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http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=WO2007017678&F=0
Description of WO2007017678
[0001] PYRAZOLO(1 ,5-A) PYRAMIDINE COMPOUNDS AND PHARMACEUTICAL COMPOSITIONS CONTAINING THEM
[0002] FIELD OF THE INVENTION
[0003] The present invention relates to certain pyrazolo[1 ,5-a]pyrimidine compounds, to processes for their preparation, compositions comprising them and methoda of using them. Novel screening methods are also provided.
[0004] BACKGROUND AND PRIOR ART
[0005] Apoptosis is a genetically regulated process of cell suicide that allows for the removal of unneeded, senescent or infected cells from the body while preserving the integrity and architecture of surrounding tissue. Whereas mitosis is responsible for the generation of new cells, apoptosis in contrast is responsible for removing the cells. It is this delicate balance of mitosis versus apoptosis that maintains tissue homeostasis.
[0006] Apoptotic pathways can be sub-divided into two categories, either the extrinsic apoptotic signals which are initiated on the outside of the cell by ligand engagement of cell surface receptors such as Fas and TNF receptors, and/ or the intrinsic pathways activated by signals emanating from cellular damage sensors (e.g. p53) or developmental cues. Although the pathways activated by extrinsic and intrinsic signals can overlap to some extent, receptor ligation (via an extrinsic signal) typically leads to recruitment of adapter proteins that promote caspase oligomerization and auto-processing
[0007] For example, following Fas ligand binding to the Fas receptor, the death signal is transmitted through conformational changes in preformed receptor clusters, resulting in the recruitment of the adaptor protein FADD (Fas-associated death-domain protein) through a DD-DD interaction. Once bound to Fas to form the death-inducing signalling complex, FADD then binds to the prodomain of caspase-8, which results in autoactivation of caspase-8 by proteolytic processing leading to cellular destruction {reviewed in Murphy et al Curr. Opin Pharm. 2003, 3:412-419).
[0008] In contrast, intrinsic signals usually operate by triggering the release of proteins from the mitochondria to the cytosol. Most notable among these is cytochrome c; binding of cytochrome c to a central apoptotic regulator, Apaf-1 , promotes oligomerization of Apaf-1 and, in a reaction requiring the ATPase activity of Apaf-1 , oligomerization and activation of caspase 9). Caspase 9 subsequently activates effector caspases such as 3, 6, and 7 and cellular destruction ensues (reviewed in Johnson & Jarvis 2004, Apoptosis.;9(4):423-7).
[0009] This targeted cell destruction is critical both in physiological contexts as well as pathological states. Apoptosis is the normal physiological response to many stimuli, including irreparable DNA damage. Various diseases evolve because of hyperactivation (neurodegenerative diseases, immunodeficiency, ischaemia-reperfusion injury) or suppression of programmed cell death (cancer, autoimmune disorders).
[0010] In cancer, the balance between mitosis and programmed cell death is disturbed, and defects in apoptotic pathways allow cells with genetic abnormalities to survive. The role of apoptosis in the genesis and progression of cancer has been well documented (e.g. Reed JC, 1999; J. Clin Oncol.17(9), 2941). Failure in normal apoptosis pathways contribute to carcinogenesis by creating a permissive environment for genetic instability and accumulation of gene mutations, promoting resistance to immune-based destruction, allowing disseverance of cell cycle checkpoints that would normally induce apoptosis, facilitating growth factor/hormone-independent cell survival, supporting anchorage- independent survival during metastasis, reducing dependence on oxygen and nutrients, and conferring resistance to cytotoxic anticancer drugs and radiation. Indeed, studies of colon specimens harvested at various points along the transformation of colorectal epithelium to carcinomas demonstrated a progressive inhibition of apoptosis (Bedi et al, 1995, Cancer Res. ;55(9):1811-6.)
[0011] COLON CANCER
[0012] Colorectal cancer is common in economically developed countries, particularly in Europe, North America and Australia and is the second leading causes of cancer-related deaths in the Western world. Every year, colorectal cancer is responsible for arr estimated 400,000 deaths worldwide. Approximately 60,000 people die from colorectal adenocarcinoma among the 150,000 new cases, which are diagnosed in Europe each year. A genetic contribution to colon cancer risk is suggested by two observations, namely a) an increased incidence of colorectal cancer among persons with a family history of colorectal cancer and b) families in which multiple family members are affected with colorectal cancer, in a pattern indicating autosomal dominant inheritence of cancer susceptibility (Burt et al 2004, Gastroenterology. 2004;127(2):444-51 ; Vasen et al 1996, Lancet. 17;348(9025):433-5). About 25% of patients with colorectal cancer have a family history of the disease while the remaining 75% of patients have sporadic disease, with no apparent evidence of inheriting the disease.
[0013] NATURAL HISTORY OF COLORECTAL CANCER
[0014] Colorectal tumours present with a broad spectrum of neoplasms, ranging from benign growths to invasive cancer and are predominantly epithelial in origin (i.e adenomas or adenocarcinomas). Pathologists have classified the lesion into three groups: nonneoplastic polyps, neoplastic polyps (adenomatous polyps, adenomas) and cancers.
[0015] Over 95% of colorectal cancers are carcinomas, most of which are adenocarcinomas. A personal/familial history of having colon adenomas places one at increased risk of developing colon cancer (Neale and Ritchie, in Herrera L, ed. Familial Adenomatous Polyposis. New York, NY; Alan R. Liss Inc., 1990 p61-66) suggesting that either the adenoma may reflect an innate or acquired tendency of the colon to form tumour or that adenomas might be the primary precursor lesion of the colon cancer. While there is no direct proof that the majority of colorectal cancers arise from adenomas, adenocarcinomas are generally considered to arise from adenomas because a) benign and malignant tissue occur within colorectal tumours (Perzin and Bridge 1981 , Cancer.48(3):799-819) and b) when patients with adenomas were followed for 20 years, the risk of cancer at the site of the adenoma was 25%, a rate much higher than the expected norm (Stryker et al 1987, Gastroenterology. 1987;93(5): 1009-13). In addition, removal of adenomatious polyps is associated with reduced colorectal cancer incidence (Muller and Sonnenberg 1995, Ann Intern Med. 15;123(12):904-10).
[0016] GENESIS OF COLON CANCER
[0017] The colon is organized into compartments of cells called crypts, where stem cells that reside near the bottom give rise to transit amplyifying cells that undergo five to seven additional divisions before they become terminally differentiated into one of four cell types, namely colonocytes, goblet cells, Paneth cells and enteroendocrine cells ( Brittan
[0018] & Wright 2004, Gut.;53(6):899-910). Three of the four cells types (exception being
[0019] Paneth cells) continue to migrate to the top of the crypt where they undergo apoptosis and are engulfed by stromal cells or are shed into the lumen. For tissue homeostasis to ensue, the birth rate of the colonic epithelial cells precisely equals ther rate of loss from the crypt apex. If birth/ loss ratio increases, a neoplasm occurs.
[0020] Since the differentiated epithelial cells have a fixed residency under normal conditions, it would appear that key to the genesis of colon cancer is that for cells to be able to accumulate mutations and form a polyp and early adenoma in this tissue, they have to become refractory to apoptosis. It is widely believed adenomas develop from normal stem cells through molecular abnormalities (Bach et al 2000, Carcinogenesis. 21(3):469- 76). However, a single random major deleterious molecular alteration is not sufficient to induce carcinogenesis. Indeed, even sustained expression of well known oncogenes, including SV-40 T antigen, human K-ras VaH 2 and a dominant negative mutant of human p53 alone or in combination do not lead to adenomas over a 9-12 month period (Kim et al 1993, J Cell Biol;123(4):877-93). One molecular alteration that seems pivotal to the genesis of colon cancer is the mutation of the APC protein such that approximately 85% of all colon cancers have this protein mutated. In addition, mutation of this gene seems to be one of the earliest events in the colorectal tumour progression pathway ( Kinzler & Vogelstein, 1998 in The Genetic Basis of Human Cancer (McGraw-Hill, Toronto). ). As such, the APC protein is viewed as a gatekeeper of colon cancer.