Inclusions comprised of fibrils of the microtubule- (MT-) associated protein tau are found in the brains of those with Alzheimer's disease (AD) and other neurodegenerative tauopathies. The pathology that is observed in these diseases is believed to result from the formation of toxic tau oligomers or fibrils and/or from the loss of normal tau function due to its sequestration into insoluble deposits. Hence, small molecules that prevent tau oligomerization and/or fibrillization might have therapeutic value. Indeed, examples of such compounds have been published, but nearly all have properties that render them unsuitable as drug candidates. For these reasons, we conducted quantitative high-throughput screening (qHTS) of approximately 292000 compounds to identify drug-like inhibitors of tau assembly. The fibrillization of a truncated tau fragment that contains four MT-binding domains was monitored in an assay that employed complementary thioflavin T fluorescence and fluorescence polarization methods. Previously described classes of inhibitors as well as new scaffolds were identified, including novel aminothienopyridazines (ATPZs). A number of ATPZ analogues were synthesized, and structure-activity relationships were defined. Further characterization of representative ATPZ compounds showed they do not interfere with tau-mediated MT assembly, and they are significantly more effective at preventing the fibrillization of tau than the Abeta(1-42) peptide which forms AD senile plaques. Thus, the ATPZ molecules described here represent a novel class of tau assembly inhibitors that merit further development for testing in animal models of AD-like tau pathology.

Epigenetic regulation of gene expression is essential in embryonic development and contributes to cancer pathology. We used a cell-based imaging assay that measures derepression of a silenced green fluorescent protein (GFP) reporter to identify novel classes of compounds involved in epigenetic regulation. This locus derepression (LDR) assay was screened against a 69,137-member chemical library using quantitative high-throughput screening (qHTS), a titration-response method that assays compounds at multiple concentrations. From structure-activity relationships of the 411 actives recovered from the qHTS, 6 distinct chemical series were chosen for further study. A total of 48 qHTS actives and analogs were counterscreened using the parental line of the LDR cells, which lack the GFP reporter. Three series-8-hydroxy quinoline, quinoline-8-thiol, and 1,3,5-thiadiazinane-2-thione-were not fluorescent and reconfirmed activity in the LDR cells. The three active series did not inhibit histone deacetylase activity in nuclear extracts or reactivate the expression of the densely methylated p16 gene in cancer cells. However, one series induced expression of the methylated CDH13 gene and inhibited the viability of several lung cancer lines at submicromolar concentrations. These results suggest that the identified small molecules act on epigenetic or transcriptional components and validate our approach of using a cell-based imaging assay in conjunction with qHTS.

We describe here a series of N-(quinolin-8-yl)benzenesulfonamides capable of suppressing the NFkappaB pathway identified from two high-throughput screens run at two centers of the NIH Molecular Libraries Initiative. These small molecules were confirmed in both primary and secondary assays of NFkappaB activation and expanded upon through analogue synthesis. The series exhibited potencies in the cell-based assays at as low as 0.6 microM, and several indications suggest that the targeted activity lies within a common region of the NFkappaB pathway.

A series of 1,3,5-triazine-2,4,6-triamines were prepared and analyzed as inhibitors of glucocerebrosidase. Synthesis, structure activity relationships and the selectivity of chosen analogues against related sugar hydrolases enzymes are described.

Alzheimer disease is diagnosed postmortem by the density and spatial distribution of beta-amyloid plaques and tau-bearing neurofibrillary tangles. The major protein component of each lesion adopts cross-beta-sheet conformation capable of binding small molecules with submicromolar affinity. In many cases, however, Alzheimer pathology overlaps with Lewy body disease, characterized by the accumulation of a third cross-beta-sheet forming protein, alpha-synuclein. To determine the feasibility of distinguishing tau aggregates from beta-amyloid and alpha-synuclein aggregates with small molecule probes, a library containing 72,455 small molecules was screened for antagonists of tau-aggregate-mediated changes in Thioflavin S fluorescence, followed by secondary screens to distinguish the relative affinity for each substrate protein. Results showed that >10-fold binding selectivity among substrates could be achieved, with molecules selective for tau aggregates containing at least three aromatic or rigid moieties connected by two rotatable bonds.