Avanafil Metabolite M-16

Avanafil Metabolite M-16 is a benzothiazole-derived pyrazoline derivative arising from oxidative metabolism of the parent compound. It retains the core 2-aminothiazole scaffold of Avanafil but features a hydroxylated phenethyl side chain and a desmethylated pyrazoline ring. The metabolite exhibits a 4-hydroxy substitution on the terminal phenyl ring, disrupting the original arylamine pharmacophore. This structural modification reduces PDE5 inhibitory activity while enhancing polarity, facilitating detection in bioanalytical matrices. It functions as an HPLC reference standard for quantifying oxidative degradation pathways in Avanafil drug substance stability studies.