Current Topics in Medicinal Chemistry - Volume 12, Issue 15, 2012

Drug delivery systems for gene transfer are called ‘vectors’. These systems were originally invented as a delivery system for the transfection in vitro or in vivo. Several vectors are then developed for clinical use of gene medicines and currently some of them are approved as animal drugs. Conventional drug delivery system generally consists of approved (existing) materials to avoid additional pre-clinical or clinical studies. However, current vectors contain novel materials to improve an efficacy of gene medicines. Thus, these vectors have functions more than a mere delivery of active ingredients. For example some vectors have immunological functions such as adjuvants in vaccines. These new types of vectors are called ‘intelligent’ or ‘innovative’ vector system', since the concept or strategy for the development is completely different from conventional drug delivery systems. In this article, we described a current status of ‘intelligent gene transfer vectors and discussed on the potentials of them.

The decoy oligodeoxynucleotide (ODN) serves as a decoy sequence for a target transcription factor, then inhibiting its binding to the authentic sequence at the promoter, and consequently hinders the gene expression. ODNs should be properly up taken by the cell and tissue, be specific for one nuclear factor, and be stable against intracellular and serum nucleases. Since phosphodiester oligos are easily degradated by nucleases, chemical modification such as phosphorothioation, and structural modification by ligation of the extremities of two single-strand phosphodiester sequence resulting in a dumbbell shaped ODN (Ribbon-type decoy ODN) are performed to increase the stability of ODNs. In combination, phosphorothioation of specific regions in Ribbon-type decoy has further increased its stability, and the introduction of saturated hydrocarbon polymer spacer linking the two double strands also improved the stability and reduced the production cost. The cellular delivery has been optimized by using the biodegradable polymer D,L-lactide-co-glycolide (PLGA) as a carrier to ODN. The nuclear factor-kappa B (NF-κB) is a convergent point of different pathways, with main role in many pathologies, and poses as an ideal target for decoy ODN strategy. Following this we have designed ODN targeting NF-κB, and in this review, we are going to discuss the various modification performed in an attempt to improve the ODN efficacy, and some promising pre-clinical data and clinical trials using NF-κB decoy ODN.

Although organ transplantations have been broadly performed in humans, occurrence of rejection has not yet been resolved. Several inflammatory factors, such as cytokines and adhesion molecules, enhance the rejection. Specific treatments that target in the attenuation of rejection have not been well studied in organ transplantation. Recent progress in the nucleic acid drugs, such as antisense oligodeoxynucleotides (ODNs) to regulate the transcription of disease-related genes, are known to play critical roles in therapeutic applications. Transfection of cis-element double-stranded DNA, named as "decoy", has been also reported to be a useful nucleic acid drug. This strategy has been not only a useful method for the experimental studies of gene regulation but also a novel clinical strategy. In this article, we reviewed the experimental results of nucleic acid drugs using the experimental organ transplant models.

Recent progress in molecular and cellular biology has resulted in the development of numerous effective drugs. However, there are still a number of diseases for which no known effective therapy exists, such as ischemic heart disease, vascular bypass graft failure and heart failure. Despite its limitations, oligodeoxynucleotide (ODN)-based therapy is emerging as a potential strategy for the treatment of patients with cardiovascular disease that is resistant to current therapeutic approaches. Indeed, several nucleic acid drugs and delivery methods for heart disease have been developed and their efficacy has been investigated in animal models. Among them, some agents have undergone clinical trials, such as cmyc antisense ODN, E2F and NFκB decoy ODN. However, none of the large randomized placebo-controlled trials has shown conclusive evidence of clinical benefit. Recent experimental studies suggested that siRNA- and miRNA-based strategies have potential as a potent therapeutic approach for the treatment of restenosis. In addition, simultaneous regulation of multiple intracellular signaling pathways is expected to enhance the therapeutic effects. This review focuses on the potential of recent ODN-based gene therapy for the treatment of heart disease, especially restenosis after revascularization.

Novel therapeutic strategies using nucleic acid drugs, such as plasmid DNA (pDNA) and nuclear factor-κB (NFκB) decoy, have been sought for non-treatable neurological disorders. Among them, the application of pDNA has been extensively studied in diabetic neuropathy. Since growth factors, such as vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF), have both neurotrophic and angiogenic properties, intramuscular injection of pDNA encoding these genes has been examined and shown to be effective for treatment in experimental animals and also in clinical trials. These growth factors have also been shown to accelerate neuroprotection, angiogenesis, and regeneration in the brain, and overexpression of these factors showed therapeutic effects in cerebral ischemia in rodents. Inhibition of inflammation is another strategy to treat cerebrovascular diseases. Recent studies suggest that NFκB plays critical roles in the formation of cerebral aneurysms, and inhibition of its function by NFκB decoy was shown to prevent cerebral aneurysm enlargement through inhibition of NFκB-mediated inflammation. In the field of neurodegenerative disease, the potential of pDNA as a tool for vaccination has attracted researchers since pDNA itself has shown adjuvant properties and the potential to induce immunity or immune tolerance. pDNA encoding disease antigens, such as amyloid-Aβ in Alzheimer disease or myelin basic protein in multiple sclerosis (MS), was shown to have therapeutic effects in rodents, and its efficacy and safety were reported in a phase I/II clinical study in MS. In this review, we discuss the potential and problems of nucleic acid drugs in neurological disorders.

Gene therapy offers a novel approach for the prevention and treatment of a variety of diseases, but it is not yet a common method in clinical cases because of various problems. Viral vectors show high efficiency of gene transfer, but they have some problems with toxicity and immunity. On the other hand, plasmid deoxyribonucleic acid (DNA)-based gene transfer is very safe, but its efficiency is relatively low. Especially, plasmid DNA gene therapy is used for cardiovascular disease because plasmid DNA transfer is possible for cardiac or skeletal muscle. Clinical angiogenic gene therapy using plasmid DNA gene transfer has been attempted in patients with peripheral artery disease, but a phase III clinical trial did not show sufficient efficiency. In this situation, more efficient plasmid DNA gene transfer is needed all over the world. This review focuses on plasmid DNA gene transfer and its enhancement, including ultrasound with microbubbles, electroporation, hydrodynamic method, gene gun, jet injection, cationic lipids and cationic polymers.

In medical oncology, targeted therapy has emerged over the last decade, as the most promising strategy to fight cancer. In addition, a more complete understanding of tumor heterogeneity and pharmacology of the more conventional anti-cancer agents has led to development of metronomic chemotherapy (MC) (i.e. a more frequent administration of anticancer agents at lower doses then the usual maximally tolerated dose because it has been realized that time of exposure to an effective drug concentration is more important than simply the dose/m2 or kg.), Here, we discuss the nature of the specificity of targeted anti-cancer treatments and conclude that optimizing the schedule is an effective way to improve treatment selectivity.

Targeted therapies have dramatically modified treatment strategies in oncology since the early 2000's, especially for treating digestive cancers. These new biotherapies such as anti-VEGF (bevacizumab) or anti-EGFR (cetuximab) monoclonal antibodies have given oncologists new opportunities to use innovative treatment schedules or combinations with cytotoxics. Consequently, significant improvements in response rates, with trends to longer progression-free survival and/or overall survival have been achieved in patients with metastatic colorectal cancer (mCRC). Panitumumab is a novel, 100% human, anti-EGFR1 (HER1) antibody that has been approved in late 2007 for use as monotherapy in mCRC patients resistant to standard chemotherapy, provided that their tumor express EGFR and display wild-type K-Ras status. Panitumumab has been recently further approved in combination with chemotherapy in mCRC patients. However, owing to the fact that its mechanism of action for targeting EGFR is similar to that of chimeric cetuximab, picturing the specificities in pharmacological and pharmacokinetic properties of this 100% human antibody could help the oncologists to better define their strategies at the bedside.

Conventional chemotherapeutic regimens have limited impact against most solid tumors and deal with significant toxicity. During the last years novel anticancer treatments targeting specific molecules or genes involved in cancer development are being developed to improve outcome and reduce side-effects. In particular several tyrosine-kinase inhibitors (TKIs, gefitinib, erlotinib, sorafenib and sunitinib) have been approved for the treatment of different solid tumors. Their clinical activity has been related to different clinical and biological parameters, such as the EGFR-activating mutations for gefitinib and erlotinib. However, not all clinical outcomes, including tolerability, are explained, and the identification/ validation of novel biomarkers is a viable area of research. Germline polymorphisms can be easily assessed in blood samples, and polymorphisms in EGFR, AKT1 and ABCG2 have been correlated with outcome and toxicity in lung cancer patients given EGFR-TKIs therapies. However, there are several controversial findings, influenced by differences in study design/analysis, while the prognostic/predictive role of these polymorphisms still needs to be evaluated within prospective studies. More studies on the relationship of the genotype with drug pharmacokinetics and mechanism of action are also warranted. All these studies, as well as further development and application of novel technologies to decipher genetic alterations, might contribute to the validation of selected polymorphisms as molecular markers predictive of drug activity and help in the selection of TKIs best suited to the individual patient.

The primary goal of phase I studies in oncology is to determine the MTD (Maximum Tolerated Dose) for a drug. This MTD is determined with respect to an accepted risk (usually 33%) to see a limiting toxity for patients. In this paper we propose a new mathematical model to determine the MTD. An important feature of this model is that the limiting toxicity can be formulated as a combination of several basic graded toxicities such as hematologic or neurological. Another feature is the possibility to take into account several patient covariates to individualize the determination of the MTD. The model is a bayesian model where some prior information has been considered. The model is expected to work better than traditional empirical schemes for determining the MTD because it uses at every step all the available information on patients, and adds some major improvements as compared with existing CRM strategies because it uses whole data made available, including low-grades toxicities. Finally the model has been validated with a retrospective data set on 17 patients from a phase I study on paclitaxel in pediatric oncology. Calculated MTDs for each patient were found to be markedly different than the doses actually given following a traditionnal dose-escalation methodology. Results suggest that our new model provides a better and safer way to drive dose-escalation in phase-I trials as compared with traditionnal schemes.

Combining several cytotoxics is the current mainstay for treating breast cancer patients. The combination between capecitabine and docetaxel was found to be more efficient than capecitabine or docetaxel when both were used as single agents. However, the administration protocol for this combination has been empirically chosen from single-agent trials. Based on already available population analysis, we propose here to optimize the administration protocol of this association so as to enhance efficacy while limiting treatment-related toxicity. Efficacy parameters evaluated from population analysis using a disturbed tumor growth model and safety characteristics from the available databases evidenced that: 1) Docetaxel is more efficient than capecitabine at the start of the treatment, but becomes less efficient next because of acquisition of resistance; 2) Over a long period of time, capecitabine is better tolerated than docetaxel. These characteristics allowed the following recommendations for an optimized modality of combination: 1) The treatment has to be started at the maximum tolerated dose for docetaxel; this dose should be individualized right from the start of the second cycle of treatment; 2) In parallel, capecitabine has to be started at a dose lower than its maximum tolerated dose. 3) When docetaxel becomes less efficient than capecitabine because of resistance, docetaxel dose has to be reduced but not discontinued. 4) If adverse events show during the treatment, it is recommended to reduce docetaxel, rather than capecitabine dosage. Combining modeling and statistical analysis of clinical data permit to optimize combination treatments. This procedure could be extended to others treatments involving combination of several cytotoxics.

Several findings suggest that patient outcome would be improved with individualized doses. The aim of this paper is to describe major approaches, methods and underlying basic foundations implemented, in clinical practice, for dosage individualization. Also we propose a new method codified by kinetic nomograms as reliable alternative to traditional Bayesian methods. Clinical and simulation data were reported to evaluate performances of the proposed methods. Real examples of therapeutic drug monitoring were selected. Bayesian methods were used to individualize high-dose methotrexate rate infusion and amikacin dosage regimen, and kinetic nomograms to adjust sirolimus doses. 1) Using only few measurements, Bayesian method resulted in accurate estimates of individual pharmacokinetic parameters of highdose methotrexate infusion. Targeting a pre-defined end-of-infusion level, infusion rate was individualized according to the previously obtained pharmacokinetic parameters. 2) With the same reasoning, individual pharmacokinetic parameters of amikacin were obtained by Bayesian estimation using three individual samples. Subsequent dosage adjustment allowed achievement of therapeutic goals at steady state. 3) Without computing individual pharmacokinetic parameters, nor using pharmacokinetic software, kinetic nomograms steered individual sirolimus blood levels within its therapeutic window with only two samples and in the first week after starting treatment. This contribution relates traditional Bayesian methods developed in 80's but not yet fully integrated in clinical context because of their complexity. The contribution focuses on recent developments based on population approaches, rendering the dosage adjustment methodology a simple and quick bedside application.

Target therapies and notably monoclonal antibodies are currently being considered for esophageal, gastric, and gastroesophageal junction cancers. EGFR was found to be overexpressed in 60-86% of gastric or gastroesophageal tumors and in 50-70% of esophageal cancers. Cetuximab was shown to be a radiosensitizing agent in the treatment of ENT neoplasia. These results led to several phase II encouraging therapeutic trials evaluating the combination of cetuximab with radiochemotherapy in locally advanced esophageal cancers. Numerous encouraging phase II trials evaluating cetuximab combined with chemotherapy in patients with gastric adenocarcinoma or gastroesophageal junction cancer were reported. These promising results are still to be confirmed by the ongoing phase III trials. Several studies reported HER2 overexpression in gastric cancer (7-34%), which appeared to be associated with poorer prognosis. Trastuzumab is a monoclonal antibody directed against the extracellular HER2 domain. The international phase III trial known as ToGA (Trastuzumab for Gastric Cancer) aimed to determine the clinical efficacy and acceptable toxicity profile of trastuzumab in combination with first-line chemotherapy in HER2-overexpressing gastric or gastroesophageal cancer. Angiogenesis is an essential step in the initial phase of tumorigenesis, and it is normally absent from healthy tissues except for particular physiological situations, such as wound healing. VEGF-A plays a role in endothelial growth and angiogenesis. Bevacizumab, a humanized monoclonal anti-VEGF-A antibody, is currently being studied for gastric cancer. The phase III AVAGAST study, evaluating bevacizumab in association with chemotherapy in advanced gastric adenocarcinoma, did not achieve its primary aim of improved OS in bevacizumab-treated patients.

Background: Dysembryoplastic Neuroepithelial Tumours (DNT) are benign brain lesions arising during childhood that are characterized by early onset partial seizures, no neurological deficit and cortical location. Pathological diagnosis is easy when the glioneuronal element is present. Its absence might lead to the diagnosis of non-specific DNT or low-grade glioma (LGG). Objective: The aim of this retrospective study was to analyse clinicopathological and molecular features of a series of cortical tumours, in order to find diagnostic and prognostic markers to better custom treatment next. Methods: Twenty four children with cortical neuroepithelial tumour were included. Clinical and radiological data were collected. Histological diagnosis was reviewed for all patients. 1p19q and p53 status were obtained by FISH and immunohistochemistry respectively. IDH1-2 gene mutations were assessed by DNA sequencing. CGH-array was performed in 6/24 samples. Results: We recorded 13 DNT and 11 cortical LGG. Median age at surgery was 11.5 years. Overall survival was 100% and event-free survival at 10 years was 70%. No tumour displayed chromosomal alteration or 1p19q deletion or p53 expression. Only one patient with grade-II oligoastrocytoma had an IDH1 mutation. No statistical difference was found between the two populations in terms of age, sex, tumour location, type of surgical resection, disease progression and clinical status at last follow-up. Only the occurrence of septations on preoperative MRI was significantly associated with pathological features of DNT. Conclusion: Patients with DNT and cortical LGG share excellent outcome. Our genetic analysis could not distinguish DNT from LGG. In particular, CGH-array analysis was strictly normal in both tumor types. In attempt to find molecular markers, diagnosis of these lesions remains difficult when the glioneuronal element is lacking.

For many years, nanocarriers have been investigated to modify pharmacokinetics and biodistribution of various active molecules. In the cancer domain, one of the biggest challenges still remains the improvement of the therapeutic index, often too low, for the majority of antitumor drugs. The application of nanotechnologies for the treatment and the diagnosis of cancers are nowadays currently developed, or under development, and liposomes play an important role in the history of nanodevices. Because of their high degree of biocompatibility, lipid nanosystems have been used to improve pharmacological profiles of various anticancer drugs otherwise discarded because of their low water solubility, poor bioavailability or either fragile and subjected to rapid biotransformations. This review aims at introducing an overview of the last 40 years of liposome researches until the last liposomal formulations commercially available or undergoing clinical trials. Liposome properties will be described, with a particular emphasis over the last generation of carriers appreciated for their active targeting characteristics. Researchers foresee a remarkable impact of nanotechnologies in the field of medicine; this review will try to summarize the main concepts over liposome domain, which can count on encouraging results as target therapy associated with targeted delivery.

Purpose: The anticancer drug 5-fluorouracile (5-FU) which is indicated for the treatment of a variety of solid malignancies such as colorectal, breast, head and neck neoplasms is extensively biotransformed to 5fluoro-5,6- dihydrouracil (5-FDHU) by the dihydropyrimidine deshydrogenase enzyme (DPD). DPD deficiency is recognized as an important risk factor, predisposing patient to undergo severe/lethal toxicities. To date, relationships between 5-FU, 5- FDHU and toxicity following i.v. bolus administration has not been studied using the population pharmacokinetics approach. Methods: Retrospective pharmacokinetic data of 5-FU and 5-FDHU from 127 colorectal cancer patients were used for the population pharmacokinetic analysis. Treatment schedule consisted of an adjuvant therapy with 5-FU plus leucovorin. 5- FU and 5-FDHU complete plasma profiles recorded on day-1 of the first chemotherapy cycle were modeled simultaneously using NONMEM software. Gastro-intestinal adverse events graded according to the WHO criteria were recorded after the first cycle. A population logistic regression model was developed to identify predictive factors of these adverse events. Results: A three-compartment pharmacokinetic mixture model best described 5-FU and 5-FDHU kinetics profiles. Linear and saturated elimination from the central compartment of 5-FU and a linear elimination from the 5-FDHU compartment were used. A bimodal distribution of the inter-compartmental clearance was observed allowing two subpopulation with high (17 L/h) and low values (3.35 L/h). DPD-phenotype is suspected to explain this mixture. No covariates were introduced in the final model. Also, no relationship was found between maximal metabolism rate and DPD-phenotype. Predictive factors associated with occurrence of high grade gastro-intestinal adverse events were gender, dose and lean body mass suggesting serious cautions with the BSA-weighted dose for women. For the low-grade toxicities, 5-FU area under curve was predictive for woman and 5-FDHU area under curve for men. Conclusion: A population pharmacokinetic mixture model was developed to describe kinetic profiles of 5-FU and its major metabolite. This model has significant implications, to identify patients with potentially low DPD phenotype requiring earlier adjustment of the 5-FU dose. Also this analysis highlights the need for developing alternative dosing-scheme for women.

Pharmacogenetics has progressively become a major concern in personalized medicine. The development of modern technologies in genetic testing and cost-effectiveness have rendered genotyping strategies easy to perform comparing to time-consuming phenotyping methods. In oncology, canonical markers such TPMT, DPYD or UGT1A1 are routinely included in clinical practice but their use is still controversial partly because of insufficient genotype to phenotype correlation. The next challenge is to accurately translate genotype-phenotype correlations into clinically useful diagnostics, and clinically useful leads concerning new therapeutic targets. Besides, recent studies have focused on emerging genetic variants of ADME genes such cytidine deaminase (CDA) or pregnane X receptor (PXR) that could be of interest for predicting anticancer drug response or toxicity. The candidate gene approach “metabolism guided” now evolves towards more global strategies thanks to genome resequencing projects such HapMap that have considerably increased our knowledge of genetics variations in humans. Multiplexed genotyping methods make possible the set-up of panels of candidate or tag SNPs for subsequent haplotypic analysis. Last, genome-wide association studies (GWAS) are feasible when large cohort of patients is available to identify new loci associated with drug response or adverse drug reactions or to definitively confirm the role of candidate genetic variations.