Recent Patents on Anti-Cancer Drug Discovery - Volume 3, Issue 2, 2008

Current standard treatments for cancer are associated with major dose-limiting toxic effects on healthy tissue. The mucosal layers of the body are particularly sensitive to regimen-induced damage, with patients suffering many unpleasant and potentially life-threatening side-effects. In recent years, there has been an increase in the understanding of the pathobiology of regimen-related mucosal injury which has lead to a number of exciting inventions for its prevention and treatment being recently patented. Agents such as growth factors, cytokines, receptor agonists/antagonists and antiinflammatory agents are among those in development in this emerging field. The complexity of mucosal injury poses a challenge for researchers, however rational targeting of intervention strategies to critical mechanisms will lead to further progress.

Dimerization of epidermal growth factor receptor (EGFR) on the cell membrane of tumor cells has been implicated in triggering a complex signal cascade that leads to increased tumor proliferation and survival. Cetuximab is a human-murine chimeric monoclonal antibody designed to target EGFR and competitively inhibit dimerization by circulating ligands. By this mechanism, it works to prevent this signal cascade thus hindering tumor proliferation. Cetuximab has been shown in a randomized phase III clinical trial to significantly increase overall survival when it is added to radiation therapy in the treatment of locally advanced squamous cell carcinoma of the head and neck. In this manuscript, the mechanism of cetuximab with its associated patents is reviewed, with its role with chemotherapy and radiation in the management of head and neck cancer along with future directions of this targeted cancer therapy.

Immunity is responsible for recognition and elimination of infectious particles and for removal of cellular waste, modified self structures and transformed cells. Innate or natural immunity acts as a first line defense and is also the link to acquired immunity and memory. By using the human hybridoma technology, a series of monoclonal antibodies and several new tumor-specific targets could be identified. A striking phenomenon of immunity against malignant cells is that all so far isolated tumor-specific antibodies were germ-line coded natural IgM antibodies. And neither in animals nor in humans affinity-maturated tumor-specific IgG antibodies have been detected so far. These IgM´s preferentially bind to carbohydrate epitopes on post-transcriptionally modified surface receptors, which are recently patented and preferentially remove malignant cells by inducing apoptosis to avoid inflammatory processes. Our “biology-” or “function-driven” method represents a unique yet powerful approach compared to the typical approaches on screening compounds or antibodies against non-validated targets (mostly differentially expressed). Moreover, the approach creates a competitive patenting strategy of creating proprietary antibodies and validated targets at the same time, which has the potential of further streamlining the discovery of new cancer therapies.

Gastrointestinal stromal tumors (GISTs) comprise a recently defined entity of the most common mesenchymal neoplasms of the gastrointestinal tract. Advances in the understanding of the molecular mechanisms of GIST pathogenesis have resulted in the development of a treatment approach which has become a model of targeted therapy in oncology. The introduction of imatinib mesylate (inhibiting KIT/PDGFRA (platelet-derived growth factor receptor-α) and their downstream signaling cascade) has revolutionized the therapy of advanced (inoperable and/or metastatic) GISTs. Imatinib has now become the standard of care in the treatment of patients with advanced GIST. However, a majority of patients eventually develop clinical resistance to imatinib. Over the last few years major progress has been made in elucidating the mechanism of disease progression (as secondary mutations in KIT and/or PDGFRA kinase domains) and resistance to imatinib. Currently, the sole approved second-line drug is sunitinib - a multitargeted agent, an inhibitor of tyrosine kinase, of KIT and PDGFRA/B and of the vascular endothelial growth factor receptors (VEGFRs)-1, -2 and 3, FMS-like tyrosine kinase-3 (FLT3), colony stimulating factor 1 receptor (CSF-1R), and glial cell-line derived neurotrophic factor receptor (REarranged during Transfection; RET). However, a number of new generation tyrosine kinase inhibitors, alone or in combination, are being evaluated at present alongside treatment options alternative to inhibiting the KIT signaling pathway (as heat shock protein 90 or mammalian target of rapamycin). This article discusses the factors relating to imatinib resistance as well as upcoming potentially effective treatment options for patients with progressive disease available in 2008 and those under investigation with more individualized treatment methods, which has been recently patented. This review focuses on the current achievements in targeted therapy of advanced GISTs, and how the insight into the resistance mechanisms may allow in the near future to treat patients with advanced GISTs.

Breast cancer management has become increasingly complex, requiring the integration of data not only from the patient's history and imaging modalities but also from specific tumor biomarkers and gene expression. Targeted and biologic therapies in breast cancer continue to evolve rapidly. The field of molecular targeted therapy has emerged. Its ultimate goal is to personalize and simplify treatment as well as minimize toxicity. This review aims at highlighting the current state-of-the-art in novel molecular targeted therapies for breast cancer based on multi-targeted small molecule tyrosine kinase inhibitors (TKI). The first two agents in this group entering clinic, Lapatinib (GW572016; Tykerb ®) and SUNITINIB (SU11248; Sutent®) are discussed. This review article also includes relevant patents.

Use of monoclonal anti-CTLA4 antibodies represents a new promising strategy to block the activation of immunosuppressive CTLA-4 and thus induce tumour regression. This review is mainly focused on the report of existing data on the clinical use of Ipilimumab (formerly MDX-010) in the treatment of metastatic melanoma. Several phase I and II trials have been conducted to evaluate safety and efficacy of this form of immunotherapy either alone or in combination with vaccines or chemotherapy in patients with stage III or stage IV melanoma. Results from these studies are presented, patented and discussed. The mechanism of ipilimumab action may take time to induce an anti-tumour immune response and thus it is recommended that ipilimumab therapy should be carried out for at least 12 weeks, even in the presence of early progressive disease. Objective response of around 15% has been reported in patients treated with ipilimumab. However, ipilimumab-mediated objective response and stable disease tend to be durable. The therapy with ipilimumab is associated with different side effects classified as immune-related adverse events (IRAEs). The most common IRAEs are enterocolitis and dermatitis. Majority of IRAEs disappear with the discontinuation of ipilimumab anti-CTLA-4 therapy. Several phase II/III trials are ongoing to evaluate ipilimumab alone or in combination with other therapeutic modalities. Results from these trials are awaited.

Aurora kinases (AK) are the name given to a family of Serine/threonine (Ser/Thr) protein kinases. These proteins represent a novel family of kinases crucial for cell cycle control. The cell division process is one of the hallmarks of every living organism. Within the complete cell-cycle process, mitosis constitutes one of the most critical steps. The main purpose of mitosis is to segregate sister chromatics into two daughters cells. It is a complex biologic process, and errors in this mechanism can lead to genomic instability, a condition associated with tumorigenesis. This process is tightly regulated by several proteins, some of them acting as check-points that ultimately ensure the correct temporal and spatial coordination of this critical biologic process. Among this network of mitotic regulators, AK play a critical role in cellular division by controlling chromatid segregation. Three AK family members have been identified in mammalian cells: A, B, and C. These proteins are implicated in several vital events in mitosis. In experimental models, overexpression of AK can induce spindle defects, chromosome mis-segregation, and malignant transformation. Conversely, downregulation of AK expression cause mitotic arrest and apoptosis in tumor cell lines. The expression levels of human AK are increased in certain types of cancer including breast, colon, pancreatic, ovarian, and gastric tumors. This observation has lent an interest to this family of kinases as potential drug targets for development of new anticancer therapies. This review focuses in recent progress in the role of AK in tumorogenesis and the development of new anticancer drug against AK proteins. This manuscript includes some relevant patents as well.

Recently, the search for more effective and safer antineoplastic agents has led to synthesis and introduction into preclinical and clinical studies of a few new purine nucleoside analogues (PNA). Three of them: clofarabine (CAFdA), nelarabine, and forodesine (immucillin H, BCX-1777), despite belonging to the same group of drugs such as PNA, have shown some differences concerning their active forms, metabolic properties and mechanism of action. However, all these drugs have demonstrated promising activity in patients with relapsed and refractory acute lymphoblastic leukemia (ALL). CAFdA was approved for the therapy of relapsed or refractory ALL in the third line of treatment. It has proved promising in pediatric patients as well as in some patients who are able to proceed to allogenic hematopietic stem cell transplantation (HSCT). Moreover, the drug exhibits an efficacy in acute myeloid leukemia (AML), blast crisis of chronic myelogenous leukemia (CML-BP) and myelodysplastic syndrome (MDS). Nelarabine is recommended for T-ALL and T-cell lymphoblastic lymphoma (T-LBL) with the overall response rates ranging from 11 to 60%. However, the use of the drug is limited by potentially severe neurotoxicity. Forodesine is a purine nucleoside phosphorylase (PNP) inhibitor and it has shown activity in relapsed and refractory T- and B-cells leukemias as well as in cutaneous T-cell lymphoma (CTCL). Recently patented, a few of inventions in the field of pharmaceutical preparation of new PNA have also been published. Great hopes are currently set on the use of these drugs in the treatment of lymphoid and myeloid malignancies in adult and in pediatric patients, however ongoing studies will help to define their role in the standard therapy.

Cancer is a common disease in Western society that can affect any organ system. It has a high morbidity and mortality despite advances in treatment over the last hundred years. There is a clear need for new approaches to cancer chemotherapy including the possibility of reducing systemic adverse effects associated with current treatments. Vesicle trafficking is an essential cellular process that is perhaps not fully recognized. There is mounting evidence that vesicle trafficking, including the release of extracellular microvesicles, is a highly important process in tumourigenesis. Diverse aspects of tumourigenesis including invasion, metastasis, cell cycle regulation, angiogenesis, tumour immune privilege, neoplastic coagulopathy and multidrug resistance can be explained by altered vesicle trafficking in cancer cells. This paper reviews the evidence in the scientific and patent literature for the role of vesicle trafficking in tumourigenesis and suggests a number of targets and strategies that may be important for cancer therapeutics.

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