Etrasimod, sold under the brand name Velsipity, is a medication that is used for the treatment of ulcerative colitis.

[6] The most common side effects include lymphopenia (low levels of lymphocytes) and headache.

[8] Etrasimod was discovered by Arena Pharmaceuticals, with subsequent development by Pfizer.

[10] Etrasimod was approved for medical use in the United States in October 2023,[6] and in the European Union in February 2024.

[6][8] It works by causing T cells to become trapped in the lymph nodes, preventing them from entering the bloodstream, from where they would travel to other tissues in the body and mediate inflammation.