We previously described an integrated in vitro liability assay for seizure, a new approach methodology (NAM) to reduce toxicity due to central nervous system (CNS) liability in drug discovery and development. Here we report the development of SAR (structure activity relationships) to guide drug design away from this liability. SAR test compounds were selected from the Enamine REadily AccesibLe (REAL) database using pharmacophore features and similarity to previous test compounds (amoxapine, diphenhydramine, quetiapine, 4-AP, linopirdine) or to ion channel positive reference compounds (bepridil, NS1619, quinidine, verapamil, XE991). These 88 compounds (10 parent compounds and 78 structurally related derivatives) were screened by automated electrophysiology in cell lines expressing human KV2.1, NaV1.2, the α1β2γ2 GABAA or α4β2 nicotinic receptors to generate IC50 values. Across all four ion channels, the derivative compounds exhibited increased, equivalent or reduced potency compared with the parent compounds, providing a complex and rich dataset for SAR. Regarding individual pharmacophoric features, statistical analysis identified 12 features significantly associated with activity at the α4β2 nicotinic receptor; 4 of these were also significantly associated with activity at KV2.1. Selected parent compounds (amoxapine, diphenhydramine, quetiapine) and structural analogues were screened for seizure-like activity in human induced pluripotent stem cell neurons using microelectrode array. The seizure-like phenotype was altered with the derivatives, as expected from the respective ion channel IC50 values. These data provide insight into specific substructures associated with seizure-like drug toxicity, offering the opportunity to avoid CNS liability in the development of novel compounds, saving time, money and resources.

Amoxapine (AMX) is an FDA-approved tricyclic antidepressant used to treat major depressive disorders by modulating monoaminergic neurotransmitters, including serotonin, dopamine, and noradrenaline. However, its clinical efficacy is limited due to poor aqueous solubility, rapid first-pass metabolism, and extensive biotransformation by cytochrome P450 enzymes, particularly CYP2D6, leading to reduced systemic and brain availability. Bergamottin (BER) and diosmetin (DIO), natural furanocoumarin and flavonoid compounds, respectively, are known inhibitors of CYP3A4 and CYP2D6 and may enhance AMX pharmacokinetics through drug-herb interactions. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantification of amoxapine during pharmacokinetic and neurotransmitter studies. In vitro and in vivo drug-herb interactions of AMX with bergamottin and diosmetin, as well as their impact on brain biodistribution and neurotransmitter levels in mice, were evaluated. In vitro CYP2D6 inhibition assays demonstrated that BER and DIO significantly suppressed CYP2D6-mediated dextromethorphan metabolism in a concentration-dependent manner, while rat liver microsome studies showed markedly improved metabolic stability of AMX, with reduced intrinsic clearance and extended half-life in the presence of BER and DIO compared with AMX alone. In vivo pharmacokinetic evaluation revealed a 1.26-fold and 2.13-fold increase in C max, along with enhanced bioavailability, when AMX was coadministered with bergamottin (BER) and diosmetin (DIO), respectively. Behavioral testing (forced swim test (FST), tail suspension test (TST) and open field test (OFT)) demonstrated significantly improved antidepressant-like responses with combination therapy versus AMX alone. Biodistribution studies confirmed increased AMX accumulation in the hippocampus and cortex, accompanied by elevated monoamine neurotransmitters, including serotonin, dopamine, norepinephrine, and epinephrine. These findings demonstrate that BER and DIO augment the pharmacokinetic and pharmacodynamic profiles of AMX through CYP2D6 inhibition and improved brain delivery, supporting their potential as natural bioenhancers to enhance antidepressant efficacy. This combination strategy represents a promising approach for developing superior AMX-based therapeutic regimens and warrants further clinical investigation.

Toxicity enhancement mediated by plasma protein binding during intoxication remains poorly understood. It is known that in mice, brain penetration of amoxapine (AMX) increases nonlinearly with increasing doses; therefore, this study investigated its potential to enhance toxicity via plasma protein binding. AMX was added to mouse or human plasma and adjusted to therapeutic, toxic, and lethal concentrations. The plasma protein-binding ratio and free AMX concentration were measured using ultrafiltration and equilibrium dialysis. Furthermore, the binding ratios of varying concentrations of chlorpromazine, which is often co-administered with AMX in cases of overdose, was analyzed in the presence of therapeutic AMX concentrations. The binding ratio of AMX exceeded 90%, thereby demonstrating a high binding rate; however, this ratio was lower in human plasma than in mice. A nonlinear increase in free AMX concentration was observed in mouse plasma, particularly at high concentrations. In contrast, free AMX concentration showed a linear increase in human plasma. Neither the therapeutic nor toxic concentration of chlorpromazine produced any visible effects on the plasma protein binding ratio or the free AMX concentration. These results suggest that protein binding of AMX is more readily saturated in mouse plasma than in human plasma. In addition, chlorpromazine inhibits AMX binding to α1-acid glycoprotein; however, AMX may alternatively binds to albumin, which results in no apparent change in the total binding ratio. Further insights into the toxicokinetic interactions mediated by plasma protein binding are also needed for various toxic substances other than AMX.

The human serotonin transporter (SERT) is a pertinent target for many psychiatric therapeutics and recreational drugs including new psychoactive substances. Current techniques to assess SERT inhibition typically monitor the uptake of radiolabeled or fluorescent substrates but face limitations regarding the use of nonendogenous substrates and/or low throughput. Inspired by a previously reported principle, coined 'TRACT' or 'transporter activity through receptor activation', a new bioassay to measure SERT inhibition was developed. The assay principle relies on SERT-mediated uptake of supplied serotonin (5-HT), precluding 5-HT-induced activation of a coexpressed modified serotonin 2A receptor (5-HT2AR). Upon SERT inhibition, more extracellular 5-HT is available for 5-HT2AR-activation, which is monitored via β-arrestin 2 recruitment, using functional complementation of a split-nanoluciferase and a luminescent read-out. Following optimization, the assay was successfully applied to three classes of antidepressants and the designer cathinone naphyrone. Obtained inhibition potencies ranged from 2.61 nM for paroxetine to 348 nM for naphyrone, and good agreement in rank order was obtained when compared with the outcome of a fluorescence-based and a radioactivity-based uptake assay. Our findings demonstrate that the TRACT assay principle is translatable to SERT, allowing the assessment of SERT inhibition via 5-HT2AR activation. Additionally, for amitriptyline and amoxapine, the TRACT assay indicated direct (non-SERT mediated) 5-HT2AR-modulating effects, caused by inverse agonism, as confirmed by the 5-HT2AR βarr2 recruitment assay. We also demonstrate a proof-of-principle for applying this system to detect SERT-mediated efflux. Overall, our findings support the utility of the TRACT assay for the characterization of SERT ligands.

Vitamin B6 (VB6) is a vital coenzyme for δ-aminolevulinic acid synthase (ALAS) in heme biosynthesis. We report a 49-year-old male with severe microcytic anemia and ringed sideroblasts initially diagnosed as myelodysplastic syndrome (MDS). VB6 deficiency, attributed to long-term amoxapine use, was identified. His anemia improved significantly with VB6 supplementation and resolved completely after discontinuing amoxapine. This case highlights the need to consider VB6 deficiency in anemia with ringed sideroblasts.

Drug-induced convulsions/seizures are a serious adverse event in the clinic; however, precise convulsion/seizure risk assessment remains challenging, particularly in the early phase of drug development. There is a demand for reliable in vitro assay systems that can predict in vivo convulsions. Here, we investigated the usefulness of in vitro microelectrode array (MEA) assays using rat primary neurons by comparing them with an in vivo convulsion study for 14 reference drugs known to cause seizure/convulsion: Paroxetine, 4-aminopyridine, pentylenetetrazol, strychnine, amoxapine, fluvoxamine, linopirdine, theophylline, pilocarpine, tramadol, bupropion, diphenhydramine, kainic acid, and veratridine. For the in vitro assay, a culture condition was established that demonstrated stable firing rates and drug responses of neurons and ensured a balanced expression of excitatory and inhibitory neuronal markers. Cultured rat primary cortical neurons were tested by MEA for electrophysiological changes induced by drugs. An MEA parameter, network burst frequency (NBF), was increased in a concentration-dependent manner by some of the drugs tested, demonstrating reproducibility. Rats were intraperitoneally or intravenously given the drugs at doses that did and did not cause convulsions. Concentrations of the drugs in cerebrospinal fluid (CSF), obtained just after convulsion onset, were measured by LC-MS/MS. The NBF threshold for seizure could be used to predict the CSF concentrations of some drugs in rats with convulsions. Thus, an in vitro MEA assay using rat primary neurons can predict the risk of in vivo convulsions, which could be useful for drug screening during the early stage of drug candidate selection.

Gut microbial β-glucuronidase (GUS) plays a key role in metabolizing compounds and influencing disease and drug metabolism, highlighting the need for potent inhibitors to improve drug efficacy and intestinal health. To identify Escherichia coli β-glucuronidase (EcGUS) inhibitors, we designed and synthesized fifty 1,2-benzoselenazol-3-one (BSEA) derivatives using a bioisosterism strategy. Among these, twenty-five BSEA derivatives demonstrated greater inhibitory efficacy than the most potent known EcGUS inhibitor, amoxapine (AMX), with compound 49 showing the strongest activity, achieving an IC50 of 12.9 nM. Structure-inhibitory activity relationship analysis suggested that modifications such as adding benzene rings or nitrogenous heterocycles to the BSEA scaffold enhanced inhibitory activity, influenced by the type and position of substituents. The LC-MS analysis confirmed that compounds 31 and 49 covalently modify Cys197 in EcGUS, and additional covalent linkage of compound 49 was observed on Cys28 and Cys443. In addition, the jump dilution assays proved that compounds 31 was irreversible covalent inhibitors, and its kinetic parameter kinact/KI were determined to be 21292.9 M[-1]s[-1]. The compounds 49 was reversible covalent inhibitors and its apparent steady-state inhibition constant Ki∗[app] were determined to be 23.33 nM. Molecular docking predicted specific interactions, such as hydrogen bonds involving Se and the pyrazole NH of compound 49 with Cys28 and Cys449, which may contribute to its inhibitory action. This study reports the first discovery of covalent inhibitors for EcGUS, with optimized BSEA derivatives acting as novel allosteric covalent inhibitors, revealing structure-activity relationships and molecular determinants that establish their potential in drug development.

Additive free aminolysis method developed for the depolymerization/upcycling of polycarbonates. We report here chemical recycling of polycarbonate under ambient conditions to get its monomer bisphenol A, monoaminocarbamate and biscarbamates in 1 : 2 : 1 ratio respectively. By employing the secondary amine as the aminating reagent, facilitates the depolymerization to work under additive/catalyst free conditions. The developed method deals with depolymerization of waste polycarbonates and works even with late-stage amine derivatives such as amoxapine and desloratadine which are drugs molecules known to treat neurotic disorders and allergies respectively. The reaction can be scaled up and works with similar efficacy which depicts the efficiency of the depolymerization of wasteend-of-life polycarbonate plastic waste. The biscarbamate and bisphenol-A was further subjected for the post functionalization to obtain amides and phenol in good yields.

There are no recommendations based on the efficacy of specific drugs for the treatment of psychotic depression. To address this evidence gap, we did a network meta-analysis to assess and compare the efficacy and safety of pharmacological treatments for psychotic depression.

Alzheimer's disease (AD) is accompanied by behavioral and psychological symptoms of dementia (BPSD), which is often alleviated by treatment with psychotropic drugs, such as antidepressants, hypnotics, and anxiolytics. If these drugs also inhibit acetylcholinesterase (AChE) activity, they may contribute to the suppression of AD progression by increasing brain acetylcholine concentrations. We tested the potential inhibitory effects of 31 antidepressants, 21 hypnotics, and 12 anxiolytics on recombinant human AChE (rhAChE) activity. At a concentration of 10[-4] M, 22 antidepressants, 19 hypnotics, and 11 anxiolytics inhibited rhAChE activity by <20%, whereas nine antidepressants (clomipramine, amoxapine, setiptiline, nefazodone, paroxetine, sertraline, citalopram, escitalopram, and mirtazapine), two hypnotics (triazolam and brotizolam), and one anxiolytic (buspirone) inhibited rhAChE activity by ≥20%. Brotizolam (≥10[-6] M) exhibited stronger inhibition of rhAChE activity than the other drugs, with its pIC50 value being 4.57 ± 0.02. The pIC50 values of the other drugs were <4, and they showed inhibitory activities toward rhAChE at the following concentrations: ≥3 × 10[-6] M (sertraline and buspirone), ≥10[-5] M (amoxapine, nefazodone, paroxetine, citalopram, escitalopram, mirtazapine, and triazolam), and ≥3 × 10[-5] M (clomipramine and setiptiline). Among these drugs, only nefazodone inhibited rhAChE activity within the blood concentration range achievable at clinical doses. Therefore, nefazodone may not only improve the depressive symptoms of BPSD through its antidepressant actions but also slow the progression of cognitive symptoms of AD through its AChE inhibitory actions.