Tiziana Servidei

The novel trinuclear platinum complex BBR3464 induces a cellular response different from cisplatin

BBR3464 is a new platinum-based drug non cross-resistant with cisplatin. To characterise the cellular basis of BBR3464 cytotoxicity as opposed to cisplatin, we performed a comparative study of the two drugs in cisplatin-resistant neuroblastoma and astrocytoma cells. In both model systems, BBR3464 proved to be more potent than cisplatin and was able to overcome cisplatin resistance. The higher potency exhibited by BBR3464 correlated with an increased cellular platinum accumulation and DNA-adduct formation. At equitoxic doses, BBR3464 induced apoptosis to a lesser extent than cisplatin and failed to overcome the decreased susceptibility to cisplatin-induced apoptosis in cisplatin-resistant cells. Cell cycle analysis showed a dose-dependent G2/M arrest by BBR3464. In astrocytoma cells, cisplatin treatment resulted in the upregulation of p53, p21 and bax, while only p21 induction was observed after BBR3464 treatment. In cisplatin-resistant cells, the reduced sensitivity to cisplatin paralleled a resistance to the induction of p53/p21 pathway by cisplatin, while the same doses of BBR3464 induced p21 to a similar extent in the resistant cells as in the parental cells. In conclusion, BBR3464 induces a cellular response that is different from cisplatin, supporting the view that the two drugs act through different mechanisms. Our data indicate that BBR3464 may be a promising agent in the treatment of tumours unresponsive to cisplatin and with a non-functional p53.

In vitro and in vivo antitumor activity of the novel trinuclear platinum complex BBR 3464 in neuroblastoma

Abstract. Purpose: BBR 3464 is a promising new trinuclear platinum complex that has been shown to circumvent the resistance to cisplatin in a panel of tumor cell lines and xenografts with acquired or intrinsic resistance to cisplatin. The in vitro and in vivo antitumor activity of BBR 3464 was evaluated and compared with that of cisplatin in neuroblastoma. Methods: In in vitro studies, the short- and long-term cytotoxicities, cell cycle perturbations, the ability to induce apoptosis, the intracellular platinum accumulation and DNA platination were evaluated in three neuroblastoma cell lines exposed to appropriate drug concentrations for 1xa0h. In in vivo studies, BBR 3464 was administered i.v. at doses of 0.30 and 0.35xa0mg/kg three times at intervals of 4xa0days (q4d×3), and cisplatin was administered i.v. according to two different schedules (at 2 and 4xa0mg/kg three times at intervals of 4xa0days and at 6 and 12xa0mg/kg as single doses). Results: In a short-term growth inhibition assay, BBR 3464 was shown to be up to 100-fold more potent than cisplatin and it was even more potent in a clonogenic assay. The difference in the antitumor effect of BBR 3464 on the different cell lines was evident in both assays, while cisplatin exerted a comparable antitumor activity in all lines tested. Cell cycle analysis demonstrated a longer-lasting block in G2/M phase induced by BBR 3464 without the early S phase accumulation induced by cisplatin. The higher potency of BBR 3464 appeared to be unrelated to the induction of apoptosis, that was lower or at most comparable to cisplatin. Cellular platinum accumulation and platinum-DNA adduct formation following BBR 3464 exposure was higher than following cisplatin exposure. These differences may have resulted from a different mechanism of action and may explain the lack of cross-resistance with cisplatin. In xenografts of neuroblastoma, BBR 3464 was confirmed to be very potent as compared to cisplatin (MTD 0.35xa0mg/kg and 4xa0mg/kg for BBR 3464 and cisplatin, respectively). The efficacy of BBR 3464 was superior to that of cisplatin when both drugs were administered on a fractionated schedule (q4d×3), while BBR 3464 appeared equally active to 12xa0mg/kg cisplatin administered as a single dose. Conclusions: Our findings indicate that BBR 3464 has a definite antitumor effect in neuroblastoma lines and may be a candidate for early clinical trials in children with neuroblastoma.

CLINICAL PHARMACOKINETICS OF CARBOPLATIN IN CHILDREN

The present study was undertaken to evaluate in children the plasma pharmacokinetics of free carboplatin given at different doses and schedules and to evaluate the inter- and intrapatient variability and the possible influence of schedule on drug exposure. A total of 35 children (age range, 1–17 years) with malignant tumors were studied. All patients had normal renal function (creatinine clearance corrected for surface body area, above 70 ml min−1 m−2; range, 71–151 ml min−1 m−2) and none had renal involvement by malignancy. Carboplatin was given at the following doses and schedules: 175, 400, 500, and 600 mg/m2 given as a 1-h infusion; 1,200 mg/m2 divided into equal doses and infused over 1 h on 2 consecutive days; and 875 and 1,200 mg/m2 given as a 5-day continuous infusion. A total of 57 courses were studied. Carboplatin levels in plasma ultrafiltrate (UF) samples were measured both by high-performance liquid chromatography and by atomic absorption spectrophotometry. Following a 1-h infusion, carboplatin free plasma levels decayed biphasically; the disappearance half-lives, total body clearance, and apparent volume of distribution were similar for different doses. In children with normal renal function as defined by creatinemia and blood urea nitrogen (BUN) and creatinine clearance, we found at each dose studied a limited interpatient variability of the peak plasma concentration (Cmax) and the area under the concentration-time curve (AUC) and a linear correlation between the dose and both Cmax (r=0.95) and AUC (r=0.97). The mean value ± SD for the dose-normalized AUC was 13±2 min m2 l−1 (n=57). The administration schedule does not seem to influence drug exposure, since prolonged i.v. infusion or bolus administration of 1,200 mg/m2 achieved a similar AUC (13.78±2.90 and 15.05±1.44 mg ml−1 min, respectively). In the nine children studied during subsequent courses a limited interpatient variability was observed and no correlation (r=0.035) was found between AUC and subsequent courses by a multivariate analysis of dose, AUC, and course number. The pharmacokinetic parameters were similar to those previously reported in adults; however, a weak correlation (r=0.52,P=0.03) between carboplatin total body clearance and creatinine clearance varying within the normal range was observed. A dosing formula appears unnecessary in children with normal renal function since a generally well-predictable free carboplatin AUC is achieved following a given dose.

Cytotoxicity of paclitaxel and docetaxel in human neuroblastoma cell lines

Taxanes are an important new class of anticancer agents that inhibit cell division by the unique mechanism of increasing the rate of microtubule assembly and preventing microtubule depolymerisation. Using the colony inhibition assay, we compared the cytotoxicity of paclitaxel and docetaxel in three human neuroblastoma (NB) cell lines, SH-SY5Y, BE(2)M17 and CHP100. Different exposure times (3, 6, 12, 24, 48 and 72 h) and different concentrations ranging from 0.1 nM to 10 microM were tested. Both paclitaxel and docetaxel show antineoplastic activity in human NB cell lines. Taxanes antitumour activity varied among the different cell lines, CHP100 being the most sensitive and SH-SY5Y the least sensitive. Paclitaxel cytotoxicity appears schedule-dependent, with marked cell kill observed only for exposures of 24 h or longer. Docetaxel cytotoxicity was dependent upon prolonged exposure only in the SH-SY5Y cell line, while an exposure time of 3-6 h resulted in exponential cell kill in the other two cell lines. Docetaxel was more cytotoxic than paclitaxel with a mean ratio of (paclitaxel/docetaxel) IC50 values ranging from 2 to 11. For both taxanes, we observed good correlation between cytotoxic effect and percentage of cells blocked in G2/M phase. A cytotoxic effect occurred at concentrations comparable with those achieved in the plasma of patients treated with these agents in initial clinical trials. The full potential of prolonged infusion or repeated daily administrations of taxanes should be explored in clinical studies, and responses to taxanes in neuroblastoma should be assessed in paediatric phase II studies.

Antitumor activity and pharmacokinetics of oral gimatecan on pediatric cancer xenografts

PurposeThis study compared the antitumor activity and the pharmacological profile of gimatecan given orally and irinotecan (CPT-11) on pediatric tumor xenografts.Experimental designGimatecan was tested in two neuroblastoma cell lines (SK-N-DZ and SK-N-(BE)2c) and on TE-671 rhabdomyosarcoma cells using two different schedules. We characterized its pharmacokinetic profile in nude mice bearing human SK-N-DZ and TE-671 cell lines.ResultsGimatecan appears to have high plasma disposition. The drug was present in plasma almost completely as the intact lactone form and showed substantial activity in all tumor models. Prolonged daily treatment with low doses of gimatecan produced significant tumor regression in all tumor xenografts.ConclusionThe antitumor activity and the promising pharmacological profile indicate gimatecan as an excellent candidate for clinical treatment of pediatric tumors.

High-performance liquid chromatographic assay for cytosine arabinoside and uracil arabinoside in cerebrospinal fluid and plasma

This paper describes an isocratic, reversed-phase HPLC technique that is simple, sensitive and relatively rapid. Using this method we performed pharmacokinetic studies on cerebrospinal fluid (CSF) and plasma of patients underdoing both conventional and high-dose chemotherapy with ara-C

Cranial irradiation and cerebrospinal fluid levels of 6-mercaptopurine in children with acute leukemia

We measured 6-mercaptopurine levels in the cerebrospinal fluid and plasma of 15 children undergoing treatment for acute leukemia. Plasma and cerebrospinal fluid samples obtained by lumbar puncture were collected before, during, and after cranial irradiation in order to evaluate a possible change in blood-brain barrier permeability to orally administered 6-mercaptopurine. Considerable interpatient variability has been observed in both plasma and cerebrospinal fluid 6-mercaptopurine levels. No statistical differences in the 6-mercaptopurine cerebrospinal fluid levels under the three different conditions could be detected. Our data suggest that cranial irradiation does not significantly influence the cerebrospinal fluid levels.