Etoposide dosage and pharmacodynamics

Novel Meta-iodobenzylguanidine and Etoposide Complex: Physicochemical Characterization and Mathematical Modeling of Anticancer Activity

It is hypothesized that meta-iodobenzylguanidine (MIBG) complexation with etoposide (VP-16) will improve drug solubility and specificity towards BE(2)C neuroblastoma (NB) cells, 90% of which are known to be MIBG avid. After MIBG and VP-16 interaction, the dry complex was analyzed for crystalline structure, surface morphology, solubility, and size distribution by X-ray powder diffraction (P-XRD), scanning electron microscopy (SEM), infrared (FTIR) and UV spectroscopy, and dynamic light scattering. After exposure to the complex, the cell viability and decay rates were assessed by the MTS assay and estimated using exponential decay models (EDM). Multi-factorial ANOVA and an independent t-test were used to assess for cell viability and solubility data, respectively. The resulting (1: 3 w/w) VP-16: MIBG complex had a mean diameter and zeta potential of 458.5 nm and 0.951 mV, respectively. It dramatically increased the drug apparent water solubility (~ 12-folds). This was ascribed to the formation of a VP-16/MIBG nanocrystalline state mainly governed by cation-π interactions, evidenced by FTIR, SEM, and P-XRD data following the complexation. The EDM relating percent cell viability to drug concentration yielded an excellent fit (r2 > 0.95) and enabled to estimate the IC50 values of both native drug and its complex: 6.2 μM and 5.23 μM, respectively (indicating a conservation of drug anticancer activity). The statistical results were consistent with those of the exponential decay models, indicating that MIBG does not inhibit the anticancer activity of VP-16. This study indicates that the VP-16/MIBG complexation improves VP-16 solubility without antagonizing its anticancer activity. Moreover, the efficiency of the EDM for drug IC50 estimation provides alternative mathematical method for such in vitro cytotoxicity studies.

Oral lipid nanomedicines: Current status and future perspectives in cancer treatment

Oral anticancer drugs have earned a seat at the table, as the need for homecare treatment in oncology has increased. Interest in this field is growing as a result of their proven efficacy, lower costs and positive patient uptake. However, the gastrointestinal barrier is still the main obstacle to surmount in chemotherapeutic oral delivery. Anticancer nanomedicines have been proposed to solve this quandary. Among these, lipid nanoparticles are described to be efficiently absorbed while protecting drugs from early degradation in hostile environments. Their intestinal lymphatic tropism or mucoadhesive/penetrative properties give them unique characteristics for oral administration. Considering that chronic cancer cases are increasing over time, it is important to be able to provide treatments with low toxicity and low prices. The challenges, opportunities and therapeutic perspectives of lipid nanoparticles in this area will be discussed in this review, taking into consideration the pre-clinical and clinical progress made in the last decade.

The amount of cytokine-release defines different shades of Sars-Cov2 infection

The recent outbreak of coronavirus disease (COVID 19), spreading from China all around the world in early 2020, has led scientists to investigate the immuno-mediated mechanisms underlying the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV2) infection. Depending on the amount of cytokines released as the result of the immunological activation induced by SARS-CoV2, three major clinical phenotypes can be identified: "mild",symbolized as a "drizzle" of cytokines, severe as a "storm", and critical as a "hurricane". In patients with mild symptoms, the release of pro-inflammatory cytokines is balanced to obtain a defense response against the virus which is often self-limiting and overcomes without tissue damage. In severe phenotype, resembling a "cytokine-release syndrome", SARS-CoV2 causes the lysis of the immune-mediators leading to a cytokine storm able to induce lung epithelium damage and acute respiratory distress syndrome. In critical patients, the immune response may become uncontrolled, thus the cytokine burst resembles a form of secondary hemophagocytic lymphohistiocytosis which may result in a multi organ failure. In addition to the standard of care, an immune-modulatory therapy tailored to each one of the different phenotypes should be used in order to prevent or reduce the release of cytokines responsible for organ damage and disease progression.

Preparation and Biopharmaceutical Evaluation of Novel Polymeric Nanoparticles Containing Etoposide for Targeting Cancer Cells

Objectives

Polymeric nanoparticles are a promising novel drug delivery system and have advantages in cancer therapy. Etoposide is an anticancer agent that is used in the treatment of a variety of malignancies. The aim of the present study was to prepare and evaluate novel polymeric nanoparticles containing etoposide.

Materials and Methods

A 3² full factorial design was used to study the effect of Eudragit EPO and Pluronic F-68 on the characterization of nanoparticle suspensions. The polymeric nanoparticles were prepared by nanoprecipitation technique. The prepared nanoparticles was evaluated by percentage yield, drug polymer compatibility using fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetric (DSC) analysis, drug content, entrapment efficiency, zeta potential, particle size, scanning electron microscopy, X-ray diffraction, in vitro drug release studies, kinetic modeling, stability studies, and in vivo animal studies. Response surface plots were studied, which were generated using PCP dissolution software.

Results

Scanning electron microscopic studies confirmed their porous structure with a number of nanochannels. The FTIR spectra showed the stable character of etoposide in a mixture of polymers and revealed the absence of drug-polymer interactions. The DSC study revealed that the drug was involved in complexation with nanoparticles. The average particle size of etoposide nanoparticles was in the range of 114.4 nm to 136.7 nm. The zeta potential values were attained to ensure good stability of nanosuspensions. In vitro release of the drug from nanoparticles follows the Peppas model and showed controlled release behavior for a period of 24 h. The optimized nanoparticles were subjected to stability studies at 4°C in a refrigerator and the most suitable temperature for storage of etoposide nanoparticles found. The average targeting efficiency of drug-loaded nanoparticles was 41.88±0.030% of the injected dose in the liver, 25.66±0.320% in the spleen 13.82±0.090% in the lungs, 4.52±0.300% in the kidney, and 4.18±0.490% in the brain.

Conclusion

Etoposide loaded nanoparticles was found to be effective in sustained release.

Preparation and evaluation of etoposide-loaded lipid-based nanosuspensions for high-dose treatment of lymphoma

Aim: High-dose administration of etoposide (VP16) was limited by its poor aqueous solubility and severe systemic toxicity on lymphoma therapy. Herein, a novel VP16-loaded lipid-based nanosuspensions (VP16-LNS) was developed for improving drug solubility, enhancing antitumor effect and reducing systemic toxicity. Materials & methods: VP16-LNS with soya lecithin and D-α-tocopheryl PEG 1000 succinate (TPGS) as stabilizers were prepared by nanoprecipitation method. Results: VP16-LNS exhibited uniform spherical morphology, small particle size and favorable colloidal stability. The concentration of VP16 in VP16-LNS was high enough (1017.67 μg/ml) for high-dose therapy on lymphoma. Moreover, VP16-LNS displayed long blood circulation time, selective intratumoral accumulation, remarkable antitumor effect and upregulated safety. Conclusion: VP16-LNS would be an efficient nanoformulation for clinical intravenous application against lymphoma.

In vitro and in vivo evaluation of etoposide - silk wafers for neuroblastoma treatment

High-risk neuroblastoma requires surgical resection and multi-drug chemotherapy. This study aimed to develop an extended release, implantable and degradable delivery system for etoposide, commonly used for neuroblastoma treatment. Different concentrations of silk, a biodegradable, non-toxic, non-immunogenic material were employed to prepare etoposide-loaded wafer formulations. Secondary structure of silk in the formulations was characterized using Fourier Transform Infrared (FTIR) spectroscopy and optimized based on the crystalline structure. Accelerated in vitro degradation studies under different conditions such as acidic, alkaline, oxidizing mediums and high temperature, were performed. The integrity of the silk wafer structure was maintained unless exposed to 0.1 N NaOH for 24 h. In vitro release of etoposide was performed in PBS (phosphate buffered saline) at 37 °C. Silk coated 6% wafers released the drug up to 45 days, while uncoated wafers released the drug for 30 days. Cytotoxicity study was performed on KELLY cells to evaluate the etoposide cytotoxicity (LC50) and the long-term efficacy of the etoposide wafer formulations. The results showed that etoposide killed 50% of the cells at 1 μg/mL concentration and the wafer formulations demonstrated significant cytotoxicity up to 22 days when compared to untreated cells. Using an orthotopic neuroblastoma mouse model, intra-tumoral implantation of the coated 6%, uncoated 6%, or uncoated 3% silk wafers were all effective at decreasing tumor growth. Histological examination revealed tumor cell necrosis adjacent to the drug-loaded silk wafer.

Acute kidney injury after high dose etoposide phosphate: A retrospective study in children receiving an allogeneic hematopoetic stem cell transplantation

BACKGROUND

Etoposide phosphate (EP; single injection, 60 mg/kg) followed by total body irradiation (TBI) at 12 Gy has been used as an allogeneic stem cell transplantation (allo-SCT) conditioning regimen for children since 2010. In our institution, EP has been suspected of leading to acute nephrotoxicity. The aim of this study was to assess the potential renal toxicity of EP in this context.

MATERIALS AND METHODS

A retrospective study was carried out on children hospitalized between 2007 and 2015 for allo-SCT with TBI-based myeloablative conditioning associated with cyclophosphamide (CY, 60 mg/kg/day × 2 days) or EP. The primary endpoint of the study was the occurrence of acute kidney injury (AKI). Additional endpoints were time to recovery for children with AKI, survival, and treatment-related mortality.

RESULTS

Thirty-five patients were analyzed (CY: 22 vs. EP: 13). AKI occurred more frequently in the EP group than in the CY one (69% vs. 27%, adjusted odds ratio 6.0, 95% confidence interval [CI] [1.145; 31.445], P = 0.03). The median time to recovery was estimated at 3 days, 95% CI (2; 17), with CY and 11 days 95% CI (5; 18) with EP (adjusted hazard ratio of recovery for EP vs. CY 0.262, 95% CI [0.071; 0.969], P = 0.04). No significant difference was highlighted between the two treatments for survival or for treatment-related mortality.

DISCUSSION

This study shows that EP at high dosage or one of its excipients is probably responsible for AKI, as compared to CY. Further studies are required to explore the origin of this adverse effect.

Efficacy of pegylated liposomal etoposide nanoparticles on breast cancer cell lines

BACKGROUND/AIM

This study aimed to investigate the efficacy of pegylated liposomal etoposide nanoparticles (NPs) against T-47D and MCF-7 breast cancer cell lines.

MATERIALS AND METHODS

Pegylated liposomal etoposide NPs were prepared by reverse phase evaporation method. The size, size distribution, and zeta potential of the NPs was measured by a Zetasizer instrument. The cytotoxicity of NPs was inspected by methyl thiazol tetrazolium assay. The release pattern of the drug from the vesicles was studied by the dialysis method. Drug loading and encapsulation efficiency (EE) were also measured.

RESULTS

The mean size, size distribution, and zeta potential of pegylated liposomal etoposide NPs were 491 ± 15.5 nm, 0.504 ± 0.14, and -35.8 ± 2.5 mV, respectively. Drug loading and EE were 10.3 ± 1.6% and 99.1 ± 2.8%, respectively. The etoposide release in the formulation was estimated at about 3.48% after 48 h. The cytotoxicity effect of etoposide NPs on T-47D and MCF-7 cell lines of breast cancer showed higher antitumor activity as compared with those of the free drug.

CONCLUSION

Liposome-based NPs may hold great potential as a drug delivery system.

Pharmacokinetics and pharmacodynamics of dasatinib in the chronic phase of newly diagnosed chronic myeloid leukemia

PURPOSE

Dasatinib is a novel, oral, multi-targeted kinase inhibitor of breakpoint cluster region-abelson (BCR-ABL) and Src family kinases. The study investigated pharmacokinetic (PK) and pharmacodynamic (PD) analyses of dasatinib in 51 newly diagnosed, chronic phase, chronic myeloid leukemia patients.

METHODS

The dasatinib concentration required to inhibit 50 % of the CrkL (CT10 regulator of kinase like) phosphorylation in bone marrow CD34+ cells (half maximal (50 %) inhibitory concentration (IC50)CD34+cells) was calculated from each patient's dose-response curve using flow cytometry. PK parameters were obtained from the population pharmacokinetic analysis of dasatinib concentrations in plasma on day 28 after administration.

RESULTS

Early molecular responses were not significantly associated with PK or PD (IC50 CD34+cells) parameters. However, the PK/PD parameter-time above IC50 CD34+cells-significantly correlated with BCR-ABL transcript level at 3 months (correlation coefficient (CC) = -0.292, P = 0.0375) and the reduction of BCR-ABL level at 1 or 3 months (CC = -0.404, P = 0.00328 and CC = -0.356, P = 0.0104, respectively). Patients with more than 12.6 h at time above IC50 CD34+cells achieved a molecular response of 3.0 log reduction at 3 months and those more than 12.8 h achieved a deep molecular response less than 4.0 log reduction at 6 months at a significantly high rate (P = 0.013, odds ratio = 4.8 and P = 0.024, odds ratio = 4.3, respectively).

CONCLUSION

These results suggest that the anti-leukemic activity of dasatinib exhibits in a time-dependent manner and that exposure for more than 12.8 h at time above IC50 CD34+cells could significantly improve prognosis.

Etoposide-loaded immunoliposomes as active targeting agents for GD2-positive malignancies

Systemic chemotherapeutics remain the standard of care for most malignancies even though they frequently suffer from narrow therapeutic index, poor serum solubility, and off-target effects. In this study, we have encapsulated etoposide, a topoisomerase inhibitor effective against a wide range of cancers, in surface-modified liposomes decorated with anti-GD2 antibodies. We characterized the properties of the liposomes using a variety of methods including dynamic light scattering, electron microscopy, and Fourier transformed infrared spectroscopy. We examined whether these immunoliposomes were able to target cell lines expressing varying levels of surface GD2 and affect cellular proliferation. Anti-GD2 liposomes were generally targeted in a manner that correlated with GD2 expression and inhibited proliferation in cell lines to which they were efficiently targeted. The mechanism by which the immunoliposomes entered targeted cells appeared to be via clathrin-dependent uptake as demonstrated using flow cytometry and confocal microscopy. These studies suggest that anti-GD2-targeted, etoposide-loaded liposomes represent a potential strategy for more effective delivery of anti-cancer drugs that could be used for GD2 positive tumors.

Protective effects of propolis and related polyphenolic/flavonoid compounds against toxicity induced by irinotecan

Despite the excellent chemotherapeutic effect of irinotecan, its cytotoxicity and genotoxicity in normal cells remains a major problem in chemotherapy. This study was carried out to find whether propolis preparations and related flavonoids (quercetin, naringin) might enhance irinotecan-induced cytotoxicity to tumor cells in mice bearing Ehrlich ascites tumors (EAT) while protecting normal blood, liver, and kidney cells. The preparation of propolis and their flavonoids were given to mice intraperitoneally at a dose of 100 mg kg(-1) body weight for three consecutive days before the ip injection of EAT cells (2×10(6)). Irinotecan was administered ip at dose of 50 mg kg(-1) on days 3, 4, and 5 after tumor cell inoculation. The combination treatment resulted in substantial inhibition of the growth of EAT cells as well as treatment with quercetin or irinotecan alone, whereas other treatment by itself showed little effect. However, when mice were pre-treated with test components prior to irinotecan, the frequencies of irinotecan-induced micronuclei (MN) was decreased but in mice bearing tumor QU and EEP increased number of micronucleated cells. Propolis preparation and related flavonoids were found to exhibit an important immunomodulatory effect and could decrease irinotecan-induced toxic and genotoxic effects to normal cells without effecting irinotecan cytotoxicity in EAT cells.

Lifespan of etoposide-treated human neutrophils is affected by antioxidant ability of quercetin

Neutropenia is the primary dose-limiting effect of etoposide toxicity resulting in a decreased efficiency of cancer treatment. Hence, the protection of neutrophils has important clinical implications. We investigated whether quercetin, due to its antioxidant properties, is able to modulate the damaging activity of etoposide. DNA damage, evaluated by the comet assay, and apoptosis, determined by FACScan flow cytometry using Annexin/PI, increased with etoposide doses. The intracellular level of reactive oxygen species (ROS) was enhanced in resting neutrophils incubated with etoposide at concentrations up to 25 microM; above this concentration etoposide revealed antioxidant properties. Only in latex-activated neutrophils, i.e. with latex-stimulated respiratory burst was the ROS production inhibited, as assessed by the luminol amplified chemiluminescence. The characteristic electron spin resonance (ESR) signal of etoposide phenoxyl radical, which occurs in the presence of myeloperoxidase, H2O2 and etoposide, was quenched by quercetin in a dose-dependent manner (0.1-0.5 microM). Quercetin also inhibited DNA damage induced by etoposide and enhanced the inhibitory action of etoposide on the ROS formation in neutrophils. However, quercetin (1 microM) lowered early and late apoptosis/necrosis only when apoptosis was induced by 25 microM etoposide; at higher etoposide concentration apoptosis was enhanced. Summing up, antioxidant adjuvant therapy using quercetin can be beneficial in prolonging neutrophils' lifespan in peripheral blood only when etoposide plasma concentration is low.

International Society of Geriatric Oncology (SIOG) recommendations for the adjustment of dosing in elderly cancer patients with renal insufficiency

A SIOG taskforce was formed to discuss best clinical practice for elderly cancer patients with renal insufficiency. This manuscript outlines recommended dosing adjustments for cancer drugs in this population according to renal function. Dosing adjustments have been made for drugs in current use which have recommendations in renal insufficiency and the elderly, focusing on drugs which are renally eliminated or are known to be nephrotoxic. Recommendations are based on pharmacokinetic and/or pharmacodynamic data where available. The taskforce recommend that before initiating therapy, some form of geriatric assessment should be conducted that includes evaluation of comorbidities and polypharmacy, hydration status and renal function (using available formulae). Within each drug class, it is sensible to use agents which are less likely to be influenced by renal clearance. Pharmacokinetic and pharmacodynamic data of anticancer agents in the elderly are needed in order to maximise efficacy whilst avoiding unacceptable toxicity.

Camptothecin and podophyllotoxin derivatives: inhibitors of topoisomerase I and II - mechanisms of action, pharmacokinetics and toxicity profile

Camptothecins represent an established class of effective agents that selectively target topoisomerase I by trapping the catalytic intermediate of the topoisomerase I-DNA reaction, the cleavage complex. The water-soluble salt camptothecin-sodium - introduced in early trials in the 1960s - was highly toxic in animals, whereas the semisynthetic derivatives irinotecan and topotecan did not cause haemorrhagic cystitis because of their higher physicochemical stability and solubility at lower pH values. Myelosuppression, neutropenia and, to a lesser extent, thrombocytopenia are dose-limiting toxic effects of topotecan. In contrast to the structurally-related topotecan, irinotecan is a prodrug which has to be converted to SN-38, its active form. SN-38 is inactivated by conjugation, thus patients with Gilbert's syndrome and other forms of genetic glucuronidation deficiency are at an increased risk of irinotecan-induced adverse effects, such as neutropenia and diarrhoea. The cytotoxic mechanism of podophyllotoxin is the inhibition of topoisomerase II. Common adverse effects of etoposide include dose-limiting myelosuppression. Hypersensitivity reactions are more common with etoposide and teniposide than with etoposide phosphate because the formulations of the former contain sensitising solubilisers. Leukopenia and thrombocytopenia occur in 65% and 80%, respectively, of patients after administration of conventional doses of teniposide. Anorexia, vomiting and diarrhoea are generally of mild severity after administration of conventional doses of topoisomerase II inhibitors. Clinical pharmacokinetic studies have revealed substantial interindividual variabilities regarding the area under the concentration-time curve values and steady-state concentrations for all drugs reviewed in this article. Irinotecan, etoposide and teniposide are degraded via complex metabolic pathways. In contrast, topotecan primarily undergoes renal excretion. Regarding etoposide and teniposide, the extent of catechol formation over time during drug metabolism may be associated with a higher risk for secondary malignancies.

Pharmacokinetic studies in children with cancer

We reviewed the current status of our knowledge of pharmacokinetics and pharmacodynamics of some anti-neoplastic drugs, used in the treatment of childhood cancer. Extrapolation of data from pharmacokinetic studies in adults to the paediatric population is often not feasible. Specific studies in children are needed. Of all reviewed anti-neoplastic drugs methotrexate appears to be most extensively studied. Methotrexate pharmacokinetics is correlated with toxicity and response to therapy, and it has been shown that individualized adaptive dosing of methotrexate is correlated with a better response to therapy without increasing toxicity in children with ALL and osteosarcoma. Of most of the other reviewed anti-neoplastic drugs it is demonstrated that pharmacokinetics is correlated with toxicity, and of some drugs a relationship of pharmacokinetics with response to therapy is demonstrated as well. In case of cytarabine, etoposide, and teniposide, individualized dosing also appears to be feasible. However, there is no evidence that this strategy improves response to therapy. Specifically data on pharmacokinetic and pharmacodynamic correlations and effect of pharmacokinetically guided, individualized dosing are important for the design of optimal cancer chemotherapy for individual patients. Unfortunately for a considerable number of anti-neoplastic drugs these specific data are lacking in children and future research is needed.

Too Old to Care?

Shortly before his death in 1995, Kenneth B. Schwartz, a cancer patient at Massachusetts General Hospital (MGH), founded The Kenneth B. Schwartz Center at MGH (http://www.theschwarzcenter.org/rounds.asp). The Schwartz Center is a nonprofit organization dedicated to supporting and advancing compassionate health care delivery, which provides hope to the patient and support to caregivers, and encourages the healing process. The center sponsors the Schwartz Center Rounds, a monthly multidisciplinary forum where caregivers reflect on important psychosocial issues faced by patients, their families, and their caregivers, and gain insight and support from fellow staff members. Ageism is a pervasive problem throughout society. It is rooted in language, attitudes, beliefs, behaviors, and policies. Aging profoundly influences physiology, challenging the medical community to accommodate but not discriminate. The elderly are at an increased risk of disease and disability. Sixty percent of cancer occurs in people aged 65 and older, and the population is aging. The treatment of cancer in the elderly is complicated by comorbidities and other physiological factors, particularly renal, bone marrow, and metabolic reserve. Caregivers have to treat patients in a manner that optimizes treatment and avoids anticipated harm. However, the caregiver is often faced with situations where they must balance their personal beliefs, professional values, and knowledge of medicine with their patients' preferences and needs. Discussion in the Rounds focused on age bias, drug toxicity, life prolongation, and symptom relief, with the role of the caregiver, and the relationship to the patient, being pivotal.

Pharmacokinetics and pharmacodynamics of imatinib in a phase I trial with chronic myeloid leukemia patients

PURPOSE

To evaluate the basic pharmacokinetic (PK) characteristics of imatinib mesylate and assess the relationship between the PK and pharmacodynamic (PD) properties of the drug.

PATIENTS AND METHODS

The PK and PD properties of imatinib were investigated during a phase I trial that included 64 adult patients with Philadelphia chromosome-positive leukemias. Patients received imatinib orally once or twice daily. PK parameters of imatinib, derived from the plasma concentration-time curves, were determined. PD response, defined as the WBC after 1 month of treatment with imatinib, was used to develop an efficacy model. A maximum inhibition-effect model was used to describe the relationship between reduction in WBC and drug exposure parameters.

RESULTS

Imatinib exposure was dose proportional after oral administration for the dose range of 25 to 1,000 mg. There was a 1.5- to three-fold drug accumulation after repeated once-daily dosing. Mean plasma trough concentration was 0.57 microg/mL (approximately 1 micromol/L) 24 hours after administration of 350 mg of imatinib at steady-state, which exceeds the 50% inhibitory concentration required to inhibit proliferation of Bcr-Abl-positive leukemic cells. Analysis of PK/PD relationships indicates that the initial hematologic response depends on the administered dose for patients with chronic myeloid leukemia.

CONCLUSION

Drug exposure (area under the concentration-time curve) is dose proportional for the dose range of 25 to 1,000 mg, and there is a 1.5- to three-fold drug accumulation at steady-state after once-daily dosing. Analysis of the relationship between PD (WBC reduction) and PK parameters at steady-state indicates that a dose of 400 mg or greater is required for maximal PD effect.

Pharmacology of anticancer drugs in the elderly population

Modifications to bodily functions and physiology are known to occur with age. These changes can have a considerable impact on the pharmacokinetic processes of absorption, distribution, metabolism and excretion and the pharmacodynamic properties of administered drugs. For many drugs with a high therapeutic index, this will be clinically unimportant, but for anticancer drugs, which usually have a low therapeutic index, these pharmacological changes can lead to dramatic consequences, such as excessive drug concentrations and unacceptable toxicity, or subtherapeutic drug concentrations and ineffective treatment. Despite the increased susceptibility of the elderly to these changes, doses are rarely adapted on the basis of pharmacokinetics and pharmacodynamics, with the exception of changes secondary to altered renal function. Until recently, only a few large prospective randomised trials have provided evidence-based data for dose adaptations in elderly patients. However, with increasing knowledge of the pharmacokinetics of anticancer drugs, advances in the knowledge of pharmacokinetic behaviour with aging, and documented efficacy and toxicity data in the elderly population, it is possible to highlight aspects of prescribing anticancer drugs in the elderly. In general, and for most drugs, age itself is not a contraindication to full-dose chemotherapy. The main limiting factors are comorbidity and poor functional status, which may be present in a significant number of the elderly population. Elderly patients with cancer are part of the daily practice of oncologists, but currently clinicians can often only estimate whether dose modification is advantageous for the elderly. This review attempts to elucidate the factors that can influence the pharmacokinetics of anticancer drugs frequently used in the elderly, and the clinical or biochemical parameters that form the basis for dose adjustments with age.

Phase I escalation of gemcitabine combined with protracted oral etoposide in gynecologic malignancies: A Gynecologic Oncology Group study

OBJECTIVE

Although improvements have been made in the management of patients with advanced ovarian cancer, long-term survivors are still uncommon. Gemcitabine and prolonged oral etoposide have shown reproducible single-agent activity in patients with platinum/paclitaxel-resistant ovarian cancer. This, combined with preclinical synergism, prompted the Gynecologic Oncology Group to determine the maximum tolerated dose (MTD) of this combination.

METHODS

Eligible patients had recurrent epithelial ovarian cancer, primary papillary peritoneal, or fallopian tube carcinoma. All had received prior platinum/paclitaxel-based chemotherapy and had adequate hepatic, renal and bone marrow function. Oral etoposide was administered at 50 mg/m2 for ten days, with three proposed dose levels for gemcitabine on days 1 and 8: 400, 550 and 700 mg/m2. Cycles were to be repeated every 28 days. Three patients were to enter at each dose level.

RESULTS

Patients were enrolled only to dose level 1 as this dose exceeded MTD. Of six patients initially enrolled, one was removed after three days with fever, ascites and decreased albumin believed not to be treatment related. Five patients were evaluable for toxicity and response. One of the first three patients developed dose limiting toxicity (DLT) manifested as grade 4 neutropenia. A second DLT (neutropenic fever and thrombocytopenia associated with bleeding) occurred among the next three patients: therefore, MTD was reached at dose level 1. Grade 4 toxicities included episodes of neutropenia (4) and thrombocytopenia (3). No objective response was observed.

CONCLUSIONS

Oral etoposide and gemcitabine at this dose and schedule was associated with substantial toxicity in this population. Patients who are previously treated with platinum/paclitaxel-based chemotherapy may be at particular risk for toxicity.

Optimizing drug regimens in cancer chemotherapy by an efficacy-toxicity mathematical model

In cancer chemotherapy, it is important to design treatment strategies that ensure a desired rate of tumor cell kill without unacceptable toxicity. To optimize treatment, we used a mathematical model describing the pharmacokinetics of anticancer drugs, antitumor efficacy, and drug toxicity. This model was associated with constraints on the allowed plasma concentrations, drug exposure, and leukopenia. Given a schedule of drug administrations, the mathematical model optimized the drug doses that can minimize the tumor burden while limiting toxicity at the level of the white blood cells. The main result is that the optimal drug administration is an initial high-dose chemotherapy up to saturation of constraints associated with normal cell toxicity and a maintenance continuous infusion at a moderate rate. Data related to etoposide investigations were used in a feasibility study. Simulations with the optimized protocol showed better performances than usual clinical protocols. Model-based optimal drug doses provide for greater cytoreduction, while limiting the risk of unacceptable toxicity.

Adaptive control methods for the dose individualisation of anticancer agents

Numerous studies have found a clear relationship between systemic exposure and the toxicity or (more rarely) the efficacy of anticancer agents. Moreover, the clearance of most of these drugs differs widely between patients. These findings, combined with the narrow therapeutic index of anticancer drugs, suggest that patient outcome would be improved if doses were individualised to achieve a target systemic exposure. Bayesian maximum a posteriori probability (MAP) forecasting is an efficient and robust method for the optimisation of drug therapy, but its use for anticancer drugs is not yet extensive. The aim of this paper is to review the application of population pharmacokinetics and MAP to anticancer drugs and to evaluate whether and when MAP Bayesian estimation improves the clinical benefit of anticancer chemotherapy. For each drug, the relationships between pharmacokinetic variables [e.g. plasma concentration or the area under the concentration-time curve] and pharmacodynamic effects are described. Secondly, the methodologies employed are considered and, finally, the results are analysed in terms of predictive performance as well as, where possible, the impact on clinical end-points. Some studies were retrospective and intended only to evaluate individual pharmacokinetic parameter values using very few blood samples. Among the prospective trials, a few studied the pharmacokinetic/pharmacodynamic relationships which provided the basis for routine pharmacokinetic monitoring. Others were performed in clinical context where MAP Bayesian estimation was used to determine maximum tolerated systemic exposure (e.g. for carboplatin, topotecan, teniposide) or for pharmacokinetic monitoring (e.g. for methotrexate or platinum compounds). Indeed, its flexibility in blood sampling times makes this technique much more applicable than other limited sampling strategies. These examples demonstrate that individual dose adjustment helps manage toxicity. The performance of pharmacokinetic monitoring is linked to the methodology used at each step of its design and application. Moreover, a limitation to the use of pharmacokinetic monitoring for certain anticancer drugs has been the difficulty in obtaining pharmacokinetic or pharmacodynamic data. Recent progress in analytical methods, as well as the development of noninvasive methods (such as positron emission tomography) for evaluating the effects of chemotherapy, will help to define pharmacokinetic-pharmacodynamic relationships. Bayesian estimation is the strategy of choice for performing pharmacokinetic studies, as well as ensuring that a given patient benefits from the desired systemic exposure. Together, these methods could contribute to improving cancer chemotherapy in terms of patient outcome and survival.

Etoposide in prostate cancer

Hormone refractory prostate cancer is a disease that kills approximately 39,000 people per year. No single chemotherapeutic agent or regimen has been demonstrated to provide a survival advantage in this disease. Etoposide as a single agent, both in i.v. and oral formulations has not proven to be effective. In the 1990s, however, etoposide has been combined with several agents to create novel treatment regiments for patients with hormone refractory disease. Several of these regimens, all involving oral etoposide, have demonstrated promising results in Phase II trials and early results suggest that they may increase survival for hormone refractory patients, although this remains to be tested in a Phase III trial setting.

Topoisomerase II-mediated alterations of K562 drug resistant sublines

In order to further elucidate the roles of DNA topoisomerase II (topo II) subtypes, alpha and beta, as drug targets in chemotherapy, we have determined the enzyme levels in K562 cells selected for resistance to mitoxantrone (K562/Mxn), daunorubicin (K562/Dnr) and idarubicin (K562/Ida 20 and K562/Ida 60), as well as topo II-DNA complex formation, DNA damage and cytotoxicity, induced by topo II interactive agents, for example etoposide, teniposide, mitoxantrone and amsacrine. As compared to the parental cells, topo IIalpha/beta protein levels in K562/Mxn, K562/Dnr, K562/Ida 20 and 60 lines, measured with Western blot, were 17/67%, 85/88, 24/31% and 10/7% respectively. DNA damage, determined by DNA unwinding technique, induced by teniposide and amsacrine correlated with both topo IIalpha/beta protein levels (r2 = 0.8/0.9, P = 0.03/0.01 and r2 = 0.8/0.9, P = 0.04/0.01, respectively). Topo II-DNA complex formation induced by all studied drugs correlated with topo IIbeta protein levels (r2-range 0.8-0.9, P-range 0.01-0.04), while the correlation with topo IIalpha was weaker. Topo IIalpha/beta protein levels tended to show an inverse correlation with the cytotoxicity of etoposide (r2 = -0.9/-0.7, P = 0.01/0.06). The overall topo II-DNA complex formation correlated with drug-induced DNA damage (r2 = 0.9, P = 0.0001), whilst not with the cytotoxicity. Our findings indicate that both topo II isozymes are the targets of the antitumor agents studied, and of potential clinical relevance for prediction of treatment efficacy. They could play a role in tailored chemotherapy.

A general model for time-dissociated pharmacokinetic-pharmacodynamic relationship exemplified by paclitaxel myelosuppression

BACKGROUND

Hematologic toxicity after cancer chemotherapy and other drug effects that occur late compared to the exposure are usually modeled with use of some summary exposure variable such as the area under the concentration-time curve (AUC model) or the time of exposure above a threshold concentration (threshold model). An underlying assumption for both of these models is that the drug exerts a direct effect while present in the body and that it is the time integral of this direct effect that is related to the ultimate observed effect, either linearly (AUC model) or by a step function (threshold model). We propose a more general model that allows this relationship to be characterized by a nonlinear continuous function.

METHODS

Data on survival fraction of neutrophiles and time course of leukopenia from 92 courses of paclitaxel therapy in 21 patients with breast or ovarian cancer was related to paclitaxel concentration-time profiles with the AUC, threshold, and general models. The properties of the general model were also investigated with use of simulations.

RESULTS

For both pharmacodynamic end points, the general model described the data significantly better than the AUC or threshold models.

CONCLUSION

The general model is an extension to the present way of relating concentration-time profiles to late-effect measures, and it may provide an improved description of the concentration-response relationship and more accurate predictions of the ultimate effect when doses and schedules are varied. It can explain complex relationships between concentration-time profiles and the observed effect, and predictions from it lack some of the counterintuitive properties that the AUC or threshold model have when extrapolations are made.

Therapeutic drug monitoring opportunities in cancer therapy

Cancer is a common cause of death, and improvements in treatment are desperately needed. The high degree of variation in systemic exposure for a given dose and the relationships between blood concentrations and either toxic or antitumor effects would suggest that therapeutic drug monitoring is a potential mechanism for improving the treatment of individual patients. In this review, the case for therapeutic drug monitoring is made in a select number of commonly used cancer drugs and areas that require more concerted effort are highlighted.

Drug administration in patients with renal insufficiency. Minimising renal and extrarenal toxicity

Renal insufficiency has been associated with an increased risk of adverse effects with many classes of medications. The risk of some, but not all, adverse effects has been linked to the patient's degree of residual renal function. This may be the result of inappropriate individualisation of those agents that are primarily eliminated by the kidney, or an alteration in the pharmacodynamic response as a result of renal insufficiency. The pathophysiological mechanism responsible for alterations in drug disposition, especially metabolism and renal excretion, is the accumulation of uraemic toxins that may modulate cytochrome P450 enzyme activity and decrease glomerular filtration as well as tubular secretion. The general principles to enhance the safety of drug therapy in patients with renal insufficiency include knowledge of the potential toxicities and interactions of the therapeutic agent, consideration of possible alternatives therapies and individualisation of drug therapy based on patient level of renal function. Although optimisation of the desired therapeutic outcomes are of paramount importance, additional pharmacotherapeutic issues for patients with reduced renal function are the prevention or minimisation of future acute or chronic nephrotoxic insults, as well as the severity and occurrence of adverse effects on other organ systems. Risk factors for the development of nephrotoxicity for selected high-risk therapies (e.g. aminoglycosides, nonsteroidal anti-inflammatory drugs, ACE inhibitors and radiographic contrast media) are quite similar and include pre-existing renal insufficiency, concomitant administration of other nephrotoxins, volume depletion and concomitant hepatic disease or congestive heart failure. Investigations of prophylactic approaches to enhance the safety of these agents in patients with renal insufficiency have yielded inconsistent outcomes. Hydration with saline prior to drug exposure has given the most consistent benefit, while sodium loading and use of pharmacological interventions [e.g. furosemide (frusemide) dopomine/dobutamine, calcium antagonists and mannitol] have resulted in limited success. The mechanisms responsible for altered dynamic responses of some agents (benzodiazepines, theophylline, digoxin and loop diuretics) in renally compromised patients include enhanced receptor sensitivity secondary to the accumulation of endogenous uraemic toxins and competition for secretion to the renal tubular site of action. Application of the pharmacotherapeutic principles discussed into clinical practice will hopefully enhance the safety of these agents and optimise patient outcomes.

Evaluation of a prediction model of cisplatin dose based on total platinum plasma concentration

The aim of this study was to validate prospectively a model of cisplatin dose adjustment. 27 patients (63 courses) with lung cancer were treated by a 5 day continuous infusion of cisplatin and etoposide. The dose of cisplatin was adjusted in order to reach a target plasma concentration of total platinum (TP) of 2000 mu/l at the end of the infusion. The target concentration was reached with a mean bias of 2.7% and a precision of 7.8%. The results were compared with those of a population of 38 patients (97 courses) with lung cancer and treated with the same protocol of chemotherapy, but without dose adjustment. The average dose adjustment was an increase of cisplatin dose of 20.2%. This augmentation was most important during the first course, decreasing during the following courses. There was also an increase in the etoposide AUC, although its dose was not modified. Toxicity to polymorphonuclear cells was significantly increased and was linked to etoposide AUC.

Etoposide combined with interferon alfa-2b: novel exploitation of established etoposide pharmacokinetics and pharmacodynamics

PURPOSE

To construct an efficient pilot study design to determine whether interferon alfa-2b modifies the pharmacokinetics and pharmacodynamics of continuous-infusion etoposide.

PATIENTS AND METHODS

A two-stage randomized 2 X 2 factorial design was used to evaluate interferon alfa-2b at two doses (2 or 10 MU/m2/day SQ for 3 days) and two schedules (interferon alfa-2b administered before or concurrent with 72-hour continuous-infusion etoposide). Etoposide was administered at 75, 100, or 125 mg/m2/day. In lieu of comparing the experimental arms to an etoposide-alone control arm to determine effect of interferon alfa-2b dose and schedule, a novel analytic approach was used. The effect of interferon alfa-2b on etoposide-induced leukopenia was assessed indirectly by comparison of the observed white blood cell (WBC) nadir to the nadir predicted from an established pharmacodynamic model for single agent etoposide.

RESULTS

Based on 29 patients, dose-normalized 24-hour total and estimated free etoposide concentrations did not differ with interferon alfa-2b dose or schedule. Patients treated with interferon alfa-2b before etoposide had, on average a WBC nadir 545 +/- 225 cells microliter lower than that predicted by a pharmacodynamic model for etoposide alone. An optimal nonlinear model for leukopenia was defined by interferon alfa-2b schedule in addition to 24-hour etoposide concentration.

CONCLUSION

A novel study design and statistical analysis provided an efficient preliminary evaluation of the combination of interferon alfa-2b with etoposide in a modest number of patients. Exploitation of a previously validated pharmacodynamic model allowed evaluation of interferon alfa-2b effect and eliminated the need for an etoposide-alone control arm. The pharmacokinetics of continuous-infusion etoposide at doses from 75 to 125 mg/m2/day appear to be unchanged by interferon alfa-2b at the doses and schedules tested and the combination appears to be feasible. We hypothesize that leukopenia may be enhanced when interferon alfa-2b is administered before etoposide, especially at a higher dose of interferon alfa-2b.

DNA synthesis and topoisomerase inhibitors increase transduction by adeno-associated virus vectors

Viral vectors based on adeno-associated virus (AAV) preferentially transduce cells in S phase of the cell cycle. We recently found that DNA-damaging agents increased the transduction of nondividing cells. However, the optimal concentrations were toxic to cells. Here we show that the transduction of normal human fibroblasts by AAV vectors is increased by prior exposure to DNA synthesis inhibitors, such as aphidicolin or hydroxyurea, and topoisomerase inhibitors, such as etoposide or camptothecin. Transduction efficiencies could be increased > 300-fold in stationary cultures at concentrations that did not affect cell viability or proliferative potential. Both S-phase and non-S-phase cells were affected, suggesting that cellular functions other than replicative DNA synthesis may be involved. Applying these methods to gene transfer protocols should improve prospects for gene therapy by AAV vectors.