In vitro: |
Anticancer Drugs. 1994 Apr;5(2):202-6. | Activity of CPT-11 (irinotecan hydrochloride), a topoisomerase I inhibitor, against human tumor colony-forming units.[Pubmed: 8049503] | CPT-11 (irinotecan hydrochloride, 7-ethyl-10-[4-(piperidino)-1-piperidino] carbonyloxy-camptothecin) is a semisynthetic camptothecin derivative developed in Japan. METHODS AND RESULTS: The inhibitory activity of CPT-11 against human tumor colony-forming units from freshly explanted human tumors was explored using a soft agar cloning system. Final CPT-11 concentrations of 0.3-3.0 micrograms/ml were used for a 1 h exposure. At a concentration of 3.0 micrograms/ml antitumor activity was seen against colorectal, ovarian, nonsmall-cell lung, breast cancer and mesothelioma colony-forming units. CONCLUSIONS: CPT-11 should have activity against a broad spectrum of tumors in patients. |
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In vivo: |
Cancer Chemother Pharmacol. 1998;42(4):280-6. | Inhibition of intestinal microflora beta-glucuronidase modifies the distribution of the active metabolite of the antitumor agent, irinotecan hydrochloride (CPT-11) in rats.[Pubmed: 9744772] | SN-38, a metabolite of irinotecan hydrochloride (CPT-11), is considered to play a key role in the development of diarrhea as well as in the antitumor activity of CPT-11. We have previously found that the inhibition of beta-glucuronidase, which hydrolyzes detoxified SN-38 (SN-38 glucuronide) to reform SN-38, in the lumen by eliminating the intestinal microflora with antibiotics, markedly ameliorates the intestinal toxicity of CPT-11 in rats. In this study we compared the disposition of CPT-11 and its metabolites in rats treated with and without antibiotics.
METHODS AND RESULTS:
Rats were given drinking water containing 1 mg/ml penicillin and 2 mg/ml streptomycin from 5 days before the administration of CPT-11 (60 mg/kg i.v.) and throughout the experiment. CPT-11, SN-38 glucuronide and SN-38 concentrations in the blood, intestinal tissues and intestinal luminal contents were determined by HPLC.
Antibiotics had little or no effect on the pharmacokinetics of CPT-11, SN-38 glucuronide or SN-38 in the blood, or in the tissues or contents of the small intestine, which has less beta-glucuronidase activity in its luminal contents. In contrast, antibiotics markedly reduced the AUC1-24 h of SN-38 (by about 85%) in the large intestine tissue without changing that of CPT-11, and this was accompanied by a complete inhibition of the deconjugation of SN-38 glucuronide in the luminal contents.
CONCLUSIONS:
These results suggest that SN-38, which results from the hydrolysis of SN-38 glucuronide by beta-glucuronidase in the intestinal microflora, contributes considerably to the distribution of SN-38 in the large intestine tissue, and that inhibition of the beta-glucuronidase activity by antibiotics results in decreased accumulation of SN-38 in the large intestine. |
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