THE MOLECULAR TWEEZER CLR01 AMELIORATES PATHOLOGY IN THE P301S-TAU MOUSE MODEL

Tau self-assembly into neurotoxic oligomers and fibrils underlies the pathophysiology in tauopathies. Molecular tweezers (MTs) act as unique, artificial nanochaperones and are the first small molecules whose activity as modulators/inhibitors of abnormal protein self-assembly has been discovered using a rational approach. Previously, we evaluated the effect of a lead MT, called CLR01, in the 3×Tg mouse model, which overexpresses mutant human PS1(M146V), APP(KM670/671NL), and tau(P301L). Immunohistochemistry (IHC) showed robust reduction of amyloid plaques, neurofibrillary tangles, and microgliosis. Because tau hyperphosphorylation is downstream of Aβ insults, the question whether CLR01 affected tau directly or indirectly remained open. Therefore, we asked if CLR01 could be used for treatment of tauopathies in the absence of amyloid pathology and set up to answer this question using the P301S-tau mouse model. The study included five groups of mice, each comprising 8 males and 8 females. The treatment groups included three Tg groups, administered 0, 0.3, or 1.0 mg/kg per day CLR01 and two wild-type littermate groups receiving 0 or 1.0 mg/kg per day CLR01. CLR01 was administered for 35 days via osmotic minipumps implanted subcutaneously at 6−6.5 months of age. The mice were weighed out and grip-strength and open field tests were performed in the beginning, middle (grip-strength only), and end of the treatment. No adverse effects were observed in any of the groups. CLR01 prevented a decline in grip-strength observed in vehicle-treated Tg mice. The mice did not show deficits in any open-field test precluding evaluation of drug effect. Following completion of the treatment, the mice were sacrificed and the brains were collected and divided into the two hemispheres. One hemisphere was fixed and sectioned for IHC analysis and the other hemisphere was dissected into regions of interest. Brain regions were snap-frozen and extracted into soluble, membrane-bound, and insoluble fractions. ELISA results and cell culture-based seeding assay show that CLR01 treatment reduced tau hyperphosphorylation and formation of tau seeds. Analysis of tau oligomerization is also underway. Our initial results strongly suggest CLR01's target engagement and beneficial therapeutic effect.