In Vitro and In Vivo Efficacies of the Linear and the Cyclic Version of an All-d-Enantiomeric Peptide Developed for the Treatment of Alzheimer's Disease.

Multiple sources of evidence suggest that soluble amyloid ß (Aß)-oligomers are responsible for the development and progression of Alzheimer's disease (AD). In order to specifically eliminate these toxic Aß-oligomers, our group has developed a variety of all-d-peptides over the past years. One of them, RD2, has been intensively studied and showed such convincing in vitro and in vivo properties that it is currently in clinical trials. In order to further optimize the compounds and to elucidate the characteristics of therapeutic d-peptides, several rational drug design approaches have been performed. Two of these d-peptides are the linear tandem (head-to-tail) d-peptide RD2D3 and its cyclized form cRD2D3. Tandemization and cyclization should result in an increased in vitro potency and increase pharmacokinetic properties, especially crossing the blood-brain-barrier. In comparison, cRD2D3 showed a superior pharmacokinetic profile to RD2D3. This fact suggests that higher efficacy can be achieved in vivo at equally administered concentrations. To prove this hypothesis, we first established the in vitro profile of both d-peptides here. Subsequently, we performed an intraperitoneal treatment study. This study failed to provide evidence that cRD2D3 is superior to RD2D3 in vivo as in some tests cRD2D3 failed to show equal or higher efficacy.

Oral Treatment with RD2RD2 Impedes Development of Motoric Phenotype and Delays Symptom Onset in SOD1G93A Transgenic Mice.

Neuroinflammation is a pathological hallmark of several neurodegenerative disorders and plays a key role in the pathogenesis of amyotrophic lateral sclerosis (ALS). It has been implicated as driver of disease progression and is observed in ALS patients, as well as in the transgenic SOD1G93A mouse model. Here, we explore and validate the therapeutic potential of the d-enantiomeric peptide RD2RD2 upon oral administration in SOD1G93A mice. Transgenic mice were treated daily with RD2RD2 or placebo for 10 weeks and phenotype progression was followed with several behavioural tests. At the end of the study, plasma cytokine levels and glia cell markers in brain and spinal cord were analysed. Treatment resulted in a significantly increased performance in behavioural and motor coordination tests and a decelerated neurodegenerative phenotype in RD2RD2-treated SOD1G93A mice. Additionally, we observed retardation of the average disease onset. Treatment of SOD1G93A mice led to significant reduction in glial cell activation and a rescue of neurons. Analysis of plasma revealed normalisation of several cytokines in samples of RD2RD2-treated SOD1G93A mice towards the levels of non-transgenic mice. In conclusion, these findings qualify RD2RD2 to be considered for further development and testing towards a disease modifying ALS treatment.

PEAß Triggers Cognitive Decline and Amyloid Burden in a Novel Mouse Model of Alzheimer's Disease.

Understanding the physiopathology of Alzheimer's disease (AD) has improved substantially based on studies of mouse models mimicking at least one aspect of the disease. Many transgenic lines have been established, leading to amyloidosis but lacking neurodegeneration. The aim of the current study was to generate a novel mouse model that develops neuritic plaques containing the aggressive pyroglutamate modified amyloid-ß (pEAß) species in the brain. The TAPS line was developed by intercrossing of the pEAß-producing TBA2.1 mice with the plaque-developing line APPswe/PS1ΔE9. The phenotype of the new mouse line was characterized using immunostaining, and different cognitive and general behavioral tests. In comparison to the parental lines, TAPS animals developed an earlier onset of pathology and increased plaque load, including striatal pEAß-positive neuritic plaques, and enhanced neuroinflammation. In addition to abnormalities in general behavior, locomotion, and exploratory behavior, TAPS mice displayed cognitive deficits in a variety of tests that were most pronounced in the fear conditioning paradigm and in spatial learning in comparison to the parental lines. In conclusion, the combination of a pEAß- and a plaque-developing mouse model led to an accelerated amyloid pathology and cognitive decline in TAPS mice, qualifying this line as a novel amyloidosis model for future studies.

A Novel Anti-Inflammatory d-Peptide Inhibits Disease Phenotype Progression in an ALS Mouse Model.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by selective neuronal death in the brain stem and spinal cord. The cause is unknown, but an increasing amount of evidence has firmly certified that neuroinflammation plays a key role in ALS pathogenesis. Neuroinflammation is a pathological hallmark of several neurodegenerative disorders and has been implicated as driver of disease progression. Here, we describe a treatment study demonstrating the therapeutic potential of a tandem version of the well-known all-d-peptide RD2 (RD2RD2) in a transgenic mouse model of ALS (SOD1*G93A). Mice were treated intraperitoneally for four weeks with RD2RD2 vs. placebo. SOD1*G93A mice were tested longitudinally during treatment in various behavioural and motor coordination tests. Brain and spinal cord samples were investigated immunohistochemically for gliosis and neurodegeneration. RD2RD2 treatment in SOD1*G93A mice resulted not only in a reduction of activated astrocytes and microglia in both the brain stem and lumbar spinal cord, but also in a rescue of neurons in the motor cortex. RD2RD2 treatment was able to slow progression of the disease phenotype, especially the motor deficits, to an extent that during the four weeks treatment duration, no significant progression was observed in any of the motor experiments. Based on the presented results, we conclude that RD2RD2 is a potential therapeutic candidate against ALS.

Deceleration of the neurodegenerative phenotype in pyroglutamate-Aß accumulating transgenic mice by oral treatment with the Aß oligomer eliminating compound RD2.

Alzheimer's disease, a multifactorial incurable disorder, is mainly characterised by progressive neurodegeneration, extracellular accumulation of amyloid-ß protein (Aß), and intracellular aggregation of hyperphosphorylated tau protein. During the last years, Aß oligomers have been claimed to be the disease causing agent. Consequently, development of compounds that are able to disrupt already existing Aß oligomers is highly desirable. We developed d-enantiomeric peptides, consisting solely of d-enantiomeric amino acid residues, for the direct and specific elimination of toxic Aß oligomers. The drug candidate RD2 did show high oligomer elimination efficacy in vitro and the in vivo efficacy of RD2 was demonstrated in treatment studies by enhanced cognition in transgenic mouse models of amyloidosis. Here, we report on the in vitro and in vivo efficacy of the compound towards pyroglutamate-Aß, a particular aggressive Aß species. Using the transgenic TBA2.1 mouse model, which develops pyroglutamate-Aß(3-42) induced neurodegeneration, we are able to show that oral RD2 treatment resulted in a significant deceleration of the progression of the phenotype. The in vivo efficacy against this highly toxic Aß species further validates RD2 as a drug candidate for the therapeutic use in humans.

Do We Need Anti-Prion Compounds to Treat Alzheimer's Disease?

BACKGROUND: While phase III clinical trials for the treatment of Alzheimer's disease (AD) keep failing regardless of the target, more and more data suggest that the toxic protein assemblies of amyloid-beta protein (Aß) and tubulin binding protein (TAU) behave like prions. Irrespective of the question of whether AD is theoretically or practically contagious, the presence of a self-replicating toxic etiologic agent in the brains of AD patients must have decisive consequences for drug development programs and clinical trial designs. OBJECTIVES: We intend to challenge the hypothesis that the underlying etiologic agent of AD is behaving prion-like. We want to discuss whether the outcome of clinical trials could have been predicted based on this hypothesis, and whether compounds that directly disassemble the toxic prion could be more beneficial for AD treatment. METHOD: We collected publicly accessible pre-clinical efficacy data of Aß targeting compounds that failed or still are in phase III clinical trials. We describe the desired properties of an anti-prion compound and compare it the properties of past and current phase III drug candidates. RESULTS: We could not find convincing and reproducible pre-clinical efficacy data of past and current phase III drug candidates on cognition other than in preventive treatment settings. The desired properties of an anti-Aß-prionic compound are fulfilled by the drug candidate RD2, which has been developed to directly disassemble toxic Aß oligomers. CONCLUSION: RD2 is the first anti-prion drug candidate. It is able to enhance cognition and impede neurodegeneration in three different transgenic AD mouse models, even under truly non-preventive conditions and even when applied orally. In addition, it is safe in humans.

Large-Scale Oral Treatment Study with the Four Most Promising D3-Derivatives for the Treatment of Alzheimer's Disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that is associated with the aggregation of the amyloid ß protein (Aß). Aß oligomers are currently thought to be the major neurotoxic agent responsible for disease development and progression. Thus, their elimination is highly desirable for therapy development. Our therapeutic approach aims at specific and direct elimination of toxic Aß oligomers by stabilizing Aß monomers in an aggregation-incompetent conformation. We have proven that our lead compound "D3", an all d-enantiomeric-peptide, specifically eliminates Aß oligomers in vitro. In vivo, D3 enhances cognition and reduces plaque load in several transgenic AD mouse models. Here, we performed a large-scale oral proof of concept efficacy study, in which we directly compared four of the most promising D3-derivatives in transgenic mice expressing human amyloid precursor protein with Swedish and London mutations (APPSL), transgenic mice, to identify the most effective compound. RD2 and D3D3, both derived from D3 by rational design, were discovered to be the most effective derivatives in improving cognition in the Morris water maze. The performance of RD2- and D3D3-treated mice within the Morris water maze was significantly better than placebo-treated mice and, importantly, nearly as good as those of non-transgenic littermates, suggesting a complete reversal of the cognitive deficit of APPSL mice.

Pharmacokinetic Properties of a Novel D-Peptide Developed to be Therapeutically Active Against Toxic ß-Amyloid Oligomers.

PURPOSE: It has been shown that amyloid ß (Aß) oligomers play an important role in the pathology of Alzheimer's disease (AD). D3, a peptide consisting solely of D-enantiomeric amino acid residues, was developed to specifically eliminate Aß oligomers and is therapeutically active in transgenic AD mice. D-peptides have several advantages over L-peptides, but little is known about their pharmacokinetic potential in vivo. Here, we analysed the pharmacokinetic properties of RD2, a rationally designed and potent D3 derivative. METHODS: The pharmacokinetic analysis was performed using (3)H-RD2 after administration via several routes in mice. The time dependent amount of radiolabelled RD2 was measured in plasma and several organ homogenates by liquid scintillation counting. Furthermore, binding to plasma proteins was estimated. RESULTS: RD2 penetrates into the brain, where it is thought to implement its therapeutic function. All administration routes result in a maximal brain concentration per dose (Cmax/D) of 0.06 (µg/g)/(mg/kg) with brain/plasma ratios ranging between 0.7 and 1.0. RD2 shows a small elimination constant and a long terminal half-life in plasma of more than 2 days. It also exhibits high bioavailability after i.p., s.c. or p.o. administration. CONCLUSIONS: These excellent pharmacokinetic properties confirm that RD2 is a very promising drug candidate for AD.

Structure characterization of unexpected covalent O-sulfonation and ion-pairing on an extremely hydrophilic peptide with CE-MS and FT-ICR-MS.

In this study, we characterized unexpected side-products in a commercially synthesized peptide with the sequence RPRTRLHTHRNR. This so-called peptide D3 was selected by mirror phage display against low molecular weight amyloid-ß-peptide (Aß) associated with Alzheimer's disease. Capillary electrophoresis (CE) was the method of choice for structure analysis because the extreme hydrophilicity of the peptide did not allow reversed-phase liquid chromatography (RPLC) and hydrophilic interaction stationary phases (HILIC). CE-MS analysis, applying a strongly acidic background electrolyte and different statically adsorbed capillary coatings, provided fast and efficient analysis and revealed that D3 unexpectedly showed strong ion-pairing with sulfuric acid. Moreover, covalent O-sulfonation at one or two threonine residues was identified as a result of a side reaction during peptide synthesis, and deamidation was found at either the asparagine residue or at the C-terminus. In total, more than 10 different species with different m/z values were observed. Tandem-MS analysis with collision induced dissociation (CID) using a CE-quadrupole-time-of-flight (QTOF) setup predominantly resulted in sulfate losses and did not yield any further characteristic fragment ions at high collision energies. Therefore, direct infusion Fourier transform ion cyclotron resonance (FT-ICR) MS was employed to identify the covalent modification and discriminate O-sulfonation from possible O-phosphorylation by using an accurate mass analysis. Electron transfer dissociation (ETD) was used for the identification of the threonine O-sulfation sites. In this work, it is shown that the combination of CE-MS and FT-ICR-MS with ETD fragmentation was essential for the full characterization of this extremely basic peptide with labile modifications.

An orally available Cav2.2 calcium channel inhibitor for the treatment of neuropathic pain.

BACKGROUND AND PURPOSE: Neuropathic pain affects up to 10% of the global population and is caused by an injury or a disease affecting the somatosensory, peripheral, or central nervous system. NP is characterized by chronic, severe and opioid-resistant properties. Therefore, its clinical management remains very challenging. The N-type voltage-gated calcium channel, Cav2.2, is a validated target for therapeutic intervention in chronic and neuropathic pain. The conotoxin ziconotide (Prialt®) is an FDA-approved drug that blocks Cav2.2 channel but needs to be administered intrathecally. Thus, although being principally efficient, the required application route is very much in disfavour. EXPERIMENTAL APPROACH AND KEY RESULTS: Here, we describe an orally available drug candidate, RD2, which competes with ziconotide binding to Cav2.2 at nanomolar concentrations and inhibits Cav2.2 almost completely reversible. Other voltage-gated calcium channel subtypes, like Cav1.2 and Cav3.2, were affected by RD2 only at concentrations higher than 10 µM. Data from sciatic inflammatory neuritis rat model demonstrated the in vivo proof of concept, as low-dose RD2 (5 mg·kg-1) administered orally alleviated neuropathic pain compared with vehicle controls. High-dose RD2 (50 mg·kg-1) was necessary to reduce pain sensation in acute thermal response assessed by the tail flick test. CONCLUSIONS AND IMPLICATIONS: Taken together, these results demonstrate that RD2 has antiallodynic properties. RD2 is orally available, which is the most convenient application form for patients and caregivers. The surprising and novel result from standard receptor screens opens the room for further optimization into new promising drug candidates, which address an unmet medical need.

Elevated Aß aggregates in feces from Alzheimer's disease patients: a proof-of-concept study.

BACKGROUND: Misfolding and aggregation of amyloid ß (Aß), along with neurofibrillary tangles consisting of aggregated Tau species, are pathological hallmarks of Alzheimer's disease (AD) onset and progression. In this study, we hypothesized the clearance of Aß aggregates from the brain and body into the gut. METHODS: To investigate this, we used surface-based fluorescence intensity distribution analysis (sFIDA) to determine the Aß aggregate concentrations in feces from 26 AD patients and 31 healthy controls (HC). RESULTS: Aß aggregates were detectable in human feces and their concentrations were elevated in AD patients compared to HC (specificity 90.3%, sensitivity 53.8%). CONCLUSION: Thus, fecal Aß aggregates constitute a non-invasive biomarker candidate for diagnosing AD. Whether digestion-resistant Aß aggregates in feces are secreted via the liver and bile or directly from the enteric neuronal system remains to be elucidated.

Aß oligomers peak in early stages of Alzheimer's disease preceding tau pathology.

INTRODUCTION: Soluble amyloid beta (Aß) oligomers have been suggested as initiating Aß related neuropathologic change in Alzheimer's disease (AD) but their quantitative distribution and chronological sequence within the AD continuum remain unclear. METHODS: A total of 526 participants in early clinical stages of AD and controls from a longitudinal cohort were neurobiologically classified for amyloid and tau pathology applying the AT(N) system. Aß and tau oligomers in the quantified cerebrospinal fluid (CSF) were measured using surface-based fluorescence intensity distribution analysis (sFIDA) technology. RESULTS: Across groups, highest Aß oligomer levels were found in A+ with subjective cognitive decline and mild cognitive impairment. Aß oligomers were significantly higher in A+T- compared to A-T- and A+T+. APOE Îµ4 allele carriers showed significantly higher Aß oligomer levels. No differences in tau oligomers were detected. DISCUSSION: The accumulation of Aß oligomers in the CSF peaks early within the AD continuum, preceding tau pathology. Disease-modifying treatments targeting Aß oligomers might have the highest therapeutic effect in these disease stages. Highlights: Using surface-based fluorescence intensity distribution analysis (sFIDA) technology, we quantified Aß oligomers in cerebrospinal fluid (CSF) samples of the DZNE-Longitudinal Cognitive Impairment and Dementia (DELCODE) cohortAß oligomers were significantly elevated in mild cognitive impairment (MCI)Amyloid-positive subjects in the subjective cognitive decline (SCD) group increased compared to the amyloid-negative control groupInterestingly, levels of Aß oligomers decrease at advanced stages of the disease (A+T+), which might be explained by altered clearing mechanisms.

Oral Treatment with d-RD2RD2 Impedes Early Disease Mechanisms in SOD1*G93A Transgenic Mice but Does Not Prolong Survival.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease affecting upper and lower motor neurons, thus, progressing to complete muscle loss until the patient dies from respiratory arrest. The disease is not curable, and patients die approximately 2-5 years after diagnosis. Studying the underlying disease mechanisms to get access to new treatment options is, therefore, essential for patients' benefit. However, so far, only three drugs that alleviate the symptoms have been approved by the U.S. Food and Drug Administration (FDA). A new drug candidate for the treatment of ALS is the all-d-enantiomeric peptide RD2RD2. In this study, we investigated the therapeutic effect of RD2RD2 in two setups. First, we analyzed disease progression and survival in 7 week-old B6.Cg-Tg(SOD1*G93A)1Gur/J mice. Second, we confirmed the result of the survival analysis in the B6SJL-Tg(SOD1*G93A)1Gur/J mouse line. Shortly before disease onset, the mice were treated daily with an oral dose of 50 mg/kg body weight. Treatment with RD2RD2 led to a delayed disease onset and reduced motor phenotype as shown using the SHIRPA test, the splay reflex test, and the pole test, but did not affect survival. In conclusion, RD2RD2 has the ability to delay the onset of symptoms.

Evaluation of the 18F-labeled analog of the therapeutic all-D-enantiomeric peptide RD2 for amyloid ß imaging.

Positron emission tomography (PET) imaging with radiotracers that bind to fibrillary amyloid ß (Aß) deposits is an important tool for the diagnosis of Alzheimer's disease (AD) and for the recruitment of patients into clinical trials. However, it has been suggested that rather than the fibrillary Aß deposits, it is smaller, soluble Aß aggregates that exert a neurotoxic effect and trigger AD pathogenesis. The aim of the current study is to develop a PET probe that is capable of detecting small aggregates and soluble Aß oligomers for improved diagnosis and therapy monitoring. An 18F-labeled radioligand was prepared based on the Aß-binding d-enantiomeric peptide RD2, which is currently being evaluated in clinical trials as a therapeutic agent to dissolve Aß oligomers. 18F-labeling was carried out using palladium-catalyzed S-arylation of RD2 with 2-[18F]fluoro-5-iodopyridine ([18F]FIPy). Specific binding of [18F]RD2-cFPy to brain material from transgenic AD (APP/PS1) mice and AD patients was demonstrated with in vitro autoradiography. In vivo uptake and biodistribution of [18F]RD2-cFPy were evaluated using PET analyses in wild-type and transgenic APP/PS1 mice. Although brain penetration and brain wash-out kinetics of the radioligand were low, this study provides proof of principle for a PET probe based on a d-enantiomeric peptide binding to soluble Aß species.

Oral treatment with the all-d-peptide RD2 enhances cognition in aged beagle dogs - A model of sporadic Alzheimer's disease.

Disease-modifying therapies to treat Alzheimer's disease (AD) are of fundamental interest for aging humans, societies, and health care systems. Predictable disease progression in transgenic AD models favors preclinical studies employing a preventive study design with an early pre-symptomatic treatment start, instead of assessing a truly curative approach with treatment starting after diagnosed disease onset. The aim of this study was to investigate the pharmacokinetic profile and efficacy of RD2 to enhance short-term memory and cognition in cognitively impaired aged Beagle dogs - a non-transgenic model of truly sporadic AD. RD2 has previously demonstrated pharmacodynamic efficacy in three different transgenic AD mouse models in three different laboratories. Here, we demonstrate that oral treatment with RD2 significantly reduced cognitive deficits in cognitively impaired aged Beagle dogs even beyond the treatment end, which suggests in combination with the treatment dependent CSF tau oligomer decrease a disease-modifying effect of RD2 treatment.

Development of an α-synuclein fibril and oligomer specific tracer for diagnosis of Parkinson's disease, dementia with Lewy bodies and multiple system atrophy.

The development of specific disease-associated PET tracers is one of the major challenges, the realization of which in neurodegenerative diseases would enable not only the efficiency of diagnosis but also support the development of disease-modifying therapeutics. Parkinson's disease (PD) is the most common neurodegenerative movement disorder and is characterized by neuronal fibrillary inclusions composed of aggregated α-synuclein (α-syn). However, these deposits are not only found in PD, but also in other related diseases such as multiple system atrophy (MSA) and dementia with Lewy bodies (DLB), which are grouped under the term synucleinopathies. In this study, we used NGS-guided phage display selection to identify short peptides that bind aggregated α-syn. By surface plasmon resonance (SPR)-based affinity screening, we identified the peptide SVLfib-5 that recognizes aggregated α-syn with high complex stability and sequence specificity. Further analysis SPR showed that SVLfib-5 is not only specific for aggregated α-syn, but in particular recognizes fibrillary and oligomeric structures. Moreover, fluorescence microscopy of human brain tissue sections from PD, MSA, and DLB patients with SVLfib-5 allowed specific recognition of α-syn and a clear discrimination between diseased and non-diseased samples. These findings provide the basis for the further development of an α-syn PET tracer for early diagnosis and monitoring of disease progression and therapy progress.

Aß oligomer concentration in mouse and human brain and its drug-induced reduction ex vivo.

The elimination of amyloid beta (Aß) oligomers is a promising strategy for therapeutic drug development of Alzheimer's disease (AD). AD mouse models that develop Aß pathology have been used to demonstrate in vivo efficacy of compounds that later failed in clinical development. Here, we analyze the concentration and size distribution of Aß oligomers in different transgenic mouse models of AD and in human brain samples by surface-based fluorescence intensity distribution analysis (sFIDA), a highly sensitive method for detecting and quantitating protein aggregates. We demonstrate dose- and time-dependent oligomer elimination by the compound RD2 in mouse and human AD brain homogenates as sources of native Aß oligomers. Such ex vivo target engagement analyses with mouse- and human-brain-derived oligomers have the potential to enhance the translational value from pre-clinical proof-of-concept studies to clinical trials.

Sex-Related Motor Deficits in the Tau-P301L Mouse Model.

The contribution of mouse models for basic and translational research at different levels is important to understand neurodegenerative diseases, including tauopathies, by studying the alterations in the corresponding mouse models in detail. Moreover, several studies demonstrated that pathological as well as behavioral changes are influenced by the sex. For this purpose, we performed an in-depth characterization of the behavioral alterations in the transgenic Tau-P301L mouse model. Sex-matched wild type and homozygous Tau-P301L mice were tested in a battery of behavioral tests at different ages. Tau-P301L male mice showed olfactory and motor deficits as well as increased Tau pathology, which was not observed in Tau-P301L female mice. Both Tau-P301L male and female mice had phenotypic alterations in the SHIRPA test battery and cognitive deficits in the novel object recognition test. This study demonstrated that Tau-P301L mice have phenotypic alterations, which are in line with the histological changes and with a sex-dependent performance in those tests. Summarized, the Tau-P301L mouse model shows phenotypic alterations due to the presence of neurofibrillary tangles in the brain.

Oral absorption enhancement of the amyloid-ß oligomer eliminating compound RD2 by conjugation with folic acid.

Amyloid-ß (Aß) plays a central role in the development and progression of Alzheimer's disease (AD) with Aß oligomers representing the most toxic species. The all-d-enantiomeric peptide RD2, which recently successfully completed clinical phase I, specifically eliminates Aß oligomers in vitro as well as in vivo and improves cognitive deficits in various transgenic AD mouse models even after oral administration. To further enhance the oral absorption of RD2, folic acid has been conjugated to the d-peptide promoting an endocytosis-mediated uptake via a folate receptor located in the intestine. Two different conjugation strategies were selected to obtain prodrugs with folic acid being cleaved after intestinal absorption releasing unmodified RD2 in order to enable RD2's unaltered systemic efficacy. Both conjugates remained stable in simulated gastrointestinal fluids. But only one of them was suitable as prodrug as it was cleaved to RD2 in vitro in human blood plasma and liver microsomes and in vivo in mice after intravenous injection leading to a systemic release of RD2. Furthermore, the conjugate's permeability in vitro and after oral administration in mice was strongly enhanced compared to unconjugated RD2 demonstrating the prodrug's functionality. However, the conjugate seemed to have impaired the mice's wellbeing shortly after oral administration possibly resulting from strain-specific hypersensitivity to folic acid. Nevertheless, we assume that the prodrug is actually non-toxic, especially in lower concentrations as verified by a cell viability test. Furthermore, lower dosages can be applied with unaltered efficacy due to its enhanced oral absorption.

All-d-Enantiomeric Peptide D3 Designed for Alzheimer's Disease Treatment Dynamically Interacts with Membrane-Bound Amyloid-ß Precursors.

Alzheimer's disease (AD) is a severe neurodegenerative pathology with no effective treatment known. Toxic amyloid-ß peptide (Aß) oligomers play a crucial role in AD pathogenesis. All-d-Enantiomeric peptide D3 and its derivatives were developed to disassemble and destroy cytotoxic Aß aggregates. One of the D3-like compounds is approaching phase II clinical trials; however, high-resolution details of its disease-preventing or pharmacological actions are not completely clear. We demonstrate that peptide D3 stabilizing Aß monomer dynamically interacts with the extracellular juxtamembrane region of a membrane-bound fragment of an amyloid precursor protein containing the Aß sequence. MD simulations based on NMR measurement results suggest that D3 targets the amyloidogenic region, not compromising its α-helicity and preventing intermolecular hydrogen bonding, thus creating prerequisites for inhibition of early steps of Aß conversion into ß-conformation and its toxic oligomerization. An enhanced understanding of the D3 action molecular mechanism facilitates development of effective AD treatment and prevention strategies.