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P508 Association between clinical outcome and post induction CT-P13 trough levels at week 14, in patients with inflammatory bowel disease. Preliminary results in an observational multicentric study

Elosua González A.*1, Oyόn Lara D.1, Nantes Castillejo Ó.1, Ogueta Fernández M.Ά.2, Gutiérrez Mendizábal P.3, Muñoz Villafranca M.C.3, Gόmez Irwin L.4, Muñagorri Santos A.I.5, Rodríguez Lago I.6, Rodríguez Gutiérrez C.1 IBD Study Group from the Basque-Navarre Society of Gastrointestinal Diseases

1Complejo Hospitalario de Navarra, Gastroenterology, Pamplona, Spain 2Hospital Universitario Araba, Gastroenterology, Vitoria, Spain 3Hospital Universitario Basurto, Gastroenterology, Bilbao, Spain 4Hospital Universitario Cruces, Gastroenterology, Barakaldo, Spain 5Hospital Universitario Donostia, Gastroenterology, San Sebastián, Spain 6Hospital Galdakao-Usansolo, Gastroenterology, Usansolo, Spain

Background

CT-P13 became the first Infliximab (IFX) biosimilar approved for the treatment of Inflammatory Bowel Disease (IBD) in 2013. Measurement of IFX trough levels has been suggested as a new approach to tailor the therapy. Few studies have evaluated in clinical practice the relationship between primary failure after induction therapy (10–30%) and trough levels of CT-P13. Our aim is to evaluate the usefulness of systematically testing trough levels of CT-P13 at week 14.

Methods

We conducted a multicentric observational study including all adult patients with IBD treated with CT-P13, excluding patients on CT-P13 to prevent post-surgical recurrence. Induction dose was 5mg/kg at week 0, 2 and 6. Trough levels were measured in week 14 using enzyme-linked immunoabsorbent assay (ELISA) (Promonitor-IFX; Progenika Biopharma®). In Crohn's Disease (CD) a decrease ≥3 points in Harvey-Bradshaw index (HBI) was considered partial response (PR) and a HBI lower than 5 was considered clinical remission (CR). In Ulcerative Colitis (UC) a decrease ≥3 points in Partial Mayo Index (MI) was considered PR and CR was a MI lower than 3.

Results

We included 80 patients with a median age of 47.55±13.6 (62.7% males). CD patients (49) had a basal HBI of 7.88±4.01. UC patients (31) had a basal MI of 6.55±2.11. Patients had previous treatment with antiTNF drugs in 38.5%, and 83.1% with immunomodulators (IMM). We associated IMM to CT-P13 in 59% of our patients.

Median trough levels at week 14 were 4.36 (CD 4.04 and UC 4.85). No differences were found between patients with concomitant IMM (4.40) or without it (4.31); naïve (3.97) and no naïve anti-TNF patients (5.07).

Postinduction trough levels in patients with NR were 2.897, PR 4.57 and CR 4.87. Patients with primary failure presented lower CT-P13 trough levels compared with patients in CR, although no statistical significance was found (p=0.539).

Considering less than 3μg/ml as infratherapeutic, only 39.7% of patients reached therapeutic levels (36.3% CD, 44.8% UC). NR had 33.3% of patients (CD = UC), PR 48% of patients (41.6% CD, 43.85% UC) and CR 36.3% (36.3% CD and 40% UC).

Conclusion

The median CT-P13 trough level in week 14 was 4.36 μg/ml. No statistically significant differences were found between CD/UC, naïve/not naive to antiTNF therapy.

Association of inmunomodulators did not increased CT-P13 postinduction levels.

Up to 60% of patients had infratherapeutic (<3μg) CT-P13 postinduction levels.

There were no statistically significant differences between therapeutic or infratherapeutic levels and clinical response at week 14.