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sof choice for preventing early colectomy. Severe endoscopic lesions appears to be predictorof short- and long-term colectomy.

Sa1233

TNF-α Levels Strongly Correlated With Disease Activity Based on HBI andCDEIS in Patients With Crohn's Disease in Maintenance Treatment WithAdalimumabGiorgia Bodini, Vincenzo Savarino, Pietro Dulbecco, Isabella Baldissarro, EdoardoSavarino

Introduction: In the last two decades the therapeutic paradigm of Crohn's disease (CD) haschanged dramatically thanks to the use of biological drugs. In this scenario, we must considerthe pivotal role of tumor necrosis factor-alpha (TNF-α), a pro-inflammatory cytokine, inthe pathogenesis and relapse of CD. High levels of TNF-α have been associated with thedevelopment of intestinal inflammation in CD and blocking this cytokine with anti-TNF-αmolecules may result in mucosal healing. In addition several studies have shown increasedTNF-α levels in the serum and in the intestinal mucosa of patients with CD. However, littleis known about the course of TNF-α levels and their relationship with disease recurrencein CD patients during maintenance treatment with Adalimumab. Aim: We assessed TNF-αlevels in patients with CD who were in maintenance treatment with ADA and correlatedthem with clinical and endoscopic disease activity. Methods: In this prospective observationalcohort study, performed at a single tertiary referral center, 23 [14M/9F; mean age 41 (range21-66) infliximab-Naive patients with CD in maintenance treatment with ADA were includedand followed-up. Blood samples were drawn at standardized time points (i.e. at 6, 12, 18,24 months and in case of CD relapse) just before ADA injection. Antibodies against ADA(AAA) were measured using an homogenous mobility shift assay (HMSA; Prometheus Lab,San Diego, United States). Blood samples were considered positive for AAA presence if ≥1.7U/mL. Disease activity was assessed at the same points by means of the Harvey-BradshawIndex (HBI, remission <5, mild disease 5-7, moderate disease 8-16, severe disease >16).Moreover, endoscopic activity was assessed at baseline and at the time of relapse by meansof CD endoscopic index (CDEIS<6 endoscopic remission, a decrease >5 responder, CDEIS<3complete endoscopic remission and mucosal healing). Results: We have data from 133 bloodsamples. AAA were observed in 26/133 (19.5%) samples, and 10/26 (38.5%) had a valueof AAA ≥1.7 U/mL. TNF-α levels were present in all samples assessed (Mean 4.4, range 0-27.2). As shown in the figure, per-patient median TNF-α levels were strongly correlatedwith median HBI scores (r2=0.702, p<0.0001). Moreover, TNF levels were also correlatedwith CDEIS (r2=0.350, p=0.001). Conclusion: TNF-α levels strongly correlated with diseaseactivity based on HBI and CDEIS indices in patients with CD in maintenance treatmentwith ADA. Indeed, moderate to severe patients often have high sustained TNF-α levels.

Sa1234

RNA-Seq Derived Whole Blood Gene Expression Signature As a Biomarker forDifferential Diagnosis and Intestinal Inflammation in Inflammatory BowelDiseaseDavid Kevans, Boyko Kabakchiev, Judy Qiang, Joanne M. Stempak, Ken Croitoru,Geoffrey C. Nguyen, A. Hillary Steinhart, Mark S. Silverberg

Background: Assessment of intestinal inflammatory activity in ulcerative colitis (UC) andCrohn's Disease (CD) is based on clinical evaluation, determination of biochemical markersof inflammation and endoscopic observation. C-reactive protein (CRP) is the most commonlyused inflammatory biomarker however its sensitivity and specificity is limited particularlyin UC. There is a need for new biomarkers which accurately reflect intestinal inflammationin inflammatory bowel disease (IBD). We aimed to evaluate the potential of a whole bloodgene expression signature as a proxy of intestinal inflammation and a biomarker for differentialdiagnosis. Methods: A cohort of 159 subjects with UC, CD, and healthy controls (HC) wasprospectively accrued. Ileocolonoscopy was performed on each subject and blood collectedfor CRP estimation. All included subjects had blood collected and stored in PAXgenetubes (Qiagen) on the day of endoscopy. Baseline demographic information, details of IBDphenotype, disease duration and medication use at the time of endoscopy were collected.Each endoscopy was reviewed and classified for the presence or absence of inflammation.Total RNA was extracted with the miRNeasy kit (Qiagen) and the transcriptomes weresequenced in paired-end runs on a HiSeq 2500 instrument (Illumina). Raw reads whichpassed quality control were aligned against the human genome (GRC37) with TopHat anddifferential gene expression was assessed with Cuffdiff from the package Cufflinks. Results:45 subjects with available RNA-Seq data were included in an initial analysis. CD and UCsubjects were generally minimally treated with no immunomodulator or biologic use. 5ASAand corticosteroids were used in 18% & 9% of CD vs. 74% & 0% of UC subjects respectively.Comparing CD, UC and HC, median CRP (mg/L) concentration was 3.9 [1 - 52], 2.0 [0 -75] and 1.0 [1 - 5] respectively. 216 genes were found to be differentially regulated betweenthe different phenotypic groups after correction for multiple testing. Of these, 110 wereexpressed differently in CD subjects compared to HC, 133 in UC compared to HC, and 62in CD compared to UC. 2 of these genes, IGJ and MZB1, were common to all three pairwisecomparisons. One gene, YAP1 not only exhibited differential expression in subjects withpresent versus absent endoscopic inflammation, but also proved more predictive of endo-scopic inflammation than CRP; OR=0.066, (CI=[0.013;0.343]) vs. OR=1.118, (CI=[0.962;1.299]) respectively. Conclusion: A gene expression signature in whole blood correlatedsignificantly with IBD phenotypes and endoscopically assessed mucosal inflammation. Wholeblood gene expression profiling has value as an adjunctive biomarker of endoscopic inflamma-tion in IBD and may help identify IBD patients with a high burden of intestinal inflammation.Replication of these initial findings is underway.

S-238AGA Abstracts

Sa1235

PKM2 As a Novel Serum Biomarker of IBD Activity, A Early Pilot StudyRomela Marin, Hamed Khalili, Ashwin N. Ananthakrishnan, Jenny Sauk, Vijay Yajnik,Nitin Gupta, Ramnik J. Xavier, Deanna D. Nguyen

Background: Disease activity monitoring in IBD often requires radiologic imaging and/orendoscopic examination since serum levels of C-reactive protein (CRP) and erythrocytesedimentation rate (ESR) are not always elevated in patients with active disease. Fecalbiomarkers such as calprotectin or lactoferrin lack the convenience of a blood test. Pyruvatekinase (PK) is a key enzyme in glycolysis with the M2 isoform expressed in rapidly dividingcells, often found to be elevated in cancer and thought to play a key role in cancer metabolismreprogramming. There have been several reports of elevated PKM2 concentrations in thestool in IBD. Aim: We sought to identify a more reliable and easily attainable biomarker ofIBD activity. Methods: Serum from patients enrolled in PRISM (Prospective Registry of IBDStudy at MGH) at the MGH Crohn's and Colitis Center were assayed for PKM2 level usinga commercially available ELISA kit. Three sets of patients were included in the assay: a)three patients for whom samples were available during active and inactive states, b) sixpatients for whom serum was available only during active or inactive state (or those whereboth were available but we only used the active sample for comparison), and c) one patientwho had samples collected at times of different symptom severity (as measured by prednisonedoses). As a positive control, we also included one sample from a patient with knownmetastatic colon cancer. Active disease was defined as current use of prednisone, physicianglobal assessment deeming suboptimal symptom control, active disease on endoscopic evalua-tion, or simple colitis activity index (SCAI) ≥ 3, whichever was available. Results: We foundsignificantly higher serum PKM2 levels in patients with active disease compared to thosewith inactive disease (Figure 1a). Among three patients who had serum collected duringactive and inactive states, using pair-wise comparision, we found a trend for elevation inserum PKM2 levels during a flare (Figure 1b). Finally, in one patient with measurementstaken during several periods of active disease, serum PKM2 levels correlated with doseadministration of prednisone, a marker of symptom severity. Spearman rank correlationbetween serum PKM2 and CRP levels was 0.674 (n = 12). Interestingly, the PKM2 levelsfound in patients with active colitis were at the same scale as that found in the positivecontrol sample of a patient with known metastatic colon cancer (134.7 U/ml). Conclusions:Serum PKM2 levels appear to be a reliable biomarker of IBD activity. Larger scale testingwill be required to confirm these preliminary results.

Sa1236

Antibodies Against Infliximab Are Associated With Increased Risk of Anti-Adalimumab Antibody Development in Patients With Inflammatory BowelDiseaseMadeline T. Frederiksen, Mark A. Ainsworth, Jorn Brynskov, Ole . Thomsen, KlausBendtzen, Casper Steenholdt

Background: Infliximab (IFX) is effective for treatment of inflammatory bowel disease (IBD),but a notable proportion of patients relapse despite dose-optimization. In these patients, itis recommended to change to a second TNF-inhibitor such as adalimumab (ADL). However,there is considerable variation in the response to ADL after switching, and factors influencingoutcomes are largely unknown. As development of anti-IFX antibodies (Abs) is a potentialcause for IFX failure, we investigated if patients with anti-IFX Abs are prone to developantibodies to ADL after switching therapy. Methods: Observational, retrospective, single-center cohort study of all IBD patients treated with IFX or ADL (n=482). Anti-IFX Abs,including cross-reactivity with ADL, anti-ADL Abs, and drug concentrations in serum weremeasured by clinically validated radioimmunoassay. Results: Anti-IFX Abs were assessed in189 patients (n=131Crohn's disease; n=58 ulcerative colitis) treated with IFX as first lineanti-TNF agent. Approximately half the patients (49%) were tested anti-IFX Ab positive(median 59 U/ml, IQR 26-97). Anti-IFX Abs appeared to be functional as they reduced theIFX serum levels of anti-IFX Ab positive patients: median 0.0 μg/ml, IQR 0-0 vs. 1.8 μg/ml, IQR 0.9-4.6 in anti-IFX Ab negative patients, p=0.002. Anti-IFX Abs did not cross-reactwith ADL (n=41 assessed). The treatment was changed to ADL in 66 patients with anti-IFXAbs and in 25 patients without anti-IFX Abs. Patients with previous anti-IFX Ab developmentwere significantly more prone to develop anti-ADL Abs (10/29 patients: 34%) than thosewithout previous anti-IFX Ab development (0/12 patients: 0%); OR estimated 13, p=0.02.Detected anti-ADL Abs correlated with reduced blood levels of ADL in all cases: median0.0 μg/ml, IQR 0-0 vs. 9.2 μg/ml, IQR 6.2-11.6 in anti-ADL Ab negative patients, p=0.017.Conclusion: Antibodies against IFX are highly drug specific and do not cross-react withADL, thus making switching from IFX to ADL safe even in the presence of anti-IFX Abs.However, compared to patients without anti-IFX Abs, patients who develop anti-IFX Absduring previous IFX therapy have a higher risk of developing specific and functional anti-ADL Abs.