Relationship between plasma adriamycin levels and the outcome of remission induction therapy for acute nonlymphocytic leukemia

Doxorubicin uptake in ascitic lymphoma model: resistance or curability is governed by tumor cell density and prolonged drug retention

Background/Aims: Chemotherapy resistance of malignancies is a universal phenomenon which unfavorably affects therapeutic results. Genetic adaptations as well as epigenetic factors can play an important role in the development of multidrug resistance. Cytotoxic drug content in plasma of cancer patients is known to variate up to one hundred-fold regardless of the same dose injected per m² body surface. The relationship between plasma concentrations, tissue uptake, and chemotherapy response is not completely understood. The main objective of this study was to investigate how the identical dose of Doxorubicin (Dox) can result in a different therapeutic response pattern depending on tumor size. Study Design: The study was performed on ascitic EL4 lymphoma in an exponential growth phase focusing on the rapidly changing tumor susceptibility to the Dox treatment. Well distinguishable tumor response patterns (curability, remission-relapse, resistance) were selected to unveil Dox intratumoral uptake and drug tissue persistence. Intratumoral Dox content within peritoneal cavity (PerC) in conjunction with systemic toxicity and plasma pharmacokinetics, were monitored at several time points following Dox injection in tumor bearing mice (TBM) with differing patterns of response. Results: Following intraperitoneal (i.p.) transplantation of 5x10⁴ EL4 lymphoma cells rapid exponential proliferation with ascites volume and animal mass increase resulted in median survival of 14.5 days. The increase in tumor cell mass in PerC between day 3 and day 9 was 112.5-fold (0.2±0.03 mg vs 22.5±0.31 mg respectively). However, tumors at this time interval (day 3 to day 9 post-transplantation) were relatively small and constituted less than 0.05% of animal weight. An identical dose of Dox (15 mg/kg) injected intravenously (i.v.) on Day 3 lead to a cure whereas a TBM injected on day 9 exhibited resistance with a median survival time no different from the untreated TBM control. Injection of Dox resulted in noticeable differences of cellular uptake in PerC between all three groups of TBM ("cure", relapse", "resistance"). Larger tumors were consistently taking up less Dox 60 min after the 15 mg/kg i.v. bolus injection. Higher initial uptake resulted also in longer retention of drug in PerC cells. The area under the concentration curve in PerC cells AUC_0-10d was 8.2±0.57 µg/g x h, 4.6±0.27 µg/g x h and 1.6±0.02 µg/g x h in "cure", "relapse" and "resistance" TBM respectively (p<0.05 "relapse" vs "cure" and p<0.001 "resistance" vs "cure"). No differences in plasma Dox pharmacokinetics or systemic hematological effects were observed in TBM following a single i.v. Dox push. Hematologic nadir was tested on day 2 and subsequent hematologic recovery was evaluated on day 10 following Dox administration. Hematologic recovery on day 10 coincided with complete drug efflux from PerC and rising tumor cell numbers in PerC of "relapse" TBM. Myelosuppression and hematological recovery patterns were identical in all surviving animal groups regardless of the tumor size on the day of Dox injection. Conclusions: Within a few days of exponential tumor growth, an identical dose of Dox produced dramatically different responses in the TBM with increasing resistance. Systemic toxicity and plasma pharmacokinetics were indistinguishable between all TBM groups. Initial uptake in tumor cells was found to be consistently lower in larger tumors. Drug uptake in tumor cells was regulated locally - a phenomenon known as inoculum effect in vitro. The duration of drug retention in cells was directly related to initial cellular uptake. The magnitude of Dox cellular retention could potentially play a role in determining tumor remission and relapse.

Prognostic significance of leukopenia during the induction phase in adult B cell acute lymphoblastic leukemia

The association between chemotherapy-induced leukopenia and clinical outcome has been reported for several types of cancer. The objective of the current study was to evaluate the association of chemotherapy-induced leukopenia during the induction phase with the clinical outcome of adult B cell acute lymphoblastic leukemia (B-ALL). Fifty-one cases of B-ALL, age ≥14 years, were reviewed. The variables under consideration included age, sex, the initial white blood cell (WBC) count (WBC-0), as well as the WBC counts on days 8 (WBC-8), 15 (WBC-15), and 22 (WBC-22) during induction therapy, early bone marrow responses on day 15 during induction therapy, immunophenotype, and cytogenetics. Univariate analysis revealed that WBC-15 ≥0.40×10⁹/L was significantly associated with inferior event-free survival (EFS) (hazard ratio [HR]=2.95, P=0.004) and overall survival (OS) (HR=2.92, P=0.015). On multivariate analysis, high WBC-15 (≥0.40×10⁹/L) remained an independent prognostic factor for EFS (HR=3.29, P=0.014) and OS (HR=3.29, P=0.038). Our results suggested that WBC-15 may contribute to refinements in the current risk stratification algorithms for adult B-ALL.

Inverse relationship between leukaemic cell burden and plasma concentrations of daunorubicin in patients with acute myeloid leukaemia

AIMS

It has been shown that the cellular uptake and cytotoxicity of anthracyclines decrease with increasing cell density in vitro, an event termed 'the inocculum effect'. It is not known whether such an effect occurs in vivo. In this study the relationships between white blood cell (WBC) count, plasma and cellular concentrations of daunorubicin (DNR) in patients with acute myeloid leukaemia were investigated.

METHODS

Plasma and mononuclear blood cells were isolated from peripheral blood from 40 patients with acute myeloid leukaemia at end of infusion (time 1 h), 5 and 24 h following the first DNR infusion. DNR concentrations were determined by high-pressure liquid chromatography and related to the WBC count at diagnosis. A population pharmacokinetic model was used to estimate the correlations between baseline WBC count, volume of distribution and clearance of DNR.

RESULTS

A clear but weak inverse relationship between the baseline WBC count and plasma concentrations of DNR (r(2)=0.11, P<0.05) at time 1 was found. Furthermore, a clear relationship between baseline WBC count and DNR central volume of distribution using population pharmacokinetic modelling (dOFV 4.77, P<0.05) was also noted. Analysis of plasma DNR and the metabolite daunorubicinol (DOL) concentrations in patients with a high WBC count support that the low DNR/DOL concentrations are due a distribution effect.

CONCLUSION

This study shows that the leukaemic cell burden influences the plasma concentrations of anthracyclines. Further studies are needed to explore if patients with high a WBC count may require higher doses of anthracyclines.

Uptake of anthracyclines in vitro and in vivo in acute myeloid leukemia cells in relation to apoptosis and clinical response

AIMS

To study anthracycline-induced apoptosis in leukemic cells isolated from patients with acute myelogenous leukemia (AML) in vitro and to compare intracellular anthracycline concentrations causing apoptosis in vitro with those obtained in vivo during anthracycline treatment.

METHODS

Mononuclear blood cells from AML patients were isolated before (n = 20) and after anthracycline infusion (n = 24). The pre-treated cells were incubated in vitro with daunorubicin (DNR) and/or idarubicin (IDA). Anthracycline concentrations were determined by high-performance liquid chromatography, and apoptosis was detected by propidium iodine staining using a flow cytometer.

RESULTS

There was a clear concentration-response relationship between intracellular anthracycline levels and apoptosis albeit with a large interindividual variation. Intracellular levels >1200 muM always led to high apoptosis development (>60%) in vitro. The intracellular concentrations of DNR in vivo (n = 24) were more than tenfold lower than the concentrations needed to induce effective apoptosis in vitro, although a significant relation between in vivo concentrations and clinical remission was found. We also found a significant relation between apoptosis induction in leukemic cells by IDA in vitro and clinical remission.

CONCLUSIONS

Our results indicate that intracellular anthracycline levels in vivo are suboptimal and that protocols should be used that increase intracellular anthracycline levels.

Doxorubicin pharmacokinetics is correlated to the effect of induction therapy in children with acute myeloid leukemia

We studied the pharmacokinetics of doxorubicin in 41 children treated for newly diagnosed acute myeloid leukemia. Doxorubicin, 75 mg/m2 body surface area, was administered by constant i.v. infusion over 8 h. Four children with Down's syndrome (DS), 1.2-2.3 years old, had a median total body clearance of 523 ml/min/m2. The median clearance in non-DS children, 0.6-1.8 years old (n = 4) and 2.5-17.7 years old (n = 33), was 446 and 538 ml/min/m2, respectively. Patients who went into complete remission (CR) after induction therapy had a significantly higher median plasma concentration of doxorubicin than those who did not, 249 compared with 180 ng/ml, respectively (P = 0.036; analysis restricted to non-DS patients). Doxorubicin plasma concentration was an independent factor for CR, both in univariate (P = 0.031) and multivariate analysis including sex, age and white blood cell count at diagnosis (P = 0.021). Patients who reached CR had a significantly lower doxorubicin clearance than those who did not, 513 and 657 ml/min/m2, respectively (P = 0.017). In conclusion, doxorubicin plasma concentration and total body clearance during up-front treatment were correlated to the effect of induction therapy. Prospective studies should be performed to confirm the concentration-effect relationship and explore the possibility of therapeutic monitoring.

The effect of age on the early disposition of doxorubicin

PURPOSE

Clinical studies indicate that anthracycline cardiotoxicity increases with patient age. This may be due to altered pharmacokinetics or pharmacodynamics. A parameter termed 'early clearance' has been shown to decrease with age in patients receiving intravenous doxorubicin. This parameter, as defined, has no immediate relationship to any physiologically based pharmacokinetic parameter. We therefore reevaluated the pharmacokinetic data to better define the relationship between doxorubicin disposition and patient age.

METHODS

Four studies provided a total of 56 patients with evaluable pharmacokinetics. The volume of the central compartment, V(c), the distribution clearance, CL(d), and total body clearance, CL, were determined for each patient and regressed against age. A physiologically based pharmacokinetic (PBPK) model for doxorubicin was also used to evaluate the effects of age on doxorubicin disposition. Published blood flows associated with various patient ages were used to simulate plasma and tissue doxorubicin concentrations. The relationship between CL(d) and initial tumor regression was also evaluated.

RESULTS

No correlation was found between V(c) and age ( P>0.05). A highly significant correlation was observed between CL(d) and age ( P<0.0005) and there was a mild but significant relationship between CL and age ( P<0.01). Use of the PBPK model with different age-related blood flows yielded virtually identical parameter values to the clinical data analyzed. Furthermore, relative tissue AUCs simulated in old and young patients compared well with those reported for daunorubicin disposition in young and old rats. In addition, a linear relationship was observed between initial tumor regression and CL(d).

CONCLUSIONS

Initial concentrations of doxorubicin following intravenous administration are higher in the elderly due to a decrease in CL(d) rather than in V(c). On the basis of simulations with the PBPK model, the reduced CL(d) appears to be related to altered regional blood flows in the elderly, and such changes may be of clinical significance.

Epirubicin in patients with liver dysfunction: development and evaluation of a novel dose modification scheme

This study aimed to develop an epirubicin dose modification scheme in women with breast cancer and liver dysfunction. We first identified target areas under the concentration-time curve (AUCs) of 2400 and 1600 ng/ml.h from pharmacokinetic studies in 15 women with normal liver tests. In a second group of 16 women with abnormal liver biochemistry, the relationship between raised asparate aminotransferase (AST) and epirubicin clearance was: dose=AUC (97.5-34.2xlog AST). Adaptive dosing was evaluated prospectively in a third group of 41 women with serum AST > or =2xnormal+/-raised bilirubin. The median AUCs were 2444 and 1608 ng/ml.h, close to the high and low target AUCs, respectively. Variability in AUC was lower with adaptive dosing than in a fourth group given an unadjusted dose of epirubicin (coefficient of variation=25.8, 30.0 and 46.5%, respectively; P=0.06). Epirubicin dosing based on AST is safe and may reduce pharmacokinetic variability.

Pharmacokinetic-pharmacodynamic relationships of the anthracycline anticancer drugs

The anthracycline glycoside antibiotics represent a group of potent anticancer agents with a wide spectrum of activity against solid tumours and haematological malignancies, and are the mainstay of a large number of clinical protocols for the treatment of adult and childhood neoplastic diseases. Their clinical activity is limited, however, by acute and chronic adverse effects. Myelosuppression, predominantly neutropenia and leucopenia, is the dose-limiting toxicity; in addition to this, mucositis, nausea, vomiting and alopecia are frequent, whereas hepatopathy, characterised by elevated bilirubin concentrations, occurs less frequently. Cardiotoxicity is a major adverse effect of the anthracycline antibiotics and can be acute or chronic; in the acute setting, electrocardiographic abnormalities may be seen, including ST-T elevations and arrhythmias, but chronic cardiotoxicity represents a serious adverse effect that may be lethal due to the development of irreversible, cumulative dose-dependent, congestive cardiomyopathy. The occurrence of toxicity displays a marked interindividual variation, and for this reason the pharmacokinetics and pharmacodynamics of anthracyclines have been extensively investigated in order to identify integrated models that can be used in the clinical setting to prevent the development of serious toxicity, mainly leucopenia, and maximise tumour exposure. Pharmacokinetics has been recognised to influence both the toxicity and the activity of anthracyclines; in particular, there is increasing evidence that the mode of administration plays an important role for cumulative cardiotoxicity and data indicate that bolus administration, rather than continuous infusion, appears to be an important risk factor for anthracycline-induced cardiomyopathy, thus implying that this type of toxicity is maximum concentration-dependent. On the contrary, exposure to the drug, as measured by area under the curve, seems best related to the occurrence of leucopenia. Finally, the development of pharmacokinetic-pharmacodynamic models allows the simulation of drug effects and ultimately dose optimisation in order to anticipate important toxicities and prevent their occurrence by the administration of prophylactic treatments.

Pharmacokinetics of doxorubicin in children with acute lymphoblastic leukemia: multi-institutional collaborative study

BACKGROUND

In adults, it has been shown that the pharmacokinetics of doxorubicin are highly variable, despite standardization of the dose based on body surface area (BSA). The purpose of this study was to determine the plasma concentrations of doxorubicin and its active metabolite doxorubicinol in children treated for acute lymphoblastic leukemia (ALL).

PROCEDURE

Children, 107 in number, aged 1.3-17.3 years, were studied at Day 1 of induction therapy according to the current Nordic protocol. Five infants, 3-9 months old, were also included. Plasma samples were drawn 23 hr after the start of a 24-hr infusion of doxorubicin 40 mg/m(2), and analyzed by reversed-phase liquid chromatography.

RESULTS

There was a more than 10-fold difference between patients in dose normalized plasma concentration of doxorubicin, median 62.8 ng/ml, range 22.6-334 ng/ml. The doxorubicin concentrations differed significantly between age groups (P = 0.003). Children aged 4-6 years had the highest doxorubicin concentrations, median 77.9 ng/ml, followed by 2-4-year-old children, median 64.3 ng/ml. Both younger and older children had median values of about 50 ng/ml. Patients with white blood cell (WBC) count > 50 x 10(9)/L at diagnosis had significantly lower doxorubicin concentrations, median 55.3 ng/ml, than those with WBC count < 10 x 10(9)/L, median 64.4 ng/ml (P = 0.015). There was no difference in doxorubicin concentration between boys and girls. No correlation was found between doxorubicin levels and serum aminotransferases or serum creatinine. The concentration of doxorubicinol was 13% (median value) of that of doxorubicin. Four infants, 7-9 months old, had plasma clearance between 350-431 ml/min/m(2), which is in the same range as in older children. A 3-month-old infant had a clearance of 181 ml/min/m(2).

CONCLUSIONS

The age groups who had the highest doxorubicin concentrations, (2-) 4-6-year-old children, are known to make up a large proportion of standard risk ALL cases with good prognosis. The correlation between doxorubicin plasma levels and clinical effect needs further study. The influence of age, body composition, and tumor burden on the pharmacokinetics of antineoplastic drugs should also be further explored, aiming at improvements in the current dosing regimen based on BSA.

Dose-adjusted EPOCH chemotherapy for untreated large B-cell lymphomas: a pharmacodynamic approach with high efficacy

We hypothesized that incremental improvements in the cyclophosphamide-doxorubicin-vincristine-prednisone (CHOP) chemotherapy regimen through optimization of drug selection, schedule, and pharmacokinetics would improve outcome in patients with large B-cell lymphomas. A prospective multi-institutional study of administration of etoposide, vincristine, and doxorubicin for 96 hours with bolus doses of cyclophosphamide and oral prednisone (EPOCH therapy) was done in 50 patients with previously untreated large B-cell lymphomas. The doses of etoposide, doxorubicin, and cyclophosphamide were adjusted 20% each cycle to achieve a nadir absolute neutrophil count below 0.5 x 10(9)/L. The median age of the patients was 46 years (range, 20-88 years); 24% were older than 60 years; and 44% were at high-intermediate or high risk according to International Prognostic Index (IPI) criteria. There was a complete response in 92% of patients, and at the median follow-up time of 62 months, the progression-free survival (PFS) and overall survival (OS) rates were 70% and 73%, respectively. Neither IPI risk factors nor the index itself was associated with response, PFS, or OS. Doses were escalated in 58% of cycles, and toxicity levels were tolerable. Significant inverse correlations were observed between dose intensity and age for all adjusted agents, and drug clearance of doxorubicin and free etoposide was also inversely correlated with age (r = -0.54 and P(2) =.08 and r = -0.45 and P(2) =.034, respectively). Free-etoposide clearance increased significantly during successive cycles (P(2) =.015). Lymphomas with proliferation of at least 80% had somewhat lower progression and those expressing bcl-2 had significantly higher progression (P(2) =.04). Expression of bcl-2 may discriminate the recently described activated B-like from germinal-center B-like large-cell lymphomas and provide important pathobiologic and prognostic information. Dose-adjusted EPOCH may produce more cell kill than CHOP-based regimens. Dynamic dose adjustment may overcome inadequate drug concentrations, particularly in younger patients, and compensate for increased drug clearance over time.

Effects of anti-neoplastic agents on the recovery of bacteria and yeasts in an automated blood culture system

The effects of 7 anti-neoplastic agents on the recovery of 5 aerobic gram-positive cocci, gram-negative rods and yeasts were studied in 2 different automated blood culture systems using an experimental model. In the absence of anti-neoplastic agents, the growth of gram-positive cocci was detected significantly earlier in standard than in FAN aerobic bottles. In the presence of 100 microM doxorubicin, however, the growth of gram-positive cocci was totally inhibited in standard culture conditions, while in FAN bottles the agent has no inhibitory effect. Etoposide at a concentration of 100 micromol/l also significantly delayed the growth of cocci in standard conditions. Neither the culture bottles nor the anti-neoplastic agents tested had any effect on the growth of gram-negative rods and yeasts. The results suggest that the anti-neoplastic agents present in blood might disturb the growth of gram-positive cocci in blood culture. This should be considered when validating blood culture systems and evaluating blood cultures of chemotherapy-receiving febrile patients.

A comparative pharmacokinetic study of doxorubicin and 4'-epi-doxorubicin in children with acute lymphocytic leukemia using a limited sampling procedure

Antraquinone glycosides are an important class of antineoplastic drugs, frequently used for treatment of a variety of malignancies in children. Doxorubicin (Dox) is the most frequently used drug within this class of antineoplastics. 4'-epi-doxorubicin (Epi), a Dox isomer, was developed with the aim of reducing risks for fatal heart toxicity observed with Dox. The aim of the present study was to investigate the pharmacokinetics of Dox and Epi in children with acute lymphocytic leukemia. In total 31 patients (13 females and 18 males; median age 5.4 years; range 0.73-15.3 years) were studied using a simplified sampling procedure. The pharmacokinetic differences of the two drugs were established by their simultaneous administration. The plasma pharmacokinetics of neither Dox nor Epi correlated with the age of the patients. There were no gender differences in dose-normalized maximum concentrations of neither Dox nor of Epi. The inter-patient variation of the dose-normalized maximum concentrations of Dox and Epi is larger among females than among males. The Cmax ratio Dox/Epi was 1.39+/-0.19 (mean +/- SD). The pharmacokinetic differences of Dox and Epi in children, although less pronounced than in adults, are still of a magnitude that might be of clinical importance.

Benefits of pharmacological knowledge in the design and monitoring of cancer chemotherapy

Prescribing chemotherapy is a difficult task, because of drug resistance, which prevents all tumors to respond to a given protocol and because of drug toxicity, which is generally unavoidable but which must be limited to acceptable levels. The therapeutic window of anticancer drugs is very narrow and clinicians have to try to optimize the individual doses and schedules of the drugs to be administered. They can rely upon simple anthropometric features, such as body weight or surface area; they can also take into account the physiological status of the patient: age, liver and kidney function, genetic characteristics of drug metabolism, etc. The best way for dose adaptation lies in the establishment of pharmacokinetic/pharmacodynamic relationships, i.e., between the behavior of a drug in the body and its efficacy and toxicity. When it is established that the optimal effect of a drug is related to a given parameter, such as the area under the curve plotting plasma concentration vs. time (AUC), it becomes possible to administer the drug with the dose allowing to obtain the target parameter value. Individual dose adaptation can be achieved thanks to the study of the pharmacokinetics of a test dose preceding that of the therapeutic dose, or by the measure of drug plasma levels, either at steady state during a protracted infusion, or from cycle to cycle during repetitive protocols. Population analysis now allows the adaptation of anticancer drug dosing from a minimum knowledge of individual pharmacokinetic features, together with other characteristics of the patients such as age, gender or physiological functions.

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 (r2 = 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.

Individual dose adaptation of anticancer drugs

The dose of anticancer drugs is currently adjusted to the patient body surface area, although patients have different abilities to clear anticancer drugs. The dose adjustment to physiological functions permits major toxic accidents to be avoided. The adjustment to tumour drug content is considered, but for ethical or technical reasons, it cannot be used routinely The best criterion for the dose adjustment seems to be drug plasma concentration. The relationship between plasma concentration and efficacy may not be excellent, since it depends on the presence of resistant cells and on the blood flow through the tumour. A relationship between plasma concentration and/or the area under the curve (AUC) with toxicity has been reported with all major anticancer drugs. Different methods of dose adjustment to the drug plasma concentration are reported. In conclusion, dose adjustment to the drug plasma concentration or to the AUC can improve the chemotherapy efficacy, while reducing toxicity.

Epirubicin in hepatocellular carcinoma: pharmacokinetics and clinical activity

The pharmacokinetics and clinical activity of epirubicin were investigated in 16 patients with hepatocellular carcinoma (HCC) who received epirubicin at 75 mg/m2; the drug was given intravenously to 7 patients and via the hepatic artery to 9 patients (7 of whom also underwent embolisation). Lignocaine (1 mg/kg) was also given intravenously to 15 patients, and the metabolite monoethylglycinexylidide (MEGX) was measured as an indicator of liver function. Epirubicin clearance correlated with serum aspartate aminotransferase (AST), albumin and bilirubin values in patients treated intravenously or intraarterially. Although the route of administration did not affect the median total plasma clearance of epirubicin, early- and intermediate-phase clearance was higher following intraarterial administration. MEGX levels correlated with serum bilirubin levels but there was no correlation with albumin or AST values or epirubicin clearance. The rate of response to epirubicin was 3/13 (23%; 95% confidence interval, 8%-50%). Intravenous epirubicin was tolerated well, but intraarterial treatment was associated with significant morbidity. These data confirm that although current recommended dose adjustments are based primarily on serum bilirubin levels, altered epirubicin pharmacokinetics correlate more strongly with AST and albumin values than with serum bilirubin concentrations. However, at this dose and schedule, epirubicin has only modest activity against HCC.

The synergistic and antagonistic effects of cytotoxic and biological agents on the in vitro antitumour effects of suramin

Suramin has shown antitumour activity in vitro and in vivo. At plasma levels higher than 200 microM there is, however, excessive toxicity. We have, therefore, attempted to improve the antitumour effects of suramin in vitro by combining it with several other antitumour agents. The MCF-7 mammary carcinoma and PC3 prostate cancer cell lines were exposed continuously to suramin and the other agents for 6 days. The sulphorhodamine B (SRB) assay was used for the assessment of growth inhibition. The dose-response interactions were evaluated using the median-effect analysis with the Chou and Talalay computer programme. In the MCF-7 cell line, the combination of suramin plus doxorubicin (DXR), cisplatin (CDDP), 5-fluorouracil (5-FU) or tumour necrosis factor (TNF) resulted in synergistic growth inhibition, whilst its combination with miltefosine (HPC) was antagonistic. In the PC-3 cell line, suramin plus CDDP or TNF was synergistic, whilst its combination with DXR, 5-FU and HPC was antagonistic. All tested combinations with interferon-alpha (IFN-alpha), interferon-gamma (IFN-gamma) and with the combination of both IFN-alpha+IFN-gamma were not synergistic. The synergistic effect of suramin with DXR was schedule dependent. Pretreatment (addition of DXR on day 1 and suramin on days 2-5) was additive at the IC50 level, in both cell lines. Addition of DXR at day 5 was more effective than simultaneous exposure. We found a synergistic effect for the combination of suramin with CDDP and TNF in both cell lines. In addition the combination with DXR and 5-FU was synergistic in MCF-7. Sequential administration of DXR-suramin or suramin-DXR increased the growth inhibition.

Clinical pharmacokinetics of epirubicin: the importance of liver biochemistry tests

The influence of liver biochemistry tests on epirubicin pharmacokinetics has been investigated in 52 women with advanced breast cancer, 27 of whom had radiologically proven liver metastases. Patients received epirubicin 12.5-120 mg m-2 given as an i.v. bolus. Epirubicin levels were measured by HPLC following the first cycle of treatment. Epirubicin elimination, expressed as clearance (dose/AUC), in the 22 patients with normal AST and bilirubin was compared with that of 30 patients with a raised AST +/- raised bilirubin. Epirubicin clearance was significantly reduced in the patients with a raised AST, whether their serum bilirubin was normal (22 patients) or elevated (eight patients). In the 30 patients with a raised AST +/- raised bilirubin, epirubicin clearance correlated strongly with the level of AST (r = -0.72) but not with serum bilirubin, alkaline phosphatase, albumin or creatinine. Using a multiple regression analysis, AST was the only one of these biochemical variables predictive of epirubicin clearance (r2 = 0.47, P = 0.0006). We conclude that a raised serum AST is a more sensitive and reliable measure of abnormal epirubicin pharmacokinetics than increased bilirubin. These findings have implications for anthracycline treatment in patients with abnormal liver biochemistry.

A phase II study of high dose epirubicin in unresectable non small cell lung cancer

Epirubicin (EPI), a doxorubicin analogue, is reported to have equal antitumour activity with lower cardiac and systemic toxicity. Recently, the maximum tolerated dose of this drug has been revised upwards with reported increased response rates in several malignancies. We initiated a phase II study of high-dose EPI as initial treatment for patients with advanced non-small cell lung cancer (NSCLC) (stage III and IV). Between May 1988 and November 1989, 25 patients were entered. The starting dose of EPI was 135 mg m-2, with dose attenuations and escalations of 15 mg m-2 based on mid-cycle evaluation of toxicity. Treatment was repeated every 3 weeks. Nine partial responses (36%, 95% CI: 18-57.5%) and 11 patients with disease stabilisation (44%) were observed. Median (range) time to progression was 19 (3-70) weeks. Median (range) survival is 32 (9-116+) weeks. There were no treatment related deaths. Major side effects were leukocytopenia WHO grade III/IV (23% of courses) and mucositis WHO grade II/III (15% of courses). In two patients left ventricular ejection fraction decreased greater than 15% compared to baseline values after a cumulative Epirubicin dose of 435 mg m-2, and therefore went off study. In none of the patients clinical signs of congestive heart failure were observed. We conclude from our data that high-dose EPI, contrary to previous negative studies using lower doses of EPI, ranks amongst the most active regimens against advanced NSCLC. Toxicity of high-dose EPI is moderate. Further evaluation of this compound in combination regimens is recommended.

Disposition of epirubicin and metabolites with repeated courses to cancer patients

Thirteen cancer patients were studied following a total of 41 courses of epirubicin (EPI) (38-50 mg.m-2, mean 49.2 mg.m-2, administered by a 60 min infusion), together with other cancer chemotherapeutic agents. The aim was to consider the disposition of EPI and metabolites following subsequent courses as it has been reported that doxorubicin (the 4'-epimer parent of EPI) clearance is increased following the first administration. We have observed that EPI-glucuronide accounted for a mean 78.0%, epirubicinol 0.2% and epirubicinol-glucuronide 19.3% and that parent EPI accounted for only 2.4% of the EPI-compounds measured (mean of all patients and courses) for the 3 h period immediately following the infusion. These data confirm the rapid metabolism of EPI and the dominance of the glucuronidation metabolite pathway (which is not available to doxorubicin) and are compared with the metabolite profile observed in other reports. Large inter- and intra-individual variability in area under the plasma concentration/time curve were observed with no clear evidence of any consistent directional trend for such fluctuations, suggesting that factors contributing to EPI disposition are multivariate.

Biphasic effects of doxorubicin on the calcium release channel from sarcoplasmic reticulum of cardiac muscle

To define the mechanism of doxorubicin cardiotoxicity, the effects of doxorubicin and caffeine were examined on calcium release channels from cardiac sarcoplasmic reticulum. We found that calcium release from cardiac sarcoplasmic reticulum vesicles was induced by both compounds. When sarcoplasmic reticulum vesicles were incorporated into planar lipid bilayers, calcium-permeable channels were observed. Addition of caffeine (2.5-10 mM) increased channel open probability from less than 0.1% to 40%, and this effect persisted for a mean of 44 minutes. In contrast, doxorubicin (2.5-10 microM) had a biphasic effect; initially, doxorubicin activated the channel, whereas after a mean of 8 minutes, the channel became irreversibly inhibited. Although the degree of channel activation by doxorubicin was concentration dependent, the time needed to inactivate the channel was concentration independent. Pretreatment with dithiothreitol (0.2 mM) prevented doxorubicin-induced channel inactivation, and channel activity persisted for an average of 58 minutes. Dithiothreitol alone did not alter channel open probability. Our results support the hypotheses that 1) the integrity of sulfhydryl groups is important for some aspects of calcium release channel function and 2) activation and inactivation of the channel are separable processes. The biphasic effect of doxorubicin on channel function may also correspond to the clinically observed adverse effects of doxorubicin, a widely used chemotherapeutic agent that, after prolonged usage, causes a dilated cardiomyopathy.

Metabolism of epirubicin to glucuronides: relationship to the pharmacodynamics of the drug

In pharmacokinetic studies of epirubicin, we observed that its main metabolite, epirubicin glucuronide, presented a marked interpatient variation. It was even possible to separate the patients into two groups: those with a high epirubicin glucuronide:epirubicin plasma ratio and those with a low ratio, with few patients in between. We retrospectively analyzed the clinical files of 48 patients who had been subjected to a pharmacokinetic study of epirubicin. We observed that those with a low epirubicin glucuronide:epirubicin ratio had significantly lower plasma levels of fibrinogen and alpha 2-globulins, suggesting that a reduced glucuronidation of epirubicin could be associated with hepatocellular insufficiency. These patients also had significantly lower percentages of change in granulocytes after therapy and responded better to the course of treatment studied. We cannot presently propose a hypothesis to explain these observations.

Effect of cyclophosphamide pretreatment on daunorubicin in rat acute leukaemia model

The total number of leukaemic cells at the time of therapy may affect the tissue and target cell distribution and antitumour efficacy of cytotoxic drugs. The effects of low dose cyclophosphamide pretreatment on daunorubicin concentrations in leukaemic bone marrow were investigated in rats. At day 12 after transplantation of the leukaemia, rats were injected intraperitoneally with cyclophosphamide (30 mg/kg). 2 days later the leukaemic rats received daunorubicin intravenously (7.5 mg/kg). Cyclophosphamide pretreatment led to a significant increase in daunorubicin concentration in the femoral bone marrow, by a factor of about 7. The log leukaemic stem cell kill (LCK) values, as estimated by a survival assay, were 1.8, 0.7, and 5.4 for the leukaemic rats injected with cyclophosphamide (day 12), with daunorubicin (day 14), or with cyclophosphamide (day 12) plus daunorubicin (day 14), respectively). The simultaneous administration of cyclophosphamide and daunorubicin at day 14, induced a LCK of 2.7, a value that was the sum of the LCKs of cyclophosphamide and daunorubicin alone. Low-dose cyclophosphamide pretreatment led to an increased daunorubicin accumulation in femoral bone marrow of leukaemic rats, and was synergistic with daunorubicin.

Anthracycline pharmacokinetics. Limited sampling model for plasma level monitoring with special reference to epirubicin (Farmorubicin)

A new principle for plasma level monitoring of the anthracyclines doxorubicin and epirubicin is presented. The area under the plasma concentration time curve (AUC) is linearly correlated with the maximum plasma concentration of the drugs at the end of 2 and 4 hours' constant rate infusions. From this relationship it is possible to obtain accurate estimates of the AUC values of the drugs in the individual patients from plasma samples, withdrawn during the last 15 minutes prior to the completion of the infusions. The limited sampling model for drug monitoring of doxorubicin and epirubicin described here is robust and simple to use. It does not require a strict time control for the withdrawing of samples. Measured maximum plasma concentrations of epirubicin during 2 hours' constant rate infusions of 70 mg m-2 to patients with lymphoma (median age: 46.5 years) were within the range 171-404 ng ml-1 (median value: 265 ng ml-1).

Pharmacokinetics of doxorubicin in man: dose and schedule dependence

Doxorubicin serum elimination kinetics were measured by HPLC in three different patient groups. A dose of (a) 30 mg/m2; (b) 50 mg/m2, and (c) 4 x 15 mg/m2 every 10 h was administered by bolus injection to (a) 10, (b) 6, and (c) 8 patients. The results obtained provided strong evidence for a nonlinear dependence of doxorubicin serum elimination on the dose and administration schedule used. Comparing the 15 and 30 mg/m2 dose there was no significant increase in early drug levels but a marked increase in terminal half-life. At doses higher than 30 mg/m2, however, there was a steep increase in early drug levels, too. Moreover a marked cumulation of the anthracycline in the central compartment following short-term (4 x 15 mg/m2 every 10 h) consecutive administration was found. To obtain an optimal concentration x time product by single bolus injection a dose equal or higher than 30 mg/m2 should be used. However, in this dose range a steep dose-dependent rise in early drug levels is to be expected. As early high serum levels correlate with congestive heart failure, administration schedules reaching effective concentration x time products without high peak levels such as continuous infusion or consecutive administration of low doses seem to be necessary.

Pharmacology of adriamycin: the message to the clinician

In attempting to describe the human pharmacology of ADR, one is aware of the gaps in our knowledge and shortcomings of the available data. Nevertheless, such information is essential if we are ever to be able to convert rationally in vitro observations into clinical pharmacologic effect or, as is more often the case, explain why the desired effect has not been produced. Clinical pharmacokinetic studies to-date suggest that there is a clear relationship between ADR blood levels and toxicity. No such relationship between ADR blood levels and therapeutic response has been shown. The 7-deoxyaglycone tissue metabolites of ADR, which also appear in blood, may be more closely related to ADR cardiotoxicity and therefore may provide a better pharmacokinetic marker of its development. It appears that the only accurate pharmacokinetic indicator of response is the level of drug in the tumour itself.

In vivo cellular adriamycin concentrations related to growth inhibition of normal and leukemic human bone marrow cells

Inhibition of clonogenicity of normal and leukemic human hematopoietic progenitor cells was studied after in vivo and in vitro exposure of bone marrow to adriamycin (ADM). Flow cytometric determination of cellular ADM concentrations in blast cells, expressed in fluorescence units/cell (FU/cell), correlated well with the extent of cytotoxicity. After 2 h in vitro exposure to 500 ng ADM/ml, the ADM concentration of leukemic (n = 7) and normal (n = 4) bone marrow blast cells amounted to 231 +/- 180 and 249 +/- 53 FU/cell respectively, producing moderate decreases in clonogenicity by 44 +/- 30 and 54 +/- 27%. Exposure to 2000 ng/ml produced ADM concentrations of 1184 +/- 472 FU/cell for leukemic blast cells and 1024 +/- 281 FU/cell for normal blast cells. Inhibition of clonogenicity was 96 +/- 7% in leukemic blasts and 99 +/- 1% in normal blasts. In vivo ADM concentrations in leukemic blast cells at 1-2 h after administration were 216 +/- 98 FU/cell (n = 8 patients). This implies that inhibition of clonogenicity after administration of conventional dosages of ADM will be approx. 60-70% for both leukemic and normal bone marrow progenitor cells. Such values were noted in four patients of whom bone marrow was cultured, which was obtained shortly after ADM monotherapy.

Pharmacokinetics of adriamycin, adriamycinol, and antipyrine in patients with moderate tumor involvement of the liver

The pharmacokinetics of adriamycin, its metabolite adriamycinol, and antipyrine were studied in 17 patients with moderate tumor involvement of the liver and compared to that of 19 tumor patients with normal liver function (Preiss et al. 1985). The individual liver function parameters deviated from normal by a factor ranging from 2.5 to 12.2. The t1/2 alpha and t1/2 beta, the AUC (corrected for body weight and dose) and the total body clearance (CL, corrected for body weight) of adriamycin did not differ significantly between the two groups of patients. Likewise, there was no difference in the kinetic parameters of antipyrine between the two groups. Unlike adriamycin and antipyrine, adriamycinol was found to have a significantly longer t1/2term (60.5 vs 28.3 h, P less than 0.001), an increased AUC (3.00 vs 1.43 h/ug per ml, P less than 0.02), and a higher AUCadriamycinol/AUCadriamycin ratio (0.94 vs 0.52, P less than 0.02) in patients with moderate tumor involvement of the liver. The CL, the AUC, and t1/2 beta of adriamycin correlated significantly (P less than 0.001 and P less than 0.01) with the corresponding kinetic parameters of antipyrine, but not with the usual liver function parameters. No correlation could be found between the kinetic parameters of adriamycinol and those of antipyrine.

Plasma levels of daunorubicin metabolites and the outcome of ANLL therapy

Levels of plasma daunorubicin, daunorubicinol and aglycone metabolites were measured in 47 patients 3 h after daunorubicin was administered daily for three days as part of a cytosine arabinoside/daunorubicin remission induction regimen. High-pressure liquid chromatography with fluorescence detection was used for separation and quantitation of the drug and its metabolites. A wide range of plasma levels were observed regardless of the outcome of therapy. Patients who had high levels of the drug, or daunorubicinol on day 1 of therapy tended to have high levels on days 2 and 3 of the regimen. Three hours after the third daily dose of daunorubicin was administered, patients who would not enter remission had significantly higher levels of aglycone metabolites in plasma than did patients who entered remission. These data indicate that resistance to chemotherapeutic effects of daunorubicin may be connected with metabolism of the drug, especially with enhanced metabolism to aglycones.

Pharmacokinetics of daunorubicin as a determinant of response in acute myeloid leukemia

Twenty-one adult patients with acute myeloid leukemia (AML) were treated with the EORTC LAM-6 remission induction protocol [daunorubicin (DNR) (45 mg/m2, days 1-3), cytarabine (200 mg/m2, days 1-7) and vincristine (1 mg/m2, day 2)]. Pharmacokinetics of DNR were studied at day 1. The concentration of DNR and daunorubicinol were determined in plasma, in white blood cells and in bone marrow. A large variability was observed with respect to (1) the plasma area under the curve (AUC) 0-24 h (range: 0.06-0.37 nmol X h/ml); (2) the white cell AUC 0-24 h (range: 0-441 nmol X h/10(9) cells); and (3) the 1 h bone marrow concentration (range: 0-27 nmol/10(9) cells). In eight patients treated twice, a small intraindividual variability of these parameters was observed. Concentrations in plasma did not correlate with cellular concentrations. All pharmacokinetic parameters in plasma and white cells did not correlate with response to therapy. In patients reaching complete remission (CR), however, the tumor load, as expressed by the number of blast cells present in the untreated bone marrow, was significantly lower than the number of blast cells in patients not reaching CR.

Continuous infusion or intravenous bolus: what is the rationale for doxorubicin administration?

In order to achieve a better therapeutic index of anticancer drugs, numerous authors are using continuous infusion therapy rather than classical intravenous bolus injection. In the case of doxorubicin or daunorubicin numerous experimental data have been published, which could provide a rationale to this clinical problem. However, due to the variety of the approaches used, the results are inconsistent and no definitive conclusion can be drawn. Several clinical phase I and II trials have been performed since 1980; they show that the toxicity of doxorubicin may be reduced by the use of continuous infusion, but the preservation of the efficacy of the drug has never been proved. Comparative phase III trials are required before this schedule of administration become routine procedure for this drug.

Marked inter-patient variation in adriamycin biotransformation to 7-deoxyaglycones: evidence from metabolites identified in serum

Several factors are known to modulate the clinical pharmacokinetics of adriamycin (ADR). Biotransformation has not been studied in this context because of problems identifying serum metabolites. We have studied patterns of ADR biotransformation in 25 patients with normal liver and kidney function and in most cases receiving ADR for the first time. Three major serum metabolites were identified by HPLC, TLC and mass spectrometry and their pharmacokinetics were followed over a 24-hr period. The relative amount of each metabolite present in a patient was quantitated by calculating its AUC. Adriamycinol was the major metabolite detected in the majority of patients. Adriamycin 7-deoxyaglycone was detected in the serum of 15 patients where it accounted for a small percentage of the total ADR concentration (1-5%). Its apparent half-life was normally less than 30 min. Adriamycinol 7-deoxyaglycone was detected in the serum of only 13 patients where it accounted for a greater percentage of the total ADR concentration (10-20%). Its pharmacokinetics exhibited marked inter-patient variations, with apparent half-lives ranging from 0.1 to 24 hr. There was a correlation between the AUC of ADR and the relative amount of metabolites present in each patient (r = 0.73). Thus, biotransformation may explain, partly, inter-patient variations in ADR pharmacokinetics. In turn, variations in biotransformation are dictated by whether or not ADR is converted to 7-deoxyaglycones.

Quantitative evaluation of intracellular uptake of daunorubicin in acute myeloid leukemia: a method analysis

Critical technical parameters to establish a reliable method for quantifying the intracellular content of anthracyclines were evaluated in patients with acute myelocytic leukemia (AML); two methods were used for the isolation of leukocytes from the peripheral blood and two methods, for the extraction of daunorubicin (DNR), daunorubicinol (DOL), and doxorubicin (DOX) from these cells, followed by drug analysis using high-performance liquid chromatography (HPLC). At 0-4 degrees C the recovery of leukocytes after methylcellulose separation was low (64%). Cold hypotonic lysis gave better recovery (100%) when performed at the same temperature. After low-volume (2 ml extraction mixture) drug extraction from isolated leukocytes, the recoveries of DNR, DOL, and DOX from the cells were low, and they were inversely related to the cellularity of the sample, irrespective of the amount of drug in the cells. With high-volume extraction (5 ml extraction mixture) the recoveries were better (up to 95%), but they remained dependent on the cellularity. A correction factor accounting for these cellularity-related recoveries was applied to calculate the DNR and DOL contents of the leukocytes. Finally, using this information, plasma and cellular DNR and DOL levels were measured in seven patients with AML during their first course of remission induction therapy. The cellular DNR levels appeared to vary over a broad range and did not correlate with plasma pharmacokinetics.

Anticancer drug pharmacodynamics

A considerable amount of information is available on the pharmacokinetics of anticancer drugs, but much less is known of their pharmacodynamics, that is of the relationship between therapeutic or toxic response and drug concentration. Drug dosage regimens which are to achieve defined therapeutic objectives can only be designed when both the pharmacokinetic and the pharmacodynamic characteristics of a drug are known. There are a few reports in the literature of relationships in man between toxic response and pharmacokinetic parameters of anticancer drugs, and an even smaller number of reports of relationships between therapeutic response and pharmacokinetic parameters. It is suggested that the lack of pharmacodynamic information is currently limiting the application of pharmacokinetic information to cancer therapy. Ways of improving knowledge of the pharmacodynamics of anticancer drugs are suggested.

Comparative pharmacokinetics of doxorubicin given by three different schedules with equal dose intensity in patients with breast cancer

The pharmacokinetics of doxorubicin given according to three different schedules with a similar dose-time intensity have been studied and compared in 16 women with metastatic breast cancer. Six patients were treated with doxorubicin 75 mg/m2 by i.v. bolus repeated every 3 weeks; 5 patients received doxorubicin by 4-day continuous infusion every 3 weeks (4 at 75 mg/m2 and 1 at 60 mg/m2); 5 patients received 25 mg/m2 by i.v. bolus given weekly. Timed blood samples were collected and plasma levels of doxorubicin and its metabolite doxorubicinol were measured by high-performance liquid chromatography with fluorescence detection. Peak plasma concentrations were measured, and areas under the concentration-time curves calculated. Peak plasma levels of doxorubicin were significantly lower with the 4-day infusion than with either of the bolus injections. The 4-day infusion, however, gave significantly greater total exposure to doxorubicin and doxorubicinol, as indicated by area under the concentration-time curve, than weekly or 3-weekly bolus treatment. A single bolus injection of doxorubicin 25 mg/m2 yielded a total exposure to doxorubicin approximately half that achieved with a 75 mg/m2 bolus injection. Over a 3-week period, therefore, total exposure to doxorubicin would be greater with the weekly low-dose schedule than with the 3-weekly administration. We conclude that drug scheduling has significant effects on doxorubicin pharmacokinetics.