S1PR1 and rheumatoid arthritis: Next-generation S1PR modulators with fewer adverse effects and receptor specificities, including mocravimod (S1P1/4/5 agonist), ozanimod (S1P1/5 agonist), etrasimod (S1P1/4/5 agonist), amiselimod (S1P1 agonist), ponesimod (S1P1/4/5 agonist), siponimod (S1P1/5 agonist), and ceralifimod (S1P1/5 agonist), were developed and investigated for clinical application in diseases other than multiple sclerosis, including inflammatory bowel disease, psoriasis, atopic dermatitis, rheumatoid arthritis, systemic lupus erythematosus, and certain cancers [87].