The phosphoinositide 3-kinase family catalyzes the phosphorylation of phosphatidylinositol-4,5-diphosphate to phosphatidylinositol-3,4,5-triphosphate, a secondary messenger which plays a critical role in important cellular functions such as metabolism, cell growth, and cell survival. Our efforts to identify potent, efficacious, and orally available phosphatidylinositol 3-kinase (PI3K) inhibitors as potential cancer therapeutics have resulted in the discovery of 4-(2-((6-methoxypyridin-3-yl)amino)-5-((4-(methylsulfonyl)piperazin-1-yl)methyl)pyridin-3-yl)-6-methyl-1,3,5-triazin-2-amine (1). In this paper, we describe the optimization of compound 1, which led to the design and synthesis of pyridyltriazine 31, a potent pan inhibitor of class I PI3Ks with a superior pharmacokinetic profile. Compound 31 was shown to potently block the targeted PI3K pathway in a mouse liver pharmacodynamic model and inhibit tumor growth in a U87 malignant glioma glioblastoma xenograft model. On the basis of its excellent in vivo efficacy and pharmacokinetic profile, compound 31 was selected for further evaluation as a clinical candidate and was designated AMG 511.

ABSTRACT:The identification of Pim-1/2 kinase overexpression in B-cell malignancies suggests that Pim kinase inhibitors will have utility in the treatment of lymphoma, leukemia, and multiple myeloma. Starting from a moderately potent quinoxalinedihydropyrrolopiperidinone lead, we recognized the potential for macrocyclization and developed a series of 13-membered macrocycles. The structure−activity relationships of the macrocyclic linker were systematically explored, leading to the identification of 9c as a potent, subnanomolar inhibitor of Pim-1 and -2. This molecule also potently inhibited Pim kinase activity in KMS-12-BM, a multiple myeloma cell line with relatively high endogenous levels of Pim-1/2, both in vitro (pBAD IC 50 = 25 nM) and in vivo (pBAD EC 50 = 30 nM, unbound), and a 100 mg/kg daily dose was found to completely arrest the growth of KMS-12-BM xenografts in mice.

The high expression of proviral insertion site of Moloney murine leukemia virus kinases (Pim-1, -2, and -3) in cancers, particularly the hematopoietic malignancies, is believed to play a role in promoting cell survival and proliferation while suppressing apoptosis. The three isoforms of Pim protein appear largely redundant in their oncogenic functions. Thus, a pan-Pim kinase inhibitor is highly desirable. However, cell active pan-Pim inhibitors have proven difficult to develop because Pim-2 has a low Km for ATP and therefore requires a very potent inhibitor to effectively block the kinase activity at cellular ATP concentrations. Herein, we report a series of quinazolinone-pyrrolopyrrolones as potent and selective pan-Pim inhibitors. In particular, compound 17 is orally efficacious in a mouse xenograft model (KMS-12 BM) of multiple myeloma, with 93% tumor growth inhibition at 50 mg/kg QD upon oral dosing.

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