<prompt> Which one of the following drugs is Topoisomerase 1 inhibitor ?DoxorubicinIrinotecanEtoposideVincristine  <response>: Ans. is b i.e., Irinotecan Topoisomerase I inhibitors -- camptothecans Irinotecan, tropotecan. Topoisomerase II inhibitors Anthracyclines doxorubicin, daunorubicin and Epipodophyllotoxin Etoposid, teniposide. 