Safety, Tolerability, and Pharmacokinetics of Single and Multiple Ascending Oral Doses of Youkenafil Hydrochloride, a Phosphodiesterase Type 5 Inhibitor, in Healthy Chinese Male Volunteers

Drug interaction evaluation of the novel phosphodiesterase type 5 inhibitor tunodafil (youkenafil): Effects of tunodafil on omeprazole pharmacokinetics based on CYP2C19 gene polymorphism, and effects of ritonavir on tunodafil pharmacokinetics

PURPOSE

To evaluate the drug-drug interactions (DDI) of tunodafil (youkenafil), a novel phosphodiesterase type 5 inhibitor, its inhibitory effects on CYP450 enzymes in vitro and its clinical trials in combination with ritonavir or omeprazole were conducted.

METHODS

The inhibitory effect of tunodafil on seven major CYP450 enzymes in human liver microsomes was investigated by probe substrate method. The effect of tunodafil on the pharmacokinetics of omeprazole (CYP2C19 substrate) in 40 healthy subjects, who received a single dose of 40 mg omeprazole in combination with tunodafil on the day 8 after taking 100 mg tunodafil daily for 7 days, was assessed based on CYP2C19 genotypes. The clinical DDI of ritonavir (potent CYP3A4 inhibitor) on tunodafil was studied in 28 healthy subjects who received a single dose of 50 mg tunodafil in combination with ritonavir on the day 6 after taking ritonavir twice a day for 5 days.

RESULTS

Tunodafil showed moderate inhibition on CYP2C19 and CYP3A4/5 in vitro. When co-administration omeprazole with tunodafil, the AUC of omeprazole in the Extensive, Intermediate and Poor Metabolizers increased by 26 %, 37 % and 21 %, respectively. After co-administration tunodafil with ritonavir, ritonavir increased the AUC and Cmax of tunodafil in human by about 78- fold and 13-fold respectively.

CONCLUSIONS

Tunodafil slightly increased omeprazole exposure in the Extensive and Intermediate Metabolizers of CYP2C19, but had no significant effect on omeprazole exposure in the Poor Metabolizers. Ritonavir could strongly inhibit the metabolism of tunodafil, and the combination of tunodafil with ritonavir should be prohibited.

An overview of conventional and investigational phosphodiesterase 5 inhibitors for treating erectile dysfunction and other conditions

INTRODUCTION

There is a rising concern about developing innovative, efficacious PDE5I molecules that provide better safety, efficacy, and tolerability with less adverse effects. Innovative PDE5I with dual targets have also been defined in the literature. Additionally, some of PDE5I are able to selectively inhibit other enzymes such as histone deacetylase, acetylcholine esterase, and cyclooxygenase or act as nitric oxide donors. This review presents knowledge concerning the advanced trends and perspectives in using PDE5I in treatment of ED and other conditions.

AREAS COVERED

Pre-clinical and early clinical trials that investigated the safety, efficacy, and tolerability of novel PDE5I such as Udenafil, Mirodenafil, Lodenafil, Youkenafil, Celecoxib, and TPN729 in treatment of ED and other conditions.

EXPERT OPINION

Preclinical and limited early clinical studies of the new molecules of PDE5I have demonstrated encouraging results; however, safety, efficacy, and tolerability are still issues that necessitate further long-term multicenter clinical studies to ensure justification of their uses in treatment of ED and other conditions. Progress in molecular delivery techniques and tailored patient-specific management and additional therapeutic technology will dramatically improve care for ED and other conditions. The dream of ED and many other conditions becoming more effectively managed may be feasible in the near future.

Age-related pharmacokinetics differences were observed between young and elderly populations of a novel PDE5 inhibitor, youkenafil, and its metabolite M459

PURPOSE

Youkenafil is a novel oral selective PDE5 inhibitor for treating Erectile Dysfunction. This investigation assessed pharmacokinetics (PK), safety, and tolerability of youkenafil and its main metabolite (M459) after taking 100 mg youkenafil hydrochloride tablets in elderly and young subjects.

METHODS

This Phase I, single-center, open-label, parallel-group, single-dose study was conducted on 24 individuals (12 elders and 12 youngsters). Each subject received a single oral 100 mg youkenafil hydrochloride tablets. Blood samples were collected before medication and up to 48 h after medication for PK analysis. Safety and tolerability were also assessed, including treatment-emergent adverse events (TEAEs), laboratory tests, 12-lead ECG, vital sign inspections, color vision examinations, and physical examinations.

RESULTS

Plasma concentrations of youkenafil and M459 were quantified. PK parameters were determined by non-compartmental analysis. Median Tmax of elderly and young groups were both 0.733 h. However, Cmax, AUC0-t, and AUC0-∞ of youkenafil were separately 16.8 %, 37.2 %, and 37.5 % higher in elders and t1/2 of youkenafil was 2.1 h longer in elders. More great differences were observed for M459. T1/2 values were 4.05 h longer in elders, with Cmax, AUC0-t and AUC0-∞ 73.7 %, 81.1 %, and 81.4 % higher in elders. Two (8.3 %) elderly subjects reported TEAEs (all grade Ⅰ in severity) and both recovered without any treatment. No serious adverse reactions (SAEs) or serious unexpected suspected adverse reactions (SUSARs) occurred in this study.

CONCLUSIONS

This was the first PK research of youkenafil and M459 in elderly men. PK parameters differences between youkenafil and M459 were comparable between elderly and young groups. Moreover, safety and tolerability of youkenafil were favorable in both groups.

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.

Phosphodiesterase 5 inhibitors: preclinical and early-phase breakthroughs for impotence treatments

INTRODUCTION

Erectile dysfunction (ED) is a condition that affects millions of men worldwide and is characterized by the inability to achieve or maintain an erection for satisfactory sexual performance. There are numerous treatment options for ED, including medications, mechanical assist devices, and surgical management; however, first-line treatment is usually a phosphodiesterase 5 (PDE5) inhibitor. There is a growing interest in developing novel, efficacious PDE5 inhibitors that provide better quality, safety, and tolerability profiles with less adverse effects. Our review of udenafil, mirodenafil, youkenafil, lodenafil, and SLx-2101 analyzes the safety, efficacy, and pharmacokinetic properties of these new ED drugs.

AREAS COVERED

Clinical trials demonstrated improved scores in questionnaires, such as the International Index of Erectile Function and Sexual Encounter Profile, for udenafil, mirodenafil, and lodenafil, while youkenafil and SLx-2101 revealed enhanced safety and tolerability in early pharmacokinetic studies.

EXPERT OPINION

It is our opinion that more robust clinical trials are required before these medications can be made available in the United States. Additionally, the field of urology may benefit from pursuing other avenues of pharmacotherapy, such as injections, tablets with a different mechanism of action, or stem cell therapy, to restore the integrity of the endothelium within the penis.