Alzheimer’s disease (AD) was first described a little more than 100 years ago. It is the most common cause of dementia with an estimated prevalence of 30 million people worldwide, a number that is expected to quadruple in 40 years. There currently is no effective treatment that delays the onset or slows the progression of AD. However, major scientific advances in the areas of genetics, biochemistry, cell biology, and neuroscience over the past 25 years have changed the way we think about AD. This review discusses some of the challenges to translating these basic molecular and cellular discoveries into clinical therapies. Current information suggests that if the disease is detected before the onset of overt symptoms, it is possible that treatments based on knowledge of underlying pathogenesis can and will be effective.

Alzheimer’s Disease: The Challenge of the Second Century

Genetic factors play a major role in determining a person's risk to develop Alzheimer's disease (AD). Rare mutations transmitted in a Mendelian fashion within affected families, for example, APP, PSEN1, and PSEN2, cause AD. In the absence of mutations in these genes, disease risk is largely determined by common polymorphisms that, in concert with each other and nongenetic risk factors, modestly impact risk for AD (e.g., the e4-allele in APOE). Recent genome-wide screening approaches have revealed several additional AD susceptibility loci and more are likely to be discovered over the coming years. In this chapter, we review the current state of AD genetics research with a particular focus on loci that now can be considered established disease genes. In addition to reviewing the potential pathogenic relevance of these genes, we provide an outlook into the future of AD genetics research based on recent advances in high-throughput sequencing technologies.

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The genetics of Alzheimer's disease.

The Alzheimer's disease (AD)-associated amyloid-β protein precursor (AβPP) is cleaved by α-, β-, and presenilin (PS)/γ-secretases through sequential regulated proteolysis. These proteolytic events control the generation of the pathogenic amyloid-β (Aβ) peptide, which excessively accumulates in the brains of individuals afflicted by AD. A growing number of additional proteins cleaved by PS/γ-secretase continue to be discovered. Similarly to AβPP, most of these proteins are type-I transmembrane proteins involved in vital signaling functions regulating cell fate, adhesion, migration, neurite outgrowth, or synaptogenesis. All the identified proteins share common structural features, which are typical for their proteolysis. The consequences of the PS/γ-secretase-mediated cleavage on the function of many of these proteins are largely unknown. Here, we review the current literature on the proteolytic processing mediated by the versatile PS/γ-secretase complex. We begin by discussing the steps of AβPP processing and PS/γ-secretase complex composition and localization, which give clues to how and where the processing of other PS/γ-secretase substrates may take place. Then we summarize the typical features of PS/γ-secretase-mediated protein processing. Finally, we recapitulate the current knowledge on the possible physiological function of PS/γ-secretase-mediated cleavage of specific substrate proteins.

The Many Substrates of Presenilin/γ-Secretase

γ-Secretase inhibitors and modulators.

Near-infrared fluorescence (NIRF) molecular imaging has been widely applied to monitoring therapy of cancer and other diseases in preclinical studies; however, this technology has not been applied successfully to monitoring therapy for Alzheimer’s disease (AD). Although several NIRF probes for detecting amyloid beta (Aβ) species of AD have been reported, none of these probes has been used to monitor changes of Aβs during therapy. In this article, we demonstrated that CRANAD-3, a curcumin analog, is capable of detecting both soluble and insoluble Aβ species. In vivo imaging showed that the NIRF signal of CRANAD-3 from 4-mo-old transgenic AD (APP/PS1) mice was 2.29-fold higher than that from age-matched wild-type mice, indicating that CRANAD-3 is capable of detecting early molecular pathology. To verify the feasibility of CRANAD-3 for monitoring therapy, we first used the fast Aβ-lowering drug LY2811376, a well-characterized beta-amyloid cleaving enzyme-1 inhibitor, to treat APP/PS1 mice. Imaging data suggested that CRANAD-3 could monitor the decrease in Aβs after drug treatment. To validate the imaging capacity of CRANAD-3 further, we used it to monitor the therapeutic effect of CRANAD-17, a curcumin analog for inhibition of Aβ cross-linking. The imaging data indicated that the fluorescence signal in the CRANAD-17–treated group was significantly lower than that in the control group, and the result correlated with ELISA analysis of brain extraction and Aβ plaque counting. It was the first time, to our knowledge, that NIRF was used to monitor AD therapy, and we believe that our imaging technology has the potential to have a high impact on AD drug development.

https://www.pnas.org/content/pnas/112/31/9734.full.pdf

Near-infrared fluorescence molecular imaging of amyloid beta species and monitoring therapy in animal models of Alzheimer’s disease

Modulation of γ-Secretase Reduces β-Amyloid Deposition in a Transgenic Mouse Model of Alzheimer's Disease

https://alz-journals.onlinelibrary.wiley.com/doi/pdf/10.1016/j.trci.2016.09.003

NGP 555, a γ-Secretase Modulator, Lowers the Amyloid Biomarker, Aβ42, in Cerebrospinal Fluid while Preventing Alzheimer's Disease Cognitive Decline in Rodents.

The present invention relates to the production of a Kuniz type protease inhibitor (KPI) peptide, and its use in regulating protease activity associated with amyloidosis This invention is further directed to in vivo and in vitro models of amyloidosis involving the KPI peptide The KPI peptide can also be used to treat coagulation disorders by regulating proteases in the coagulation pathway KPI is also used to inhibit or ameliorate protease-associated damage following injury, especially head injury Nucleic acid sequences encoding the protease inhibitor and expression systems for high level expression of the active inhibitor are provided

Recombinant amyloid precursor protein inhibitor domain and treatment of various disease states

NGP 555, a γ-secretase modulator, shows a beneficial shift in the ratio of amyloid biomarkers in human cerebrospinal fluid at safe doses

In accordance with the present invention, there are provided formulations of gamma secretase modulators (GSMs) which are suitable for oral delivery and have improved transport properties relative to prior art formulations thereof. Also provided are methods for the preparation of such improved formulations and uses thereof for the delivery of GSMs to subjects in need thereof.

William T. Comer

Papers

Modulation of γ-Secretase Reduces β-Amyloid Deposition in a Transgenic Mouse Model of Alzheimer's Disease

NGP 555, a γ-Secretase Modulator, Lowers the Amyloid Biomarker, Aβ42, in Cerebrospinal Fluid while Preventing Alzheimer's Disease Cognitive Decline in Rodents.

Recombinant amyloid precursor protein inhibitor domain and treatment of various disease states

NGP 555, a γ-secretase modulator, shows a beneficial shift in the ratio of amyloid biomarkers in human cerebrospinal fluid at safe doses

Formulations containing gamma secretase modulators