Active loading liposomal irinotecan hydrochloride:Preparation,in vitro and in vivo evaluation

The aim of the present study was to investigate the effect of various transmembrane ammonium salt gradients and different lipid composition on the loading efficiency of liposomal formulations of irinotecan hydrochloride(CPT-11),their behavior in vivo and cytotoxicity.Among ammonium salts studied,ammonium sulfate was successfully used to load CPT-11 into liposomes with the highest encapsulation efficiency.Subsequently,liposomal CPT-11 with different lipid composition was prepared by ammonium sulfate gradient method.CPT-11 can be loaded to a level over 90%into liposomes composed of soybean phospholipids/cholesterol(SPC-L)or hydrogenated natural soybean phospholipids/cholesterol(HSPC-L).In vitro release profiles were also investigated,indicating that HSPC-L had a lower release than that in SPC-L.In vivo,encapsulation of CPT-11 in both liposomal formulations showed higher area under the curve(AUC),a lower rate of clearance(CL)and smaller volume of distribution for CPT-11 than those of irinotecan hydrochloride solution(CPT-11-S).However,CL and AUC of 7-ethyl-10-hydroxycamptothecin(SN-38)were moderately improved in HSPC-L group.Based on the results of comparative pharmacokinetics of liposomal CPT-11 with different lipid composition,the in vitro cytotoxicity of HSPC-L was evaluated with human tumor cell.The result indicated that liposomal CPT-11 showed a great enhancement in vitro cytotoxicity.The results suggested that entrapment of CPT-11 in liposomes especially in those with high phase-transition temperature lipid by ammonium sulfate gradient would be a promising formulation with a better in vivo behavior.

Phase 1/2 study of concurrent chemoradiotherapy with weekly irinotecan hydrochloride for advanced/recurrence uterine cancer:A multi-institutional study of Kansai Clinical Oncology Group

Objective:Concurrent chemoradiotherapy using cisplatin was thought to be standard treatment for squamous cell carcinoma of cervix,but it had not been effective for adenocarcinoma.Concurrent chemoradiotherapy using irinotecan hydrochloride(CPT-11)had been effective for colorectal cancer,thus,we chose CPT-11 as a candidate for gynecologic adenocarcinoma.To evaluate the maximum tolerated dose(MTD)of weekly CPT-11 with external pelvic radiotherapy,a phase 1/2 study was conducted according to modified Fibonacci method.Methods:Eligible patients were advanced uterine cancer with measurable diseases[performance score(PS):0-2].Study period was from August 1 st,2002 to December 31 st,2008.The starting dose level(DL)of CPT-11 was 30 mg/m2(DL1)given weekly for 4 weeks.Subsequently,dose escalation was scheduled in 10 mg/m2 increments to 60 mg/m^2(DL4).The fixed radiotherapy consisted of whole pelvic 1.8 Gy/d,once a day in weekday for five weeks and it amounted to 45 Gy(25 fractions)in total.Results:Seventeen patients were enrolled.As for toxicities,one(1/17:5.9%)grade(G)4 neutropenia lasting 7 days had been seen in DL4.G2 diarrhea was identified in 35.3%(6/17)of the patients,and 11.8%(2/17)G3 diarrhea was observed in DL3 and DL4.Thus,the MTD of CPT-11 was defined as dose of 60 mg/m^2.The recommended dose was decided as 50 mg/m^2.The response rate was 88.2%[9 complete response(CR),3 partial response(PR),3 stable disease(SD),2 not evaluable(NE)].Disease control rate at 1 month after treatment completion was 100%but distant metastases were found in 24%(4/17)in longer outcome.Conclusions:MTD was 60 mg/m^2 and recommended dose was set as 50 mg/m2.This concurrent chemoradiation using weekly CPT-11 was feasible at 50 mg/m^2,and it might be effective even in adenocarcinoma of the uterus.

Dexamethasone Regulates Differential Expression of Carboxylesterase 1 and Carboxylesterase 2 through Activation of Nuclear Receptors

Carboxylesterases (CESs) play important roles in the metabolism of endogenous and foreign compounds in physiological and pharmacological responses. The aim of this study was to investigate the effect of dexamethasone at different doses on the expression of CES1 and CES2. Imidapril and irinotecan hydrochloride (CPT-11) were used as special substrates for CES1 and CES2, respectively. Rat hepatocytes were cultured and treated with different concentrations of dexamethasone. The hydrolytic activity of CES1 and CES2 was tested by incubation experiment and their expression was quantitated by real-time PCR. A pharmacokinetic study was conducted in SD rats to further evaluate the effect of dexamethasone on CESs activity in vivo. Western blotting was performed to investigate the regulatory mechanism related to pregnane X receptor (PXR) and glucocorticoid receptor (GR). The results showed that exposure of cultured rat hepatocytes to nanomolar dexamethasone inhibited the imidapril hydrolase activity, which was slightly elevated by micromolar dexamethasone. For CES2, CPT-11 hydrolase activity was induced only when dexamethasone reached micromolar levels. The real-time PCR demonstrated that CES1 mRNA was markedly decreased by nanomolar dexamethasone and increased by micromolar dexamethasone, whereas CES2 mRNA was significantly increased by micromolar dexamethasone. The results of a complementary animal study showed that the concurrent administration of dexamethasone significantly increased the plasma concentration of the metabolite of imidapril while the ratio of CPT-11 to its metabolite SN-38 was significantly decreased. PXR protein was gradually increased by serial concentrations of dexamethasone. However, only nanomolar dexamethasone elevated the level of GR protein. The different concentrations of dexamethasone required suggested that suppression of CES1 may be mediated by GR whereas the induction of CES2 may result from the role of PXR. It was concluded that dexamethasone at different concentrations can differentially regulate CES1 and CES2.