Improvement of intraperitoneal chemotherapy for rat ovarian cancer using cisplatin-containing microspheres

Antitumor effectiveness and toxicity of cisplatin-loaded long-circulating and pH-sensitive liposomes against Ehrlich ascitic tumor

Cisplatin (CDDP) is one of the most active cytotoxic agents commonly used in the treatment of peritoneal carcinomatosis. The disadvantages of its clinical use are systemic side-effects, such as nephrotoxicity and myelotoxicity. Long-circulating and pH-sensitive liposomes containing CDDP (SpHL-CDDP) were developed by our research group aiming to promote the release of CDDP near the tumor as well as decreasing toxicity. The aim of this study was to evaluate the antitumor efficacy and toxicity of SpHL-CDDP after intraperitoneal administration in initial or disseminated tumor-bearing mice, at a dose of 12 mg/kg. The survival was monitored and blood samples were collected for biochemical and hematological analysis. Kidneys, liver and spleen were removed for histopathological examination. Tumor cells were evaluated for cellular viability and cell cycle. The survival of animals treated with SpHL-CDDP was higher than those treated with free CDDP. The cell death caused by treatment with SpHL-CDDP occurred through induction of apoptosis, with a cell cycle arrest at the G0/G1 phase. The treatment of mice presenting initial cancer with both formulations provoked a suppression of granulocytes. Mice treated with free CDDP also showed a decrease in platelet count, which suggests a high myelotoxicity. In an advanced cancer model, SpHL-CDDP treatment allowed an improvement of the immune response. Mice affected by cancer at an early stage and treated with free CDDP or SpHL-CDDP showed a lower urea/creatinine index compared with the saline control group. These findings indicate that both treatments were able to reduce the renal damage caused by peritoneal carcinomatosis. Microscopic analysis of kidneys from mice treated with SpHL-CDDP showed a discrete morphological alteration, while tubular necrosis was observed for free CDDP-treated mice. Concerning hepatotoxicity, no alteration in clinical chemistry parameters was observed. These findings reveal that SpHL-CDDP can improve the antitumor efficacy and decrease renal and bone marrow toxicity.

Relation between dissolution profiles and toxicity of cisplatin-loaded microspheres

The aim of this study is to evaluate and compare the dissolution profiles of cisplatin-loaded microspheres (CDDP-MS) in vitro and in vivo, and to determine the relationship between the dissolution profiles in vitro and systemic toxicity. For this purpose, three types of CDDP-MS that release the CDDP for 1, 2 and 5 weeks without a large amount of initial release in phosphate buffered saline (pH 7.4) were prepared. The dissolution profiles of these formulations in vivo were well correlated with in vitro studies, and resulted in well-controlled plasma platinum concentration. The systemic toxicity of the CDDP-MS and CDDP dissolved in saline (CDDP-SOL) were assessed by intraperitoneal administration in mice. The maximal tolerable dose (MTD) of CDDP-SOL was 13.4 mg/kg, whereas the CDDP-MS of 1, 2 and 5-week types were 34.6, 44.2, 62.6 mg/kg, respectively. The MTD of CDDP increased proportionally when 50% of CDDP had been released from MS in vitro (MTD (mg/kg)=5.22 x T(50(day)) + 13.2, R(2)=0.9935). We demonstrate that the systemic toxicity of CDDP-MS can be predicted by evaluation of the dissolution rate in vitro since in vivo dissolution was correlated with the in vitro.

Antitumor effect of the idiotypic cascade induced by an antibody encapsulated in poly(d,l-lactide-co-glycolide) microspheres

A major difficulty encountered during development of antibody vaccines is their weak immunogenicity. In this study, a monoclonal antibody CS20.5 to human breast cancer antigen CA15.3 was coencapsulated in poly(d,l-lactide-co-glycolide) microspheres with monophosphoryl lipid A. The antitumor effect of this formulation was investigated in a murine model. The induced Ab2 biologically mimics antigen as it competed with CA15.3 for the same idiotope on Ab1. Ab3 induction was also observed. After five sequential administrations of encapsulated antibody, mice showed statistically significant tumor regression. These results indicate that this formulation may serve as a potential treatment for breast cancer.

Cisplatin-incorporated polymeric micelles eliminate nephrotoxicity, while maintaining antitumor activity

cis-Diamminedichloroplatinum (II) (cisplatin, CDDP), a potent anticancer agent, was bound to the aspartic acid residues of poly(ethylene glycol)-poly(aspartic acid) (PEG-P(ASP)) block copolymer by ligand substitution reaction at the platinum atom of CDDP. The polymeric drug thus obtained was observed to form a micelle structure in aqueous medium, showing excellent water solubility. In the present study, in vitro and in vivo antitumor activity against several human tumor cell lines, toxicity and pharmacokinetic characteristics in rodents of CDDP-incorporated polymeric micelles (CDDP / m) were evaluated in comparison with those of CDDP. In vitro, CDDP / m exhibited 10 - 17% of the cytotoxicity of CDDP against human tumor cell lines. CDDP / m given by intravenous (i.v.) injection yielded higher and more sustained serum levels than CDDP. In vivo CDDP / m treatment resulted in higher and more sustained levels in tumor tissue than CDDP, and showed similar antitumor activity to CDDP against MKN 45 human gastric cancer xenograft. CDDP / m treatment caused much less renal damage than CDDP. These results indicate that CDDP / m treatment can reduce CDDP-induced nephrotoxicity without compromising the anticancer cytotoxicity of CDDP.

Antitumor effect of cisplatin incorporated into polylactic acid microcapsules

Cisplatin containing microcapsules (CDDP-MC) were prepared by encapsulating cisplatin suspended in a dispersing agent in a copolymer (lactic acid) matrix using an in water drying method. Cisplatin release from the microcapsules was controlled by the addition of albumin. The CDDP-MC were relatively stable in storage, and there was only minimal initial release of the cisplatin from the microcapsules. The antitumor effects of this sustained release dosage form of cisplatin were evaluated in vitro and in vivo in mice. Mice were given an intraperitoneal (i.p.) injection of CDDP-MC 24 h after inoculation with tumor cells. The CDDP-MC were effective against Ehrlich ascites tumors and showed reduced acute toxicity compared with standard cisplatin solution. Due to the small initial release of the cisplatin from the microcapsules, however, the antitumor effect of the CDDP-MC was weaker than that of cisplatin solution. Conventional sustained release preparations have been reported to have large particle sizes and demonstrate large releases of cisplatin from microcapsules. They have been considered more effective than cisplatin solution because of the large initial release of cisplatin from the microcapsules and the maintenance of drug levels. The antitumor effect of our slow-release formulation of cisplatin was evaluated by administration of CDDP-MC 1, 4, and 7 days before i.p. implantation of tumor cells. The survival time of the tumor-bearing mice was prolonged in the CDDP-MC group, but not in the group treated with cisplatin solution. By using this modified formulation of cisplatin, the toxicity of the drug can be reduced, and effective concentrations of the drug can be maintained locally for prolonged periods of time.

Design and testing of a new cisplatin form using a base material by combining poly-D,L-lactic acid and polyethylene glycol acid against peritoneal metastasis

Microspheres containing cisplatin (CDDP) embedded in poly-d,l-lactic acid (PLA) and polyethylene glycol acid (CDDP-PPMS) were developed to improve treatment of malignant effusions. In vitro studies demonstrated that CDDP was released continuously for more than 4 weeks from CDDP-PPMS without initial burst. CDDP-PPMS was compared with CDDP aqueous solution (CDDP-SOL) by i.p. administration in rats for 1) tissue distribution, 2) toxicity and 3) therapeutic effects against Yoshida sarcoma. We found that the CDDP concentration in the omentum was maintained at a higher level than in the CDDP-SOL group, while the particles of CDDP-PPMS were observed in the stomata of the omentum by electron microscopy. Concentrations of CDDP in the lung, liver, kidney and blood were lower in the CDDP-PPMS group than in the CDDP-SOL group. All rats given CDDP-PPMS containing < or = 28 mg/kg were alive, whereas in the CDDP-SOL group, all rats given > or = 16 mg/kg died from side effects. The LD50 of CDDP-PPMS and CDDP-SOL were 32.8 and 14.8 mg/kg, respectively. The survival of rats with peritoneal metastasis was better in the CDDP-PPMS group than in the CDDP-SOL group.