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Metabolite identification plays a critical role in the phases during drug development. Drug metabolites can contribute to efficacy, toxicity, and drug-drug interaction. Thus, the correct identification of metabolites is essential to understand the behavior of drugs in humans. Drug administration authorities (e.g., FDA, EMA, and NMPA) emphasize evaluating the safety of human metabolites with exposure higher than 10% of the total drugrelated components. Many previous reviews have summarized the various methods, tools, and strategies for the appropriate and comprehensive identification of metabolites. In this review, we focus on summarizing the importance of identifying metabolites in the preclinical and clinical phases of drug development. Summarized scenarios include the role of metabolites in pharmacokinetics/pharmacodynamics (PK/PD) analysis, disproportional exposure of metabolites that contribute to drug toxicity, changes in metabolite exposure in renal-impaired patients, covalent tyrosine kinase inhibitors (anticancer drugs), and metabolite identification of drug candidates from natural medicines. This review is aimed to provide meaningful insight into the significant role of metabolite identification in drug development.

Forsythin extracted from Forsythiae Fructus is widely used to treat fever caused by the common cold or influenza in China, Japan and Korea. The present study aimed to analyze the pharmacokinetics, metabolism and excretion routes of forsythin in humans and determine the major enzymes and transporters involved in these processes. After a single oral administration, forsythin underwent extensive metabolism via hydrolysis and further sulfation. In total, 3 of the 13 metabolites were confirmed by comparison to reference substances, i.e., aglycone M1, M1 sulfate (M2), and M1 glucuronide (M7). Hydrolysis was the initial and main metabolic pathway of the parent compound, followed by extensive sulfation to form M2 and a reduced level of glucuronidation to form M7. In addition, the plasma exposure of M2 and M7 were 86- and 4.2-fold higher than that of forsythin. Within 48 h, ~75.1% of the administered dose was found in urine, with M2 accounting for 71.6%. Further phenotyping experiments revealed that sulfotransferase 1A1 and UDP-glucuronosyltransferase 1A8 were the most active hepatic enzymes involved in the formation of M2 and M7, respectively. The in vitro kinetic study provided direct evidence that M1 showed a preference for sulfation. Sulfated conjugate M2 was identified as a specific substrate of organic anion transporter 3, which could facilitate the renal excretion of M2. Altogether, our study demonstrated that sulfation dominated the metabolism and pharmacokinetics of forsythin, while the sulfate conjugate was excreted mainly in the urine.

Objective: To assess the immune effect of different types of hepatitis B vaccine (HepB) booster doses 2–32 years after primary immunization, explore the influencing factors, and offer guidance regarding the necessity and timing of boosters. Methods: In total, 1163 participants who were born from 1986 to 2015, received the HepB full-course primary vaccination, were hepatitis B surface antigen (HBsAg) and hepatitis B core antibody (anti-HBc) negative, and had hepatitis B surface antibody (anti-HBs)

Previous work has confirmed that the chronic hypoxia-hypercapnia (CHH) associated with chronic obstructive pulmonary disease contributes to the development of skeletal muscle atrophy. Neuromuscular Electrical Stimulation (NMES) has shown some efficacy when used as a treatment to reduce skeletal muscle atrophy. The present study focuses on the MicroRNA-486/PTEN/FoxO1 pathway with the goal of identifying its physiological role in skeletal muscle atrophy induced by CHH as well as its role during NMES treatment. To test this, 32 male Sprague Dawley rats were randomly divided into four groups. After completion of the disease modeling, gastrocnemius muscles were collected from all animals and cross-sectional areas of muscular fiber were observed and analyzed via H&E staining. MiR-486 expression was further assessed by qRT-PCR, and protein levels of TNF-α, PTEN, p-Akt, Akt, FoxO1, atrogin-1 and MuRF1 were measured by immunohistochemistry and western blotting. CSA, miR-486, and the ratio p-Akt/Akt were significantly reduced in the CHH group, while the levels of TNF-α, PTEN, FoxO1, atrogin-1, and MuRF1 were markedly increased. Importantly, these findings were reversed as a result of NMES. Thus, the MicroRNA-486/PTEN/FoxO1 pathway functions in muscle protein synthesis and degradation. NEW & NOTEWORTHY: Our research provides a theoretical basis for the application of NMES as a means of improving muscle atrophy. Moreover, these therapeutic targets provide possible clues relevant to the treatment of amyotrophic diseases.

Forsythiae suspensa is widely used in China as a traditional Chinese medicine. Forsythin is extracted from Forsythiae Fructus and has undergone phase II clinical trials as an antipyretic drug in China. The main metabolites of forsythin in human plasma are aglycone sulfate (KD-2-SO3H) and aglycone glucuronide (KD-2-Glc). In the present study, a sensitive and rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and fully validated for the simultaneous analysis of forsythin, KD-2-Glc, and KD-2-SO3H, in human plasma. After precipitating proteins with methanol, these three analytes were separated on a Gemini-C18 column along with teniposide as an internal standard. Mass spectrometry detection, under multiple reaction monitoring, was then carried out in negative mode using the Triple Quad™ 6500+ LC-MS/MS system coupled with an electrospray ionization (ESI) ion source. The transitions of m/z 371.1→356.1 for forsythin, m/z 547.2→356.0 for KD-2-Glc and m/z 451.2→356.2 for KD-2-SO3H were chosen to effectively maintain the balance between selectivity and sensitivity. The developed method was linear over the following concentrations in human plasma samples: 1.00-1000 ng/mL for forsythin, 2.50-2500 ng/mL for KD-2-Glc, and 5.00-5000 ng/mL for KD-2-SO3H. Assays were validated and satisfied the acceptance criteria recommended by the CFDA guidance. Furthermore, this LC-MS/MS method was successfully implemented in a Phase I, first-in-human, dose-escalation pharmacokinetic study among Chinese healthy participants after single oral administration of forsythin tablets.

TPN171 is a novel potent pyrimidinone phosphodiesterase type 5 (PDE5) inhibitor with high selectivity and long duration of action. It has been used to treat patients suffering from pulmonary arterial hypertension and entered phase I clinical trials in 2016. Considering the potential therapeutic value of TPN171, its metabolism in humans is necessary to be elucidated during early-stage of drug development. This study aimed to establish a rapid and reliable method based on ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry for the characterization of TPN171 metabolites in human plasma, urine and stool samples. A total of 17 metabolites, including 14 from phase I and 3 from phase II metabolic reactions, were identified and characterized. TPN171 was found to be the predominant component in all plasma, urine and stool samples. Seven proposed metabolites were validated by comparing with synthetic reference standards. N-demethylation, O-depropylation, N-oxidation and dehydrogenation were demonstrated to be the main metabolic pathways of TPN171 in humans, yielding metabolites M4, M3, M7-2 and M5-3, respectively. Notably, M5-3 (a dehydrogenation product) and M3 (an O-depropylation product) were the main metabolites in human plasma while M5-3 (produced via dehydrogenation) and M7-2 (produced via N-oxidation) were the major metabolites in human urine. Besides, O-depropylation product M3 and N-demethylation product M4 were the main metabolites in human stool. In overall, this study assessed the metabolic fate of TPN171 in humans, which may yield considerably benefits for subsequent studies focusing on TPN171 metabolism and development of other PDE5 inhibitors.

The Cr-/Si-modified NiAlHf coatings were produced on single-crystal (SC) superalloy N5 by electron beam physical vapor deposition (EB-PVD). The cyclic oxidation behavior of the coatings at 1100 °C was investigated. The microstructures of the oxide scales grown on the coatings were characterized by scanning electron microscope (SEM) with energy-dispersive X-ray spectrum (EDX), electron probe micro-analyzer (EPMA) and X-ray diffraction (XRD). The effects of Cr and Si on the cyclic oxidation behavior of the NiAlHf coatings were discussed. The addition of Si to the NiAlHfCr coating not only reduces the oxidation rate but also enhances the oxide scale adherence. Owing to the addition of Si in the coating, the segregation of Cr and Mo beneath the oxide scale is effectively avoided, which contributes to enhancing oxide scale adherence.

The aim of the present study was to determine the effects of emodin, a natural compound with antioxidant properties, on oxidative stress and apoptosis induced by hypoxia/reoxygenation (H/R) in HK-2 human renal tubular cells. In HK-2 cells subjected to H/R, it was observed that pre-treatment with emodin lead to an increase in cellular viability and a reduction in the rate of apoptosis and the B-cell lymphoma 2 (Bcl-2)-associated X protein/Bcl-2 ratio. H/R alone caused a significant increase in the levels of reactive oxygen species and malondialdehyde (P

Skeletal muscle dysfunction in chronic obstructive pulmonary disease (COPD) patients is common. Neuromuscular Electrical Stimulation (NMES) is a powerful exercise training that may relieve muscle dysfunction in COPD. This study investigated whether electrical stimulation may have atypical adaptations via activation of miRNA related pathways in counteracting COPD muscle dysfunction. Forty-eight male Sprague-Dawley rats were randomly assigned to 3 groups. With the exception of the rats in the control group, the experimental rats were exposed to chronic intermittent hypoxia-hypercapnia (CIHH) (9∼11%O2,5.5∼6.5%CO2) for 2 or 4 weeks. Electrical stimulation was performed immediately after each CIHH session. Following assessment of the running capacity, biopsy samples were obtained from the gastrocnemius of the rats. The miR-1, miR-133a and miR-133b levels were measured, as well as their related proteins: phosphorylation of Akt (p-AKT), PGC-1alpha (PGC-1α), histone deacetylase 4 (HDAC4) and serum response factor (SRF). Myosin heavy chainIIa (MHCIIa) and myosin heavy chainIIb (MHCIIb) were also measured to assess fiber type changes. After 2 weeks, compared with the controls, only miR-1 and miR-133a were significantly increased (p