Andrew Pate Owens

Generation of C-terminally truncated amyloid-β peptides is dependent on γ-secretase activity

Aberrant production of amyloid‐β peptides by processing of the β‐amyloid precursor protein leads to the formation of characteristic extracellular protein deposits which are thought to be the cause of Alzheimers disease. Therefore, inhibiting the key enzymes responsible for amyloid‐β peptide generation, β‐ and γ‐secretase may offer an opportunity to intervene with the progression of the disease. In human brain and cell culture systems a heterogeneous population of amyloid‐β peptides with various truncations is detected and at present, it is unclear how they are produced. We have used a combination of surface enhanced laser desorption/ionization time‐of‐flight mass spectrometry (SELDI‐TOF MS) and a specific inhibitor of γ‐secretase to investigate whether the production of all amyloid‐β peptide species requires the action of γ‐secretase. Using this approach, we demonstrate that the production of all truncated amyloid‐β peptides except those released by the action of the nonamyloidogenic α‐secretase enzyme or potentially beta‐site βAPP cleaving enzyme 2 depends on γ‐secretase activity. This indicates that none of these peptides are generated by a separate enzyme entity and a specific inhibitor of the γ‐secretase enzyme should havethe potential to block the generation of all amyloidogenicpeptides. Furthermore in the presence of γ‐secretase inhibitors, the observation of increased cleavage of the membrane‐bound βAPP C‐terminal fragment C99 by α‐secretase suggests that during its trafficking C99 encounters compartments in which α‐secretase activity resides.

A new series of potent benzodiazepine γ-secretase inhibitors

Abstract A new series of benzodiazepine-containing γ-secretase inhibitors with potential use in the treatment of Alzheimers disease is disclosed. Structure–activity relationships of the pendant hydrocinnamate side-chain which led to the preparation of highly potent inhibitors are described.

Piperidine-ether based hNK1 antagonists 2: Investigation of the effect of N-substitution

Abstract The effect of nitrogen substitution on the binding affinity of the piperidine-ether substance P antagonist L-733,060 for the hNK 1 receptor and L-type Ca 2+ channel is discussed.

Discovery of Selective and Potent Inhibitors of Gram-Positive Bacterial Thymidylate Kinase (TMK).

Thymidylate kinase (TMK) is an essential enzyme in bacterial DNA synthesis. The deoxythymidine monophosphate (dTMP) substrate binding pocket was targeted in a rational-design, structure-supported effort, yielding a unique series of antibacterial agents showing a novel, induced-fit binding mode. Lead optimization, aided by X-ray crystallography, led to picomolar inhibitors of both Streptococcus pneumoniae and Staphylococcus aureus TMK. MICs < 1 μg/mL were achieved against methicillin-resistant S. aureus (MRSA), S. pneumoniae, and vancomycin-resistant Enterococcus (VRE). Log D adjustments yielded single diastereomers 14 (TK-666) and 46, showing a broad antibacterial spectrum against Gram-positive bacteria and excellent selectivity against the human thymidylate kinase ortholog.

Synthesis and γ-secretase activity of APP substrate-based hydroxyethylene dipeptide isosteres

Two new APP substrate-based hydroxyethylene isosteres (AT and VI) were prepared and their dipeptide conjugates shown not to inhibit the γ-secretase-mediated formation of either Aβ1-40 or Aβ1-42. The FG isostere and a des-hydroxy hydroxyethylene isostere also gave inactive compounds. Conversely, a number of compounds containing the intact substrate-unrelated Phe-Phe (FF) hydroxyethylene isostere were shown to be potent inhibitors (ED50=14–732 nM). These results show that the factors governing the substrate-based design of γ-secretase inhibitors are more complicated than first thought.

3-benzyloxy-2-phenylpiperidine NK1 antagonists: The influence of alpha methyl substitution

Abstract In vitro metabolism studies on a series of 3,5-bis(trifluoromethyl)benzyl ethers have identified 3,5-bis(trifluoromethyl)benzoic acid as a significant metabolite possibly arising via oxidation of the benzylic position. A methyl group was introduced in an effort to suppress this route of metabolism. One diastereoisomer displayed an increase in affinity and a marked improvement in duration of action. In vitro metabolism studies on a series of 3,5-bis(trifluoromethyl)benzyl ethers have identified 3,5-bis(trifluoromethyl)benzoic acid as a significant metabolite possibly arising via oxidation at the benzylic position. A methyl group was introduced in an effort to suppress this route of metabolism. One diastereoisomer displayed an increase in affinity and a marked improvement in duration of action

Spirocyclic NK1 antagonists I:[4.5] and [5.5]-spiroketals

A series of novel spiroketal-based NK(1) antagonists is described. The effect of modifications to the spiroether ring and aromatic substituents are discussed, leading to the identification of compounds with high affinity and excellent CNS penetration.

A small molecule mitigates hearing loss in a mouse model of Usher syndrome III

Usher syndrome type III (USH3) characterized by progressive deafness, variable balance disorder, and blindness is caused by destabilizing mutations in the gene encoding the clarin-1 protein (CLRN1). Here we report a novel strategy to mitigate hearing loss associated with a common USH3 mutation CLRN1N48K that involved a cell-based high-throughput screening of small molecules capable of stabilizing CLRN1N48K, a secondary screening to eliminate general proteasome inhibitors, and finally an iterative process to optimize structure activity relationships. This resulted in the identification of BF844. To test the efficacy of BF844, a mouse model was developed that mimicked the progressive hearing loss of USH3. BF844 effectively attenuated progressive hearing loss and prevented deafness in this model. Because the human CLRN1N48K mutation causes both hearing and vision loss, BF844 could in principle prevent both sensory deficiencies in USH3. Moreover, the strategy described here could help identify drugs for other protein-destabilizing monogenic disorders.

Acyclic NK1 antagonists: Replacements for the benzhydryl group.

Abstract An exploration of benzhydryl replacements is described. Whilst bridged and fused polynuclear aromatic systems both incur a reduction in affinity it was possible to replace the benzhydryl by a single phenyl ring with only a modest reduction in affinity. In contrast to the analogous diphenylalanyl ethers the binding was also shown to be stereoselective.

Spirocyclic NK1 antagonists II: [4.5]-spiroethers

A series of novel spiroether-based neurokinin-1 (NK(1)) antagonists is described. The effect of modifications to the spiroether ring and aromatic substituents are discussed, leading to the identification of compounds with high affinity and excellent CNS penetration.