An automated liquid chromatography-mass spectrometry process to determine metabolic stability half-life and intrinsic clearance of drug candidates by substrate depletion

Bioisosteric analogs of MDMA: Improving the pharmacological profile?

3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') is re-emerging in clinical settings as a candidate for the treatment of specific neuropsychiatric disorders (e.g. post-traumatic stress disorder) in combination with psychotherapy. MDMA is a psychoactive drug, typically regarded as an empathogen or entactogen, which leads to transporter-mediated monoamine release. Despite its therapeutic potential, MDMA can induce dose-, individual-, and context-dependent untoward effects outside safe settings. In this study, we investigated whether three new methylenedioxy bioisosteres of MDMA improve its off-target profile. In vitro methods included radiotracer assays, transporter electrophysiology, bioluminescence resonance energy transfer and fluorescence-based assays, pooled human liver microsome/S9 fraction incubations, metabolic stability studies, isozyme mapping, and liquid chromatography coupled to high-resolution mass spectrometry. In silico methods included molecular docking. Compared with MDMA, all three MDMA bioisosteres (ODMA, TDMA, and SeDMA) showed similar pharmacological activity at human serotonin, dopamine, and norepinephrine transporters (hSERT, hDAT, and hNET, respectively) but decreased agonist activity at 5-HT2A/2B/2C receptors. Regarding their hepatic metabolism, they differed from MDMA, with N-demethylation being the only metabolic route shared, and without forming phase II metabolites. In addition, TDMA showed an enhanced intrinsic clearance in comparison to its congeners. Additional screening for their interaction with human organic cation transporters (hOCTs) and plasma membrane monoamine transporter (hPMAT) revealed a weaker interaction of the MDMA analogs with hOCT1, hOCT2, and hPMAT. Our findings suggest that these new MDMA bioisosteres might constitute appealing therapeutic alternatives to MDMA, sparing the primary pharmacological activity at hSERT, hDAT, and hNET, but displaying a reduced activity at 5-HT2A/2B/2C receptors and alternative hepatic metabolism. Whether these MDMA bioisosteres may pose lower risk alternatives to the clinically re-emerging MDMA warrants further studies.

Discovery and Optimization of N-Arylated Tetracyclic Dicarboximides That Target Primary Glioma Stem-like Cells

We recently discovered a novel N-aryl tetracyclic dicarboximide MM0299 (1) with robust activity against glioma stem-like cells that potently and selectively inhibits lanosterol synthase leading to the accumulation of the toxic shunt metabolite 24(S),25-epoxycholesterol. Herein, we delineate a systematic and comprehensive SAR study that explores the structural space surrounding the N-aryl tetracyclic dicarboximide scaffold. A series of 100 analogs were synthesized and evaluated for activity against the murine glioma stem-like cell line Mut6 and for metabolic stability in mouse liver S9 fractions. This study led to several analogs with single-digit nanomolar activity in Mut6 glioblastoma cells that were metabolically stable in S9 fractions. In vivo pharmacokinetic analysis of selected analogs identified compound 52a (IC50 = 63 nM; S9 T1/2 > 240 min) which was orally available (39% plasma; 58% brain) and displayed excellent brain exposure. Chronic oral dosing of 52a during a 2-week tolerability study indicated no adverse effect on body weight nor signs of hematologic, liver, or kidney toxicity.

In Silico Assisted Identification, Synthesis, and In Vitro Pharmacological Characterization of Potent and Selective Blockers of the Epilepsy-Associated KCNT1 Channel

Gain-of-function (GoF) variants in KCNT1 channels cause severe, drug-resistant forms of epilepsy. Quinidine is a known KCNT1 blocker, but its clinical use is limited due to severe drawbacks. To identify novel KCNT1 blockers, a homology model of human KCNT1 was built and used to screen an in-house library of compounds. Among the 20 molecules selected, five (CPK4, 13, 16, 18, and 20) showed strong KCNT1-blocking ability in an in vitro fluorescence-based assay. Patch-clamp experiments confirmed a higher KCNT1-blocking potency of these compounds when compared to quinidine, and their selectivity for KCNT1 over hERG and Kv7.2 channels. Among identified molecules, CPK20 displayed the highest metabolic stability; this compound also blocked KCNT2 currents, although with a lower potency, and counteracted GoF effects prompted by 2 recurrent epilepsy-causing KCNT1 variants (G288S and A934T). The present results provide solid rational basis for future design of novel compounds to counteract KCNT1-related neurological disorders.

Metabolic profile of N-ethylhexedrone, N-ethylpentedrone, and 4-chloromethcathinone in urine samples by UHPLC-QTOF-HRMS

Forensic laboratories are constantly required to identify new drugs and their metabolites. N-ethylhexedrone (NEH, HEXEN), N-Ethylpentedrone (NEP), and 4-Chloromethcathinone (4-CMC, clephedrone) are synthetic substances structurally related to natural cathinone, alkaloid present in the leaves of the Catha edulis (Khat) plant. These synthetic cathinones (SC) are members of the heterogenous family of new psychoactive substances (NPS) that raised major concerns in scientific and forensic communities over the past years due to their widespread consumption. In this context, we investigated their metabolic profile using of UHPLC-QTOF-HRMS to elucidate the distribution of the parent drug and its metabolites in urine samples over time. Initially, both male and female volunteers were divided into three groups and eight subjects of each group were administered intranasally or orally with one SC (20-40 mg of NEH or NEP intranasal, 100-150 mg of 4-CMC oral). Urine samples were collected at 0-2 and 2-4 or 2-5 h. Urine (50 μL) was diluted 1:2 with acetonitrile/methanol (95:5) and injected into the UHPLC-QTOF-HRMS. Phase-I and phase-II metabolites were identified on the basis of fragmentation patterns and exact masses. Several phase-I and glucuronide-phase-II metabolites were identified in urine samples. Keto group reduction, hydroxylation and dealkylation were the common metabolic pathways identified for all cathinones and the presence of NEH-glucuronide, NEP-glucuronide and 4-CMC-glucuronide was also relevant. Significant is the slower metabolite formation for 4-CMC, which was detected at high concentrations in its original form even 5 h after administration, due to its long half-life and low intrinsic clearance compared to the other SCs. UHPLC-QTOF-HRMS demonstrated a considerable capability to semi-quantify the three synthetic cathinones and identify the target metabolites with high reliability. The introduction of new target compounds improves the efficiency of toxicological screening analysis on real samples and extends the window of detection of the SCs in biological matrices.

Short peptides based on the conserved regions of MIEN1 protein exhibit anticancer activity by targeting the MIEN1 signaling pathway

Migration and invasion enhancer 1 (MIEN1) overexpression characterizes several cancers and facilitates cancer cell migration and invasion. Leveraging conserved immunoreceptor tyrosine-based activation motif and prenylation motifs within MIEN1, we identified potent anticancer peptides. Among them, bioactive peptides LA3IK and RP-7 induced pronounced transcriptomic and protein expression changes at sub-IC50 concentrations. The peptides effectively inhibited genes and proteins driving cancer cell migration, invasion, and epithelial-mesenchymal transition pathways, concurrently suppressing epidermal growth factor-induced nuclear factor kappa B nuclear translocation in metastatic breast cancer cells. Specifically, peptides targeted the same signal transduction pathway initiated by MIEN1. Molecular docking and CD spectra indicated the formation of MIEN1-peptide complexes. The third-positioned isoleucine in LA3IK and CVIL motif in RP-7 were crucial for inhibiting breast cancer cell migration. This is evident from the limited migration inhibition observed when MDA-MB-231 cells were treated with scrambled peptides LA3IK SCR and RP-7 SCR. Additionally, LA3IK and RP-7 effectively suppressed tumor growth in an orthotopic breast cancer model. Notably, mice tolerated high intraperitoneal (ip) peptide doses of 90 mg/Kg well, surpassing significantly lower doses of 5 mg/Kg intravenously (iv) and 30 mg/Kg intraperitoneally (ip) used in both in vivo pharmacokinetic studies and orthotopic mouse model assays. D-isomers of LA3IK and RP-7 showed enhanced anticancer activity compared to their L-isomers. D-LA3IK remained stable in mouse plasma for 24 h with 75% remaining, exhibiting superior pharmacokinetic properties over D/L-RP-7. In summary, our findings mark the first report of short peptides based on MIEN1 protein sequence capable of inhibiting cancer signaling pathways, effectively impeding cancer progression both in vitro and in vivo.

Peptidomimetics as potent dual SARS-CoV-2 cathepsin-L and main protease inhibitors: In silico design, synthesis and pharmacological characterization

In this paper we present the design, synthesis, and biological evaluation of a new series of peptidomimetics acting as potent anti-SARS-CoV-2 agents. Starting from our previously described Main Protease (MPro) and Papain Like Protease (PLPro) dual inhibitor, CV11, here we disclose its high inhibitory activity against cathepsin L (CTSL) (IC50 = 19.80 ± 4.44 nM), an emerging target in SARS-CoV-2 infection machinery. An in silico design, inspired by the structure of CV11, led to the development of a library of peptidomimetics showing interesting activities against CTSL and Mpro, allowing us to trace the chemical requirements for the binding to both enzymes. The screening in Vero cells infected with 5 different SARS-CoV-2 variants of concerns, highlighted sub-micromolar activities for most of the synthesized compounds (13, 15, 16, 17 and 31) in agreement with the enzymatic inhibition assays results. The compounds showed lack of activity against several different RNA viruses except for the 229E and OC43 human coronavirus strains, also characterized by a cathepsin-L dependent release into the host cells. The most promising derivatives were also evaluated for their chemical and metabolic in-vitro stability, with derivatives 15 and 17 showing a suitable profile for further preclinical characterization.

Lead to hit ruthenium-cyclopentadienyl anticancer compounds: Cytotoxicity against breast cancer cells, metabolic stability and metabolite profiling

The successful choice of hit compounds during drug development programs involves the integration of structure-activity relationship (SAR) studies with pharmacokinetic determinations, including metabolic stability assays and metabolite profiling. A panel of nine ruthenium-cyclopentadienyl (RuCp) compounds with the general formula [Ru(η5-C5H4R)(PPh3)(bipyR')]+ (with R = H, CHO, CH2OH; R' = H, CH3, CH2OH, CH2Biotin) has been tested against hormone-dependent MCF-7 and triple negative MDA-MB-231 breast cancer cells. In general, all compounds showed important cytotoxicity against both cancer cell lines and were able to inhibit the formation of MDA-MB-231 colonies in a dose-dependent manner, while showing selectivity for cancer cells over normal fibroblasts. Among them, four compounds stood out as lead structures to be further studied. Cell distribution assays revealed their preference for the accumulation at cell membrane (Ru quantification by ICP-MS) and the mechanism of cell death seemed to be mediated by apoptosis. Potential structural liabilities of lead compounds were subsequently flagged upon in vitro metabolic stability assays and metabolite profiling. The implementation of this integrated strategy led to the selection of RT151 as a promising hit compound.

An Ultrafast UPLC-MS/MS Method for Characterizing the In Vitro Metabolic Stability of Acalabrutinib

Acalabrutinib, commercially known as Calquence®, is a pharmacological molecule that has robust inhibitory activity against Bruton tyrosine kinase. The medicine in question was carefully developed by the esteemed pharmaceutical company AstraZeneca. The FDA granted authorization on 21 November 2019 for the utilization of acalabrutinib (ACB) in the treatment of small lymphocytic lymphoma (SLL) or chronic lymphocytic leukemia (CLL) in adult patients. The aim of this study was to develop a UPLC-MS/MS method that is effective, accurate, environmentally sustainable, and has a high degree of sensitivity. The methodology was specifically developed with the intention of quantifying ACB in human liver microsomes (HLMs). The methodology described above was subsequently utilized to assess the metabolic stability of ACB in HLMs in an in vitro environment. The validation procedures for the UPLC-MS/MS method in the HLMs were conducted in accordance with the bioanalytical method validation criteria established by the U.S.- DA. The utilization of the StarDrop software (version 6.6), which integrates the P450 metabolic module and DEREK software (KB 2018 1.1), was employed for the purpose of evaluating the metabolic stability and identifying potential hazardous alarms associated with the chemical structure of ACB. The calibration curve, as established by the ACB, demonstrated a linear correlation across the concentration range of 1 to 3000 ng/mL in the matrix of HLMs. The present study conducted an assessment of the accuracy and precision of the UPLC-MS/MS method in quantifying inter-day and intra-day fluctuations. The inter-day accuracy demonstrated a spectrum of values ranging from -1.00% to 8.36%, whilst the intra-day accuracy presented a range of values spanning from -2.87% to 4.11%. The t1/2 and intrinsic clearance (Clint) of ACB were determined through in vitro testing to be 20.45 min and 39.65 mL/min/kg, respectively. The analysis concluded that the extraction ratio of ACB demonstrated a moderate level, thus supporting the recommended dosage of ACB (100 mg) to be administered twice daily for the therapeutic treatment of persons suffering from B-cell malignancies. Several computational tools have suggested that introducing minor structural alterations to the butynoyl group, particularly the alpha, beta-unsaturated amide moiety, or substituting this group during the drug design procedure, could potentially enhance the metabolic stability and safety properties of novel derivatives in comparison to ACB.

Evaluation of Alectinib Metabolic Stability in HLMs Using Fast LC-MS/MS Method: In Silico ADME Profile, P450 Metabolic Lability, and Toxic Alerts Screening

Alectinib, also known as Alecensa®, is prescribed for the therapeutic treatment of individuals diagnosed with metastatic non-small cell lung cancer (NSCLC) who have a specific genetic mutation referred to as anaplastic lymphoma kinase (ALK) positivity. The Food and Drug Administration granted regular approval to alectinib, a drug developed by Hoffmann-La Roche, Inc. (Basel, Switzerland)/Genentech, Inc. (South San Francisco, CA, USA), on 6 November 2017. The screening of the metabolic stability and identification of hazardous alarms within the chemical structure of ALC was conducted using the StarDrop software package (version 6.6), which incorporates the P450 metabolic module and DEREK software (KB 2018 1.1). The primary aim of this investigation was to develop a high-throughput and accurate LC-MS/MS technique for the quantification of ALC in the metabolic matrix (human liver microsomes; HLMs). The aforementioned methodology was subsequently employed to assess the metabolic stability of ALC in HLMs through in vitro tests, with the obtained results further validated using in silico software. The calibration curve of the ALC showed a linear correlation that exists within the concentration range from 1 to 3000 ng/mL. The LC-MS/MS approach that was recommended exhibited accuracy and precision levels for both inter-day and intra-day measurements. Specifically, the accuracy values ranged from -2.56% to 3.45%, while the precision values ranged from -3.78% to 4.33%. The sensitivity of the established approach was proved by its ability to adhere to an LLOQ of 0.82 ng/mL. The half-life (t1/2) and intrinsic clearance (Clint) of ALC were estimated to be 22.28 min and 36.37 mL/min/kg, correspondingly, using in vitro experiments. The ALC exhibited a moderate extraction ratio. The metabolic stability and safety properties of newly created derivatives can be enhanced by making modest adjustments to the morpholine and piperidine rings or by substituting the substituent, as per computational software. In in silico ADME prediction, ALC was shown to have poor water solubility and high gastrointestinal absorption along with inhibition of some cytochrome P450s (CYP2C19 and CYP2C9) without inhibition of others (CYP1A2, CYP3A4, and CYP2D6) and P-glycoprotein substrate. The study design that involves using both laboratory experiments and different in silico software demonstrates a novel and groundbreaking approach in the establishment and uniformization of LC-MS/MS techniques for the estimation of ALC concentrations, identifying structural alerts and the assessment of its metabolic stability. The utilization of this study strategy has the potential to be employed in the screening and optimization of prospective compounds during the drug creation process. This strategy may also facilitate the development of novel derivatives of the medicine that maintain the same biological action by targeted structural modifications, based on an understanding of the structural alerts included within the chemical structure of ALC.

Rapid high performance liquid chromatography method for erlotinib quantification in vitro: Application to study the effect of resveratrol on metabolism and cellular uptake of erlotinib

BACKGROUND

Erlotinib is a selective epidermal growth factor receptor inhibitor that is used for the treatment of non-small cell lung cancer and pancreatic cancer. Its metabolism is mainly mediated by cytochrome P450 3A (CYP 3A). Resveratrol, a natural compound found in many plants and supplements, is known to inhibit CYP3A enzyme, therefore, it may act as an inhibitor for the metabolism of erlotinib.

OBJECTIVE

Development of a rapid high performance liquid chromatography with photodiode array detection (HPLC-PDA) method for the quantification of erlotinib in liver microsomes and cancer cells and its application to study resveratrol effect on metabolism and cellular uptake of erlotinib.

METHODS

HPLC-PDA was used to develop an efficient bioanalytical method with a 2.5-min runtime preceded by a simple protein precipitation step. The method was validated according to the European Medicines Agency guidelines. Erlotinib metabolic stability and resveratrol effect on erlotinib metabolite formation were evaluated in rat liver microsomes. Furthermore, the method was used to measure the intracellular concentrations of erlotinib in cancer colorectal cells and investigating resveratrol effect on the cellular uptake of erlotinib.

RESULTS

A rapid HPLC-PDA method was developed and validated for the first time to address potential drug interaction of erlotinib with resveratrol. Resveratrol was a strong inhibitor of erlotinib metabolism in vitro with IC50  = 4.03 μM. Resveratrol, however, had no effect on erlotinib cellular uptake after 1 h incubation in human colorectal cancer cells.

CONCLUSION

The study suggests that resveratrol may produce a potential herb-drug interaction with erlotinib at the metabolism level and should be investigated in patients in the clinic.

Dimeric 2-aminoimidazoles are highly active adjuvants for gram-positive selective antibiotics against Acinetobacter baumannii

The Centers for Disease Control and Prevention (CDC) reports that hospital acquired infections have increased by 65% since 2019. One of the main contributors is the gram-negative bacterium Acinetobacter baumannii. Previously, we reported aryl 2-aminoimidazole (2-AI) adjuvants that potentiate macrolide antibiotics against A. baumannii. Macrolide antibiotics are typically used to treat infections caused by gram-positive bacteria, but are ineffective against most gram-negative bacteria. We describe a new class of dimeric 2-AIs that are highly active macrolide adjuvants, with lead compounds lowering minimum inhibitory concentrations (MICs) to or below the gram-positive breakpoint level against A. baumannii. The parent dimer lowers the clarithromycin (CLR) MIC against A. baumannii 5075 from 32 μg/mL to 1 μg/mL at 7.5 μM (3.4 μg/mL), and a subsequent structure activity relationship (SAR) study identified several compounds with increased activity. The lead compound lowers the CLR MIC to 2 μg/mL at 1.5 μM (0.72 μg/mL), far exceeding the activity of both the parent dimer and the previous lead aryl 2-AI. Furthermore, these dimeric 2-AIs exhibit considerably reduced mammalian cell toxicity compared to aryl-2AI adjuvants, with IC50s of the two lead compounds against HepG2 cells of >200 μg/mL, giving therapeutic indices of >250.

HPLC methods for studying pharmacokinetics of tivozanib and in vitro metabolic interaction with dexamethasone in rat

Tivozanib is a recently approved tyrosine kinase inhibitor for the treatment of renal cell carcinoma. In this work, two new HPLC methods coupled with fluorescence (FLD), or photodiode array detectors (PDA) were developed and used for the first time for tivozanib quantification in rat plasma and liver microsomes. The described methods were efficient with a 4-min runtime employing a Gemini-NX C₁₈ column (50 × 2.1 mm, 3 µm) and a mobile phase of acetonitrile and ammonium acetate buffer (pH 4.7, 10 mM) (40:60, v/v) delivered at a flow rate of 0.4 mL/min. The use of HPLC-FLD allowed the quantification of 50 ng/ mL tivozanib using only 100 µL rat plasma. The HPLC-FLD method was validated according to the US food and drug administration (FDA) bioanalytical guidelines and was applied successfully in a rat pharmacokinetic study (n = 7) following oral administration of 1 mg/ kg tivozanib. Furthermore, HPLC-PDA was used for monitoring the depletion of 1 μM (454.9 ng/mL) tivozanib in rat liver microsomes and was applied to study the effect of dexamethasone induction on tivozanib metabolism in vitro. Results showed that dexamethasone enhanced the intrinsic clearance of tivozanib by 60 % suggesting a potential drug-drug interaction at the metabolism level. Dexamethasone is commonly used in the management of cancer disease and thus coadministration with tivozanib therapy may cause treatment failure in patients. The simplicity, speed and cost-effectiveness of the reported methods are ideal for supporting in vivo and in vitro tivozanib studies, including drug-drug interaction studies, particularly in bioanalytical labs lacking LC-MS/MS capabilities.

Assessment of In Silico and In Vitro Selpercatinib Metabolic Stability in Human Liver Microsomes Using a Validated LC-MS/MS Method

Selpercatinib (SLP; brand name Retevmo®) is a selective and potent RE arranged during transfection (RET) inhibitor. On 21 September 2022, the FDA granted regular approval to SLP (Retevmo, Eli Lilly, and Company). It is considered the only and first RET inhibitor for adults with metastatic or locally advanced solid tumors with RET gene fusion. In the current experiment, a highly specific, sensitive, and fast liquid chromatography tandem mass spectrometry (LC-MS/MS) method for quantifying SLP in human liver microsomes (HLMs) was developed and applied to the metabolic stability evaluation of SLP. The LC-MS/MS method was validated following the bioanalytical methodology validation guidelines outlined by the FDA (linearity, selectivity, matrix effect, accuracy, precision, carryover, and extraction recovery). SLP was detected by a triple quadrupole detector (TQD) using a positive ESI source and multiple reaction monitoring (MRM) mode for mass spectrometric analysis and estimation of analytes ions. The IS-normalized matrix effect and extraction recovery were acceptable according to the FDA guidelines for the bioanalysis of SLP. The SLP calibration standards were linear from 1 to 3000 ng/mL HLMs matrix, with a regression equation (y = 1.7298x + 3.62941) and coefficient of variation (r2 = 0.9949). The intra-batch and inter-batch precision and accuracy of the developed LC-MS/MS method were −6.56–5.22% and 5.08–3.15%, respectively. SLP and filgotinib (FLG) (internal standard; IS) were chromatographically separated using a Luna 3 µm PFP (2) stationary phase (150 × 4.6 mm) with an isocratic mobile phase at 23 ± 1 °C. The limit of quantification (LOQ) was 0.78 ng/mL, revealing the LC-MS/MS method sensitivity. The intrinsic clearance and in vitro t1/2 (metabolic stability) of SLP in the HLMs matrix were 34 mL/min/kg and 23.82 min, respectively, which proposed an intermediate metabolic clearance rate of SLP, confirming the great value of this type of kinetic experiment for more accurate metabolic stability predictions. The literature review approved that the established LC-MS/MS method is the first developed and reported method for quantifying SLP metabolic stability.

Development of an LC-MS/MS Method for Quantification of Sapitinib in Human Liver Microsomes: In Silico and In Vitro Metabolic Stability Evaluation

Sapitinib (AZD8931, SPT) is a tyrosine kinase inhibitor of the epidermal growth factor receptor (EGFR) family (pan-erbB). In multiple tumor cell lines, STP has been shown to be a much more potent inhibitor of EGF-driven cellular proliferation than gefitinib. In the current study, a highly sensitive, rapid, and specific LC-MS/MS analytical method for the estimation of SPT in human liver microsomes (HLMs) was established with application to metabolic stability assessment. The LC-MS/MS analytical method was validated in terms of linearity, selectivity, precision, accuracy, matrix effect, extraction recovery, carryover, and stability following the FDA guidelines for bioanalytical method validation. SPT was detected using electrospray ionization (ESI) as an ionization source under multiple reaction monitoring (MRM) in the positive ion mode. The IS-normalized matrix factor and extraction recovery were acceptable for the bioanalysis of SPT. The SPT calibration curve was linear, from 1 ng/mL to 3000 ng/mL HLM matrix samples, with a linear regression equation of y = 1.7298x + 3.62941 (r² = 0.9949). The intraday and interday accuracy and precision values of the LC-MS/MS method were -1.45-7.25% and 0.29-6.31%, respectively. SPT and filgotinib (FGT) (internal standard; IS) were separated through the use of an isocratic mobile phase system with a Luna 3 µm PFP(2) column (150 × 4.6 mm) stationary phase column. The limit of quantification (LOQ) was 0.88 ng/mL, confirming the LC-MS/MS method sensitivity. The intrinsic clearance and in vitro half-life of STP were 38.48 mL/min/kg and 21.07 min, respectively. STP exhibited a moderate extraction ratio that revealed good bioavailability. The literature review demonstrated that the current analytical method is the first developed LC-MS/MS method for the quantification of SPT in an HLM matrix with application to SPT metabolic stability evaluation.

Selective and brain-penetrant lanosterol synthase inhibitors target glioma stem-like cells by inducing 24(S),25-epoxycholesterol production

Glioblastoma (GBM) is an aggressive adult brain cancer with few treatment options due in part to the challenges of identifying brain-penetrant drugs. Here, we investigated the mechanism of MM0299, a tetracyclic dicarboximide with anti-glioblastoma activity. MM0299 inhibits lanosterol synthase (LSS) and diverts sterol flux away from cholesterol into a "shunt" pathway that culminates in 24(S),25-epoxycholesterol (EPC). EPC synthesis following MM0299 treatment is both necessary and sufficient to block the growth of mouse and human glioma stem-like cells by depleting cellular cholesterol. MM0299 exhibits superior selectivity for LSS over other sterol biosynthetic enzymes. Critical for its application in the brain, we report an MM0299 derivative that is orally bioavailable, brain-penetrant, and induces the production of EPC in orthotopic GBM tumors but not normal mouse brain. These studies have implications for the development of an LSS inhibitor to treat GBM or other neurologic indications.

Metabolism-Guided Optimization of Tryptophanol-Derived Isoindolinone p53 Activators

For the first time, the pharmacokinetic (PK) profile of tryptophanol-derived isoindolinones, previously reported as p53 activators, was investigated. From the metabolites' identification, performed by liquid chromatography coupled to high resolution tandem mass spectrometry (LC-HRMS/MS), followed by their preparation and structural elucidation, it was possible to identify that the indole C2 and C3 are the main target of the cytochrome P450 (CYP)-promoted oxidative metabolism in the tryptophanol-derived isoindolinone scaffold. Based on these findings, to search for novel p53 activators a series of 16 enantiopure tryptophanol-derived isoindolinones substituted with a bromine in indole C2 was prepared, in yields of 62-89%, and their antiproliferative activity evaluated in human colon adenocarcinoma HCT116 cell lines with and without p53. Structural optimization led to the identification of two (S)-tryptophanol-derived isoindolinones 3.9-fold and 1.9-fold more active than hit SLMP53-1, respectively. Compounds' metabolic stability evaluation revealed that this substitution led to a metabolic switch, with the impact of Phase I oxidative metabolism being minimized. Through differential scanning fluorimetry (DSF) experiments, the most active compound of the series in cell assays led to an increase in the protein melting temperature (Tm) of 10.39 °C, suggesting an effective binding to wild-type p53 core domain.

Metabolic stability and metabolite profiling of emerging synthetic cathinones

Synthetic cathinones constitute the second largest groups of new psychoactive substances (NPS), which are especially popular among adolescents and young adults. Due to their potential toxicity, the recreational use of these NPS constitute a serious worldwide public health problem. However, their fast appearance in the market renders the continuous updating of NPS information highly challenging for forensic authorities. The unavailability of pharmacokinetic data for emerging NPS is critical for forensic and clinical verifications. With the ultimate goal of having a proactive approach towards the NPS issue, high resolution mass spectrometry was used in the current work to assess preliminary pharmacokinetic data for 8 selected cathinones: 4 reported substances (4-CIC, 3-CMC, 4-CMC and 4-MEAP) and 4 previously unreported ones (3-CIC, 4-MDMB, 4-MNEB and 4-MDMP) for which the emergence on the NSP market is expected to be eminent, were also included in this study. Based on the calculation of pharmacokinetic parameters, half-life and intrinsic clearance, 4-CMC and 4-MDMB are low and high clearance compounds, respectively, and all the remaining cathinones included in this study are intermediate clearance compounds. This fact anticipates the key role of metabolites as suitable biomarkers to extend detection windows beyond those provided by the parent cathinones. Reduction of the keto group and hydroxylation on the alkyl chains were the common metabolic pathways identified for all cathinones. However, the relative importance of these metabolic transformations is dependent on the cathinone substituents. The glucuronic acid conjugation to metabolites stemming for keto group reduction constituted the sole Phase II transformation identified. To our knowledge, this study constitutes the first metabolite profiling of the already reported synthetic cathinones 4-CIC, 3-CMC and 4-CMC. Noteworthy is the fact that 3-CMC accounts for almost a quarter of the quantity of powders seized during 2020. The analytical methods developed, and the metabolites characterized, are now available to be included in routine screening methods to attest the consumption of the 8 cathinones studied.

In silico and in vitro ADME-Tox analysis and in vivo pharmacokinetic study of representative pan-PDE inhibitors from the group of 7,8-disubstituted derivatives of 1,3-dimethyl-7H-purine-2,6-dione

Phosphodiesterase (PDE) inhibitors represent a wide class of chemically different compounds that have been extensively studied in recent years. Their anti-inflammatory and anti-fibrotic effects are particularly desirable in the treatment of chronic respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD). Due to diversified expression of individual PDEs within cells and/or tissues as well as PDE signaling compartmentalization, pan-PDE inhibitors (compounds capable of simultaneously blocking various PDE subtypes) are of particular interest. Recently, a large group of 7,8-disubstituted derivatives of 1,3-dimethyl-7H-purine-2,6-dione (theophylline) was designed and synthesized. These compounds were characterized as potent pan-PDE inhibitors and their prominent anti-inflammatory and anti-fibrotic activity in vitro has been proved. Herein, we investigated a general in vitro safety profile and pharmacokinetic characteristics of two leading compounds from this group: a representative compound with N'-benzylidenebutanehydrazide moiety (38) and a representative derivative containing N-phenylbutanamide fragment (145). Both tested pan-PDE inhibitors revealed no cytotoxic, mutagenic, and genotoxic activity in vitro, showed moderate metabolic stability in mouse and human liver microsomes, as well as fell into the low or medium permeation category. Additionally, 38 and 145 revealed a lack of interaction with adenosine receptors, including A1, A2A, and A2B. Pharmacokinetic analysis revealed that both tested 7,8-disubstituted derivatives of 1,3-dimethyl-7H-purine-2,6-dione were effectively absorbed from the peritoneal cavity. Simultaneously, they were extensively distributed to mouse lungs and after intraperitoneal (i.p.) administration were detected in bronchoalveolar lavage fluid. These findings provide evidence that investigated compounds represent a new drug candidates with a favorable in vitro safety profile and satisfactory pharmacokinetic properties after a single i.p. administration. As the next step, further pharmacokinetic studies after multiple i.p. and p.o. doses will be conducted to ensure effective 38 and 145 serum and lung concentrations for a longer period of time. In summary, 7,8-disubstituted derivatives of 1,3-dimethyl-7H-purine-2,6-dione represent a promising compounds worth testing in animal models of chronic respiratory diseases, the etiology of which involves various PDE subtypes.

HPLC with Fluorescence and Photodiode Array Detection for Quantifying Capmatinib in Biological Samples: Application to In Vivo and In Vitro Studies

Capmatinib, a recently approved tyrosine kinase inhibitor, is used for the treatment of non-small cell lung cancer. We describe two new HPLC methods for capmatinib quantification in vivo and in vitro. HPLC with a fluorescence detection method was used to quantify capmatinib in plasma for the first time. The method was successfully applied in a pharmacokinetic study following a 10 mg/kg oral dose of capmatinib given to rats. The chromatographic separation was performed using a Eurospher II 100-3 C18H (50 × 4 mm, 3 µm) column and a mobile phase containing 10 mM of ammonium acetate buffer (pH 5.5): acetonitrile (70:30, v/v), at a flow rate of 2.0 mL min^-1. The study also describes the use of HPLC-PDA for the first time for the determination of capmatinib in human liver microsomes and describes its application to study its metabolic stability in vitro. Our results were in agreement with those reported using LC-MS/MS, demonstrating the reliability of the method. The study utilized a Gemini-NX C18 column and a mobile phase containing methanol: 20 mM ammonium formate buffer pH 3.5 (53:47, v/v), delivered at a flow rate of 1.1 mL min^-1. These methods are suitable for supporting pharmacokinetic studies, particularly in bioanalytical labs lacking LC-MS/MS capabilities.

Orally Bioavailable Quinoxaline Inhibitors of 15-Prostaglandin Dehydrogenase (15-PGDH) Promote Tissue Repair and Regeneration

15-Prostaglandin dehydrogenase (15-PGDH) regulates the concentration of prostaglandin E2 in vivo. Inhibitors of 15-PGDH elevate PGE2 levels and promote tissue repair and regeneration. Here, we describe a novel class of quinoxaline amides that show potent inhibition of 15-PGDH, good oral bioavailability, and protective activity in mouse models of ulcerative colitis and recovery from bone marrow transplantation.

Enhancing Repair of Oxidative DNA Damage with Small-Molecule Activators of MTH1

Impaired DNA repair activity has been shown to greatly increase rates of cancer clinically. It has been hypothesized that upregulating repair activity in susceptible individuals may be a useful strategy for inhibiting tumorigenesis. Here, we report that selected tyrosine kinase (TK) inhibitors including nilotinib, employed clinically in the treatment of chronic myeloid leukemia, are activators of the repair enzyme Human MutT Homolog 1 (MTH1). MTH1 cleanses the oxidatively damaged cellular nucleotide pool by hydrolyzing the oxidized nucleotide 8-oxo-2'-deoxyguanosine (8-oxo-dG)TP, which is a highly mutagenic lesion when incorporated into DNA. Structural optimization of analogues of TK inhibitors resulted in compounds such as SU0448, which induces 1000 ± 100% activation of MTH1 at 10 μM and 410 ± 60% at 5 μM. The compounds are found to increase the activity of the endogenous enzyme, and at least one (SU0448) decreases levels of 8-oxo-dG in cellular DNA. The results suggest the possibility of using MTH1 activators to decrease the frequency of mutagenic nucleotides entering DNA, which may be a promising strategy to suppress tumorigenesis in individuals with elevated cancer risks.

Optimization of 2-Amino-4,6-diarylpyrimidine-5-carbonitriles as Potent and Selective A1 Antagonists

We herein document a large collection of 108 2-amino-4,6-disubstituted-pyrimidine derivatives as potent, structurally simple, and highly selective A₁AR ligands. The most attractive ligands were confirmed as antagonists of the canonical cyclic adenosine monophosphate pathway, and some pharmacokinetic parameters were preliminarilly evaluated. The library, built through a reliable and efficient three-component reaction, comprehensively explored the chemical space allowing the identification of the most prominent features of the structure–activity and structure–selectivity relationships around this scaffold. These included the influence on the selectivity profile of the aromatic residues at positions R⁴ and R⁶ of the pyrimidine core but most importantly the prominent role to the unprecedented A₁AR selectivity profile exerted by the methyl group introduced at the exocyclic amino group. The structure–activity relationship trends on both A₁ and A_2AARs were conveniently interpreted with rigorous free energy perturbation simulations, which started from the receptor-driven docking model that guided the design of these series.

Discovery and Investigation of 1-[4-(2-Aminoethoxy)Phenylcarbonyl]- 3,5-Bis-(Benzylidene)-4-Piperidones as Candidate Antineoplastic Agents: Our Last 15 Years Study

This review outlines the discovery and development of a novel series of 1-[4-2- aminoethoxy)phenylcarbonyl]-3,5-bis-(benzylidene)-4-piperidones (5-8) as potential drug candidates over the last 15 years in our laboratory. Many of these compounds demonstrate excellent cytotoxic properties and are often more potent than contemporary anticancer drugs. Two highly important features of many of these molecules are first, the greater tumour-selective toxicity and second, the ability of these molecules to act as modulators of multi-drug resistance. The modes of action of some of the potent compounds are by apoptosis induction, generation of reactive oxygen species, activation of certain caspases and affecting mitochondrial functions. These molecules also display promising antimalarial and antimycobacterial properties. In a short term toxicity study, these molecules are well tolerated in mice. Structure-activity relationships and a drug delivery system along with pharmacokinetic studies and metabolic stability of these compounds, have been presented. The positive characteristics associated with the series (5-8) warrant their further evaluations as candidate antineoplastic drug candidates.

Tryptophanol-Derived Oxazolopyrrolidone Lactams as Potential Anticancer Agents against Gastric Adenocarcinoma

Gastric cancer is one of the deadliest cancers in modern societies, so there is a high level of interest in discovering new drugs for this malignancy. Previously, we demonstrated the ability of tryptophanol-derived polycyclic compounds to activate the tumor suppressor protein p53, a relevant therapeutic target in cancer. In this work, we developed a novel series of enantiomerically pure tryptophanol-derived small molecules to target human gastric adenocarcinoma (AGS) cells. From an initial screening of fourteen compounds in AGS cell line, a hit compound was selected for optimization, leading to two derivatives selective for AGS gastric cells over other types of cancer cells (MDA-MB-231, A-549, DU-145, and MG-63). More importantly, the compounds were non-toxic in normal cells (HEK 293T). Additionally, we show that the growth inhibition of AGS cells induced by these compounds is mediated by apoptosis. Stability studies in human plasma and human liver microsomes indicate that the compounds are stable, and that the major metabolic transformations of these molecules are mono- and di-hydroxylation of the indole ring.

Macrocyclic Gq Protein Inhibitors FR900359 and/or YM-254890-Fit for Translation?

Guanine nucleotide-binding proteins (G proteins) transduce extracellular signals received by G protein-coupled receptors (GPCRs) to intracellular signaling cascades. While GPCRs represent the largest class of drug targets, G protein inhibition has only recently been recognized as a novel strategy for treating complex diseases such as asthma, inflammation, and cancer. The structurally similar macrocyclic depsipeptides FR900359 (FR) and YM-254890 (YM) are potent selective inhibitors of the Gq subfamily of G proteins. FR and YM differ in two positions, FR being more lipophilic than YM. Both compounds are utilized as pharmacological tools to block Gq proteins in vitro and in vivo. However, no detailed characterization of FR and YM has been performed, which is a prerequisite for the compounds' translation into clinical application. Here, we performed a thorough study of both compounds' physicochemical, pharmacokinetic, and pharmacological properties. Chemical stability was high across a large range of pH values, with FR being somewhat more stable than YM. Oral bioavailability and brain penetration of both depsipeptides were low. FR showed lower plasma protein binding and was metabolized significantly faster than YM by human and mouse liver microsomes. FR accumulated in lung after chronic intratracheal or intraperitoneal application, while YM was more distributed to other organs. Most strikingly, the previously observed longer residence time of FR resulted in a significantly prolonged pharmacologic effect as compared to YM in a methacholine-induced bronchoconstriction mouse model. These results prove that changes within a molecule which seem marginal compared to its structural complexity can lead to crucial pharmacological differences.

Fungal-Selective Resorcylate Aminopyrazole Hsp90 Inhibitors: Optimization of Whole-Cell Anticryptococcal Activity and Insights into the Structural Origins of Cryptococcal Selectivity

The essential eukaryotic chaperone Hsp90 regulates the form and function of diverse client proteins, many of which govern thermotolerance, virulence, and drug resistance in fungal species. However, use of Hsp90 inhibitors as antifungal therapeutics has been precluded by human host toxicities and suppression of immune responses. We recently described resorcylate aminopyrazoles (RAPs) as the first class of Hsp90 inhibitors capable of discriminating between fungal (Cryptococcus neoformans, Candida albicans) and human isoforms of Hsp90 in biochemical assays. Here, we report an iterative structure-property optimization toward RAPs capable of inhibiting C. neoformans growth in culture. In addition, we report the first X-ray crystal structures of C. neoformans Hsp90 nucleotide binding domain (NBD), as the apoprotein and in complexes with the non-species-selective Hsp90 inhibitor NVP-AUY922 and three RAPs revealing unique ligand-induced conformational rearrangements, which reaffirm the hypothesis that intrinsic differences in protein flexibility can confer selective inhibition of fungal versus human Hsp90 isoforms.

Metabolic profiling of synthetic cannabinoid 5F-ADB and identification of metabolites in authentic human blood samples via human liver microsome incubation and ultra-high-performance liquid chromatography/high-resolution mass spectrometry

RATIONALE

Indazole carboxamide synthetic cannabinoids, a prevalent class of recreational drugs, are a major clinical, forensic and public health challenge. One such compound, 5F-ADB, has been implicated in fatalities worldwide. Understanding its metabolism and distribution facilitates the development of laboratory assays to substantiate its consumption. Synthetic cannabinoid metabolites have been extensively studied in urine; studies identifying metabolites in blood are limited and no data on the metabolic stability (half-life, clearance and extraction ratio) of 5F-ADB have been published prior to this report.

METHODS

The in vitro metabolism of 5F-ADB was elucidated via incubation with human liver microsomes for 2 h at 37°C. Samples were collected at multiple time points to determine its metabolic stability. Upon identification of metabolites, authentic forensic human blood samples underwent liquid-liquid extraction and were screened for metabolites. Extracts were analyzed via ultra-high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC/QTOFMS) operated in positive electrospray ionization mode.

RESULTS

Seven metabolites were identified including oxidative defluorination (M1); carboxypentyl (M2); monohydroxylation of the fluoropentyl chain (M3.1/M3.2) and indazole ring system (M4); ester hydrolysis (M5); and ester hydrolysis with oxidative defluorination (M6). The half-life (3.1 min), intrinsic clearance (256.2 mL min^-1  kg^-1 ), hepatic clearance (18.6 mL min^-1 kg^-1 ) and extraction ratio (0.93) were determined for the first time. In blood, M1 was present in each sample as the most abundant substance; two samples contained M5; one contained 5F-ADB, M1 and M5.

CONCLUSIONS

5F-ADB is rapidly metabolized in HLM. 5F-ADB, M1 and M5 are pharmacologically active at the cannabinoid receptors (CB₁ /CB₂ ) and M1 and M5 may contribute to a user's impairment profile. The results demonstrate that it is imperative that synthetic cannabinoid assays screen for pharmacologically active metabolites, especially for drugs with short half-lives. The authors propose that M1 and M5 are appropriate markers to include in laboratory blood tests screening for 5F-ADB.

Discovery of BMS-986144, a Third-Generation, Pan-Genotype NS3/4A Protease Inhibitor for the Treatment of Hepatitis C Virus Infection

The discovery of a pan-genotypic hepatitis C virus (HCV) NS3/4A protease inhibitor based on a P1-P3 macrocyclic tripeptide motif is described. The all-carbon tether linking the P1-P3 subsites of 21 is functionalized with alkyl substituents, which are shown to effectively modulate both potency and absorption, distribution, metabolism, and excretion (ADME) properties. The CF₃Boc-group that caps the P3 amino moiety was discovered to be an essential contributor to metabolic stability, while positioning a methyl group at the C1 position of the P1' cyclopropyl ring enhanced plasma trough values following oral administration to rats. The C7-fluoro, C6-CD₃O substitution pattern of the P2* isoquinoline heterocycle of 21 was essential to securing the targeted potency, pharmacokinetic (PK), and toxicological profiles. The C6-CD₃O redirected metabolism away from a problematic pathway, thereby circumventing the time-dependent cytochrome P (CYP) 450 inhibition observed with the C6-CH₃O prototype.

Privileged scaffold-based design to identify a novel drug-like 5-HT7 receptor-preferring agonist to target Fragile X syndrome

Recent preclinical studies have shown that activation of the serotonin 5-HT₇ receptor has the potential to treat neurodevelopmental disorders such as Fragile X syndrome, a rare disease characterized by autistic features. With the aim to provide the scientific community with diversified drug-like 5-HT₇ receptor-preferring agonists, we designed a set of new long-chain arylpiperazines by exploiting structural fragments present in clinically approved drugs or in preclinical candidates (privileged scaffolds). The new compounds were synthesized, tested for their affinity at 5-HT₇ and 5-HT_1A receptors, and screened for their in vitro stability to microsomal degradation and toxicity. Selected compounds were characterized as 5-HT₇ receptor-preferring ligands, endowed with high metabolic stability and low toxicity. Compound 7g emerged as a drug-like 5-HT₇ receptor-preferring agonist capable to rescue synaptic plasticity and attenuate stereotyped behavior in a mouse model of Fragile X syndrome.

Minimalistic Principles for Designing Small Molecules with Multiple Reactivities against Pathological Factors in Dementia

Multiple pathogenic elements, including reactive oxygen species, amyloidogenic proteins, and metal ions, are associated with the development of neurodegenerative disorders. We report minimalistic redox-based principles for preparing compact aromatic compounds by derivatizing the phenylene moiety with various functional groups. These molecular agents display enhanced reactivities against multiple targets such as free radicals, metal-free amyloid-β (Aβ), and metal-bound Aβ that are implicated in the most common form of dementia, Alzheimer's disease (AD). Mechanistic studies reveal that the redox properties of these reagents are essential for their function. Specifically, they engage in oxidative reactions with metal-free and metal-bound Aβ, leading to chemical modifications of the Aβ peptides to form covalent adducts that alter the aggregation of Aβ. Moreover, the administration of the most promising candidate significantly attenuates the amyloid pathology in the brains of AD transgenic mice and improves their cognitive defects. Our studies demonstrate an efficient and effective redox-based strategy for incorporating multiple functions into simple molecular reagents.

Toxicokinetics and toxicodynamics of the fentanyl homologs cyclopropanoyl-1-benzyl-4´-fluoro-4-anilinopiperidine and furanoyl-1-benzyl-4-anilinopiperidine

The two fentanyl homologs cyclopropanoyl-1-benzyl-4´-fluoro-4-anilinopiperidine (4F-Cy-BAP) and furanoyl-1-benzyl-4-anilinopiperidine (Fu-BAP) have recently been seized as new psychoactive substances (NPS) on the drugs of abuse market. As their toxicokinetic and toxicodynamic characteristics are completely unknown, this study focused on elucidating their in vitro metabolic stability in pooled human liver S9 fraction (pHLS9), their qualitative in vitro (pHLS9), and in vivo (zebrafish larvae) metabolism, and their in vitro isozyme mapping using recombinant expressed isoenzymes. Their maximum-tolerated concentration (MTC) in zebrafish larvae was studied from 0.01 to 100 µM. Their µ-opioid receptor (MOR) activity was analyzed in engineered human embryonic kidney (HEK) 293 T cells. In total, seven phase I and one phase II metabolites of 4F-Cy-BAP and 15 phase I and four phase II metabolites of Fu-BAP were tentatively identified by means of liquid chromatography high-resolution tandem mass spectrometry, with the majority detected in zebrafish larvae. N-Dealkylation, N-deacylation, hydroxylation, and N-oxidation were the most abundant metabolic reactions and the corresponding metabolites are expected to be promising analytical targets for toxicological analysis. Isozyme mapping revealed the main involvement of CYP3A4 in the phase I metabolism of 4F-Cy-BAP and in terms of Fu-BAP additionally CYP2D6. Therefore, drug-drug interactions by CYP3A4 inhibition may cause elevated drug levels and unwanted adverse effects. MTC experiments revealed malformations and changes in the behavior of larvae after exposure to 100 µM Fu-BAP. Both substances were only able to produce a weak activation of MOR and although toxic effects based on MOR activation seem unlikely, activity at other receptors cannot be excluded.

In vitro-in vivo extrapolation of metabolic clearance using human liver microsomes: factors showing variability and their normalization

In vitro-in vivo extrapolation (IVIVE) using human liver microsomes has been widely used to predict metabolic clearance, but some of the factors used in the process of prediction show variability for the same compound: notably, microsomal intrinsic clearance values corrected by the unbound fraction (CL_{int, u}), physiological parameters used for scale-up, and the source of in vivo clearance data.The purpose of this study was to assess the correlation between in vitro and in vivo CL_int with a focus on factors showing variability using four cytochrome P450 (CYP)3A substrates.We surveyed in vivo clearance values in literature and also determined the microsomal CL_{int, u} values. A scaling factor (SF_direct) was defined as in vivo CL_int divided by the microsomal CL_{int, u}, which ranged from 1190 to 2310 (mg protein per kg body weight). The application of a mean SF_direct of 1600 (mg protein per kg body weight) and further normalization by the microsomal CL_{int, u} values of midazolam, the most commonly used substrate, resulted in improved prediction accuracy for CL_{int, u} values from various microsomal batches.The results suggest the normalization of variability might be useful for predicting the in vivo CL_int.

Toxicokinetic Studies and Analytical Toxicology of the New Synthetic Opioids Cyclopentanoyl-Fentanyl and Tetrahydrofuranoyl-Fentanyl

The growing number of new synthetic opioids (NSO) on the new psychoactive substances (NPS) market bears new challenges in toxicology. As their toxicodynamics and particularly their toxicokinetics are usually unknown, impact on human health is not yet fully understood. Detection of the 2 NSO cyclopentanoyl-fentanyl (CP-F) and tetrahydrofuranoyl-fentanyl (THF-F) was first reported in 2016. Both were involved in several fatal intoxication cases, but no detailed information about their toxicological characteristics is available so far. The main purpose of this study was therefore to investigate the in vitro toxicokinetics and in vivo analytical toxicology of CP-F and THF-F by means of liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS). These studies included metabolic stability, phase I and II metabolism, isozyme mapping, plasma protein binding and detectability in LC-HRMS/MS standard urine screening approaches (SUSA) using rat urine samples. In total, 12 phase I metabolites of CP-F and 13 of THF-F were identified, among them 9 metabolites described for the first time. Overall, N-dealkylations, hydroxylations and dihydroxylations were the main metabolic reactions. The cytochrome P450 (CYP) isozymes mainly involved were CYP2D6 and CYP3A4, leading to elevated drug levels and intoxications in CYP2D6 poor metabolizers. CP-F showed a high plasma protein binding of 99%, which may increase the risk of toxicity by simultaneous intake of other highly bound drugs. Detectability studies showed that neither the parent compounds nor their metabolites were detectable in rat urine using LC-HRMS/MS SUSA. However, a more sophisticated analytical strategy was successfully applied and should be used for analytical confirmation of an intake of CP-F and/or THF-F.

Enhancement of the Antioxidant Activity and Neurotherapeutic Features through Pyridol Addition to Tetraazamacrocyclic Molecules

Alzheimer's and other neurodegenerative diseases are chronic conditions affecting millions of individuals worldwide. Oxidative stress is a consistent component described in the development of many neurodegenerative diseases. Therefore, innovative strategies to develop drug candidates that overcome oxidative stress in the brain are needed. To target these challenges, a new, water-soluble 12-membered tetraaza macrocyclic pyridinophane L4 was designed and produced using a building-block approach. Potentiometric data show that the neutral species of L4 provides interesting zwitterionic behavior at physiological pH, akin to amino acids, and a nearly ideal isoelectric point of 7.3. The copper(II) complex of L4 was evaluated by X-ray diffraction and cyclic voltammetry to show the potential modes of antioxidant activity derived, which was also demonstrated by 2,2-diphenyl-1-picrylhydrazyl and coumarin carboxylic acid antioxidant assays. L4 was shown to have dramatically enhanced antioxidant activity and increased biological compatibility compared to parent molecules reported previously. L4 attenuated hydrogen peroxide (H2O2)-induced cell viability loss more efficiently than precursor molecules in the mouse hippocampal HT-22 cell model. L4 also showed potent (fM) level protection against H2O2 cell death in a BV2 microglial cell culture. Western blot studies indicated that L4 enhanced the cellular antioxidant defense capacity via Nrf2 signaling activation as well. Moreover, a low-cost analysis and high metabolic stability in phase I and II models were observed. These encouraging results show how the rational design of lead compounds is a suitable strategy for the development of treatments for neurodegenerative diseases where oxidative stress plays a substantial role.

Microbial biotransformation of some novel hydantoin derivatives: Perspectives for bioremediation of potential sunscreen agents

Having identified novel hydantoin derivatives (compounds 1-5) demonstrating promising photoprotective capacity against UV radiation, and understainding the problem of the biotic and abiotic degradation of UV filters, the aim of the study was to evaluate their metabolic fate with the environmental fungus Cunninghamella echinulata. In parallel, compound 1 in vitro microsomal metabolic pattern was evaluated. Finally, in silico toxicity of test compounds and their biotransformation products was estimated, and parent compounds photostability was assessed. The study demonstrated the capacity for C. echinulata to metabolize 1-5, which were biotransformed to a greater extent than the standard UV filter. O-dealkylation of the side chains attached to the phenyl or hydantoin rings, and hydroxylation of the phenyl ring occurred during microbial transformation. O-dealkylation product was a unique metabolite observed in microsomal biotransformation of 1, being its intrinsic clearance in the medium category range. In silico study demonstrated that compounds 1-5 have low toxicity risk. Among the resulting metabolites, four can increase the risk of reproductive effects as shown by OSIRIS prediction. Noteworthy, all indicated metabolites belong to minor metabolites, except for compound 3 major metabolite. Moreover, the results of the photostability study showed that 1-5 were considered to be photostable. To sum up, the obtained in vitro biotransformation, photostability, and in silico toxicity results encourage further studies on hydantoin derivatives as potential UV photoprotective agents. The presented biotransformation profile of compounds 1-5 by C. echinulata suggests that these compounds may follow a similar biodegradation fate when released into the environment.

In vitro metabolism and in vivo pharmacokinetics of bentysrepinine (Y101), an investigational new drug for anti-HBV-infected hepatitis: focus on interspecies comparison

The objective of this study was to clarify the species differences of pharmacokinetics of Y101 (N-[N-benzoyl-O-(2-dimethylaminoethyl)-l-tyrosyl]-l-phenylalaninol hydrochloride), a derivative of herbal ingredient with anti-HBV hepatitis activity, in rats, dogs, monkeys and humans.The metabolic stability and metabolite identification studies using liver microsomes in vitro, plasma protein binding using a rapid equilibrium dialysis in vitro, pharmacokinetic studies in vivo were carried out to evaluate the interspecies differences. The toxicokinetic study in monkeys was also investigated.The metabolic profiles were similar in monkeys and humans, which were significant different from rats and dogs in vitro. In vitro plasma protein binding showed no major differences between species with medium to high protein binding rates. After single oral dose to rats, dogs, and monkeys, the absolute oral bioavailability of Y101 was 44.9%, 43.1%, and 19.2%, respectively. There was no accumulation for Y101 toxicokinetics in monkeys after oral administration for 90 d.The metabolic profiles indicated monkey was the very animal model for preclinical safety evaluation of Y101. Our results have demonstrated the favorable pharmacokinetics profile of Y101, which supports the clinical trials in humans.

Toxicokinetics and analytical toxicology of the abused opioid U-48800 - in vitro metabolism, metabolic stability, isozyme mapping, and plasma protein binding

Due to the risk of new synthetic opioids (NSOs) for human health, the knowledge of their toxicokinetic characteristics is important for clinical and forensic toxicology. U-48800 is an NSO structurally non-related to classical opioids such as morphine or fentanyl and offered for abuse. As toxicokinetic data of U-48800 is not currently available, the aims of this study were to identify the in vitro metabolites of U-48800 in pooled human liver S9 fraction (pS9), to map the isozymes involved in the initial metabolic steps, and to determine further toxicokinetic data such as metabolic stability, including the in vitro half-life (t_1/2 ), and the intrinsic (CL_int ) and hepatic clearance (CL_h ). Furthermore, drug detectability studies in rat urine should be done using hyphenated mass spectrometry. In total, 13 phase I metabolites and one phase II metabolite were identified. N-Dealkylation, hydroxylation, and their combinations were the predominant metabolic reactions. The isozymes CYP2C19 and CYP3A4 were mainly involved in these initial steps. CYP2C19 poor metabolizers may suffer from an increased U-48800 toxicity. The in vitro t_1/2 and CL_int could be rated as moderate, compared to structural related compounds. After administration of an assumed consumer dose to rats, the unchanged parent compound was found only in very low abundance but three metabolites were detected additionally. Due to species differences, metabolites found in rats might be different from those in humans. However, phase I metabolites found in rat urine, the parent compound, and additionally the N-demethyl metabolite should be used as main targets in toxicological urine screening approaches.

Dialing in on pharmacological features for a therapeutic antioxidant small molecule

The pyridinophane molecule L2 (3,6,9,15-tetraazabicyclo[9.3.1]penta-deca-1(15),11,13-trien-13-ol) has shown promise as a therapuetic for neurodegenerative diseases involving oxidative stress and metal ion misregulation. Protonation and metal binding stability constants with Mg2+, Ca2+, Cu2+, and Zn2+ ions were determined to further explore the therapeutic and pharmacological potential of this water soluble small molecule. These studies show that incorporation of an -OH group in position 4 of the pyridine ring decreases the pI values compared to cyclen and L1 (3,6,9,15-tetraazabicyclo[9.3.1]penta-deca-1(15),11,13-triene). Furthermore, this approach tunes the basicity of the tetra-aza macrocyclic ligand through the enhanced resonance stabilization of the -OH in position 4 and rigidity of the pyridine ring such that L2 has increased basicity compared to previously reported tetra-aza macrocycles. A metal binding preference for Cu2+, a redox cycling agent known to produce oxidative stress, indicates that this would be the in vivo metal target of L2. However, the binding constant of L2 with Cu2+ is moderated compared to cyclen due to the rigidity of the ligand and shows how ligand design can be used to tune metal selectivity. An IC50 = 298.0 μM in HT-22 neuronal cells was observed. Low metabolic liability was determined in both Phase I and II in vitro models. Throughout these studies other metal binding systems were used for comparison and as appropriate controls. The reactivity reported to date and pharmacological features described herein warrant further studies in vivo and the pursuit of L2 congeners using the knowledge that pyridine substitution in a pyridinophane can be used to tune the structure of the ligand and retain the positive therapeutic outcomes.

Metabolic stability and its role in the discovery of new chemical entities

Determination of metabolic profiles of new chemical entities is a key step in the process of drug discovery, since it influences pharmacokinetic characteristics of therapeutic compounds. One of the main challenges of medicinal chemistry is not only to design compounds demonstrating beneficial activity, but also molecules exhibiting favourable pharmacokinetic parameters. Chemical compounds can be divided into those which are metabolized relatively fast and those which undergo slow biotransformation. Rapid biotransformation reduces exposure to the maternal compound and may lead to the generation of active, non-active or toxic metabolites. In contrast, high metabolic stability may promote interactions between drugs and lead to parent compound toxicity. In the present paper, issues of compound metabolic stability will be discussed, with special emphasis on its significance, in vitro metabolic stability testing, dilemmas regarding in vitro-in vivo extrapolation of the results and some aspects relating to different preclinical species used in in vitro metabolic stability assessment of compounds.

Design and Synthesis of TASIN Analogues Specifically Targeting Colorectal Cancer Cell Lines with Mutant Adenomatous Polyposis Coli (APC)

Despite advances in targeted anticancer therapies, there are still no small-molecule-based therapies available that specifically target colorectal cancer (CRC) development and progression, the second leading cause of cancer deaths. We previously disclosed the discovery of truncating adenomatous polyposis coli (APC)-selective inhibitor 1 (TASIN-1), a small molecule that specifically targets colorectal cancer cells lines with truncating mutations in the adenomatous polyposis coli (APC) tumor suppressor gene through inhibition of cholesterol biosynthesis. Here, we report a medicinal chemistry evaluation of a collection of TASIN analogues and activity against colon cancer cell lines and an isogenic cell line pair reporting on the status of APC-dependent selectivity. A number of potent and selective analogues were identified, including compounds with good metabolic stability and pharmacokinetic properties. The compounds reported herein represent a first-in-class genotype-selective series that specifically target apc mutations present in the majority of CRC patients and serve as a translational platform toward a targeted therapy for colon cancer.

In vitro metabolism of synthetic cannabinoid AM1220 by human liver microsomes and Cunninghamella elegans using liquid chromatography coupled with high resolution mass spectrometry

Purpose

Identifying intake of synthetic cannabinoids generally requires the metabolism data of the drugs so that appropriate metabolite markers can be targeted in urine testing. However, the continuous appearance of new cannabinoids during the last decade has made it difficult to keep up with all the compounds including {1-[(1-methylpiperidin-2-yl)methyl]-1H-indol-3-yl}(naphthalen-1-yl)methanone (AM1220). In this study, metabolism of AM1220 was investigated with human liver microsomes and the fungus Cunninghamella elegans.

Methods

Metabolic stability of AM1220 was analysed by liquid chromatography–tandem mass spectrometry in multiple reaction monitoring mode after 1 µM incubation in human liver microsomes for 30 min. Tentative structure elucidation of metabolites was performed on both human liver microsome and fungal incubation samples using liquid chromatography–high-resolution mass spectrometry.

Results

Half-life of AM1220 was estimated to be 3.7 min, indicating a high clearance drug. Nine metabolites were detected after incubating human liver microsomes while seven were found after incubating Cunninghamella elegans, leading to 11 metabolites in total (five metabolites were common to both systems). Demethylation, dihydrodiol formation, combination of the two, hydroxylation and dihydroxylation were the observed biotransformations.

Conclusions

Three most abundant metabolites in both human liver microsomes and Cunninghamella elegans were desmethyl, dihydrodiol and hydroxy metabolites, despite different isomers of dihydrodiol and hydroxy metabolites in each model. These abundant metabolites can potentially be useful markers in urinalysis for AM1220 intake.

Biotransformation of 4-fluoro-N-(1-{2-[(propan-2-yl)phenoxy]ethyl}-8-azabicyclo[3.2.1]octan-3-yl)-benzenesulfonamide, a novel potent 5-HT7 receptor antagonist with antidepressant-like and anxiolytic properties: In vitro and in silico approach

The aim of the study was to investigate the metabolism of 4-fluoro-N-(1-{2-[(propan-2-yl)phenoxy]ethyl}-8-azabicyclo[3.2.1]octan-3-yl)-benzenesulfonamide (PZ-1150), a novel 5-HT₇ receptor antagonist with antidepressant-like and anxiolytic properties, by the following three ways: in vitro with microsomes; in vitro employing Cunninghamella echinulata, and in silico using MetaSite. Biotransformation of PZ-1150 with microsomes resulted in five metabolites, while transformation with C. echinulata afforded two metabolites. In both models, the predominant metabolite occurred due to hydroxylation of benzene ring. In silico data coincide with in vitro experiments, as three MetaSite metabolites matched compounds identified in microsomal samples. In human liver microsomes PZ-1150 exhibited in vitro half-life of 64 min, with microsomal intrinsic clearance of 54.1 μL/min/mg and intrinsic clearance of 48.7 mL/min/kg. Therefore, PZ-1150 is predicted to be a high-clearance agent. The study demonstrated the applicability of using microsomal model coupled with microbial model to elucidate the metabolic pathways of compounds and comparison with in silico metabolite predictions.

Kinetic and metabolic profiles of synthetic cannabinoids NNEI and MN-18

In 2014 and 2015, synthetic cannabinoid receptor agonists NNEI (N-1-naphthalenyl-1-pentyl-1H-indole-3-carboxamide) and MN-18 (N-1-naphthalenyl-1-pentyl-1H-indazole-3-carboxamide) were detected in recreationally used and abused products in multiple countries, and were implicated in episodes of poisoning and toxicity. Despite this, the pharmacokinetic profiles of NNEI and MN-18 have not been characterized. In the present study NNEI and MN-18 were incubated in rat and human liver microsomes and hepatocytes, to estimate kinetic parameters and to identify potential metabolic pathways, respectively. These parameters and pathways were then examined in vivo, via analysis of blood and urine samples from catheterized male rats following intraperitoneal (3 mg/kg) administration of NNEI and MN-18. Both NNEI and MN-18 were rapidly cleared by rat and human liver microsomes, and underwent a range of oxidative transformations during incubation with rat and human hepatocytes. Several unique metabolites were identified for the forensic identification of NNEI and MN-18 intake. Interestingly, NNEI underwent a greater number of biotransformations (20 NNEI metabolites versus 10 MN-18 metabolites), yet parent MN-18 was eliminated at a faster rate than NNEI in vivo. Additionally, in vivo elimination was more rapid than in vitro estimates. These data highlight that even closely related synthetic cannabinoids can possess markedly distinct pharmacokinetic profiles, which can vary substantially between in vitro and in vivo models.

In Vitro Metabolite Profiling of ADB-FUBINACA, A New Synthetic Cannabinoid

Metabolite profiling of novel psychoactive substances (NPS) is critical for documenting drug consumption. N-(1-amino-3,3-dimethyl-1-oxobutan-2-yl)-1-(4-fluorobenzyl)-1H-indazole-3-carboxamide (ADB-FUBINACA) is an emerging synthetic cannabinoid whose toxicological and metabolic data are currently unavailable. We aimed to determine optimal markers for identifying ADB-FUBINACA intake. Metabolic stability was evaluated with human liver microsome incubations. Metabolites were identified after 1 and 3 h incubation with pooled human hepatocytes, liquid chromatography- high resolution mass spectrometry in positive-ion mode (5600+ TripleTOF®, Sciex) and several data mining approaches (MetabolitePilot™, Sciex). Metabolite separation was achieved on an Ultra Biphenyl column (Restek®); full-scan TOF-MS and information-dependent acquisition MS/MS data were acquired. ADB-FUBINACA microsomal half-life was 39.7 min, with a predicted hepatic clearance of 9.0 mL/min/kg and a 0.5 extraction ratio (intermediate-clearance drug). Twenty-three metabolites were identified. Major metabolic pathways were alkyl and indazole hydroxylation, terminal amide hydrolysis, subsequent glucuronide conjugations, and dehydrogenation. We recommend ADB-FUBINACA hydroxyalkyl, hydroxydehydroalkyl and hydroxylindazole metabolites as ADB-FUBINACA intake markers. N-dealkylated metabolites are not specific ADB-FUBINACA metabolites and should not be used as definitive markers of consumption. This is the first ADB-FUBINACA in vitro metabolism study; in vivo experiments enabling pharmacokinetic and pharmacodynamics studies or urine from authentic clinical/forensic cases are needed to confirm our results.

Inhibitors of 15-Prostaglandin Dehydrogenase To Potentiate Tissue Repair

The enzyme 15-prostaglandin dehydrogenase (15-PGDH) catalyzes the first step in the degradation of prostaglandins including PGE2. It is a negative regulator of tissue repair and regeneration in multiple organs. Accordingly, inhibitors of 15-PGDH are anticipated to elevate in vivo levels of PGE2 and to promote healing and tissue regeneration. The small molecule SW033291 (1) inhibits 15-PGDH with K_i = 0.1 nM in vitro, doubles PGE2 levels in vivo, and shows efficacy in mouse models of recovery from bone marrow transplantation, ulcerative colitis, and partial hepatectomy. Here we describe optimized variants of 1 with improved solubility, druglike properties, and in vivo activity.

In vitro and in vivo pharmacokinetics and metabolism of synthetic cannabinoids CUMYL-PICA and 5F-CUMYL-PICA

CUMYL-PICA [1-pentyl-N-(2-phenylpropan-2-yl)-1H-indole-3-carboxamide] and 5F-CUMYL-PICA [1-(5-fluoropentyl)-N-(2-phenylpropan-2-yl)-1H-indole-3-carboxamide] are recently identified recreationally used/abused synthetic cannabinoids, but have uncharacterized pharmacokinetic profiles and metabolic processes. This study characterized clearance and metabolism of these compounds by human and rat liver microsomes and hepatocytes, and then compared these parameters with in vivo rat plasma and urine sampling. It also evaluated hypothermia, a characteristic cannabimimetic effect. Incubation of CUMYL-PICA and 5F-CUMYL-PICA with rat and human liver microsomes suggested rapid metabolic clearance, but in vivo metabolism was prolonged, such that parent compounds remained detectable in rat plasma 24 h post-dosing. At 3 mg/kg (intraperitoneally), both compounds produced moderate hypothermic effects. Twenty-eight metabolites were tentatively identified for CUMYL-PICA and, coincidentally, 28 metabolites for 5F-CUMYL-PICA, primarily consisting of phase I oxidative transformations and phase II glucuronidation. The primary metabolic pathways for both compounds resulted in the formation of identical metabolites following terminal hydroxylation or dealkylation of the N-pentyl chain for CUMYL-PICA or of the 5-fluoropentyl chain for 5F-CUMYL-PICA. These data provide evidence that in vivo elimination of CUMYL-PICA, 5F-CUMYL-PICA and other synthetic cannabinoids is delayed compared to in vitro modeling, possibly due to sequestration into adipose tissue. Additionally, the present data underscore the need for careful selection of metabolites as analytical targets to distinguish between closely related synthetic cannabinoids in forensic settings.