Topoisomerase inhibitors are used to treat various cancers, including lung cancer, colorectal cancer, and ovarian cancer. These medications work by interfering with type I or type II topoisomerase enzymes to prevent cancer cells from multiplying. Topoisomerase inhibitors come in different forms, including oral pills and injectable solutions. Examples include etoposide, irinotecan (Camptosar), and topotecan (Hycamtin). Your cancer specialist will be in charge of choosing the best treatment regimen for you.