Assessments of CYP­inhibition­based drug-drug interaction between vonoprazan and poziotinib in vitro and in vivo.

CONTEXT: Poziotinib and vonoprazan are two drugs mainly metabolized by CYP3A4. However, the drug-drug interaction between them is unknown. OBJECTIVE: To study the interaction mechanism and pharmacokinetics of poziotinib on vonoprazan. MATERIALS AND METHODS: In vitro experiments were performed with rat liver microsomes (RLMs) and the contents of vonoprazan and its metabolite were then determined with UPLC-MS/MS after incubation of RLMs with vonoprazan and gradient concentrations of poziotinib. For the in vivo experiment, rats in the poziotinib treated group were given 5 mg/kg poziotinib by gavage once daily for 7 days, and the control group was only given 0.5% CMC-Na. On Day 8, tail venous blood was collected at different time points after the gavage administration of 10 mg/kg vonoprazan, and used for the quantification of vonoprazan and its metabolite. DAS and SPSS software were used for the pharmacokinetic and statistical analyses. RESULTS: In vitro experimental data indicated that poziotinib inhibited the metabolism of vonoprazan (IC50 = 10.6 µM) in a mixed model of noncompetitive and uncompetitive inhibition. The inhibitory constant Ki was 0.574 µM and the binding constant αKi was 2.77 µM. In vivo experiments revealed that the AUC(0-T) (15.05 vs. 90.95 µg/mL·h) and AUC(0-∞) (15.05 vs. 91.99 µg/mL·h) of vonoprazan increased significantly with poziotinib pretreatment. The MRT(0-∞) of vonoprazan increased from 2.29 to 5.51 h, while the CLz/F value decreased from 162.67 to 25.84 L/kg·h after pretreatment with poziotinib. CONCLUSIONS: Poziotinib could significantly inhibit the metabolism of vonoprazan and more care may be taken when co-administered in the clinic.

Novel inhibitor of hematopoietic cell kinase as a potential therapeutic agent for acute myeloid leukemia.

Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) are characterized by risk of relapses, poor survival, unwanted side effects and high toxicity with the current therapies. In light of these facts, there are efforts to develop new drugs specific for deregulated molecules that participate in leukemia pathogenesis. Hematopoietic cell kinase (HCK), an Src kinase family member, is overexpressed on hematopoietic stem cells of MDS and de novo AML patients and involved in the oncogenic process. Thus, we investigated in vitro, ex vivo and in vivo effects of a novel chemical compound targeting HCK inhibition (iHCK-37), in combination with the most used drugs for the treatment of MDS and de novo AML, 5-Azacytidine and Cytarabine. Herein, the combination treatment with iHCK-37 and 5-Azacytidine or Cytarabine demonstrated additive effects against leukemia cells, compared to either drug alone. iHCK-37 plus 5-Azacytidine or Cytarabine treatment was able to reduce the activation of oncogenic pathways, MAPK/ERK and PI3K/AKT, leading to reduction of ERK and AKT phosphorylation, and increased BAX and decreased BCL-XL protein expression. Moreover, treatment with iHCK-37 reduced MDS and AML CD34-positive cell numbers inside a 3D-structure but did not affect normal CD34-positive cell numbers. In vivo analysis showed that leukemic mice treated with iHCK-37 had reduced ERK and AKT proteins phosphorylation levels and leukocyte numbers. In conclusion, the iHCK-37 inhibitor has anti-neoplastic activity in leukemia cells without altering apoptosis and survival rate of normal cells, suggesting on-target malignant cell killing activity as a single agent or in combination with 5-Azacytidine or Cytarabine.

Highly Selective Binding and Inhibition of Pyr-His-Pro-NH2 (TRH) Function using a Polypyridinyl Macrocyclic Receptor with an Amphiphilic Cavity.

Macrocycle, cyclo[4] [(1,3-(4,6)-dimethylbezene)[4](2,6-(3,5)-dimethylpyridine (B4P4), shows highly selective binding affinity with protirelin (Pyr-His-Pro-NH2 ; TRH) among the tested 26 drug or drug adductive substrates. The stable complexation in a 1:1 manner was fully characterized in solution, gas phase, and solid state study. Furthermore, B4P4 acts as an efficient TRH inhibitor even at [macrocycle]:[drug] <1:300, both in membrane transport and cellar incubation. The current work provides an unprecedented strategy for macrocycles to be efficiently used in drug target therapy.

Purification and Characterization of Glucose 6-Phosphate Dehydrogenase, 6-Phosphogluconate Dehydrogenase, and Glutathione Reductase from Rat Heart and Inhibition Effects of Furosemide, Digoxin, and Dopamine on the Enzymes Activities.

The present study was aimed to investigate characterization and purification of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and glutathione reductase from rat heart and the inhibitory effect of three drugs. The purification of the enzymes was performed using 2',5'-ADP sepharose 4B affinity material. The subunit and the natural molecular weights were analyzed by SDS-PAGE and gel filtration. Biochemical characteristics such as the optimum temperature, pH, stable pH, and salt concentration were examined for each enzyme. Types of product inhibition and Ki values with Km and Vmax values of the substrates and coenzymes were determined. According to the obtained Ki and IC50 values, furosemide, digoxin, and dopamine showed inhibitory effect on the enzyme activities at low millimolar concentrations in vitro conditions. Dopamine inhibited the activity of these enzymes as competitive, whereas furosemide and digoxin inhibited the activity of the enzyme as noncompetitive.

Purification and biochemical characterization of glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and glutathione reductase from rat lung and inhibition effects of some antibiotics.

G6PD, 6PGD and GR have been purified separately in the single step from rat lung using 2', 5'-ADP Sepharose 4B affinity chromatography. The purified enzymes showed a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The molecular weights of the enzymes were estimated to be 134 kDa for G6PD, 107 kDa for 6PGD and 121 kDa for GR by Sephadex G-150 gel filtration chromatography, and the subunit molecular weights was respectively found to be 66, 52 and 63 kDa by SDS-PAGE. Optimum pH, stable pH, optimum ionic strength, optimum temperature, KM and Vmax values for substrates were determined. Product inhibition studies were also performed. The enzymes were inhibited by levofloxacin, furosemide, ceftazidime, cefuroxime and gentamicin as in vitro with IC50 values in the range of 0.07-30.13 mM. In vivo studies demonstrated that lung GR was inhibited by furosemide and lung 6PGD was inhibited by levofloxacin.

Effect of apatinib on the pharmacokinetics of tramadol and O-desmethyltramadol in rats.

Since the combination of anticancer drugs and opioids is very common, apatinib and tramadol are likely to be used in combination clinically. This study evaluated the effects of apatinib on the pharmacokinetics of tramadol and its main metabolite O-desmethyltramadol in Sprague-Dawley (SD) rats and the inhibitory effects of apatinib on tramadol in rat liver microsomes (RLMs), human liver microsomes (HLMs) and recombinant human CYP2D6.1. The samples were determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The in vivo results showed that compared with the control group, apatinib increased the AUC(0-t), AUC(0-∞) and Cmax values of tramadol and O-desmethyltramadol, and decreased the values of VZ/F and CLz/F. In addition, the MRT(0-t), MRT(0-∞) values of O-desmethyltramadol were increased. In vitro, apatinib inhibited the metabolism of tramadol by a mixed way with IC50 of 1.927 µM in RLMs, 2.039 µM in HLMs and 15.32 µM in CYP2D6.1. In summary, according to our findings, apatinib has a strong in vitro inhibitory effect on tramadol, and apatinib can increase the analgesic effect of tramadol and O-desmethyltramadol in rats.

Recoding of Nonsense Mutation as a Pharmacological Strategy.

Approximately 11% of genetic human diseases are caused by nonsense mutations that introduce a premature termination codon (PTC) into the coding sequence. The PTC results in the production of a potentially harmful shortened polypeptide and activation of a nonsense-mediated decay (NMD) pathway. The NMD pathway reduces the burden of unproductive protein synthesis by lowering the level of PTC mRNA. There is an endogenous rescue mechanism that produces a full-length protein from a PTC mRNA. Nonsense suppression therapies aim to increase readthrough, suppress NMD, or are a combination of both strategies. Therefore, treatment with translational readthrough-inducing drugs (TRIDs) and NMD inhibitors may increase the effectiveness of PTC suppression. Here we discuss the mechanism of PTC readthrough and the development of novel approaches to PTC suppression. We also discuss the toxicity and bioavailability of therapeutics used to stimulate PTC readthrough.

N-(4-[18F]fluorobenzyl)cholylglycine, a potential tracer for positron emission tomography of enterohepatic circulation and drug-induced inhibition of ileal bile acid transport. A proof-of-concept PET/CT study in pigs.

INTRODUCTION: Enterohepatic circulation (EHC) of conjugated bile acids is an important physiological process crucial for bile acids to function as detergents and signal carriers. Perturbation of the EHC by disease or drugs may lead to serious and life-threatening liver and gastrointestinal disorders. In this proof-of-concept study in pigs, we investigate the potential of N-(4-[18F]fluorobenzyl)cholylglycine ([18F]FBCGly) as tracer for quantitative positron emission tomography (PET) of the EHC of conjugated bile acids. METHODS: The biodistribution of [18F]FBCGly was investigated by PET/CT in domestic pigs following intravenous and intraileal administration of the tracer. Hepatic kinetics were estimated from PET and blood data using a 2-tissue compartmental model and dual-input of [18F]FBCGly. The ileal uptake of [18F]FBCGly was investigated with co-injection of nifedipine and endogenous cholyltaurine. Dosimetry was estimated from the PET data using the Olinda 2.0 software. Blood, bile and urine samples were analyzed for possible fluorine-18 labelled metabolites of [18F]FBCGly. RESULTS: [18F]FBCGly was rapidly taken up by the liver and excreted into bile, and underwent EHC without being metabolized. Both nifedipine and endogenous cholyltaurine inhibited the ileal uptake of [18F]FBCGly. The flow-dependent hepatic uptake clearance was estimated to median 1.2 mL blood/min/mL liver tissue. The mean residence time of [18F]FBCGly in hepatocytes was 4.0 ± 1.1 min. Critical organs for [18F]FBCGly were the gallbladder wall (0.94 mGy/MBq) and the small intestine (0.50 mGy/MBq). The effective dose for [18F]FBCGly was 36 µSv/MBq. CONCLUSION: We have shown that [18F]FBCGly undergoes EHC in pigs without being metabolized and that its ileal uptake is inhibited by nifedipine and endogenous bile acids. Combined with our previous findings in rats, we believe that [18F]FBCGly has potential as PET tracer for assessment of EHC of conjugated bile acids under physiological conditions as well as conditions with perturbed hepatic and ileal bile acid transport.