Prospective Observational Evaluation of the Time-Dependency of Adalimumab Immunogenicity and Drug Concentration in Ulcerative Colitis Patients: the POETIC II Study.

BACKGROUND AND AIMS: Home self-injection of the human anti-tumour necrosis alpha [anti-TNFα] monoclonal adalimumab complicates prospective serial-sampling studies. Although a recent study examined adalimumab levels and immunogenicity in Crohn's disease [CD] patients, prospective real-world data from ulcerative colitis [UC] patients are lacking. METHODS: A three-monthly home-visit programme from induction was established prospectively for UC patients. Clinical scores were determined at each visit, and sera were obtained for assessment of drug and anti-adalimumab antibody levels. Calprotectin was measured using a smartphone-based app. This cohort was compared to a parallel prospective cohort of adalimumab-treated CD patients [POETIC1]. RESULTS: Fifty UC patients starting adalimumab [median follow-up 28 weeks] were compared to 98 adalimumab-treated CD patients [median follow-up 44 weeks]. Only 11/50 UC patients [22%] continued treatment to the end of the follow-up compared with 50/98 [51%] CD patients (odds ratio [OR] = 0.27, p = 0.001). Loss of response was significantly more common in UC patients [OR = 3.2, p = 0.001]. Seventeen patients [34%] in the UC cohort developed anti-adalimumab antibodies, 9/17 [52.9%] as early as week 2. There was no difference between patient cohorts in the overall development of anti-adalimumab antibodies [34% vs 30.6%, respectively, OR = 1.67, p = 0.67], nor was there a difference in early immunogenicity [OR = 1.39, p = 0.35]. There was no difference in low drug levels [<3 µg/mL] between the two cohorts [OR = 0.87, p = 0.83]. CONCLUSIONS: Loss of response to adalimumab therapy was significantly more common in the UC compared to the CD cohort and was driven by a higher rate of non-immunogenic, pharmacodynamic parameters.