A rapid and sensitive LC–MS/MS assay to quantify yonkenafil in rat plasma with application to preclinical pharmacokinetics studies

LC-MS/MS methods for simultaneous determination of youkenafil and its metabolite M1 in human seminal plasma and plasma: Application to evaluate the acute effect of youkenafil on semen quality and its pharmacokinetics in human

Youkenafil is a novel Phosphodiesterase type 5 inhibitor used for treating erectile dysfunction. N-desethyl compound of youkenafil (M1) is its main active metabolite. In this study, two methods were developed and validated for the simultaneous determination of youkenafil and M1 by HPLC-MS/MS in human matrices including seminal plasma and plasma, in which the multiple reaction monitoring and electrospray ionization in positive mode were adopted, and the deuterated youkenafil (youkenafil-d5) was selected as the internal standard. The collected semen sample was kept at room temperature for approximately 30 min until fully liquefied. The volume of the liquefied semen was measured and then divided into two parts. One part was centrifuged to obtain the seminal plasma for the content detection of youkenafil and M1, while the other part was used for routine semen analysis. The chromatographic separation was accomplished with the column of Poroshell 120 EC-C18 (5 × 2.1 mm, 2.7 μm, Agilent). Protein precipitation with methanol was used for the pretreatment of seminal plasma and plasma. The intra-run and inter-run precisions were less than 6.4 % (relative standard deviation) and accuracies were all within -4.7 %-6.8 % (relative error) in both matrices. All other validated bioanalytical parameters were within the acceptance criteria set by the FDA. The methods were successfully applied to different clinical studies of youkenafil. In the clinical study of the acute effect of youkenafil on semen quality in healthy males, the content of youkenafil in seminal plasma was extremely low. Concentrations of youkenafil and M1 in seminal plasma were lower than those in plasma, at 20.7 % and 4.49 % of the plasma concentration, respectively. There was no significant acute effect of youkenafil on semen quality. In the pharmacokinetic study of youkenafil after single dose-escalation administration, the exposure to youkenafil and M1 was non-linear with the dose in the range of 100-400 mg.

Simultaneous quantitative analysis of polyethylene glycol (PEG), PEGylated paclitaxel and paclitaxel in rats by MS/MSALL technique with hybrid quadrupole time-of-flight mass spectrometry

PEGylation is practically one of most important modifications of drugs including small molecules, peptides and proteins, which has been proven to dramatically improve physicochemical properties and pharmacokinetic behavior of the PEGylated drugs. However, it is a challenge currently to quantitatively analyze PEG and PEGylated drugs by various analytical methods, even mass spectrometry because of multiple parent ion distribution of PEG caused by its polydispersity of molecular weight. Here we developed a robust method with MS/MS^ALL technique using electrospray ionization (ESI) source coupled high resolution Quadrupole Time-of-Flight (Q-TOF) mass spectrometry for the quantification of PEG2K-Paclitaxel (PEG-PTX) and its two metabolites, PEG and Paclitaxel (PTX). The analysis was performed on a 300SB-C18 column with acetonitrile and 0.1% formic acid as the mobile phase. Samples were simply prepared by protein precipitation in a small quantity of plasma (50μL). Calibration curve was linear within the range of 50.0-4000ng/mL for PEG and PEG-PTX and 1.0-1000ng/mL for PTX. The intra- and inter-day precisions were 3.2-6.9% and 3.1-6.9% for PEG, 4.1-7.8% and 4.0-9.9% for PEG-PTX, and 3.3-4.8% and 3.1-6.9% for PTX, respectively. The recoveries were greater than 90% with low matrix effects. Afterwards, the newly developed method was successfully applied to support a preclinical pharmacokinetic study in six rats after single intravenous injection of PEG-PTX (51.7mg/kg).

Rapid and sensitive liquid chromatography with tandem mass spectrometry method for the simultaneous quantification of yonkenafil and its major metabolites in rat plasma

Yonkenafil is a promising drug for treatment of male erectile dysfunction. Previous studies showed that the piperazine-N,N'-deethylation metabolite, piperazine-N-deethylation metabolite, and piperazine-N-deethylation-N,N'-deethylation metabolite were the major metabolites of yonkenafil after extensive metabolism. We developed a sensitive and selective method for the simultaneous quantification of yonkenafil and its major metabolites using high-throughput liquid chromatography with tandem mass spectrometry. Analytes and internal standard were extracted from a small quantity of plasma (50 μL) using liquid-liquid extraction with diethyl ether/dichloromethane (60:40, v/v), and the baseline separation was achieved on Zorbax SB-C₁₈ column using ammonia/water/methanol (0.2:20:80, v/v/v) as the mobile phase. The assay was performed with an electrospray positive ionization mass spectrometry through the multiple-reaction monitoring mode within 2 min. Calibration curve of the method was linear within the range of 1.00-1000 ng/mL for all the analytes with the intra- and interday precisions of 4.0-5.2 and 4.0-5.3% for yonkenafil, 3.1-4.9 and 3.1-5.2% for the piperazine-N,N'-deethylation metabolite, 4.8-6.8 and 4.8-7.3% for the piperazine-N-deethylation metabolite, and 2.9-6.1 and 5.4-6.3% for the piperazine-N-deethylation-N,N'-deethylation metabolite, respectively. The recoveries were above 90% with low matrix effects. The validated assay was successfully applied to support a preclinical pharmacokinetic study in six rats using a single oral dose of yonkenafil (8 mg/kg).

Yonkenafil: a novel phosphodiesterase type 5 inhibitor induces neuronal network potentiation by a cGMP-dependent Nogo-R axis in acute experimental stroke

Yonkenafil is a novel phosphodiesterase type 5 (PDE5) inhibitor. Here we evaluated the effect of yonkenafil on ischemic injury and its possible mechanism of action. Male Sprague-Dawley rats underwent middle cerebral artery occlusion, followed by intraperitoneal or intravenous treatment with yonkenafil starting 2h later. Behavioral tests were carried out on day 1 or day 7 after reperfusion. Nissl staining, Fluoro-Jade B staining and electron microscopy studies were carried out 24h post-stroke, together with an analysis of infarct volume and severity of edema. Levels of cGMP-dependent Nogo-66 receptor (Nogo-R) pathway components, hsp70, apaf-1, caspase-3, caspase-9, synaptophysin, PSD-95/neuronal nitric oxide synthases (nNOS), brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase B (TrkB) and nerve growth factor (NGF)/tropomyosin-related kinase A (TrkA) were also measured after 24h. Yonkenafil markedly inhibited infarction and edema, even when administration was delayed until 4h after stroke onset. This protection was associated with an improvement in neurological function and was sustained for 7d. Yonkenafil enlarged the range of penumbra, reduced ischemic cell apoptosis and the loss of neurons, and modulated the expression of proteins in the Nogo-R pathway. Moreover, yonkenafil protected the structure of synapses and increased the expression of synaptophysin, BDNF/TrkB and NGF/TrkA. In conclusion, yonkenafil protects neuronal networks from injury after stroke.