CYC-116 is a novel, ATP-competitive, pyrimidine drug that is taken by mouth as a capsule. The drug is a selective agent that potently inhibits the enzymes Aurora kinases and VEGFR-2 kinase at comparable levels with a range of 19 to 69 nanomolar. Median potency of CYC-116 in cancer cells is approximately 300 nanomolar. CYC-116 has demonstrated a broad spectrum of potent cytotoxic activity against human tumor cell types. Non-clinical efficacy of CYC-116 has been demonstrated by the oral route using mouse leukemia models, in which increased survival was observed, and human solid tumor xenograft models, in which reductions in tumor growth were observed. Cancer cell types that appear to be particularly sensitive to CYC-116 are leukemia, non-small cell lung cancer and pancreatic cancer. CYC-116 works by affecting the cell cycle progression of cancer cells before they enter mitosis or divide to create daughter cancer cells. The mechanism of action of CYC-116 affects cancer cells in several ways. CYC-116-treated cells display delayed entry into mitosis; defective polymerization of tubulins, or proteins that make up microtubules which are the target of the taxane drugs; changes in the function of the centrosome, or the cell's microtubule organizing center; and formation of the mitotic spindle, or the highway along which chromosomes and cellular materials are transported from the mother cell to the daughter cells. After cancer cells are treated with CYC-116, their spindle checkpoint is inactivated resulting in inhibition of cytokinesis or the process by which a mother cell divides. These defects result in the generation of polyploidy or cells with more than two chromosome sets, multinucleated cells or cells with multiple cores and apoptosis or cancer cell death. In a mouse model of leukemia CYC116-treatment induced decreases in tumor cell volume and infiltration of leukemic cells in the bone marrow and resulted in an increase in life span. No significant effects on body weight or normal bone marrow cells were observed at effective doses of CYC-116. Tumor neovascularization, or creation of new blood vessels around a tumor, was significantly reduced in a dose dependent manner. The data confirm that CYC-116 acts as a dual mitotic and angiogenesis inhibitor, a combination of anti-cancer mechanisms which could have therapeutic benefit in the clinic. CYC-116 is currently being studied in a Phase 1 trial in patients with solid tumors at Roswell Park Cancer Institute in Buffalo, New York, and South Texas Accelerated Research Therapeutics (START) in San Antonio. The study is designed to identify the maximum tolerated dose of CYC-116 and evaluate its pharmacokinetic, pharmacodynamic and anti-tumor effects.

Pfizer's CP-547632 is a selective inhibitor of VEGFR-2 tyrosine kinase that was discovered during Pfizer's collaboration with OSI Pharmaceuticals. CP-547632, was identified as a potent inhibitor of the VEGFR-2 and basic fibroblast growth factor (FGF) kinases (IC(50) = 11 and 9 nM, respectively). It is selective relative to epidermal growth factor receptor, platelet-derived growth factor beta, and other related TKs. It also inhibits VEGF-stimulated autophosphorylation of VEGFR-2 in a whole cell assay with an IC(50) value of 6 nM. After oral administration of CP-547632 to mice bearing NIH3T3/H-ras tumors, VEGFR-2 phosphorylation in tumors was inhibited in a dose-dependent fashion (EC(50) = 590 ng/ml). CP-547,632 is a well-tolerated, orally-bioavailable inhibitor presently under clinical investigation for the treatment of human malignancies. CP-547632 is in phase I for the treatment of diabetic retinopathy and age-related macular degeneration.

R1530 is the multikinase inhibitor with potential antiangiogenesis and antineoplastic activities. R1530 is also a mitosis-angiogenesis inhibitor (MAI) that inhibits multiple receptor tyrosine kinases involved in angiogenesis, such as vascular endothelial growth factor receptor (VEGFR)-1, -2, -3, platelet-derived growth factor receptor (PDGFR) beta, FMS-like tyrosine kinase (Flt)-3, and fibroblast growth factor receptor (FGFR) -1, -2. In addition, this agent exhibits anti-proliferative activity by initiating mitotic arrest and inducing apoptosis. In the presence of R1530, polyploid cancer cells underwent apoptosis or became senescent which translated into potent in vitro and in vivo efficacy. Normal proliferating cells were resistant to R1530-induced polyploidy thus supporting the rationale for cancer therapy by induced polyploidy. Mitotic checkpoint kinase BubR1 was found downregulated during R1530-induced exit from mitosis, a likely consequence of PLK4 inhibition. R1530 strongly inhibited human tumor cell proliferation and growth factor-driven proliferation of endothelial and fibroblast cells. Significant tumor growth inhibition was demonstrated in a lung cancer xenograft model with a range of once daily, weekly and twice-weekly doses of R1530. Daily doses were most effective in the lung cancer model and also had significant growth inhibitory effects in models of colorectal, prostate, and breast tumors. Tumor regression occurred in all models treated with the maximum tolerated daily dose. The doses of 25 and 50 mg/kg QD resulted in biologically significant increased survival in all tested models. After oral administration in nude mice, R1530 showed good tissue penetration. R1530 had been in phase I clinical trials by Hoffmann-La Roche, Inc. for the treatment of advanced solid tumors. However, the clinical development of R1530 was discontinued.

BMS-794833 (N-(4-(2-Amino-3-chloropyridin-4-yloxy)-3-fluorophenyl)-5-(4- fluorophenyl)-4-oxo-l,4-dihydropyridine-3-carboxamide) is an inhibitor of Met, VEGFR2, Ron, Axl and Flt-3 kinases. BMS-794833 demonstrated dose-dependent tumor growth inhibition following oral administration in xenograft models. In cell culture, BMS-794833 inhibited the proliferation of human tumor cell lines containing constitutively activated Met receptor. BMS-794833 is an active moety of pro-drug BMS-817378. Bristol-Myers Squibb and Simcere Pharmaceutical Group are developing BMS-817378 for treatment of cancer.

AAL993 (ZK260253) is a potent and selective VEGF receptor kinase (VEGF-R) tyrosine kinase inhibitor (VEGFR2), which binds to an inactive conformation of the protein. In addition, AAL993 possesses dual functions, including suppression of HIF-1 alpha expression through ERK inhibition without affecting Akt phosphorylation.

AST-487 is an inhibitor of RET (IC50 = 0.88 uM), FLT3 (Ki = 0.52 uM), KDR (IC50 = 0.17 uM), c-Abl (IC50 = 0.02 uM), and c-Kit (IC50 = 0.5 uM). AST-487 has potent and selective antiproliferative effects 7 on primary AML patient cells and cell lines expressing FLT3-ITD or FLT3 kinase domain point mutants. AST-487, which selectively targets mutant FLT3 protein kinase activity, is also shown to override PKC412 resistance in vitro, and has significant antileukemic activity in an in vivo model of FLT3-ITD(+) leukemia. Finally, the combination of NVP-AST487 with standard chemotherapeutic agents leads to enhanced inhibition of proliferation of mutant FLT3-expressing cells. AST-487 displays high selectivity and potency toward FLT3 as a molecular target, and could potentially be used to override drug resistance in AML.