Clinical pharmacokinetics of carboplatin

Pharmacokinetic studies in children with cancer

We reviewed the current status of our knowledge of pharmacokinetics and pharmacodynamics of some anti-neoplastic drugs, used in the treatment of childhood cancer. Extrapolation of data from pharmacokinetic studies in adults to the paediatric population is often not feasible. Specific studies in children are needed. Of all reviewed anti-neoplastic drugs methotrexate appears to be most extensively studied. Methotrexate pharmacokinetics is correlated with toxicity and response to therapy, and it has been shown that individualized adaptive dosing of methotrexate is correlated with a better response to therapy without increasing toxicity in children with ALL and osteosarcoma. Of most of the other reviewed anti-neoplastic drugs it is demonstrated that pharmacokinetics is correlated with toxicity, and of some drugs a relationship of pharmacokinetics with response to therapy is demonstrated as well. In case of cytarabine, etoposide, and teniposide, individualized dosing also appears to be feasible. However, there is no evidence that this strategy improves response to therapy. Specifically data on pharmacokinetic and pharmacodynamic correlations and effect of pharmacokinetically guided, individualized dosing are important for the design of optimal cancer chemotherapy for individual patients. Unfortunately for a considerable number of anti-neoplastic drugs these specific data are lacking in children and future research is needed.

Cisplatin stabilizes a multimeric complex of the human Ctr1 copper transporter: requirement for the extracellular methionine-rich clusters

Cisplatin is a highly effective cancer chemotherapy agent. However, acquired resistance currently limits the clinical utility of this drug. The human high affinity copper importer, hCtr1, and its yeast and murine orthologues have been shown to mediate the uptake of cisplatin. This transporter is located at the plasma membrane under low copper conditions, and excess copper concentrations stimulate its endocytosis and degradation. In this study we further examined the link between cisplatin and hCtr1 by examining whether cisplatin can also stimulate the endocytosis and degradation of hCtr1. The steady-state location of hCtr1 and its endocytosis from the plasma membrane were not altered by cisplatin treatment. Unexpectedly, cisplatin treatment of a cell line expressing hCtr1 revealed the time- and concentration-dependent appearance of a stable hCtr1 multimeric complex, consistent with a homotrimer, which was not observed following copper treatment of these same cells. Mutagenesis studies identified two methionine-rich clusters in the extracellular amino-terminal region of hCtr1 that were required for stabilization of the hCtr1 multimer by cisplatin, suggesting that these sequences bind cisplatin and form crosslinks between hCtr1 polypeptides. Treatment with the metal chelator dimethyldithiocarbamate disassembled the hCtr1 multimer following cisplatin exposure, suggesting that platinum was an integral component of this complex. These studies provide the first evidence for a direct interaction between cisplatin and the hCtr1 protein and establish that cisplatin and copper have distinct biochemical consequences on this transporter.

Pharmacokinetic analysis of combination chemotherapy with carboplatin and etoposide in small-cell lung cancer patients undergoing hemodialysis

BACKGROUND

The aim of this study was to use pharmacokinetic analysis to investigate the efficacy and toxicity of combined chemotherapy with carboplatin (CBDCA) and etoposide (ETP) in small-cell lung cancer (SCLC) patients with chronic renal failure undergoing hemodialysis (HD).

PATIENTS AND METHODS

Three SCLC patients with chronic renal failure undergoing HD were treated with CBDCA (300 mg/m(2)) on day 1 and ETP (50 mg/m(2)) on days 1 and 3, followed by HD 1 h after completing the administration of anticancer agents on each day. The pharmacokinetic analysis of CBDCA and ETP was planned for at least the first two courses of the chemotherapy in each patient.

RESULTS

Two complete responses and one partial response were achieved in the three patients. Two patients experienced grade 3/4 neutropenia and required blood transfusion due to thrombocytopenia and anemia. Non-hematological toxicities were moderate. The pharmacokinetic analysis revealed that the platinum and the ETP concentrations in the plasma were similar to those in patients with normal renal function during the first 24 h, while the platinum still remained in the plasma for over 90 h.

CONCLUSIONS

Chemotherapy with CBDCA (300 mg/m(2) on day 1) and ETP (50 mg/m(2) on day 1, 3) as used in the present study may be a suitable regimen for SCLC patients undergoing HD, although careful attention should be given to hematological toxicities.

Kinetic Study on the Reactions of Platinum Drugs with Glutathione

The binding of platinum (Pt) drugs (oxaliplatin, carboplatin, and cisplatin) to glutathione (GSH, 6.75 mM) was investigated at 37 degrees C in Hepes (100 mM, pH approximately 7.4) or Tris-NO(3) (60 mM, pH 7.4) buffer and NaCl (4.62, 6.63, or 7.82 mM). The conditions were chosen to mimic passage of clinical concentrations of the drugs (135 microM) through the cytosol. The reactions were monitored by UV-absorption spectroscopy, high-performance liquid chromatography (HPLC), and atomic absorption spectroscopy. The initial rates, detected by UV absorbance, were similar for oxaliplatin and cisplatin reacting with GSH and were more than 5-fold faster than for carboplatin reacting with GSH. The Pt contents in HPLC eluates corresponding to unbound drug decreased exponentially with time, confirming that the reactions were first order in [Pt drug] and allowing determination of the pseudo first-order rate constants (k(1)). The second-order rate constants (k(2)) were calculated as k(1) divided by [GSH]. The k(2) value for oxaliplatin reacting with GSH was approximately 3.8 x 10(-2) M(-1) s(-1), for cisplatin reacting with GSH approximately 2.7 x 10(-2) M(-1) s(-1), and for carboplatin reacting with GSH approximately 1.2 x 10(-3) M(-1) s(-1) (approximately 32-fold slower than that of oxaliplatin and approximately 23-fold slower than that of cisplatin). These results demonstrate an influence of ligands surrounding the Pt coordination sphere on the reactivity of Pt(2+) with GSH.

An experimental study of the combined effect of radiotherapy and chemotherapy on head and neck squamous cell carcinoma cell line

OBJECTIVE

We have reported clinical effects of radiotherapy combined with either CDDP or CBDCA for head and neck cancer. In this study, we examined the combined effects of either CDDP or CBDCA with irradiation on the cell lines established from tongue SCC.

METHODS

The effects of irradiation, chemotherapy and the combined therapy on growth of the cell lines were examined respectively by the Alamar Blue assay.

RESULTS

The combination of 0.1 and 0.25 microg/ml CDDP with four times exposure to I Gy 60Co. which did not affect the growth of the cell lines, suppressed the growth synergistically. The combination of 1.0 and 2.0 ) microg/ml of CBDCA with four times exposure to 1 Gy 60Co showed synergistically suppressive effects on the growth of the cell lines.

CONCLUSION

It was suggested that the radiotherapy combined with the platium coordination complexes had a clinical usefulness in patients with head and neck cancer.

Carboplatin, ifosfamide, and vinorelbine in the treatment of advanced non-small-cell lung cancer: a phase II study

The authors evaluated the efficacy and toxicity of the combination of carboplatin, ifosfamide, and vinorelbine in the treatment of advanced non-small-cell lung cancer. From March 1994 through March 1996, 56 previously untreated patients with stage IIIB or stage IV non-small-cell lung cancer with measurable lesions and good performance status were entered in the study. The chemotherapy schedule was as follows: carboplatin 100 mg/m2 and ifosfamide 1,500 mg/m2 with mesna on days 1, 2, and 3; vinorelbine 25 mg/m2 on days 1 and 8, every 21 days; for a total of six courses. Among 55 evaluable patients there were three complete responses (5%) and 22 partial responses (40%), for a response rate of 45% (95% confidence interval, 32-59%). The median response duration was 10.3 months (range, 2.5-27.7 months), and median survival time was 11.3 months (range, 1.1-28.1 months). The survival rate at 1 year was 48%. Toxicity included hematologic toxicity in 60% of the 247 treatment cycles administered, nausea, alopecia, and neuropathy. One pathologic complete response was observed in a patient with stage IIIB disease who became operable after four courses of chemotherapy. The outpatient treatment with carboplatin, ifosfamide, and vinorelbine shows activity in advanced non-small-cell lung cancer. The toxicity was well tolerated by patients with a good performance status.

Review of the comparative pharmacology and clinical activity of cisplatin and carboplatin

PURPOSE

To review the pharmacodynamics, pharmacokinetics, toxicities, and relative clinical activities of cisplatin and carboplatin. Through a search of the MEDLINE database, we identified phase III clinical trials and pharmacologic studies comparing cisplatin and carboplatin published in the English language medical literature from January 1966 to December 1997.

RESULTS

Prospective randomized trials comparing cisplatin to carboplatin were identified for ovarian (n = 12), germ cell (n = 4), non-small-cell lung (n = 1), small-cell lung (n = 3), and head and neck (n = 4) cancers. Carboplatin and cisplatin were equally effective in suboptimally debulked ovarian cancer and extensive-stage small-cell lung cancer. One study each showed a trend toward better survival in favor of cisplatin for patients with optimally debulked ovarian and limited-stage small-cell lung cancers. These results were, however, based on subset analyses. In germ cell tumors, carboplatin was inferior because of lower relapse-free survival rates. Cisplatin produced superior response rates and survival in head and neck cancers. There are no published randomized phase III studies of bladder, cervical, endometrial, and esophageal cancers.

CONCLUSION

Carboplatin does not possess equivalent activity to cisplatin in all platinum-sensitive tumors. Carboplatin can replace cisplatin in chemotherapy regimens for suboptimally debulked ovarian cancer. Two ongoing studies will address the same question in optimally debulked disease. Carboplatin can also be substituted for cisplatin in the treatment of non-small-cell and extensive-stage small-cell lung cancers. Its role in limited-stage small-cell lung cancer needs to be investigated further. Carboplatin is inferior to cisplatin in germ cell, head and neck, and esophageal cancers. Randomized studies are needed to determine whether carboplatin has equivalent efficacy to cisplatin in bladder, cervical, and endometrial cancers.

Fractionated carboplatin radiosensitization: a phase I dose-escalation study

Carboplatin is one of the most common drugs used for radiochemotherapy of cancer. However, the best way to combine the drug with fractionated radiotherapy has not been established. In the present study the authors investigated which maximum tolerated daily bolus dose of carboplatin would allow safe radiopotentiation for 10 consecutive radiotherapy days, the scheme being repeated twice during the 6 weeks that a conventional radiotherapy scheme lasts. Seventy-two patients with lung or pelvis malignancies were included in a dose escalation study. Twenty-four patients comprised the first baseline cohort and were treated with radiotherapy alone. The daily dose of carboplatin was escalated starting from 38 mg/m2 daily (for 10 days) and increasing by 7 mg/m2 per day. Six patients were to be included in each cohort. All 12 patients treated at the 38 mg/m2 and 45 mg/m2 dose level completed two cycles of 10-day carboplatin treatment with no grade III-IV toxicity. Granulocyte colony-stimulating factor effectively averted the incidence of neutropenia and allowed the administration of the second carboplatin 10-day cycle in five of six patients at the 52 mg/m2 daily dose level. Platelet grade III-IV toxicity was observed in all 12 patients (six supported with granulocyte colony-stimulating factor and six with granulocyte colony-stimulating factor and recombinant human erythropoietin) treated at the 59 mg/m2 daily dose level and none of them received the second cycle of chemotherapy. Twelve patients were treated at the same dose level using amifostine 500 mg before carboplatin infusion. Two patients interrupted chemotherapy because of severe nausea and vomiting. Nine of 10 who accomplished the 10-day treatment had platelet levels more than 90,000/microl on day 28 and completed the second 10-day cycle without severe toxicity. Acute radiation toxicity did not increase in the carboplatin cohorts. In this study the authors established a high-dose fractionated carboplatin schedule that can be safely administered during radical radiotherapy.

Release of cytokines from human umbilical vein endothelial cells treated with platinum compounds in vitro

Endothelial cells (EC) produce cytokines, such as interleukin (IL)-1, IL-6, IL-8 and granulocyte-macrophage colony-stimulating factor (GM-CSF). These cytokines have an important role in the proliferation and differentiation of hematopoietic progenitor cells. On the other hand, anticancer agents generally cause hematopoietic disorders. However, little is known about the effects of chemotherapeutic agents on the secretion of cytokines from EC. Therefore, we investigated if treatment with platinum compounds may stimulate EC to secrete cytokines. EC newly isolated from a human umbilical vein were exposed to cisplatin, carboplatin, or TRK-710 for 80 min, then the cells were washed and placed in fresh medium. The levels of cytokines in the fresh medium were measured by the ELISA method, the levels of intracellular hydrogen peroxide (H2O2) were measured by flow cytometry, and the rhodamine 123-stained live mitochondria of the EC were observed under a confocal laser microscope. Platinum compounds induced cytokine production in human EC: cisplatin most prominently induced the release of IL-1 and IL-6, and TRK-710 had the greatest ability to induce the release of GM-CSF. Intracellular H2O2 production and IL-8 release were transiently induced immediately after treatment with platinum compounds, leading to IL-1 release when H2O2 production was eliminated. These results may provide new insights into the hematological toxicity induced by anticancer agents and the role of IL-1 and IL-6 secreted from EC in this toxicity.

Enhancement of warfarin response in a patient receiving etoposide and carboplatin chemotherapy

OBJECTIVE

To report a case of a possible drug interaction between warfarin, carboplatin, and etoposide resulting in a marked increase in a patient's response to warfarin, and to outline monitoring strategies for this interaction.

CASE SUMMARY

A 74-year-old white man receiving warfarin (average dose 42.5 mg/wk) for atrial fibrillation was diagnosed with a right testicular non-seminoma mixed germ cell tumor. Mediastinal metastases were subsequently discovered, and the patient was treated with a chemotherapy regimen including carboplatin and etoposide. Sixteen days after the first course of chemotherapy, the international normalized ratio (INR) was increased to 12.6 from a baseline range of 1.15-2.11 that was observed over the previous 8 months of therapy, indicating a clinically significant alteration in the pharmacodynamic response to warfarin.

DISCUSSION

This patient had no concomitant disease or dietary changes to explain the altered response to warfarin. Carboplatin and etoposide have not been reported to inhibit warfarin metabolism. However, previous reports have suggested that etoposide may displace warfarin from its protein binding sites, resulting in an early elevation in prothrombin time following chemotherapy. The late elevation of INR observed in our patient suggests that his response to warfarin may have been due to the displacement of warfarin by elemental platinum, which has a long plasma half-life.

CONCLUSIONS

This case report suggests a possible drug interaction between carboplatin, etoposide, and warfarin. Because of the risk associated with an increased response to warfarin, we recommend close monitoring of the INR, perhaps twice weekly, early and later in the time course following chemotherapy with these agents. Appropriate dosage adjustments of warfarin should be performed if an altered response to warfarin is observed.

Pharmacokinetic evaluation of zeniplatin in humans

Zeniplatin, a more water-soluble organoplatinum than cisplatin, was evaluated for clinical pharmacology in the context of a phase II trial in previously treated patients with ovarian carcinoma. A total of 12 patients were given zeniplatin at 120 mg/m2 by rapid intravenous infusion over 90 min, with both blood and urine being sampled. All platinum moieties were analyzed in whole blood, plasma, plasma ultrafiltrate, and urine by atomic absorption, and free zeniplatin was analyzed in plasma ultrafiltrate by specific high-performance liquid chromatography (HPLC). In a comparison of the platinum-time concentration curve, AUC (area under the curve) values indicated that approximately 90% of platinum moieties were bound to circulating plasma proteins. There was no evidence of drug accumulation after repetitive dosing. The terminal half-life (t1/2) of this drug in plasma ultrafiltrate (3.7-7.2 h.) as measured by HPLC was slightly longer than that of carboplatin, whereas total platinum moieties in plasma displayed a long t1/2 (124-154 h). Approximately 60% of platinum moieties could be recovered in the urine within 24 h. These findings suggest that zeniplatin has a pharmacokinetic profile similar to that of carboplatin.

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 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).2+ 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.(ABSTRACT TRUNCATED AT 400 WORDS)

Pharmacokinetics of cisplatin instilled into the pleural cavity following panpleuropneumonectomy in patients with malignant pleurisy due to lung cancer

The pharmacokinetics of cisplatin instilled into the pleural cavity in patients with malignant pleurisy due to lung cancer were studied. Higher concentrations of total and free platinum in pleural effusion have been maintained for longer than 72 hours in patients who were subjected to panpleuropneumonectomy than in those who received simple drainage. Early rapid drop of total platinum within 6 hours was significant in the drainage group. Total platinum level in the serum of the panpleuropneumonectomy group gradually increased during 1-72 hours, however, that of the drainage group was highest at 1 hour after instillation and declined gradually with time. Free platinum in the serum was also present at lower concentrations in the panpleuropneumonectomy group than in the drainage group. These facts may be ascribed to the absorptive activity of parietal pleura which is present in the drainage group but absent in the panpleuropneumonectomy group. In summary, removal of the parietal pleura by panpleuropneumonectomy could cause cisplatin to be not only more active but also less toxic in patients with malignant pleurisy due to lung cancer.

Phase I clinical and pharmacokinetic study of zeniplatin, a new platinum complex

Forty-six patients with refractory solid malignancies received the new platinum complex [2,2-bis(aminomethyl)-1,3-propanediol-N-N'] [1,1-cyclobutanedicarboxylato] [(2-)0,0')] platinum (zeniplatin). Zeniplatin was given, without hydration or mannitol, as a 60- to 90-min i.v. infusion every 3 weeks at doses ranging from 8 to 145 mg/m2. The maximum tolerated dose of zeniplatin was 145 mg/m2. The dose-limiting toxicity of zeniplatin was dose-related leukopenia and neutropenia, with the nadir usually observed between 1 and 2 weeks after therapy and recovery usually occurring by 3 weeks after therapy. Thrombocytopenia was rare. The most prominent non-hematological side-effect of zeniplatin was nausea and vomiting. Other non-hematological side-effects were mild or absent. Zeniplatin did not induce significant neurological or auditory toxicity. Zeniplatin was not nephrotoxic at doses less than or equal to 120 mg/m2. At 145 mg/m2, the clearance decreased by a mean of 40% after 2 cycles of therapy. Two patients, one with malignant melanoma and one with renal cell cancer, achieved a partial response. Pharmacokinetics of free (plasma ultrafiltrates) and total platinum in plasma were determined in 5 patients. An in vitro study of the rate and extent of zeniplatin binding to protein in human plasma was also performed. Free and total platinum were measured by flameless atomic absorption spectrometry; free zeniplatin was measured in ultrafiltrate by HPLC. Total and free plasma platinum concentrations were co-modelled using the information from the in vitro study.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the cytotoxic activities of cisplatin and carboplatin against glioma cell lines at pharmacologically relevant drug exposures

Carboplatin has lower nephro- and neurotoxicities and better penetration into brain tissue than cisplatin. If carboplatin has comparable cytotoxicity against glioma cells, it might have a therapeutic advantage in the treatment of malignant gliomas. Using an assay of colony-forming efficiency, we compared the cytotoxicity of these two drugs in human glioma cell lines SF-126, SF-188, U87-MG, and U251-MG. The experiments were designed so that the product of in vitro drug concentration (C) and time (T) would encompass the same range of values as the C x T of the ultrafilterable platinum plasma fraction as determined by pharmacokinetic studies in man. The in vitro stability of the drugs was evaluated by measuring the cytotoxicity of aged drugs with a microculture tetrazolium assay. Cisplatin and carboplatin were both stable during the 2-h treatment. The cytotoxic activities of these drugs at clinically achievable levels of drug exposure were of the same order of magnitude. These results, in conjunction with the lower nephro- and neurotoxicities of carboplatin, the higher platinum levels in brain tissue after treatment with carboplatin, and the encouraging results of carboplatin in the clinical treatment of brain tumors that have been demonstrated in other studies, suggest that carboplatin might be preferable to cisplatin in the treatment of patients with malignant glioma.

Clinical trial and pharmacokinetics of carboplatin 560 mg/m2 in children

We report a clinical trial with carboplatin (CBDCA) in 15 children with malignant solid tumors recurrent after or resistant to conventional treatment. Based on previous phase I clinical trials, these children were given a dose of CBDCA 560 mg/m2 by intravenous infusion every 4 weeks. The study includes a pharmacokinetic analysis of CBDCA in three patients. This clinical trial shows the feasibility of this CB-DCA schedule, even after high cumulative doses of previous chemotherapy. As expected the main toxicity was hematologic but the risk of renal and ototoxicity is not excluded and these functions have still to be monitored when this relatively high dose of CBDCA chemotherapy is used.

Carboplatin: a clinical review

Carboplatin is a platinum analog that is less nephrotoxic, less neurotoxic, and less emetic than cisplatin, but has a similar spectrum of antitumor activity. Myelotoxicity is dose limiting. Carboplatin offers several advantages over cisplatin, in addition to a better quality of life. It may be useful in ABMT in refractory germ cell cancers in combination with etoposide. It may also prove useful in patients who have impaired renal function but require a drug with the efficacy of cisplatin.