Alan J. Kraker

Biochemical and cellular effects of c-Src kinase-selective pyrido[2,3-d]pyrimidine tyrosine kinase inhibitors

Increased expression or activity of c-Src tyrosine kinase has been associated with the transformed phenotype in tumor cells and with progression of neoplastic disease. A number of pyrido[2, 3-d]pyrimidines have been characterized biochemically and in cells as part of an assessment of their potential as anti-tumor agents. The compounds were ATP-competitive inhibitors of c-Src kinase with IC(50) values < 10 nM and from 6 to >100-fold selectivity for c-Src tyrosine kinase relative to basic fibroblast growth factor receptor (bFGFr) tyrosine kinase, platelet-derived growth factor receptor (PDGFr) tyrosine kinase, and epidermal growth factor receptor (EGFr) tyrosine kinase. The compounds yielded IC(50) values < 5 nM against Lck. Human colon tumor cell growth in culture was inhibited, as was colony formation in soft agar at concentrations < 1 microM. Phosphorylation of the c-Src cellular substrates paxillin, p130(cas), and Stat3 was also inhibited at concentrations < 1 microM. Autophosphorylation of EGFr tyrosine kinase or PDGFr tyrosine kinase was not inhibited by c-Src inhibitors, thus showing the selective nature of the compounds in cells. In a mitogenesis assay measuring thymidine incorporation stimulated by specific mitogens, the c-Src tyrosine kinase inhibitors reduced incorporated thymidine in a manner consistent with previously reported roles of c-Src in mitogenic signaling. Progression through the cell cycle was inhibited at G(2)/M in human colon tumor cells treated with two of the c-Src-selective compounds, which is also consistent with earlier reports describing a requirement for active c-Src tyrosine kinase for G(2) to M phase progression. The compounds described here are selective inhibitors of c-Src tyrosine kinase and have antiproliferative effects in tumor cells consistent with inhibition of c-Src.

discovery and structure-activity studies of a novel series of pyrido[2,3-d]pyrimidine tyrosine kinase inhibitors

Abstract The inhibition of tyrosine kinase-mediated signal transduction pathways represents a therapeutic approach to the intervention of proliferative diseases such as cancer, atherosclerosis, and restenosis. A novel series of pyrido[2,3-d]pyrimidine inhibitors of the PDGFr, bFGFr, and c-Src tyrosine kinases was developed from compound library screening and lead optimization.1 In addition, highly selective inhibitors of the FGFr tyrosine kinase were also discovered and developed from this novel series of pyrido[2,3-d]pyrimidines. The syntheses, biological evaluation, and structure-activity relationships of this series are reported.

SMALL MOLECULE INHIBITORS OF THE PLATELET-DERIVED GROWTH FACTOR RECEPTOR, THE FIBROBLAST GROWTH FACTOR RECEPTOR, AND SRC FAMILY TYROSINE KINASES

The inhibition of tyrosine kinases involved in growth factor signal transduction pathways represents an attractive strategy for controlling aberrant cellular growth. Over the last 4-5 years, there have been numerous reports on the discovery of small molecule inhibitors for potential therapeutic applications to a number of proliferative diseases, principally cancer and restenosis, where the over-expression of certain tyrosine kinases has been demonstrated. These include, amongst others, the platelet-derived growth factor receptor, the fibroblast growth factor receptor, and the nonreceptor c-Src tyrosine kinase. This review compiles published reports and patent filings from 1995 to mid-1997 that include data directly related to inhibition of the platelet-derived growth factor receptor, fibroblast growth factor receptor, and Src family tyrosine kinases. Potential clinical applications for selected classes of tyrosine kinase inhibitors reviewed herein will likely depend on the demonstration of meaningful activity in a variety of therapeutic targets in animal models.

Elevated DNA polymerase beta activity in a cis-diamminedichloroplatinum(II) resistant P388 murine leukemia cell line

The activity of DNA polymerase beta, which is an enzyme involved in repair of DNA damage, was assessed in P388 murine leukemia cell lines sensitive and resistant to cis-diamminedichloroplatinum(II) (cis-Pt). The resistant line was selected with cis-Pt and showed cross-resistance to a number of alkylating agents, but not to an anthracycline. The DNA polymerase beta activity was found to be elevated 5-fold in the resistant line based upon activity per mg cell protein and elevated 4-fold based upon activity per 10(7) cells. The characterization of elevated activity of an enzyme active in DNA repair in a cell line resistant to DNA damaging agents describes a possible mechanism of resistance in addition to those previously found.

STRUCTURE-ACTIVITY RELATIONSHIPS FOR 4-ANILINOQUINAZOLINES AS POTENT INHIBITORS AT THE ATP BINDING SITE OF THE EPIDERMAL GROWTH FACTOR RECEPTOR IN VITRO

1. Structure‐activity relationships are described for the inhibition of the tyrosine kinase activity (phosphorylation of a fragment of phospholipase Cg1) of the epidermal growth factor receptor (EGFR) by 4‐anilinoquinazolines. These compounds are competitive inhibitors at the ATP binding site.

1-oxo-3-aryl-1H-indene-2-carboxylic acid derivatives as selective inhibitors of fibroblast growth factor receptor-1 tyrosine kinase

Abstract Fibroblast growth factor receptor (FGFr) mediated signal transduction is implicated in vascular proliferative diseases and some cancers. We have identified methyl 1-oxo-3-phenyl-1H-indene-2-carboxylic ester as a small molecule inhibitor of the tyrosine kinase activity of FGFr-1, (IC50 = 5.1 μM). We report here the synthesis and structure-activity studies about this template core. Additionally, screening of this series against a panel of tyrosine kinases shows selective inhibition of FGFr.

Preclinical antitumor activity of CI-973,[SP-4-3-(R)]-[1,1- cyclobutanedicarboxylato(2-)](2 methyl-1,4-butane-diamine-N,N')platinum.

SummaryThe antitumor activity of [SP-4-3-(R)]-[1,1-cyclobutanedicarboxylato-(2-)](2 methyl-1,4-butanediamine-N,N′)platinum (CI-973) was characterized in a number of preclinical model systems. CI-973 retained substantial activity in cisplatin resistant murine leukemia cell lines, in vitro and in vivo; in L1210 leukemia resistant to cisplatin in vivo, CI-973 retained as much activity as was found in animals bearing sensitive L1210 leukemia. When compared in five solid murine tumors in vivo, both CI-973 and cisplatin were approximately equivalent in activity. In one human colon tumor and one human non-small cell lung carcinoma tested as xenografts in immunodeficient mice, cisplatin and CI-973 were ineffective. In two other human non-small cell lung carcinomas tested in the same fashion, cisplatin did possess activity. CI-973 has entered phase I clinical trials.

Chapter 25. New Targets in Cell Cycle Regulation

Publisher Summary This chapter explores new targets in cell cycle regulation. A better understanding of the mechanistic events that regulate cell cycle progression and cell replication has provided targets for the discovery of novel therapeutic agents for the treatment of diseases that result from uncontrolled cell proliferation. Enhanced ability to modulate the signaling and regulatory pathways may lead to a greater understanding of cell cycle progression and to valuable advances in clinical care. Cell cycle progression can be viewed as a sequence of events that are regulated by a cascade of protein kinases that are controlled by four known mechanisms: protein–protein interactions, phosphorylation, intracellular sequestration, and proteolytic degradation of the kinase or its regulatory components. Of the four regulatory mechanisms, those involving enzyme catalysis are the subject of the chapter because small molecule inhibitors remain the focus of most approaches to therapeutic intervention. Two small molecule inhibitors of Cdks, flavopiridol and UCN-01, have progressed into clinical trials and are highlighted in the chapter. The emphasis is on molecules that regulate the G2/M transition and M phase progression.