On 14 April, the FDA rejected Lilly’s biologic licence application (BLA) for their anti-interleukin (IL)-23, mirikizumab, which is in development for the treatment of ulcerative colitis (UC). While the FDA sent Lilly a complete response letter detailing issues pertaining to the proposed manufacturing of mirikizumab, the regulator raised no concerns about the clinical data package or label for the medicine. The recent setback dents mirikizumab’s chances to be the first among the IL-23 inhibitors to launch in the US for UC.

Anti-interleukin therapies are generally prescribed as second-line or third-line treatment in UC patients who have failed a biological drug. While Janssen’s Stelara is currently the only approved anti-interleukin therapy approved for UC in the US, this therapy’s mechanism of action, targeting both IL-12 and IL-23, means it is associated with a higher risk of immunosuppression compared to selective IL-23 inhibitor agents such as mirikizumab. The selective inhibition of the latter set of agents is seen as a key advantage over Stelara, and one that will help these agents to differentiate themselves in the crowded biologics space for UC. Other anti-IL-23 agents that are in late-stage development for UC include AbbVie’s Skyrizi (ustekinumab), Janssen’s Tremfya (guselkumab), and Boehringer Ingelheim’s Spevigo (spesolimab).