P1070PCDAI eligibility criteria into clinical trials: Post-hoc analysis of the UNITI Jr study of ustekinumab in paediatric Crohn’s Disease (CD)

Abstract Background The PCDAI is the multi-item measure most commonly used to assess baseline activity for entry into paediatric CD trials. A PCDAI cutoff score 30 is recommended by regulators for identifying moderately-to-severely active disease.(1) Initial validation of the cut-off score (2,3) prioritized independent association of the PCDAI and CDAI with the purported gold standard of “physician global assessment”. Here we revisit the suitability of this threshold, with an emphasis on equity with adult studies in order to ensure that PCDAI eligibility criteria represent the same severity of disease as the adult reference population, which uses a CDAI cutoff of 220. The objective of this post-hoc analysis was to determine the PCDAI threshold that correlates best with a CDAI threshold of 220. Methods Pooled baseline and post-baseline daily diary PCDAI and CDAI data from 79 patients aged 2 to 18 years in the UNITI Jr study (NCT04673357; single open-label IV ustekinumab induction dose followed by blinded SC ustekinumab maintenance therapy Q8W/Q12W for 44-weeks) were analyzed. Spearman rank correlations and Gwet’s coefficient were computed. Cluster bootstrapping was used to account for within-patient correlations. Results Strong correlation between the diary PCDAI and CDAI scores was demonstrated, Spearman correlation coefficient (95% CI) = 0.80 (0.73, 0.85)(Figure). A PCDAI score cutoff ≥25 in patients 2 to 18 years increased the agreement (Gwet’s coefficient 95% CI) with CDAI score ≥220 from 71% (60%, 82%) to 76% (66%, 85%) compared with a PCDAI threshold ≥30. Conclusion This post-hoc analysis of the UNITI Jr trial provides evidence supporting inclusion of paediatric patients 2 to 18 years with moderately-to-severely active CD with a lowered threshold of PCDAI ≥25 (from ≥30). A PCDAI threshold of ≥ 25 with objective evidence of inflammation (centrally read SES-CD score) balances inclusivity and preserves the ability to detect a relevant change in disease activity. This approach could permit inclusion of children with clinically meaningful disease who would have been otherwise excluded from participation in paediatric CD trials. References: (1) US Food and Drug Administration. Pediatric Inflammatory Bowel Disease: Developing Drugs for Treatment Guidance for Industry. July 2024. Available at: https://www.fda.gov/regulatory-information/search-fda-guidance-documents/pediatric-inflammatory-bowel-disease-developing-drugs-treatment. Accessed 15 October 2025. (2) Hyams JS, Ferry G, Mandel FS, et al. Development and validation of a pediatric Crohn’s disease activity index. J Pediatr Gastroenterol Nutr. 1991;12:439-447. (3) Otley A, Loonen H, Parekh N, et al. Assessing activity of pediatric Crohn’s disease: which index to use? Gastroenterology. 1999;116(3):527-31. Conflict of interest: Prof. Russell, Richard K.: Grant: Nestec Other: Abbvie, Celltrion, Janssen, Lilly, Nestle, Pharmacosmos, Pfizer Received medical writing assistance funded by Johnson & Johnson Volger, Sheri: Employed by Johnson & Johnson Innovative medicine and have stock in the company Received medical writing assistance funded by Johnson & Johnson Griffiths, Anne: Grant: Nestec Other: Abbvie, Celltrion, Janssen, Lilly, Nestle, Pharmacosmos, Pfizer Received medical writing assistance funded by Johnson & Johnson Hyams, Jeffrey: Abbvie: Advisory Board Janssen: Advisory Board Roche/Genentech: Consultant Takeda: Consultant Received medical writing assistance funded by Johnson & Johnson De Greef, Elisabeth: Advisory Board Johnson & Johnson. Received medical writing assistance funded by Johnson & Johnson. Fieo, Robert: Employee of Janssen Pharmaceuticals/Johnson & Johnson Received medical writing assistance funded by Johnson & Johnson Strauss, Richard: Employee of Johnson & Johnson and may own stock/have stock options in the company. Received medical writing assistance funded by Johnson & Johnson. Kim, Lilianne: I’m an employee of Johnson and Johnson Innovative Medicine and I hold stocks in the company Received medical writing assistance funded by Johnson & Johnson Gaddah, Auguste: I’m an employee of Johnson & Johnson and hold stock or stock options in Johnson & Johnson Received medical writing assistance funded by Johnson & Johnson Hemperly, Amy: Employed by Johnson & Johnson and owns stocks and/or stock options Received medical writing assistance funded by Johnson & Johnson