Multiple-dose pharmacokinetics of epirubicin at four different dose levels: studies in patients with metastatic breast cancer

Summary Pharmacokinetic analysis of epirubicin and its metabolites epirubicinol and 7-deoxy-13-dihydro-epirubicinol aglycone during the first and the fourth courses of treatment was performed in 78 patients with metastatic breast cancer. The patients were treated every 3 weeks with epirubicin given as 10-min i.v. infusions at four different dose levels: 40, 60, 90 and 135 mg/m². In most cases (76 of 78 cases), plasma concentration-time curves fitted to a three-compartmental pharmacokinetic model. The terminal half-life of epirubicin was independent of dose and duration of treatment. Large interindividual differences were demonstrated (meant _1/2, 21.6±7.9 h; range, 10.6–69 h;n=110). In two subjects, extremely long half-lives and high serum bilirubin concentrations indicated impaired liver function. No correlation was found between the half-life and levels of liver alanine aminotransferase (ALAT) or serum creatinine. The metabolite epirubicinol appeared quickly after epirubicin administration and its half-lives were shorter than that of the parent compound (meant _1/2, 18.1±4.8 h; range, 8.2–38.4 h;n=105).Formation of the aglycone metabolite was delayed and the half-life of this metabolite was shorter than that of epirubicin (meant _1/2, 13±4.6 h; range, 2.7–29 h;n=104). The AUC of epirubicin and the total AUC (drug and metabolites) were linearly proportional to the dose, with the former value constituting two-thirds of the latter. A correlation was found between AUC and the plasma concentration of epirubicin at two time points (2 and 24 h after administration). The proposed model was AUC=9.44×c ₂+62.5×c ₂₄+157.7 (r=0.953).This work was supported by the Lundbeck Foundation, the Michaelsen Foundation and Farmitalia Carlo Erba Ltd.     

Methotrexate and 6-mercaptopurine maintenance therapy for childhood acute lymphoblastic leukemia: dose adjustments by white cell counts or by pharmacokinetic parameters?

In a consecutive study of 14 boys and 17 girls with non-B-cell ALL who were 1 year of age at diagnosis, the degree of myelosuppression during the last year of MTX/6MP maintenance therapy was analyzed in relation to the erythrocyte concentration of MTX polyglutamates and 6-thioguanine nucleotides (E-MTX and E-6TGN, the respective major cytotoxic metabolites of MTX and 6MP). For each patient, E-MTX and E-6TGN levels were measured 2–15 (median, 6) and 2–17 (median, 7) times, respectively. From these measurements, arithmetic means of E-MTX and E-6TGN were calculated (mE-MTX and mE-6TGN, respectively). Since MTX and 6MP probably work synergistically, the product of mE-MTX and mE-6TGN was calculated for each patient (mE-MTX×6TGN). The degree of myelosuppression was registered as the mean WBC determined following cessation of the therapy minus the mean WBC measured during the therapy (mWBC_shift). The mean WBCs measured on therapy (mWBC_on) and off therapy were highly correlated (r=0.48,P=0.009). The median mWBC_shift was 2.7×10⁹/l (range, 1.4–4.8×10⁹/l). In a multivariate regression analysis, the best-fit model to predict the mWBC_shift included mE-MTX×6TGN, age at drug withdrawal, and mWBC in the order given [mWBC_shift=4.3+0.00089×(mE-MTX×6TGN)–0.097×age–0.41×mWBC_on; globalr _s=0.66,P=0.0002]. Thus, the patients with higher mE-MTX×6TGN values, the younger patients, and the patients with the lowest WBC during therapy had the most pronouced degree of myelosuppression as measured by mWBC_shift. These results indicate that E-MTX and E-6TGN may give a better reflection of the treatment intensity than do the WBCs alone.Abbreviations ALL Acute lymphoblastic leukemia - CV coefficient of variation - dose-MTX/dose-6MP inean dose of MTX and 6MP, respectively, during the last year of therapy - dose MTX×6MP the product of dose-MTX and dose-6MP - E-MTX nmol MTX/mmol Hb in erythrocytes - E-6TGN nmol 6TGN/mmol Hb in erythrocytes - mE-MTX mean E-MTX - mE-6TGN mean E-6TGN - mE-MTX×6TGN the product of mE-MTX and mE-6TGN - 6MP 6-mercaptopurine - MTX methotrexate - mPLATE_off mean platelet count following cessation of therapy - mPLATE_on mean platelet count during the last year of therapy - mPLATE_shift change in mean platelet count following cessation of therapy - mWBC_off mean WBC following cessation of therapy - mWBC_on mean WBC during the last year of therapy - mWBC_shift change in mean WBC following cessation of therapy - WBC white blood cell count This paper presents data from a larger study that has received financial support from the Carl and Ellen Hertz Foundation, the Danish Cancer Society (grants 88-8502, 90-051, 91-048), the Foersom Foundation, the Gerda and Aage Haensch Foundation, Inner Wheel Denmark, and the Wille Heise Foundation.     

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.)     

Limited sampling models for simultaneous estimation of the pharmacokinetics of irinotecan and its active metabolite SN-38

Irinotecan (CPT-11) is a novel topoisomerase I inhibitor with clinical activity in human malignancies. The objective of this study was to develop efficient limited sampling models (LSMs) to estimate simultaneously the area under the plasma concentration versus time curves (AUC) for both CPT-11 and its active metabolite SN-38. A total of 64 pharmacokinetic sets (24-h sampling) were obtained in phase I studies at doses ranging from 50 to 750 mg/m² (0.5-h i.v. infusion). The patients were randomly assigned to a training data set (n=32) and a test set (n=32). Multiple linear regression analyses were used to determine the optimal LSMs based on the correlation coefficient (r), bias (MPE%, percentage of mean prediction error), and precision (RMSE%, percentage of root mean squared prediction error). Of these LSMs, the ones including maximal concentrations of CPT-11 (0.5 h, the end of the i.v. infusion) and metabolite SN-38 ( 1 h) were favored along with predictive precision and clinical constraints. Several bivariate models including a 6-h time point as the last sampling time (or 7 h) were found to be highly predictive of either the CPT-11 AUC or the SN-38 AUC. The chosen sampling time points were the ones that allowed the best compromise between the accurate determination of either compound alone with the same sampling times. The simultaneously best prediction of both CPT-11 and SN-38 AUCs was obtained with sampling time points harvested at 0.5, 1, and 6 h (or 7 h). With these sampling time points a trivariate model was selected for the determination of CPT-11 AUC namely, CPT-11 AUC (ng h ml^–1)=0.820×C_0.5h+0.402×C_1h+15.47 ×C_6h+928, and a corresponding model was selected for the determination of metabolite AUC, i.e., SN-38 AUC (ng h ml^–1)=4.05×C_0.5h–0.81×C_1h+23.01×C_6h–69.78, whereC(t) is the concentration in nanograms per milliliter of either compound at a given timet. These models performed well with the test data sets for CPT-11 AUC (r=0.98, MPE%=–1.4, RMSE%=13.9) and for SN-38 AUC (r=0.95, MPE%=–6.5, RMSE%=37.7). In addition to the determination of AUCs (and hence clearance), these models also allow the determination of the maximal concentrations of both compounds, which might be needed for pharmacodynamics studies. Other bi- and trivariate models including other time points are also presented. These LSMs not only will facilitate ongoing and future clinical trials by significantly reducing the number of blood samples needed for pharmacokinetics studies but will hopefully contribute to a better knowledge of pharmacokinetic-pharmacodynamic relationships for both CPT-11 and its active metabolite SN-38.Abbreviations CPT-11 (7-Ethyl-10-[4-(1-piperidino)-1-piperidino]-carbonyloxy-camptothecin - SN-38 7-ethyl-10-hydroxy-camptothecin - AUC area under the plasma concentration versus time curve - MPE% percentage of mean prediction error (bias) - RMSE% percentage root mean squared prediction error (precision) - MRT mean residence time - Vdss volume of distribution at steady state - CL total body clearance     

A limited sampling method for estimation of the carboplatin area under the curve

Summary A limited sampling method for estimation of the carboplatin area under the curve (AUC) from one or two plasma concentration determination is presented. The model was conceived and developed using 43 pharmacokinetic studies in 15 patients with ovarian cancer (model data set) who received carboplatin in combination with cyclophosphamide. Linear regression analyses comparing the AUC and the drug concentration at a single time point (0.25–10 h after the end of the infusion) as calculated from the fitted exponential equations gave correlation coefficients as high as 0.97, with maximal correlations falling within the interval of 2–3.25 h. The model was validated prospectively in 9 patients with ovarian cancer (validation data set) who received the same treatment as did the model data set (21 pharmacokinetic studies), testing the equation AUC=0.52×C_2.75h+0.92. Observed and estimated AUCs were correlated in the validation data set (r=0.91). The mean predictive error (MPE%±SE) was –4.4%±3.1% and the root mean squared error (RMSE%) was 13.9%. Multiple regression analysis revealed that adding a second sample drawn at 0.25 h (AUC=0.053×C_0.25h+0.401×C_2.75h+0.628) improved the MPE% to –2.2%±2.1% and the RMSE% to 9.4% (r=0.96). We conclude that the carboplatin AUC can be estimated from a single plasma sample at 2.75 h or, more precisely, from two plasma samples at 0.25 and 2.75 h. The methods described may prove to be a handy tool for the calculation of approximate AUCs in trials of a size that would discourage detailed pharmacokinetic studies.This work was supported by grants from the Lundbeck Foundation and the Danish Cancer Society     

Maintenance chemotherapy for childhood acute lymphoblastic leukemia: relation of bone-marrow and hepatotoxicity to the concentration of methotrexate in erythrocytes

Summary To explore the clinical significance of the concentration of methotrexate (MTX) in erythrocytes (E-MTX), 42 boys and 31 girls were studied during maintenance chemotherapy for childhood acute lymphoblastic leukemia for periods of 3–22 months (median, 8 months) at an unchanged dose of MTX. For each study period, a weighted mean of white cell counts (mWBC), absolute neutrophil counts (mANC), and serum aminotransferases (mAT) were calculated, using as weights the intervals from sampling until the next WBC, ANC, or AT determinations were done. In 17 patients who underwent at least six measurements of E-MTX during a period in which the MTX dose remained unchanged for up to 22-months, the median intraindividual coefficient of variation for E-MTX was 10% (range, 5%–22%). For each patient, a mean of all E-MTX values (mE-MTX) during a study period (range, 1–15 measurements; median, 3) was used as an index of the RBC accumulation of MTX at the prescribed dose of MTX. Among 42 patients receiving full-dose MTX (>17.5 mg/m²), the mE-MTX ranged between 3.4 and 9.6 nmol hemoglobin (Hb) (interindividual coefficient of variation, 33%). The mE-MTX was significantly related to the MTX dose (r=0.45,P=0.00003). The mWBC and mANC were both significantly related to the mE-MTX (mWBC:r=–0.31,P=0.004; mANC:r=–0.35,P=0.02), but not to the dose of MTX (mWBC:r=–0.08,P=0.25; mANC:r=–0.22,P=0.08). Each of four patients with a persistent rise in AT above the upper-normal limit (40 IU/I) and an mAT of >80 IU/I had an mE-MTX of >6.5 nmol/mmol Hb. Due to its low intraindividual variation, E-MTX may be useful for detecting persistent or intermittent failure of patient compliance. Its prognostic significance and its clinical value in MTX dose adjustment should be explored in prospective studies.This study was financially supported by the Rosalie Petersen Foundation     

The relative toxicity of intravenous and intraperitoneal doses of epirubicin

Summary The toxicity of single doses of the anthracycline epirubicin was compared in the rat after either the intravenous (i.v.: 2–6 mg/kg) or intraperitoneal (i.p.; 4–8 mg/kg) administration of the drug. These doses produced comparable acute toxicity that was characterised by a dose-dependent, transient reduction in body weight (<15%) in the first 2 weeks after drug administration. Sequential measurements of cardiac output in animals that received i.v. doses of epirubicin showed that the time-related changes in cardiac function were biphasic. There was an initial decline in cardiac output in the first 12 weeks, which was followed by a phase of persistent depression in cardiac output between 12 weeks and 20 weeks. The time-related changes in cardiac function after i.p. doses of the drug were more variable, although the trend of changes, as after i.v. administration, appeared to be dose-dependent. Recovery of cardiac function occurred at 20 weeks after an i.p. dose of 4 mg/kg; however, after 6 mg/kg, cardiac function was significantly depressed after 16 weeks. For both routes of administration, the likelihood of late cardiac complications was dependent on the level of the reduction in cardiac output at 12 weeks. A study of the impairment of cardiac output and the incidence of cardiac-related mortality demonstrated that epirubicin was more cardiotoxic after i.v. administration. Equivalent cardiotoxic doses of epirubicin after i.v. and i.p. administration were highly linearly correlated (r=0.998), although there appeared to be a threshold dose of 3.33 mg/kg after i.p. administration of the drug. Thus, the relative cardiotoxicity between the two routes of administration was found to be dependent on the drug dose and, hence, the level of effect. The difference in the effect was less for high drug doses. The LD₅₀ for deaths due to cardiotoxicity at 20 weeks was 4.42±0.42 mg/kg after i.v. administration, which was significantly lower than the value of 6.28±0.41 mg/kg obtained after i.p. administration of the drug (P<0.01). There was no qualitative difference in the histological lesions induced in the myocardium after the i.v. vs i.p. administration of epirubicin.     

Effects of verapamil on the pharmacokinetics and metabolism of epirubicin

Summary Experimental data suggest that multidrug resistance in cancer may be overcome by using an increased dose of anticancer agent(s) in combination with a resistance-modifying agent (RMA). We studied the pharmacokinetics and metabolism of both epirubicin (EPI) and verapamil (VPL) to explore the possible pharmacokinetic interactions between these two drugs. Ten patients with advanced breast cancer were given EPI (40 mg/m² in a daily i.v. bolus for 3 consecutive days), and five of them also received VPL (4×120 mg/daily p.o. for 4 consecutive days). The data indicated a significant interaction between these two drugs that affected their metabolism. The areas under the concentration-time curves (AUC) obtained for epirubicin glucuronide, epirubicinol glucuronide, and both of the 7-deoxy-aglycones were higher in the EPI+VPL group as compared with the EPI group. The AUC, terminal half-life, mean residence time, volume of distribution at steady state, and plasma clearance of EPI alone as compared with EPI+VPL did not differ significantly. These results suggest either an induction of enzymes necessary for drug metabolism or an increase in the liver blood flow, resulting in an enhanced generation of metabolites with time or in an inhibition of excretion processes. Comparisons of the AUC values obtained for EPI and its metabolites after the first, second, and third injections of EPI revealed a cumulative effect for the metabolites that was more pronounced in the EPI+VPL group, being significant (P<0.05) for epirubicin glucuronide in both treatment groups and for epirubicinol glucuronide in the EPI+VPL group. Maximal concentrations of VPL and nor-VPL reached 705±473 and 308±122 ng/ml, respectively, with the steady-state concentrations being 265±42 ng/ml for VPL and 180±12 ng/ml for nor-VPL.This study was supported by the Erich und Gertrud Roggenbuck-Stiftung zur Förderung der Krebsforschung (Hamburg). The anthracycline metabolites were kindly provided by Dr. A. Suarato (Farmitalia, Milano, Italy); nor verapamil was provided by Dr. Traugott (Knoll, Ludwigshafen, Germany)     

Epirubicin metabolism and pharmacokinetics after conventional- and high-dose intravenous administration: a cross-over study

In a pharmacokinetics study, six patients were treated i.v. with epirubicin (EPI) at the two dose levels of 60 and 120 mg/m², whereas a further six patients were treated at 75 and 150 mg/m². Both groups were studied according to a balanced cross-over design; the aim of the study was to assess the pharmacokinetic linearity of epirubicin given at high doses. Both the absolute goodness of fit and the Akaike Information Criterion (AIC) point to a linear, tricompartmental open model as the choice framework for discussing EPI plasma disposition after 16/24 administrations, independent of the delivered dose. After 8 treatments, the minimal AIC value corresponded to a nonlinear tissue-binding model. However, even in these cases, second-order effects were present only during the early minutes following treatment. In a model-independent framework, mean EPI plasma clearance was identical at the two dose levels of 60 and 120 mg/m² (65.4±8.0 vs 65.3±13.4 l/h,P=0.92). Both the mean residence time (MRT) and the volume of distribution at steady-state (V_ss) were similar as well (MRT: 22.6±2.9 vs 24.2±3.7 h;P=0.46; V_ss: 21.3±1.5 vs 22.6±6.5 l/kg,P=0.46). No statistically significant difference could be found in mean statistical-moment-theory parameters determined after 75- and 150-mg/m² EPI doses (plasma clearance, PICI: 83.4±13.5 vs 68.5±12.8 l/h,P=0.12; MRT: 22.6±4.8 vs 21.9±3.9 h,P=0.60; V_ss: 26.7±10.5 vs 21.2±7.0 l/kg,P=0.17). Analysis of variance also failed to reveal any significant correlation between dose and plasma clearance. However, when data relative to single patients were examined, a trend toward nonlinear drug distribution as well as a consequent increase in peripheral bioavailability could be observed in 4/6 patients of the 75-mg/m² vs the 150-mg/m² group. No significant dose-dependent variation was observed in the ratio between the molecular-weight-corrected areas under the concentration-time curve for the metabolites and those for EPI [60 vs 120 mg/m²: epirubicinol (EPIol), 0.23±0.10 vs 0.22±0.06,P=0.20; epirubicin glucoronide (G1), 0.46±0.14 vs 0.62±0.40,P=0.26; epirubicinol glucuronide (G2), 0.21±0.05 vs 0.30±0.16,P=0.06; and 75 vs 150 mg/m²: EPIol, 0.33±0.22 vs 0.32±0.19,P=0.42; G1, 0.51±0.23 vs 0.46±0.17,P=0.53; G2, 0.18±0.10 vs 0.22±0.10,P=0.34]. In conclusion, all the metabolic pathways seemed well preserved when the dose was doubled, and no evident sign of saturation kinetics could be found.     

Dose-toxicity relationship of carboplatin in combination with cyclophosphamide in ovarian cancer patients

Summary A study was undertaken to examine the relationships between carboplatin's pharmacokinetic parameters and the myelotoxicity associated with its administration in combination with cyclophosphamide. An additional aim of the study was to test the applicability of the method proposed by Calvert et al. for calculation of the carboplatin dose to be used in the combination regimen. A total of 24 previously untreated ovarian cancer patients were given a combination of 250–500 mg/m² carboplatin and 500 mg/m² cyclophosphamide every 4 weeks for 4 months. The pharmacokinetics of carboplatin and the associated myelotoxicity were investigated in 64 courses. The results showed a significant correlation (r=0.89) between the AUC calculated for carboplatin and that predicted according to Calvert's formula [carboplatin dose in milligrams=AUC (glomerular filtration rate +25)]. We conclude that the model is a useful guide in the calculation of the carboplatin dose to be given in combination with cyclophosphamide, and it enables a more precise prediction of the carboplatin exposure than does the conventional calculation, which is based on milligrams of drug per square meter of body surface. The AUC for carboplatin was a reliable predictor of the myelotoxicity as measured by the relative decrease in thrombocyte count. However, the relationship between AUC and myelotoxicity changed during the treatment because of increasing bone marrow toxicity. Despite this finding, dose calculation based on carboplatin's AUC appears to provide an improvement in the clinical use of the drug, and the method also seems to be fully applicable in combination chemotherapy with cyclophosphamide.Supported by grants from the Lundbeck Foundation and the Danish Cancer Society     

Pharmacokinetics and pharmacodynamics of prolonged oral etoposide in women with metastatic breast cancer

The pharmacokinetics and pharmacodynamics of prolonged oral etoposide chemotherapy were investigated in 15 women with metastatic breast cancer who received oral etoposide 100 mg as a single daily dose for up to 15 days. There was considerable interpatient variability in the day 1 pharmacokinetic parameters: area under the plasma concentration time curve (AUC) (0–24 h) 1.95±0.87 mg/ml per min (mean ± SD), apparent oral clearance 60.9±21.7 ml/min per 1.73 m², peak plasma concentration 5.6±2.5 g/ml, time to peak concentration 73±35 min and half-life 220±83 min. However, intrapatient variability in systemic exposure to etoposide was much less with repeated doses. The intrapatient coefficient of variation (CV) of AUC for day 8 relative to day 1 was 20% and for day 15 relative to day 1 was 15%, compared to the day 1 interpatient CV of 45%. Neutropenia was the principal toxicity. Day 1 pharmacokinetic parameters were related to the percentage decrease in absolute neutrophil count using the sigmoidal E_max equation. A good fit was found between day 1 AUC and neutrophil toxicity (R ²=0.77). All patients who had a day 1 AUC>2.0 mg/ml per min had WHO grade III or IV neutropenia. The predictive performance of the models for neutrophil toxicity was better for AUC (percentage mean predictive error 5%, percentage root mean square error 18.1%) than apparent oral clearance, peak plasma concentration, or daily dose (mg/m²). A limited sampling strategy was developed to predict AUC using a linear regression model incorporating a patient effect. Data sets were divided into training and test sets. The AUC could be estimated using a model utilizing plasma etoposide concentration at only two time points, 4 h and 6 h after oral dosing (R ²=98.9%). The equation AUC_pr=–0.376+0.631×C_4h+0.336×C_6h was validated on the test set with a relative mean predictive error of –0.88% and relative root mean square error of 6.4%. These results suggest monitoring of AUC to predict subsequent myelosuppression as a strategy for future trials with oral etoposide.Division of Haematology and Medical Oncology, Peter MacCallum Cancer Institute, Locked Bag 1, A'Beckett St, Melbourne 3000, Australia     

Ifosfamide/etoposide and mesna uroprotection in advanced breast cancer

The object of the study was to evaluate the effectiveness of ifosfamide/etoposide and mesna therapy in advanced breast cancer. A total of 44 patients with breast cancer were included in the trial. Eligibility criteria included measurable, refractory disease; prior anthracycline therapy (or its contraindication); a life expectancy of at least 3 months; and adequate hepatic, renal, CNS and bone marrow function. All patients were70 years of age and had a Karnofsky performance status of50%. There were 36 evaluable cases. Sites of metastatic disease included bone (19), skin (18), liver (9), lung (14), lymph node (19), and miscellaneous (7). Treatment consisted of 1,500 mg/m² ifosfamide given i.v. on days 1–5, 120 mg/m² etoposide given i.v. on days 1–3, and 400 mg i.v. mesna given with and at 4 and 8 h after ifosfamide. Cycles were repeated every 28 days. Initial doses were reduced by 25% or 50% in patients who had previously undergone both chemotherapy and radiotherapy. A median of 4 cycles (range, 2–8) were given. The myelotoxicity was marked: WHO grades 3/4 leukopenia (n=37), grades 3/4 thrombocytopenia (n=12), and grades 2/3 anemia (n=13). Due to myelotoxicity, dose reduction or prolongation of treatment-free intervals was necessary in 28 cases. Alopecia was seen in 35 patients and CNS toxicity, in 8. Partial remission (PR) was obtained in five cases and complete remission (CR), in three. Sites of response included the lung (5), skin (4), lymph node (5), and peritoneum (1). The duration of response was 4 (n=2) and 8 (n=1) months for CR and 2 (n=2), 6 (n=2), and 10 (n=1) months for PR. We conclude that the ifosfamide/etoposide and mesna regimen is effective, but its myelotoxicity is treatment-limiting.Presented at the Satellite Symposium Ifosfamide in Gynecological Tumors of the 5th European Conference on Clinical Oncology and Cancer Nursing, London, September 3–7, 1989     

Gender affects doxorubicin pharmacokinetics in patients with normal liver biochemistry

We studied the variability in doxorubicin pharmacokinetics in 27 patients, all of whom had normal liver biochemistry tests. Blood samples were collected after the first cycle of single-agent doxorubicin given as an i.v. bolus and plasma levels were measured by high-performance liquid chromatography (HPLC). The relationship of doxorubicin clearance (dose/AUC) with biochemical tests (AST, bilirubin, alkaline phosphatase, albumin, creatinine) and physical characteristics (age, gender, height, weight, tumour type) was investigated. The 6 men had a significantly higher doxorubicin clearance than did the 21 women (median values, 59 and 27 lh^–1 m^–2, respectively;P=0.002). Doxorubicin clearance was significantly lower in patients with breast cancer than in those with other tumours (median values, 26 and 53 lh^–1 m^–2, respectively;P=0.0008). The other biochemical and physical parameters did not correlate with doxorubicin clearance. However, in multivariate analysis, gender was the only factor predicting doxorubicin clearance (r ²=40%). The ratio of the AUCs for doxorubicinol and doxorubicin (R) was higher in the men than in the women (median values, 0.62 and 0.36, respectively;P=0.03). We conclude that gender may be an important determinant of doxorubicin clearance in patients with normal liver biochemistry.     

A phase I trial of trimetrexate glucuronate (NSC 352122) given every 3 weeks: clinical pharmacology and pharmacodynamics

Summary Trimetrexate glucuronate (TMTX), a non-classic folate antagonist, has been evaluated clinically on several schedules. We studied TMTX given as an i.v. bolus over 5–30 min every 3 weeks in 44 patients with advanced solid tumors; it was given at doses ranging from 20 to 275 mg/m². The maximal tolerated dose (MTD) on this schedule is 220 mg/m², which we also recommend as a starting dose for phase II studies in patients without extensive prior therapy. Because of wide individual differences in drug tolerance, dose escalation in 25% increments is recommended for non-toxic patients. The principal dose-limiting toxicity was myelosuppression, although in some patients a flu-like syndrome precluded dose escalation. Significant rash and mucositis also frequently occurred in toxic patients. TMTX plasma concentrations were measured after the first dose and the data were fit by two-or three-compartment mammillary pharmacokinetic models. The TMTX clearance rate was 36.5±21 ml/min per m² and did not change with dose; non-linearities with increasing dose were apparent in the steady-state volume of distribution (V_SS) and in the terminal disposition half-life (t 1/2). The difference between pre-treatment and nadir leucocyte counts was correlated with TMTX dose (r=0.58; P=0.0006) and with the area under the concentration vs time curve (AUC) (r=0.41; P=0.02). Pre-treatment plasma albumin concentrations correlated weakly with the nadir white blood count (r=-0.36; P=0.047). Optimal schedules for the administration of TMTX have not been established and phase II trials using both bolus and daily x5 schedules are under way.Supported in part by NCI Contract, NCI-CM-47663     

Pharmacokinetic study of fludarabine phosphate (NSC 312887)

Summary Characterization of the pharmacokinetics of 2-FLAA has been completed in seven patients receiving 18 or 25 mg/m² daily x5 of 2-FLAMP over 30 min. Assuming 2-FLAMP was instantaneously converted to 2-FLAA, the plasma levels of 2-FLAA declined in a biexponential fashion. Computer fitting of the plasma concentrationtime curves yielded an average distribution half-life (t1/2) of 0.60 h and a terminal half-life (t1/2) of 9.3 h. The estimated plasma clearance was 9.07±3.77 l/h per m² and the steady state volume of distribution, 96.2±26.0 l/m². There was a significant inverse correlation between the area under the curve (AUC) and absolute granulocyte count (r=-0.94, P<0.02). A relationship between creatinine clearance and total body clearance was noted, but was not statistically significant (r=0.828; P<0.1). Aproximately 24%±3% of 2-FLAA was excreted renally over the 5-day course of drug administration.Abbreviations used 2-FLAA-9--D arabinofuranosyl-2-fluoroadenine - 2-FLAMP the 5'-monophosphate of 2-FLAA, also known as fludarabine phosphate - AUC area under the curve - AGC absolute granulocyte count - TPC total plasma clearance - Vd_ss volume of distribution at steady state - Vd volume of distribution - Creat Cl creatinine clearance - SGOT serum glutamic-oxaloacetic transaminase - WBC peripheral white blood cell count This study was supported by contract NCI N01-CM-27542, NIH grant RR-01346 and by the VA Research Service.     

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.     

High-dose thiotepa and melphalan with hemopoietic progenitor support following induction therapy with epirubicin-paclitaxel-containing regimens in metastatic breast cancer (MBC).

Background:Preliminary data from phase III randomized studieshave failed to show benefit of HDC given as consolidation after anthracyclineand alkylating-based chemotherapy in metastatic breast cancer (MBC).Moderate activity of induction regimens and selection of chemoresistant clonesare among the possible reasons for these disappointing results. We thereforehave designed a phase II study where high-dose alkylating agents are given asconsolidation after an induction treatment including the most active agents(epirubicin and paclitaxel) without alkylating agents. Patients and methods:Patients with MBC not previously treatedwith chemotherapy for metastatic disease were eligible. After six courses ofepirubicin–paclitaxel · gemcitabine patients received a courseof thiotepa 600 mg/m² + melphalan 160 mg/m² withhemopoietic support. Pharmacokinetic parameters of thiotepa and melphalan weremeasured and related to treatment outcomes. The L-VEF of the patients wasmonitored before and after treatment. Results:Forty-eight patients have been treated. Before HDC 14patients were in CR, and 34 in PR. A median of 6.92 · 10⁶(range 1.53–16.6) CD34+ cells/kg were reinfused after HDC. Median days(range) to neutrophils >0.5 · 10⁹/l and platelets>20,000 · 10⁹/l were 9.5 (9–33) and 10 days(9–32), respectively. Symptomatic CHF was observed in two patients(4.1%). C_max and AUC of thiotepa showed a linearrelationship with time to progression (TTP) and overall survival (OS):r ² = 0.6. After HDC the conversion rate from PR to CR was44.1%. At five years progression-free and overall survival ratesare 37.5% and 65%, respectively. A treatment-related death wasobserved. Conclusions:High-dose thiotepa and melphalan after anepirubicin–paclitaxel-containing treatment is feasible, devoid ofsignificant cardiotoxicity and very active. Pharmacokinetic parameters ofhigh-dose thiotepa might be linked to treatment outcome.     

Phase I clinical and pharmacokinetic study of cyclophosphamide administered by five-day continuous intravenous infusion

Summary A total of 14 patients, 7 male and 7 female, received in all 21 evaluable courses of cyclophosphamide administered by 5-day continuous infusion. Cyclophosphamide doses were escalated from 300 to 400 mg/m² per day for 5 days and repeated every 21–28 days. The patient population had a median age of 55 years (range 38–76) and a median Karnofsky performance status of 80 (range 60–100). Only 1 patient had not received prior therapy; 5 patients had received only prior chemotherapy, 1 had received only prior radiotherapy, and 7 had received both. Tumor types were gastric (1), lung (2), colon (4), urethral adenocarcinoma (1), cervical (2), chondrosarcoma (1), melanoma (1), uterine leiomyosarcoma (1), and pancreatic (1). The dose-limiting toxicity was granulocytopenia, with median WBC nadir of 1700/l (range 100–4800) in 8 heavily pretreated patients treated at 350 mg/m² per day for 5 days. One patient without heavy prior treatment received two courses at 400 mg/m² and had WBC nadirs of 800/l and 600l. WBC nadirs occurred between days 9 and 21 (median 14). Drug-induced thrombocytopenia occurred in only one patient (350 mg/m² per day, nadir 85000/l). Neither hyponatremia nor symptomatic hypoosmolality was observed. Radiation-induced hemorrhagic cystitis may have been worsened in one patient. Nausea and vomiting were mild. Objective remissions were not observed. The maximum tolerated dose for previously treated patients is 350 mg/m² per day for 5 days. This dose approximates the doses of cyclophosphamide commonly used with bolus administration. Plasma steady-state concentrations (Css) of cyclophosphamide, measured by gas liquid chromatography, were 2.09–6.79 g/ml. Steady state was achieved in 14.5±5.9 h (mean ±SD). After the infusion, cyclophosphamide disappeared from plasma monoexponentially, with a t^1/2 of 5.3±3.6 h. The area under the curve of plasma cyclophosphamide concentrations versus time (AUC) was 543±150 g/ml h and reflected a cyclophosphamide total-body clearance (CL_TB) of 103±31.6 ml/min. Plasma alkylating activity, assessed by p-nitrobenzyl-pyridine, remained steady at 1.6–4.3 g/ml nor-nitrogen mustard equivalents. Urinary excretion of cyclophosphamide and alkylating activity accounted for 9.3%±7.6% and 15.1%±2.0% of the administered daily dose, respectively. The t^1/2 and AUC of cyclophosphamide associated with the 5-day continuous infusion schedule are similar to those reported after administration of cyclophosphamide 1500 mg/m² as an i.v. bolus. The AUC of alkylating activity associated with the 5-day continuous infusion of cyclophosphamide is about three times greater than the AUC of alkylating activity calculated after a 1500-mg/m² bolus dose of cyclophosphamide. Daily urinary excretions of cyclophosphamide and alkylating activity associated with the 5-day continuous infusion schedule are similar to those reported after bolus doses of cyclophosphamide.     

Pharmacogenetics of adjuvant breast cancer treatment with cyclophosphamide,epirubicin and 5-fluorouracil

Purpose

Most adjuvant breast cancer treatment regimens include the combination of an anthracycline (epirubicin or doxorubicin) and the alkylating agent cyclophosphamide. This study sought to investigate the influence of pharmacogenetics on the pharmacokinetics and metabolism of these agents.

Methods

Blood samples were taken from patients treated with cyclophosphamide (n = 51) and epirubicin (n = 35), with or without 5-fluorouracil (5-FU). The pharmacokinetics and metabolism of the three drugs were investigated, together with pharmacogenetic investigations for cyclophosphamide and epirubicin. Cyclophosphamide and its metabolites and also epirubicin and epirubicinol were measured in plasma. DNA was extracted from whole blood and genotyping performed using RT-PCR.

Results

Patients with at least one variant CYP2C19*17 allele had a longer CP half-life (p = 0.007), as did homozygous variants for the CYP2B6*6 allele. There was no significant effect of GSTP1, CYP2B6*2, CYP2B6*5 or CYP2C19*2 on any pharmacokinetic parameter of CP. An NQO2 exonic SNP was associated with a higher exposure to epirubicinol relative to epirubicin (p = 0.011). Other polymorphic variants of NQO1, carbonyl reductase, UGT enzymes and transporters had no influence on epirubicin or its metabolite.

Conclusion

Overall, pharmacogenetic factors had only a minor influence on cyclophosphamide or anthracycline-based adjuvant therapy of breast cancer.     

The pharmacokinetics of the quinazoline antifolate ICID 1694 in mice and rats

Summary N-(5-[N-(3,4-Dihydro-2-methyl-4-oxoquinazolin-6-ylmethyl)-N-methylamino]-2-thenoyl)-l-glutamic acid (ICI D1694) is an analogue of the thymidylate synthase inhibitorN ¹⁰-propargyl-5,8-dideazafolic acid (CB3717). CB3717 was found to be an active anticancer agent in early clinical studies, but its use was limited by its relative insolubility at physiological pH. ICI D1694 has been shown to be a more active anticancer agent than CB 3717 in model systems, and it is devoid of the acute renal toxicity associated with the administration of the latter drug to mice. In the present study, the pharmacokinetics of ICI D1694 were studied in both mice and rats using reverse-phase HPLC. In rats, ICI D1694 clearance (CL) conformed to a two-compartment open model and was rapid (CL=10.7 ml min^–1 kg^–1,t1/2=30 min). Excretion was mainly biliary (65% of the delivered dose in 4 h vs 12% in urine) in the rat following a 100-mg/kg i.v. bolus. A high degree of protein binding was seen in rat plasma (90% over the range of 20–100 m). In mice, ICI D1694CL=27 ml min^–1 kg^–1 andt1/2=30 min following 100 mg/kg i.v., which was significantly faster than CB3717 clearance (CL=6 ml min^–1 kg^–1,t1/2=93 min). ICI D1694 was fully bioavailable following i.p. administration (AUC=3.73 mg ml^–1 min i.v. 4.03 mg ml^–1 min i.p.), but its bioavailability following oral administration appeared to be low (approximately 10%–20%). Tissue distribution and excretion studies in mice suggested that biliary excretion predominated, confirming the results obtained in rats. Following an i.v. dose of 500 mg/kg ICI D1694 in mice, drug was detectable at 24h, suggesting the presence of a third phase of plasma clearance. The initial HPLC assay could not detect this third phase following a dose of 100 mg/kg; hence, a more sensitive assay was developed that includes a solid-phase extraction step. The latter assay was used to define the third phase of ICI D1694 clearance in mice, and preliminary studies demonstrated a terminal half-life of 6.5±2.7 h.These studies were supported by the UK Cancer Research Campaign and the British Technology Group