Current Drug Discovery Technologies - Volume 8, Issue 2, 2011

The key regular functions of microRNAs (miRNAs) were only discovered a few years ago, when it became evident that miRNAs play important roles in gene regulation. Today, more than 700 miRNAs have been identified from the human genome. Because of their regulatory functions in transcription, signal transduction, cell cycle regulation, proliferation, cell growth, apoptosis, cell metabolism and neurogenesis, malfunctioning miRNAs have been suggested to affect a number of diseases. Indeed, absence of miRNAs or their mutations has been associated with various types of cancers and other diseases such as neurodegenerative, autoimmune, cardiovascular, infectious, metabolic and oncologic diseases. This has been confirmed by genetic analysis of patient samples. The disease association has attracted potential diagnostic and therapeutic applications of miRNAs. A significant issue to achieve successful therapy is the delivery of miRNAs as problems of targeted and long-lasting presence of miRNA exist. Different approaches have included the modification of miRNAs and the use of viral delivery vectors.

Significant efforts through genomic approaches have been dedicated toward the identification of novel proteinprotein interactions as promising therapeutic targets for indications such as Alzheimer's disease, Parkinson's disease and neuropsychiatric disorders. Additionally, the number of biotherapeutic agents entering the Pharmaceutical sector continues to increase and according to EvaluatePharma's “World Preview 2014” report, “the compounded annual growth rate of biologics is expected to be 8.5 percent from 2008-2014, eight to 10 times greater than the growth rate of small molecules”. However, there are limited examples of success in developing biotherapeutic modalities for central nervous system (CNS) diseases in the drug development pipeline. A primary reason for the lack of application of biotherapeutics to neuroscience targets, is that the blood-brain barrier (BBB) isolates and protects CNS structures creating a unique biochemically and immunologically privileged environment, therefore passage of macromolecules across this barrier has additional challenges. An understanding of the anatomical and physiological properties of this barrier with respect to penetration of biotherapeutics is presented in this review document. In this summary, recent advances in biotherapeutic delivery mechanisms across the BBB including transcranial brain drug delivery, focused ultrasound technology, nasal delivery, absorptive endocytosis, and receptor mediated endocytosis are evaluated using an industrial perspective. With acknowledgement that each approach has advantages and disadvantages, this review discusses the opportunities and challenges that are encountered during application of these methods across a variety of therapeutic areas such as, pain, obesity, neuroscience, and oncology. Utilizing an industrial perspective, including consideration of cost of goods and commercial feasibility for these approaches, this review highlights technology features which would enable industry investments toward novel BBB delivery technologies for biologics. Through continued development and improvement of such technology, new therapeutic options to treat and potentially cure central nervous system diseases could eventually evolve.

Despite significant improvements in ways to treat cancer, numerous patients still die from this disease. One of the reasons for this inability to cure cancer is the lack of ability of drugs to penetrate target cells properly. While studies on drug resistance have focused on the molecular mechanisms of single cells, there has been little attention on drug penetration or distribution in solid tumor tissues. It is reported that the factors that obstruct the penetration and distribution of drugs in solid tumors are closely related to the microenvironment of solid tumors. This review paper aims to discuss the microenvironment that hinders drug penetration in solid tumors and to investigate whether or not changes in the microenvironment can improve drug penetration. This review also introduces in vitro 3D multicellular culture systems that can reproduce the characteristics of solid tumors in vivo and that are required for such studies.

Feature selection has become increasingly important for quantitative structure-activity relationship (QSAR) studies. In the present article, we evaluate three state-of-the-art feature selection algorithms, namely mutual information (MI), genetic algorithm (GA), and support vector machine regression (SVR)-based recursive feature elimination (SVRRFE), in the reduction of high dimensional feature space for QSAR regression. We used SVR to evaluate the performance of these feature selection algorithms. In addition, we present a simple but very efficient iterative strategy for optimizing parameters for SVM-RFE algorithm. All three algorithms can effectively reduce the number of features and often achieve improved performance.

Human immunodeficiency virus (HIV) starts to replicate upon virus-cell fusion mediated by the CD4-Envcoreceptor interaction. HIV enters target cells also through endocytosis, a mechanism which rarely leads to HIV replication. Both modes of entry are greatly improved by cell-cell contact. We recently reported that the contact of human primary dendritic cells with HIV-1 infected cells leads to high levels of virus endocytosis and HIV-1 antigen presentation activity in dendritic cells. Here, we provide evidence that the activity of matrix metalloproteinase (MMP)-9 is involved in the mechanism of cell-to-cell HIV-1 endocytosis in DCs. Accordingly, the specific inhibition of MMP-9 led to reduced extents of HIV-1 antigen presentation activity. The identification of cell molecules involved in the cell-to-cell HIV-1 endocytosis would be of significance for better understanding the mechanisms underlying the induction of the anti-HIV adaptive immune response.

Obesity has been associated with both the carcinogenesis and poor prognosis of colon cancer, one of the leading causes of cancer-related death. Increased blood levels of insulin in obese subjects have been demonstrated to play a key role in carcinogenesis. It is also possible that insulin affects treatment efficacy, leading to poor prognosis. In this study, we demonstrated that insulin can increase HT29 colon cancer cell line resistance to cycloheximide and 5- fluorouracil induced cytotoxicity. This effect can be inhibited by the PI3K/Akt inhibitor Ly294002, indicating the important role of this pathway in the insulin-induced inefficacy of chemotherapy. The insulin-induced resistance to cycloheximide and 5-fluorouracil can be used in drug screening to overcome the inefficacy of chemotherapy in obesity-associated colon cancer.

The aim of this study was to develop a pH-sensitive chitosan/polyvinyl pyrrolidone (PVP) based controlled drug release system for repaglinide. The hydrogels were synthesised by crosslinking chitosan and PVP blend with glutaraldehyde to form a semi-interpenetrating polymer network (semi-IPN). These semi-IPNs were studied for their content uniformity, swelling index (SI), mucoadhesion, wettability, in vitro release and their release kinetics. The hydrogels showed more than 95% loading of repaglinide. These hydrogels showed high swelling and mucoadhesion under acidic conditions. The swelling was found due to the protonation of a primary amino group on chitosan. In acidic condition chitosan was ionized, and adhesion occurred between the positively charged chitosan and the negatively charged mucus. In the physiological condition less swelling was noticed. In vitro release study revealed that formulation containing chitosan (2% w/v) and PVP (4% w/v) in the ratio of 14:6 w/w showed complete drug release after 12h. Release profile showed that all the formulations followed non-fickian diffusion mechanism (diffusion coupled with swelling). Fourier Transform Infrared (FTIR) spectroscopic analysis revealed proper crosslinking of polymer and formation of semi-IPN as well as presence of drug in the formulation. Differential Scanning Calorimetry (DSC) and Powder X-Ray Diffraction (p-XRD) study revealed the presence of repaglinide in crystalline form in the formulations. The surface morphology of semi-IPN was studied before and after dissolution in Simulated Gastric Fluid (SGF, pH 1.2) which indicated generation of open channellike structure in hydrogel after dissolution. The results of study suggest that semi-IPNs of Chitosan/PVP are potent candidates for delivery of repaglinide in acidic environment.

Dutasteride loaded liposomal system were developed for topical application in order to avoid the side effects associated with the oral administration of the drug. Drug-loaded multilamellar liposomes were prepared using thin-film hydration method followed by sonication and optimized with respect to entrapment efficiency, drug payload, size and lamellarity. The vesicular systems consisting of egg phosphatidylcholine (100 mg), cholesterol (50 mg), and dutasteride (5 mg) showed highest drug entrapment efficiency (94.6%) and drug payload (31.5 μg/mg of total lipids). Mean vesicle size of these liposomes was noted to be 1.82 ± 0.15 μm. Significantly higher skin permeation of dutasteride through excised abdominal mouse skin was achieved via the developed liposomal formulations as compared to hydro-alcoholic solution and conventional gels. The formulation exhibited about seven fold higher deposition of drug in skin. Stability studies indicated that the liposomal formulations were quite stable in the refrigerated conditions for 10 weeks with negligible drug leakage or vesicle size alteration. Results of the current studies exhibited improved and localized drug action in the skin and thus could be considered as a better option to cure androgenetic alopecia.

Nifedipine is a dihydropyridine calcium channel antagonist effective in the clinical management of cardiovascular disease. Due to nifedipine's poor water solubility and erratic bioavailability, complexation with selected cyclodextrins was studied in order to overcome these limitations. The aim was to develop a quantitative structure property relationship (QSPR) to identify cyclodextrin molecular properties important in complex formation and provide a predictive tool which would be valuable during preformulation studies. The QSPR developed indicates that the major driving forces for nifedipine complexation, in addition to cyclodextrin concentration, are hydrophobicity and Van der Waals interactions (3D solubility parameters, hydrophilic surface area and differential connectivity index).