Clinical pharmacokinetics of doxorubicin

Pegylated liposomal doxorubicin, vincristine, and reduced-dose dexamethasone as first-line therapy for multiple myeloma

In patients with multiple myeloma (MM) who may ultimately receive active therapy, the combination of VAD (vincristine, doxorubicin, and dexamethasone) has been shown to be effective. However, the use of VAD is complicated by inherent risks that result from the use of central venous catheters, steroid toxicity, and by doxorubicin-associated adverse events such as cardiotoxicity and alopecia. To address these issues, a phase II trial investigating the combination of vincristine, pegylated liposomal doxorubicin, and reduced-schedule oral dexamethasone in the first-line treatment of patients with MM has been conducted. Patients with symptomatic, newly diagnosed MM were treated with intravenous (i.v.) pegylated liposomal doxorubicin 40 mg/m2 and vincristine 2 mg on day 1, along with dexamethasone 40 mg/day given either i.v. or orally for 4 days, every 4 weeks for a minimum of 6 cycles. Responses were reported in 29 patients (88%), and an additional 3 patients achieved stable disease. The median time to maximal response was 5.8 months (range, 0.7-13.6 months), and median overall survival time is estimated to be 60 months. This treatment regimen was well tolerated, and the most common grade 3/4 adverse events included hand-foot syndrome (21%), neutropenia (30%), anemia (21%), and mucositis (12%). Based on these results, the vincristine/liposomal doxorubicin/dexamethasone regimen appears to be effective and well tolerated in the first-line treatment of MM.

P-glycoprotein (ABCB1) but not multidrug resistance-associated protein 1 (ABCC1) is induced by doxorubicin in primary cultures of rat astrocytes

At least two drug efflux pumps involved in multidrug resistance, P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (Mrp1), are expressed in rat astrocyte primary cultures. The aim of this study was to compare the expression of P-gp and Mrp1 in primary cultures exposed to 50 or 500 ng/mL doxorubicin (DOX). Among the two P-gp genes expressed in rodents, mdr1a and mdr1b, a time- and dose-dependent increase in mdr1b mRNA levels was revealed by northern blot analysis. This up-regulation was inhibited by actinomycin D and occurred as early as 2 h after exposure to 50 or 500 ng/mL DOX, whereas mdr1a and mrp1 transcripts were not modified by the DOX exposure. In addition, DOX also strongly enhanced, in a time- and dose-dependent manner, P-gp but not Mrp1 expression. Moreover, DOX raised the cellular efflux of vincristine, a substrate for both P-gp and Mrp1. This efflux was inhibited by the P-gp modulators PSC833 and GW918, but not by the Mrp1 modulator MK571. On the other hand, a 24-h exposure to 500 ng/mL DOX, but not 50 ng/mL DOX, induced apoptosis in primary cultures of rat astrocytes. Fumonisin B1, a ceramide synthase inhibitor, reduced DOX-induced apoptosis, suggesting that de novo synthesis of the ceramide regulatory pathway might be involved in DOX-induced apoptosis. Moreover, western blot analysis showed that fumonisin B1 was not able to decrease the overexpression of P-gp induced by DOX. Our results provide evidence that DOX up-regulates a functional P-gp in primary cultures of rat astrocytes and might cause astrocyte apoptosis via the ceramide pathway.

Effect of the surface charge of liposomes on their uptake by angiogenic tumor vessels

Recently, cationic liposomes have been shown to preferentially target the angiogenic endothelium of tumors. It was the aim of our study to investigate the influence of liposomal surface charge on the uptake and kinetics of liposomes into solid tumors and tumor vasculature. Experiments were performed in the amelanotic hamster melanoma A-Mel-3 growing in the dorsal skinfold chamber preparation of male Syrian golden hamsters. Fluorescently labeled liposomes with different surface charge were prepared. Accumulation of i.v. injected liposomes was assessed by quantitative intravital fluorescence microscopy of tumor and surrounding host tissue. The histological distribution of liposomes was analyzed by double-fluorescence microscopy 20 min after application of fluorescently labeled lectin as a vascular marker. After i.v. application of anionic and neutral liposomes, we observed an almost homogeneous distribution of liposome-induced fluorescence throughout the chamber preparation without specific targeting to tumor tissue. In contrast, cationic liposomes exhibited a significantly enhanced accumulation in tumor tissue and tumor vasculature up to 3-fold compared to surrounding tissue (p<0.05). The histological distribution of neutral and anionic liposomes revealed extravasation 20 min after i.v. injection, while cationic liposomes displayed a highly selective accumulation on the vascular endothelium. In conclusion, cationic liposomes exhibited a preferential uptake in angiogenic tumor vessels and therefore may provide an efficient tool for the selective delivery of diagnostic or therapeutic agents to angiogenic blood vessels of solid tumors. On the other hand, anionic and neutral liposomes may be used as carriers of drugs to the extravascular compartment of tumors due to their extravasation.

Biological and environmental monitoring of hospital personnel exposed to antineoplastic agents: a review of analytical methods

In order to assess occupational exposure of hospital personnel involved in the preparation and administration of antineoplastic drugs, biological and environmental monitoring are essential to identify the main exposure routes and to quantify potential health risks. If workplace contamination cannot be completely avoided, it is of utmost importance to reduce exposure to the lowest possible levels. To this aim, not only do education and training of the exposed subjects play an important role, but accurate standardized sampling techniques and analytical methods are also required. A critical overview of the most significant methods available in the literature is presented and their value is discussed, especially with respect to their sensitivity and specificity. In addition, attention is given to validation procedures and, consequently, to their reliability. The results from the most important surveys carried out at hospital departments are also discussed, with a view to improving both monitoring strategies and moreover working conditions.

Doxorubicin cardiotoxicity: prevention of congestive heart failure with serial cardiac function monitoring with equilibrium radionuclide angiocardiography in the current era

BACKGROUND

Congestive heart failure (CHF) is among the most serious toxicities of doxorubicin, a potent cancer chemotherapeutic agent. Serial left ventricular ejection fraction (LVEF) monitoring during doxorubicin therapy for preventing CHF was proposed over 20 years ago. The current utility and cost-effectiveness of this approach in the present era are not known.

METHODS AND RESULTS

Clinical and follow-up data of 265 patients with cancer (age, 53 +/- 14 years; 76% women) undergoing doxorubicin chemotherapy with serial equilibrium radionuclide angiocardiography (ERNA) monitoring (> or =2 studies) were analyzed retrospectively. Patients with a normal baseline LVEF (> or =50%) and a 10% or greater point fall in LVEF to a final value of less than 50% during doxorubicin therapy were considered "at risk" for CHF (n = 41). Over 679 +/- 426 days of follow-up, 7 patients (2.6%) had CHF develop and 90 (34%) died (all cancer-related deaths, with none due to CHF). A comparison of "at-risk" (n = 41 [15%]) and "low-risk" (n = 224 [85%]) groups showed a higher incidence of CHF (12% vs 0.9%, P <.0001), lower baseline LVEF (58% +/- 8% vs 64% +/- 8%, P <.0001), lower value for the lowest LVEF (42% +/- 8% vs 57% +/- 7%, P <.0001), and higher rate of cancer-related deaths (59% vs 29%, P =.0003) in the former despite similar cumulative doxorubicin dose (304 +/- 124 mg/m(2) vs 284 +/- 110 mg/m(2), P = not significant). There were no differences in age, gender, cancer type, and co-morbidity. Cost analysis showed the overall cost of ERNA studies to be lower than the 1-year cost of caring for additional cases of CHF that would potentially be prevented by routine LVEF monitoring.

CONCLUSIONS

An incipient fall in LVEF detected on serial ERNA during doxorubicin therapy provides an appropriate and cost-effective approach for predicting and preventing impending CHF. Use of this approach was associated with a low incidence of CHF (2.6%) and no CHF-related mortality in this study.

Evaluation of rat intestinal absorption data and correlation with human intestinal absorption

The absorption of 111 drug and drug-like compounds was evaluated from 111 references based on the ratio of urinary excretion of drugs following oral and intravenous administration to intact rats and biliary excretion of bile duct-cannulated rats. Ninety-eight drug compounds for which both human and rat absorption data were available were selected for correlation analysis between the human and rat absorption. The result shows that the extent of absorption in these two species is similar. For 94% of the drugs the absorption difference between humans and rats is less than 20% and for 98% of drugs the difference is less than 30%. There is only one drug for which human absorption is significantly different from rat absorption. The standard deviation is 11% between human and rat absorption. The linear relationship between human and rat absorption forced through the origin, as determined by least squares regression, is %Absorption (human)=0.997%Absorption (rat) (n=98, SD=11). It is suggested that the absorption in rats could be used as an alternative method to human absorption in pre-clinical oral absorption studies.

A Phase II trial of pegylated liposomal doxorubicin, vincristine, and reduced-dose dexamethasone combination therapy in newly diagnosed multiple myeloma patients

BACKGROUND

Patients with multiple myeloma (MM) have increased bone marrow angiogenesis, a low plasma cell labeling index, and multidrug resistance (the primary cause of chemotherapy failure). MM patients receiving the vincristine, doxorubicin, and dexamethasone (VAD) regimen develop resistance and cardiac and steroid toxicity. Pegylated liposomal doxorubicin (Doxil/CAELYX) could potentially extend the duration of malignant plasma cell exposure to therapeutic levels of doxorubicin. This Phase II study evaluates combination pegylated liposomal doxorubicin, vincristine, and reduced-dose dexamethasone in MM patients.

METHODS

Thirty-three newly diagnosed patients with MM received intravenous pegylated liposomal doxorubicin (40 mg/m(2)), vincristine (2.0 mg, Day 1), and oral or intravenous dexamethasone (40 mg per day for 4 days) every 4 weeks for six or more cycles and/or for two cycles after the best response.

RESULTS

The overall response rate was 88%: 4 (12%) patients achieved a complete response, 18 (55%) a major response, and 7 (21%) a minor response. Three patients (9%) had stable and one (3%) had progressive disease. The median time to progression was 23.1 months, with 2-year and 3-year progression-free survival rates of 42% and 23%, respectively. The patient survival rate at 3 years was 67%. No patients discontinued treatment due to adverse events. Myelosuppression was manageable. The most common toxicities were Grade 3 palmar-plantar erythrodysesthesia, mucositis, and neutropenia. Only one patient experienced cardiotoxicity.

CONCLUSIONS

Substituting pegylated liposomal doxorubicin for doxorubicin in the VAD regimen and reducing the dose of dexamethasone in patients with MM improve the safety profile and convenience of the treatment regimen without compromising efficacy.

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.

Anthracyclines in the treatment of gynecologic malignancies

OBJECTIVE

The purpose of this article is to present a summary of the pharmacology of anthracyclines as well as to review the results of clinical trials including patients with gynecologic malignancies treated with anthracycline-based therapy.

METHODS

We performed a MEDLINE literature search of relevant clinical trials for the scope of this review that evaluated anthracycline-based therapy in gynecologic malignancies.

RESULTS

Doxorubicin has established activity in carcinomas that arise in the ovary, uterine cervix, and endometrium as well as in uterine sarcomas. However, doxorubicin has structural characteristics that limit its efficacy and safety. Newer anthracyclines with distinct structure, pharmacokinetics, pharmacodynamics, and toxicity profiles have been developed to overcome the limitations of doxorubicin and to further exploit the activity of anthracyclines. Epirubicin is characterized by a structural formula that confers similar cytotoxic antitumor activity with fewer associated side effects than its analogue. Most recently, pegylated liposomal formulations, with distinct pharmacokinetic properties and a favorable toxicity profile, have shown antitumor activity as salvage therapy in ovarian cancer. Intraperitoneal mitoxantrone is also associated with activity in ovarian cancer; however, its clinical use is limited by the severity of local adverse effects.

CONCLUSIONS

The role of anthracyclines in the management of advanced gynecologic malignancies is important as part of first-line therapy or as a salvage approach. Newer anthracycline agents such as epirubicin and pegylated liposomal doxorubicin are associated with a more favorable toxicity profile. Clinical trials are under way to further explore the role of newer anthracycline-based regimens as first-line or salvage treatment in gynecologic malignancies.

Modification of adriamycin pharmacokinetics by direct electric current in rats

Adriamycin (ADR, doxorubicin), a drug having cardiotoxicity, is electrically charged as a cation in blood. We therefore investigated whether iontophoresis caused by direct electric current (DC; 50 microA, 90 min) would cause systemic modification of ADR pharmacokinetics. Cathode and anode were placed into a right kidney and muscles of the abdominal wall, respectively, in six Donryu rats. Urinary excretion of ADR, as measured by catheterizing into the right kidney, was significantly higher in the DC group than in the controls (p < 0.05). Both plasmic and renal ADR clearances were significantly higher in the DC group (p<0.005 and p<0.001, respectively). Tissue ADR concentrations were significantly lower in the DC group (heart: p<0.003; liver and lung: both p<0.05). These results suggest that electric therapy might potentially induce modification of ADR pharmacokinetics by iontophoresis, and that the therapy might effectively change ADR concentration both locally and systemically.

Quantification of doxorubicin in plasma--a comparative study of capillary and venous blood sampling

Doxorubicin, an anthraquinone glycoside, is currently one of the clinically most important antineoplastic drugs. The aim of the present study was to identify potential concentration differences of doxorubicin in plasma from capillary and venous blood samples. Sixteen patients (seven females and nine males; median age: 37 years, range: 1-77 years) were included. The quantitative analysis of doxorubicin was carried out by reversed-phase liquid chromatography with fluorometric detection. The concentration of doxorubicin in capillary and venous samples were closely correlated (r=0.98; p<0.0001). The median plasma concentration ratio capillary/venous was 1.13 (95% confidence interval: 1.06-1.20) and not affected either by plasma drug concentration, age or the body mass index of the patient. The concentration ratio was significantly higher in males (median: 1.18) than in females (median: 1.01). The observed concentration differences of doxorubicin in plasma from capillary and venous samples are of minor importance only. Capillary blood sampling is recommended for use in pharmacokinetic studies of doxorubicin, especially in pediatric patients, in order to avoid sometimes traumatic venous blood sampling.

Alterations in P-glycoprotein expression in mouse tissues by doxorubicin: implications for pharmacokinetics in multiple dosing regimens

The purpose of the studies presented here is to determine if alterations in doxorubicin (DOX) pharmacokinetics that seem to occur following multiple-dosing are due to changes in DOX elimination via P-glycoprotein (PGP) mediated transport in the liver, kidney and gut. A pharmacokinetic study in female Balb/c mice was carried out with blood and tissue DOX levels measured in animals following a single DOX treatment (6 mg/kg), and in animals following a second DOX treatment after receiving a DOX treatment a week earlier. The pharmacokinetics of DOX in blood and tissues was altered by earlier exposure to DOX, as the animals that were treated once a week for 2 weeks showed an increased rate of DOX elimination from blood and tissues following the second treatment. Immunoblot analysis of PGP expression in liver and kidney from naïve and DOX-treated mice showed an approximately 1.2-fold elevation of PGP protein in these tissues in response to DOX exposure. Immunohistochemical staining of liver and small intestine sections for PGP showed 1.6-fold and 1.9-fold increases, respectively, in the DOX-treated tissues. These results have implications both in multiple-dosing regimens, as well as multiple-drug regimens, where DOX is used in combination with other drugs that are substrates for PGP-mediated efflux. Increases in PGP expression in both hepatic and extrahepatic tissues can lead to changes in the pharmacokinetics of DOX, as well as other drugs that are transported by PGP.

Phase I and pharmacokinetic study of the novel MDR1 and MRP1 inhibitor biricodar administered alone and in combination with doxorubicin

PURPOSE

To evaluate the safety, tolerability, and pharmacokinetics of biricodar (VX-710), an inhibitor of P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP1), alone and with doxorubicin in patients with advanced malignancies. The effect of VX-710 on the tissue distribution of (99m)Tc-sestamibi, a P-gp and MRP1 substrate, was also evaluated.

PATIENTS AND METHODS

Patients with solid malignancies refractory to standard therapy first received a 96-hour infusion of VX-710 alone at 20 to 160 mg/m(2)/h. After a 3-day washout, a second infusion of VX-710 was begun, on the second day of which doxorubicin 45 mg/m(2) was administered. Cycles were repeated every 21 to 28 days. (99m)Tc-sestamibi scans were performed before and during administration of VX-710 alone.

RESULTS

Of the 28 patients who enrolled, 25 patients were eligible for analysis. No dose-limiting toxicity (DLT) was observed in the nine assessable patients who received 120 mg/m(2)/h or less. Among seven patients receiving VX-710 160 mg/m(2)/h, two DLTs were seen: reversible CNS toxicity and febrile neutropenia. All other adverse events were mild to moderate and reversible. Plasma concentrations of VX-710 in patients who received at 120 and 160 mg/m(2)/h were two- to fourfold higher than concentrations required to fully reverse drug resistance in vitro. VX-710 exhibited linear pharmacokinetics with a harmonic mean half-life of 1.1 hours. VX-710 enhanced hepatic uptake and retention of (99m)Tc-sestamibi in all patients.

CONCLUSION

A 96-hour infusion of VX-710 at 120 mg/m(2)/h plus doxorubicin 45 mg/m(2) has acceptable toxicity in patients with refractory malignancies. The safety and pharmacokinetics of VX-710 plus doxorubicin warrant efficacy trials in malignancies expressing P-gp and/or MRP1.

Evaluation of human intestinal absorption data and subsequent derivation of a quantitative structure–activity relationship (QSAR) with the Abraham descriptors

The human intestinal absorption of 241 drugs was evaluated. Three main methods were used to determine the human intestinal absorption: bioavailability, percentage of urinary excretion of drug-related material following oral administration, and the ratio of cumulative urinary excretion of drug-related material following oral and intravenous administration. The general solvation equation developed by Abraham's group was used to model the human intestinal absorption data of 169 drugs we considered to have reliable data. The model contains five Abraham descriptors calculated by the ABSOLV program. The results show that Abraham descriptors can successfully predict human intestinal absorption if the human absorption data is carefully classified based on solubility and administration dose to humans.

A cell-based drug delivery system for lung targeting: II. Therapeutic activities on B16-F10 melanoma in mouse lungs

The in vitro and in vivo anticancer activities of doxorubicin-loaded B16-F10 murine melanoma cells (DLTC) were evaluated. DLTC showed similar growth-inhibitory effects against live B16-F10 cells with doxorubicin solution in cell culture system, with the IC50 of 0.11 microM and 0.17 microM, respectively. However, DLTC demonstrated higher effectiveness than the free solution in treating mouse lung cancer caused by live B16-F10 cells. Syngeneic C57BL mice were inoculated intravenously with live B16-F10 cells first, and then received daily treatment of intravenous injections of doxorubicin in either DLTC or free solution form. Compared with the control group treated with phosphate-buffered saline, DLTC eradicated almost all the lung cancer colonies (>99%), while the free solution form reduced the colonies by 61%, when the treatment was given at an early stage. If the treatment started after the establishment of micrometastatic colonies in the mouse lungs, DLTC and free solution treatment resulted in 85% and 30% cancer reduction, respectively. Additional experiments demonstrated that the reduction of lung cancer colonies by DLTC was related to the initial treatment time: the earlier the treatment, the greater the effect. In conclusion, DLTC showed better therapeutic outcomes than free solution form in treating lung cancer of our animal model.

A cell-based drug delivery system for lung targeting: I. Preparation and pharmacokinetics

A drug-loaded tumor cell (DLTC) system has been developed for lung metastasis-targeting drug delivery. Doxorubicin was loaded into B16-F10 murine melanoma cells (96 microg/10(6) cells). The loading process led to the death of all the carrier cells. The diameter of DLTC was 15.03+/-2.36 microm (mean +/- SD). The amount and rate of doxorubicin being released from the DLTC mainly depended on the drug loading and carrier cell concentration. Over a 6-month storage in phosphate buffered saline (PBS) at 4 degrees C, the decrease in intracellular drug concentration and the carrier cell number were less than 25% and 5%, respectively. After a bolus injection of 30 microg doxorubicin in either DLTC form or free solution into the mice tail veins, drug deposit in the lung from DLTC was 3.6-fold of that achieved by free drug solution. The latter resulted in higher drug content in liver and spleen. Extensive trypsinization of DLTC reduced its lung targeting effect by 30%, and the density of surface adhesion molecule GM3 on DLTC surface by 25%. In conclusion, this DLTC system demonstrated a lung-targeting activity that may be partially attributed to its specific surface characteristics.

Drug-targeting strategies in cancer therapy

Genetic changes in cell-cycle, apoptotic, and survival pathways cause tumorigenesis, leading to significant phenotypic changes in transformed cells. These changes in the tumor environment - elevated expression of surface proteases, increased angiogenesis and glucuronidase activity - can be taken advantage of to improve the therapeutic index of existing cancer therapies. Targeting cytotoxics to tumor cells by enzymatic activation is a promising strategy for improving chemotherapeutics.

The prognostic value of etoposide area under the curve (AUC) at first chemotherapy cycle in small cell lung cancer patients: a multicenter study of the groupe Lyon-Saint-Etienne d'Oncologie Thoracique (GLOT)

PURPOSE

To assess the potential relationships between systemic exposure to doxorubicin, etoposide and ifosfamide at first chemotherapy cycle and therapeutic effect, tumor response, toxicity, and survival, in small cell lung cancer (SCLC) patients.

PATIENTS AND METHODS

Twenty-four patients referred to five different centers with either thorax-limited or metastatic SCLC entered the study. All but one received two induction courses of the 3 day-AVI (doxorubicin 50 mg/m(2) day 1, etoposide 120 mg/m(2) day 1, 2, 3, ifosfamide 2000 mg/m(2) day 1, 2) regimen. Individual plasma samples were collected at the first course and complete concentration data on 24 courses were available. Drugs exposures were estimated using a population pharmacokinetic method and expressed as clearance (Cl), area under the curve (AUC), and AUC-intensity (AUC/cycle duration). Responding patients received thoracic irradiation+concomitant cisplatinum-etoposide (limited disease) or four more courses of AVI (extensive disease). The impact of exposure parameters on haematological toxicity, tumor response and overall survival was assessed using linear regression, the Mann-Whitney U-test and the log-rank test/Kaplan-Meier estimation, respectively.

RESULTS

Twenty-three patients could be evaluated for response and survival. We found no relationship between drug exposure and haematological toxicity but all patients had received Granulocyte-Colony Stimulating Factor support. Tumor response was marginally influenced by ifosfamide AUC. In patients with etoposide AUC>254.8 mg h/l, 1-year survival was 50.0 vs. 9.1% in the other group (median 11.4 vs. 7.1 months, P=0.02), with respect to established prognostic factors. In patients with extensive disease only (n=15), 1-year survival was 42.9 vs. 0% (median 11.3 vs. 5.3 months, P=0.01).

CONCLUSION

This study strongly suggests that SCLC patients should benefit from sufficient etoposide exposure at first cycle to improve survival. Adaptative control based on plasma concentration measurements should be tested in further studies assessing various polychemotherapy regimens.

Population pharmacokinetics of doxorubicin, etoposide and ifosfamide in small cell lung cancer patients: results of a multicentre study

AIMS

To determine the population pharmacokinetic (PK) parameters of doxorubicin (Dox), etoposide (Eto) and ifosfamide (Ifo) in small cell lung cancer (SCLC) patients, to assess the potential relationship between those parameters and to estimate the impact of individual morphological and biological covariates on patients' PK parameters.

METHODS

Twenty-four patients with either SCLC limited to the thorax or extensive SCLC entered the study. All but one received at least two 3 day courses of the standard AVI (Dox 50 mg m-2 day 1, Eto 120 mg m-2 day 1,2,3, Ifo 2000 mg m-2 day 1,2) regimen. Individual blood samples were collected during each course and data on 47 courses were available. Data were analysed with the NONMEM program. Dox, Eto and Ifo plasma concentrations were studied with multicompartment (3, 2 and 2, respectively) models. Inter-individual and interoccasion (course-to-course) variabilities were estimated. The influence of individual covariates (age, sex, stage of the disease, weight, height, body-surface area, serum creatinine, total protein, LDH, ASAT, ALAT, alkaline phosphatase, gamma-GT, bilirubin) on PK parameters was also assessed. Correlations between individual PK parameters of Dox, Eto and Ifo were explored by using Pearson's correlation coefficient.

RESULTS

Multiple data were available for each patient. Dox clearance (CL) and volume of distribution (Vd) were 32.0 l h-1 and 9.3 l (Inter-individual variability: 17.2% and 19.2%). Eto CL (l h-1) and Vd were, respectively, 3.34-0.0083* serum creatinine (micromol l-1) and 6.38 l (interindividual variability: 15.6% and 18.7%). Ifo CL and Vd at day 1 were 5.6 l h-1 and 26.0 l (interindividual variability: 10.1% and 17.2%, respectively). Estimation of course-to-course variability improved the precision of PK models in some cases. No correlation was observed between the respective PK parameters of each drug. Of individual covariates tested, only serum creatinine correlated with Eto CL (r = -0.37, P < 0.001). Self-induction of the metabolism of Ifo was apparent (mean CL increase from day 1 to day 2 : 42%) and individually correlated with the CL value at day 1 (r = -0.61, P < 0.001).

CONCLUSIONS

Assessment of potential relationships between individual systemic exposure of chemotherapy and therapeutic endpoints (tumour response, toxicity and survival) will be required to adjust drugs dosages based on individual PK parameters rather than questionable body-surface area. However, all three drugs in the AVI regimen should be monitored simultaneously.

Gemcitabine in combination with doxorubicin in advanced breast cancer: final results of a phase II pharmacokinetic trial

PURPOSE

Gemcitabine has promising single-agent activity in advanced breast disease. The aim of this phase II study was to determine the efficacy, toxicity, and pharmacokinetic profile of gemcitabine administered with doxorubicin as first-line treatment in patients with metastatic breast cancer.

PATIENTS AND METHODS

Of the 42 women with metastatic breast cancer (age 33 to 74 years; mean age, 55 years), 13 were chemotherapy-naive and 29 had received adjuvant chemotherapy. Gemcitabine (800 or 1,000 mg/m(2)) and doxorubicin (25 mg/m(2)) were administered intravenously on days 1, 8, and 15 of each 28-day cycle. Blood samples were drawn on day 8 of cycles 1, 2, and 3 and of subsequent odd cycles for gemcitabine pharmacokinetic determinations and before and after the first dose of cycle 1 or 2 for doxorubicin determinations.

RESULTS

There were three complete and 20 partial responses, for an overall response rate of 55% (95% confidence interval [CI], 40% to 70%) and a complete response rate of 7%. The median survival time for all 42 patients was 27 months (95% CI, 13.4 to 30.0 months) and the 1-year survival rate was 80%. Toxicity was mainly hematologic. The disposition of both drugs was unchanged when they were administered on the same day compared with when they were given singly.

CONCLUSION

The combination of gemcitabine (800 mg/m(2)) and doxorubicin (25 mg/m(2)) can be safely administered using a weekly schedule. The disposition of both drugs is unchanged when they are administered on the same day. This combination shows promising activity with acceptable toxicity compared with other combination therapies.

Effect of fluconazole on the pharmacokinetics of doxorubicin in nonhuman primates

Antifungal prophylaxis in cancer patients who are undergoing chemotherapy is associated with prolonged neutropenia. We measured the effect of fluconazole on doxorubicin pharmacokinetics in nonhuman primates to determine if neutropenia is related to a pharmacokinetic interaction that delays the clearance of the chemotherapeutic agent. Fluconazole pretreatment had no effect on doxorubicin pharmacokinetics.

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.

Lack of mechanism-based inactivation of rat hepatic microsomal cytochromes P450 by doxorubicin

Administration of the antineoplastic doxorubicin to rodents causes depression of hepatic cytochrome P450 (CYP) dependent biotransformation, an effect that has been partially attributed to the ability of doxorubicin to stimulate microsomal lipid peroxidation. Since doxorubicin can be bioactivated by the CYP/NADPH-CYP reductase system to products that bind covalently to microsomal protein, we hypothesized that doxorubicin functions as a mechanism-based inactivator of hepatic microsomal CYPs and (or) NADPH-CYP reductase under conditions in which doxorubicin-stimulated NADPH-dependent lipid peroxidation is minimized. In vitro studies were conducted with hepatic microsomes isolated from untreated and phenobarbital-treated male rats. Unlike the positive control carbon tetrachloride, doxorubicin (10 µM) did not stimulate NADPH-dependent lipid peroxidation in microsomal incubations containing EDTA (1.5 mM). Doxorubicin did not cause NADPH-dependent loss of microsomal CYP, heme, or steroid hydroxylation activities selective for CYP2A, CYP2B, CYP2C11, and CYP3A. The positive control 1-aminobenzotriazole caused marked NADPH-dependent decreases in all of these parameters. Neither doxorubicin nor 1-aminobenzotriazole caused NADPH-dependent loss of NADPH-CYP reductase activity, and neither compound altered the immunoreactive protein levels of CYP2B, CYP2C11, CYP3A, and NADPH-CYP reductase. These results indicate that a pharmacologically relevant concentration of doxorubicin does not cause direct mechanism-based inactivation of hepatic microsomal CYPs or NADPH-CYP reductase, suggesting that the ability of doxorubicin to depress hepatic CYP-mediated biotransformation in vivo is due to lipid peroxidation mediated heme destruction, altered heme metabolism, and (or) decreased expression of selected CYP enzymes.Key words: doxorubicin, cytochrome P450, mechanism-based inactivation, lipid peroxidation.

Pharmacokinetics of doxorubicin incorporated in solid lipid nanospheres (SLN)

The pharmacokinetics of doxorubicin incorporated as ion-pair into solid lipid nanospheres (SLN) was compared with that of the commercial solution of the drug. Male albino rats (Wistar-derived strain) were treated i.v. with equivalent doses (6 mg kg(-1)) of two different doxorubicin formulations: an aqueous dispersion of SLN carrying doxorubicin and a commercial doxorubicin solution (Adriablastina). These formulations were injected, under general anaesthesia, through a cannula into the jugular vein and blood samples were collected at 1, 15, 30, 45, 60, 120 and 180 min after administration. After 180 min rats were killed and samples of liver, heart, lung, kidney, spleen and brain were collected. Blood and tissue samples were analysed by a spectrofluorimetric method. The anthracycline concentration in the blood was markedly higher at each point times with the SLN than with the commercial solution. The drug concentration was also higher in the lung, spleen and brain. SLN-treated rats showed a lower doxorubicin concentration in liver, heart and kidney. The results showed that SLN increased the area under the curve (0-180 min) of doxorubicin compared to conventional doxorubicin solution and led to a different body distribution profile.

Doxorubicin does not spread systemically following a local injection into the eyelids of rabbits

PURPOSE

An experimental treatment for benign essential blepharospasm and hemifacial spasm involves the direct injection of doxorubicin into the eyelids to permanently kill muscle. This study examined the extent of local and systemic spread of doxorubicin after localized injections of low doses into the eyelid and determined the length of time doxorubicin was retained in the eyelid after injection.

METHODS

Two mg doxorubicin was injected subcutaneously into the lower eyelids of rabbits. After various time periods, the eyelids were removed and dissected into three separate specimens consisting of skin, subcutaneous connective tissue including orbicularis oculi muscle, or palpebral conjunctiva. Nearby tissues were also collected, including facial muscles and extraocular muscles. Urine, blood, kidney, spleen, heart and liver samples were collected. All tissues were prepared for HPLC determination of doxorubicin concentration.

RESULTS

Doxorubicin was detected in all three eyelid specimens for the first 4 days after injection, although by the fourth day the level of doxorubicin was greatly reduced. On and after the seventh day, there was no detectable doxorubicin in the treated eyelid tissues. There were no detectable levels of doxorubicin in the urine or any other body tissue at any of the post-injection intervals examined. There was no long term retention in any of the eyelid tissues examined.

CONCLUSIONS

The well described array of serious systemic side effects caused by the use of high systemic doses of doxorubicin as a chemotherapeutic agent made it critical to ascertain how long doxorubicin remained within the injected eyelids, and to determine to what extent and with what time course local injections of chemically intact doxorubicin might spread systemically. The short retention of the active or unmetabolized drug at the injection site is important, since more than one set of injections has been required for satisfactory amelioration of muscle spasms in blepharospasm and hemifacial spasm patients. The lack of detectable systemic spread of the drug distant from the local site of injection as well as the lack of long term retention of the locally injected doxorubicin lends support for the safety of doxorubicin administered in this manner to blepharospasm and hemifacial spasm patients.

Anthracycline analysis by capillary electrophoresis. Application to the analysis of daunorubicine in Kaposi sarcoma tumor

Laser-induced fluorescence (LIF) detection is now a well-known sensitive and selective detection mode for capillary electrophoresis (CE) analysis. It has been shown to be 100- to 100,000-times more sensitive than UV detection and little work has been done using LIF in conjunction with high-performance liquid chromatography (HPLC). The need for greater resolution and higher sensitivity for the analysis of anthracyclines (fluorescent chemotherapic drugs), prompted us to compare CE-LIF and HPLC-LIF, for the detection of these substances. CE-LIF sensitivity based on quantity of anthracycline injected is 50-times greater than that obtained with HPLC-LIF, because of the injected sample volume. Analysis of daunorubicin in Kaposy sarcoma tumors and in plasma are presented. The decrease of the concentration of daunorubicin in the tumor and in the plasma following time show the same behavior, indicating identical concentrations of the anthracycline in both samples.

Drug-induced apoptosis is delayed and reduced in XPD lymphoblastoid cell lines: possible role of TFIIH in p53-mediated apoptotic cell death

The tumor suppressor gene product p53 can bind to and inhibit the helicase activity of the multisubunit transcription-repair factor TFIIH. We previously reported that p53-mediated apoptosis is attenuated in primary human fibroblasts from individuals with Xeroderma Pigmentosum (XP) that harbor mutations in the TFIIH DNA helicases XPD or XPB. In this study we show that apoptosis is reduced and delayed in three XPD lymphoblastoid cell lines (LCLs), but not in an XPD heterozygote LCL, after exposure to doxorubicin, a DNA-damaging agent and topoisomerase II inhibitor frequently used in cancer therapy. Apoptosis was assessed by quantitation of Annexin V binding to exposed phosphatidylserine residues and by caspase-mediated cleavage of Poly(ADP)Ribose Polymerase (PARP). Apoptosis induced by doxorubicin was suppressed in LCLs retrovirally transduced with the Human Papillomavirus 16 E6 oncoprotein, consistent with the hypothesis that this is a p53-dependent process. PARP cleavage was not delayed in XPD LCLs in response to anti-Fas (CD95) antibody-mediated apoptosis, thus, the defect in the apoptotic pathway in these cells lies upstream of caspase activation. Similar changes in the expression of apoptosis-effector genes, p53, and p53-responsive genes p21Cip1/WAF-1/Sid1 (p21), gadd45, bcl-2 and bax were observed in normal and XPD LCLs after treatment with doxorubicin, indicating that delayed apoptosis was not a consequence of defective transcription of these genes. Thus, our studies provide further support to the hypothesis that XPD and p53 can functionally interact in a p53-mediated apoptotic pathway.

A simple HPLC method using a microbore column for the analysis of doxorubicin

Doxorubicin is one of the most potent anti-tumor agents generally used in the treatment of bone cancer. A simple and sensitive HPLC method was developed and validated for the assay of doxorubicin. The method used a C18 Luna microbore column (50 x 1 mm) with a fluorescent detector (505 nm Ex. and 550 nm Em.). The mobile phase consisted of water-acetonitrile-acetic acid (80:19:1, v/v/v, pH 3.0) and the flow rate was 0.1 ml min(-1). Daunomycin was used as the internal standard. This isocratic system required a 10-min run-time, giving a detection limit of 0.02 ng (0.035 pmol per injection). Standard curves were linear over the concentration range of 0.01-0.1 microg ml(-1). Relative standard deviations (R.S.D.) for the within-day, day-to-day precision, and the accuracy measurement for the assay were less than 4.0, 3.2, and 4.1%, respectively. This HPLC method was used to study the in vitro release characteristics of doxorubicin from implantable drug delivery system.

A critical evaluation of the mechanisms of action proposed for the antitumor effects of the anthracycline antibiotics adriamycin and daunorubicin

The mechanisms responsible for the antiproliferative and cytotoxic effects of the anthracycline antibiotics doxorubicin (Adriamycin) and daunorubicin (daunomycin) have been the subject of considerable controversy. This commentary addresses the potential role of DNA synthesis inhibition, free radical formation and lipid peroxidation, DNA binding and alkylation, DNA cross-linking, interference with DNA strand separation and helicase activity, direct membrane effects, and the initiation of DNA damage via the inhibition of topoisomerase II in the interaction of these drugs with the tumor cell. One premise underlying this analysis is that only studies utilizing drug concentrations that reflect the plasma levels in the patient after either bolus administration or continuous infusion are considered to reflect the basis for drug action in the clinic. The role of free radicals in anthracycline cardiotoxicity is also discussed.

Determination of doxorubicin and doxorubicinol in plasma of cancer patients by high-performance liquid chromatography

A high-performance liquid chromatographic assay with fluorescence detection has been developed for the determination of doxorubicin and its metabolite doxorubicinol in plasma of cancer patients. Quantitative extraction was achieved by a single protein-precipitation step of 1-ml samples with 500 microl of acetone in the presence of 100 microl of zinc sulfate [70% (w/v) in water]. Doxorubicin and doxorubicinol were separated isocratically on a column packed with Inertsil ODS-80A material and a mobile phase composed of water:acetonitrile:tetrahydrofuran (76:24:0.5, v/v/v). The related compound daunorubicin was used as internal standard. The column effluent was monitored fluorimetrically at an excitation wavelength of 480 nm and an emission wavelength of 560 nm, with a band width of 40 nm. The calibration graphs of doxorubicin and doxorubicinol were linear over a range of 1.0 to 100 and 0.50 to 50. 0 ng/mL, respectively, with lower limits of quantitation of 1.0 and 0.50 ng/ml. Results obtained from a 4-day validation study demonstrated excellent accuracy (91.0-106%) and precision (0.90-10. 2%) across the calibration ranges for both compounds. The developed method has been applied extensively to a clinical study to examine the pharmacokinetics and metabolism of doxorubicin in patients cotreated with a potent inhibitor of MDR1 P-glycoprotein activity, GF120918.

Low-density lipoprotein receptor-mediated delivery of a lipophilic daunorubicin derivative to B16 tumours in mice using apolipoprotein E-enriched liposomes

Many tumours express relatively high levels of low-density lipoprotein (LDL) receptors on their membranes. The LDL receptor is, therefore, an attractive target for the selective delivery of antineoplastic drugs to tumour cells. We reported previously on the synthesis of small apolipoprotein E (apoE)-containing liposomes that behave in vivo in a very similar way to native LDL. In this study, we examined the interaction of this liposomal carrier with cultured B16 melanoma cells. Binding of apoE liposomes to the cells is saturable, with a maximum binding of approximately 90000 particles per cell. Cross-competition studies indicated that apoE liposomes are bound by the LDL receptor. Association of apoE liposomes to B16 cells is strictly Ca2+ dependent, which forms additional evidence for a role of the LDL receptor. The affinity of apoE liposomes for the LDL receptor on B16 cells is 15-fold higher than that of LDL (0.77 vs 11.5 nM respectively). ApoE is essential for the LDL receptor recognition because liposomes lacking apoE were, in competition studies, 20- to 50-fold less effective than apoE-containing liposomes. We examined in B16 tumour-bearing mice the tumour-localizing properties of apoE liposomes and the disposition of an incorporated lipophilic derivative of daunorubicin (LAD). Tissue distribution studies showed that LAD-loaded apoE liposomes were taken up and processed by the major LDL receptor-expressing organs (i.e. adrenals, liver and spleen). Of all other tissues, the tumour showed the highest uptake. The distribution patterns of LAD-loaded apoE liposomes and native LDL in the tumour-bearing mice were very similar, which supports the role of the LDL receptor in the disposition of the prodrug-loaded particles. The disposition of LAD followed the pattern of the liposomal carrier. We conclude that apoE liposomes enable LDL receptor-mediated specific delivery of antineoplastic (pro)drugs to tumours, and, therefore, constitute an attractive novel option for anti-tumour chemotherapy.

Proteasome is a carrier to translocate doxorubicin from cytoplasm into nucleus

When an effective concentration of doxorubicin (DXR) was added into L1210 of a mouse leukemia cell line, DXR was rapidly distributed much more in the nuclei than in the other organelle within a few minutes. A [14C]DXR-binding fraction was obtained from the cytosol prepared from L1210 cells. The fraction was adsorbed to hydroxylapatite matrix and eluted from the matrix by 50-150 mM potassium phosphate buffer. The fraction showed high DXR-binding and Suc-Leu-Leu-Val-Tyr-MCA-degrading activity. The binding of [14C]DXR was inhibited by unlabeled DXR. Gel chromatography of the fraction with Sephacryl S-300 separated two fractions of high molecular weight (Peak I, approx. 750 kDa) and low molecular weight (Peak II). Peak I showed proteolytic activity. [14C]DXR-binding Peak I had much higher affinity to DNA-cellulose than [14C]DXR-binding Peak II. [14C]DXR-Peak I complex also was retained into the nuclei isolated from L1210 cells, temperature-dependently. These results suggest that a specific carrier to translocate DXR from cytoplasm into nucleus exists in L1210 cell and the carrier is proteasome.

Simultaneous determination of epirubicin, doxorubicin and their principal metabolites in human plasma by high-performance liquid chromatography and electrochemical detection

A high-performance liquid chromatographic method with electrochemical detection has been developed for the simultaneous determination of epirubicin, 13-S-dihydroepirubicin, doxorubicin and 13-S-dihydrodoxorubicin in human plasma. An aliquot of 200 microl plasma, spiked with internal standard, was extracted by solid-phase extraction using polymeric adsorbent columns. Chromatography was performed using a C18 reversed-phase column with a mobile phase consisting of water-acetonitrile (71:29, v/v) containing 0.05 M Na2HPO4 and 0.05% v/v triethylamine adjusted to pH 4.6 with citric acid. Linearity of the method was obtained in the concentration range of 1-500 ng/ml for all the analytes. Analytical recoveries of the analytes ranged from 89 to 93%. The assay can be used for the simultaneous determination of the four analytes, or for epirubicin and its metabolite or doxorubicin and its metabolite, using the other parent drug as an internal standard. The method was applied to analyze human plasma samples from patients treated with epirubicin using doxorubicin as an internal standard.

Effect of tamoxifen on the pharmacokinetics of doxorubicin in patients with non-Hodgkin's lymphoma

The authors examined the effect of tamoxifen (TAM), a multiple-drug resistance modulator, on the pharmacokinetics of doxorubicin (DOX) in patients with non-Hodgkin's lymphoma treated according to the CHOP-protocol which included DOX, cyclophosphamide, vincristine, and prednisone. The dose of DOX was 50 mg/m2, but was reduced 25% if the patient was older than 60 years. Of these, 10 randomly-selected patients received a daily dose of 480 mg of TAM (Group-1) and 10 others did not (Group-2). Blood samples were collected at different time intervals, and DOX was measured in plasma by liquid chromatography. The concentration-time data of DOX exhibited the characteristics of the two-compartment open model well. The mean (SEM) values of alpha, beta, k12, k21, k10, Vc, Vss, AUC, total clearance, and mean residence time observed in Group-1 were 4.06 (0.96) hr(-1), 0.0395 (0.0068) hr(-1), 3.13 (0.79) hr(-1), 0.264 (0.052) hr(-1), 0.708 (0.19) hr(-1), 525 (156) l/m2, 1060 (163) l/m2, 1145 (234) microg x hr/l, 49.3 (8.5) l/hr x m2, and 26.8 (6.6) hours, respectively. Those in Group-2 were 4.99 (1.13) hr(-1), 0.0432 (0.0073) hr(-1), 2.46 (0.63) hr(-1), 0.111 (0.026) hr(-1), 2.46 (0.86) hr(-1), 231 (53) l/m2, 812 (149) l/m2, 1690 (276) microg x hr/l, 30.3 (4.1) l/hr x m2, and 29.7 (5.1) hours, respectively. Of these parameters, the difference between the two groups was significant (p < or = 0.0169) only in k21. Thus, the coadministration of TAM at the earlier-mentioned dose appears generally to have no significant influence on the pharmacokinetics of doxorubicin when used in the CHOP-protocol.

Apoptosis-associated signaling pathways are required for chemotherapy-mediated female germ cell destruction

Female sterility resulting from oocyte destruction is an unfortunate, and in many cases inevitable, consequence of chemotherapy. We show that unfertilized mouse oocytes exposed to therapeutic levels of the antitumor drug, doxorubicin (DXR), undergo apoptosis; however, fertilized oocytes do not initiate apoptosis, but enter cell-cycle arrest, when treated with DXR. Apoptosis induced by DXR in oocytes is blocked by sphingosine-1-phosphate, an inhibitor of ceramide-promoted cell death. Oocytes from Bax-deficient, but not p53-null, female mice display complete resistance to DXR-induced apoptosis in vivo and in vitro. Pretreatment of oocytes with a specific peptide inhibitor of caspases also abrogates the apoptotic response to DXR. These findings indicate that oocyte destruction caused by chemotherapy can be prevented by manipulation of apoptosis-associated signaling pathways.

Population pharmacokinetics and pharmacodynamics of pegylated-liposomal doxorubicin in patients with AIDS-related Kaposi's sarcoma

OBJECTIVE

To characterize the population pharmacokinetics of pegylated-liposomal doxorubicin in patients with acquired immunodeficiency disease (AIDS)-related Kaposi's sarcoma and to explore the relationship between response of the cutaneous Kaposi's sarcoma lesions to treatment and measures of drug exposure.

METHODS

Forty-three male patients (median age, 40 years; age range, 28 to 50 years), body surface area, 1.89 m2; range, 1.5 to 2.3 m2) with AIDS and at least five biopsy-proven cutaneous Kaposi's sarcoma lesions were randomized to receive either a 10 or 20 mg/m2 dose of study drug for their first cycle and the alternate dose 3 weeks later. Patients continued to receive the study drug at a dose of 20 mg/m2 every 3 weeks. Serial blood samples were obtained after the first two doses and analyzed by HPLC for determination of total plasma doxorubicin concentration. Kaposi's sarcoma lesion response was categorized as either progressive disease, stable disease, partial response, or complete response. Classification and regression tree (CART) analysis was used to determine the relationship between drug exposure and categorical lesion response. Iterative two-stage analysis was used to characterize both the pharmacokinetics of pegylated-liposomal doxorubicin and to model the probabilities of achieving a specific lesion response.

RESULTS

The pharmacokinetics of pegylated-liposomal doxorubicin were best described by a two-compartment linear structural model. Lesion response was significantly related to both the average daily maximum doxorubicin concentration (Cmax,avg) and dose intensity.

CONCLUSIONS

The pharmacokinetics of pegylated-liposomal doxorubicin are strikingly different from conventional doxorubicin. Identification of both Cmax,avg and dose intensity as predictors of lesion response will provide guidelines for future dosing regimen designs.

Receptor-mediated uptake of low-density lipoprotein by B16 melanoma cells in vitro and in vivo in mice

Selective delivery of cytotoxic anti-neoplastic drugs can diminish the severe side-effects associated with these drugs. Many malignant tumours express high levels of low-density lipoprotein (LDL) receptors on their membranes. Therefore, LDL may be used as a carrier to obtain selective delivery of anti-neoplastic drugs to tumours. The present study was performed to investigate the feasibility of the murine B16 tumour/mouse model for the evaluation of LDL-mediated tumour therapy. LDL binds with high affinity to LDL receptors on cultured B16 cells (Kd, 5.9 +/- 2.3 micrograms ml-1; Bmax 206 +/- 23 ng LDL mg-1 cell protein). After binding and internalisation, LDL was very efficiently degraded: 724 +/- 19 ng LDL mg-1 cell protein h-1. Chloroquine and ammonium chloride completely inhibited the degradation of LDL by the B16 cells, indicating involvement of lysosomes. LDL receptors were down-regulated by 70% after preincubation of B16 cells with 300 micrograms ml-1 LDL, indicating that their expression is regulated by intracellular cholesterol. To evaluate the uptake of LDL by the B16 tumour in vivo, tissue distribution studies were performed in C57/B1 mice inoculated with B16 tumours. For these experiments, LDL was radiolabelled with tyramine cellobiose, a non-degradable label, which is retained in cells after uptake. At 24 h after injection of LDL, the liver, adrenals and the spleen were found to be the major organs involved in LDL uptake, with tissue-serum (T/S) ratios of 0.82 +/- 0.08, 1.17 +/- 0.20 and 0.69 +/- 0.08 respectively. Of all the other tissues, the tumour showed the highest uptake of LDL (T/S ratio of 0.40 +/- 0.07). A large part of the LDL uptake was receptor mediated, as the uptake of methylated LDL was much lower. Although the LDL uptake by the liver, spleen and adrenals is higher than that by the tumour, the LDL receptor-mediated uptake by these organs may be selectively down-regulated by methods that do not affect the expression of LDL receptors on tumour cells. It is concluded that the B16 tumour-bearing mouse constitutes a good model to evaluate the effectiveness of LDL-mediated delivery of cytotoxic (pro)drugs to tumours in vivo.

Clinically significant drug interactions with cyclosporin. An update

Since its approval in 1983 for immunosuppressive therapy in patients undergoing organ and bone marrow transplants, cyclosporin has had a major impact on organ transplantation. It has significantly improved 1-year and 2-year graft survival rates, and decreased morbidity in kidney, liver, heart, heart-lung and pancreas transplantation. Several studies have supported the efficacy of cyclosporin in preventing graft-versus-host disease in bone marrow transplantation. Cyclosporin is also possibly effective in treating diseases of autoimmune origin and as an antineoplastic agent. The introduction of therapeutic drug monitoring of cyclosporin was extremely useful because of the wide inter- and intraindividual variability in the pharmacokinetics of cyclosporin after oral or intravenous administration. Optimal long term use of cyclosporin requires careful monitoring of the blood (or plasma) concentrations. Sustained and clinically significant drug-drug interactions can occur during long term therapy with cyclosporin. The coadministration of multiple drugs with cyclosporin could result in graft rejection, renal dysfunction or other undesirable effects. Any interaction that leads to modified cyclosporin concentrations is of potential clinical importance. Cyclosporin itself may have significant effects on the pharmacokinetics and/or pharmacodynamics of coadministered drugs, such as digoxin, HMG-CoA reductase inhibitors and antineoplastic drugs affected by multidrug resistance. Many drugs have been shown to affect the pharmacokinetics and/or pharmacodynamics of cyclosporin. Interactions between cyclosporin and danazol, diltiazem, erythromycin, fluconazole, itraconazole, ketoconazole, metoclopramide, nicardipine, verapamil, carbamazepine, phenobarbital (phenobarbitone), phenytoin, rifampicin (rifampin) and cotrimoxazole (trimethoprim/sulfamethoxazole) are well documented in a large number of patients. Other interactions (such as those with aciclovir, estradiol and imipenem) are documented only in isolated case studies.

Doxorubicin encapsulated in liposomes containing surface-bound polyethylene glycol: pharmacokinetics, tumor localization, and safety in patients with AIDS-related Kaposi's sarcoma

A study of the plasma pharmacokinetics, tumor localization, and safety of a single dose of doxorubicin encapsulated in liposomes containing surface-bound polyethylene glycol (PEG-liposomal doxorubicin) was conducted in patients with Kaposi's sarcoma (KS) as a manifestation of acquired immune deficiency syndrome (AIDS). Eighteen patients with AIDS-KS diagnosed by examination of biopsy specimens were randomly assigned to receive either standard doxorubicin or PEG-liposomal doxorubicin. Consecutive participants were entered at three dose levels (10, 20, and 40 mg/m2) in ascending fashion. Clearance of PEG-liposomal doxorubicin was 0.034 L/h/m2 to 0.108 L/h/m2, volume of distribution (Vd) was 2.2 L/m2 to 4.4 L/m2, and half-lives (t1/2) of the initial decline in the plasma concentration-time curve and of the terminal decline were 3.77 hours and 41.3 hours, respectively. Seventy-two hours after administration, doxorubicin levels observed in lesions of patients receiving PEG-liposomal doxorubicin were 5.2 to 11.4 times greater than those found in patients given comparable doses of standard doxorubicin. PEG-liposomal doxorubicin and standard doxorubicin were roughly equipotent in producing toxicity. Encapsulation in liposomes containing surface-bound PEG significantly limits the distribution and elimination of doxorubicin, results in greater accumulation of the drug in KS lesions 72 hours after dosing than does standard doxorubicin, and may improve drug efficacy and therapeutic index in the treatment of AIDS-KS.

The role of human cytochrome P450 enzymes in the metabolism of anticancer agents: implications for drug interactions

1. Little information is available about the pharmacokinetic interactions of anticancer drugs in man. However, clinically significant drug interactions do occur in cancer chemotherapy, and it is likely that important interactions have not been recognized. 2. Specific cytochrome P450 (CYP) enzymes have been recently shown to be involved in the metabolism of several essential anticancer agents. In particular, enzymes of the CYP3A subfamily play a role in the metabolism of many anticancer drugs, including epipodophyllotoxins, ifosphamide, tamoxifen, taxol and vinca alkaloids. CYP3A4 has been shown to catalyse the activation of the prodrug ifosphamide, raising the possibility that ifosphamide could be activated in tumour tissues containing this enzyme. 3. As examples of recently found, clinically significant interactions, cyclosporin considerably increases plasma doxorubicin and etoposide concentrations. Although cyclosporin and calcium channel blockers may influence the pharmacokinetics of certain anticancer agents by inhibiting their CYP3A mediated metabolism, it is more likely that these P-glycoprotein inhibitors inhibit P-glycoprotein mediated drug elimination. 4. Appropriate caution should be exercised when combining P-glycoprotein inhibitors and potential CYP3A inhibitors with cancer chemotherapy.

Pharmacokinetics of two different delivery regimens of doxorubicin in isolated hyperthermic limb perfusion

Evaluation of doxorubicin (DOX) pharmacokinetics in hyperthermic isolated limb perfusion (HILP) is limited. In this study two administration regimens of DOX were compared in terms of area under the time concentration curve (AUC) in plasma. HILP was performed in 13 dogs. In group 1 (n = 7) four single doses of DOX were injected in intervals of 15 minutes, in group 2 (n = 6) DOX was administered continuously during the first 30 min. The total dose in both groups was 1 mg/kg body weight, and the perfusion lasted 60 min. Concentrations of DOX and its major metabolite doxorubicinol (DOXol) were measured in perfusate and muscle tissue by high performance liquid chromatography (HPLC). Pharmacokinetic estimates were calculated. The two investigated administration modes provided sufficient drug levels of DOX during the whole perfusion time. Maximum concentrations in the perfusate and areas under the time concentration curves were nearly the same. The tissue concentrations also did not show significant differences. Both regimens are practicable avoiding high peak levels of the drug in order to minimize toxic side effects.

Distribution, metabolism and tumoricidal activity of doxorubicin administered in sorbitan monostearate (Span 60) niosomes in the mouse

PURPOSE

Encapsulation of doxorubicin in niosomes was sought as a route to tumour targeting and improved tumoricidal through the alteration of doxorubicin pharmacokinetics and metabolism.

METHODS

Doxorubicin niosomes (10 mg kg-1 doxorubicin) prepared from sorbitan monostearate (Span 60), cholesterol and choleth-24 (a 24 oxyethylene cholesteryl ether) in the molar ratio 45:45:10 were administered intravenously to female NMRI mice bearing the MAC 15A subcutaneously implanted tumour. Plasma doxorubicin was fractionated by gel filtration and quantified by HPLC with fluorometric detection as niosome-associated doxorubicin and released doxorubicin. Tumoricidal activity of the formulation was assessed by the intravenous injection of 5 mg kg-1 and 10 mg kg-1 doxorubicin niosomes to male NMRI mice bearing a 6 day old MAC 15A tumour.

RESULTS

At least 90% of the plasma doxorubicin was associated with the niosome fraction 4 h after dosing, and 50% was still associated after 24 h. The clearance of doxorubicin released from the niosomes was about 10 fold greater than the clearance of niosomal doxorubicin (176.5 mL h-1 and 16.2 mL h-1, respectively). The area under the plasma level-time curve increased 6 fold when doxorubicin was administered in niosomes, compared to doxorubicin solution (66.0 micrograms.h mL-1 and 10.3 micrograms. h mL-1, respectively). The area under the tumour level time curve was increased by over 50% by the administration of doxorubicin in niosomes when compared to the drug administered in solution (58.6 micrograms.h mL-1 and 34.3 micrograms.h mL-1, respectively). There was no statistically significant difference between levels of the drug in the heart when niosomal doxorubicin or doxorubicin solution were administered. Doxorubicin metabolites, namely doxorubicinol and the aglycones doxorubicinone, doxorubicinolone and 7-deoxydoxorubicinone, were found associated with the niosomes in the plasma, possibly due to their adsorption to the vesicle surface once formed outside the niosome. Overall metabolite levels in the liver were increased when doxorubicin niosomes were administered compared to the drug in solution. A 5 mg kg-1 injection of doxorubicin niosomes produced a terminal mean tumour weight that was similar to that obtained from animals administered 10 mg kg-1 doxorubicin solution.

CONCLUSIONS

Modest tumour targeting was achieved by the delivery of doxorubicin in sorbitan monostearate niosomes, increasing the tumour to heart AUC0-24 ratio from 0.27 to 0.36 and a doubling of tumoricidal activity. The overall level of doxorubicin metabolites was also increased.

Pharmacokinetics of doxorubicin co-administered with high-dose verapamil

The potential for the modification of the pharmacokinetics of doxorubicin (DOX) concurrently administered with high-dose verapamil (VER) has been investigated in 17 patients with advanced neoplasms refractory to drugs belonging to the multidrug resistance spectrum. Steady-state concentration of DOX, systemic clearance and urinary excretion were analysed. No significant difference was found between the kinetic parameters estimated for DOX at different levels of VER and those reported for doxorubicin as single agent. It can be concluded that VER does not appear to modify DOX kinetics.

Drug distribution and a pulmonary adverse effect of intraperitoneally administered doxorubicin niosomes in the mouse

Niosomes (non-ionic surfactant vesicles) prepared from C16G2 (a hexadecyl-diglycerol ether), and loaded with doxorubicin, were administered intraperitoneally to male AKR mice at dose levels of 0, 2.5, 5.0, and 10.0 mg kg-1. Free drug was given at 10.0 mg kg-1 by the intraperitoneal route. At a dose level of 10.0 mg kg-1, peak doxorubicin levels in the central compartment were attained faster with the free drug than with the niosome formulation. However, the peak plasma levels were similar for the free drug and the niosome preparation at the 10 mg kg-1 dose level. With doxorubicin administered as the niosome preparation by the intraperitoneal route at 2.5, 5.0, and 10.0 mg kg-1, mean peak plasma concentrations of the drug showed a tendency to be dose-related although the differences were not significant. Over the 24 h period of the experiment, with doxorubicin at 10 mg kg-1, the niosome formulation delivered significantly more drug to the plasma compartment than the free drug (p < 0.05). When doxorubicin was given in niosomes at 2.5, 5.0 and 10.0 mg kg-1 by the intraperitoneal route, the resulting levels of doxorubicin in cardiac tissue were not dose related and the differences not significant and, although the mean peak cardiac-tissue concentration was higher in animals receiving the free drug at 10.0 mg kg-1 intraperitoneally than in mice given intraperitoneal doxorubicin niosomes at this dose level, the differences were again not significant. There were clinical signs of toxicity in mice given doxorubicin-containing niosomes intraperitoneally at 5.0 and 10.0 mg kg-1, and at post-mortem an accumulation of fluid in the pleural cavity was evident. These changes were not seen in mice dosed intraperitoneally with free drug at 10 mg kg-1, or in animals given doxorubicin niosomes intraperitoneally at 2.5 mg kg-1. In mice dosed intraperitoneally with doxorubicin niosomes at 12.0 mg kg-1 and at a dose volume of 0.2-0.4 mL, histological examination of the lungs demonstrated a congestion of the alveolar capillaries, and an increased number of acute inflammatory cells in the alveolar walls. There was no histological evidence of lung toxicity in mice dosed with doxorubicin niosomes at 12.0 mg kg-1 when the formulation was administered with the higher dose volume of 1.8-2.0 mL. Importantly there was no histological evidence of lung toxicity in mice dosed with empty niosomes intraperitoneally or with doxorubicin niosomes given intravenously at 12.0 mg kg-1.

The effects of cyclosporine on the pharmacokinetics of doxorubicin in patients with small cell lung cancer

BACKGROUND

The authors compared the pharmacokinetics of doxorubicin when administered with and without concomitant high dose cyclosporine for multidrug resistant (MDR) tumor modulation in small cell lung cancer.

METHODS

Eight patients with small cell lung cancer served as their own controls and were studied first during an initial course of doxorubicin without cyclosporine, and then subsequently during a cyclosporine-modulated doxorubicin course. All patients received cyclophosphamide and vincristine in each course. Doxorubicin was administered as a 1-hour infusion after a 2-hour cyclosporine loading infusion, and cyclosporine was infused continuously for the next 48 hours. Serum concentrations of doxorubicin, doxorubicinol, and cyclosporine all were assayed by high-pressure liquid chromatography. Pharmacokinetic analysis of doxorubicin included area under the curve (AUC), clearance, apparent volume of distribution at steady state (Vss), and elimination half-life (T1/2). The percent of change and surviving fraction of leukocyte count and platelets were determined as pharmacodynamic indices.

RESULTS

Cyclosporine modulation increased the AUC0-36 of doxorubicin by 48% (P = 0.042) and the AUC0-36 of doxorubicinol by 443% (P = 0.0001), whereas the doxorubicin clearance declined by 37% (P = 0.0495). No difference was found in the Vss or T1/2 for doxorubicin when cyclosporine was added to the regimen. The ratio of the doxorubicinol AUC0-36 to the doxorubicin AUC0-36 increased significantly with cyclosporine modulation (8.88 vs. 2.19; P = 0.001). Drug-related toxicity was also greater with the cyclosporine-modulated course of doxorubicin. A 91% reduction in the leukocyte count followed the modified course, compared with an 84% reduction following the initial course (P = 0.0074). A more prolonged and greater degree of myelosuppression was observed and a significant relationship was found between the systemic exposure to doxorubicin (defined by AUC) and the surviving fraction of the leukocyte count (r = -0.69; P = 0.006). Similarly, the reduction in the platelet count was significantly greater after the cyclosporine-modulated course (72.8%) than after the initial course (36.4%) (P = 0.0016). A significant correlation was found between the AUC of doxorubicinol and the surviving fraction of platelets (r = -0.71; P = 0.004). In addition, patients showed decreased performance status associated with significant weight loss and severe myalgias.

CONCLUSIONS

The addition of high dose cyclosporine for MDR modulation resulted in the significant alteration of doxorubicin disposition and remarkable toxicity in all patients. The mechanisms responsible for the decreased doxorubicin clearance may include cyclosporine's ability both to interfere with P-glycoprotein in normal tissues and to selectively inhibit the cytochrome P-450 enzyme system. Further study of this potentially significant drug-drug interaction is warranted.

Degradation and intrahepatic compatibility of albumin-heparin conjugate microspheres

The in vitro degradation properties of glutaraldehyde cross-linked albumin and albumin-heparin conjugate microspheres (AMS and AHCMS respectively) were evaluated using light microscopy, turbidity measurements and heparin release determinations, showing that the microspheres are degraded by proteolytic enzymes such as trypsin, proteinase K and lysosomal enzymes. The degradation rate was inversely related to the cross-link density of the microspheres. After intrahepatic administration of AHCMS, cross-linked with 0.5% glutaraldehyde, to male Wag/Rij rats by injection into a mesenteric vein (intravenoportal: i.v.p.), the microspheres were entrapped in the hepatic vascular system. The AHCMS were entrapped within terminal portal veins predominantly at the periphery of the liver. The AHCMS were degraded by cellular enzymatic processes within 2 wk after injection, with a half life of approximately 1 d. Biocompatibility of AHCMS and adriamycin-loaded AHCMS was evaluated by histological assessment of the mitotic activity of liver parenchyma and inflammatory response, and by determination of liver damage marker enzymes during 4 wk after administration. Liver damage marker enzymes were not increased compared with controls, nor were adverse effects observed upon histological examination. There was no difference in response between empty and adriamycin-loaded AHCMS.

Hepatic intra-arterial administration of doxorubicin and degradable starch microspheres. A pharmacokinetic study in the rat

Urinary concentration of doxorubicin and its active metabolite doxorubicinol was followed in two groups of rats after hepatic intra-arterial injection of a single dose of 6 mg/kg doxorubicin or the same dose combined with 30 mg/kg Spherex (DSM). Urinary samples were collected during five days following administration. The concomitant DSM administration caused a significant decrease of the cumulative urinary excretion of intact doxorubicin; average five days of cumulative values were 73 and 103 micrograms respectively in the group with and without DSM. This indicates a DSM-induced reduction in systemic drug exposure. The elimination rates of doxorubicin or its active metabolite were not influenced by DSM. The decrease in excretion of the parent drug was not due to an interaction between the drug and DSM as evident by examining the binding of doxorubicin to DSM in vitro. Instead regionally altered drug distribution seems a plausible explanation to the reduction.