Potential of PI3Kβ Inhibitors in the Treatment of Cancer and Other Diseases

Patent Application Title:	Quinoxaline and Pyridopyrazine Derivatives as PI3Kβ Inhibitors
Patent Application Number:	WO 2017/060406 Al	Publication date:	13 April 2017
Priority Application:	EP 15189163.7	Priority date:	9 October 2015
	EP 16174710.0		16 June 2016
Inventors:	Angibaud, P. R.; Querolle, O. A. G.; Berthelot, D. J.-C.; Meyer, C.; Willot, M. P. V.; Meerpoel, L.
Applicant:	Janssen Pharmaceutica NV; Tumhoutseweg 30, 2340 Beerse (BE)
Disease Area:	Cancer, cardiovascular, autoimmune, inflammatory, and neurodegenerative diseases among others.	Biological Target:	The phosphoinositide-3-kinase PI3Kβ

Summary:	The invention in this patent application relates to substituted quinoxaline and pyridopyrazine derivatives, represented generally by formula I. These compounds possess activities as PI3Kβ inhibitors and may be useful for the treatment or prevention of cancer, autoimmune disorders, cardiovascular diseases, inflammatory diseases, neurodegenerative diseases, allergy, pancreatitis, asthma multiorgan failure, kidney diseases, platelet aggregation, sperm motility, transplantation rejection, graft rejection, lung injuries, and probably others.
	Phospholipids are key components of cell membranes. Phosphatidic acids are important phospholipids, which are structurally classified as diacyl glycerol phosphate or as mixed triglycerides. They are generally made by esterification of the hydroxyl groups of glycerol with a saturated fatty acid on C1, an unsaturated fatty acid on C2, and phosphoric acid on C3. These molecules are amphiphilic in nature since they contain both hydrophobic (fatty acid esters) and hydrophilic (phosphate ester) structural components. An important phosphatidic acid is phosphatidylinositol (PtdIns). PtdIns is a key membrane constituent made by esterification of glycerol with stearic, arachidonic, and phosphoric acids on C1, C2, and C3 (of glycerol), respectively. In addition, the phosphate group is linked to the C1′–OH of an l-myo-inositol ring as illustrated below. The inositol ring of PtdIns contains five free hydroxy groups, which can all be potentially phosphorylated by specific kinases. However, only the C3′, C4′, and C5′ hydroxyl groups can be phosphorylated to form mono-, di-, or triphosphates. The lack of phosphorylation on C2′ and C6′ hydroxyls is probably due to steric hindrance. Phosphorylated PtdIns are generally named phosphoinositides, and they perform key roles in lipid signaling, cell signaling, and membrane trafficking.
	Phosphoinositide-4,5-bisphosphate-3-kinases (PI3Ks) are a family of enzymes with multiple cellular functions such as cell growth, proliferation, differentiation, motility, survival, and intracellular trafficking, all of which are involved in cancer. PI3K enzymes phosphorylate the C3′-hydroxy group of the inositol ring of PtdIns. The PI3Ks family is divided, based on substrate specificity, tissue distribution, and mechanism of action, into three classes: class I, class II, and class III. Class I PI3Ks are the most associated with human cancer. They are heterodimeric molecules made by the dimerization of a catalytic and a regulatory subunit. Class I PI3Ks enzymes are further divided into two subclasses:
	Class IA: this group contains a p110 catalytic subunit (exist in three variants: p110α, p110β, and p110δ) that associate with a p85 regulatory subunit (exist in five variants: p85α, p55α, p50α, p85β, and p55γ) to generate three heterodimeric isoforms, PI3Kα, PI3Kβ, and PI3Kδ. These heterodimeric isoforms are inactive and remain this way until activated. Class IB: it contains only p110γ catalytic subunit that associates with either p101 or p84 regulatory subunit to form PI3Kγ heterodimeric isoform.
	Class IA PI3Ks are activated in a variety of solid and nonsolid tumors via mutation or deletion of a lipid phosphatase tumor suppressor named phosphatase and tensin homologue (PTEN) or by activating mutations of p110α. Additionally, PI3Ks are activated by receptor tyrosine kinases (RTKs), and p110β can be activated by G-protein coupled receptors. Activated class IA PI3Ks main function is to catalyze the phosphorylation of phosphatidylinositol-4,5-bisphosphate (PIP2) to form phosphatidylinositol-3,4,5-triphosphate (PIP3). PTEN antagonizes the activity of the PI3Ks by catalyzing the dephosphorylation of PIP3. PIP3 binds to a subset of lipid-binding domains of downstream targets such as the pleckstrin homology domain of protein kinase B (a serine/threonine-specific protein kinase also known as Akt). This binding recruits Akt to the plasma membrane where it phosphorylates several effector molecules that participate in biological processes such as metabolism, differentiation, proliferation, longevity, and apoptosis.
	Studies suggest a key role for p110β in causing deficiency of PTEN in cancerous tumors. The genetic knockout of p110β, but not p110α, in a mouse model resulted in blocking tumor formation and Akt activation driven by loss of PTEN in the anterior prostate. Furthermore, a subset of PTEN-deficient human tumor cell lines is sensitive to inactivation of p110β rather than p110α. PTEN deficiency was observed frequently in human cancers such as glioblastoma multiforme (GBM), endometrial, lung, breast, and prostate cancers.
	These findings suggest that inhibition of p110β may be therapeutically beneficial for the treatment of PTEN-deficient cancers. Another benefit from targeting p110β may lead to a new antithrombotic therapy. Studies in mouse models showed that inhibition of PI3Kβ can prevent stable integrin aIIbb3 adhesion contacts that eliminate occlusive thrombus formation without prolongation of bleed time.
	Other studies have shown that PI3K/Akt pathway is frequently activated during prostate cancer (PCa) progression through the loss or mutation of the PTEN gene. The PI3K/Akt pathway is the second major driver of PCa growth following the androgen receptor (AR) pathway. The efficacy of PI3K/Akt-targeted agents in PTEN-negative PCa models has improved when combined with hormonal therapy. Upregulation of AR-target genes upon PI3K/Akt inhibition suggests a compensatory crosstalk between the PI3K-AR pathways, which, for optimal efficacy treatment, could require cotargeting of the AR axis. Therefore, it may be advantageous to combine the use of PI3Kβ inhibitors with antiandrogen therapies such as androgen receptor antagonists and inhibitors of androgen biosynthesis in the treatment of PTEN-negative prostate cancers.
	Thus, there is a strong need for the discovery and development of novel selective PI3Kβ kinase inhibitors such as the compounds of formula I, described in this patent application, which may potentially provide new treatment and/or prevention of many kinds of cancer, in particular PTEN-deficient cancers, more particularly prostate cancer.
Important Compound Classes:
Key Structures:	The inventors reported the structures of 408 compounds of formula I; many of them contain a chiral center and were resolved to the pure enantiomers. The following are representative examples; chiral centers are marked by *:
Biological Assay:	Enzyme Binding Assays (KINOMEscan) Cellular assays
Biological Data:	The inhibitor binding constant (Kd) data from enzyme binding assay of the above representative examples are listed in the following table:
	The IC50 data obtained from cellular assays of the above representative examples are listed in the following table. Cellular activities of PI3Kβ inhibitors were determined by quantifying the phosphorylation of Akt in PC-3 cells.
Recent Review Articles:	1. Torti M.Blood 2015, 125( (5), ), 750–751.
	2. Cescon D. W.; Gorrini C.; Mak T. W.. Cancer Cell 2015, 27 ( (1), ), 5–7.
	3. Lin H.Chin. J. Chem. 2013, 31 ( (3), ), 299–303.
	4. Ilic N.; Roberts T. M.. Curr. Top. Microbiol. Immunol. 2010, 347 ( (Phosphoinositide 3-kinase in Health and Disease, Volume 2), ), 55–77.

The author declares no competing financial interest.