Deciphering Nonbioavailable Substructures Improves the Bioavailability of Antidepressants by Serotonin Transporter.

Inadequate bioavailability is one of the most critical reasons for the failure of oral drug development. However, the way that substructures affect bioavailability remains largely unknown. Serotonin transporter (SERT) inhibitors are first-line drugs for major depression disorder, and improving their bioavailability may be able to decrease side-effects by reducing daily dose. Thus, it is an excellent model to probe the relationship between substructures and bioavailability. Here, we proposed the concept of "nonbioavailable substructures", referring to substructures that are unfavorable to bioavailability. A machine learning model was developed to identify nonbioavailable substructures based on their molecular properties and shows the accuracy of 83.5%. A more potent SERT inhibitor DH4 was discovered with a bioavailability of 83.28% in rats by replacing the nonbioavailable substructure of approved drug vilazodone. DH4 exhibits promising anti-depression efficacy in animal experiments. The concept of nonbioavailable substructures may open up a new venue for the improvement of drug bioavailability.

Novel difluoromethylated 1-(phenylsulfonyl)-4-(piperazin-1-yl)-1H-indole derivatives as potent 5-HT6 receptor antagonist with AMDE-improving properties: Design, synthesis, and biological evaluation.

Serotonin type 6 receptor (5-HT6R) has been considered as a particularly promising target for treating cognitive deficits due to the positive effects of its antagonists in a wide range of memory impairment paradigms. In this study, we designed, synthesized, and evaluated a series of 3-(difluoromethyl)-1-(phenylsulfonyl)-4-(piperazin-1-yl)-1H-indole derivatives as potent 5-HT6R antagonists. Structure-activity relationship study led to the discovery of five compounds (6a, 6m, 6n, 6p and 6q) with potent binding affinity at 5-HT6R. In in vivo pharmacokinetic studies in rats, 6p showed 30-folds higher AUC (267 ng·h/mL) and better bioavailability (34.39 %) than those of 6a (9.37 ng·h/mL and 5.95 %, respectively) by using difluoromethyl group replacing a methyl group. Besides, 6p showed good brain penetration with Cb/Cp ratio ∼6. Based on the pharmacological characteristics and favorable pharmacokinetic properties, 6p was further chosen to evaluate cognition-enhancing property in the preliminary in vivo models. It is identified that 6p not only prevented scopolamine-induced learning deficits in the novel object recognition test but also rescued the recognition barrier caused by scopolamine. Finally, the combination of 6p and donepezil produces synergistic effects on increasing the acetylcholine levels in the intracerebral hippocampus. In light of these findings, we propose 6p as a potential 5-HT6R antagonist for treatment of AD.

Novel difluoromethyl-containing 1-((4-methoxy-3-(piperazin-1-yl)phenyl)sulfonyl)-1H-indole scaffold as potent 5-HT6R antagonists: Design, synthesis, biological evaluation, and early in vivo cognition-enhancing studies.

Herein, a series of novel 1-((4-methoxy-3-(piperazin-1-yl)phenyl)sulfonyl)- 1H-indole derivatives were designed and synthesized via hybridization strategy of idalopirdine and SB-271046. The optimal compound C14 (Ki = 0.085 nM), with difluoromethyl on C3 position on indole scaffold, increased the affinity for the 5-HT6R up to 10-folds than idalopirdine (Ki = 0.83 nM). Additionally, C14 had good pharmacokinetic properties and in vitro metabolic properties. Finally, C14 could efficiently reverse the scopolamine induced emotional memory deficits in novel object recognition assay in rats. Thus, we propose C14 might be considered as a new cognition-enhancing agent and the further studies are now underway in our laboratory.

Design, synthesis and biological evaluation of pyridinylmethylenepiperidine derivatives as potent 5-HT1F receptor agonists for migraine therapy.

Migraine is a common neurovascular disease which has been classified as the sixth most disabling disorder. Current migraine therapy was triptans, however, riptans can cause contraction of blood vessels. Therefore, novel drugs without cardiovascular effects emerged, such as CGRP and selective 5-HT1F receptor agonists. In this work, a series of pyridinylmethylenepiperidine derivatives were designed, synthesized and evaluated for their 5-HT1F receptor agonist activity. The results in vitro showed that compound C1-C6 displayed potent agonist activities compared with positive drug lasmiditan. Pharmacokinetic properties in rat indicated that 2,4,6-trifluoro-N-(6-(fluoro(1-methylpiperidin-4-ylidene)methyl)pyridin-2-yl)benzamide (C5) possessed high AUC and good bioavailability. In two rodent models of migraine, C5 significantly inhibited dural plasma protein extravasation and c-fos expression in the trigeminal nucleus caudalis. Moreover, C5 showed no effect on vasoconstriction. Through these studies, we identified C5 as a potent 5-HT1F receptor agonist for migraine therapy.