Synthesis and biological investigation of new equatorial (β) stereoisomers of 3-aminotropane arylamides with atypical antipsychotic profile

The antidepressant-like effect and proposed mechanism of action of TPN672MA, a novel serotonin-dopamine receptor modulator for the treatment of schizophrenia

TPN672MA, an innovative antipsychotic drug candidate currently in clinical trials, acts as a dopamine D2/D3 receptor partial agonist, serotonin 5-HT1A receptor agonist, and serotonin 5-HT2A receptor antagonist. Preclinical investigations have demonstrated its potential in treating the core symptoms of schizophrenia. The present study highlights TPN672MA's significant antidepressant-like effects in classical behavioral models, such as the chronic social defeat stress paradigm. The pronounced 5-HT1A receptor agonism and D2/D3 receptor partial agonism of TPN672MA likely contribute to its therapeutic effects in depression. Additionally, TPN672MA's antidepressant-like efficacy may be linked to its ability to enhance the expression levels of brain-derived neurotrophic factor (BDNF) and postsynaptic density protein-95 (PSD95) in the hippocampus. Furthermore, TPN672MA displayed a more rapid onset of antidepressant-like action. In conclusion, TPN672MA represents a promising new drug candidate for the treatment of symptoms of schizophrenia and depression.

Recent advances in dopamine D2 receptor ligands in the treatment of neuropsychiatric disorders

Dopamine is a biologically active amine synthesized in the central and peripheral nervous system. This biogenic monoamine acts by activating five types of dopamine receptors (D_1-5 Rs), which belong to the G protein-coupled receptor family. Antagonists and partial agonists of D₂ Rs are used to treat schizophrenia, Parkinson's disease, depression, and anxiety. The typical pharmacophore with high D₂ R affinity comprises four main areas, namely aromatic moiety, cyclic amine, central linker and aromatic/heteroaromatic lipophilic fragment. From the literature reviewed herein, we can conclude that 4-(2,3-dichlorophenyl), 4-(2-methoxyphenyl)-, 4-(benzo[b]thiophen-4-yl)-1-substituted piperazine, and 4-(6-fluorobenzo[d]isoxazol-3-yl)piperidine moieties are critical for high D₂ R affinity. Four to six atoms chains are optimal for D₂ R affinity with 4-butoxyl as the most pronounced one. The bicyclic aromatic/heteroaromatic systems are most frequently occurring as lipophilic appendages to retain high D₂ R affinity. In this review, we provide a thorough overview of the therapeutic potential of D₂ R modulators in the treatment of the aforementioned disorders. In addition, this review summarizes current knowledge about these diseases, with a focus on the dopaminergic pathway underlying these pathologies. Major attention is paid to the structure, function, and pharmacology of novel D₂ R ligands, which have been developed in the last decade (2010-2021), and belong to the 1,4-disubstituted aromatic cyclic amine group. Due to the abundance of data, allosteric D₂ R ligands and D₂ R modulators from patents are not discussed in this review.

Metabolic stability studies of lead compounds supported by separation techniques and chemometrics analysis

With metabolism being one of the main routes of drug elimination from the body (accounting for removal of around 75% of known drugs), it is crucial to understand and study metabolic stability of drug candidates. Metabolically unstable compounds are uncomfortable to administer (requiring repetitive dosage during therapy), while overly stable drugs increase risk of adverse drug reactions. Additionally, biotransformation reactions can lead to formation of toxic or pharmacologically active metabolites (either less-active than parent drug, or even with different action). There were numerous approaches in estimating metabolic stability, including in vitro, in vivo, in silico, and high-throughput screening to name a few. This review aims at describing separation techniques used in in vitro metabolic stability estimation, as well as chemometric techniques allowing for creation of predictive models which enable high-throughput screening approach for estimation of metabolic stability. With a very low rate of drug approval, it is important to understand in silico methods that aim at supporting classical in vitro approach. Predictive models that allow assessment of certain biological properties of drug candidates allow for cutting not only cost, but also time required to synthesize compounds predicted to be unstable or inactive by in silico models.

Cannabinoid-induced lower lip retraction in rats

RATIONALE

Lower lip retraction (LLR) in rats has been described as a distinctive effect of 5-HT_1A agonists. In the course of evaluating behavioral effects of cannabinoid agonists in rats, LLR effects were evident following injection of several cannabinoid agonists.

OBJECTIVES

To pharmacologically characterize cannabinoid-induced LLR in rats.

METHODS

Lower lip retraction was scored using a 3-point scale for up to 6 h after injection of the cannabinoid agonists Δ⁹-tetrahydrocannabinol (Δ⁹-THC, 1-10 mg/kg), AM7499 (0.01-1.0 mg/kg), or AM2389 (0.003-0.1 mg/kg), or, for comparison, the 5-HT_1A agonist 8-OH-DPAT (0.01-0.3 mg/kg). Next, antagonist effects of rimonabant (1-10 mg/kg) and WAY100635 (0.3 mg/kg) on LLR produced by cannabinoid or 5-HT_1A agonists were evaluated. Lastly, effects of 8-OH-DPAT were determined following pretreatment with AM2389 (0.003-0.01 mg/kg) or Δ⁹-THC (1 mg/kg).

RESULTS

All three cannabinoid agonists produced LLR. Effects of AM2389 were attenuated by both rimonabant and WAY100635 whereas effects of 8-OH-DPAT were antagonized by WAY 100635 but not by rimonabant. Pretreatment with 1 mg/kg Δ⁹-THC or 0.01 mg/kg AM2389 shifted the 8-OH-DPAT dose-effect function for LLR to the left and isobolographic analysis of the data indicates CB1 and 5-HT_1A interactions can be supraadditive.

CONCLUSIONS

Cannabinoid agonists produce LLR in rats, an effect heretofore ascribed only to activity at 5-HT_1A receptors, via CB1 receptor-mediated actions. Co-administration of a cannabinoid agonist and the 5-HT_1A agonist 8-OH-DPAT results in a synergistic effect on LLR.

Synthesis and biological investigations of 3β-aminotropane arylamide derivatives with atypical antipsychotic profile

This work is a continuation of our previous research, concentrating this time on lead structure modification to increase the 5-HT_1A receptor affinity and water solubility of designed compounds. Therefore, the compounds synthesised within the present project included structural analogues of 3β-acylamine derivatives of tropane with the introduction of a methyl substituent in the benzyl ring and a 2-quinoline, 3-quinoline, or 6-quinoline moiety. A series of novel 3β-aminotropane derivatives was evaluated for their affinity for 5-HT_1A, 5-HT_2A, and D₂ receptors, which allowed for the identification of compounds 12e, 12i, and 19a as ligands with highest affinity for the tested receptors; they were then subjected to further evaluation in preliminary in vivo studies. Selected compounds 12i and 19a displayed antipsychotic properties in the d-amphetamine-induced and MK-801-induced hyperlocomotor activity test in mice. Moreover, compound 19a showed significant antidepressant-like activity in the forced swim test in mice.