The design and synthesis of a novel series of 2,6-disubstituted pyrazine derivatives as CK2 kinase inhibitors is described. Structure-guided optimization of a 5-substituted-3-thiophene carboxylic acid screening hit (3a) led to the development of a lead compound (12b), which shows inhibition in both enzymatic and cellular assays. Subsequent design and hybridization efforts also led to the unexpected identification of analogs with potent PIM kinase activity (14f).

In this letter, we describe the design, synthesis, and structure-activity relationship of 5-anilinopyrazolo[1,5-a]pyrimidine inhibitors of CK2 kinase. Property-based optimization of early leads using the 7-oxetan-3-yl amino group led to a series of matched molecular pairs with lower lipophilicity, decreased affinity for human plasma proteins, and reduced binding to the hERG ion channel. Agents in this study were shown to modulate pAKT(S129), a direct substrate of CK2, in vitro and in vivo, and exhibited tumor growth inhibition when administered orally in a murine DLD-1 xenograft.

Abstract Casein Kinase 2 (CK2) is an abundant, highly conserved protein serine/threonine kinase with numerous physiological targets and participates in the maintenance of cell viability with a role in cell growth and proliferation. While the expression level of CK2 in normal cells is tightly regulated, there is an increasing body of evidence demonstrating it's over expression in cancerous cells, thereby making inhibition a viable chemotherapeutic target. Here we will describe a mathematical tumor growth inhibition model describing the relationship between systemic exposure to a potent inhibitor of CK2 (AZ285) and efficacy in the HCT116 xenograft model. Furthermore, a PK/PD model describing the onset, intensity, and duration of the pAKT and cleaved caspase 3 response as function of concentration and time is described and linked to pre-clinical xenograft efficacy outcomes. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3770. doi:1538-7445.AM2012-3770

In this paper we describe a series of 3-cyano-5-aryl-7-aminopyrazolo[1,5-a]pyrimidine hits identified by kinase-focused subset screening as starting points for the structure-based design of conformationally constrained 6-acetamido-indole inhibitors of CK2. The synthesis, SAR, and effects of this novel series on Akt signaling and cell proliferation in vitro are described.

Abstract Casein Kinase 2 (CK2) is a highly conserved and ubiquitously expressed serine/threonine kinase that regulates several key oncogenic signaling pathways, including PI3K/AKT, and NFkB and Wnt, and whose targeted overexpression in transgenic animal models results in neoplastic growth. Herein we describe the identification of AZ285, a potent pyrazolo[1,5-a]pyrimidine-derived inhibitor of CK2 with a high degree of kinase selectivity. AZ285 depletes levels of the CK2 substrates pAKTS129 and PTENS370 and induces apoptosis in cells in a concentration-dependent manner. Optimization of early leads was aided in part by cell wash-out experiments and X-ray cocrystallography with huCK2a and resulted in an agent with physical properties and DMPK characteristics suitable for evaluation in disease model studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3907. doi:1538-7445.AM2012-3907