Inhibitors of CD73 May Provide a Treatment for Cancer and Autoimmune Diseases

Patent Application Title:	Benzothiadiazine Compounds
Patent Application Number:	WO 2017/098421 A1	Publication date:	15 June 2017
Priority Application:	US 62/264,419	Priority date:	8 December 2015
Inventors:	Adams, J. L.; Ator, L. E.; Duffy, K. J.; Graybill, T. L.; Kiesow, T. J.; Lian, Y.; Moore, M. L.; Ralph, J. M.; Ridgers, L. H.
Applicant:	GlaxoSmithKline Intellectual Property Development Limited; 980 Great West Road, Brentford Middlesex TW89GS (GB)
Disease Area:	Cancer, precancerous syndromes, AIDS, autoimmune diseases, infections, atherosclerosis, and ischemia-reperfusion injury	Biological Target:	The cluster of differentiation 73 (CD73)

Summary:	The invention in this patent application relates to substituted benzothiadiazine derivatives represented generally by formula I. These compounds are inhibitors of CD73 and may potentially be useful for the treatment of cancer, precancerous syndromes, and other diseases associated with CD73 activities, such as AIDS, autoimmune diseases, infections, atherosclerosis, and ischemia-reperfusion injury.
	Conditions such as infection, tissue injury, ischemia, or intervention-induced tumor cell death cause sharp elevation of local extracellular adenosine triphosphate (ATP). Increased level of ATP serves as a danger signal to alert the immune system to initiate multiple pro-inflammatory events, including the recruitment of macrophages and dendritic cells. The extracellular ectonucleotidases CD73 and CD39 dephosphorylate extracellular ATP to lower its levels and replace it with extracellular adenosine. This results in sharp increase of the concentration of adenosine from a low homeostatic level of 20–200 to 1000–10000 nM. Elevated adenosine concentrations engage the immunosuppressive actions of adenosine A2A and A2B receptors on the infiltrating lymphocytes to shield the cells from excessive inflammatory response and thereby provide a self-limiting mechanism to resolve the immune response. It was observed that hypoxia can increase the adenosine levels in a solid tumor by 10–20-fold compared to normal cell levels. It is believed that such elevated level of adenosine will maintain a chronic suppression of the innate immune response, which leads to immune tolerance and subsequently to uncontrolled malignant growth.
	The cluster of differentiation 73 (CD73), also known as 5′-ribonucleotide phosphohydrolase, is a glycophosphatidylinositol-anchored di-Zn2+ metallo-phosphatase specific for the dephosphorylation of purine and pyrimidine ribo- and deoxyribonucleoside monophosphates to the corresponding nucleosides. CD73 has high affinity to adenosine monophosphate (AMP) and catalyzes its conversion to the bioactive adenosine. It is believed that this process is the major contributor to extracellular adenosine formation in the tumor microenvironment. Expression of CD73 is directly regulated by the hypoxia-inducible factor 1α (HIF1α), which explains the observed increase in extracellular adenosine under hypoxic conditions. CD73 was found to be overexpressed in leukemia and in multiple solid tumor types, including aggressive and difficult to treat tumors, such as glioblastoma and ovarian tumors. Studies have shown that T-regulatory cells (TReg) (both circulating and tumor associated) express both CD73 and CD39 in patients with head and neck squamous cell carcinoma (HNSCC). Thus, there is a mechanism to convert ATP to adenosine that depends only on TReg cells. Multiple studies employing small-interfering ribonucleic acids (siRNA), transgenic knockouts, and overexpression models have confirmed the involvement of CD73 in the generation of adenosine and promotion of immune tolerance. Therefore, inhibitors of CD73 may potentially be able to relieve the adenosine-mediated immunosuppression of the tumor microenvironment and may provide a viable treatment for cancer, either alone or in combination with other agents.
	As a consequence of decreasing extracellular adenosine by CD73 inhibitors, they may also be useful for the treatment of other diseases mediated by adenosine and its action on adenosine receptors. Thus, it is possible to use CD73 inhibitors for enhancing immune responses, enhancing immunization, and increasing inflammatory responses, as well as for the treatment of a wide range of conditions including neurological, neurodegenerative, and CNS diseases, including depression, Parkinson’s disease, cerebral and cardiac ischemic diseases, sleep disorders, and fibrosis.
Important Compound Classes:
Key Structures:	The inventors described the structures and syntheses of 187 examples of formula I, including the following representative examples:
Biological Assay:	CD73 Assay
Biological Data:	The compounds of formula I were tested using the CD73 enzyme assay, and in at least one experimental run in each case, they exhibited pIC50 values between 5 to 8.4 against CD73. The reported pIC50 values for the above representative examples are listed in the following table:
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The author declares no competing financial interest.