Ontamalimab is a fully human immunoglobulin G2 monoclonal antibody against mucosal addressin cell adhesion molecule-1 in development for the induction and maintenance of clinical remission in patients with ulcerative colitis (UC). This study aimed to assess the long-term pharmacokinetics (PK) of ontamalimab in patients with UC, and the effects of concomitant medications on PK parameters.