PEGylated liposome IHL-305 markedly improved the survival of ovarian cancer peritoneal metastasis in mouse.

BACKGROUND: Advanced ovarian cancer is characterized by peritoneal metastasis and the accumulation of ascites. Peritoneal metastasis of ovarian cancer is a major cause of the negative treatment outcome, as these metastases are resistant to most chemotherapy regimens. The aim of this study was to clarify aggressive pathology of peritoneal metastasis and examine the therapeutic efficacy of a liposomal agent in the model. METHODS: A human cancer cell line ES-2 of ovarian clear cell carcinoma, known as a chemotherapy-resistant cancer, was cultured in nonadherent plate to form spheroid and single cell suspension was transplanted into mouse peritoneal cavity. The epidermal growth factor receptor (EGFR) pathways in the cellular aggregates were analyzed both spheroid and ascites. The pharmacokinetics and therapeutic efficacy of CPT-11 (45 mg/kg) and IHL-305 (45 mg/kg), an irinotecan-encapsulated liposome, were examined by intravenous administration. RESULTS: Established peritoneal metastasis model showed an accumulation of ascites. The activation of EGFR and Akt was demonstrated in cellular aggregates both in the spheroid and ascites. In ascites samples, the area under the curve of SN-38, the activated form of CPT-11, was 3.8 times higher from IHL-305-treated mice than from CPT-11-treated mice. IHL-305 prolonged the survival time and decreased the accumulation of ascites and tumor metastasis. The median survival time were 22, 37 and 54 days in the control, CPT-11-treated, and IHL-305-treated mice, respectively. CONCLUSIONS: EGFR/Akt pathway contributes to the aggressive progression in ES-2 peritoneal metastasis model and effective delivery into ascites of IHL-305 was thought to useful treatment for ovarian cancer with peritoneal metastasis.

Streptomycin alleviates irinotecan-induced delayed-onset diarrhea in rats by a mechanism other than inhibition of ß-glucuronidase activity in intestinal lumen.

Irinotecan hydrochloride (CPT-11) is a useful drug for cancer chemotherapy but sometimes induces severe diarrhea clinically. CPT-11 is mainly activated to SN-38 by carboxylesterase (CES) and then detoxified to SN-38 glucuronide (SN-38G) by UDP-glucuronosyltransferase (UGT) in the liver. SN-38G is excreted via bile and de-conjugated to SN-38 by ß-glucuronidase (ß-GLU) in the intestinal content. In order to clarify the alleviative effect of antibiotics on CPT-11-induced diarrhea, we examined whether penicillin G and streptomycin (SM) alleviate CPT-11-induced delayed-onset diarrhea using three diarrheal models, i.e., Wistar rats with repeated dosing of CPT-11 (60 mg/kg/day i.v. for 4 consecutive days) and Wistar and Gunn rats with a single dosing of CPT-11 (200 and 20 mg/kg i.v., respectively). Gunn rats have an inherited deficiency of UGT1A and cannot conjugate SN-38 to SN-38G. Therefore, onset of CPT-11-induced diarrhea in Gunn rats is not affected by ß-GLU activity. SM alleviated diarrhea in all three diarrheal models. The alleviation of diarrhea by SM in Gunn rats indicated that the effect of SM occurred by a mechanism other than the inhibition of ß-GLU activity. SM decreased CPT-11 and/or SN-38 concentrations in intestinal tissues and alleviated epithelial damage from the ileum to colon. SM did not inhibit ß-GLU activity in the cecal content. SM also inhibited the intestinal absorption of CPT-11 and decreased CES activity and increased UGT activity in the intestinal epithelium. These findings indicated that SM decreased the exposure of CPT-11 and SN-38 to the intestinal epithelium by inhibiting the absorption of CPT-11 from the intestinal lumen and the change of CES and UGT activities in the intestinal epithelium and alleviated delayed-onset diarrhea.

Involvement of UDP-glucuronosyltransferase activity in irinotecan-induced delayed-onset diarrhea in rats.

We assessed the involvement of UDP-glucuronosyltransferase (UGT) activity in episodes of irinotecan hydrochloride (CPT-11)-induced delayed-onset diarrhea using a mutant rat strain with an inherited deficiency of UGT1A (Gunn rats). Gunn rats exhibited severe diarrhea after the intravenous administration of CPT-11 at a dose of 20 mg/kg, whereas Wistar rats did not. In the epithelium of the small intestine and cecum in Gunn rats, the shortening of villi, degeneration of crypts, and destruction of the nucleus were observed. The AUC, MRT, and t (1/2) of CPT-11, and the AUC of 7-ethyl-10-hydroxycamptothecin (SN-38) in plasma were, respectively, 1.6-fold, 1.5-fold, 1.7-fold, and 6.5-fold higher, and the cumulative biliary excretion rate of SN-38 was 2.3-fold higher, in Gunn rats than Wistar rats. SN-38 glucuronide excreted via bile in Wistar rats was not de-conjugated in the small intestinal lumen. The SN-38 AUC values in small intestinal tissues were also 5.0 to 5.8-fold higher in Gunn rats than Wistar rats. In conclusion, Gunn rats developed severe delayed-onset diarrhea after i.v. administration of CPT-11 at a much lower dose. Severe intestinal impairments would be induced in Gunn rats through exposure to SN-38 at high levels for a long period mainly via the intestinal lumen and partially via the bloodstream. These results clarified that the deficiency of UGT activity contributed greatly to the induction of the CPT-11-induced delayed-onset diarrhea and epithelial impairment in the intestine. In the clinic, great care is needed when using chemotherapy with CPT-11 in patients with poor UGT activity.

Efficient and chemoselective N-acylation of 10-amino-7-ethyl camptothecin with poly(ethylene glycol).

A new poly(ethylene glycol) (PEG) conjugate of 10-amino-7-ethyl camptothecin, a potent antitumor analogue of camptothecin, has been synthesized and preliminary in vivo tests have been performed. Successful chemoselective N-acylation of 10-amino-7-ethyl camptothecin was accomplished using phenyl dichlorophosphate, a coupling reagent used in esterification of alcohols, while other coupling methods failed, due to the low nucleophilicity of the amino group in position 10. The conjugate was tested against P388 murine leukemia cell lines and resulted equipotent to CPT-11, a camptothecin analogue already in clinical use.

Synthesis, characterization, and preliminary in vivo tests of new poly(ethylene glycol) conjugates of the antitumor agent 10-amino-7-ethylcamptothecin.

Despite the high antitumor activity of camptothecins, few derivatives have been developed and tested for human treatment of solid tumors, due to unpredictable toxicity mainly connected to their poor water solubility. We report the conjugation of the antitumor agent 10-amino-7-hydroxy camptothecin (SN-392) to linear or branched poly(ethylene glycol)s (PEGs) of different loading capacity through a tri- or tetrapeptide spacer selectively cleaved by lysosomal enzymes (cathepsins). A synthetic strategy based on the chemoselective acylation of the aromatic amino group in the presence of the unprotected C20 tertiary alcohol allowed high overall yields. Two conjugates demonstrated good stability at physiological pH and in mouse plasma (nonspecific proteases) but slowly released the drug payload in the presence of the lysosomal enzyme cathepsin B1. Compound 3, selected for in vivo experiments, was very active against P388, P388/ADM leukaemia, and Meth A fibrosarcoma cell lines, scoring T/C% values comparable with the camptothecin derivative CPT-11. Pharmacokinetic studies indicated that 3 acts as a reservoir of 10-amino-7-ethylcamptothecin, as the mean residence time (MRT) is about 3-fold higher than that of the free drug.

Alleviation of side effects induced by irinotecan hydrochloride (CPT-11) in rats by intravenous infusion.

PURPOSE: Irinotecan hydrochloride (CPT-11) is a potent topoisomerase I inhibitor and is established and used widely as an antitumor agent. However, it sometimes causes severe side effects such as myelosuppression and diarrhea. These dose-limiting toxicities prevent the adoption of CPT-11 in aggressive chemotherapy. Thus we sought to determine in a rat model whether extending the period of infusion of CPT-11 would ameliorate the adverse reactions. METHODS: CPT-11 was administered intravenously (i.v.) to rats at a dose of 60 mg/kg per day for four consecutive days as a bolus injection or as 3-, 8- or 24-h infusions, and then blood cell counts and the incidence of acute and delayed-onset diarrhea were monitored. RESULTS: Serious acute and delayed-onset diarrhea and marked decreases in the number of neutrophils and lymphocytes were observed in the bolus injection group. These symptoms were alleviated in the infusion groups with the degree of alleviation dependent on infusion time. In the bolus injection group, mucosal impairment of the cecal epithelium including wall thickening, edema, a decrease in the number and size of crypts, and the formation of a pseudomembrane-like substance was observed, whereas these changes were less severe in the infusion groups. Areas under the plasma concentration-time curves (AUCpla) of CPT-11 and its metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38), differed little among the bolus injection group, and the 3-h and 8-h infusion groups. However, the AUCpla values of CPT-11 and SN-38 were significantly decreased and increased, respectively, in the 24-h infusion group. The maximum plasma concentrations (Cmax) of CPT-11 decreased with increasing infusion time, but those of SN-38 did not. CONCLUSIONS: It was confirmed that the side effects of CPT-11 were alleviated by extending the infusion time. The pharmacokinetic parameters suggested that the Cmax of CPT-11 is closely related to the incidence and severity of adverse reactions such as myelosuppression and acute and delayed-onset diarrhea.