Karin Kolmodin

Discovery of AZD3839, a Potent and Selective BACE1 Inhibitor Clinical Candidate for the Treatment of Alzheimer Disease

Background: BACE1 inhibitors target the first step in Aβ formation and are tractable drugs for halting disease progression in Alzheimer disease. Results: AZD3839 is a novel BACE1 inhibitor that effectively reduces brain and CSF Aβ levels in several preclinical species. Conclusion: Based on the preclinical profile, AZD3839 was progressed into Phase I. Significance: AZD3839 may have disease-modifying potential in the treatment of Alzheimer disease. β-Site amyloid precursor protein cleaving enzyme1 (BACE1) is one of the key enzymes involved in the processing of the amyloid precursor protein (APP) and formation of amyloid β peptide (Aβ) species. Because cerebral deposition of Aβ species might be critical for the pathogenesis of Alzheimer disease, BACE1 has emerged as a key target for the treatment of this disease. Here, we report the discovery and comprehensive preclinical characterization of AZD3839, a potent and selective inhibitor of human BACE1. AZD3839 was identified using fragment-based screening and structure-based design. In a concentration-dependent manner, AZD3839 inhibited BACE1 activity in a biochemical fluorescence resonance energy transfer (FRET) assay, Aβ and sAPPβ release from modified and wild-type human SH-SY5Y cells and mouse N2A cells as well as from mouse and guinea pig primary cortical neurons. Selectivity against BACE2 and cathepsin D was 14 and >1000-fold, respectively. AZD3839 exhibited dose- and time-dependent lowering of plasma, brain, and cerebrospinal fluid Aβ levels in mouse, guinea pig, and non-human primate. Pharmacokinetic/pharmacodynamic analyses of mouse and guinea pig data showed a good correlation between the potency of AZD3839 in primary cortical neurons and in vivo brain effects. These results suggest that AZD3839 effectively reduces the levels of Aβ in brain, CSF, and plasma in several preclinical species. It might, therefore, have disease-modifying potential in the treatment of Alzheimer disease and related dementias. Based on the overall pharmacological profile and its drug like properties, AZD3839 has been progressed into Phase 1 clinical trials in man.

Design of compound libraries for fragment screening

Approaches to the design of libraries for fragment screening are illustrated with reference to a 20xa0k generic fragment screening library and a 1.2xa0k generic NMR screening library. Tools and methods for library design that have been developed within AstraZeneca are described, including Foyfi fingerprints and the Flush program for neighborhood characterization. It will be shown how Flush and the BigPicker, which selects maximally diverse sets of compounds, are used to apply the Core and Layer method for library design. Approaches to partitioning libraries into cocktails are also described.

Aminoimidazoles as Bace-1 Inhibitors: The Challenge to Achieve in Vivo Brain Efficacy

The evaluation of a series of bicyclic aminoimidazoles as potent BACE-1 inhibitors is described. The crystal structures of compounds 14 and 23 in complex with BACE-1 reveal hydrogen bond interactions with the protein important for achieving potent inhibition. The optimization of permeability and efflux properties of the compounds is discussed as well as the importance of these properties for attaining in vivo brain efficacy. Compound (R)-25 was selected for evaluation in vivo in wild type mice and 1.5h after oral co-administration of 300μmol/kg (R)-25 and efflux inhibitor GF120918 the brain Aβ40 level was reduced by 17% and the plasma Aβ40 level by 76%.

AZ-4217: a high potency BACE inhibitor displaying acute central efficacy in different in vivo models and reduced amyloid deposition in Tg2576 mice.

Aβ, the product of APP (amyloid precursor protein), has been implicated in the pathophysiology of Alzheimers disease (AD). β-Site APP cleaving enzyme1 (BACE1) is the enzyme initiating the processing of the APP to Aβ peptides. Small molecule BACE1 inhibitors are expected to decrease Aβ-peptide generation and thereby reduce amyloid plaque formation in the brain, a neuropathological hallmark of AD. BACE1 inhibition thus addresses a key mechanism in AD and its potential as a therapeutic target is currently being addressed in clinical studies. Here, we report the discovery and the pharmacokinetic and pharmacodynamic properties of BACE1 inhibitor AZ-4217, a high potency compound (IC50 160 pm in human SH-SY5Y cells) with an excellent in vivo efficacy. Central efficacy of BACE1 inhibition was observed after a single dose in C57BL/6 mice, guinea pigs, and in an APP transgenic mouse model of cerebral amyloidosis (Tg2576). Furthermore, we demonstrate that in a 1 month treatment paradigm BACE1 inhibition of Aβ production does lower amyloid deposition in 12-month-old Tg2576 mice. These results strongly support BACE1 inhibition as concretely impacting amyloid deposition and therefore potentially an important approach for therapeutic intervention in AD.

Evidence for dimeric BACE-mediated APP processing.

beta-Secretase (BACE) is an aspartyl protease, which proteolytically processes amyloid precursor protein, making BACE an interesting pharmacological target in Alzheimers disease. To study the enzymatic function of BACE, we mutated either of the two aspartic acid residues in the active site of BACE. This rendered BACE functionally inactive without affecting the degree of glycosylation or endosomal localization. In contrast, substituting both active site aspartic acid residues produced a functionally inactive, endoplasmic reticulum-retained and partially glycosylated BACE. Interestingly, co-expression of the two single active site mutants partially restored beta-site cleavage of amyloid precursor protein, and the restored activity was inhibited with similar dose-dependency and potency as wildtype BACE by a small molecule inhibitor raised against BACE. In sum, our data suggest that two different active site mutants can complement each other in a partially functional BACE dimer and mediate APP processing.

Potent and orally efficacious benzothiazole amides as TRPV1 antagonists.

Benzothiazole amides were identified as TRPV1 antagonists from high throughput screening using recombinant human TRPV1 receptor and structure-activity relationships were explored to pinpoint key pharmacophore interactions. By increasing aqueous solubility, through the attachment of polar groups to the benzothiazole core, and enhancing metabolic stability, by blocking metabolic sites, the drug-like properties and pharmokinetic profiles of benzothiazole compounds were sufficiently optimized such that their therapeutic potential could be verified in rat pharmacological models of pain.

In vivo reduction of beta-amyloid peptides in the brain of Tg2576 mice after oral administration of a novel BACE1 inhibitor

daily for 7 days, then 16 mg daily for 7 days, followed by a co-administration period of 10 days with 125 mg avagacestat.Results: 32 and 34 subjects were randomized in the donepezil and galantamine study, respectively. Coadministration of avagacestat and donepezil or galantamine was associated with an increase in the geometric mean Cmax (14-21%) and AUC(TAU) (24-26%) of donepezil and/or galantamine; an increase not likely to be clinically relevant. One serious adverse event (SAE) was reported in healthy subjects co-administered avagacestat and galantamine for 10 days. On Day 25, a subject was found to have elevated lipase (5x ULN) and amylase (2x ULN) and was diagnosed with pancreatitis. The subject, who also had multiple gall stones, was admitted to the hospital, was treated, and recovered fully. Co-administration of avagacestat with either donepezil or galantamine in healthy subjects for short periods of timewas associated with a higher frequency of AEs than administration of donepezil or galantamine alone. The most common AEs in either study included headache, nausea, and epistaxis. Most AEs were mild in nature and all, except nasal congestion, resolved prior to study discharge. Conclusions: Co-administration of multiple 125 mg doses of avagacestat (the highest dose tested in phase IIb studies) and either donepezil or galantamine at steady-state appeared to be generally well tolerated in healthy subjects. Co-administration of avagacestat was not associated with clinically relevant increases in Cmax or AUC for either donepezil or galantamine.