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Small-molecule inhibitors that target bromodomains outside of the bromodomain and extra-terminal (BET) sub-family are lacking. Here, we describe highly potent and selective ligands for the bromodomain module of the human lysine acetyl transferase CBP/p300, developed from a series of 5-isoxazolyl-benzimidazoles. Our starting point was a fragment hit, which was optimized into a more potent and selective lead using parallel synthesis employing Suzuki couplings, benzimidazole-forming reactions, and reductive aminations. The selectivity of the lead compound against other bromodomain family members was investigated using a thermal stability assay, which revealed some inhibition of the structurally related BET family members. To address the BET selectivity issue, X-ray crystal structures of the lead compound bound to the CREB binding protein (CBP) and the first bromodomain of BRD4 (BRD4(l)) were used to guide the design of more selective compounds. The crystal structures obtained revealed two distinct binding modes. By varying the aryl substitution pattern and developing conformationally constrained analogues, selectivity for CBP over BRD4(l) was increased. The optimized compound is highly potent (Kd = 21 nM) and selective, displaying 40-fold selectivity over BRD4(l). Cellular activity was demonstrated using fluorescence recovery after photo-bleaching (FRAP) and a p53 reporter assay. The optimized compounds are cell-active and have nanomolar affinity for CBP/p300; therefore, they should be useful in studies investigating the biological roles of CBP and p300 and to validate the CBP and p300 bromodomains as therapeutic targets. [ABSTRACT FROM AUTHOR]

Silicone wristbands present a noninvasive exposure assessment tool and an alternative to traditional biomonitoring; however, questions about their utility remain as validation studies are limited. We sought to determine if wristbands provide quantitative estimates of internal organophosphate ester (OPE) exposure. We evaluated internal dose by measuring metabolite masses excreted in 24-hour urine samples collected over five days among ten adults. We compared internal dose to OPE concentrations in paired wristbands worn during collection and, as a comparison, evaluated metabolite levels in spot urine samples. Three of six OPE metabolites evaluated were detected in >98% of urine samples, and 24 of 34 assessed OPEs were detected in at least one wristband. OPE uptake in wristbands was linear over time (range=0.54-61.8 ng/g/day). OPE concentrations in spot urine and wristbands were not correlated with total diphenyl phosphate (DPHP) excreted in urine, which may be due to the range of possible DPHP parent compounds or dietary exposure. However, for tris-(1,3-dichloro-2-propyl)phosphate (TDCIPP) and tris-(2-chloroisopropyl)phosphate (TCIPP), wristbands and spot urine samples were both moderately to strongly correlated with internal dose (all r s >0.56 and p<0.1), suggesting both perform well as integrated exposure estimates. Given the potential advantages of silicone wristbands, further studies investigating additional compounds are warranted.

Bromodomains, protein modules that recognize and bind to acetylated lysine, are emerging as important components of cellular machinery. These acetyl-lysine (KAc) "reader" domains are part of the write-read-erase concept that has been linked with the transfer of epigenetic information. By reading KAc marks on histones, bromodomains mediate protein-protein interactions between a diverse array of partners. There has been intense activity in developing potent and selective small molecule probes that disrupt the interaction between a given bromodomain and KAc. Rapid success has been achieved with the BET family of bromodomains, and a number of potent and selective probes have been reported. These compounds have enabled linking of the BET bromodomains with diseases, including cancer and inflammation, suggesting that bromodomains are druggable targets. Herein, we review the biology of the bromodomains and discuss the SAR for the existing small molecule probes. The biology that has been enabled by these compounds is summarized.