Which of the following drugs is topoisomerase I inhibitor?: (A) Doxorubicin, (B) Irinotecan, (C) Etoposide, (D) Vincristine
Answer is B. Camptothecin derivatives like topotecan and irinotecan act by inhibiting topoisomerase-I whereas Epipodophyllotoxins (etoposide and teniposide) and anthracyclines (doxorubicin, daunorubicin etc.) act by inhibiting topoisomerase-II.