The effects of compounds interfering with gamma-secretase, the enzymatic complex responsible of the formation of the amyloid-beta (Abeta) peptide from amyloid-beta protein precursor (AbetaPP), on plaque deposition in transgenic mouse models of Alzheimer's disease are known but scanty data are available on the effects of these drugs on brain plasticity. We evaluated the effects of long-term treatment with CHF5074, a new gamma-secretase modulator, on hippocampal neurogenesis, cortical synaptophysin levels, and contextual memory in transgenic mice carrying the double Swedish mutation of AbetaPP (Tg2576). Six-month old Tg2576 mice were treated with CHF5074 (375 ppm in the diet) up to 15 months of age. Age-matched control transgenic and wild-type mice received standard diet. Compared to wild-type animals, transgenic controls showed a significant decrease in the number of doublecortin-positive neuroblasts in dentate gyrus, synaptophysin intensity in the cortex, freezing to context in the contextual fear conditioning test. Compared to transgenic controls, CHF5074 treatment of Tg2576 mice resulted in a significant attenuation of the neurogenesis impairment in hippocampus (p=0.036), normalization of synaptophysin levels in cortex (p< 0.001), attenuation of plaque burden in the cortex (p=0.033), increases astroglial reaction around plaques (p=0.001), and attenuation of activated microglia (p=0.040). These effects were associated to a complete reversal of contextual memory deficit (p=0.006). Contextual memory significantly correlated with synaptophysin immunoreactivity in the cortex (r=0.548, p=0.0038).

As neuroinflammation is an early event in the pathogenesis of Alzheimer' s disease, new selective antiinflammatory drugs could lead to promising preventive strategies. We evaluated the safety, tolerability, pharmacokinetics and pharmacodynamics of CHF5074, a new microglial modulator, in a 12-week, double-blind, placebo-controlled, parallel groups, ascending dose study involving 96 MCI patients. Subjects were allocated into three successive study cohorts to receive ascending, titrated doses of CHF5074 (200, 400 or 600 mg/day) or placebo. Vital signs, cardiac safety, neuropsychological performance and safety clinical laboratory parameters were assessed on all subjects. Plasma samples were collected throughout the study for measuring drug concentrations, soluble CD40 ligand (sCD40L) and TNF-α. At the end of treatment, cerebrospinal fluid (CSF) samples were optionally collected after the last dose to measure drug levels, β- amyloid1-42 (Aβ42), tau, phospho-tau181, sCD40L and TNF-α. Ten patients did not complete the study: one in the placebo group (consent withdrawn), two in the 200-mg/day treatment group (consent withdrawn and unable to comply) and seven in the 400-mg/day treatment group (five AEs, one consent withdrawn and one unable to comply). The most frequent treatment-emergent adverse events were diarrhea, dizziness and back pain. There were no clinically significant treatmentrelated clinical laboratory, vital sign or ECG abnormalities. CHF5074 total body clearance depended by gender, age and glomerular filtration rate. CHF5074 CSF concentrations increased in a dose-dependent manner. At the end of treatment, mean sCD40L and TNF-α levels in CSF were found to be inversely related to the CHF5074 dose (p=0.037 and p=0.001, respectively). Plasma levels of sCD40L in the 600-mg/day group were significantly lower than those measured in the placebo group (p=0.010). No significant differences between treatment groups were found in neuropsychological tests but a positive dose-response trend was found on executive function in APOE4 carriers. This study shows that CHF5074 is well tolerated in MCI patients after a 12-week titrated treatment up to 600 mg/day and dose-dependently affects central nervous system biomarkers of neuroinflammation.

Abnormal amyloid-β (Aβ) production and deposition is believed to represent one of the main causes of Alzheimer's disease (AD). γ-Secretase is the enzymatic complex responsible for Aβ generation from its precursor protein. Inhibition or modulation of γ-secretase represents an attractive therapeutic approach. CHF5074 is a new γ-secretase modulator that has been shown to inhibit brain plaque deposition and to attenuate memory deficit in adult AD transgenic mice after chronic treatment. To date, it is not known whether the positive behavioral effects of this compound also occur in young transgenic mice without plaque deposition. Here, we evaluated the effects of acute and subchronic treatment with CHF5074 on contextual and recognition memory and on hippocampal synaptic plasticity in plaque-free Tg2576 mice. We found that at 5 months of age, contextual memory impairment was significantly attenuated after acute subcutaneous administration of 30 mg/kg CHF5074. At 6 months of age, recognition memory impairment was fully reversed after a 4-week oral treatment in the diet (≈60 mg/kg/day). These cognitive effects were associated with a reversal of long-term potentiation (LTP) impairment in the hippocampus. A significant reduction in brain intraneuronal AβPP/Aβ levels and hyperphosphorylated tau, but no change in soluble or oligomeric Aβ levels was detected in Tg2576 mice showing functional recovery following CHF5074 treatment. We conclude that the beneficial effects of CHF5074 treatment in young transgenic mice occurred at a stage that precedes plaque formation and were associated with a reduction in intraneuronal AβPP/Aβ and hyperphosphorylated tau.

BackgroundAlzheimer disease is a multifactorial disorder characterized by the progressive deterioration of neuronal networks. The pathological hallmarks includes extracellular amyloid plaques and intraneuronal neurofibrillary tangles, but the primary cause is only partially understood. Thus, there is growing interest in developing agents that might target multiple mechanisms leading to neuronal degeneration. CHF5074 is a nonsteroidal anti-inflammatory derivative that has been shown to behave as a γ-secretase modulator in vitro and to inhibit plaque deposition and to reverse memory deficit in vivo in transgenic mouse models of Alzheimer’s disease (AD). In the present study, the effects of a long-term (13-month) treatment with CHF5074 on indicators of brain functionality and neurodegeneration in transgenic AD mice (Tg2576) have been assessed and compared with those induced by a prototypical γ-secretase inhibitor (DAPT).ResultsTo this end, plaque-free, 6-month-old Tg2576 mice and wild-type littermates were fed with a diet containing CHF5074 (125 and 375 ppm/day), DAPT (375 ppm/day) or vehicle for 13 months. The measured indicators included object recognition memory, amyloid burden, brain oligomeric and plasma Aβ levels, intraneuronal Aβ, dendritic spine density/morphology, neuronal cyclin A positivity and activated microglia. Tg2576 mice fed with standard diet displayed an impairment of recognition memory. This deficit was completely reverted by the higher dose of CHF5074, while no effects were observed in DAPT-treated mice. Similarly, amyloid plaque burden, microglia activation and aberrant cell cycle events were significantly affected by CHF5074, but not DAPT, treatment. Both CHF5074 and DAPT reduced intraneuronal Aβ content, also increasing Aβ40 and Aβ42 plasma levels.ConclusionsThis comparative analysis revealed a profoundly diverse range of clinically relevant effects differentiating the multifunctional anti-inflammatory derivative CHF5074 from the γ-secretase inhibitor DAPT and highlighted unique mechanisms and potential targets that may be crucial for neuroprotection in mouse models of AD.

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