A novel B-RAF inhibitor blocks interleukin-8 (IL-8) synthesis in human melanoma xenografts, revealing IL-8 as a potential pharmacodynamic biomarker.

B-RAF mutations have been identified in the majority of melanoma and a large fraction of colorectal and papillary thyroid carcinoma. Drug discovery efforts targeting mutated B-RAF have yielded several interesting molecules, and currently, three compounds are undergoing clinical evaluation. Inhibition of B-RAF in animal models leads to a slowing of tumor growth and, in some cases, tumor reduction. Described within is a novel series of diaryl imidazoles with potent, single-digit nanomolar, anti-B-RAF activity. One compound from this series has been detailed here and has been shown to block B-RAF(V600E)-dependent extracellular signal-regulated kinase 1/2 phosphorylation in SK-MEL-28 melanoma cells as well as soft agar colony formation and proliferation. Importantly, interleukin-8 (IL-8) was identified by quantitative real-time PCR and ELISA as a product of the elevated mitogen-activated protein kinase signaling in these cells. Plasma concentrations of IL-8 in mice bearing melanoma xenografts were significantly reduced following exposure to B-RAF inhibitors. Taken together, these data suggest that IL-8 could serve as a tractable clinical biomarker.

Dual binding site inhibitors of B-RAF kinase.

Computer aided modeling guided the design of a series of diarylimidazole compounds (11-22) intended to interact with both the ATP and adjacent allosteric binding domains of B-RAF kinase. Their ability to inhibit the function of B-RAF kinase and intracellular ERK1/2 phosphorylation were evaluated.

2-Aryl benzimidazoles featuring alkyl-linked pendant alcohols and amines as inhibitors of checkpoint kinase Chk2.

A series of benzimidazole compounds containing pendant alcohol and amine moieties was found to be active against checkpoint kinase Chk2. These compounds were prepared to examine a potential hydrogen bond interaction with an active site residue and to investigate replacement of a biaryl linker with an aliphatic system in an effort to improve solubility.

Checkpoint kinase inhibitors: SAR and radioprotective properties of a series of 2-arylbenzimidazoles.

The discovery of a series of novel, potent, and highly selective inhibitors of the DNA damage control kinase chk2 is disclosed. Here we report the first SAR study around inhibitors of this kinase. High-throughput screening of purified human chk2 led to the identification of a novel series of 2-arylbenzimidazole inhibitors of the kinase. Optimization was facilitated using homology models of chk2 and docking of inhibitors, leading to the highly potent 2-arylbenzimidazole 2h (IC(50) 15 nM). Compound 2h is an ATP-competitive inhibitor of chk2 that dose dependently protects human CD4(+) and CD8(+) T-cells from apoptosis due to ionizing radiation. This work suggests that a selective small molecule inhibitor of chk2 could be a useful adjuvant to radiotherapy, increasing the therapeutic window of such treatment.

Novel non-benzimidazole chk2 kinase inhibitors.

In a recent paper, [Arienti, K. L.; Brunmark, A.; Axe, F. U.; McClure, K. M.; Lee, A.; Blevitt, J.; Neff, D. K.; Huang, L.; Crawford, S.; Chennagiri, R. P.; Karlsson, L.; Brietenbucher, J. G. J. Med. Chem.2005, 48, 1873], we described the discovery of a class of benzimidazole chk2 kinase inhibitors, exemplified by compound 1, which had radio-protective effects in human T-cells subjected to ionizing radiation. Here, a series of non-benzimidazole analogs intended to define the scope of the SAR about this new series of inhibitor, and allow for refinement of the binding model of these compounds to the chk2 kinase is described.

Early antigen-specific response by naive CD8 T cells is not altered with aging.

Both a dramatic decline in CD8 responses and a switch to memory T cell predominance occur with aging. The extent to which the loss of responsiveness is the consequence of the accumulation of more differentiated vs intrinsically defective T cells (or both) has been unclear. Using similar conditions of Ag stimulation, we have examined the responses generated by CD8(+) cells isolated from aged TCR transgenic mice. We found that the naive transgene(+) CD8(+) cells from aged 2C mice expressed activation markers, produced IL-2, proliferated, and differentiated into cytotoxic T cells as efficiently as their young counterparts. The extent of responsiveness and the level of the responses were comparable in both age groups regardless of the stimulatory conditions used, i.e., partial costimulation/adhesion molecule expression on APCs, or presentation of lower affinity peptide or diminished peptide concentrations. By day 4 after Ag stimulation, no significant age-related differences were observed in the number of effector cells generated nor in the levels of secreted IL-2 or IFN-gamma. Upon restimulation of effector cells, IL-2 secretion and to a lesser extent TNF-alpha expression, but not IFN-gamma secretion, were diminished with age. These findings suggest that age-associated alterations in naive CD8 cell function are not found after primary stimulation, but may become apparent upon restimulation.