Development of fluorine-substituted NH2-biphenyl-diarylpyrimidines as highly potent non-nucleoside reverse transcriptase inhibitors: Boosting the safety and metabolic stability

Our recent studies for nonnucleoside reverse transcriptase inhibitors identified a highly potent compound JK-4b against WT HIV-1 (EC50 = 1.0 nmol/L), but the poor metabolic stability in human liver microsomes (t 1/2 = 14.6 min) and insufficient selectivity (SI = 2059) with high cytotoxicity (CC50 = 2.08 μmol/L) remained major issues associated with JK-4b. The present efforts were devoted to the introduction of fluorine into the biphenyl ring of JK-4b, leading to the discovery of a novel series of fluorine-substituted NH2-biphenyl-diarylpyrimidines with noticeable inhibitory activity toward WT HIV-1 strain (EC50 = 1.8-349 nmol/L). The best compound 5t in this collection (EC50 = 1.8 nmol/L, CC50 = 117 μmol/L) was 32-fold in selectivity (SI = 66,443) compared to JK-4b and showed remarkable potency toward clinically multiple mutant strains, such as L100I, K103N, E138K, and Y181C. The metabolic stability of 5t was also significantly improved (t 1/2 = 74.52 min), approximately 5-fold higher than JK-4b in human liver microsomes (t 1/2 = 14.6 min). Also, 5t possessed good stability in both human and monkey plasma. No significant in vitro inhibition effect toward CYP enzyme and hERG was observed. The single-dose acute toxicity test did not induce mice death or obvious pathological damage. These findings pave the way for further development of 5t as a drug candidate.

Picomolar inhibitor of reverse transcriptase featuring significantly improved metabolic stability

Considering the undesirable metabolic stability of our recently identified NNRTI 5 (t1/2 = 96 min) in human liver microsomes, we directed our efforts to improve its metabolic stability by introducing a new favorable hydroxymethyl side chain to the C-5 position of pyrimidine. This strategy provided a series of novel methylol-biphenyl-diarylpyrimidines with excellent anti-HIV-1 activity. The best compound 9g was endowed with remarkably improved metabolic stability in human liver microsomes (t1/2 = 2754 min), which was about 29-fold longer than that of 5 (t1/2 = 96 min). This compound conferred picomolar inhibition of WT HIV-1 (EC50 = 0.9 nmol/L) and low nanomolar activity against five clinically drug-resistant mutant strains. It maintained particularly low cytotoxicity (CC50 = 264 μmol/L) and good selectivity (SI = 256,438). Molecular docking studies revealed that compound 9g exhibited a more stable conformation than 5 due to the newly constructed hydrogen bond of the hydroxymethyl group with E138. Also, compound 9g was characterized by good safety profiles. It displayed no apparent inhibition of CYP enzymes and hERG. The acute toxicity assay did not cause death and pathological damage in mice at a single dose of 2 g/kg. These findings paved the way for the discovery and development of new-generation anti-HIV-1 drugs.

Evaluation of the metabolism of PEP06,an endostatin-RGDRGD 30-amino-acid polypeptide and a promising novel drug for targeting tumor cells / 药物分析学报

PEP06 is a novel endostatin-Arg-Gly-Asp-Arg-Gly-Asp(RGDRGD)30-amino-acid polypeptide featuring a terminally fused RGDRGD hexapeptide at the N terminus.The active endostatin fragment of PEPO6 directly targets tumor cells and exerts an antitumoral effect.However,little is known about the kinetics and degradation products of PEP06 in vitro or in vivo.In this study,we investigated the in vitro metabolic stability of PEP06 after it was incubated with living cells obtained from animals of different species;we further identified the degradation characteristics of its cleavage products.PEP06 underwent rapid enzymatic degradation in multiple types of living cells,and the liver,kidney,and blood play important roles in the metabolism and clearance of the peptides resulting from the molecular degradation of PEP06.We identified metabolites of PEP06 using full-scan mass spectrometry(MS)and tandem MS(MS2),wherein 43 metabolites were characterized and identified as the degradation metabolites from the parent peptide,formed by successive losses of amino acids.The metabolites were C and N terminal truncated products of PEP06.The structures of 11 metabolites(M6,M7,M16,M17,M21,M25,M33,M34,M39,M40,and M42)were further confirmed by comparing the retention times of similar full MS spectrum and MS2 spectrum information with reference standards for the synthesized metabolites.We have demonstrated the metabolic stability of PEP06 in vitro and identified a series of potentially bioactive downstream metabolites of PEP06,which can support further drug research.

Discovery of highly selective and orally available benzimidazole-based phosphodiesterase 10 inhibitors with improved solubility and pharmacokinetic properties for treatment of pulmonary arterial hypertension

Optimization efforts were devoted to discover novel PDE10A inhibitors in order to improve solubility and pharmacokinetics properties for a long-term therapy against pulmonary arterial hypertension (PAH) starting from the previously synthesized inhibitor

Advances in methodologies for predicting metabolic stability for low-clearance drugs / 中国药科大学学报

@#The metabolic stability test of drugs is a key step in drug discovery and achieving low clearance is frequently the goal in the design of drug. Increased drug metabolism stability can reduce drug dosage, enhance drug exposure and prolong drug half-life. Accurately assessing the metabolic stability parameters of low clearance drugs and predicting human pharmacokinetics has become a challenge. Traditional tools in vitro including microsomes and suspended primary hepatocytes are limited by incubation time, which is not long enough to make sufficient metabolic conversion. Determination of intrinsic clearance or metabolic pathways and mechanisms of drug are implicated. Novel models tend to further mimic the in vivo environment in order to prolong lifetime of hepatocytes and achieve sufficient metabolic turnover of drugs for monitoring. In vitro-in vivo correlation of intrinsic clearance of methodologies has evaluated to support the reliability in predicting human pharmacokinetics. Application of these methodologies greatly decreases the forthputting of experimental animals and the release of expensive clinical trials during the acquisition of pharmacokinetic parameters. In this review, we summarized the principles, advantages and disadvantages of the novel in vitro methodologies for metabolic stability dealing with low-turnover drugs, including hepatocyte relay method, plated human hepatocytes, coculture system and microfluidic devices. Future prospect is proposed for in vitro metabolic models and it provides reference and optimization in metabolic stability for early lead compounds.

Gender differences in cytochrome P450 enzyme and UDP-glucuronosyltransferase mediated metabolic stabilities of bakuchiol in rat and human liver microsomes / 中国药理学与毒理学杂志

OBJECTIVE: To investigate the metabolic characteristics of bakuchiol mediated by cytochrome P450 enzyme (CYP) and UDP-glucuronosyltransferase (UGT) in rat liver microsomes (RLMs) or human liver microsomes (HLMs), and to compare the metabolic gender differences. METHODS: Bakuchiol was incubated at 37? with male and female RLMs or HLMs in the presence of nicotinamide adenine dinucleotide phosphate (NADPH) or uridine 5′-diphosphoglucuronic acid (UDPGA). The residual concentrations of bakuchiol were measured in each incubation system using high performance liquid chromatography (HPLC). The metabolic stability and metabolic gender differences of bakuchiol were evaluated by the remaining percentage of bakuchiol after incubation.RESULTS: When bakuchiol was metabolized by CYP in RLMs, the intrinsic clearance (Clint) value in male RLMs ?(326.6±15.4) mL·min-1·kg-1?was significantly higher than that of female RLMs ?(77.2±4.8) mL·min-1·kg-1? (P<0.01). When bakuchiol was metabolized by UGT in RLMs, female RLMs had a significantly higher Clint value ?(419.1±24.1) mL·min-1·kg-1? than male RLMs ?(164.5±8.4) mL·min-1·kg-1? (P<0.01). When bakuchiol was metabolized by both CYP and UGT in RLMs, male RLMs had a significantly higher Clint value ?(1063.1±27.2) mL·min-1·kg-1? than female RLMs ?(781.2±16.5) mL·min-1·kg-1?(P<0.01). When bakuchiol was metabolized by CYP in HLMs, male HLMs had a significantly higher Clint value ?(24.8±2.1) mL·min-1·kg-1? than female HLMs ?(17.6±1.0) mL·min-1·kg-1? (P<0.01). There were no significant gender differences in the metabolism of bakuchiol when it was metabolized by UGT in HLMs. The Clint values were 176.4±26.5 and (165.9±8.6) mL·min-1·kg-1, respectively. The metabolic parameters of bakuchiol mediated by CYP and UGT in HLMs had no significant gender differences. The Clint values were 262.5±20.9 and (236.2±10.5) mL·min-1·kg-1, respectively. CONCLUSION Bakuchiol can be metabolized by CYP and UGT in RLMs or HLMs, and the metabolic parameters exhibit species differences and gender differences.

Study on the Metabolic Characteristics of Piperitylmagnolol in Different Species of Liver Microsomes by UPLC-MS/MS / 中国药房

OBJECTIVE： To establish a method for the determination of piperitylmagnolol in the incubation system of liver microsomes， and to investigate the metabolic characteristics of it in different species of liver microsomes. METHODS： The piperitylmagnolol were respectively dissolved in NADPH activated liver microsome incubation systems of human， rat， mouse， monkey and dog， and then incubated in water at 37 ℃. The reaction was terminated with methanol at 0， 2， 5， 10， 15， 20， 30， 45 and 60 minutes of incubation， respectively. Using magnolol as internal standard， UPLC-MS/MS method was used to determine the concentration of piperitylmagnolol in the incubation system. The determination was performed on Acquity UPLCTM CSH C18 column with mobile phase consisted of 0.1％ formic acid-methanol （gradient elution） at the flow rate of 0.3 mL/min. The column temperature was set at 30 ℃， and the sample size was 2 μL. The ion source was electrospray ion source， and the positive ion scanning was carried out in the multiple reaction monitoring mode. The ion pairs used for quantitative analysis were m/z 401.2→331.1 （piperitylmagnolol） and m/z 265.1→247.0 （internal standard）， respectively. Using the concentration of piperitylmagnolol at 0 min of incubation as a reference， the residual percentage， metabolism half-life in vitro （t1/2） and intrinsic clearance （CLint） were calculated for different incubation systems. The metabolic pathway of piperitylmagnolol was studied by chemical inhibitor method. Under the above chromatographic conditions， the metabolites in vitro were preliminarily analyzed by first-order full scanning and positive ion detection. RESULTS： The linear range of piperitylmagnolol was 3.91-500.00 ng/mL. The limit of quantitation was 3.91 ng/mL. RSDs of intra-day and inter-day were less than 10％. The accuracy ranged 87.40％-103.75％. Matrix effect didn’t affect the determination of the substance to be measured. The piperitylmagnolol was metabolized significantly in human， rat， mouse and dog liver microsomes， but not in monkey liver microsomes. After incubating for 30 min， residual percentage of piperitylmagnolol kept stable in different species of liver microsomes. The t1/2 of piperitylmagnolol were 12.07， 17.68， 17.59， 216.56 and 61.88 min in human， rat， mouse， monkey and dog liver microsomes； CLint were 0.115， 0.078， 0.079， 0.006， 0.022 mL/（min·mg）， respectively. Inhibitory rates of CYP2A6， CYP2D6， CYP2C19， CYP3A4， CYP2C9， CYP2E1 and CYP1A2 to compound metabolism were 55.76％， 93.94％， 96.01％， 93.69％， 71.81％， 23.25％， 28.04％， respectively. Quasi-molecular ion peaks of the two main metabolites of piperitylmagnolol in human liver microsomes were m/z 441.2（[M+Na]+） and m/z 337.2（[M+H]+）， respectively. CONCLUSIONS： Established UPLC-MS/MS method is simple， rapid and specific， and can be used for the determination of piperitylmagnolol concentration in the incubation system of liver microsomes and pharmacokinetic study. The metabolic characteristics of the compound are different among liver microsomes of human， rat， mouse， monkey and dog. Its metabolism process may be associated with CYP2D6， CYP2C19， CYP3A4， CYP2C9， etc.

Investigation of metabolism of HN-1 isolated from Millettia pachyloba in vivo and in vitro / 中国中药杂志

Ultra-fast performance liquid chromatography-mass spectrometry( UFLC-MS/MS) was used to study the anti-inflammatory active ingredient of Millettia pachyloba,6-methoxy-8,8-dimethyl-3-( 2,4,5-trimethoxyphenyl)-4 H,8 H-pyrano[2,3-f]chromen-4-one( HN-1),in liver microsomes of rats,mice,rhesus monkeys,Beagle dogs and humans metabolic stability,and compare the metabolic differences between different species. The metabolic phenotype in human liver microsomes was determined by chemical inhibitor method. Using UPLC-Q-TOF-MS/MS detection method,the in vitro metabolites of various liver microsomes were preliminarily inferred by comparing the samples incubated for 0 min and 60 min in vitro. The metabolites of HN-1 in SD rats were presumed by comparing feces,urine,plasma blanks and samples after administration. The results showed that the metabolism of HN-1 in various liver microsomes was stable,and the metabolic properties of dog and human liver microsomes were the closest. It is mainly catabolized by CYP1 A1,CYP2 D6 and CYP3 A4 isoenzymes in human liver microsomes. The metabolites of HN-1 in vitro and in vivo,including 3 in vitro metabolites and5 in vivo metabolites,were preliminarily estimated. The results laid the foundation for further pharmacological studies of HN-1.

In Vitro Metabolism of Two Novel Tacrine Derivates ST09 and ST10 / 中国药学杂志

OBJECTIVE: To determin the in vitro metabolic stability of ST09 and ST10 in human liver microsomes (HLMs), and to evaluate their potential inhibitions on five HLM cytochrome P450 isoforms. METHODS: A liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to assess remaining concentration of ST09 and ST10 at designed time points during the HLM incubation. Six major metabolites of cytochrome P450 were simultaneously measured with LC-MS/MS, and the inhibitory effects of ST09 and ST10 were respectively evaluated with IC50 values. RESULTS: ST09 was extremely unstable in vitro, and t1/2 was less than 1 min. However, ST10, the major metabolite of ST09, was NADPH-independent metabolized in HLMs, while its t1/2 and microsomal intrinsic clearance (CLint) were 32 min and 0.043 mL·min-1·mg(protein)-1, respectively. IC50 values of ST09 and ST10 on CYP3A4 (midazolam as substrate), CYP3A4 (testosterone as substrate), CYP1A2, CYP2C9, CYP2C19 and CYP2D6 were 0.42/0.25, 1.27/0.81, 24.92/18.21, 36.53/54.34, 67.64/144.90, 6.43/5.30 μmol·L-1, respectively. CONCLUSION: ST09 and ST10 are extensively metabolized in vitro and both compounds had significant inhibition on CYP3A4 and CYP2D6.

In vitro metabolism of liquiritigenin in liver microsomes of different species / 中草药

Objective: To compare in vitro metabolic differences of liquiritigenin, an aglycone of liquiritin, among liver microsomes of different species, which would provide reference for further research and development of liquiritin. Methods: Metabolic stability and metabolic biotransformation were investigated after liquiritigenin was incubated with rat, mouse, human, dog, and monkey liver microsomes. Metabolic stability was evaluated using a substrate depletion approach, and the results were reported as "% liquiritigenin remaining", which was then used to calculate the in vitro half-life (t1/2). Metabolic biotransformation was characterized by metabolite profiling. Results: In liver microsomal incubation systems of five species, the t1/2 values of liquiritigenin for phase I were as follows: rat < mouse < human < monkey < dog, whereas for phase II, the metabolic rates were all fast and the remaining of liquiritigenin were all below 50% in 5 min except mouse. In addition, phase II metabolite profiling in monkey liver microsomes was identical to that of human, but marked differences were found between other species and human. Conclusion: The metabolic characteristics of liquiritigenin in monkey liver microsomes is most similar to that of human, then followed by dog, and marked differences existed between rat, mouse and human. Therefore, monkey or dog could be the animal model for further preclinical pharmacokinetic and toxicological studies.

Pharmacokinetic characteristics of YZG-331, a promising sedative-hypnotic candidate agent / 药学学报

The purpose of this article was to study the pharmacokinetic characteristics of YZG-331, plasma protein binding and metabolic stability in vivo and in vitro. Plasma and tissue concentrations of YZG-331 were determined in mice and rats after administration by LC-MS/MS analysis orally or intravenously. The plasma protein binding of YZG-331 with human, dog, monkey, rat and mouse were measured by ultrafiltration method. The stability of YZG-331 in animal and human plasma, liver microsomes, intestinal bacteria and artificial gastrointestinal fluid was also investigated in vitro. The results show that YZG-331 was absorbed rapidly in both mice and rats after oral administration, while the absorption and elimination saturation YZG-331 were also observed. The bioavailability of YZG-331 was much higher in male mice (51.2%) than that in female mice (27.7%), however, the bioavailability in male rats (27.1%) was lower than that in female rats (78.7%). YZG-331 was widely distributed in different tissues of mice, especially in certain regains of brain, including thalamus, hippocampi, cortical and striatal. YZG-331 was found to bind to human, dog, monkey, rat and mouse plasma protein in vitro (93.3%-98.9%) without significant concentration dependences and species differences. YZG-331 was stable in animal and human plasma, simulated gastric/intestinal fluid and liver microsomal incubations, except rat liver microsomes and intestinal flora. Therefore, we concluded that:the pharmacokinetics of YZG-331 in mice and rats have gender and species differences; YZG-331 was widely distributed in vivo including brain, the targets of the agent; YZG-331 had a high affinity to plasma protein and was metabolized by rat liver microsomes and intestinal flora.

In vitro metabolism of anti-tumor compound E7 in different species of liver microsomes / 中国中药杂志

To investigate the metabolic stability of E7 in liver microsomes of human, Beagle dog, Cynomolgus monkey and SD rats, and compare the metabolic differences between different species. Selective chemical inhibitors were used to determine the effects of different inhibitors on E7 metabolic rate, and predict the main enzymes involved in E7 metabolism in rat liver microsomes. The experimental results showed that the in vitro half-lives (T1/2) of E7 in liver microsomes of human, dog, monkey and rats were 57.75, 69.30, 16.90,30.13 min respectively. Their intrinsic clearance rate was 0.004 8, 0.004 0, 0.016 4 and 0.009 2 mL•min⁻¹•mg⁻¹ respectively. Hence, it could be speculated that the metabolic rate of E7 was similarly slow in human and dog liver microsomes; while it was similarly fast in monkey and rat liver microsomes. There was significant difference in metabolic rate of E7 between different species. The results showed that CYP2E1, CYP2A6, CYP1A2 and CYP2D6 might participate in metabolism of E7, while the contribution of polymorphic CYP3A4 was small.

Metabolic stability and metabolic enzyme phaenotypes of lanceolatin B in liver microsomes of different species by UPLC-MS/MS / 中国中药杂志

To investigate the metabolic stability and parameters in vitro of lanceolatin B in liver microsomes of rats, human, Beagle dogs, and monkeys, and to identify the phaenotypes of CYP enzymes of lanceolatin B by using the liver microsome incubation system in vitro. After incubated with different species of liver microsomes, lanceolatin B was quantified by UPLC-MS/MS method to evaluate its metabolic stability and metabolic kinetic parameters in vitro. Lanceolatin B was incubated with specific inhibitors of CYP450 isoforms (CYP2E1, 2C19, 1A2, 2D6, 2C9, 3A4, and 2A1) to determine the phaenotypes of metabolic enzymes. The results showed that lanceolatin B was metabolized in the liver microsomes of rats and monkeys but not in the human and Beagle dogs. Their in vitro half-life T1/2 and intrinsic clearance rate CLint in rat and monkey liver microsomes were 11.57,8.07 min, and 0.12,0.17 mL•min⁻¹•mg⁻¹ without significant difference. The results of metabolic phenotyping indicated that CYP1A2 was mainly involved in the metabolism of lanceolatin B. There existed a difference in the metabolism of lanceolatin B in different types of liver microsomes. Several of CYP450 isoforms metabolized lanceolatin B together in liver microsomes of rats, in which CYP1A2 was the major enzyme mainly responsible for the metabolism of lanceolatin B.

Determination of aconitine in dog tissue homogenates by HPLC-MS/MS and its application to in vitro metabolic stability study / 国际药学研究杂志

Objective To develop a HPLC-MS/MS method for the determination of aconitine and study thein vitro metabolic stability of aconitine in dog tissue homogenates.Methods The chromatographic separation was performed on a C18 column.The mobile phase consisted of acetonitrile and water with 0.2％ formic acid and 5 mmol/L ammonium acetate.A triple quadrupole tandem mass spectrometer equipped with an electrospray ionization interface source was used for the quantitative determination in the positive selective reaction monitor mode.Aconitine was incubated with dog tissue homogenates and samples were withdrawn at different time points and precipitated by acetonitrile with internal standards citalopram.Results Aconitine showed good linear relationship over the range from 5 to 500 ng/ml.The recoveries of aconitine were between 85.73％ and 92.12％ at three QC concentration levels.The intra- and inter-day precisions were 5.32％ - 8.95％ and 5.45％ - 8.86％,respectively.After incubation,about 20％ of aconitine were cleared in the liver and small intestine,and t1/2 were 460.6 and 521.3 min,respectively.But none was metabolized in the stomach and kidney.Conclusion These results demonstrated that aconitine was mainly metabolized in the liver and small intestine at a slow rate.