Nonlinear renal clearance of ultrafilterable platinum in patients treated with cis-dichlorodiammineplatinum (II)

Summary Nonlinear renal clearance of ultrafilterable platinum was observed in 5 of 7 patients given cis-dichlorodiammineplatinum (II) in doses of 50–140 mg/m² by short-term infusion (2h). Average renal clearance determined during and 24 h after infusion ranged from 100 to 543 ml/min and always exceeded creatinine clearance, suggesting that ultrafilterable platinum was renally secreted. Saturable tubular reabsorption was postulated on the basis that renal clearance was highest at peak plasma and urinary levels and fell as the levels declined. Although an overall relationship between dose and renal clearance was not apparent, one patient receiving the highest dose (140 mg/m²) had elevated average renal clearance (485 ml/min), probably associated with saturation of reabsorption, whereas a patient receiving 50 mg/m² had the lowest average renal clearance (100 ml/min), indicating that either active secretion was lower, or tubular reabsorption was saturated. One patient also showed urine-flow-dependent changes in renal clearance. Four patients had transient rises in ultrafilterable platinum levels, which were attributed to changes in renal tubular reabsorption. The results suggest that renal clearance of ultrafilterable platinum is probably dependent on cis-DDP dose, urine flow rate, and individual variability in the extent of active secretion and tubular reabsorption. A sensitive HPLC method was applied and ultrafilterable platinum was detected in the plasma of all patients 24 h after infusion. Renal tubular reabsorption may result in prolonged plasma levels of ultrafilterable platinum, which could contribute to the drug's antitumour effect.     

High dose melphalan in children with advanced malignant disease

Summary Nine children with poor-prognosis malignancies — seven with advanced neuroblastoma and two with metastatic Ewing's sarcoma — were give high doses of melphalan (HDM), 150 mg/m² (3 patients) and 180 mg/m² (6 patients), as a late intensification agent combined with noncryopreserved autologous bone marrow transplants. Melphalan levels in the plasma decreased biphasically, with mean half-lives of 6.6 min and 3.0 h. At the time of marrow reinfusion (12–21 h after HDM) the melphalan plasma level was generally below 0.1 g/ml. The renal contribution to melphalan clearance was low, a mean of 5.8% of the injected dose being found in patients' urine over the 12 h following HDM administration. No significant difference was seen in pharmacokinetic parameters between patients undergoing and not undergoing forced diuresis.     

Dose-escalating and pharmacological study of bortezomib in adult cancer patients with impaired renal function: a National Cancer Institute Organ Dysfunction Working Group Study

Purpose

To determine the toxicities, pharmacokinetics, pharmacodynamics, and maximum tolerated dose of bortezomib in patients with renal impairment and to develop dosing guidelines for such a patient population.

Patients and Methods

Sixty-two adult cancer patients received intravenous bortezomib at 0.7?C1.5?mg/m² on days 1, 4, 8, and 11 every 3?weeks. Patients were stratified by 24-h creatinine clearance (CrCl) normalized to body surface area (BSA) 1.73?m² into five cohorts: normal renal function (??60?ml/min/1.73?m²); mild dysfunction (40?C59?ml/min/1.73?m²); moderate dysfunction (20?C39?ml/min/1.73?m²); severe dysfunction (<20?ml/min/1.73?m²); and dialysis. Dose escalation was planned for the four cohorts with renal dysfunction. Plasma bortezomib concentrations and blood 20S proteasome inhibition were assayed.

Results

Bortezomib escalation to the standard 1.3?mg/m² dose was well tolerated in all patients with CrCl ??20?ml/min/1.73?m²; 0.7?mg/m² was tolerated in three patients with severe renal dysfunction (<20?ml/min/1.73?m²). Bortezomib dose escalation was well tolerated in nine dialysis patients, including to 1.3?mg/m² in four patients. Decreased CrCl did not affect bortezomib pharmacokinetics or pharmacodynamics. Bortezomib-related side-effects were neither more common nor severe in patients with renal dysfunction versus those with normal renal function.

Conclusion

Bortezomib 1.3?mg/m² is well tolerated, and dose reductions are not necessary in patients with renal dysfunction. Extrapolation from clinical and pharmacologic data suggests patients with severe renal dysfunction, including dialysis patients, can receive bortezomib at the full dose established to be clinically effective in the general patient population.     

Pharmacokinetic study of doxifluridine given by 5-day stepped-dose infusion

Summary Doxifluridine (5-deoxy-5-fluorouridine, 5-dFUR) metabolism has been reported to be saturable and associated with a fall in clearance of the drug as the dose is increased. The aim of the present study was to determine the disposition of 5-dFUR and 5-fluorouracil (5-FU) when 5-dFUR was given as a 5-day infusion, with the infusion rate increased stepwise every 24 h. Measurement of plasma and urinary levels of 5-dFUR and 5-FU at steadystate for each infusion rate enabled the estimation of 5-dFUR renal (Cl_R) and nonrenal (Cl_NR) clearance and 5-FU renal clearance. A total of 28 patients with histologically proven malignancy received 5-day courses of 5-dFUR ranging in dose from 3.75 to 20 g/m² per 120 h. The lowest dose given over 24 h was 0.25 g/m², and the highest was 5 g/m². Steady-state plasma levels of 5-dFUR ranged from 167 to 6.519 ng/ml. At these plasma levels there was no evidence of significant saturation of 5-dFUR metabolism; steady-state plasma levels of 5-dFUR increased approximately linearly with dose, and nonrenal clearance did not change significantly with dose. There was also no evidence of nonlinearity in 5-dFUR renal clearance. The mean (±SD) Cl_R of 5-dFUR was 108.9±53.6 ml/min per m² (range, 45.7–210 ml/min per m²), and the Cl_NR was 728±181 ml/min per m² (range, 444–1,119 ml/min per m²). Renal clearance comprised 13% of the total 5-dFUR clearance. The mean renal clearance of 5-FU was 100.8±48.6 ml/min per m² (range, 23.5–198 ml/min per m²). There was considerable interpatient variability in 5-dFUR renal and nonrenal clearance, event at the same dose level. We concluded that the administration of 5-dFUR by the infusion method described avoided the saturation of nonrenal elimination processes reported to occur with shorter infusion schedules.This study was supported by a grant from F. Hoffmann-La Roche, Basel, Switzerland     

A phase I and pharmacokinetics study of prolonged ambulatory-infusion carboplatin

A total of 18 patients received 6-week ambulatory infusions of carboplatin in groups at dose levels of 14, 28, 35 and 42 mg/m² per day. The dose-limiting toxicity was myelosuppression. At 42 mg/m², three of four patients had WHO grade 4 and one of four had grade 3 neutropenia, whereas two patients had grade 3 thrombocytopenia. At 35 mg/m², two of five patients had grade 3 neutropenia, whereas one had grade 4 and two had grade 3 thrombocytopenia. Non-hematological toxicities were predominantly gastrointestinal, with 3 of 18 patients experiencing grade 3 emesis. Total and ultrafiltrable platinum (UFPt) were assayed by flameless atomic absorption spectrometry in weekly and post-infusion plasma and urine samples. In plasma, levels of total platinum increased throughout the infusion, and the protein binding slowly increased from 60% platinum bound at week 1 to 90% bound by week 4. Although the UFPt level reached a steady state within 1 week, the concentration did not increase with the dose level, remaining at a mean value of 0.58±0.24 M. Renal excretion of platinum accounted for 70±12% of the dose at steady state. There was a high inter-patient variability in both total body clearance of UFPt (range, 83–603 ml/min) and renal clearance (range, 67–390 ml/min). A terminal elemination half-life of 13–27 h was noted for post-infusion UFPt. Neutropenia was linearly related to the total daily carboplatin dose, but neither neutropenia nor thrombocytopenia could be related to steady-state UFPt or the UFPt area under the concentration-time curve (AUC). The recommended dose for phase II studies is 28 mg/m² per day.     

Phase I and pharmacokinetic study of tiazofurin (NSC 286193) administered by 5-day continuous infusion

Summary A phase I and pharmacokinetic study of tiazofurin (NSC 286193), a C-nucleoside that inhibits IMP dehydrogenase, has been completed. The drug was administered by continuous infusion over 5 days. The maximum tolerated dose was 1650 mg/m² per day, neurological toxicity being the dose-limiting factor. Gastrointestinal and hematological toxicity were mild. A definite relationship exists between dosage and steady-state levels. The plasma clearance was 29.13 (±SD 4.05) ml/min per m². No complete or partial remissions were demonstrated among the 18 patients treated at five dose levels between 550 mg/m² and 2200 mg/m² per day.     

Phase I clinical and pharmacologic trial of trimetrexate in combination with 5-fluorouracil

Summary Based on the synergy of sequential methotrexate (MTX) and 5-fluorouracil (5-FU) in vitro and in vivo and the superior antitumor activity of trimetrexate (TMTX) compared with MTX in preclinical models, we carried out a phase I trial of TMTX and 5-FU (fixed dose, 400 mg/m² per day), both given as 10-min i.v. infusions daily x5 days, every 28 days. The TMTX dose was escalated from 3.0 to 14.0 mg/m² per day. In all, 92 evaluable courses were given to 34 patients, half of whom were heavily pretreated with radiation or cytotoxics. Myelosuppression and mucositis were the dose-limiting toxicities but were not different in heavily or minimally pretreated patients; there were five episodes of moderate to severe mucositis. Rash, fatigue, and diarrhea were mild toxicities. Plasma TMTX elimination was biexponential, with a mean t._1/2 of 0.23 h and a t._1/2 of 16.7 h. The area under the plasma TMTX concentration versus time curve increased linearly with dose, suggesting first-order elimination. Total plasma TMTX clearance (mean±SD) was 14.3±5.9 ml/min per m². Renal clearance accounted for approximately 7% of total clearance, indicating biotransformation as the major route of elimination. TMTX was highly protein-bound (97%). Thus, TMTX can be given with 5-FU (400 mg/m²) on a daily x 5-day bolus schedule at the 12 mg/m² per day dose level, which was the recommended dose of TMTX as a single agent for phase II studies using the 5-day bolus schedule.     

Regional pharmacokinetic selectivity of intrapleural cisplatin

The pharmacokinetics and toxicity of cisplatin were investigated in 3 patients affected by malignant mesothelioma who received 90 mg/m² of the drug intrapleurally. The mean area under the pleural Pt concentration versus time curve (AUC) [12.83 (S.D. 4.06) mg.min/ml] was about 50 times greater than that detected in plasma [0.27 (0.03) mg.min/ml], indicating a clear pharmacological advantage for this route of administration. The mean plasma total Pt concentration was 1.1 μg/ml and the apparent total body clearance was 268 (101) ml/min. Platinum plasma pharmacokinetic data measured following intrapleural cisplatin administration (4 patients) were compared with those observed in 7 patients treated intravenously with the same dose of cisplatin (90 mg/m²) under the same modalities of hydration. Intrapleural administration of cisplatin resulted in significantly lower plasma total partial AUC (P < 0.05) and prolonged plasma levels of filterable Pt compared with intravenous administration. No difference between the two routes of cisplatin administration in the renal clearance (S.D.) of filterable Pt [132 (64) ml/min and 122 (39) ml/min for intravenous and intrapleural cisplatin, respectively] were observed. None of the mesothelioma patients developed clinical symptoms or signs of pleural inflammation. The intrapleural treatment did not produce haemotoxicity and the emetic toxicity was lower compared with that observed in patients receiving cisplatin intravenously.     

Pharmacokinetics of unchanged carboplatin (CBDCA) in patients with small cell lung carcinoma

Summary The disposition of the cisplatin analogue carboplatin was studied in seven patients with small cell lung cancer. Carboplatin 100 mg/m² was administered without hydration by a 1-h infusion with VP16-213 120 mg/m² on days 1, 2 and 3 of each course. Plasma and urine collections were made on days 1 and 3 of the first course of treatment. Carboplatin levels in plasma ultrafiltrate and urine were quantitated using a specific and sensitive, highperformance liquid chromatographic assay which involved sample clean-up on a Dowex-2 column prior to injection. Estimates of pharmacokinetic parameters determined using either compartmental or non-compartmental methods were comparable. There was no difference between carboplatin pharmacolinetic parameters determined on days 1 and 3 of treatment. The mean (±SD) carboplatin half-life determined from plasma data on day 1 was 105±30.4 min and was not significantly different from that determined using urinary excretion rate data (107±51.7 min). Urinary excretion rate plots showed that carboplatin elimination was mono-exponential for up to 14 h after infusion. Totalbody clearance was 105±40.0 ml min^-1 m^-2, renal clearance 64.3±44.1 ml min^-1 m^-2, and volume of distribution 17.3±4.2 l/m² on the 1st day of treatment. Of the administered dose, 58.4%±21.2% was recovered in urine over a 24-h period after the start of the infusion. The mean renal clearance of carboplatin was comparable to creatinine clearance. Carboplatin disposition was clearly defined in the patients studied using analytical methodology specific for the unchanged drug.     

Phase I study of the effects of renal impairment on the pharmacokinetics and safety of satraplatin in patients with refractory solid tumors

BackgroundSatraplatin is an oral platinum analog with demonstrated activity in a range of malignancies. The current study was designed to evaluate the effect of varying degrees of renal impairment on the safety and pharmacokinetics (PKs) of satraplatin.Patients and methodsPatients with advanced solid tumors, refractory to standard therapies, were eligible. The study included four cohorts of patients with varying levels of renal function, and eight patients per cohort: Group 1 (G1) = normal renal function; G2 = mild renal impairment [creatinine clearance (CrCl) 50–80 ml/min]; G3 = moderate impairment (CrCl 30 to <50 ml/min); G4 = severe impairment (CrCl <30 ml/min). Satraplatin was administered orally at 80 mg/m²/day on days 1–5 every 35 days.ResultsA total of 32 patients were enrolled, 8 patients in each renal function group. Each group tolerated the dose of 80 mg/m²/day on days 1–5 every 35 days without the need for dose deescalation. The most common adverse events were fatigue (63%), nausea (56%), diarrhea (53%), anorexia (47%), constipation (38%), vomiting (28%), anemia, dyspnea, and thrombocytopenia (25%). There were no dose-limiting toxic effects in any study group. There was increased exposure to plasma platinum and plasma ultrafiltrate platinum in patients with moderate to severe renal impairment.ConclusionsSatraplatin PKs was altered in patients with renal impairment. However, a corresponding increase in satraplatin-related toxic effects was not observed.     

Phase I clinical trial of continuous infusion cyclopentenyl cytosine

Cyclopentenyl cytosine (CPE-C) is an investigational drug that is active against human solid tumor xenografts. The 5-triphosphate of CPE-C inhibits CTP synthase, and depletes CTP and dCTP pools. We conducted a phase I clinical trial of CPE-C given as a 24-h continuous i. v. infusion every 3 weeks in 26 adults with solid tumors. The starting dose rate, 1 mg/m² per h, was selected on the basis of both preclinical studies and pharmacokinetic data from two patients obtained after a test dose of 24 mg/m² CPE-C as an i. v. bolus. Dose escalation was guided by clinical toxicity. A total of 87 cycles were given, and ten patients received four or more cycles. The mean CPE-C steady-state plasma levels (Cpss) increased linearly from 0.4 M to 3.1 M at dose levels ranging from 1 to 5.9 mg/m² per h (actual body weight); the mean total body clearance was 146±38 ml/min per m². CPE-C was eliminated by both renal excretion of intact drug and deamination to cyclopentenyl uracil in an apparent 21 ratio. CTP synthase activity in intact bone marrow mononuclear cells was inhibited by 58% to 100% at 22 h compared to matched pretreatment samples at all CPE-C dose levels. When all data were combined, flux through CTP synthase was decreased by 89.6%±3.1% at 22h (mean ± SE,n=16), and remained inhibited by 67.6%±7.7% (n=10) for at least 24 h post-CPE-C infusion. Granulocyte and platelet toxicities were dose-dependent, and dose-limiting myelosuppression occurred during the initial cycle in two of three patients treated with 5.9 mg/m² per h. Four of 11 patients (4 of 20 cycles) who received 4.7 mg/m² per h CPE-C experienced hypotension 24–48 h after completion of the CPE-C infusion during their first (n=2), third (n=1) and sixth cycles (n=1), respectively. Two of these patients died with refractory hypotension despite aggressive hydration and cardiopulmonary resuscitation. One of 12 patients (28 total cycles) treated with 3.5 mg/m² per h CPE-C experienced orthostatic hypotension during cycle 1, and this patient had a second episode of orthostatic hypotension at a lower dose (3.0 mg/m²per h). Hypotension was not seen in patients receiving 2.5 mg/m² per h CPE-C. The occurrence of hypotension did not directly correlate with either CPE-C Cpss, CPE-U plasma levels, pretreatment cytidine plasma levels, baseline CTP synthase activity, or with the degree of enzyme inhibition during treatment. While the hypotension appeared to be dose-related, its unpredictable occurrence and the uncertainty concerning the mechanism preclude a recommendation of a tolerable dose for future studies.     

Pharmacokinetics of 5-fluorouracil infusions in the rat: Comparison with man and other species

Summary Saturable elimination of 5-FU is exhibited in rats during constant infusions. Over the range of 3–480 mg/m²/h, total-body clearance of 5-FU decreases from 600 ml/min/m² to less than 90 ml/min/m². Previously published values for catabolism of 5-FU by rat hepatocytes can be used to simulate the plasma concentrations of 5-FU that were measured over this range of infusions. The qualitative pattern of nonlinear pharmacokinetics for 5-FU is similar in rats, dogs, monkeys, and humans. However, there are major quantitative differences in total-body clearance values, expressed in terms of surface area (ml/min/m²) or as a fraction of cardiac output. Rat and monkey have substantially lower 5-FU clearance values than dog and man. Although 5-FU clearance values were similar in dogs and humans, total body clearance values for thymidine are 18-fold higher in humans than in dogs. The selection of an appropriate animal model to pursue the clinical observations of high total body clearance of pyrimidines remains uncertain.     

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 (C_max) and the area under the concentration-time curve (AUC) and a linear correlation between the dose and both C_max (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.Supported by the Associazione Italiana per la Ricerca sul Cancro (A.I.R.C.)     

The effect of food on oral melphalan absorption

Summary Fifteen patients receiving oral melphalan (4.2–5.3 mg/m²) for a variety of neoplastic disorders were studied. Ten patients received the drug on separate occasions, with and without a standardized breakfast. Eight of these patients also received an IV bolus dose (5 mg/m²) to determine bioavailability. Serial melphalan plasma samples were taken over 5 h after administration and assayed by high-performance liquid chromatography. The median area under the curve (AUC) when taken fasting was 179 (range 95–336) ng · h · ml^-1, and when taken with food, 122 (47–227) ng · h · ml^-1, the median reduction being 39% (P0.01). In one patient, who died before completing the study, the drug was not detectable at all after being taken with food. In the eight patients who were also given IV melphalan, the median terminal melphalan half-life (57 min, range 38–71) was no different from its oral half-life [55 (27–104) min fasting; 55 (30–72) min with food] (P>0.1). In these patients bioavailability was 85% (26–96)% when the drug was taken fasting and 58% (7–99)% when taken with food (P0.025). Median clearance following IV administration was 362 ml/min/m² (range 104–694). It was found that the melphalan level in a single plasma sample drawn 1.5 h after administration was highly predictive of oral melphalan AUC (r_s=0.915, P0.1). This study suggests that to ensure optimum absorption of the drug, melphalan should not be taken with food.     

Pharmacokinetics of carboplatin administered with lobradimil to pediatric patients with brain tumors

Purpose To determine the pharmacokinetics of adaptively dosed carboplatin when administered in combination with the bradykinin agonist, lobradimil (RMP-7, Cereport), to pediatric patients with brain tumors.Methods Carboplatin pharmacokinetic studies were performed on 21 of 25 children with primary brain tumors who received carboplatin and lobradimil on two consecutive days every 28 days in a phase I dose-escalation trial of lobradimil. Carboplatin was adaptively dosed, based on the radioisotopic glomerular filtration rate (GFR) to achieve a target plasma area under the concentration vs time curve (AUC) of 3.5 mgmin/ml per dose ×2 (2.5 mgmin/ml per dose ×2 in patients with prior craniospinal radiation or myeloablative chemotherapy). The adaptive dosing formula was: carboplatin dose (mg/m²)=target AUC (mgmin/ml) × [0.93 × GFR (ml/min/m²)+15]. Carboplatin was infused over 60 min (n=15) or 15 min (n=6). The 10-min lobradimil infusion (100–600 ng/kg ideal body weight) began 5 min before the end of the carboplatin infusion. Frequent blood samples were drawn over 24 h after the first dose of carboplatin/lobradimil. Ultrafilterable platinum was measured by atomic absorption spectroscopy, and the AUC of ultrafilterable platinum was derived using the linear trapezoidal rule and extrapolated to infinity.Results The median GFR was 65 ml/min/m² (range 38–95 ml/min/m²) and the median carboplatin doses for the 2.5 and 3.5 mg min/ml target AUCs were 154 and 276 mg/m²/day (124–235 and 179–360 mg/m²/day), respectively. The measured carboplatin AUC exceeded the target AUC in all 21 patients by a median of 35% (range 0.2–131%). The median carboplatin AUCs at the 2.5 and 3.5 mgmin/ml target AUCs were 3.4 and 4.8 mgmin/ml (2.51–5.8 and 3.9–7.7 mgmin/ml), respectively. Carboplatin clearance was lower than values previously reported in children and correlated poorly with GFR (r²=0.14).Conclusions Adaptive dosing of carboplatin based on GFR overestimated the dose required to achieve the target carboplatin AUC in pediatric patients with brain tumors treated with concurrent lobradimil. The degree to which the measured carboplatin AUC exceeded the target AUC appeared to be greater at higher doses of lobradimil, suggesting that the failure of the adaptive dosing method was related to an unexpected pharmacokinetic drug interaction.     

Phase II study of carboplatin in recurrent ovarian cancer: severe hematologic toxicity in previously treated patients

Summary Carboplatin (CBDCA) is a second-generation cisplatin analog that has shown activity in early clinical trials. Its spectrum of toxicity is quantitatively and qualitatively different from that of the parent compound. Between November 1984 and September 1986 we conducted a phase II trial of CBDCA in 46 women with epithelial ovarian cancer. All patients had undergone at least one prior chemotherapy regimen; 41 (89%) had previously received cisplatin (mean cumulative dose, 540 mg/m²). The CBDCA dose was based on renal function and was injected i. v. once every 4 weeks. Patients were stratified on the basis of baseline creatinine clearance: those with a baseline creatinine clearance of 60 ml/min received 400 mg/m² CBDCA; those with a creatinine clearance between 30 and 60 ml/min received an initial dose calculated according to a previously published formula [2, 3] that corrected for renal insufficiency and projected nadir platelet counts of 75,000/mm³. Of 41 evaluable patients, 6 (15%) had an objective response [2 complete responses (CRs); 4 partial responses (PRs)]; 5 of the 6 responders had previously responded to cisplatin treatment. No responses were observed in 12 patients who had not responded to prior cisplatin therapy. Significant hematologic toxicity was seen. Of 18 patients with a creatinine clearance of 60 ml/min (dose, 400 mg/m²), 6 had nadir platelet counts of <25,000/mm³, 4 with symptomatic bleeding. Of the 21 evaluable patients for whom the dose-modification formula was applied, 10 had nadir platelet counts of <75,000/mm³; 5 had counts of <50,000/mm³. CBDCA has activity even in patients who have previously undergone extensive cisplatin therapy; however, its toxicity is variable and thrombocytopenia is dose-limiting. We did not confirm the ability of the above-mentioned formula to calculate the CBDCA dose and accurately predict the nadir platelet count for all patients. Other factors, such as prior radiotherapy, may also be important in the dosing of CBDCA in pretreated patients.Supported in part by a grant from Bristol Myers Company Pharmaceutical Research and Development Division, CRU CA 16087 and CRU-96.N. Colombo is the recipient of a fellowship from the American Italian Foundation for Cancer Research.     

Pharmacokinetics of high-dose etoposide after short-term infusion

Summary The pharmacokinetics of high-dose etoposide (total dose, 2100 mg/m² divided into three doses given as 30-min infusions on 3 consecutive days) were studied in ten patients receiving high-dose combination chemotherapy followed by autologous bone marrow transplantation. In addition to etoposide, all subjects received 2×60 mg/kg cyclophosphamide and either 6×1,000 mg/m² cytosine arabinoside (ara-C), 300 mg/m² carmustine (BCNU), or 1,200 mg/m² carboplatin. Plasma etoposide concentrations were determined by²⁵²Cf plasma desorption mass spectrometry. In all, 27 measurements of kinetics in 10 patients were analyzed. According to graphic analysis, the plasma concentration versus time data for all postinfusion plasma ctoposide values were fitted to a biexponential equation. The mean values for the calculated pharmacokinetic parameters were:t1/2, 256±38 min; mean residence time (MRT), 346±47 min; AUC, 4,972±629g min ml^–1 (normalized to a dose of 100 mg/m²); volume of distribution at steady state (Vd_ss), 6.6±1.2l/m²; and clearance (CL), 20.4±2.4 ml min^–1 m^–2. A comparison of these values with standard-dose etoposide pharmacokinetics revealed that the distribution and elimination processes were not influenced by the dose over the range tested (70–700 mg/m²). Also, the coadministration of carboplatin did not lead to significant pharmacokinetic alterations. Although plasma etoposide concentrations at the time of bone marrow reinfusion (generally at 30 h after the last etoposide infusion) ranged between 0.57 and 2.39 g/ml, all patients exhibited undelayed hematopoietic reconstitution.     

Phase I and pharmacokinetics studies of prochlorperazine 2-h i.v. infusion as a doxorubicin-efflux blocker

In an earlier phase I study, we reported that the maximal tolerated dose (MTD) of prochlorperazine (PCZ) given as a 15-min i.v. infusion was 75 mg/m². The highest peak plasma PCZ concentration achieved was 1100 ng/ml. The present study was conducted to determine if PCZ levels high enough to block doxorubicin (DOX) efflux in vitro could be achieved and sustained in vivo by increasing the duration of i.v. infusion from 15 min to 2 h. The treatment schedule consisted of i.v. prehydration with at least 500 ml normal saline (NS) and administration of a fixed standard dose of 60 mg/m² DOX as an i.v. bolus over 15 min followed by i.v. doses of 75, 105, 135, or 180 mg/m² PCZ in 250 ml NS over 2 h. The hematologic toxicities attributable to DOX were as expected and independent of the PCZ dose. Toxicities attributable to PCZ were sedation, dryness of mouth, anxiety, akathisia, hypotension, cramps, and confusion. The MTD of PCZ was 180 mg/m². Large interpatient variation in peak PCZ plasma levels (91–3215 ng/ml) was seen, with the plasma half-life (t1/2) being approximately 57 min in patients given 135–180 mg/m² PCZ. The volume of distribution (V_d), total clearance (Cl_T), and area under the curve (AUC) were 350.1±183.8 l/m², 260.7±142.7 l m² h^–1 and 1539±922 ng ml h^–1, respectively, in patients given 180 mg/m² PCZ and the respective values for patients receiving 135 mg/m² were 48.9±23.76 l/m², 33.2±2.62 l m² h^–1, and 4117±302 ng ml h^–1. High PCZ plasma levels (>600 ng/ml) were sustained in all patients treated with 135 mg/m² PCZ for up to 24 h. DOX plasma elimination was biphasic at 135 and 180 mg/m² PCZ, and a>10-ng/ml DOX plasma level was maintained for 24 h. Partial responses were seen in three of six patients with malignant mesothelioma, in two of ten patients with non-small-cell lung carcinoma, and in the single patient with hepatoma. Our data show that PCZ can be safely given as a 2-h infusion at 135 mg/m² with clinically manageable toxicities. The antitumor activity of the combination of DOX and PCZ needs to be confirmed in phase II trials.This work was supported by NIH grant R01 CA-29360 and S1488, CRC grant M01 RR-05280, and the Joan Levy Cancer Foundation. This paper was presented at the meeting of the American Association for Cancer Research, Orlando, Florida, May 19–22, 1993     

Cisplatin disposition in children and adolescents with cancer

Summary The disposition of cisplatin was evaluated in 28 children and adolescents with cancer, as part of a phase II clinical trial. Patients received either 30 mg/m² (11) or 90 mg/m² (17) of cisplatin as a 6-h IV infusion. Serum samples and divided urine collections were obtained over 48 h following completion of the cisplatin infusion, and were assayed in duplicate for total platinum by atomic absorption spectrophotometry. Serum samples obtained up to 4 h after three cisplatin infusions were assayed for parent (free) cisplatin following ultrafiltration. The mean (±SE) elimination half-life of free cisplatin in serum was 1.3 (±0.4) h. Serial serum concentrations of total platinum following 90 mg/m² dosages were adequately described by a biexponential equation. The mean (±SE) serum T_1/2 of total platinum was 0.42 (±0.10) h and the mean (±SE) T_1/2 was 44.43 (±8.24) h. The intercompartment distribution rate constants of a two-compartment kinetic model indicate extensive tissue accumulation of total platinum, with a rate of transport into tissue compartments (K₁₂) that is about six times the rate of transport out of tissues (K₂₁). The mean (±SE) renal clearance of total platinum from 0–3 h was 37.36 (±11.96) ml/min/m² and 35.8 (±13.6) ml/min/m² for the 30 mg/m² and 90 mg/m² groups, respectively. This value decreased to 3.25 (±0.94) and 2.16 (±0.4) ml/min/m² for the two groups by the 6–12 h interval, and remained between 1 and 3 ml/min/m² for the duration of the observation period. The ratio of total plantinum clearance to creatinine clearance decreased significantly(P<0.05) beginning 3 h post-infusion. The change in renal clearance of total platinum is apparently a function of two independent first-order processes for renal clearance of parent drug and cisplatin metabolites.     

Pharmacokinetic study of indicine N-oxide in pediatric cancer patients

Summary Pharmacokinetics of the experimental antitumor agent indicine N-oxide were investigated in a group of 23 pediatric cancer patients. Plasma elimination of indicine N-oxide was best described by a two-compartment open model. The mean plasma distribution phase half-life, plasma elimination phase half-life, and plasma clearance were 8 min, 84 min, and 62 ml/min/m² (2.1 ml/min/kg), respectively. One patient with renal impairment had an abnormally long plasma elimination phase half-life (275 min) and reduced plasma clearance (17 ml/min/m²). Plasma elimination phase half-life values increased and plasma clearance values decreased with increasing age of the pediatric patients. Plasma elimination of indicine N-oxide was more rapid in this group of children than in adults who had previously received the drug.