In vivo effects of the alpha-synuclein misfolding inhibitor minzasolmin supports clinical development in Parkinson's disease

Abstract

Direct targeting of alpha-synuclein (ASYN) has emerged as a disease-modifying strategy for Parkinson's disease and other synucleinopathies which is being approached using both small molecule compounds and ASYN-targeted biologics. Minzasolmin (UCB0599) is an orally bioavailable and brain-penetrant small molecule ASYN misfolding inhibitor in clinical development as a disease-modifying therapeutic for Parkinson's disease. Herein the results of preclinical evaluations of minzasolmin that formed the basis for subsequent clinical development are described. Pharmacokinetic evaluations of intraperitoneal 1 and 5 mg/kg minzasolmin in wildtype mice revealed parallel and dose-proportional exposures in brain and plasma. Three-month administration studies in the Line 61 transgenic mouse model of PD were conducted to measure ASYN pathology and other PD-relevant endpoints including markers of CNS inflammation, striatal DAT labeling and gait. Reductions in ASYN pathology were correlated with improved aspects of gait and balance, reductions in CNS inflammation marker abundance, and normalized striatal DAT levels. These findings provide support for human dose determinations and have informed the translational strategy for clinical trial design and biomarker selection for the ongoing clinical studies of minzasolmin in patients living with early-stage Parkinson's disease (ClinicalTrials.gov ID: NCT04658186; EudraCT Number 2020-003265).

Fig. 1. Structure of minzasolmin (UCB0599): a clinical stage small molecule advancing through development as a putative therapeutic for Parkinson’s disease.

The structure, IUPAC nomenclature and molecular weight of minzasolmin (International Patent Publication Number WO 2015/116663 A1). The rendering was generated by Biovia Draw 2020 version 20.1.

Fig. 2. Improved gait in Line 61 transgenic mice treated with minzasolmin (UCB0599).

a Line 61 transgenic mice had gait deficits as indicated by lower round beam performance composite scores in vehicle-treated Line 61 transgenic mice compared to non-transgenic control mice (****P < 0.0001; N/group = 8 (Non-tg/Vehicle), 9 (Line 61 tg/Vehicle), 11 (Line 61 tg/1 mg/kg) and 10 (Line 61 tg/5 mg/kg)). Gait deficits were attenuated in 1 mg/kg minzasolmin (UCB0599)-treated Line 61 transgenic mice compared to vehicle-treated Line 61 transgenic mice with an increase in scoring (^## P < 0.01). Data are presented as group means ± SEM. b Radar plot of composite score components used to visualize the gait and balance-related deficit profile of vehicle-treated Line 61 transgenic mice compared to non-transgenic control mice that is normalized by minzasolmin treatments.

Fig. 3. Minzasolmin (UCB0599) reduces total ASYN pathology in Line 61 transgenic mice.

Statistically significant increases in total ASYN immunolabeling were observed in the (a) cortex, (b) hippocampus and (c) striatum of vehicle-treated Line 61 transgenic mice as compared to non-transgenic control mice (****P < 0.0001 for all regions). Compared with vehicle-treated Line 61 transgenic controls, minzasolmin (UCB0599) administration (1 and 5 mg/kg) in Line 61 transgenic mice produced statistically significant reductions in total ASYN levels in the (a) cortex (^# P < 0.05 and ^#### P < 0.0001, respectively), (b) hippocampus (^#### P < 0.0001, for both doses), and (c) striatum (^#### P < 0.0001, for both doses). Data are presented as group means ± SEM. Representative images in (d) were chosen based on the group mean for each treatment group. Scale bars represent 250 μm and 40 μm for low- and high-magnification images, respectively.

Fig. 4. Minzasolmin (UCB0599) reduces disease-relevant proteinase K-resistant ASYN pathology in Line 61 transgenic mice.

Proteinase K-resistant ASYN immunolabeling was observed in the (a) cortex, (b) hippocampus and (c) striatum of vehicle-treated Line 61 transgenic, but not non-transgenic control mice. Compared to vehicle-treated Line 61 transgenic controls, minzasolmin (UCB0599) administration (1 and 5 mg/kg) in Line 61 transgenic mice produced statistically significant reductions in total ASYN levels in the (a) cortex (b) hippocampus, and (c) striatum (^#### P < 0.0001, for all regions and doses). Data are presented as group means ± SEM. Representative images in (d) were chosen based on the group mean for each treatment group. Scale bars represent 250 μm and 40 μm for low- and high-magnification images, respectively.

Fig. 5. ASYN pathology is negatively correlated with round beam performance.

Pearson r correlation analyses of (a) total or (b) Proteinase K-resistant ASYN immunolabeling versus the total round beam scoring with reveals negative correlations, demonstrating reduced round beam performance with increased ASYN burden in all regions evaluated. Accordingly, reduced ASYN pathology was associated with improved round beam performance.

Fig. 6. Minzasolmin (UCB0599) normalizes striatal dopamine transporter (DAT) levels in Line 61.

Evaluations of dopamine transporter levels in striatum. a Statistically significant decreases in striatal DAT immunolabeling were observed in vehicle-treated Line 61 transgenic mice compared to non-transgenic control mice (****P < 0.0001). Compared with vehicle-treated Line 61 transgenic controls, minzasolmin (UCB0599) administration (1 and 5 mg/kg) in Line 61 transgenic mice produced statistically significant normalizations in striatal DAT levels (^# P < 0.05 and ^#### P < 0.0001, respectively). Data are presented as group means ± SEM. Representative images in (b) were chosen based on the group mean for each treatment group. Low magnification survey images were obtained at 4x and followed by imaging at ×40 for analysis of DAT immunolabeling (scale bar = 25 mm). c Pearson r correlation analyses of DAT with (left to right panels) total or Proteinase K-resistant forms of ASYN in the striatum, or functional round beam composite scoring reveals negative and positive correlations, respectively.

Fig. 7. Minzasolmin (UCB0599) administration normalizes GFAP immunolabeling in Line 61 transgenic mice.

GFAP immunolabeling was increased in the (a) neocortex and (b) hippocampus (CA1/2) of vehicle-treated Line 61 transgenic mice compared to non-transgenic control mice (^**** P < 0.0001, for both regions). 1 and 5 mg/kg minzasolmin administration decreased GFAP immunolabeling in Line 61 transgenic mice compared to vehicle-treated Line 61 transgenic mice (^#### P < 0.0001, for both regions and doses). Data are presented as group means ± SEM. Representative images in (c) were chosen based on the group mean for each treatment group. A low-magnification overview of the hippocampus and overlying cortical regions is shown in the upper row of images. Higher-magnification inset images of GFAP immunolabeling in the hippocampus are shown in the lower row of images. d There were positive correlations between GFAP with total ASYN in the cortex (left panel), and the hippocampus (right panel).