Keywords: 2NF; 2-nitroflourene; AAI; air agar interface; AAN; 2-aminoanthracene; FI; fold increase; ICH; International Commission on Harmonization; ICR-191; 6-âchloro-â9-â[3-â(2-âchloroethylamino)âpropylamino]â-â2-âmethoxyacridine dihydrochloride;