Surprisingly high stability of the Aβ oligomer eliminating all-d-enantiomeric peptide D3 in media simulating the route of orally administered drugs

Abstract

The aggregation of the amyloid β protein (Aβ) plays an important role in the pathology of Alzheimer's disease. Previously, we have developed the all-d-enantiomeric peptide D3, which is able to eliminate neurotoxic Aβ oligomers in vitro and improve cognition in a transgenic Alzheimer's disease mouse model in vivo even after oral administration. d-Peptides are expected to be more resistant against enzymatic proteolysis compared to their l-enantiomeric equivalents, and indeed, a pharmacokinetic study with tritiated D3 revealed the oral bioavailability to be about 58%. To further investigate the underlying properties, we examined the stability of D3 in comparison to its corresponding all-l-enantiomeric mirror image l-D3 in media simulating the gastrointestinal tract, blood and liver. Potential metabolization was followed by reversed-phase high-performance liquid chromatography. In simulated gastric fluid, D3 remained almost completely stable (89%) within 24h, while 70% of l-D3 was degraded within the same time period. Notably, in simulated intestinal fluid, D3 also remained stable (96%) for 24h, whereas l-D3 was completely metabolized within seconds. In human plasma and human liver microsomes, l-D3 was metabolized several hundred times faster than D3. The remarkably high stability may explain the high oral bioavailability seen in previous studies allowing oral administration of the drug candidate. Thus, all-d-enantiomeric peptides may represent a promising new compound class for drug development.

Structural Insights into Curli CsgA Cross-β Fibril Architecture Inspired Repurposing of Anti-amyloid Compounds as Anti-biofilm Agents

“…We next sought to investigate whether known inhibitors of human pathological amyloid formation would effectively inhibit CsgA fibrillation on the basis of this proposed structural similarity. We tested a group of synthetic D-enantiomeric peptides (referred to here as D-peptides) designed against Aβ (55)(56)(57)(58)(59)(60)(61)(62)(63)(64)(65). Two of the D-peptides tested, ANK6 and DB3DB3 (60), were found to inhibit CsgA fibrillation in dose-dependent manners.…”

“…The structural similarity between fibrillar spine segments derived from CsgA and those derived from human pathological amyloids prompted us to investigate whether fibrillation inhibitors designed against human amyloids could also inhibit curli formation. Accordingly, we found that two D-enantiomeric peptides, originally designed to interfere with the formation of oligomers of Alzheimer's disease-associated Aβ (55)(56)(57)(58)(59)(60)(61)(62)(63)(64)(65), inhibited the fibrillation of CsgA spines as well as of full-length CsgA and reduced biofilm formation in curli-expressing Salmonella typhimurium in dosedependent manners. These results provide structural insights into a biofilm-related amyloid and pave the way for the rational development of anti-microbial drugs targeting amyloid-structured biofilms.…”

A d-enantiomeric peptide interferes with heteroassociation of amyloid-β oligomers and prion protein

“…The advantage of D-peptides over L-peptides is their higher protease resistance, resulting in slower degradation and longer half-life (31,32). For A␤(1-42)directed D-peptides, high stability in media simulating the route of orally administered drugs (33) and enhanced proteolytic stability in murine plasma and organ homogenates were shown (34). The lead compound of these D-peptides, D3, had been selected by mirror-image phage display (26,35).…”

In Vitro Potency and Preclinical Pharmacokinetic Comparison of All-D-Enantiomeric Peptides Developed for the Treatment of Alzheimer’s Disease

“…As each -peptide’s 3 H-label was located in a leucine alkyl group (4,5- 3 H- -Leu), the labels were also considered to be biologically stable [ 25 ]. Further underlining the -peptides’ stabilities, Elfgen et al confirmed this by incubation in several media simulating the oral administration route with HPLC analyses [ 22 ]. Thus, the amount of 3 H-labelled -peptide quantified in LSC measurements was used for back-calculation of the total -peptide concentration in the respective samples and pharmacokinetic parameters were calculated subsequently.…”