Background. The most important goals of the recent therapies of inflammatory bowel disease (IBD) are to induce and maintain clinical remission and mucosal healing (MH), which can be achieved with anti-TNF-α biological therapy. CT-P13 is the first biosimilar to infliximab (IFX) that has been approved for the same indications as its originator IFX, but no data was available on the effect of IFX biosimilar on mucosal healing. Serum IFX and antibody-to-infliximab (ATI) levels are objective parameters, that may have a great role in the therapeutic decisions during maintenance biological therapy in the use of original and biosimilar agents. The aims of this thesis were, to evaluate (I) the correlation between clinical and endoscopic disease activities of UC defined by activity scores. (II) the efficacy of CT-P13 induction therapy, (III) to assess the correlation between serum IFX and ATI levels, the response to IFX therapy, and to determine the accuracy of serum drug concentration measurement in the prediction of the long-term clinical response. The last part of this thesis evaluates (IV) the diagnostic accuracy of different fecal markers in the detection of colorectal adenomas and cancer. Biomarkers are important in not only studying IBD, but may be important in colorectal cancer (CRC) as well. As CRC is the second deadliest malignancy worldwide, the simple and early detection methods are critical for theeffective management of this disease. Methods Clinical and endoscopic activities were evaluated in 100 consecutive UC patients. Clinical activities were defined by two activity indices: the Rachmilewitz Activity Index (CAI) and the partial Mayo score. They graded the findings both according to the endoscopic part of the Rachmilewitz Endoscopic Activity Index (EI) and the Mayo endoscopic subscore. MH was defined as Mayo endoscopic subscore and EI of 0. Histological activity was scored by the Riley score. Sixty-three UC patients who underwent CT-P13 induction therapy were enrolled in the second study. Sigmoidoscopy was performed after the end of the induction therapy at week 14. Mucosal healing was defined as Mayo endoscopic subscore 0 or 1. Complete mucosal healing was defined as Mayo endoscopic subscore 0. Trough level (TL) of CT-P13 was measured at week 14. Fourty-eight IBD patients receiving maintenance IFX therapy were prospectively enrolled and divided into adequate and inadequate groups. Blood samples were collected just before (trough level) and two (W2aTL) and six weeks (W6aTL) after the administration of IFX. Stool samples of patients referred to colonoscopy were collected, from 95 non-IBD patients, for the analysis of tumor M2 pyruvate kinase (M2PK), human hemoglobin (Hb), hemoglobin/haptoglobin (Hb/Hp) complex, fecal calprotectin (FC), and matrix metalloproteinase-9 (MMP-9). Results Clinical and endoscopic activities showed strong correlations using both scoring systems (p = 0.0029 and p = 0.0001). Endoscopic disease activity also correlated with the histological activity (p 1 cm were 60% and 67.5% and for CRC were 94.7% and 67.5%. Sensitivity and specificity of iFOBT for adenomas sized ≥ 1 cm were 80% and 72.5% and for CRC were 94.7% and 72.5%. Sensitivity and specificity of Hb/Hp complex for adenomas sized≥ 1 cm were 80% and 52.9% and for CRC were 100% and 52.9%. Sensitivity of FC andMMP-9 for CRC was 77.8% and 72.2%. Combined use ofM2PK, iFOBT, and FC resulted in a sensitivity and specificity of 95% and 47.5% for the detection of adenomas sized ≥ 1 cm. Conclusion Assessment of MH is very important for guiding therapy and for the evaluation of remission in patients with UC..
