S1PR1 and multiple sclerosis: As such, S1P1 has served as an attractive receptor for pharmacological intervention in autoimmune diseases, and S1P receptor modulators have been studied clinically in diseases and conditions such as organ transplant rejection, lupus, atopic dermatitis, inflammatory bowel disease, and multiple sclerosis (MS) (Park and Im, 2017; Tanaka et al., 2020; Roy et al., 2021).