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[Topoisomerase inhibitors developing in Japan]
1Fourth Dept. of Internal Medicine, Teikyo University.
Abstract:
Irinotecan hydrochloride (CPT-11), topotecan, sobuzoxane, NC-190, and IST-622 are unique topoisomerase inhibitors and are investigational in Japan. CPT-11 is a water-soluble, semisynthetic derivative of camtothecin. CPT-11 shows its anticancer activity by inhibiting topoisomerase I activity, now a target of anticancer agents with major interest. Recent clinical trials reveal that CPT-11 is very effective in the treatment of cancer including lung cancer, cervical cancer, ovary cancer, stomach cancer, colon cancer, and non-Hodgkin's lymphoma. Major dose limiting toxicities are leukopenia and diarrhea, and are dose related. Topotecan is an another semisynthetic derivative of camtothecin and is also topoisomerase I inhibitor. Topotecan has undergone phase I clinical evaluations in USA, europe, and recently in Japan. DLF are leukopenia and neutropenia. Topotecan is more hydrophilic than its parent compound and shows lesser protein binding. Renal excretion appears to be the major route of elimination. Sobuzoxane (MST-16) is a unique derivative of dioxopiperazine, an inhibitor of topoisomerase II. In phase II studies, definite anticancer effects are observed in patients with non-Hodgkin's lymphoma and adult T-cell leukemia/lymphoma. Responses are seen even in pretreated cases. Leukopenia is also dose-limiting. Non-hematologic toxicities are mild and include alopecia and G.I. toxicities. NC-190 is a novel benzophenazine derivative with excellent antitumor activities against murine tumors. NC-190 also inhibits topoisomerase II. Now the drug is an early clinical phase II studies in Japan. Toxicities include bone marrow suppression, transient mild to moderate liver enzyme elevation, alopecia and mild G.I. toxicities. Tumor responses are occasionally encountered. IST-622 is a semisynthetic derivative of chartreusin. The drug is an inhibitor of topoisomerase II (and I in high concentration). IST-622 shows excellent, broad anticancer activity against murine tumors. The drug is well absorbed from small intestine. IST-622 is now in phase I clinical trial in Japan.
Insights
Investigational topoisomerase inhibitors irinotecan hydrochloride (CPT-11) and topotecan show efficacy in various cancers. Other agents like sobuzoxane, NC-190, and IST-622 are also being studied for their anticancer properties.
Area of Science:
- Oncology
- Pharmacology
Background:
- Topoisomerase inhibitors are a significant class of anticancer agents.
- Irinotecan hydrochloride (CPT-11), topotecan, sobuzoxane, NC-190, and IST-622 are investigational drugs in Japan targeting topoisomerases.
Purpose of the Study:
- To review the status and preliminary findings of novel topoisomerase inhibitors under investigation in Japan.
- To highlight their mechanisms of action, therapeutic potential, and toxicities.
Main Methods:
- Review of clinical trial data and preclinical studies for CPT-11, topotecan, sobuzoxane, NC-190, and IST-622.
- Summary of efficacy in various cancer types and dose-limiting toxicities.
Main Results:
- CPT-11 and topotecan (topoisomerase I inhibitors) demonstrate efficacy in lung, cervical, ovarian, stomach, colon cancers, and lymphoma, with leukopenia and diarrhea as dose-limiting toxicities.
- Sobuzoxane, NC-190, and IST-622 (topoisomerase II inhibitors) show activity in non-Hodgkin's lymphoma, adult T-cell leukemia/lymphoma, and various murine tumors, with myelosuppression as a common toxicity.
Conclusions:
- These novel topoisomerase inhibitors represent promising therapeutic options for various malignancies.
- Further clinical evaluation is warranted to establish their role in cancer treatment.