Novel phosphodiesterase type 5 modulators: a patent survey (2008 - 2010).

INTRODUCTION: The inhibition of cyclic nucleotide PDE5 has been clinically validated as an effective treatment for erectile dysfunction and pulmonary arterial hypertension. There are three PDE5 inhibitors (sildenafil, vardenafil and tadalafil) approved worldwide and a further two agents (udenafil and mirodenafil) approved only in Korea. These first generation agents are perceived to have flaws in selectivity over other PDEs: slow onset, duration of action or CNS penetration, which has driven further research to identify optimal PDE5 inhibitors for the current pathologies. Several clinical trials have been reported to investigate the potential for PDE5 inhibitors to treat additional indications, which might require agents with different biological and/or pharmacokinetic profiles. AREAS COVERED: This review provides a summary of developments in the patent and open literature over the period 2008 - 2010. EXPERT OPINION: Avanafil, the first of a new generation of PDE5 inhibitors, has shown encouraging efficacy in clinical trials, and is likely to result in a new drug application filing during 2011, followed by a possible launch in 2012. Judging by the wealth of different structural series being claimed in patents, it seems that the selectivity and pharmacokinetic issues facing the first generation can be addressed through novel chemical matter.

Determination of mirodenafil and sildenafil in the plasma and corpus cavernous of SD male rats.

The purpose of the present study was to determine sildenafil and a novel PDE-5 inhibitor, mirodenafil in the plasma and corpus cavernosum tissue of rats to compare their pharmacokinetic properties. The concentrations of mirodenafil and sildenafil in the rat plasma and corpus cavernosum tissue samples were analyzed using LC-MS/MS after a single oral administration at a dose of 40mg/kg to rats. Although the T(max), Tlambda(1/2) and MRT were not different between mirodenafil and sildenafil, the C(max) and AUC of mirodenafil were significantly higher than those of sildenafil in the plasma and corpus cavernosum tissue. Consequently mirodenafil remained longer than sildenafil in the plasma and tissue. This may provide pharmacokinetic evidence for assessment of the in vivo efficacy of mirodenafil and sildenafil.

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

A novel method for the quantitation of yonkenafil, a new synthetic phosphodiesterase V inhibitor, in rat plasma using high-performance liquid chromatography/tandem mass spectrometry (LC-MS/MS) has been developed. The analyte and internal standard (diazepam) were extracted from plasma (100 microl) by liquid-liquid extraction and separated on a C18 column using 10mM ammonium acetate buffer: methanol (15:85, v/v) as mobile phase in a run time of 3.0 min. The detector was a Q-trap mass spectrometer with an ESI interface operating in the multiple reaction monitoring (MRM) mode. The assay was linear over the concentration range 1.0-1000 ng/ml with a limit of detection of 0.20 ng/ml. Intra- and inter-day precision (as relative standard deviation) were both within 8.45% with good accuracy. The method was successfully applied to a preclinical pharmacokinetic study of yonkenafil in rat after sublingual, oral and intravenous administration. The results demonstrate that the sublingual route gives a higher bioavailablity than the oral route and may represent a useful alternative route of yonkenafil administration.