Steve Jacobsen

Design and Synthesis of 5,5′-Disubstituted Aminohydantoins as Potent and Selective Human β-Secretase (BACE1) Inhibitors

The identification of small molecule aminohydantoins as potent and selective human beta-secretase inhibitors is reported. These analogues exhibit low nannomolar potency for BACE1, show comparable activity in a cell-based (ELISA) assay, and demonstrate >100x selectivity for the other structurally related aspartyl proteases BACE2, cathepsinD, renin, and pepsin. On the basis of the cocrystal structure of the HTS-hit 2 in the BACE1 active site and by use of a structure-based drug design approach, we methodically explored the comparatively large binding pocket of the BACE1 enzyme and identified key interactions between the ligand and the protein that contributed to the affinity. One of the more potent compounds, (S)-55, displayed an IC(50) value for BACE1 of 10 nM and exhibited comparable cellular activity (EC(50) = 20 nM) in the ELISA assay. Acute oral administration of (S)-55 at 100 mg/kg resulted in a 69% reduction of plasma A beta(40) at 8 h in a Tg2576 mouse (p < 0.001).

Design and synthesis of aminohydantoins as potent and selective human β-secretase (BACE1) inhibitors with enhanced brain permeability.

The identification of small molecule aminohydantoins as potent and selective human β-secretase inhibitors is reported. These analogs exhibit good brain permeability (40-70%), low nanomolar potency for BACE1, and demonstrate >100-fold selectivity for the structurally related aspartyl proteases cathepsin D, renin and pepsin. Alkyl and alkoxy groups at the meta-position of the P1 phenyl, which extend toward the S3 region of the enzyme, have contributed to the ligands reduced affinity for the efflux transporter protein P-gp, and decreased topological polar surface area, thus resulting in enhanced brain permeability. A fluorine substitution at the para-position of the P1 phenyl has contributed to 100-fold decrease of CYP3A4 inhibition and enhancement of compound metabolic stability. The plasma and brain protein binding properties of these new analogs are affected by substitutions at the P1 phenyl moiety. Higher compound protein binding was observed in the brain than in the plasma. Two structurally diverse potent BACE1 inhibitors (84 and 89) reduced 30% plasma Aβ40 in the Tg2576 mice in vivo model at 30 mg/kg p.o..

Discovery and initial optimization of 5,5'-disubstituted aminohydantoins as potent β-secretase (BACE1) inhibitors

8,8-Diphenyl-2,3,4,8-tetrahydroimidazo[1,5-a]pyrimidin-6-amine (1) was identified through HTS, as a weak (micromolar) inhibitor of BACE1. X-Ray crystallographic studies indicate the 2-aminoimidazole ring forms key H-bonding interactions with Asp32 and Asp228 in the catalytic site of BACE1. Lead optimization using structure-based focused libraries led to the identification of low nanomolar BACE1 inhibitors such as 20b with substituents which extend from the S(1) to the S(3) pocket.

Small-molecule inhibition of Usp14 enhances the proteolytic degradation and clearance of misfolded proteins associated with neurodegenerative diseases

ENHANCES THE PROTEOLYTIC DEGRADATION AND CLEARANCE OF MISFOLDED PROTEINS ASSOCIATEDWITH NEURODEGENERATIVE DISEASES Steve Jacobsen, Chris Conrad, Andres Hurtado-Lorenzo, Mohmmad Hafiz, Akhil Bhalla, Megan Foley, Bob Chambers, Dee Shen, Jyoti Malhotra, Brad Poland, Eric Roskelley, David Hurtado, Peter Lee-Armandt, James Soper, Eva Nokes, Jennifer Andersen, Dan Garza, Brad Geddes, Brad Tait, Peter Reinhart, Byung-Hoon Lee, Dan Finley, Randy King, Proteostasis Therapeutics, Cambridge, Massachusetts, United States; 2 Proteostasis Therapeutics, Cambridge, Massachusetts, United States; Harvard Medical School, Boston, Massachusetts, United States.

P4-085: The role of liver X receptor (LXR) agonists in modulating Aβ levels in vitro and in vivo

Recent studies show that intracellular cholesterol levels can modulate the processing of amyloid precursor protein (APP) to A peptide, the major constituent of senile plaques in Alzheimer’s disease (AD). As well as influencing A production, cholesterol, and in particular, cholesterol-rich apolipoprotein E (apoE) containing lipoproteins may also promote A clearance and degradation. Agonists of liver X receptor (LXR) transcriptionally induce a variety of genes involved in cellular lipid efflux and transport, including ATP binding cassette A1 (ABCA1) and apoE. As such, LXR agonists have the potential to both inhibit APP processing and promote A clearance. Here we show that LXR activation yielded inconsistent effects on A production in vitro. A range of tool LxR agonists either decreased, stimulated or had no effect on A 40 and A 42 secretion. In vivo, LXR agonist TO901317 dose dependently increased brain ABCA1 and apoE levels with a concomitant decrease in A 42 levels in APP transgenic (Tg2576) mice. Interestingly, TO901317 had no significant effects on levels of A 40, full length APP, or the APP processing products; sAPP , sAPP , and CTF . Since A 42 has been linked to memory failure in the Tg2576, we examined the effects of TO901317 in the contextual fear conditioning paradigm; TO901317 completely reversed the working memory deficit in these mice. Together these data demonstrate that LxR agonists do not directly inhibit APP processing but rather facilitate the clearance of A 42 and improve working memory.