Kimberly E. Vanover

The role of M1 muscarinic receptor agonism of N-desmethylclozapine in the unique clinical effects of clozapine

RationaleClozapine is a unique antipsychotic, with efficacy against positive symptoms in treatment-resistant schizophrenic patients, and the ability to improve cognition and treat the negative symptoms characteristic of this disease. Despite its unique clinical actions, no specific molecular mechanism responsible for these actions has yet been described.Objectives and methodsTo comprehensively profile a large library of neuropsychiatric drugs, including most antipsychotics, at human monoamine receptors using R-SAT, an in vitro functional assay.ResultsProfiling revealed that N-desmethylclozapine (NDMC), the principal metabolite of clozapine, but not clozapine itself, is a potent and efficacious muscarinic receptor agonist, a molecular property not shared by any other antipsychotic. To further explore the role of NDMC muscarinic receptor agonist properties in mediating the physiological actions of clozapine, systemically administered NDMC was found to stimulate the phosphorylation of mitogen-activated protein kinase (MAP kinase) in mouse CA1 hippocampal neurons, an effect that was blocked by scopolamine, confirming central M1 muscarinic receptor agonist activity in vivo. Lastly, an analysis of clozapine and NDMC serum levels in schizophrenic patients indicated that high NDMC/clozapine ratios better predicted improvement in cognitive functioning and quality of life than the levels of either compound alone.ConclusionsThe muscarinic receptor agonist activities of NDMC are unique among antipsychotics, and provide a possible molecular basis for the superior clinical effects of clozapine pharmacotherapy.

Pharmacological and Behavioral Profile of N-(4-Fluorophenylmethyl)-N-(1-methylpiperidin-4-yl)-N′-(4-(2-methylpropyloxy)phenylmethyl) Carbamide (2R,3R)-Dihydroxybutanedioate (2:1) (ACP-103), a Novel 5-Hydroxytryptamine2A Receptor Inverse Agonist

The in vitro and in vivo pharmacological properties of N-(4-fluorophenylmethyl)-N-(1-methylpiperidin-4-yl)-N′-(4-(2-methylpropyloxy)phenylmethyl)carbamide (2R,3R)-dihydroxybutanedioate (2:1) (ACP-103) are presented. A potent 5-hydroxytryptamine (5-HT)2A receptor inverse agonist ACP-103 competitively antagonized the binding of [3H]ketanserin to heterologously expressed human 5-HT2A receptors with a mean pKi of 9.3 in membranes and 9.70 in whole cells. ACP-103 displayed potent inverse agonist activity in the cell-based functional assay receptor selection and amplification technology (R-SAT), with a mean pIC50 of 8.7. ACP-103 demonstrated lesser affinity (mean pKi of 8.80 in membranes and 8.00 in whole cells, as determined by radioligand binding) and potency as an inverse agonist (mean pIC50 7.1 in R-SAT) at human 5-HT2C receptors, and lacked affinity and functional activity at 5-HT2B receptors, dopamine D2 receptors, and other human monoaminergic receptors. Behaviorally, ACP-103 attenuated head-twitch behavior (3 mg/kg p.o.), and prepulse inhibition deficits (1-10 mg/kg s.c.) induced by the 5-HT2A receptor agonist (±)-2,5-dimethoxy-4-iodoamphetamine hydrochloride in rats and reduced the hyperactivity induced in mice by the N-methyl-d-aspartate receptor noncompetitive antagonist 5H-dibenzo[a,d]cyclohepten-5,10-imine (dizocilpine maleate; MK-801) (0.1 and 0.3 mg/kg s.c.; 3 mg/kg p.o.), consistent with a 5-HT2A receptor mechanism of action in vivo and antipsychotic-like efficacy. ACP-103 demonstrated >42.6% oral bioavailability in rats. Thus, ACP-103 is a potent, efficacious, orally active 5-HT2A receptor inverse agonist with a behavioral pharmacological profile consistent with utility as an antipsychotic agent.

A 5-HT2A receptor inverse agonist, ACP-103, reduces tremor in a rat model and levodopa-induced dyskinesias in a monkey model.

A potent 5-hydroxytryptamine (5-HT)2A receptor inverse agonist and antagonist, ACP-103 [N-(4-fluorophenylmethyl)-N-(1-methylpiperidin-4-yl)-N-(4-(2-methylpropyloxy)phenylmethyl) carbamide (2R,3R)-dihydroxybutanedioate (2:1, active:salt)], was evaluated for its ability to reduce the primary motor symptom of tremor using tacrine-induced tremulous jaw movements in rats, which is an animal model of parkinsonian tremor. Furthermore, ACP-103 was evaluated for its ability to reduce levodopa-induced dyskinesias in monkeys rendered parkinsonian with MPTP [1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine]. ACP-103 reduced tacrine-induced tremulous jaw movements in rats. In addition, ACP-103 administered in combination with levodopa caused a dose-related reduction in dyskinesias in monkeys. These data suggest that ACP-103 may have the potential to reduce tremor and levodopa-induced dyskinesias in Parkinsons disease.

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

Antipsychotic-like behavioral effects and cognitive enhancement by a potent and selective muscarinic M₁ receptor agonist, AC-260584.

AC-260584 (4-[3-(4-butylpiperidin-1-yl)-propyl]-7-fluoro-4H-benzo[1,4]oxazin-3-one) is a potent and selective muscarinic M-sub-1 receptor agonist. AC-260584 was evaluated in animal models: antipsychotic-like effects were tested by the ability to reduce amphetamine- and MK-801-induced hyperactivity and apomorphine-induced climbing; catalepsy was assessed by measuring step-down latency; spatial memory was tested by using the Morris water maze. AC-260584 reduced amphetamine- and MK-801-induced hyperactivity and apomorphine-induced climbing. In contrast to haloperidol, AC-260584 did not produce catalepsy. AC-260584 enhanced performance in the water maze during a probe test without a platform after 6 days of training, similar to the positive control tacrine. These data indicate that AC-260584 has a behavioral profile consistent with antipsychotic-like efficacy with the potential to improve cognitive performance and shows reduced liability for extrapyramidal symptoms.

PET analysis of the 5-HT2A receptor inverse agonist ACP-103 in human brain.

The mechanisms underlying the clinical properties of atypical antipsychotics have been postulated to be mediated, in part, by interactions with the 5-HT2A receptor. Recently, it has been recognized that clinically effective antipsychotic drugs are 5-HT2A receptor inverse agonists rather than neutral antagonists. In the present study, which is part of the clinical development of the novel, selective 5-HT2A receptor inverse agonist ACP-103, we applied positron emission tomography (PET) with the radioligand [11C]N-methylspiperone ([11C]NMSP) to study the relationship between oral dose, plasma level, and uptake of ACP-103 in living human brain. The safety of drug administration was also assessed. Four healthy volunteers were examined by PET at baseline, and after the oral administration of various single doses of ACP-103. Two subjects each received 1, 5, and 20 mg doses, and two subjects each received 2, 10, and 100 mg doses, respectively. ACP-103 was well tolerated. Detectable receptor binding was observed at very low ACP-103 serum levels. Cortical [11C]NMSP binding was found to be dose-dependent and fitted well to the law of mass action. A reduction in binding was detectable after an oral dose of ACP-103 as low as 1 mg, and reached near maximal displacement following the 10-20 mg dose. In conclusion, administration of ACP-103 to healthy volunteers was found to be safe and well tolerated, and single oral doses as low as 10 mg were found to fully saturate 5-HT2A receptors in human brain as determined by PET.

Pharmacokinetics, Tolerability, and Safety of ACP‐103 Following Single or Multiple Oral Dose Administration in Healthy Volunteers

The pharmacokinetics, safety, and tolerability of ACP‐103, a selective serotonin 5‐HT2A receptor inverse agonist, were evaluated in 2 double‐blind, placebo‐controlled, dose escalation studies in healthy male volunteers. Pharmacokinetic sampling was measured up to 216 hours after single oral/nasogastric doses of ACP‐103 and after the last dose of once‐daily oral administration of ACP‐103 for 14 days. Single doses of ACP‐103 (20–300 mg) resulted in dose‐proportionate mean Cmax values (9–152 ng/mL) and AUC0–∞ (706–10 798 h·ng/mL), and multiple doses (50–150 mg) resulted in dose‐proportionate mean Cmax, ss (93–248 ng/mL) and AUC0–∞,ss (1839–4680 h·ng/mL). The half‐life of ACP‐103 was approximately 55 hours, with a tmax at 6 hours. ACP‐103 was well tolerated at single doses up to and including 300 mg and multiple doses up to 100 mg once daily for 14 days.

Neuroactive steroids attenuate cocaine-induced sucrose intake in rats, but not cocaine-induced hyperactivity in mice

Abstractu2002Rationale: Neuroactive steroids, including the potent anticonvulsants ganaxolone (3α-hydroxy-3β-methyl-5α-pregnan-20-one) and Co 2-1068 (3β-(4acetylphenyl)ethynyl-3α,21-dihydroxy-5β-20-one-21-hemisuccinate), have recently been shown to protect against cocaine-induced seizures. Objectives: The purpose of the present experiments was to determine whether ganaxolone and Co 2-1068 attenuate acute behavioral effects of cocaine unrelated to seizures. Methods: In the first experiment, the locomotor effects of Co 2-1068 (10–100 mg/ kg), pentobarbital (10–100 mg/kg) and haloperidol (0.03–0.3 mg/kg), alone or in combination with cocaine (5.6–30 mg/kg), were determined in mice. In the second experiment, the effects on sucrose intake of ganaxolone (4–16 mg/kg), Co 2-1068 (8–64 mg/kg), pentobarbital (4–32 mg/kg), and haloperidol (0.04–0.4 mg/kg), alone or in combination with cocaine (4–16 mg/kg), were determined in rats. Results: Cocaine caused a dose-related increase in locomotor activity in mice, whereas Co 2-1068, pentobarbital and haloperidol caused dose-related decreases. The dopamine antagonist haloperidol, at a dose that had no effect on activity by itself, but not Co 2-1068 or pentobarbital, attenuated the cocaine-induced increase in locomotor activity. Cocaine, ganaxolone, Co 2-1068, and haloperidol produced dose-related decreases in sucrose intake in rats; the effects of pentobarbital on sucrose intake were variable. As with locomotor effects, haloperidol attenuated the cocaine-induced decrease in sucrose intake. In addition, cocaine-induced decreases in sucrose intake were attenuated by ganaxolone and Co 2-1068. Pentobarbital had no statistically significant effect on the cocaine dose-response function. Conclusions: These results suggest that the interaction of neuroactive steroids with cocaine extends to pharmacologic actions beyond anticonvulsant efficacy, but that the blockade of behavioral effects of cocaine by neuroactive steroids does not apply to all acute behaviors.

The Effects of Food on the Pharmacokinetics of a Formulated ACP‐103 Tablet in Healthy Volunteers

A CP-103, N-(4-flurophenylmethyl)-N-(1-methylpiperidin-4-yl)-N′-(4-(2-methylpropyloxy) phenylmethyl)carbamide (2R,3R)-dihydroxybutanedioate (2:1), is a potent inverse agonist at serotonin 5-HT2A receptors currently being developed as a novel antipsychotic drug. In a phase I clinical study, ACP103 was found to be safe and well tolerated at single oral doses ranging from 20 to 300 mg and multiple doses up to and including 100 mg daily for 14 days in healthy volunteers. The first pharmacokinetic study in humans was conducted using an oral solution. Administration of this oral solution resulted in a bitter taste and was not well tolerated. In that first study, single doses greater than 50 mg were administered nasogastrically to avoid the local intolerance. ACP-103 was administered in powder-filled capsules for the multiple-dose study. Subsequently, ACP-103 was formulated in an immediate-release coated tablet. The purpose of the present study was to compare the pharmacokinetics after administration of the formulated coated tablet to those after administration of the solution of ACP-103. Furthermore, the effects of food on the pharmacokinetics of ACP-103 after a single oral administration were evaluated in healthy male subjects.