RATIONALEThe β-secretase BACE1 initiates amyloid-β (Aβ) generation and represents a long-standing prime therapeutic target for the treatment of Alzheimer's disease (AD). However, BACE1 inhibitors tested to date in clinical trials have yielded no beneficial outcomes. In fact, prior BACE1 inhibitor trials targeted at ~ 50-90% Aβ reductions in symptomatic or prodromal AD stages have ended in the discontinuation due to futility and/or side effects, including cognitive worsening rather than expected improvement at the highest dose.OBJECTIVESWe tested whether a combination strategy with the selective BACE1 inhibitor GRL-8234 and the FDA-approved symptomatic drug memantine may provide synergistic cognitive benefits within their safe dose range.METHODSThe drug effects were evaluated in the advanced symptomatic stage of 5XFAD mice that developed extensive cerebral Aβ deposition.RESULTSChronic combination treatment with 33.4-mg/kg GRL-8234 and 10-mg/kg memantine, but not either drug alone, rescued cognitive deficits in 5XFAD mice at 12 months of age (the endpoint after 60-day drug treatment), as assessed by the contextual fear conditioning, spontaneous alternation Y-maze and nest building tasks. Intact baseline performances of wild-type control mice on three cognitive paradigms demonstrated that combination treatment did not augment potential cognitive side effects of individual drugs. Biochemical and immunohistochemical examination showed that combination treatment did not synergistically reduce the β-amyloidogenic processing of amyloid precursor protein or Aβ levels in 5XFAD mouse brains.CONCLUSIONSA combination strategy with BACE1 inhibitors and memantine may be able to increase the effectiveness of individual drugs within their safe dose range in AD therapy.

01 Jun 2021·Neuropsychopharmacology Reports

Accelerated long‐term forgetting is a BACE1 inhibitor‐reversible incipient cognitive phenotype in Alzheimer’s disease model mice

Article

Author: Ohno, Masuo

AbstractAimAfter the continued failure of β‐secretase (BACE1) inhibitor clinical trials in prodromal as well as mild‐to‐moderate Alzheimer's disease (AD), they are shifting to further earlier or asymptomatic stages. The aim of this study is to explore a cognitive paradigm that allows us to more sensitively detect beneficial effects of BACE1 inhibitors in presymptomatic AD.MethodsGRL‐8234 (33.4 mg/kg, ip), a small‐molecule BACE1 inhibitor, was administered once daily for 28 days to the 5XAFD transgenic mouse model of AD. The contextual fear conditioning was used to evaluate the effects of GRL‐8234 on memory deficits in 5XFAD mice at different ages.ResultsChronic administration of GRL‐8234 to 5XFAD mice rescued their contextual memory deficits, when tested 1 day after training at 6‐8 months but not at 12 months of age. Importantly, 4‐month‐old 5XFAD mice retain the ability to form contextual memory equivalent to wild‐type controls, demonstrating that the standard method of 1‐day memory assessment is not suitable for evaluating BACE1 inhibitor efficacy in ameliorating cognitive declines during earlier disease stages. Despite normal contextual memory formation, young 5XFAD mice showed faster forgetting when a longer delay (28 days) intervened between training and memory testing. Notably, GRL‐8234 administered to 4‐month‐old 5XFAD mice during the 28‐day delay reversed accelerated long‐term forgetting almost completely back to wild‐type control levels.ConclusionThe results provide experimental evidence that accelerated long‐term forgetting represents more sensitive memory testing that can help evaluate BACE1 inhibitor therapy in presymptomatic AD populations.

03 Jan 2015·Current Alzheimer ResearchQ4 · MEDICINE

Beneficial Effects of the β-Secretase Inhibitor GRL-8234 in 5XFAD Alzheimer’s Transgenic Mice Lessen During Disease Progression

Q4 · MEDICINE

Article

Author: Ohno, Masuo ; Devi, Latha ; Tang, Jordan

The β-secretase enzyme BACE1, which initiates the cleavage of amyloid precursor protein (APP) into the amyloid-β (Aβ) peptide, is a prime therapeutic target for Alzheimer's disease (AD). However, recent investigations using genetic animal models raise concern that therapeutic BACE1 inhibition may encounter the dramatic reduction of efficacy in ameliorating AD-like pathology and memory deficits during disease progression. Here, we compared the effects of the potent and selective small-molecule BACE1 inhibitor GRL-8234 in different pathological stages of AD mouse model. Specifically, we administered GRL-8234 (33.4 mg/kg, i.p.) once daily for 2 months to 5XFAD transgenic mice, which showed modest (4 months) and massive (10 months of age) Aβ plaque deposition at starting points. Chronic treatments with GRL-8234 reversed memory impairments, as tested by the spontaneous alternation Y-maze task, in the younger 5XFAD group concomitant with significant reductions in cerebral Aβ42 levels. In contrast, only marginal reductions of Aβ42 were observed in 12-month-old 5XFAD mice treated with GRL-8234 and their memory function remained impaired. We found that not only BACE1 but also full-length APP expression was significantly elevated with progressive Aβ accumulation in 5XFAD mice, while GRL-8234 failed to affect these detrimental mechanisms that further accelerate plaque growth in brains of older 5XFAD mice. Therefore, our results provide important insights into the mechanisms by which Aβ accumulation and related memory impairments become less responsive to rescue by BACE1 inhibition during the course of AD development.

100 Deals associated with GRL-8234

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Indication	Highest Phase	Country/Location	Organization	Date
Alzheimer Disease	Preclinical	-	CoMentis, Inc.	-
Alzheimer Disease	Preclinical	-	Purdue Research Foundation	-
Alzheimer Disease	Preclinical	-	Oklahoma Medical Research Foundation	-
Alzheimer Disease	Preclinical	-	University of Illinois	-

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