Siponimod is a selective modulator of sphingosine-1-phosphate (S1P) receptors of types 1 and 5, registered in the Russian Federation for the treatment of patients with secondary progressive multiple sclerosis (SPMS), regardless of the presence or absence of exacerbations. The effectiveness of the drug in comparison with placebo was demonstrated in patients with SPMS in the international clinical trial EXPAND (phase III). This review devotes actual problems in the treatment of patients with SPMS, discusses the pathophysiology of multiple sclerosis progression, describes the peripheral and central mechanisms of siponimod action and its differences from fingolimod. According to analysis of scientific literature experimental, clinical and neuroimaging data are presented, which could explain the reasons for the successful use of siponimod in patients with SPMS, taking into account the pathophysiological mechanisms of the development of progression and the mechanisms of drug action.