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Cisplatin nanocapsules represent a novel lipid formulation of the anticancer drug cis-diamminedichloridoplatinum(II) (cisplatin), characterized by an unprecedented cisplatin-to-lipid molar ratio, and exhibiting strongly increased in-vitro cytotoxicity compared with the free drug. In this study, antitumor efficacy and biodistribution of PEGylated cisplatin nanocapsules were compared with those of the free drug in a mouse tumor model. Nude mice bearing human ovarian carcinoma OVCAR-3 xenografts were treated twice with a 1-week interval by intravenous administration of cisplatin nanocapsules or cisplatin in solution, and the growth inhibitory effects were determined by measurement of tumor volumes. At a dose of 3 mg cisplatin/kg, corresponding to the maximum tolerated dose of cisplatin nanocapsules, cisplatin nanocapsules and cisplatin in solution exhibited similar therapeutic effectiveness, reducing tumor growth by 90% at day 20 after first injection. The platinum biodistribution was assayed by analyzing plasma and tissues for total platinum content by nonflame atomic absorption spectroscopy. Plasma and tumor concentrations of platinum were similar for both formulations. During the first hour after injection of cisplatin nanocapsules, the platinum content of the kidney was 40% less than that after administering the free drug. Platinum from nanocapsules showed rapid and 4.5-fold higher accumulation in the liver compared with free cisplatin, and, at a slower rate, accumulation to a high concentration in the spleen. We conclude that the formulation of cisplatin nanocapsules inhibits the growth of OVCAR-3 xenografts in nude mice, albeit to a similar extent as free cisplatin. The results suggest that the antitumor efficacy of the nanocapsules could be improved by preventing rapid clearance from circulation.

In preclinical studies, BNP7787 (disodium 2,2'-dithio-bis-ethane sulphonate), the disulphide form of mesna, has demonstrated selective protection against cisplatin-induced nephrotoxicity due to conversion into mesna inactivating toxic platinum species. Mesna (sodium 2-mercapto ethane sulphonate), however, can affect the antitumour activity of cisplatin, while BNP7787 does not interfere with the antitumour activity. To understand the difference in interference with cisplatin-induced antitumour activity between BNP7787 and mesna as well to characterise the selective nephroprotection by BNP7787, the pharmacokinetics of BNP7787 and mesna, each given i.v. 1000 mg x kg(-1), were determined in plasma, kidney, liver, red blood cells (RBC), skeletal muscle and tumour of Fischer rats bearing subcutaneously implanted WARD colon tumours. The following results were obtained: (1). high concentrations of BNP7787 and mesna were observed in the plasma and kidney after administration of BNP7787 or mesna, except for mesna in plasma after BNP7787 administration; (2). in all other sampled compartments, the AUC values of both compounds were at least 5.5-fold lower than the corresponding values in kidney; (3). the AUC of mesna in plasma after mesna administration was comparable to the AUC of mesna in kidney after a dose of BNP7787 that can completely prevent cisplatin-induced nephrotoxicity in rats; (4). the AUC of mesna in plasma was five-fold higher relative to the AUC of mesna following BNP7787 administration (P<0.01). In conclusion, the five-fold higher AUC of mesna in plasma after mesna administration and the fact that mesna is more reactive with (hydrated) cisplatin than its disulphide form BNP7787 represent a plausible explanation as to why mesna administration can reduce the antitumour activity of cisplatin. After BNP7787 administration, the distribution of BNP7787 and mesna was restricted to the kidney, which confirmed the selective protection of the kidney by BNP7787.

DX-8951f or exatecan mesylate ((1S,9S)-1-amino-9-ethyl-5-fluoro-2,3-dihydro-9-hydroxy-4-methyl-1H,12H-benzo[de]pyrano[3',4':6,7]indolizino[1,2-b]quinoline-10-13(9H,15H)-dione methanesulfonate dihydrate), is a new water-soluble derivative of camptothecin. We determined the activity of DX-8951f in experimental human colon cancer and ovarian cancer, being tumor types sensitive to camptothecins. With the use of the MTT assay, DX-8951f was more potent than SN-38 in four out of five human colon cancer cell lines and three out of four human ovarian cancer cell lines (P<0.05). DX-8951f was considerably more potent than topotecan in all cell lines tested (P<0.05). Prolonged exposure to DX-8951f resulted in a greater increase in inhibition of cell proliferation as compared to that obtained with SN-38 or topotecan (P<0.05). Overexpression of Pgp, MRP1, and LRP did not affect the in vitro activity of DX-8951f. DX-8951f administered daily x 5 or weekly x 2 resulted in growth inhibition <50% in two human colon cancer xenografts grown s.c. in nude mice. In three human ovarian cancer xenografts, however, >50% growth inhibition was observed at both schedules. In the OVCAR-3 human ovarian cancer model, DX-8951f showed considerably greater activity than topotecan (P<0.01). DX-8951f combined with cisplatin or paclitaxel did not indicate the presence of a pharmacological interaction. In OVCAR-3 xenografts the combination was clearly more effective than DX-8951f alone, as the number of complete remissions increased substantially. In conclusion, this study shows that DX-8951f is highly potent in vitro and highly effective in experimental human ovarian cancer in vivo. Prolonged exposure to DX-8951f in vitro greatly increased the antiproliferative effects, which may be a rationale for testing a continuous infusion schedule in the clinic. Addition of cisplatin or paclitaxel improved the in vivo antitumor effects of DX-8951f.

BNP7787 (2',2'-dithio-bis-ethane sulphonate sodium), a water-soluble disulphide, is chemically and mechanistically different from other sulphur-containing chemoprotective agents. Presently, BNP7787 is under investigation for its protective properties with regard to the side-effects of platinum compounds. In this study, we evaluated BNP7787, mesna and amifostine for their effects on the antitumour activity of platinum compounds. Continuous exposure to BNP7787 did not affect the antiproliferative effects of cisplatin or carboplatin, but the efficacy of both compounds was reduced in the presence of mesna in vitro in two human ovarian cancer cell lines. BNP7787 or amifostine combined with cisplatin or carboplatin given in standard schedules for the treatment of nude mice bearing well-established OVCAR-3 xenografts did not interfere with platinum-induced inhibition of tumour growth. Of interest, BNP7787 or amifostine co-administered with carboplatin was significantly more effective than carboplatin alone (P<0.01). In the presence of amifostine, doses of cisplatin and carboplatin could be safely increased by factors of 1.6 and 1.5, respectively. Unlike in a previous study of BNP7787 in tumour-bearing rats, BNP7787 did not protect against additional weight loss following treatment with higher doses of cisplatin in OVCAR-3-bearing mice. Pharmacokinetics of (mixed) disulphides including BNP7787 and extractable mesna in deproteinised plasma revealed a rapid disappearance of BNP7787 and an AUC(5-60) value of mesna 9-fold lower than that calculated after an equivalent dose of mesna by weight. We can conclude that BNP7787 does not interfere with the antitumour activity of platinum compounds in vitro and in vivo. Clinical trials are underway to evaluate the protection of normal tissues by BNP7787 when combined with cisplatin.

Objectives: We have established a panel of 15 human ovarian cancer xenografts grown subcutaneously in the flank of the nude mouse. Similar to the clinic, the xenografts show differences in histological subtype and volume doubling time. We determined whether the panel is useful for drug screening by testing the sensitivity to six conventional anticancer agents. In addition, we investigated whether the glutathione detoxification system affects sensitivity to cisplatin and cyclophosphamide, major drugs in the treatment of ovarian cancer., Methods: Mice bearing well-established tumors were treated at maximum tolerated doses as defined by a reversible weight loss up to 15% of their initial weight: cisplatin 5 mg/kg iv weekly x2, cyclophosphamide 150 mg/kg ip 2-weekly x2, doxorubicin 8 mg/kg iv weekly x2, hexamethylmelamine ip 150 mg/kg every other day x4, methotrexate ip 150 mg/kg weekly x2, and 5-fluorouracil 60 mg/kg ip weekly x4. Glutathione levels and the activities of three different glutathione-dependent enzymes were measured in untreated xenograft tissues., Results: Growth inhibition >75% was reached for cisplatin in 40%, for cyclophosphamide in 27%, and for doxorubicin in 20% of the xenografts. Methotrexate and 5-fluorouracil did not induce growth inhibition of importance. Hexamethylmelamine showed >75% growth inhibition in 53% of the xenografts, which may have been caused by the favorable metabolism of the drug in mice when compared with that in patients. Glutathione levels varied 3.6-fold in the xenografts and did not show a relation with sensitivity to cisplatin, cyclophosphamide, or doxorubicin. No relation was found between the activities of glutathione S-transferase and glutathione peroxidase and the sensitivities to the three anticancer agents. Glutathione reductase activity, however, showed a weak, inverse relation with the efficacy of cisplatin and cyclophosphamide (r values of -0.55 and -0.58, respectively)., Conclusions: The sensitivity to the six anticancer agents of our panel of 15 human ovarian cancer xenografts reflects the response rates known for similar drugs in ovarian cancer patients. In that respect, the panel may be useful for drug screening as well as studies on the relevance of drug resistance features in vivo. The various components of the glutathione detoxification system did not predict for primary drug resistance which confirms clinical data in ovarian cancer., (Copyright 2000 Academic Press.)

The prodrug N-[4-(daunorubicin-N-carbonyl-oxymethyl)phenyl] O-beta-glucuronyl carbamate (DNR-GA3) was synthesized for specific activation by human beta-glucuronidase, released in necrotic areas of tumour lesions. In vitro, DNR-GA3 was 18 times less toxic than daunorubicin (DNR) and the prodrug was completely activated to the parent drug by human beta-glucuronidase. The maximum tolerated dose of DNR-GA3 in nude mice bearing s.c. human ovarian cancer xenografts was 6-10 times higher than that of DNR. The prodrug was cleared more rapidly from the circulation (elimination t1/2 = 20 min) than the parent drug (elimination t1/2 = 720 min). The anti-tumour effects of DNR-GA3 and DNR were investigated in four different human ovarian cancer xenografts OVCAR-3, FMa, A2780 and MRI-H-207 at a mean tumour size between 100 and 200 mm3. In three out of four of these tumour lines, the prodrug given i.v. at the maximum tolerated dose ranging from 150 to 250 mg kg(-1) resulted in a maximum tumour growth inhibition from 82% to 95%. The standard treatment with DNR at a dose of 8 mg kg(-1) given i.v. weekly x 2 resulted only in a maximum tumour growth inhibition from 40% to 47%. Tumour line FMa did not respond to DNR, nor to DNR-GA3. Treatment with DNR-GA3 was also given to mice with larger tumours that would contain more necrosis (mean size 300-950 mm3). The specific growth delay by DNR-GA3 was extended from 2.1 to 4.4 in OVCAR-3 xenografts and from 4.4 to 6.0 in MRI-H-207 xenografts. Our data indicate that DNR-GA3 is more effective than DNR and may be especially of use for treatment of tumours with areas of necrosis.

We have established ten transplantable human soft-tissue sarcoma (STS) xenografts grown as subcutaneous tumours in the nude mouse. Nine xenografts originated from patients that needed chemotherapy in the course of their disease. The xenografts were tested for their sensitivity to maximum tolerated doses of five anti-cancer agents. Growth of treated tumours was expressed as a percentage of control tumour growth and a growth inhibition > 75% was measured for doxorubicin in 20% of the STS xenografts, for cyclophosphamide in 30%, for ifosfamide in 20%, for vincristine in 20%, whereas etoposide was not effective in the STS xenografts. In three out of ten STS xenografts MDR1 mRNA was detectable, but this was not related to the resistance against doxorubicin, vincristine or etoposide. Topoisomerase IIalpha mRNA expression levels did not reflect sensitivity to doxorubicin or etoposide. In all STS tissues, however, these levels were lower than topoisomerase IIalpha mRNA in a drug-sensitive human ovarian cancer xenograft. Glutathione concentrations and the activities of glutathione S-transferase, glutathione peroxidase and glutathione reductase were not related to resistance against the alkylating agents or doxorubicin. Of interest, in all STS tissues, glutathione S-transferase pi was the predominant isoenzyme present. In conclusion, chemosensitivity of the STS xenografts reflects clinical response rates in phase II trials on the same compounds in adult STS patients. Relatively low levels of topoisomerase IIalpha mRNA may partly account for intrinsic resistance against, for example, doxorubicin. Additional factors must contribute to moderate responsiveness to alkylating agents.

CPT-11, a semi-synthetic derivative of camptothecin, was investigated for its activity in panels of 15 human ovarian-cancer lines and 10 human soft-tissue sarcoma lines grown s.c. in nude mice. Various factors were analyzed that may be of influence on the extent of tumor-growth inhibition induced by CPT-11. At equitoxic doses, CPT-11 was more effective in the daily x5 schedule than the weekly x2 schedule, although a 2-fold higher dose was administered in the weekly x2 schedule. Since i.p. and i.v. injections were similarly effective, the selected treatment schedule was 20 mg/kg i.p. daily x5, starting when tumors measured approximately 150 mm3. Growth inhibition of > or = 75% was obtained in 8/15 human ovarian-cancer lines and in 6/10 human soft-tissue sarcoma lines. A weak correlation was found between topoisomerase-I mRNA in xenograft tissues and sensitivity to CPT-11. Relative topoisomerase-I expression was highest in MRI-H-207 and WLS-160 xenografts, in which CPT-11 was able to induce cures of all tumors. The high efficacy in the 2 panels of human tumor lines suggests over-prediction of its potential clinical activity in these tumor types. The difference in efficacy of CPT-11 between species may be related to the metabolism of the drug, since CPT-11 is converted more efficiently into SN-38 in mice. In addition, mice may be less sensitive to SN-38-induced side-effects. On the basis of the preclinical data, frequent administration of lower doses of CPT-11 should be considered in order to increase response rates in the clinic.

The therapeutic efficacy of gemcitabine, a new nucleoside analogue, was assessed in a variety of well-established human soft tissue sarcoma and ovarian cancer xenografts grown s.c. in nude mice. Tumour lines selected had different histological subtypes, growth rates and sensitivities to conventional cytostatic agents. The three different doses and schedules designed on the basis of a mean weight loss between 5% and 15% were i.p. injections of daily 3.5 mg kg-1 x 4, every 3 days 120 mg kg-1 x 4, and weekly 240 mg kg-1 x 2, which ultimately resulted in 19%, 10% and 4% toxic deaths, respectively. The weekly schedule induced > or = 50% growth inhibition in 2/4 soft tissue sarcoma and 4/6 ovarian cancer lines, while in three ovarian cancer lines > or = 75% growth inhibition was obtained. The anti-tumour effects of gemcitabine appeared to be similar or even better than previous data with conventional drugs tested in the same tumour lines. In comparison with the every 3 days schedule, the weekly and the daily schedule were less effective in 5/7 and 3/3 tumour lines (P < 0.001), respectively. In another experiment in three human tumour lines selected for their differential sensitivity to gemcitabine, weekly injections of 240 mg kg-1 x 6 did not result in a significant increase in the percentages of growth inhibition when compared to lower doses of 120 mg kg-1 or 60 mg kg-1 in the same schedule. However, the 240 mg kg-1 weekly x 6 schedule showed superior effects in 2/3 tumour lines in comparison with the same dose given every 2 weeks x 3 (P < 0.05). The preclinical activity of gemcitabine suggests that the drug can induce responses in soft tissue sarcoma and ovarian cancer patients. Our results further indicate that clinical trials of gemcitabine in solid tumour types should be designed on the basis of a schedule rather than a dose dependence.

Background: The new cytostatic agent taxol has clearly demonstrated its effectiveness in ovarian cancer patients. The synthesis of drugs related to taxol could overcome its limited natural supply and may have additional benefits, such as greater efficacy or better solubility. Taxotere (RP 56976, NSC 628503) is such a compound. We investigated the drug for its antitumor activity in human ovarian cancer xenografts., Materials and Methods: Five human ovarian cancer lines were selected with respect to differences in histological sub-types, growth rates and chemosensitivity to conventional cytostatic agents. Tumors were implanted as fragments s.c. into both flanks of female nude mice (Hsd: athymic nude-nu). Treatment was started in groups of 5-8 mice at the time mean tumor volume measured 50-150 mm3. Taxotere was injected i.v. weekly x 2. Drug efficacy was expressed as the maximum percentage of growth inhibition of treated tumors as compared to control tumors., Results: At the maximum tolerated dose of 15-20 mg/kg for weekly i.v. x 2 injections, taxotere induced a mean weight loss of 10%-15% of the initial weight within 2 weeks after the first injection. The maximum percentage of growth inhibition obtained was > or = 50% in 4/5 lines and > or = 90% in 3/5 lines. In 2 lines, taxotere appeared more effective than cisplatin, cyclophosphamide or doxorubicin, drugs studied previously at maximum tolerated doses in the same tumor lines., Conclusion: Our findings in human ovarian cancer xenografts hold promise for the efficacy of taxotere in this type of disease in the clinic.

N-l-leucyl-doxorubicin and vinblastine-isoleucinate can be considered as relatively non-toxic prodrugs from doxorubicin and vinblastine, respectively. A comparative analysis was carried out of the anti-tumour activity of the four compounds as well as vintriptol in four human ovarian cancer xenografts different in histology, growth rate and chemosensitivity. Injections were given i.v. weekly twice into mice bearing well-established s.c. tumours. At equitoxic doses, the amount of drug administered for N-l-leucyl-doxorubicin and vinblastine-isoleucinate was respectively 3-fold and 2-fold higher than the doses of the parent compound. N-l-leucyl-doxorubicin induced a growth inhibition > 50% in three out of four human ovarian cancer lines. The anti-tumour effects obtained were significantly better (P < 0.01) than in the case of doxorubicin. Vinblastine-isoleucinate studied in two of these lines could induce a growth inhibition of > 50%. This prodrug appeared slightly less effective than vinblastine. Insignificant growth inhibition (< 50%) was obtained by vintriptol.

Eight human ovarian cancer lines grown in nude mice were used to compare the activity of doxorubicin, epirubicin, mitoxantrone and menogaril. The tumour lines were different in histological subtype, tumour doubling time and sensitivity to doxorubicin. The compounds were administered intravenously at the maximum tolerated dose twice with one week in between when tumours measured 50-150 mm3. Growth inhibition greater than 50% was obtained for doxorubicin in 8/8, for epirubicin in 4/8, for mitoxantrone in 5/8 and for menogaril in 2/8 tumour lines. In MRI-H-207, doxorubicin was the only drug able to induce complete remission. Compared with doxorubicin, mitoxantrone and menogaril were given in proportionally higher doses than those administered to patients, but did not result in superior antitumour activity.

A series of eight human ovarian cancer lines grown in nude mice were used to compare the activity of hexamethylmelamine (HMM) and N2,N4,N6-trihydroxy methyl-N2,N4,N6-trimethylmelamine (trimelamol). The tumor lines differed in histological subtype and growth rate. The drugs were administered i.p. at the maximum tolerated dose at alternate days. Differences in volume of treated and control tumors were endpoints of the study. The tumor lines varied widely in sensitivity to HMM and in four lines a T/C% below 25% was achieved. Trimelamol appeared to be more active than HMM and achieved a T/C below 25% in seven tumor lines. Thus far, the drug has demonstrated significant activity in a phase I trial in ovarian cancer patients. Comparative clinical studies of HMM vs trimelamol have not yet been performed.