Pharmacology of nivegacetor (RG6289), a potent and selective gamma secretase modulator in clinical development for the treatment of Alzheimer’s disease

Background Alzheimer’s Disease (AD) is a prevalent neurodegenerative disorder which involves a complex pathobiology driven by amyloid-beta (Aβ) and tau pathologies, among other factors. Aβ peptides are generated via β-secretase (BACE1) and γ-secretase cleavage of amyloid precursor protein (APP). While long isoforms like Aβ42 are neurotoxic and aggregation-prone, shorter isoforms (Aβ38, Aβ37) are non-amyloidogenic. γ-secretase modulators (GSMs) shift production from longer to shorter peptides which is expected to slow down or halt (prevent) amyloid accumulation and its downstream effects. Methods The novel GSM nivegacetor was evaluated in vitro using cell lines overexpressing human wild-type APP, or human APP with the Swedish mutation K670N/M671L (APPSwe). The in vitro selectivity of nivegacetor was tested on Notch-1, a representative gamma secretase substrate other than APP. Additionally, nivegacetor was profiled for its selectivity on a range of pharmacological targets. In vivo studies tested a dose-response and a time course of nivegacetor on soluble Aβ levels in brain tissue of APPSwe transgenic mice. Furthermore, the impact of two ADAD mutations, PSEN1 E280A (Columbian) and PSEN2 N141I (Volga German), on nivegacetor’s potency was tested. Moreover, nivegacetor was tested for possible effects on 3 Hflorbetaben binding to Aβ plaque pathology in human AD brain tissue sections. Results Nivegacetor lowered the production of Aβ42 and Aβ40 and concomitantly increased levels of Aβ37 and Aβ38 in vitro and in vivo in mice. Nivegacetor did not inhibit Notch-1 and showed a favorable selectivity profile on a broad range of targets. When tested on two ADAD mutations, nivegacetor was equipotent on the PSEN1 E280A mutation and significantly less potent on the PSEN2 N141I mutation compared to wild-type gamma secretase. Nivegacetor did not interfere with the detection of amyloid plaques by 3 Hflorbetaben in human AD brain tissue, which is an important prerequisite for the use of florbetaben as a PET tracer in clinical trials. Conclusion Nivegacetor is a potent, orally bioavailable GSM with favorable properties and is currently under investigation as a clinical candidate in a Phase 2A clinical trial in individuals with prodromal and early sporadic AD, and in a Phase 2 clinical trial in individuals carrying the PSEN1 E280A ADAD mutation.