Differences among conventional, atypical and novel putative D2/5-HT1A antipsychotics on catalepsy-associated behaviour in cynomolgus monkeys

Cannabidiol effects on prepulse inhibition in nonhuman primates

Prepulse inhibition (PPI) of acoustic startle reflex is a well-established behavior paradigm to measure sensorimotor gating deficits. PPI is disrupted in several neuropsychiatric disorders, including schizophrenia. PPI tests can be used to screen new drugs for treatment of such disorders. In this review, we discuss how PPI paradigm can help in screening the therapeutic effects of cannabidiol (CBD). We look into recent literature about CBD effects on PPI response in animal models, especially in nonhuman primates. CBD has been shown to modify PPI inN-methyld-aspartate receptor antagonist models for schizophrenia, both in rodents and in nonhuman primates. These results show CBD as a potential drug for the treatment of neurologic disorders that present alterations in sensorimotor system, such as schizophrenia. Moreover, the PPI paradigm seems to be a useful and relative simple paradigm to test the efficacy of CBD as a potential therapeutic drug.

Distinctive in vitro signal transduction profile of NLX-112, a potent and efficacious serotonin 5-HT1A receptor agonist

Objectives

NLX-112 (befiradol, F13640) is a selective serotonin 5-HT1A receptor agonist. Although it has been tested in vivo, little has been reported on its in vitro signal transduction profile.

Methods

NLX-112 was tested on G-protein activation, inhibition of adenylyl cyclase, ERK1/2 phosphorylation (pERK) and receptor internalization in recombinant cell lines. NLX-112 was also tested on G-protein activation in rat hippocampal membranes. Gα subunit mRNA expression in cell lines and rat brain tissue was quantified by quantitative PCR.

Key findings

For all signalling measures, NLX-112 exhibited agonist efficacy greater than for reference compounds ((±)8-OH-DPAT or buspirone), but similar to the endogenous agonist, serotonin, and was more potent for pERK than other responses. In rat hippocampal membranes, NLX-112 stimulated ‘total G-proteins' but, unlike (±)8-OH-DPAT and buspirone, was more potent for Gαo activation. Cell lines predominantly expressed Gαi1 and Gαi2 mRNA, with low levels of Gαo, whereas in rat brain Gαo subunits showed highest mRNA expression.

Conclusions

Unlike reference compounds, NLX-112 was a highly efficacious agonist in vitro, preferentially activating pERK in cell lines and Gαo proteins in rat hippocampal membranes. However, Gα subunit mRNA levels differ markedly between rat brain and cell lines, warranting caution when extrapolating from recombinant systems to native tissues.

LASSBio-1422: a new molecular scaffold with efficacy in animal models of schizophrenia and disorders of attention and cognition

Aiming to identify new antipsychotic lead-compounds, our group has been working on the design and synthesis of new N-phenylpiperazine derivatives. Here, we characterized LASSBio-1422 as a pharmacological prototype of this chemical series. Adult male Wistar rats and CF1 mice were used for in-vitro and in-vivo assays, respectively. LASSBio-1422 [1 and 5 mg/kg, postoperatively (p.o.)] inhibited apomorphine-induced climbing as well as ketamine-induced hyperlocomotion (1 and 5 mg/kg, p.o.), animal models predictive of efficacy on positive symptoms. Furthermore, LASSBio-1422 (5 mg/kg, p.o.) prevented the prepulse impairment induced by apomorphine, (±)-2,5-dimethoxy-4-iodoamphetamine, and ketamine, as well as the memory impairment induced by ketamine in the novel object-recognition task at the acquisition, consolidation, and retrieval phases of memory formation. Potential extrapyramidal side-effects and sedation were assessed by catatonia, rota-rod, locomotion, and barbiturate sleeping time, and LASSBio-1422 (15 mg/kg, p.o.) did not affect any of the parameters observed. Binding assays showed that LASSBio-1422 has a binding profile different from the known atypical antipsychotic drugs: it does not bind to AMPA, kainate, N-methyl-D-aspartate, glicine, and mGluR2 receptors and has low or negligible affinity for D1, D2, and 5-HT2A/C receptors, but high affinity for D4 receptors (Ki=0.076 µmol/l) and, to a lesser extent, for 5-HT1A receptors (Ki=0.493 µmol/l). The antagonist action of LASSBio-1422 at D4 receptors was assessed through the classical GTP-shift assay. In conclusion, LASSBio-1422 is effective in rodent models of positive and cognitive symptoms of schizophrenia and its ability to bind to D4 and 5-HT1A receptors may at least in part explain its effects in these animal models.

Differential responses to JNJ-37822681, a specific and fast dissociating dopamine D2 receptor antagonist, in cynomolgus monkey and Sprague-Dawley rat general toxicology studies: clinical observations, prolactin levels, mammary histopathology findings and toxicokinetics

JNJ-37822681 is a potent, specific and fast dissociating dopamine D2 receptor antagonist intended for the treatment of schizophrenia. Its nonclinical toxicological profile was investigated in a series of general repeat dose toxicity studies in cynomolgus monkeys and Sprague-Dawley rats. The maximum duration of treatment was 9 and 6 months, respectively. Interspecies differences were noted in the response to JNJ-37822681 in terms of extrapyramidal (EPS)-like clinical signs and prolactin-mediated tissue changes in the mammary gland. Monkeys showed severe EPS-like clinical signs such as abnormal posture, abnormal eye movements and hallucination-like behavior at relatively low exposures compared to those associated with EPS in patients with schizophrenia. The high sensitivity of the monkey to JNJ-37822681-induced EPS-like signs was unexpected based on the fast dissociating properties of the compound. Rats, however, were not prone to EPS. Elevated serum prolactin levels were found in rats and monkeys. While rats showed slight to moderate prolactin-related tissue changes upon histopathological examination in all studies, which among others affected the mammary gland, only minor mammary gland tissue changes were noted in monkeys. Prolactin levels were only slightly increased in patients with schizophrenia receiving relatively high dose levels of JNJ-37822681. The monkey toxicology studies did not provide an exposure-based safety margin, while in rats adverse effects were only noted at exposures considerably higher than those achieved at efficacious plasma concentrations in the clinic. Overall, the available data suggest that the cynomolgus monkey showed better predictivity towards the nature of JNJ-37822681-associated adverse events in humans than the Sprague-Dawley rat.

Nonhuman primates: translational models for predicting antipsychotic-induced movement disorders

Repeated haloperidol treatment administered to nonhuman primates (NHPs) over several months or even years leads to the gradual appearance of drug-induced dystonic reactions in the orofacial region (mouth opening, tongue protrusion or retraction, bar biting) and in the whole body (writhing of the limbs and trunk, bar grasping). The propensity of antipsychotics to induce dystonia in NHPs is not correlated with their propensity to induce catalepsy in rodents, suggesting that the two types of effects are dissociated and may represent distinct aspects of the extrapyramidal symptoms induced by antipsychotics. In view of the clear homology to clinically observed phenomena, antipsychotic-induced dystonias in antipsychotic-primed NHPs would appear to possess a high degree of translational validity. These NHP phenomena could therefore serve as a useful model for predicting the occurrence of similar abnormal movements with novel substances developed for the treatment of schizophrenia or other psychotic disorders. Moreover, the NHP dystonia model could possibly serve as a biomarker for substances that will eventually cause tardive dyskinesia in patients.

Comparative pharmacology of antipsychotics possessing combined dopamine D2 and serotonin 5-HT1A receptor properties

RATIONALE

There is increasing interest in antipsychotics intended to manage positive symptoms via D(2) receptor blockade and improve negative symptoms and cognitive deficits via 5-HT(1A) activation. Such a strategy reduces side-effects such as the extrapyramidal syndrome (EPS), weight gain, and autonomic disturbance liability.

OBJECTIVE

This study aims to review pharmacological literature on compounds interacting at both 5-HT(1A) and D(2) receptors (as well as at other receptors), including aripiprazole, perospirone, ziprasidone, bifeprunox, lurasidone and cariprazine, PF-217830, adoprazine, SSR181507, and F15063.

METHODS

We examine data on in vitro binding and agonism and in vivo tests related to (1) positive symptoms (e.g., psychostimulant-induced hyperactivity or prepulse inhibition deficit), (2) negative symptoms (e.g., phencyclidine-induced social interaction deficits and cortical dopamine release), and (3) cognitive deficits (e.g., phencyclidine or scopolamine-induced memory deficits). EPS liability is assessed by measuring catalepsy and neuroendocrine impact by determining plasma prolactin, glucose, and corticosterone levels.

RESULTS

Compounds possessing "balanced" 5-HT(1A) receptor agonism and D(2) antagonism (or weak partial agonism) and, in some cases, combined with other beneficial properties, such as 5-HT(2A) receptor antagonism, are efficacious in a broad range of rodent pharmacological models yet have a lower propensity to elicit EPS or metabolic dysfunction.

CONCLUSIONS

Recent compounds exhibiting combined 5-HT(1A)/D(2) properties may be effective in treating a broader range of symptoms of schizophrenia and be better tolerated than existing antipsychotics. Nevertheless, further investigations are necessary to evaluate recent compounds, notably in view of their differing levels of 5-HT(1A) affinity and efficacy, which can markedly influence activity and side-effect profiles.