Preparation and evaluation of radioiodinated avanafil: A novel potential radiopharmaceutical for the diagnostic evaluation of erectile dysfunction.

Avanafil, a selective second-generation phosphodiesterase-5 inhibitor, was successfully labeled with iodine-125 via electrophilic and different factors affecting the labeling efficiency were studied. The labeled compound exhibited in-vitro stability of more than 24 h with a maximum labeling yield of up to 98.4 ± 1.9 %. Molecular modeling and in-vitro assessment of tracer inhibitory activity were performed to ensure that radiolabeling did not affect its binding ability to the target. Biodistribution studies were performed in normal rats and models of erectile dysfunction. The tracer specifically accumulated in the penis, and the clearance appeared to take place via the hepatobiliary route. Results suggested the usefulness of radiolabeled avanafil as a promising tracer for erectile dysfunction.