. By using specific timing of oral ITI-214 administration, it was demonstrated in the NOR that ITI-214 is able to enhance acquisition, consolidation, and retrieval memory processes. All memory effects were in the absence of effects on exploratory behavior. ITI-214 did not disrupt the risperidone pharmacokinetic profile or effects in CAR. CONCLUSIONS: ITI-214 improved the memory processes of acquisition, consolidation, and retrieval across a broad dose range (0.1-10 mg/kg, po) without disrupting the antipsychotic-like activity of a clinical antipsychotic medication, specifically risperidone. Clinical development of ITI-214 is currently in progress.

Discovery of Potent and Selective Inhibitors of Phosphodiesterase 1 for the Treatment of Cognitive Impairment Associated with Neurodegenerative and Neuropsychiatric Diseases.

A diverse set of 3-aminopyrazolo[3,4-d]pyrimidinones was designed and synthesized. The structure-activity relationships of these polycyclic compounds as phosphodiesterase 1 (PDE1) inhibitors were studied along with their physicochemical and pharmacokinetic properties. Systematic optimizations of this novel scaffold culminated in the identification of a clinical candidate, (6aR,9aS)-2-(4-(6-fluoropyridin-2-yl)benzyl)-5-methyl-3-(phenylamino)-5,6a,7,8,9,9a-hexahydrocyclopenta[4,5]imidazo[1,2-a]pyrazolo[4,3-e]pyrimidin-4-(2H)-one phosphate (ITI-214), which exhibited picomolar inhibitory potency for PDE1, demonstrated excellent selectivity against all other PDE families and showed good efficacy in vivo. Currently, this investigational new drug is in Phase I clinical development and being considered for the treatment of several indications including cognitive deficits associated with schizophrenia and Alzheimer's disease, movement disorders, attention deficit and hyperactivity disorders, and other central nervous system (CNS) and non-CNS disorders.

ITI-007 for the Treatment of Schizophrenia: A 4-Week Randomized, Double-Blind, Controlled Trial.

BACKGROUND: An urgent need exists for new treatments of schizophrenia that are effective against a broad range of symptoms and free of limiting safety issues. ITI-007 is a new molecular entity with a pharmacologic profile that combines dose-related monoamine modulation with phosphorylation of intracellular signaling proteins. METHODS: A phase II randomized, double-blind, placebo-controlled, and active-controlled trial was conducted at eight sites in the United States with randomization of 335 acutely psychotic adults with schizophrenia. ITI-007 (60 mg and 120 mg), placebo, and risperidone, included for assay sensitivity, were evaluated as monotherapy for 4 weeks. The primary outcome measure was the Positive and Negative Syndrome Scale total score, with secondary analyses conducted on symptom subscales. RESULTS: ITI-007 60 mg (p = .017, effect size = .4) and risperidone (p = .013, effect size = .4) demonstrated antipsychotic efficacy superiority over placebo on the primary end point. The results of secondary analyses reflected improvements in negative and depressive symptoms by ITI-007 60 mg. ITI-007 120 mg did not separate from placebo. However, both doses of ITI-007 were well tolerated in this patient population, as evidenced by low discontinuation and adverse event rates, and were associated with a benign metabolic profile as evidenced by significantly lower levels of prolactin, fasting glucose, total cholesterol, and triglycerides than risperidone. CONCLUSIONS: The mechanistically novel investigational drug ITI-007 was effective for the treatment of schizophrenia and comparable with placebo on safety measures in this trial. Secondary analyses indicated that ITI-007 improved negative and depression symptoms and might have expanded therapeutic efficacy in comparison with current antipsychotic drugs.

ITI-007 demonstrates brain occupancy at serotonin 5-HT2A and dopamine D2 receptors and serotonin transporters using positron emission tomography in healthy volunteers.

RATIONALE: Central modulation of serotonin and dopamine underlies efficacy for a variety of psychiatric therapeutics. ITI-007 is an investigational new drug in development for treatment of schizophrenia, mood disorders, and other neuropsychiatric disorders. OBJECTIVES: The purpose of this study was to determine brain occupancy of ITI-007 at serotonin 5-HT2A receptors, dopamine D2 receptors, and serotonin transporters using positron emission tomography (PET) in 16 healthy volunteers. METHODS: Carbon-11-MDL100907, carbon-11-raclopride, and carbon-11-3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)-benzonitrile) (carbon-11-DASB) were used as the radiotracers for imaging 5-HT2A receptors, D2 receptors, and serotonin transporters, respectively. Brain regions of interest were outlined using magnetic resonance tomography (MRT) with cerebellum as the reference region. Binding potentials were estimated by fitting a simplified reference tissue model to the measured tissue-time activity curves. Target occupancy was expressed as percent change in the binding potentials before and after ITI-007 administration. RESULTS: Oral ITI-007 (10-40 mg) was safe and well tolerated. ITI-007 rapidly entered the brain with long-lasting and dose-related occupancy. ITI-007 (10 mg) demonstrated high occupancy (>80 %) of cortical 5-HT2A receptors and low occupancy of striatal D2 receptors (~12 %). D2 receptor occupancy increased with dose and significantly correlated with plasma concentrations (r (2) = 0.68, p = 0.002). ITI-007 (40 mg) resulted in peak occupancy up to 39 % of striatal D2 receptors and 33 % of striatal serotonin transporters. CONCLUSIONS: The results provide evidence for a central mechanism of action via dopaminergic and serotonergic pathways for ITI-007 in living human brain and valuable information to aid dose selection for future clinical trials.

Functional profile of a novel modulator of serotonin, dopamine, and glutamate neurotransmission.

RATIONALE: Schizophrenia remains among the most prevalent neuropsychiatric disorders, and current treatment options are accompanied by unwanted side effects. New treatments that better address core features of the disease with minimal side effects are needed. OBJECTIVES: As a new therapeutic approach, 1-(4-fluoro-phenyl)-4-((6bR, 10aS)-3-methyl-2,3,6b,9,10,10a-hexahydro-1H,7H-pyrido[3',4':4,5]pyrrolo[1,2,3-de]quinoxalin-8-yl)-butan-1-one (ITI-007) is currently in human clinical trials for the treatment of schizophrenia. Here, we characterize the preclinical functional activity of ITI-007. RESULTS: ITI-007 is a potent 5-HT2A receptor ligand (K i = 0.5 nM) with strong affinity for dopamine (DA) D2 receptors (K i = 32 nM) and the serotonin transporter (SERT) (K i = 62 nM) but negligible binding to receptors (e.g., H1 histaminergic, 5-HT2C, and muscarinic) associated with cognitive and metabolic side effects of antipsychotic drugs. In vivo it is a 5-HT2A antagonist, blocking (±)-2,5-dimethoxy-4-iodoamphetamine hydrochloride (DOI)-induced headtwitch in mice with an inhibitory dose 50 (ID50) = 0.09 mg/kg, per oral (p.o.), and has dual properties at D2 receptors, acting as a postsynaptic D2 receptor antagonist to block D-amphetamine hydrochloride (D-AMPH) hyperlocomotion (ID50 = 0.95 mg/kg, p.o.), yet acting as a partial agonist at presynaptic striatal D2 receptors in assays measuring striatal DA neurotransmission. Further, in microdialysis studies, this compound significantly and preferentially enhances mesocortical DA release. At doses relevant for antipsychotic activity in rodents, ITI-007 has no demonstrable cataleptogenic activity. ITI-007 indirectly modulates glutamatergic neurotransmission by increasing phosphorylation of GluN2B-type N-methyl-D-aspartate (NMDA) receptors and preferentially increases phosphorylation of glycogen synthase kinase 3ß (GSK-3ß) in mesolimbic/mesocortical dopamine systems. CONCLUSION: The combination of in vitro and in vivo activities of this compound support its development for the treatment of schizophrenia and other psychiatric and neurologic disorders.

Discovery of a tetracyclic quinoxaline derivative as a potent and orally active multifunctional drug candidate for the treatment of neuropsychiatric and neurological disorders.

We report the synthesis and structure-activity relationships of a class of tetracyclic butyrophenones that exhibit potent binding affinities to serotonin 5-HT(2A) and dopamine D2 receptors. This work has led to the discovery of 4-((6bR,10aS)-3-methyl-2,3,6b,9,10,10a-hexahydro-1H,7H-pyrido[3',4':4,5]pyrrolo[1,2,3-de]quinoxalin-8-yl)-1-(4-fluorophenyl)-butan-1-one 4-methylbenzenesulfonate (ITI-007), which is a potent 5-HT(2A) antagonist, postsynaptic D2 antagonist, and inhibitor of serotonin transporter. This multifunctional drug candidate is orally bioavailable and exhibits good antipsychotic efficacy in vivo. Currently, this investigational new drug is under clinical development for the treatment of neuropsychiatric and neurological disorders.

Intracellular signaling and approaches to the treatment of schizophrenia and associated cognitive impairment.

Schizophrenia is a pervasive neuropsychiatric disorder affecting over 1% of the world's population. Dopamine system dysfunction is strongly implicated in the etiology of schizophrenia. Data support the long-standing concept of schizophrenia as a disease characterized by hyperactivity within midbrain (striatal D2) dopamine systems. In addition, there is now considerable evidence that glutamate neurotransmission, mediated through NMDA-type receptors, is deficient in schizophrenic patients and that hypoactivity in cortical dopamine and glutamate pathways is a key feature of the schizophrenic brain. While current antipsychotic medications-typically dopamine D2 antagonists-adequately address positive symptoms of the disease, such as the acute hallucinations and delusions, they fail to substantially improve negative features, such as social isolation, and can further compromise poor cognitive function in schizophrenic patients. In fact, cognitive impairment is a core feature of schizophrenia. The treatment of cognitive impairment and other residual symptoms associated with schizophrenia, therefore, remains a significant unmet medical need. With current cell-surface receptor-based pharmacology falling short of addressing these core symptoms associated with schizophrenia, more recent approaches to treatment development have focused on processes within the cell. In this review, we discuss the importance of a number of intracellular targets, including cyclic nucleotide phosphodiestereases, and non-phosphodiesterase approaches such as ITI-007, which have been proposed to regulate hyperdopaminergic function, hypoglutamatergic function and/or the delicate balance of the two associated with cognitive deficits in schizophrenia. We also discuss the challenge facing those developing drugs to target specific pathways involved in psychopathology without involving other systems that produce concomitant side effects.

Pimavanserin, a selective serotonin (5-HT)2A-inverse agonist, enhances the efficacy and safety of risperidone, 2mg/day, but does not enhance efficacy of haloperidol, 2mg/day: comparison with reference dose risperidone, 6mg/day.

Most atypical antipsychotic drugs (APDs), e.g. risperidone (RIS), produce more extensive blockade of brain serotonin (5-HT)(2A) than dopamine (DA) D(2) receptors. This distinguishes them from typical APDs, e.g. haloperidol (HAL). Our objective was to test the hypothesis that augmentation of low doses of RIS or HAL (2mg/day) with pimavanserin (PIM), a selective 5-HT(2A) inverse agonist, to enhance 5-HT(2A) receptor blockade, can achieve efficacy comparable to RIS, 6mg/day, but with lesser side effects. In a multi-center, randomized, double-blind, 6week trial, 423 patients with chronic schizophrenia experiencing a recent exacerbation of psychotic symptoms were randomized to RIS2mg+placebo (RIS2PBO), RIS2mg+PIM20mg (RIS2PIM), RIS6mg+PBO (RIS6PBO), HAL2mg+PBO (HAL2PBO), or HAL2mg+PIM20mg (HAL2PIM). Improvement in psychopathology was measured by the PANSS and CGI-S. The reduction in PANSS Total Score with RIS2PIM at endpoint was significantly greater than RIS2PBO: -23.0 vs. -16.3 (p=0.007), and not significantly different from the RIS6PBO group: -23.2 points. The percentage of patients with ≥20% improvement at day 15 in the RIS2PIM group was 62.3%, significantly greater than the RIS6PBO (42.1%; p=0.01) and the RIS2PBO groups (37.7%; p=0.002). Weight gain and hyperprolactinemia were greater in the RIS6PBO group than the RIS2PIM group but there was no difference in extrapyramidal side effects (EPS). HAL2PBO and HAL2PIM were not significantly different from each other in efficacy but HAL2PIM had less EPS at end point. Both HAL groups and RIS6PBO showed equal improvement in psychopathology at endpoint, indicating HAL 2mg/day is effective to treat an acute exacerbation in chronic schizophrenia patients. In conclusion, a sub-effective RIS dose combined with PIM to enhance 5-HT(2A) receptor blockade provided faster onset of action, and at endpoint, equal efficacy and better safety, compared to standard dose RIS. These results support the conclusion that 5-HT(2A) receptor blockade is a key component of the action of some atypical APDs and can reduce EPS due to a typical APD.