Synthesis and mutagenic risk of avanafil's potential genotoxic impurities

In the technical route for the synthesis of avanafil, 1-ethyl-(3-dimethylaminopropyl)carbamyldiimide hydrochloride (EDCI) and 1-hydroxybenzotriazole (HOBT) are used as reactive acid-amine binding agents. HOBT contains trace amounts of hydrazine residue, and there is a risk of introducing potentially mutagenic impurities with hydrazide-containing structures. The potentially genotoxic impurities E (Imp-E) and F (Imp-F) of avanafil with altering hydrazide-structure were synthesized by chemical method; subsequently, the impurities were evaluated and classified according to ICH M7 guidelines. Two complementary quantitative structure-activity relationship (QSAR) evaluation systems (Derek and Sarah) based on expert rules and statistics were used to preliminarily predict the genotoxicity of Imp-E and Imp-F, and the prediction result of E was suspected to be positive. In the Ames test of Imp-E and Imp-F, in the dose range of 62.5-1000 μg per plate, with or without the presence of metabolic activation system S9, the number of revertant colonies did not exceed 2 times the number of colonies in the solvent control group and did not show a dose-response relationship, and the test results were negative. Imp-E and Imp-F were determined to be negative for genotoxicity, which could be controlled as class 5 in ICH M7, that is, non mutagenic impurity.