AstraZeneca PLC / Allergan plc

Crohn's Disease & Ulcerative Colitis (Anti-IL-23 Biologic)

70K US cases/yr · $18.5B U.S. IBD biologics market 2022 · ~$80,000 WAC per patient/year for branded IBD biologics

Disease Overview

Crohn's disease (CD) and ulcerative colitis (UC) are the two principal forms of inflammatory bowel disease (IBD), each affecting roughly 1.6 million Americans combined with approximately 70,000 new IBD diagnoses per year in the U.S. Crohn's is a transmural inflammation of any segment of the GI tract presenting with abdominal pain, diarrhea, fistulae, and strictures; UC is restricted to colonic mucosa and submucosa with bloody diarrhea and tenesmus. Both diseases follow a relapsing-remitting course with substantial morbidity, hospitalization burden, and surgical risk (approximately 20-30% of CD patients require bowel resection within 10 years). The IL-23/Th17 axis is now validated as a central driver of mucosal inflammation in IBD, with selective IL-23p19 antagonism delivering superior endoscopic remission relative to anti-IL-12/23 antagonism. The U.S. IBD biologics market is dominated by anti-TNF agents (Humira/Remicade biosimilars), anti-integrin vedolizumab, and the IL-23 class. WAC pricing for branded IBD biologics ranges $50,000-$80,000 per patient per year and roughly half of patients cycle through 2-3 biologics due to primary or secondary loss of response.

Competitive Landscape

The IBD competitive landscape has shifted decisively toward selective anti-IL-23p19 antagonism. Skyrizi (risankizumab, AbbVie) is the franchise leader following positive Phase 3 ADVANCE/MOTIVATE in CD and FDA approval mid-2022, with UC approvals projected 2024. Stelara (ustekinumab, J&J) is the entrenched anti-IL-12/23p40 incumbent across both indications and is now facing biosimilar erosion. Tremfya (guselkumab, J&J) reads out positive Phase 3 GALAXI/QUASAR data in CD/UC. Mirikizumab (Lilly) won FDA approval in UC in October 2023 (Omvoh) and has CD Phase 3 data pending. Brazikumab (anti-IL-23p19, AstraZeneca) had advanced Phase 2b/3 INTREPID in CD before development was discontinued in 2021 after Lilly's mirikizumab interim showed competitive depth-of-response advantage. Other modalities include Entyvio (vedolizumab, anti-α4β7 integrin, Takeda), Xeljanz/Rinvoq JAK inhibitors (Pfizer/AbbVie), and Zeposia (S1P modulator, Bristol Myers). The brazikumab divestiture from AbbVie/Allergan to AstraZeneca was a regulatory antitrust unwind tied to AbbVie's Skyrizi conflict, not a value-creating commercial repositioning.