HPLC–MS/MS analysis of mesupron and its application to a pharmacokinetic study in rats

In vitro interaction of potential antiviral TMPRSS2 inhibitors with human serum albumin and cytochrome P 450 isoenzymes

The interactions of four sulfonylated Phe(3-Am)-derived inhibitors (MI-432, MI-463, MI-482 and MI-1900) of type II transmembrane serine proteases (TTSP) such as transmembrane protease serine 2 (TMPRSS2) were examined with serum albumin and cytochrome P450 (CYP) isoenzymes. Complex formation with albumin was investigated using fluorescence spectroscopy. Furthermore, microsomal hepatic CYP1A2, 2C9, 2C19 and 3A4 activities in presence of these inhibitors were determined using fluorometric assays. The inhibitory effects of these compounds on human recombinant CYP3A4 enzyme were also examined. In addition, microsomal stability assays (60-min long) were performed using an UPLC-MS/MS method to determine depletion percentage values of each compound. The inhibitors showed no or only weak interactions with albumin, and did not inhibit CYP1A2, 2C9 and 2C19. However, the compounds tested proved to be potent inhibitors of CYP3A4 in both assays performed. Within one hour, 20%, 12%, 14% and 25% of inhibitors MI-432, MI-463, MI-482 and MI-1900, respectively, were degraded. As essential host cell factor for the replication of the pandemic SARS-CoV-2, the TTSP TMPRSS2 emerged as an important target in drug design. Our study provides further preclinical data on the characterization of this type of inhibitors for numerous trypsin-like serine proteases.

Therapeutic Strategies Targeting Urokinase and Its Receptor in Cancer

Several studies have ascertained that uPA and uPAR do participate in tumor progression and metastasis and are involved in cell adhesion, migration, invasion and survival, as well as angiogenesis. Increased levels of uPA and uPAR in tumor tissues, stroma and biological fluids correlate with adverse clinic-pathologic features and poor patient outcomes. After binding to uPAR, uPA activates plasminogen to plasmin, a broad-spectrum matrix- and fibrin-degrading enzyme able to facilitate tumor cell invasion and dissemination to distant sites. Moreover, uPAR activated by uPA regulates most cancer cell activities by interacting with a broad range of cell membrane receptors. These findings make uPA and uPAR not only promising diagnostic and prognostic markers but also attractive targets for developing anticancer therapies. In this review, we debate the uPA/uPAR structure-function relationship as well as give an update on the molecules that interfere with or inhibit uPA/uPAR functions. Additionally, the possible clinical development of these compounds is discussed.

Absolute oral and subcutaneous bioavailability of ortho-topolin riboside in mice

Among essential phytohormones playing a pivotal role in regulating growth and development, ortho-topolin riboside (oTR) exerts the most substantial anti-tumor potency in various cancer cell lines. This study was designed to establish a quantitative determination method for oTR in mouse plasma using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS), to validate the analytical method including stability, and to characterise its pharmacokinetic behaviour in mice. After simple protein precipitation with acetonitrile including kinetin riboside (internal standard), oTR was eluted on a reversed-phase column using a mobile phase of water and acetonitrile (3:7 v/v, including 0.1% formic acid). The protonated precursor ion [M+H]⁺ and major fragment ion were confirmed at m/z 374.06 and 241.99 for oTR, and 348.23 and 216.06 for the IS, respectively. oTR was stable under bench and storage conditions. The analytical method met the criteria of FDA-validated bioanalytical methods and was successfully applied to a pharmacokinetic study for the first time following oral, subcutaneous, and intravenous administrations. While oTR was merely absorbed by an oral route, 90% of the absolute subcutaneous bioavailability was observed.

A sensitive analytical method for the determination of SG-SP1 in rat plasma by HPLC-MS/MS and its application to a pharmacokinetic study

SG-SP1, a newly synthesised gallic acid derivative, blocks histamine release by reducing calcium influx in mast cells and inhibits inflammatory cytokine expression. This derivative has promising anti-allergic potential. Our research was designed to establish a quantitative determination method for SG-SP1 in rat plasma using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS), to validate the analytical method including stability and to characterise its pharmacokinetic behaviour in rats. After simple protein precipitation with acetonitrile including an internal standard, SG-SP1 was eluted on a reversed-phase column using a mobile phase of water and acetonitrile (2:8 v/v, including 0.1 % formic acid). The protonated precursor ion [M+H]⁺ and major fragment ion were confirmed at m/z 588.2 and 180.1, respectively. The substance was stable under bench and storage conditions. The analytical method met the criteria of FDA-validated bioanalytical methods and was successfully applied to a pharmacokinetic study for the first time. SG-SP1 decayed in a biphasic pattern with terminal half-life of 5.1 h and clearance of about 3.2 L/h/kg. Double peaks were observed following oral administration, and the absolute oral bioavailability was ∼1 %.

A new sensitive UPLC-MS/MS method for the determination of cucurbitacin B in rat plasma: application to an absolute bioavailability study

Cucurbitacin B (CuB) is a highly oxygenated tetracyclic triterpene, and a Biopharmaceutics Classification System (BCS) class IV drug used for the treatment of persistent hepatitis, chronic hepatitis, and primary liver cancer. Nevertheless, CuB has low solubility and low permeability, and is present at low concentrations in the human body. The aim of this study was to develop a method for the determination of CuB in plasma using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) with estrone as an internal standard (IS), as well as to examine the pharmacokinetics and absolute bioavailability of CuB in rats. Plasma samples were processed by liquid–liquid extraction with ethyl acetate. Separation was achieved on a BEH C18 column (2.1 × 50 mm, 1.7 μm) at 35 °C using an isocratic mobile phase system with 0.1% formic acid–acetonitrile (50 : 50, v/v) at a flow rate of 0.3 mL min⁻¹. The detection was performed using a multiple reaction monitoring mode via a positive electrospray ionization interface. The calibration curves showed good linearity (r = 0.9998) within the tested concentration ranges. The lower limit of quantification for plasma was 0.05 ng mL⁻¹; the matrix effect of CuB and IS was 94.19–99.42% and 100.83%, respectively. The mean extraction recoveries from plasma were 85.34–90.53%. The intra-day and inter-day accuracies and precision deviations were within ±15%, which was in line with the allowable range of accuracy. In addition, the stability of the method was also verified. The absolute bioavailability of orally administered CuB in rats was 1.37%. To sum up, the presented method was determined to be suitable for the quantitation of CuB in rat plasma. Also, the absolute bioavailability observed in the present study suggested that it was necessary to change the dosage form to improve bioavailability, or to improve this by other means.

A method was developed for the determination of CuB in plasma using UPLC-MS/MS with estrone as an internal standard, and the pharmacokinetics and absolute bioavailability of CuB in rats were examined.