Recent Patents on Anti-Cancer Drug Discovery - Volume 2, Issue 1, 2007

E1A is a multifunctional adenoviral protein expressed early after infection that interferes with numerous important regulatory processes by interaction with host cell proteins or direct transcriptional activation of target genes. Although, initially identified as the adenoviral component that can cause malignant conversion of rodent cells, remarkable tumorsuppressive effects of E1A on various types of human cancer cells were observed. Gene therapeutic approaches with E1A are currently evaluated in animal models and early clinical studies. Therapeutic applications of E1A are covered by a series of patents which include the description of small variants (mini-E1A) that can be used for tumor suppression and E1A gene transfer in combination with conventional chemotherapy. In this mini review, we provide an introduction to E1A functions, summarize relevant patents, and discuss potential clinical applications of E1A gene transfer on basis of recent results of clinical and preclinical investigations.

Ribonucleotide Reductase (RNR) plays a critical role in DNA synthesis, and is a well-recognized target for cancer chemotherapeutic and antiviral agents. RNR inhibition precludes DNA transcription and repair, from which results cell apoptosis. Many regulation checkpoints concerning RNR activity have been unravelled through the last two decades, with potential use to inhibit enzyme activity. This was accomplished by researchers from different but complementary areas, and from which several and different inhibitors have resulted. The volume of these studies has generated over 4000 articles since the discovery of RNR in 1960. This review summarises patents and papers during the period 1958 - 2005 dealing with the present understanding of ribonucleotide reductase biochemistry, mechanism of action and the most relevant data concerning RNR inhibition. Special attention is given to the inhibitors that have been patented and are currently in clinical use.

Cytochrome P450's are enzymes which catalyze a large number of biological reactions, for example hydroxylation, N-, O-, S- dealkylation, epoxidation or desamination. Their substrates include fatty acids, steroids or prostaglandins. In addition, a high number of various xenobiotics are metabolized by these enzymes. The enzyme 17α-hydroxylase-C17,20-lyase (P45017, CYP 17, androgen synthase), a cytochrome P450 monooxygenase, is the key enzyme for androgen biosynthesis. It catalyzes the last step of the androgen biosynthesis in the testes and adrenal glands and produces androstenedione and dehydroepiandrosterone from progesterone and pregnenolone. The microsomal enzyme aromatase (CYP19) transforms these androgens to estrone and estradiol. Estrogens stimulate tumor growth in hormone dependent breast cancer. In addition, about 80 percent of prostate cancers are androgen dependent. Selective inhibitors of these enzymes are thus important alternatives to treatment options like antiandrogens or antiestrogens. The present article deals with recent patents (focus on publications from 2000 - 2006) concerning P450 inhibitor design where steroidal substrates are involved. In this context a special focus is provided for CYP17 and CYP19. Mechanisms of action will also be discussed. Inhibitors of CYP11B2 (aldosterone synthase) will also be dealt with.

New blood vessel formation (angiogenesis) is fundamental to the process of tumor growth, invasion, and metastatic dissemination. The vascular endothelial growth factor (VEGF) family of ligands and receptors are well established as key regulators of these processes. VEGF is a glycoprotein with mitogenic activity on vascular endothelial cells. Specifically, VEGF-receptor pathway activation results in signaling cascades that promote endothelial cell growth, migration, differentiation, and survival from pre-existing vasculature. Thus, the role of VEGF has been extensively studied in the pathogenesis and angiogenesis of human cancers. Recent identification of seven VEGF ligand variants (VEGF [A-F], PIGF) and three VEGF tyrosine kinase receptors (VEGFR- [1-3]) has led to the development of several novel inhibitory compounds. Clinical trials have shown inhibitors to this pathway (anti-VEGF therapies) are effective in reducing tumor size, metastasis and blood vessel formation. Clinically, this may result in increased progression free survival, overall patient survival rate and will expand the potential for combinatorial therapies. Having been first described in the 1980s, VEGF patenting activity since then has focused on anti-cancer therapeutics designed to inhibit tumoral vascular formation. This review will focus on patents which target VEGF-[A-F] and/or VEGFR-[1-3] for use in anti-cancer treatment.

Melanoma is a significant, worldwide growing public health burden. Single-agent chemotherapy or immunotherapy remains the treatment of election for this disease when systemic therapy is offered. Malignant melanoma of the skin is distinguished by its capability to early metastatic spread by means of lymphatic vessels to regional lymph nodes. Herein new accomplishments on the role of lymphangiogenesis and of angiogenesis in cutaneous melanoma will be discussed, together with the possible application of these discoveries in developing prognostic and therapeutic tools in melanoma metastasis. Furthermore, the present review will summarize the main angiogenic inhibitors reported in the recent patents (2003-2005), with special emphasis on the aspects which have important implications for the prognosis and the treatment of human melanomas.

Vascular disrupting agents (VDAs) are a new class of potential anticancer drugs that selectively destroy tumor vasculature and shutdown blood supply to solid tumors, causing extensive tumor cell necrosis. VDAs target established tumor blood vessels, which are distinct from antiangiogenic agents that prevent the formation of new blood vessels. There are two types of VDAs, small molecules and ligand-directed agents. Most of the small molecule VDAs are tubulin inhibitors, including CA4P, ZD6126, AVE8062, OXi-4503, NPI-2358, MN-029 and EPC2407. The others are synthetic flavonoids including FAA and DMXAA that induce the production of local cytokines such as TNF-alpha. VDAs have shown good antitumor efficacy in animal models, especially in combination with established anticancer agents. Several VDAs, including CA4P and DMXAA, have demonstrated good safety profile as well as some promising efficacy in phase I clinical trials. Currently CA4P and DMXAA are in phase II clinical trials and AVE8062, OXi-4503, NPI-2358 and MN- 029 are in phase I clinical trials. This review will focus on recent progress in the discovery and development of small molecule VDAs, including recently published patent applications and issued patents related with small molecule VDAs.