Rosemary C. McFall

Synthesis and initial SAR studies of 3,6-disubstituted pyrazolo[1,5-a]pyrimidines: A new class of KDR kinase inhibitors

We have synthesized and evaluated the activity of 3,6-disubstituted pyrazolo[1,5-a]pyrimidines as a new class of KDR kinase inhibitors. Starting with screening lead 1, potency against isolated KDR was fully optimized with 3-thienyl and 4-methoxyphenyl substituents at the 6- and 3-positions (3g, KDR IC(50)=19 nM), respectively. The synthesis and SAR of these compounds are described.

Optimization of a pyrazolo[1,5-a]pyrimidine class of KDR kinase inhibitors: improvements in physical properties enhance cellular activity and pharmacokinetics.

We have introduced solubilizing functionality to a 3,6-disubstituted pyrazolo[1,5-a]pyrimidine series of KDR kinase inhibitors to improve the physical properties of these compounds. The addition of a basic side-chain to the 6-aryl ring, introduction of 3-pyridyl groups, and most significantly, incorporation of a 4-pyridinonyl substituent at the 6-position of the core are modifications that maintain and often enhance the intrinsic potency of this class of inhibitors. Moreover, the improvements in physical properties result in marked increases in cellular activity and more favorable pharmacokinetics in rats. The synthesis and SAR of these compounds are described.

Effects of Subtype-Selective and Balanced Angiotensin II Receptor Antagonists in a Porcine Coronary Artery Model of Vascular Restenosis

BACKGROUND Numerous studies have demonstrated the ability of angiotensin II (Ang II) receptor antagonists and angiotensin-converting enzyme (ACE) inhibitors to inhibit intimal hyperplasia after balloon dilation of noncoronary arteries in small-animal models, suggesting an important role for Ang II in the response to injury. Although ACE inhibitors have not been similarly effective in nonhuman coronary models or in human restenosis trials, questions remain regarding the efficacy ACE inhibitors against tissue ACE and the contributions of ACE-independent pathways of Ang II generation. Unlike ACE inhibitors, Ang II receptor antagonists have the potential to inhibit responses to Ang II independent of its biosynthetic origin. METHODS AND RESULTS In separate studies, three Ang II receptor antagonists, including AT1 selective (L-158,809), balanced AT1/AT2 (L-163,082), and AT2 selective (L-164,282) agents, were evaluated for their ability to inhibit vascular intimal thickening in a porcine coronary artery model of vascular injury. Preliminary studies in a rat carotid artery model revealed that constant infusion of L-158,809 (0.3 or 1.0 mg X kg-1 X d-1) reduced the neointimal cross-sectional area by up to 37% measured 14 days after balloon dilatation. In the porcine studies, animals were treated with vehicle or test compound beginning 2 days before and extending 28 days after experimental angioplasty. Left anterior descending, left circumflex, and/or right coronary arteries were injured by inflation of commercially available angioplasty balloons with placement of coiled metallic stents. Infusion of L-158,809 (1 mg X kg-1 X d-1), L-163,082 (1 mg X kg-1 X d-1), or L-164,282 (1.5 mg X kg-1 X d-1) in the study animals yielded plasma drug levels sufficient either to chronically block or, for L-164,282, to spare pressor responses to exogenous Ang II. Neither L-158,809, L-163,082, nor L-164,282 had statistically significant effects (P=.12, P=.75, and P=.48, respectively, compared with vehicle-treated controls) on neointimal thickness (normalized for degree of injury) measured by morphometric analysis at day 28 after angioplasty. CONCLUSIONS These findings indicate that chronic blockade of Ang II receptors by either site-selective or balanced AT1/AT2 antagonists is insufficient to inhibit intimal hyperplasia after experimental coronary vascular injury in the pig. The results further suggest that, unlike in the rat carotid artery, Ang II is not a major mediator of intimal thickening in the pig coronary artery.

Identification of biomarkers for tumor endothelial cell proliferation through gene expression profiling

Extensive efforts are under way to identify antiangiogenic therapies for the treatment of human cancers. Many proposed therapeutics target vascular endothelial growth factor (VEGF) or the kinase insert domain receptor (KDR/VEGF receptor-2/FLK-1), the mitogenic VEGF receptor tyrosine kinase expressed by endothelial cells. Inhibition of KDR catalytic activity blocks tumor neoangiogenesis, reduces vascular permeability, and, in animal models, inhibits tumor growth and metastasis. Using a gene expression profiling strategy in rat tumor models, we identified a set of six genes that are selectively overexpressed in tumor endothelial cells relative to tumor cells and whose pattern of expression correlates with the rate of tumor endothelial cell proliferation. In addition to being potential targets for antiangiogenesis tumor therapy, the expression patterns of these genes or their protein products may aid the development of pharmacodynamic assays for small molecule inhibitors of the KDR kinase in human tumors.

Property-based design of KDR kinase inhibitors.

Small molecule inhibitors of KDR kinase activity have typically possessed poor intrinsic physical properties including low aqueous solubility and high lipophilicity. These features have often conferred limited cell permeability manifested in low levels of cell-based KDR inhibitory activity and oral bioavailability. Thus, the design of inhibitors with appropriate physical properties has played a critical role in the development of clinical candidates. We present a variety of structural modifications that have afforded improvements in physical properties and thereby have addressed suboptimal cellular potency and pharmacokinetics for three unique classes of KDR kinase inhibitors.

2,4-disubstituted pyrimidines: a novel class of KDR kinase inhibitors.

2,4-Disubstituted pyrimidines were synthesized as a novel class of KDR kinase inhibitors. Evaluation of the SAR of the screening lead compound 1 (KDR IC(50)=105 nM, Cell IC(50)=8% inhibition at 500 nM) led to the potent 3,5-dimethylaniline derivative 2d (KDR IC(50)=6 nM, cell IC(50)=19 nM).

Design and synthesis of 1,5-diarylbenzimidazoles as inhibitors of the VEGF-receptor KDR

1,5-Diarylbenzimidazoles have been identified as potent inhibitors of KDR kinase activity. The series was developed with a goal of finding compounds with optimal drug-like properties. This communication describes structural modifications in the series that enhance solubility, lower protein binding, and provide compounds with excellent potency and pharmacokinetic profiles.

Discovery and evaluation of 3-(5-Thien-3-ylpyridin-3-yl)-1H-indoles as a novel class of KDR kinase inhibitors

We have discovered 3-(5-thien-3-ylpyridin-3-yl)-1H-indoles as potent inhibitors of KDR kinase activity. This communication details the evolution of this novel class from a potent screening lead of vastly different structure with an emphasis on structural modifications that retained activity and provided improvements in key physical properties. The synthesis and in-depth evaluation of these inhibitors are described.

Immunohistochemical Detection of Antitumor, Antimetastasis, and Antiangiogenesis Effects of a Vascular Endothelial Growth Factor Receptor 2 Kinase Inhibitor in an Orthotopic Breast Cancer Metastasis Model

Abstract Antiangiogenic agents such as vascular endothelial growth factor receptor 2 (VEGFR2) inhibitors may prove most efficacious in the setting of early disease and in the prevention of dissemination and growth of micrometastases. This hypothesis was tested in a metastatic orthotopic rat model of breast cancer with the use of a novel orally bioavailable VEGFR2 kinase inhibitor, MK-0888. Mat B III rat mammary cancer cells were implanted into the mammary fat pads of syngeneic female F344 rats. Primary tumor growth was very aggressive, with micrometastases detected 8 days after cell implantation in ipsilateral axillary and inguinal lymph nodes. Lung metastases were detected 15 days after cell implantation by histological analysis. MK-0888 suppressed primary and metastatic tumor growth and reduced the incidence of metastasis in a dose- and schedule-dependent manner. Inhibitions of primary and metastatic tumor growth, as well as intratumoral antiangiogenesis effects, were detected in situ by immunohistochemical analysis of tumor cells, endothelial cell proliferation, microvascular density, and blood vessel maturity. In the Mat B III rat mammary cancer metastasis model, our results provide further evidence supporting the ongoing clinical development of VEGFR2 kinase inhibitors, as well as clinically applicable in situ detection and verification of the inhibitor effect in tumor and metastasis biopsies. (The J Histotechnol 33(1):15–24, 2010) Submitted November 20, 2009; accepted February 8, 2010.