Current Medicinal Chemistry - Volume 24, Issue 42, 2017

Cancer is a multifactorial disease and its genesis and progression are extremely complex. The biggest problem in the anticancer drug development is acquiring of multidrug resistance and relapse. Classical chemotherapeutics directly target the DNA of the cell, while the contemporary anticancer drugs involve molecular-targeted therapy such as targeting the proteins possessing abnormal expression inside the cancer cells. Conventional strategies for the complete eradication of the cancer cells proved ineffective. Targeted chemotherapy was successful in certain malignancies however, the effectiveness has often been limited by drug resistance and side effects on normal tissues and cells. Since last few years, many promising drug targets have been identified for the effective treatment of cancer. The current review article describes some of these promising anticancer targets that include kinases, tubulin, cancer stem cells, monoclonal antibodies and vascular targeting agents. In addition, promising drug candidates under various phases of clinical trials are also described. Multi-acting drugs that simultaneously target different cancer cell signaling pathways may facilitate the process of effective anti-cancer drug development.

Cancer is considered as one of the world's leading causes of morbidity and mortality. Over the past four decades, spectacular advances in molecular and cellular biology have led to major breakthroughs in the field of cancer research. However, the design and development of anticancer drugs prove to be an intricate, expensive, and time-consuming process. To overcome these limitations and manage large amounts of emerging data, computer- aided drug discovery/design (CADD) methods have been developed. Computational methods can be employed to help and design experiments, and more importantly, elucidate structure-activity relationships to drive drug discovery and lead optimization methods. Structure- and ligand-based drug designs are the most popular methods utilized in CADD. Additionally, the assimilation provided by these two complementary approaches are even more intriguing. Nowadays, the integration of experimental and computational approaches holds great promise in the rapid discovery of novel anticancer therapeutics. In this review, we aim to provide a comprehensive view on the state-of-the-art technologies for computer-assisted anticancer drug development with thriving models from literature. The limitations associated with each traditional in silico method have also been discussed, which can help the reader to rationale the best computational tool for their analysis. In addition, we will also shed some light on the latest advances in the computational approaches for anticancer drug development and conclude with a brief precis.

This review addresses in-depth recent structure-activity relationship (SAR) studies published in 2015 on new marine compounds and their synthetic analogues with potential or established anticancer activity. Priority was given to papers on in vitro screening methods of marine-derived bioactive compounds, usually performed using panels of human cancer cell lines, as a first step of the anticancer drugs discovery process. Our review describes compounds belonging to different classes of substances, namely terpenoids, glycosides, alkaloids, steroids, as well as other small molecular compounds. We believe that our review will not only help chemists in the design and synthesis of novel anticancer compounds possessing specific cytotoxic or cytostatic activity in human cancer cells, but will also extend the existing databases comprising data on bioactivity of marine natural compounds.

Intrinsic or acquired chemoresistance represents the main obstacle to the successful treatment of cancer patients. Several mechanisms are involved in multidrug resistance: decreased uptake of hydrophilic drugs, increase of energy dependent efflux, alteration of the redox state, alteration of apoptotic pathways, and modification of the tumor microenvironment. In recent years, several types of nanoparticles have been developed to overcome these obstacles and improve the accumulation and release of drugs at the pathological site. In this review, we describe the main mechanisms involved in multidrug resistance and the nanovehicles which have been proposed to target specific aspects of this phenomenon.

Proteases are involved in a variety of processes associated with tumor development and progression. Because of their integral role in extracellular matrix and basal lamina degradation they play important roles in cancer cell migration, invasion, angiogenesis and metastasis. They are also involved in cancer cell signaling, the epithelial-mesenchymal transition, the antitumor immune response, cell de-differentiation and cancer stem cell remodeling. Their involvement in pro-tumorigenic processes makes them interesting targets for anticancer therapy. The most promising are matrix metalloproteases, cysteine cathepsins, the urokinase-type plasminogen activator system and proteasome; these constitute the focus of this review. Several inhibitors have been developed for reducing their activities that are in different phases of development, with some already in clinical use. However, systemic delivery of protease inhibitors can result in undesired reduction of proteolytic activity in normal tissues, leading to adverse effects and limited therapeutic efficacy. This caveat can be circumvented by nanoparticle delivery systems that direct protease inhibitors specifically to cancer cells. In this article we review the current state of nanoparticle delivery systems for delivering protease inhibitors to cancer cells.

Protein kinases are versatile molecule switches that govern functional processes in signal transduction networks and regulate fundamental biological processes of cell cycle and organism development. The continuous growth of biological information and a remarkable breath of structural, genetic, and pharmacological studies on protein kinase genes have significantly advanced our knowledge of the kinase activation, drug binding and allosteric mechanisms underlying kinase regulation and interactions in signaling cascades.. Structural and biochemical studies of the genetic and molecular determinants of protein kinases binding with inhibitors have been the cornerstone of drug discovery efforts in clinical oncology leading to proliferation of effective anticancer therapies. Recent advances in understanding allosteric regulation of protein kinases have fueled unprecedented efforts aiming in the discovery of targeted and allosteric kinase inhibitors that can combat cancer mutants and are at the forefront of the precision medicine initiative in oncology. Despite diversity of regulatory scenarios underlying kinase functions, dimerization-driven activation is a common mechanism of allosteric regulation that is shared by many protein kinase families, most notably ErbB and BRAF kinases that play a central role in growth factor signaling and human disease. In this review, we focused on structural, biochemical and computational studies of the ErbB and BRAF kinases and discuss how diversity of the structural landscape for these kinase genes and dimerization- dependent mechanisms of their regulation can be leveraged in the design and discovery of kinase inhibitors and allosteric modulators of kinase activation. The lessons from this analysis could inform discovery of specific targeted therapies and robust drug combinations for cancer treatment.

Nucleic acids are prone to structural polymorphism and a number of structures may be formed in addition to the well-known DNA double helix. Among these is a family of nucleic acid four-stranded structures known as G-quadruplexes (G4). These quadruplex structures can be formed by sequences containing repetitive guanine-rich tracks and the analysis of Non-B-DNA database indicated an enrichment of these sequences in genomic regions controlling cellular proliferation, such as for example in the promoter regions of c- MYC, k-RAS, c-KIT, HSP90 and VEGF among others. The broad concept of G4 targeting with small molecules is now generally accepted as a promising novel approach to anticancer therapy and several small molecules with antiproliferative activity in cancer cell lines have also been shown to stabilize these DNA structures, thus suggesting a potential application of G4-interactive small molecules as new anticancer drugs. Herein we review, by targeted oncogene and main chemical scaffold, those G4-interactive small molecules with reported gene expression modulatory activity in cancer cell lines. The data obtained so far are encouraging but further efforts are needed to validate G4 as drug targets and optimize the structure of G4- interactive small molecules into new anticancer drugs.

Background: Cancer chemotherapy is limited by severe side effects due to unspecific cytotoxic activity of currently used therapeutics. In order to minimize these unwanted effects, several approaches have been taken, relying on the use of light to activate drugs. As light can be delivered with a very high spatiotemporal resolution, this technique is a promising strategy to selectively activate cytotoxic drugs at their site of action and thus to improve the tolerability and safety of chemotherapy. Objective: This review summarizes different approaches towards photoactivated chemotherapy and identifies its challenges and opportunities. Results: The respective papers were summarized and evaluated in terms of their phototherapeutic indices and the wavelength needed for activation. First, the design, synthesis and/or evaluation of photoactivated metal complexes including platinum- , ruthenium-, and rhodium-complexes is described. Next, photocaged metal complexes and photoacaged organic chemotherapeutics are reported, with a wide range of cytotoxicity mechanisms. The final part includes, examples of photoswitchable drugs for cancer therapy. Some designs, especially metal complexes, stand out due to their very high phototherapeutic index (> 1880) but the common drawback of light-responsive metal complexes and organic chemotherapeutics is the irreversibility of activation. Photoswitchable drugs, however, address this challenge. Nevertheless, the need of UV light for their activation still limits their application. Conclusion: The field of photoactivated cancer chemotherapy is rapidly growing and already includes very promising approaches with designs providing high phototherapeutic indices and also NIR or visible light-activatable drugs.