The plasma and cerebrospinal fluid pharmacokinetics of the platinum analog satraplatin after intravenous administration in non-human primates.

BACKGROUND: Satraplatin is an orally bioavailable platinum analog with preclinical activity in cisplatin resistant models and clinical activity in adults with refractory cancers. The cerebrospinal fluid (CSF) penetration of cisplatin and carboplatin in non-human primates (NHP) is limited (3.7 and 2.6%, respectively). We evaluated the plasma and CSF pharmacokinetics (PK) of satraplatin after an intravenous (IV) dose in NHP. METHODS: Satraplatin (120 mg/m(2)) was administered as 1 h IV infusion in DMSO (5%) and normal saline to 5 NHP. Serial blood and CSF samples were obtained over 48 h. Plasma ultrafiltrate (UF) was immediately prepared by centrifugation. Platinum was quantified in plasma UF and CSF using a validated atomic absorption spectroscopy assay with lower limit of quantification (LLQ) of 0.025 µM in UF and 0.006 µM after concentration in CSF. Pharmacokinetic parameters were estimated using non-compartmental analyses. CSF penetration was calculated from the CSF AUC(0-48h) : plasma UF AUC(0-48h). RESULTS: Satraplatin was well tolerated. Median (range) PK parameters in plasma UF were: maximum concentration (C (max)) 8.3 µM (5.7-10.6), area under the curve (AUC(0-48h)) 29.2 µM h (22.6-33.2), clearance 0.36 l/h/kg (0.31-0.37), and t (1/2) 18.8 h (13.4-25). Satraplatin was detected in the CSF of all NHP. Median (range) PK parameters in CSF were: C (max) 0.07 µM (0.02-0.12), AUC(0-48h) 1.2 µM h (0.49-2.43). The median (range) CSF penetration of satraplatin was 4.3% (2.2-7.4). CONCLUSIONS: Satraplatin penetration into CSF is similar to that of carboplatin and cisplatin, despite its greater lipophilicity. The development of a phase I trial of satraplatin for refractory childhood solid tumors including brain tumors is in progress.

Extracellular fluid concentrations of cisplatin, carboplatin, and oxaliplatin in brain, muscle, and blood measured using microdialysis in nonhuman primates.

PURPOSE: Cisplatin, carboplatin, and oxaliplatin are chemically reactive anticancer drugs with modest activity in brain tumors. Previously, we have demonstrated that drug exposure in cerebrospinal fluid (CSF) for these platinum analogs is <5% of the plasma ultrafiltrate (UF) drug exposure in nonhuman primates. Microdialysis is a minimally invasive in vivo method for sampling small molecules in the blood and tissue extracellular fluid (ECF). The purpose of this study was to estimate the penetration of platinum analogs into the brain ECF. METHODS: We measured free concentrations of cisplatin, carboplatin, and oxaliplatin in ECF of brain, muscle, and blood of nonhuman primates using microdialysis and compared ECF platinum concentrations in blood and brain to plasma UF and CSF concentrations obtained using conventional sampling methods. RESULTS: For all three platinum analogs, AUC(0-4h) for microdialysis sampling from the vein was similar to standard plasma UF sampling. The median AUC(0-4h) ratio for vein to plasma UF was 1.1 (range, 0.9-1.4). The platinum analogs had limited distribution (<5%) to the CSF and brain ECF. CSF penetration predicts for the limited penetration of the platinum analogs into brain ECF, but concordance between CSF and brain ECF measurements was poor. CSF oxaliplatin concentrations (AUC(0-4h), 0.4-0.9 microM h) were substantially lower than brain ECF concentrations (AUC(0-4h), 2.0-8.6 microM h). CONCLUSIONS: The penetration of platinum analogs into CSF and brain is limited. The differences in the CNS penetrations among the three platinum analogs are not clinically significant. For cisplatin and carboplatin, CSF penetration appears to be a surrogate for brain extracellular free drug exposure.

Intracavitary chemotherapy (paclitaxel/carboplatin liquid crystalline cubic phases) for recurrent glioblastoma -- clinical observations.

Human malignant brain tumors have a poor prognosis in spite of surgery and radiation therapy. Cubic phases consist of curved biocontinuous lipid bilayers, separating two congruent networks of water channels. Used as a host for cytotoxic drugs, the gel-like matrix can easily be applied to the walls of a surgical resection cavity. For human glioblastoma recurrences, the feasibility, safety, and short-term effects of a surgical intracavitary application of paclitaxel and carboplatin encapsulated by liquid crystalline cubic phases are examined in a pilot study. A total of 12 patients with a recurrence of a glioblastoma multiforme underwent re-resection and received an intracavitary application of paclitaxel and carboplatin cubic phases in different dosages. Six of the patients received more than 15 mg paclitaxel and suffered from moderate to severe brain edema, while the remaining patients received only a total of 15 mg paclitaxel. In the latter group, brain edema was markedly reduced and dealt medically. Intracavitary chemotherapy in recurrent glioblastoma using cubic phases is feasible and safe, yet the clinical benefit remains to be examined in a clinical phase II study.

Local chemotherapy of F98 rat glioblastoma with paclitaxel and carboplatin embedded in liquid crystalline cubic phases.

Implanted drug carrier systems for retarded chemotherapy against gliomas are mainly based upon polymers containing nitrosoureas. The authors have developed an intracavitary carrier system of biodegradable liquid crystalline cubic phases encapsulating carboplatin and paclitaxel and studied it for release kinetics, antitumor activity, and survival prolongation. A total of 61 Fisher rats with F98 tumors were divided into six treatment groups at day 12 post-inoculation, receiving either no treatment, surgery with partial tumor resection, or partial resection with implantation of cubic phases containing either paclitaxel and carboplatin, paclitaxel alone, carboplatin alone, or no drug. Animals were killed for tumor size analysis at day 21 post-inoculation (n=28) or were included in survival studies (n=33). Additional 12 animals received a paclitaxel/carboplatin application and were killed at different time intervals (6 h, 24 h, 48 h, 5 d, 7 d, 10 d post-agent application) for in vivo diffusion studies. Animals from the paclitaxel/carboplatin group showed a significantly smaller tumor (mean 3.25 mm2+/-SD 1.79 mm2) than animals from the control group (15.30+/-5.86 mm2; P=0.0031), animals having received the empty matrix (11.62+/-6.66 mm2; P=0.0241), and animals after tumor resection without implantation (20.87+/-3.56 mm2; P

Plasma and cerebrospinal fluid pharmacokinetics of intravenous oxaliplatin, cisplatin, and carboplatin in nonhuman primates.

PURPOSE: Describe and compare the central nervous system pharmacology of the platinum analogues, cisplatin, carboplatin, and oxaliplatin and develop a pharmacokinetic model to distinguish the disposition of active drug from inert platinum species. EXPERIMENTAL DESIGN: Oxaliplatin (7 or 5 mg/kg), cisplatin (2 mg/kg), or carboplatin (10 mg/kg) was given i.v. Serial plasma and cerebrospinal fluid (CSF) samples were collected over 24 hours. Plasma ultrafiltrates were prepared immediately. Platinum concentrations were measured using atomic absorption spectrometry. Areas under the concentration x time curve were derived using the linear trapezoidal method. CSF penetration was defined as the CSF AUC(0-24)/plasma ultrafiltrate AUC(0-24) ratio. A four-compartment model with first-order rate constants was fit to the data to distinguish active drug from inactive metabolites. RESULTS: The mean +/- SD AUCs in plasma ultrafiltrate for oxaliplatin, cisplatin, and carboplatin were 61 +/- 22, 18 +/- 6, and 211 +/- 64 micromol/L hour, respectively. The AUCs in CSF were 1.2 +/- 0.4 micromol/L hour for oxaliplatin, 0.56 +/- 0.08 micromol/L hour for cisplatin, and 8 +/- 2.2 mumol/L hour for carboplatin, and CSF penetration was 2.0%, 3.6%, and 3.8%, respectively. For oxaliplatin, cisplatin, and carboplatin, the pharmacokinetic model estimated that active drug accounted for 29%, 79%, and 81% of platinum in plasma ultrafiltrate, respectively, and 25%, 89%, and 56% of platinum in CSF, respectively. The CSF penetration of active drug was 1.6% for oxaliplatin, 3.7% for cisplatin, and 2.6% for carboplatin. CONCLUSIONS: The CSF penetration of the platinum analogues is limited. The pharmacokinetic model distinguished between active drug and their inactive (inert) metabolites in plasma and CSF.

Toxicity and cerebrospinal fluid levels of carboplatin chronically infused into the brainstem of a primate.

PURPOSE: Carboplatin was infused into the brainstem of cynomolgus monkeys to investigate neurotoxicity and systemic exposures following chronic local delivery. METHODS: Infusions at 0.42 microl/h were intended to deliver 0.025 (n = 2), 0.075 (n = 3), 0.25 (n = 5), and 0.75 (n = 3) mg/kg by day 30. Laboratory tests, radiographic measurements, and clinical observations were used to monitor toxicity. Blood and cerebrospinal fluid (CSF) were sampled for platinum. RESULTS: Lethargy and ataxia were observed after week 4 in the monkeys given 0.075 mg/kg, and week 2 in the monkeys given 0.25 mg/kg when the infused doses were approximately 250 and 400 microg, respectively. Rapidly progressive neurotoxicity with the 0.75 mg/kg dose required termination of the infusions at days 4-10. Hematology and chemistry values were unremarkable in all groups. Blood levels of platinum remained undetectable in 0.025 and 0.075 mg/kg dose groups. Levels in the 0.25 mg/kg group were 3.1 +/- 0.6 microg/l at 2 weeks and 5.2 +/- 0.8 microg/l at 1 month. The CSF platinum levels varied. Animals in the 0.25 mg/kg group had higher CSF levels at 2 weeks (avg. 65 microg/l, range 36-89) compared to their 1 month value (avg. 60 microg/l, range 7-170), despite the constant infusion. CONCLUSION: Carboplatin can be chronically infused into monkey brainstems. Neurotoxicity is the predominant side effect and is dose-dependent. Pharmacokinetics of local and systemic delivery are different for carboplatin. Further studies are needed to monitor toxicity at higher flow rates and to investigate drug binding to abnormal central nervous system (CNS) tissues.

Pharmacokinetics of etoposide and carboplatin in cerebrospinal fluid and plasma during hyperosmotic disruption of the blood brain barrier and intraarterial combination chemotherapy.

The present paper investigates the pharmacokinetics of etoposide (VP-16) and carboplatin (CBDCA) in plasma and the cerebrospinal fluid (CSF), in the space left by tumor removal, of patients with glioma. Eight Japanese patients with glioma received a course of hyperosmotic disruption of the blood-brain barrier (HODBBB) and intraarterial combination chemotherapy with 60 mg/m2 of VP-16 and 300 mg/m2 of CBDCA. All patients were initially administered mannitol, followed by infusion of the anticancer drugs into the right internal carotid artery. Blood samples and samples of CSF in the space left by tumor removal were obtained. VP-16 and CBDCA concentration were measured by HPLC, and the pharmacokinetic parameters of these drugs estimated in CSF and plasma. The plasma concentrations of VP-16 and CBDCA peaked at the end of infusion, then decreased in a bi-exponential decay pattern during the remainder of the treatment period. Both VP-16 and CBDCA were detectable in CSF beginning 0.5 h after the initiation of each infusion, and were then slowly eliminated from the space left by tumor removal. The mean maximum CSF concentration of VP-16 and CBDCA was 0.17 and 15.25% of that in plasma, respectively. The mean area under the time-CSF concentration curve from 0 to 24 h after VP-16 and CBDCA infusion was 1.91 and 113.6% of plasma, respectively. In two of the eight patients, the clinical response to treatment was a partial response and other patients showed no change. HODBBB and intraarterial combination chemotherapy with VP-16 and CBDCA may be useful in patients with brain tumors for maintenance chemotherapy.