S1PR1 and myeloid sarcoma: Hence, selectivity was further fine-tuned with second-generation molecules to maximize benefits and lessen the risk of side effects, leading to the development of the S1P1 and S1P5 selective modulators siponimod and ozanimod, which have also been approved for relapsing forms of MS (Mayzent approval language, 2021; Zeposia approval language, 2021; Roy et al., 2021).