␥-Secretase inhibitors are one promising approach to the development of a therapeutic for Alzheimer's disease (AD). ␥-Secretase inhibitors reduce brain ␤-amyloid peptide (A␤), which is believed to be a major contributor in the etiology of AD. Transgenic mice overexpressing the human ␤-amyloid precursor protein (APP) are valuable models to examine the dynamics of A␤ changes with ␥-secretase inhibitors in plaque-free and plaque-bearing animals. BMS-299897 2-[(1R)-1-[[(4-chlorophenyl)sulfony](2,5-difluorophenyl)amino]ethyl]-5-fluorobenzenepropanoic acid, a ␥-secretase inhibitor, showed doseand time dependent reductions of A␤ in brain, cerebrospinal fluid (CSF), and plasma in young transgenic mice, with a significant correlation between brain and CSF A␤ levels. Because CSF and brain interstitial fluid are distinct compartments in composition and location, this correlation could not be assumed. In contrast, aged transgenic mice with large accumulations of A␤ in plaques showed reductions in CSF A␤ in the absence of measurable changes in plaque A␤ in the brain after up to 2 weeks of treatment. Hence, CSF A␤ levels were a valuable measure of ␥-secretase activity in the central nervous system in either the presence or absence of plaques. Transgenic mice were also used to examine potential side effects due to Notch inhibition. BMS-299897 was 15-fold more effective at preventing the cleavage of APP than of Notch in vitro. No changes in the maturation of CD8ϩ thymocytes or of intestinal goblet cells were observed in mice treated with BMS-299897, showing that it is possible for ␥-secretase inhibitors to reduce brain A␤ without causing Notch-mediated toxicity.Diagnosis of AD is based on key pathological features at autopsy in the presence of dementia: loss of neuronal mass, intracellular tangles, and extracellular plaques. Plaques are composed predominantly of A␤. A␤ has both N-and C-terminal heterogeneity, with the C terminus usually ending at residues 40 or 42. Although A␤40 is 80 to 90% of the total, A␤42 is most associated with disease and is predominant in plaques. A␤ is produced by two cleavage events in APP (Wolfe, 2001). ␤-Secretase, now identified as ␤-site APP cleaving enzyme, makes the initial N-terminal cleavage, releasing a soluble N-terminal form of APP. The remaining, membrane-bound C-terminal fragment (CTF) of APP is cleaved by ␥-secretase to release soluble A␤ along with the APP intracellular domain. Alternatively, APP can This research was supported by Bristol-Myers Squibb and SIBIA Neurosciences, Inc.Article, publication date, and citation information can be found at

Compound 3 (BMS-536924), a novel small-molecule inhibitor of the insulin-like growth factor receptor kinase with equal potency against the insulin receptor is described. The in vitro and in vivo biological activity of this interesting compound is also reported.

ABSTRACT:The United States Public Health Service Administration is alerting medical professionals that a substantial percentage of cocaine imported into the United States is adulterated with levamisole, a veterinary pharmaceutical that can cause blood cell disorders such as severe neutropenia and agranulocytosis. Levamisole was previously approved in combination with fluorouracil for the treatment of colon cancer; however, the drug was withdrawn from the U.S. market in 2000 because of the frequent occurrence of agranulocytosis. The detection of autoantibodies such as antithrombin (lupus anticoagulant) and an increased risk of agranulocytosis in patients carrying the human leukocyte antigen B27 genotype suggest that toxicity is immune-mediated. In this perspective, we provide an historical account of the levamisole/cocaine story as it first surfaced in 2008, including a succinct review of levamisole pharmacology, pharmacokinetics, and preclinical/clinical evidence for levamisole-induced agranulocytosis. Based on the available information on levamisole metabolism in humans, we propose that reactive metabolite formation is the rate-limiting step in the etiology of agranulocytosis associated with levamisole, in a manner similar to other drugs (e.g., propylthiouracil, methimazole, captopril, etc.) associated with blood dyscrasias. Finally, considering the toxicity associated with levamisole, we propose that the 2,3,5,6-tetrahydroimidazo[2,1-b]thiazole scaffold found in levamisole be categorized as a new structural alert, which is to be avoided in drug design.

The reactive thiol of cysteine is often used for coupling maleimide-containing linker-payloads to antibodies resulting in the generation of antibody drug conjugates (ADCs). Currently, a numbers of ADCs in drug development are made by coupling a linker-payload to native or engineered cysteine residues on the antibody. An ADC conjugated via hinge-cysteines to an auristatin payload was used as a model in this study to understand the impact of the maleimide linkers on ADC stability. The payload was conjugated to trastuzumab by a protease-cleavable linker, maleimido-caproyl-valine-citruline-p-amino-benzyloxy carbonyl (mcVC-PABC). In plasma stability assays, when the ADC (Trastuzumab-mcVC-PABC-Auristatin-0101) was incubated with plasma over a 144-h time-course, a discrepancy was observed between the measured released free payload concentration and the measured loss of drug-to-antibody ratio (DAR), as measured by liquid chromatography-mass spectrometry (LC-MS). We found that an enzymatic release of payload from ADC-depleted human plasma at 144 h was able to account for almost 100% of the DAR loss. Intact protein mass analysis showed that at the 144 h time point, the mass of the major protein in ADC-depleted human plasma had an additional 1347 Da over the native albumin extracted from human plasma, exactly matching the mass of the linker-payload. In addition, protein gel electrophoresis showed that there was only one enriched protein in the 144 h ADC-depleted and antipayload immunoprecipitated plasma sample, as compared to the 0 h plasma immunoprecipitated sample, and the mass of this enriched protein was slightly heavier than the mass of serum albumin. Furthermore, the albumin adduct was also identified in 96 h and 168 h postdose in vivo cynomolgus monkey plasma. These results strongly suggest that the majority of the deconjugated mc-VC-PABC-auristatin ultimately is transferred to serum albumin, forming a long-lived albumin-linker-payload adduct. To our knowledge, this is the first report quantitatively characterizing the extent of linker-payload transfer to serum albumin and the first clear example of in vivo formation of an albumin-linker-payload adduct.

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