Search

Protein kinase CK2 is a potential drug target for many diseases including cancer and inflammation disorders. The crystal structure of clinical candidate CX-4945 1 with CK2 revealed an indirect interaction with the protein through hydrogen bonding between the NH of the 3-chlorophenyl amine and a water molecule. Herein, we investigate the relevance of this hydrogen bond by preparing several novel tricyclic derivatives lacking a NH moiety at the same position. This SAR study allowed the discovery of highly potent CK2 inhibitors.

In this article we describe the preclinical characterization of 5-(3-chlorophenylamino) benzo[c][2,6]naphthyridine-8-carboxylic acid (CX-4945), the first orally available small molecule inhibitor of protein CK2 in clinical trials for cancer. CX-4945 was optimized as an ATP-competitive inhibitor of the CK2 holoenzyme (Ki = 0.38 nM). Iterative synthesis and screening of analogs, guided by molecular modeling, led to the discovery of orally available CX-4945. CK2 promotes signaling in the Akt pathway and CX-4945 suppresses the phosphorylation of Akt as well as other key downstream mediators of the pathway such as p21. CX-4945 induced apoptosis and caused cell cycle arrest in cancer cells in vitro. CX-4945 exhibited a dose-dependent antitumor activity in a xenograft model of PC3 prostate cancer model and was well tolerated. In vivo time-dependent reduction in the phosphorylation of the biomarker p21 at T145 was observed by immunohistochemistry. Inhibition of the newly validated CK2 target by CX-4945 represents a fresh therapeutic strategy for cancer.

A novel and efficient synthesis of 5-oxo-6-carboxy-naphthyridines is reported in this Letter along with a discussion of scope and limitations. Activated 3-nicotinic acids readily acylate the magnesium anion of 2-(benzothiazol-2-yl) or 2-(benzimidazol-2-yl) acetates. The corresponding product can then undergo cyclization spontaneously or under very mild conditions to give the desired naphthyridine products. Only near stoichiometric ratios of reactants are required for this approach and the products are isolated in pure form after a trituration making this an efficient process.

This letter details the attenuation of hERG in a class of Akt inhibitors through heteroatom insertions into aromatic rings. The development of a cell-active dual Akt 1 and 2 inhibitors devoid of hERG activity is discussed using structure-activity relationships.

The enantioselective syntheses of naphthyl-substituted-N-tosylphenylglycines are described. These unnatural amino acids were tested as ligands for the chiral oxazaborolidine catalyzed Diels-Alder reaction between cyclopentadiene and 2-bromoacrolein.

Secondary and tertiary amides were treated with trifluoromethanesulfonic (triflic) anhydride in the presence of pyridine at low temperatures to generate imino and iminium triflates. Subsequent treatment with hydrogen sulfide immediately gave rise to the corresponding thioamide in good to excellent yields at low temperature. Alternatively, treatment with stoichiometric amounts of 18O-labeled water produced the 18O-labeled amide.

Secondary and tertiary amides were treated with trifluoromethanesulfonic (triflic) anhydride in the presence of pyridine at low temperatures to generate imino and iminium triflates. Successive treatment with 2,2-bishydroxymethyl-1-propanol in the pyridine buffered solution gave the corresponding 2,6,7-trioxabicyclo[2.2.2]octane orthoesters in good to excellent yields at below room temperature.

Tumour hypoxia presents a barrier to conventional chemotherapy and radiation therapy. To combat hypoxic cells a number of hypoxia modifying treatments are currently in development. In this study we assessed the potential for inhibiting DNA double strand break repair in hypoxic cells by targeting DNA-dependent protein kinase (DNA-PK) and we report the synthesis and in vitro efficacy of BCCA621C (1), a hypoxia activated inhibitor of DNA-PK. We found that DNA-PK deficient hypoxic cells are radiosensitive compared to hypoxic DNA-PK proficient cells and that this effect can be observed using both a small molecule inhibitor of DNA- PK, IC86621 (2), as well as with a genetically deficient model cell line. BCCA621C, which is designed to selectively release a DNA-PK inhibitor in hypoxic cells was synthesized and assessed for bioreduction using mouse liver microsomes and NCI-H460 cells. BCCA621C is activated by bioreduction in severely hypoxic NCI-H460 cells and was able to radiosensitize hypoxic NCI-H460 cells with a sensitizer enhancement ratio (SER) of 1.85. No enhancement of radiosensitivity was found to occur with BCCA621C treatment in oxygenated NCI-H460 cells in a range of clinically relevant ionizing radiation doses.

RXDX-107 is a dodecanol alkyl ester of bendamustine, which is then encapsulated in human serum albumin (HSA) to form nanoparticles. Bendamustine is an alkylating agent that induces interstrand DNA crosslinks (ICLs) and causes cell death via several pathways, including intrinsic apoptosis. The activity of bendamustine in the treatment of solid tumor malignancies has not been impressive, possibly due to the pharmacokinetic and limited biodistribution properties of bendamustine. RXDX-107 was designed to improve tissue biodistribution over bendamustine, which may result in superior efficacy and tolerability in patients with solid tumors. In preclinical studies, RXDX-107 displayed significant anti-tumor activity in multiple solid tumor cell lines, cell line-derived xenograft (CDX) and patient-derived xenograft (PDX) models of advanced solid tumors, such as breast, lung, and ovarian cancer. In this study, we further evaluated the mechanism of action of RXDX-107, particularly the means of entry and accumulation of drug into tumor cells. We have developed a novel analytical method to precisely quantify both dodecanol alkyl ester of bendamustine and released bendamustine in tissue culture medium and cells. Our data demonstrate that RXDX-107 is transported into cells in three active forms. Firstly, RXDX-107 slowly releases bendamustine into the extracellular medium, and released bendamustine then enters into cells. Secondly, the dodecanol alkyl ester of bendamustine is transported into cells and causes ICLs. And lastly, by measuring macropinocytosis, we also determined that human serum albumin nanoparticles mediate the intracellular entry of RXDX-107. Each of these mechanisms results in the formation of ICLs. In addition, comet assay data demonstrate that RXDX-107 displayed stronger induction of ICLs than bendamustine, and the induced ICLs persist over 48 hours in multiple solid tumor cell lines. Taken together, our data demonstrate that RXDX-107 enters and accumulates into cells via multiple mechanisms, and causes extensive and superior ICLs compared to bendamustine in several solid tumor cell lines, thereby providing a strong rationale for further investigation of this agent in solid tumor indications. Citation Format: Leenus Martin, Roopal Patel, Michael Johnson, Jerry Cao, Peter Chua, Colin Walsh, Jennifer Oliver, Pratik Multani, Robert Wild, Ralph Lin, Gary G. Li. RXDX-107 exhibits multiple mechanisms of intracellular delivery and results in extensive drug-induced interstrand crosslinks in solid tumor preclinical models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4780.

Herein we chronicle the discovery of CX-4945 (25n), a first-in-class, orally bioavailable ATP-competitive inhibitor of protein kinase CK2 in clinical trials for cancer. CK2 has long been considered a prime cancer drug target because of the roles of deregulated and overexpressed CK2 in cancer-promoting prosurvival and antiapoptotic pathways. These biological properties as well as the suitability of CK2's small ATP binding site for the design of selective inhibitors, led us to fashion novel therapeutic agents for cancer. The optimization leading to 25n (K(i) = 0.38 nM) was guided by molecular modeling, suggesting a strong binding of 25n resulting from a combination of hydrophobic interactions, an ionic bridge with Lys68, and hydrogen bonding with the hinge region. 25n was found to be highly selective, orally bioavailable across species (20-51%) and efficacious in xenograft models. The discovery of 25n will allow the therapeutic targeting of CK2 in humans for the first time.

Malignant transformation and maintenance of the malignant phenotype depends on oncogenic and non-oncogenic proteins that are essential to mediate oncogene signaling and to support the altered physiologic demands induced by transformation. Protein kinase CK2 supports key prosurvival signaling pathways and represents a prototypical non-oncogene. In this study, we describe CX-4945, a potent and selective orally bioavailable small molecule inhibitor of CK2. The antiproliferative activity of CX-4945 against cancer cells correlated with expression levels of the CK2α catalytic subunit. Attenuation of PI3K/Akt signaling by CX-4945 was evidenced by dephosphorylation of Akt on the CK2-specific S129 site and the canonical S473 and T308 regulatory sites. CX-4945 caused cell-cycle arrest and selectively induced apoptosis in cancer cells relative to normal cells. In models of angiogenesis, CX-4945 inhibited human umbilical vein endothelial cell migration, tube formation, and blocked CK2-dependent hypoxia-induced factor 1 alpha (HIF-1α) transcription in cancer cells. When administered orally in murine xenograft models, CX-4945 was well tolerated and demonstrated robust antitumor activity with concomitant reductions of the mechanism-based biomarker phospho-p21 (T145). The observed antiproliferative and anti-angiogenic responses to CX-4945 in tumor cells and endothelial cells collectively illustrate that this compound exerts its antitumor effects through inhibition of CK2-dependent signaling in multiple pathways. Finally, CX-4945 is the first orally bioavailable small molecule inhibitor of CK2 to advance into human clinical trials, thereby paving the way for an entirely new class of targeted treatment for cancer. Cancer Res; 70(24); 10288–98. ©2010 AACR.

Secondary and tertiary amides were treated with trifluoromethanesulfonic (triflic) anhydride in the presence of pyridine at low temperatures to generate imino and iminium triflates. Successive treatment with 2,2-bishydroxymethyl-1-propanol in the pyridine buffered solution gave the corresponding 2,6,7-trioxabicyclo[2.2.2]octane orthoesters in good to excellent yields at below room temperature.

Secondary and tertiary amides were treated with trifluoromethanesulfonic (triflic) anhydride in the presence of pyridine at low temperatures to generate imino and iminium triflates. Subsequent treatment with hydrogen sulfide immediately gave rise to the corresponding thioamide in good to excellent yields at low temperature. Alternatively, treatment with stoichiometric amounts of 18O-labeled water produced the 18O-labeled amide.

A novel and efficient synthesis of 5-oxo-6-carboxy-naphthyridines is reported in this Letter along with a discussion of scope and limitations. Activated 3-nicotinic acids readily acylate the magnesium anion of 2-(benzothiazol-2-yl) or 2-(benzimidazol-2-yl) acetates. The corresponding product can then undergo cyclization spontaneously or under very mild conditions to give the desired naphthyridine products. Only near stoichiometric ratios of reactants are required for this approach and the products are isolated in pure form after a trituration making this an efficient process.

Structure-activity relationship studies leading to the discovery of novel mGlu5 receptor antagonists are described. These compounds show high in vitro potency, have good in vivo receptor occupancy, and a reasonable intravenous pharmacokinetic profile.

Pyrimidine methyl anilines as potent and selective mGlu2 potentiators are described. Findings from the structure-activity-relationship investigations are discussed.