Siponimod Demonstrates Pro-remyelination Effects in the Mouse Cuprizone-Intoxication Model (2503)

Objective: To assess the relevance of the cuprizone-intoxication model for studying the pro-remyelination effects of siponimod. Background: Recent clinical observations, using magnetic resonance imaging (MRI) to assess the magnetization transfer ratio (MTR) and T2-weighted signal intensity (T2-WSI), revealed pro-myelination effects for siponimod, the first oral disease-modifying therapy shown to reduce disability progression, cognitive decline, and total brain volume loss versus placebo in SPMS patients. Hence, siponimod appears to be an ideal pharmacological tool to validate/invalidate preclinical mechanistic models for the translational study of remyelination processes. Design/Methods: Typically, cuprizone treatment in mice (5 weeks; 0.2% in diet) produces robust signs of demyelination in the brain corpus callosum (CC) and external capsule (EC), visualized by MRI (MTR and T2-WSI). Upon stopping cuprizone treatment, slow spontaneous remyelination can be observed by quantitative immunohistochemistry (qIHC) for myelin density (Luxol Fast Blue staining [LFB]) and oligodendrocyte numbers (GST-π+ cells) in brain sections. This study compared the impacts of siponimod treatment (via drug-loaded diet [10 mg/kg]) with a control diet. Results: Cuprizone-intoxication resulted in a marked demyelination within the CC/EC, indicated by a 24% increase in mean T2-WSI and 5–7% reduction in mean MTR. Within 2 weeks of cuprizone washout, control mice showed a small but significant reduction (8%) in T2-WSI, not associated with MTR changes. This indicated a weak spontaneous remyelination, confirmed by qIHC. In siponimod-treated mice, drug levels reached in blood and brain were within the expected range (0.4 and 2.5 μM, respectively) and the level of spontaneous remyelination over 2 weeks, measured by qIHC, was significantly increased (by 26% and 16%, respectively) versus controls, although no significant impact on MRI parameters could be detected. Conclusions: The mouse cuprizone-intoxication model appears to be a relevant mechanistic model for exploring siponimod-sensitive remyelination processes, with monitoring periods longer than 2 weeks needed for visualization via imaging techniques. Disclosure: Marc Bigaud has received personal compensation for serving as an employee of Novartis Pharma. Nicolau Beckmann has received personal compensation for serving as an employee of Novartis Pharma AG. Nicolau Beckmann has received stock or an ownership interest from Novartis Pharma AG. Sandrine Desrayaud has received personal compensation for serving as an employee of Novartis Pharma AG. Claude HAGER has received personal compensation for serving as an employee of Novartis. Anna Neuhaus has nothing to disclose. Laura Bollepalli has received personal compensation for serving as an employee of Novartis. Stefan Rudin has nothing to disclose. Peter Wipfli has received personal compensation for serving as an employee of Novartis Pharma AG. Stefan Zurbruegg has received personal compensation for serving as an employee of Novartis Pharma. Derya Shimshek has received personal compensation for serving as an employee of Novartis Pharma AG. Derya Shimshek has received stock or an ownership interest from Novartis Pharma AG. Derya Shimshek has received intellectual property interests from a discovery or technology relating to health care.