Michael P. Gosland

Alteration of etoposide pharmacokinetics and pharmacodynamics by cyclosporine in a phase I trial to modulate multidrug resistance.

PURPOSE To determine the effects of high-dose cyclosporine (CsA) infusion on the pharmacokinetics of etoposide in patients with cancer. PATIENTS AND METHODS Sixteen patients were administered 20 paired courses of etoposide and CsA/etoposide. Etoposide was administered daily for three days, alone or with CsA, which was delivered by a loading dose and 3-day infusion. Etoposide was measured by high-performance liquid chromatography (HPLC) and serum CsA by nonspecific immunoassay. Etoposide pharmacokinetics included area under the concentration-time curve (AUC), total and renal clearance (CL), half-life (T1/2), and volume of distribution at steady state (Vss). RESULTS CsA concentrations more than 2,000 ng/mL produced an increase in etoposide AUC of 80% (P less than .001), a 38% decrease in total CL (P < .01), a > twofold increase in T1/2 (P < .01), and a 46% larger Vss (P = .01) compared with etoposide alone. CsA levels ranged from 297 to 5,073 ng/mL. Higher CsA levels (< 2,000 ng/mL v > 2,000 ng/mL) resulted in greater changes in etoposide kinetics: Vss (1.4% v 46%) and T1/2 (40% v 108%). CsA produced a 38% decrease in renal and a 52% decrease in nonrenal CL of etoposide. Etoposide with CsA levels > 2,000 ng/mL produced a lower WBC count nadir (900/mm3 v 1,600/mm3) compared with baseline etoposide cycles. CONCLUSIONS High-dose CsA produces significant increases in etoposide systemic exposure and leukopenia. These pharmacokinetic changes are consistent with inhibition by CsA of the multidrug transporter P-glycoprotein in normal tissues. Etoposide doses should be reduced by 50% when used with high-dose CsA in patients with normal renal and liver function. Alterations in the disposition of other multidrug resistance (MDR)-related drugs should be expected to occur with modulation of P-glycoprotein function in clinical trials.

Phase I trial of etoposide with cyclosporine as a modulator of multidrug resistance.

PURPOSE To determine the maximum-tolerated dose (MTD) of cyclosporine (CsA) infusion administered with etoposide for 3 days in patients with cancer. PATIENTS AND METHODS Of the 72 registered patients, 26 were treated initially with CsA and etoposide. Forty-six received etoposide alone until disease progression, and 31 of these proceeded to CsA and etoposide. CsA was administered as a 2-hour loading dose (LD) and as a 3-day continuous infusion (CI); doses were escalated from 2 to 8 mg/kg LD and 5 to 24 mg/kg/d CI. RESULTS Fifty-seven patients were treated with 113 cycles of CsA with etoposide. Steady-state serum CsA levels (nonspecific immunoassay) more than 2,000 ng/mL were achieved in 91% of the cycles at CsA doses > or = 5 mg/kg LD and > or = 15 mg/kg/d CI. The major dose-related toxicity of CsA was reversible hyperbilirubinemia, which occurred in 78% of the courses with CsA levels > 2,000 ng/mL. Myelosuppression and nausea were more severe with CsA and etoposide. Other CsA toxicities included hypomagnesemia, 60%; hypertension, 29%; and headache, 21%. Nephrotoxicity was mild in 12% and severe in 2% of the cycles. Tumor regressions occurred in four patients after the addition of CsA (one non-Hodgkins lymphoma, one Hodgkins disease, and two ovarian carcinomas). Biopsy procedures for tumors from three of the four patients who responded were performed, and the results were positive for mdr1 expression. CONCLUSIONS Serum CsA levels of up to 4 mumol/L (4,800 ng/mL) are achievable during a short-term administration with acceptable toxicities when administered in combination with etoposide. The CsA dose that is recommended in adults is a LD of 5 to 6 mg/kg, followed by a CI of 15 to 18 mg/kg/d for 60 hours. CsA blood levels should be monitored and the doses should be adjusted to achieve CsA levels of 2.5 to 4 mumol/L (3,000 to 4,800 ng/mL). Reversible hyperbilirubinemia may be a useful marker of inhibition by CsA of P-glycoprotein function. When used with high-dose CsA, etoposide doses should be reduced by approximately 50% to compensate for the pharmacokinetic effects of CsA on etoposide (Lum et al, J Clin Oncol, 10:1635-1642, 1992).

Molecular Targets in Oncology: Implications of the Multidrug Resistance Gene

The curative potential of chemotherapy for a number of tumor types has been obscured by the fact that many patients initially have striking remissions but later relapse and die. At the time of relapse many patients manifest resistance to a wide array of structurally unrelated antineoplastic agents, hence the term multidrug resistance (MDR). Other tumor types, such as those arising in the colon, kidneys, liver, and lungs, tend to exhibit poor response to available cytotoxic drugs. The MDR phenomenon includes cross‐resistance among the anthracyclines (doxorubicin, daunorubicin), the epipodophyllotoxins (etoposide, teniposide), the vinca alkaloids (vinblastine, vincristine), taxol, and other compounds. In vitro studies in cell culture indicate that this form of resistance is associated with amplification or overexpression of the mdrl gene. The mdrl gene codes for the expression of a cell surface protein, P‐glycoprotein (P‐gp), which acts as an energy‐dependent efflux pump that transports drugs associated with MDR out of the cell before cytotoxic effects occur. The protein is expressed in normal human tissues such as the gastrointestinal tract, liver, and kidneys, where it is thought to serve as an excretory pathway for xenobiotic drugs and toxins. Preliminary studies demonstrated the presence of P‐gp in tumor samples from patients with acute leukemia, multiple myeloma, lymphomas, and a variety of solid tumors. A number of drugs are able to reverse MDR, including calcium‐channel blockers, phenothiazines, quinidine, antimalarial agents, antiestrogenic and other steroids, and cyclosporine. Limited results from clinical trials with small numbers of patients suggest that the addition of verapamil, diltiazem, quinine, trifluoperazine, or cyclosporine to chemotherapeutic regimens has the potential to reverse MDR; however, toxicities limit their clinical usefulness. A number of trials are under way to identify more active and less toxic modulators of MDR.

Analysis of blood T‐cell cytokine expression in B‐chronic lymphocytic leukaemia: evidence for increased levels of cytoplasmic IL‐4 in resting and activated CD8 T cells

The cytoplasmic cytokines of purified blood T cells (CD4/C]D8) in B‐CLL patients (n = 5) and controls (n =5) were evaluated by flow cytometry. The mean levels of cytoplasmic IL‐4 were significantly elevated in resting and activated B‐CLL CD8 cells compared to control CD8 cells. IL‐4 cytoplasmic levels were comparable for resting B‐CLL and control CD4 cells but greater for B‐CLL activated CD4 cells. The mean fluorescence intensity of B‐CLL CD8 cytoplasmic IL‐4 was 4–5‐fold greater, indicating higher IL‐4 density per CLL CD8 than control CD8 cells. Both CLL CD4 and CD8 cells post‐activation had higher levels of cells double positive for cytoplasmic IL‐4 and interferon. These data indicate that freshly isolated CD8 and CD4 blood T cells from B‐CLL patients have significantly elevated (above control) levels of commitment to expression of IL‐4. Since IL‐4 has an important modulatory impact on CLL and normal B cells, this observation has implications regarding the biology of B‐CLL.

The use of probenecid as a chemoprotector against cisplatin nephrotoxicity

Probenecid inhibits cisplatin (CP) secretion in humans and protects against CP‐induced nephrotoxicity in rats. The authors conducted a Phase I trial of escalating doses of CP using probenecid as a chemoprotector. Fifty‐four courses of CP at doses ranging from 100 to 160 mg/m2 were given by 24‐hour infusion to 36 patients. There was no renal impairment at any dose. Ototoxicity, however, became the dose‐limiting toxicity; 14 patients experienced a 20 or greater decibel (dB) loss. Seven percent of courses were associated with a leukocyte count of less than 1.5 × 10/μ1, and 19% with a platelet count of less than 50 × 103/μ1. Only three patients developed neurotoxicity. Correlating pharmacokinetic data and toxicity, the authors found that high cumulative dose, area under the curve (AUC) for unbound platinum, and cumulative AUC were associated with ototoxicity and peripheral neuropathy. It was concluded that probenecid may protect against CP nephrotoxicity and warrants further investigation. Its unique mechanism of action and lack of toxicity make it ideal to combine with other chemoprotectors.

Reversal of doxorubicin, etoposide, vinblastine, and taxol resistance in multidrug resistant human sarcoma cells by a polymer of spermine

Abstract We have previously descibed the synthesis of a cytotoxic polymeric conjugate of spermine (Poly-SPM) which is able to inhibit the transport of polyamines (spermine, spermidine, and putrescine) into normal and malignant cells. Recent studies examining the toxicity of Poly-SPM in parental and multidrug resistant (MDR) cancer cells have revealed a cross- resistance in the MDR variant Dx5 to the toxic effects of the conjugate in the MDR-positive cells. There were also differences in spermine and putrescine uptake rates between parental and MDR-positive cells with the MDR-positive cells having a lower Vmax and a higher Km. The ability of this Poly-SPM to reverse MDR was examined in MDR variants (Dx5 cells) of the human sarcoma cell line MES-SA. The cells express high levels of the mdr1 gene product, P-glycoprotein, and are 25- to 60-fold resistant to doxorubicin (DOX), etoposide (VP-16), vinblastine (VBL), and taxol (TAX). Cytotoxicity was measured by the MTT [3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Poly-SPM (50 μM) lowered the drug concentration IC50 values in the Dx5 cells by 37-fold with VBL, 42-fold with DOX, 29-fold with VP-16, and 25-fold with TAX when compared to the control IC50 values without Poly-SPM. This reversal of resistance was concentration dependent, decreasing 17-fold with DOX, 6.1-fold with VBL, 19-fold with VP-16, and 5-fold with TAX when 25 μM Poly-SPM was used. No modulation was observed in the parental cell line MES-SA, which does not express the mdr1 gene. Poly-SPM had no influence on the IC50 of non-MDR chemotherapeutic agents such as cisplatin. The modulation studies correlated with the ability of Poly-SPM to reverse the cellular accumulation defect of [3H]-VBL and [3H]-TAX in the Dx5 but not MES-SA cells. Pretreatment of the Dx5 cells with α-difluoromethylornithine (DFMO at 2 and 5 μM) for 24 h increased the function of the MDR transporter to further decrease the cellular accumulation of VBL and TAX when compared to untreated cells. DFMO pretreatment is known to up-regulate the polyamine transporter(s). These findings show that, in addition to inhibiting polyamine transport, Poly-SPM reverses MDR in Dx5 cells, suggesting a potential relationship between the polyamine influx transporter and the MDR efflux pump. This potential functional link between the polyamine influx transporter(s) and the MDR efflux transporter (P-glycoprotein) offers a novel approach to inhibiting this form of drug resistance.

Modulation effects of cyclosporine on etoposide pharmacokinetics and CNS distribution in the rat utilizing microdialysis

In the present study, we evaluated the pharmacokinetics of the chemotherapeutic agent etoposide (ET) under steady-state conditions and examined its extent of distribution into the CNS of conscious animals. An i.v. infusion of 15 mg/kg/hr was administered to nine rats. Each of the nine rats also received the potent multidrug resistance (MDR) modulator cyclosporine (CSA). Upon the addition of CSA, the i.v. treated animals demonstrated a 53% decrease in ET clearance. This decrease resulted in a greater than 2-fold increase in the steady-state concentrations of ET> The corrected brain-blood ratio (BBR (corr)) was 0.36 +/- 0.18 prior to CSA treatment, and although CNS concentrations increased upon the addition of CSA, there was no increase in the BBR(corr) (0.24 +/- 0.10). The present study demonstrates that the increase of ET in the CNS following CSA is a result of a decrease in ET systemic clearance and not an inhibition of ET efflux from the CNS.

A phase I trial of 5-day continuous infusion cisplatin and interferon α

Combination therapy of cisplatin with interferon α (IFN) has been shown in several in vitro as well as in vivo models to be synergistic. In order to decrease toxicity seen with cisplatin, 5-day continuous infusions, in place of bolus administration, have been introduced. This led us to investigate the combination of 5-day continuous infusion cisplatin with repeated IFN dosing in a phase I cisplatin dose escalation study. A group of 17 patients were enrolled in this trial. The maximum tolerated dose (MTD) of cisplatin was 20 mg/m2 per day when combined with 3×106 units IFN given three times a week. The dose-limiting toxicities seen included thrombocytopenia, leukopenia, and nausea and vomiting. Pharmacokinetic analyses of free (unbound or ultrafilterable) platinum revealed that the decay curve fitted a monoexponential model. Pharmacokinetic parameters of cisplatin were found to correlate with toxicity. Both increases in the maximum concentration of cisplatin achieved (Cpmax) as well as the area-under-the-curve (AUC) for free platinum, correlated with the incidence of nausea and vomiting (both acute and delayed) and hematological toxicities (leukopenia and thrombocytopenia). None of the patients exhibited significant changes in renal function while on this study. The free platinum levels were higher than found in similar studies evaluating comparable cisplatin infusions alone. The enhanced toxicities seen in this trial may be explained by the results of an in vitro study using human plasma spiked with cisplatin and IFN that revealed decreased protein binding of cisplatin by 2.5–3.0-fold. Of the 17 patients treated, two non-small cell lung cancer patients obtained a partial response and one malignant melanoma patient obtained complete resolution of a malignant pleural effusion. Considering the acceptable toxicity seen in this trial, we recommend phase II trials be conducted with continuous infusion cisplatin with IFN in the treatment of non-small cell lung cancer.

The Anticancer Drugs, 2nd EditionThe Anticancer Drugs, 2nd Edition By PrattWilliam B., RuddonRaymond W., EnsmingerWilliam D., and MaybaumJonathan. Published by Oxford University Press, New York, 1994. ISBN 0-19-506739-8. Paperbound, 352 pp. (25 × 17.5 cm),

The novice to the field of oncology is provideda concise up-to-date review of cancer chemotherapywith this book.The authors are establishedexperts in the field of cancer pharmacology. The authors state in the preface that the aim of the text is to help the readerunderstand the rationale for chemotherapywith respect to the biologyof the cancer cell and to tumorgrowthkinetics. This aim is achieved by presenting material in a form that integrates fundamental knowledge areas,drawingfrom the fields of medicinal chemistry, pharmacology, biochemistry, cell biology, molecular biology, pathophysiology, epidemiology, and clinical pharmacology and toxicology. The text is divided into4 parts. Part 1 reviews the principles of cancer chemotherapy, presenting 4 chapters, in whichthe first statesthe cancer problem in terms of cancer epidemiology,causation, survival,and the role of chemotherapy. Chapter 2 provides an entertaining historical overviewof the developmentof anticancerdrugs.This section also explainshow discoveries in the areasof biochemistry and molecular biology led to the development of many chemotherapeutic agents.Chapter3 reviews cell biologyand tumorgrowthkinetics as a determinant of drug responsiveness, interweaving the criticalconceptsof tumorsite,cytokinetics,drug scheduling, circadian timingof chemotherapy, and the immune system. Chapter 4 focuses on drug resistance. This chapter outlines the currentmechanisms of drug resistance, and begins to show the importance of molecular biology toolsin understanding resistance through gene amplification and multidrugresistance. This chapter also presents specific data to support these mechanisms of drug resistance, which makethe overallconcepts easierfor the readerto understand. Part 2 provides5 chapters that reviewanticancerdrug classes,effectively integrating conceptsderivedfrom our knowledge of these agents from biochemistry, molecularbiology,pharmacology, clinicaluse, and toxicity. The figures thatdepictchemicalstructure, metabolic pathways, and cancer pharmacology in this sectionmake theseprinciples easier for the readerto understand and integrate. Part 3 describesclinicalcancer therapy.The first chapter in this section describesfactors influencingthe choice of drugs in cancer chemotherapy, such as the type of tumor, the patient, therapeutic goals (i.e., cure or palliation), typesof treatment(combination chemotherapy, adjuvant,neoadjuvant, radiosensitization), and principles for the clinicaluse of anticancerdrugs, such as tumor volume,the dose-response relationship, and toxicity.The second chapter in this section uses 4 important cancersto exemplify different usesof anticancer drugs,including testicular cancer, breastcancer,colorectalcancer, and nonsmallcell lung cancer.The treatment of thesecancersillustrates the widerangeof therapeutic goals encounteredin oncology.For example, treatmentof testicular cancer shows the potentialcurabilityof a solid tumor,and treatmentof breastand coloncancersillustrates adjuvant chemotherapy. Treatmentof metastaticbreast cancer demonstratespalliationof symptomswith improvedquality of life,and the treatment of metastatic colorectal and nonsmall cell lung cancers shows how to modestly improve survival rates andconductresearch to improvetreatment. Part 4 of this text outlinesnew directionsin cancer therapy. The first chapter discusses anticancer drug development: screening to discover newdrugs, use of chemosensitivity testingand tumormarkers, and drug delivery systemssuchas devices, liposomes, microspheres, and antibodies.To illustrate the widerangeof drugdevelopment, the authors provided a 6-pagetablelistingnew therapeutic agentsby cancer type,sponsor, Foodand DrugAdministration designation, and development status. The next chapter discusses biologic treatments of cancer, such as the cytokines, and alsogives the readeran introduction to neweraspects of biologic therapysuch as gene therapy,antisenseoligonucleotide therapy, modificationof tumor-cell antigenicity,and tumor vaccines.The final chapter again takesour current understanding of cellularand molecular biologyinto a practical discussion of new directions in anticancertherapy. This section outlines targets such as topoisomerase, DNA repair mechanisms, transcription factors, antisense oligonucleotides, oncogenes, andotherregulators of cellgrowth. Thesmall section on pharmacologicchernoprevention at the end of thischapterappearsout of placeor as a lateaddition. Giventhecurrent interest and the number of clinical trials in thisarea,moreemphasis could havebeengivenearlierin the text. The uniquenicheof this text is that it is conciseand affordable, witha style that allowsa studentor a new practitioner in the field of oncology to gain rapidly a firmunderstanding of the concepts and rationale of cancer chemotherapy. The fundamental conceptspresented with up-to-date discussions using the diversity of knowledge derived from medicinal chemistry, pharmacology, biochemistry, cell biology, molecular biology, pathophysiology, epidemiology, clinicalpharmacology, and toxicology make this text useful despite the anticipated rapid evolution of data in theseareas.This text is not intended to replaceother texts,such as Cancer Chemotherapy Handbook. 2nd Edition (RobertT. Dorr and Daniel D. Von Hoff, Appleton& Lange, Norwalk, CT, 1994),AmericanHospital Formulary ServiceDrugInformation (American Societyof Hospital Pharmacists, Bethesda, MD, 1994),or The Chemotherapy Sourcebook (Michael C. Perry,ed.,Williams & Wilkins, Baltimore, MD, 1992), whichwillcontinue to serveas the comprehensive sourcesof pharmacologic,toxicologic, and pharmaceutical information for anticancerdrugs in the daily activitiesof the oncologypractitioner. This textbookserves as a concise,well-organized, integrated sourcefor cancerchemotherapy pharmacology.