Discovery of a potent, orally bioavailable pyrimidine VLA-4 antagonist effective in a sheep asthma model.

A series of N-(pyrimidin-4-yl)-phenylalanine VLA-4 antagonists is described. Optimization of substituents at the 2 and 5 positions of the pyrimidine ring gave 14, a very potent VLA-4 inhibitor which is orally active in a sheep asthma model.

Design, synthesis, and crystal structure of hydroxyethyl secondary amine-based peptidomimetic inhibitors of human beta-secretase.

The design and synthesis of a novel series of potent and cell permeable peptidomimetic inhibitors of the human beta-secretase (BACE) are described. These inhibitors feature a hydroxyethyl secondary amine isostere and a novel aromatic ring replacement for the C-terminus. The crystal structure of BACE in complex with this hydroxyethyl secondary amine isostere inhibitor is also presented.

The identification and optimization of orally efficacious, small molecule VLA-4 antagonists.

The identification of orally active, small molecule antagonists of the alpha4beta1 integrin, VLA-4, could lead to therapeutic agents with utility in a number of clinical settings, including asthma, multiple sclerosis and IBD. Starting from CDR3 sequences conserved among neutralizing alpha4 antibodies, peptides were identified that antagonized VLA-4 mediated adhesion in vitro. Through a series of structural modifications, these peptides evolved into small molecules that exhibited high potency and selectivity for VLA-4 in cell adhesion assays. Finally, through the optimization of physical and pharmacokinetic properties, compounds were identified that exhibited oral activity in animal models of asthma and multiple sclerosis.

Design of substrate-based inhibitors of human beta-secretase.

By use of the effectively cleaved beta-secretase (BACE) substrate (1), incorporation of a statine in P(1) resulted in a weak inhibitor 13 of the enzyme. Further substitution of P(1)'-Asp by P(1)'-Val in 13 results in a potent inhibitor 22 of BACE. Removal of the P(10)-P(5) residues on the N-terminal part of inhibitor 22 resulted in no loss of potency (23). C-terminal truncations of inhibitor 22 generally led to significant loss of potency.

Design and synthesis of hydroxyethylene-based peptidomimetic inhibitors of human beta-secretase.

The hydroxyethylene (HE) transition state isostere was developed as a scaffold to provide potent, small molecule inhibitors of human beta-secretase (BACE). The previous work on the statine series proved critical to the discovery of HE structure-activity relationships. Compound 20 with the N-terminal isophthalamide proved to be the most potent HE inhibitor (IC(50) = 30 nM) toward BACE. Unlike the statine series, we identified HE inhibitors without carboxylic acids on the C terminus, leading to enhanced cell penetration and making them attractive candidates for further drug development in Alzheimer's disease.

Design and synthesis of statine-based cell-permeable peptidomimetic inhibitors of human beta-secretase.

We describe the development of statine-based peptidomimetic inhibitors of human beta-secretase (BACE). The conversion of the peptide inhibitor 1 into cell-permeable peptidomimetic inhibitors of BACE was achieved through an iterative strategy of conceptually subdividing 1 into three regions: an N-terminal portion, a central statine-containing core, and a C-terminus. Replacement of the amino acid residues of 1 with moieties with less peptidic character was done with retention of BACE enzyme inhibitory activity. This approach led to the identification of the cell-permeable BACE inhibitor 38 that demonstrated BACE-mechanism-selective inhibition of Abeta secretion in human embryonic kidney cells.

A series of C-terminal amino alcohol dipeptide A beta inhibitors.

Potent, small molecule A beta inhibitors have been prepared that incorporate an alanine core bracketed by an N-terminal arylacetyl group and various C-terminal amino alcohols. The compounds exhibit stereospecific inhibition as demonstrated in an in vitro assay.