Topotecan is an antineoplastic agent used to treat ovarian cancer, small cell lung cancer, or cervical cancer. Hycamtin. Generic Name Topotecan DrugBank Accession Number DB01030 Background. An antineoplastic agent used to treat ovarian cancer. It works by stabilizing the cleavable complex formed between topoisomerase I and DNA, preventing relegation of single strand breaks that arise during DNA replication and thereby converting those lesions into lethal double strand breaks in S phase cells; topotecan is a semisynthetic camptothecin analogue available in intravenous and oral formulations, exists in equilibrium between an active lactone form and an inactive carboxylate form that is pH dependent, is primarily cleared by renal and hepatic routes with dose adjustments required in renal impairment, and its principal toxicities are dose dependent myelosuppression with neutropenia and thrombocytopenia along with gastrointestinal effects and potential mucositis, so therapy requires laboratory monitoring of blood counts and appropriate supportive care.
Parent: Topotecan
The impurity and related compound profile for topotecan typically reflects hydrolytic opening of the lactone ring to the carboxylate, N-demethylation, oxidative N-oxide derivatives, ring-cleavage products and minor process-related residuals; because the lactone equilibrium is pH sensitive, degradation to the carboxylate increases under alkaline or aqueous conditions and with elevated temperature, and analytical control is usually performed by stability-indicating reversed phase HPLC with orthogonal confirmation by LC-MS; industry specifications commonly control individual specified impurities at low ppm levels or fractions of a percent for the drug substance and drug product, for example individual specified impurities often limited to 0.1 to 0.5 percent and total impurities to around 1.0 percent for the active pharmaceutical ingredient, with tighter product-specific limits set by manufacturers and regulators and stability strategies that include pH control, low temperature storage, limited aqueous exposure and protection from light.
Topotecan is used as chemotherapy for certain gynecologic and thoracic malignancies, most commonly for recurrent ovarian cancer, for second-line treatment of small cell lung cancer, and for selected cases of cervical cancer; it may be given intravenously or orally depending on the formulation and regimen.
Success rates depend on disease, prior therapies and patient factors; as a single agent in recurrent ovarian cancer response rates reported in clinical series vary widely with higher responses in platinum sensitive relapse and lower responses in platinum resistant disease, and for second-line small cell lung cancer topotecan produces modest objective response rates and symptom relief; clinicians interpret success in terms of response rate, progression free interval and symptom control rather than a single universal percentage.
Topotecan is effective as a targeted cytotoxic that preferentially affects S phase tumor cells by inhibiting topoisomerase I; effectiveness is regimen dependent and generally results in objective responses and symptom improvement in settings where it is indicated, but clinical benefit is often modest and balanced against hematologic toxicity, so selection of patients, dosing schedule and supportive measures are important determinants of overall effectiveness.
Both are camptothecin derivatives that inhibit topoisomerase I, but irinotecan is a prodrug converted in vivo to the active metabolite SN-38 while topotecan is administered as an active drug; they differ in primary indications, dosing and toxicity profiles with irinotecan frequently used in colorectal cancer and more associated with acute and delayed diarrhea, whereas topotecan is used for ovarian and small cell lung cancers and is more commonly associated with myelosuppression; pharmacokinetics, routes of administration and metabolism also differ between the two agents.
