AstraZeneca PLC / Allergan plc

Crohn's Disease and Ulcerative Colitis

Disease Overview

Crohn's disease is a chronic transmural inflammatory bowel disease that can affect any segment of the GI tract, causing pain, diarrhea, fistulae, strictures, and surgery. Ulcerative colitis is a related IBD limited to colonic mucosa. Both have rising US prevalence and are managed across a step-up of mesalamines, immunomodulators, and biologics, but a meaningful share of patients fail or lose response to currently available therapies.

Competitive Landscape

At deal time (Oct 2016), the IBD biologic market was dominated by anti-TNFs—AbbVie's Humira (adalimumab), J&J's Remicade (infliximab), and Takeda's Entyvio (vedolizumab, anti-α4β7)—plus J&J's Stelara (ustekinumab, anti-IL-12/23 p40), which was approved in Crohn's in September 2016, just weeks before the AstraZeneca-Allergan deal. The bet on MEDI2070/brazikumab was that selective IL-23p19 inhibition would beat IL-12/23 dual blockade by sparing IL-12-driven Th1 immunity, mirroring the psoriasis trajectory where IL-23p19 agents (Tremfya, Skyrizi) outclassed Stelara. Allergan publicly framed brazikumab as a potential first-in-class oral-naive biologic franchise. However, the IL-23p19 race rapidly crowded with AbbVie's Skyrizi (risankizumab) and Eli Lilly's Omvoh (mirikizumab), both of which beat brazikumab to approval in IBD. Allergan returned global rights to AstraZeneca in 2020 to clear FTC concerns ahead of the AbbVie-Allergan merger; Jefferies described the recovered asset as 'essentially a free new pipeline option' for AstraZeneca. AstraZeneca later discontinued brazikumab in 2023 citing competitive landscape and timeline disadvantage.