Rational design, synthesis, and biological evaluation of indole-piperazine based α-ketoamide derivatives as dual Aβ and tau aggregation modulators for Alzheimer's disease.

Abstract

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by pathological aggregation of amyloid-β (Aβ) and tau proteins, representing two major hallmarks of disease progression. Targeting both aggregation pathways simultaneously offers a promising therapeutic strategy. Building upon our previous identification of the α-ketoamide derivative BD23 as a dual aggregation modulator, we report the rational design, synthesis, and biological evaluation of a new series of indole-piperazine based α-ketoamide moiety. A focused library of twenty-four compounds was synthesized and characterized using nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry (HRMS). These compounds were evaluated for modulation of Aβ42 aggregation using the thioflavin T fluorescence assay. Several derivatives significantly altered fibrillization kinetics, with MD03, MD07, MD08, and MD10 emerging as the most active candidates. Among them, MD08 exhibited optimal aqueous solubility (0.037 ± 0.0035 mg/mL) along with moderate blood-brain barrier permeability (Pe = 3.42 ± 0.33 × 10-6 cm/s). Further evaluation demonstrated that MD08 inhibited heparin-induced tau aggregation in vitro, without cytotoxicity in human neuroblastoma (SH-SY5Y) cells. In vivo studies in an Aβ-induced cognitive decline mouse model revealed significant cognitive improvement in a dose-dependent manner (2, 5, and 10 mg/kg), with the highest dose showing efficacy comparable to the standard drug donepezil. Complementary in silico studies, including molecular docking and molecular dynamics simulations, supported stable interactions with Aβ and tau. Collectively, these findings identify MD08 as a promising dual aggregation modulator for AD, warranting further preclinical investigation.