Diagnostic delay in IBD is common. Why patients wait so long before seeking help is unclear. We hypothesise that direct to public calprotectin testing linked to definitive secondary care assessment for patients with positive results will reduce diagnostic delay. To establish a baseline, prior to direct-to-public stool testing pilot, we undertook a prospective cohort study using patient reported outcomes to define time to IBD diagnosis and the demographic, disease-related and psychological factors associated with a delay. Delay was defined as greater than a year between symptom onset and secondary care contact and included time from symptom onset to first primary care contact (patient delay), first primary care contact to referral (primary care delay) and referral to diagnosis (secondary care delay). Depression, anxiety and fatigue were assessed using the Patient Health Questionnaire-8, General Anxiety Disorder-7 and IBD-fatigue respectively. A word cloud was generated from 185 responses to: “What, if anything, caused a delay in your IBD diagnosis?”. We used backwards stepwise regression to determine which factors to include in our final models. We included 192 patients (92 female, mean age 45 yrs) diagnosed with IBD between June 2024 and September 2025. The median [IQR] interval between diagnosis and survey completion was 22 [10-58] days. 34% (49/144) and 58% (28/48) patients experienced delay to diagnosis of ulcerative colitis (UC) or IBD unclassified and Crohn’s disease (CD) respectively. The largest component of overall delay was patient delay (Fig 1). Factors associated with overall delay were CD diagnosis (0.23 = p0.004), male sex (-0.15 p = 0.031), symptoms of IBS (0.17 p = 0.035) and embarrassment (0.19 p = 0.011). Within disease models, a history of IBS was associated with delay in CD and embarrassment in UC. PHQ-8 depression scores were associated with increased risk of diagnostic delay (p = 0.04), but this factor was not selected for the final model by the backwards regression process. Patient-reported symptom duration prior to referral was significantly longer than that captured in primary care referral letters (median difference 4.8 weeks p < 0.001). The prominence of GP in our word-cloud (Fig2) was due to positive (24) and negative (37) comments related to GP services, as well as reluctance to go to the GP (41). Using patient reported symptom duration, more than a third of people living with IBD experience a delay to diagnosis of more than a year. Male sex, embarrassment and a history of IBS were associated with delay to diagnosis. Novel strategies to reduce the time to diagnosis of IBD, including direct-to-public stool testing, may help overcome embarrassment and reduce patient-related delay Reference: 1. Walker, GJ, Lin, S, Chanchlani, N, et al. Quality improvement project identifies factors associated with delay in IBD diagnosis. Aliment Pharmacol Ther. 2020; 52: 471– 480. https://doi.org/10.1111/apt.15885 2. Jayasooriya, N, Baillie, S, Blackwell, J, Bottle, A, Petersen, I, Creese, H, et al., POP-IBD study group. Systematic review with meta-analysis: Time to diagnosis and the impact of delayed diagnosis on clinical outcomes in inflammatory bowel disease. Aliment Pharmacol Ther. 2023; 57: 635– 652. https://doi.org/10.1111/apt.17370 Conflict of interest: Dr. Smith, Rebecca: No conflict of interest Cairnes, Vida: No conflict of interest Bishara, Maria: No conflict of interest Roberts, Christopher: Funding of research: Nova Ltd, Open Targets Odeh, Safwat: No conflict of interest Vine, Jordan: No conflict of interest Nice, Rachel: No conflict of interest Hodges, Phoebe: No conflict of interest Badrulhisham, Fakhirah: No conflict of interest Bewshea, Claire: No conflict of interest McDonald, Tim: No conflict of interest Pollok, Richard: I have no potential Conflict of Interest in the past 3 years including grants, honoraria, shares, paid positions, advisory boards, personal fees or non-financial support Rimmer, Peter: I have received research funding from F. Hoffman La Roche. I have received educational grants from Abbvie and Johnson & Johnson. I have received speaker fees from Abbvie, Ferring, Johnson & Johnson and Takeda. Appleby, Richard: No conflict of interest Kennedy, Nicholas Alexander: Grant: Dr Kennedy’s department has received research funding from AbbVie, Biogen, Celgene, Celtrion, Galapagos, MSD, Napp, Pfizer, Pharmacosmos, Roche and Takeda Personal Fees: Dr Kennedy has served as a speaker and/or advisory board member for AbbVie, Amgen, BMS, Falk, Ferring, Galapagos, Janssen, Mylan, Pharmacosmos, Sandoz, Takeda and Tillotts Non-financial Support: Dr Kennedy has had support to attend meetings from AbbVie, Falk, Janssen and Tillotts Goodhand, James Ross: No conflict of interest Ahmad, Tariq: Tariq Ahmad reports grants, personal fees and non-financial support from F. Hoffmann-La Roche AG, Biogen Inc, Abbvie, Janssen, Celltrion Healthcare, Galapagos NV, Immundiagnostik, Takeda, ARENA, Gilead, Adcock Ingram Healthcare, Pfizer, Genentech, Tillotts.

Abstract Background The longest component of the time-to-diagnosis is the interval between symptom onset and an individual seeking help. Recent reports in patients with sexually transmitted infections and hepatitis C, who also suffer health related stigma and a delay in diagnosis, suggest that this barrier may be overcome by the anonymity of direct-to-public testing. We sought to characterise the availability of online direct-to-public calprotectin testing in 2023 in the UK. Methods We undertook an online search using the Google search engine on May 25th, 2023, with the terms "buy" or "purchase" AND "calprotectin" AND "inflammatory bowel disease". Collection kits were procured, and stool samples tested to receive follow-up advice for known positive and negative stool samples. We recorded data regarding the assay, consumer information and the clinical advice offered on return of a positive and negative test. Results Overall, 54.5% (6/11) of available tests were home lateral flow tests, the remainder were home collection laboratory-based tests. Of the laboratory-based tests, three were conventional enzyme-linked immunosorbent assay (ELISA) assays and two were OC sensor tests. The lateral flow tests were considerably cheaper than the laboratory-based tests (median cost £14.20 [£7.85-21.00] vs £75.85 [£59-151], p<0.0001). The median turnaround time for the laboratory tests was 14 (1-23) days. All but one provider used a positivity threshold of 50ug/g. Eight of the eleven platforms (4 lateral flow tests and 4 laboratory-based tests) explicitly stipulated testing in the setting of gastrointestinal symptoms or suggested exclusion criteria. All tests included written and pictorial instructions with the testing kit. The median Flesch Kincaid readability score for the instructions and result reporting were 54.3 (43.9-73.7) and 51.8 (12.9-64.9): equivalent to a school reading grade of 9.2 (6.2-10.8) and 11.3 (7.2-15.8), respectively. Only two of the lateral flow tests provided written recommendations about follow up of positive results, whereas amongst the laboratory-based tests, all but one provider recommended onward discussion with a general practitioner or specialist. Two providers offered private referrals or consultations and six provided safety netting advice with regards to negative results. Conclusion In the UK online direct-to-public calprotectin testing is already readily available from multiple providers. Consumers can choose between home-based lateral flow tests or conventional laboratory testing. Further work is needed to redefine the diagnostic accuracy of calprotectin used in this way, however, the rapid turnaround times and anonymity suggest that direct-to-public calprotectin testing could be used to reduce the time to IBD diagnosis.

Abstract Background In conventional laboratory-based Enzyme Linked Immunosorbant Assays (ELISA) for calprotectin measurement, raw stool is returned to and manually processed by testing laboratories. The OCS-Pledia calprotectin test uses the same stool collection device as the OCS-Pledia FIT test used in the UK Bowel cancer screening programme. In brief, individuals sample their stool with a picker and transfer to a preprepared buffered diluent, which is then returned to the laboratory for fully automated analysis. We have previously shown that a stool concentration of >100ug/g measured using the IDK calprotectin ELISA was the optimal cut-off to distinguish IBS from IBD (sensitivity 86%, specificity 90%, positive predictive value 39%, negative predictive value 99%). We undertook a methods comparison study to report the stability, linearity and potential bias of the OCS-Pledia calprotectin assay compared with IDK ELISA. Methods 32 stool samples were collected from people with GI pathology, and homogenised. Samples were prepared for calprotectin testing using IDK and OCS-Pledia less than 4 hours from excretion (mean2.6 [SD]1.3 hrs). Samples were left at room temperature and further extracts taken at 6, 24, 48, 72, and 168 hours. Pairwise analysis of samples across the reporting range was undertaken and linearity and bias assayed by Pearson’s correlation and Bland-Altmann analysis, respectively. Results Calprotectin was stable over one week in both the OCS-Pledia buffered and the IDK ELISA unbuffered stool samples. However, OCS-Pledia results showed lower variance than that of the IDK ELISA, especially at later time points. There was a linear relationship between calprotectin measured with the OCS-Pledia and IDK-ELISA assays (R2=0.85; p<0.0001). The OCS-Pledia calprotectin assay has a positive bias across the reporting range. This led to 40 samples reading elevated calprotectin levels on OCS-Pledia but within normal range on IDK-ELISA. All 40 had colonic inflammation and therefore were false negative IDK-ELISA. Calprotectin concentrations of 600ug/g and 400ug/g measured using the OCS-Pledia assay were equivalent to concentrations of about 250ug/g and 100ug/g measured using the IDK ELISA. Conclusion OCS- Pledia assays for the measurement of calprotectin are likely to superseded conventional ELISAs because they are cheaper, easier to automate and do not involve laboratory staff pre-processing stool samples. Like conventional ELISA assays calprotectin is stable for at least one week. Clinicians will need to be aware, however, of the positive bias across the reporting range of calprotectin and adjust their positivity thresholds.

Abstract Background Anti-tumour necrosis factor drugs such as infliximab are associated with attenuated antibody responses after COVID-19 vaccination. It is unknown how infliximab impacts vaccine-induced serological responses against highly transmissible Omicron variants, which possess the ability to evade host immunity and are now the dominating variants causing current waves of infection. Methods In this prospective, multicentre, observational cohort study, we investigated neutralising antibody responses against SARS-CoV-2 wild-type and Omicron BA.1 and BA.4/5 variants after three doses of COVID-19 vaccination in 1288 patients with IBD without prior COVID-19 infection, who were established on either infliximab (n=871) or vedolizumab (n=417). Cox proportional hazards models were constructed to investigate the risk of breakthrough infection in relation to neutralising antibody titres. Results Following three doses of COVID-19 vaccine, neutralising titre NT50 (half-inhibitory neutralising titre) was significantly diminished in patients treated with infliximab as compared to patients treated with vedolizumab, against wild-type, BA.1 and BA.4/5 variants (Fig 1). Patients with Crohn’s disease showed lower antibody NT50 compared to patients with ulcerative colitis against wild-type strain and BA.4/5 (Fig 2). Older age and thiopurine were independently associated with lower NT50 against wild-type strain and BA.4/5 (Fig 2). Non-white ethnicity was associated with higher NT50 compared to white ethnicity against wild-type strain, BA.1 and BA.4/5 (Fig 2). Breakthrough infection was significantly more frequent in patients treated with infliximab compared to patients treated with vedolizumab (Fig 3). Cox proportional hazards models of time to breakthrough infection after the third dose showed infliximab treatment to be associated with a higher hazard risk (HR) of 1.71 (95% CI [1.08 to 2.71], p=0.022) compared to vedolizumab (Fig 4). Higher neutralising antibody titres against BA.4/5 were associated with a lower hazard risk and a longer time to breakthrough infection (HR 0.87 [0.79 to 0.95] p=0.0028) (Fig 4). Conclusion Following a third COVID-19 vaccine dose, patients established on infliximab treatment have significantly lower neutralising titres against SARS-CoV-2, which were especially low against Omicron variants. Increased breakthrough infection in infliximab recipients was associated with lower neutralising antibody titres against BA.4/5. These data underline the importance of continued COVID-19 vaccination programs, including second-generation bivalent vaccines, especially in patient subgroups where vaccine immunogenicity and efficacy may be reduced.

Introduction Anti-TNF drugs impair serological responses following SARS-CoV-2 infection and vaccination; strategies to mitigate this effect are now required. Vitamin D has a regulatory role in innate and adaptive immune processes and has been linked to poor SARS-CoV-2 infection outcomes and vaccine responses in some, but not all studies. We sought to assess whether 25-hydroxyvitamin D concentrations influenced serological responses to SARS-CoV-2 vaccine in infliximab-treated patients with IBD. Methods 1331 infliximab-treated patients who received a third dose of mRNA-based vaccine were identified from the impaCt of bioLogic therApy on saRs-cov-2 Infection and immuniTY (CLARITY) IBD study. 25-hydroxyvitamin D concentrations were measured in serum samples obtained prior to a third dose of SARS-CoV-2 vaccine, and cut-offs for vitamin D status were: deficiency < 25nmol/L, insufficiency 25–50nmol/L and sufficiency > 50nmol/L. The primary outcome was geometric mean anti-S RBD antibody concentration 2 to 10 weeks after a third dose of vaccine. Secondary outcome was pseudoneutralisation against SARS-CoV-2 wild-type and omicron subvariants BA.1 and BA.4/5 in 816 individuals without a prior SARS-CoV-2 infection. Results Baseline demographics of the cohort are shown in table 1. The median time from Vitamin D concentrations to a third dose of SARS-CoV-2 vaccine was 4.6 weeks [IQR 2.4 - 7.3]. Overall, 1.7% (23/1331) and 23.8% (317/1331) patients had vitamin D deficiency and insufficiency, respectively. Low pre-vaccination vitamin D concentrations were not associated with anti-S antibody responses following a third dose of vaccine, regardless of whether patients had a prior SARS-CoV-2 infection (3302 U/mL [9.8] vs 3931 U/mL [4.5]) or not (2440 U/mL [3.8] vs 1966 U/mL [4.7]). We observed a weak negative correlation between pre-third dose-vaccine vitamin D concentrations and pseudoneutralising activity against SARS-CoV-2 wild-type (R=-0.075, P=0.032) but not against omicron BA.1 or BA.4/5 variants. Conclusions In this proof of principle experiment we did not observe a relationship between vitamin D concentrations and post third dose booster anti-S RBD concentrations or pseudoneutralistation activity against the BA.1 or BA.4/5 variants.

Abstract Background and Aims Vitamin D has a regulatory role in innate and adaptive immune processes. Previous studies have reported that low pretreatment vitamin D concentrations are associated with primary non-response (PNR) and non-remission to anti-TNF therapy. This study aimed to assess whether pretreatment 25-hydroxyvitamin D concentrations predicted PNR and non-remission to infliximab and adalimumab in patients with active luminal Crohn’s disease. Methods 25-Hydroxyvitamin D concentrations were measured in stored baseline samples from 659 infliximab- and 448 adalimumab-treated patients in the Personalised Anti-TNF Therapy in Crohn’s disease (PANTS) study. Cut-offs for vitamin D were deficiency <25 nmol/L, insufficiency 25–50 nmol/L, and adequacy/sufficiency >50 nmol/L. Results About 17.1% (189/1107; 95% CI, 15.0–19.4) and 47.7% (528/1107; 95% CI, 44.8–50.6) of patients had vitamin D deficiency and insufficiency, respectively. 22.2% (246/1107) of patients were receiving vitamin D supplementation. Multivariable analysis confirmed that sampling during non-summer months, South Asian ethnicity, lower serum albumin concentrations, and non-treatment with vitamin D supplementation were independently associated with lower vitamin D concentrations. Pretreatment vitamin D status did not predict response or remission to anti-TNF therapy at week 14 (infliximab Ppnr = .89, adalimumab Ppnr = .18) or non-remission at week 54 (infliximab P = .13, adalimumab P = .58). Vitamin D deficiency was, however, associated with a longer time to immunogenicity in patients treated with infliximab, but not adalimumab. Conclusions Vitamin D deficiency is common in patients with active Crohn’s disease. Unlike previous studies, pretreatment vitamin D concentration did not predict PNR to anti-TNF treatment at week 14 or nonremission at week 54.

Abstract Background Lower serum free triiodothyronine-to-thyroxine (fT3/fT4) ratio has been linked to non-response to treatment in a range of diseases, including in biologic-treated patients with IBD. We sought to assess whether baseline serum fT3/fT4 ratio predicted primary non-response (PNR) and non-remission to infliximab and adalimumab in patients with Crohn’s disease. Methods We included 997 adult participants from the Personalised Anti-TNF Therapy in Crohn’s Disease study (PANTS). Thyroid function tests, using the Roche Elecsys TSH immunoassay and T3 and T4 electrochemiluminescence assays, were measured on stored baseline samples (prior to biologic treatment). PNR, assessed at week 14, was defined as treatment failure (including IBD-related surgery), ongoing corticosteroid use, or both CRP failing to fall to ≤3 mg/L, or by 50% from baseline, and HBI failing to fall to ≤4, or by 3 points. Non-remission, assessed at week 54, was defined as either CRP of > 3mg/L or HBI of >4 points, ongoing corticosteroid therapy, or exit for treatment failure. Results Serum fT3, fT4 and TSH concentrations were similar in infliximab (n=549) and adalimumab treated (n=448) patients. Baseline median [IQR] fT3/fT4 ratios were lower in women than men (0.30 [0.27 - 0.34] vs 0.32 [0.28 - 0.36], p<0.001), in patients with more severe inflammatory disease, and in patients receiving corticosteroids (0.28 [0.25 - 0.33] vs 0.32 [0.29 - 0.36], p<0.001). Multivariable logistic regression analysis demonstrated that fT3/fT4 ratio was independently associated with PNR at week 14 (OR 0.51, 95% CI 0.31 – 0.85, p = 0.009), however when stratified by drug and adjusted for variables known to be associated with PNR, low fT3/fT4 ratio remained associated with PNR for adalimumab, but not infliximab. After excluding patients treated with corticosteroids at baseline, there was no difference in fT3/fT4 ratio in those who experienced PNR compared to those who did not (PNR: [128/630] 0.31 [0.28 – 0.35] vs no PNR: [502/630] 0.32 [0.29 – 0.36], p = 0.095). The optimal threshold to determine PNR was 0.31 (AUC 0.57 [95% CI 0.54 - 0.61] sensitivity 0.62 [95% CI 0.41 - 0.74], specificity 0.53 [95% CI 0.42 - 0.73]). No association was seen for baseline fT3/fT4 ratio and non-remission or changes in faecal calprotectin concentrations at week 54. Conclusion Lower baseline serum fT3/fT4 ratio was independently associated with female sex, higher inflammatory burden at baseline, and baseline corticosteroid use, and predicted PNR to anti-TNF therapy at week 14, but not non-remission or change in faecal calprotectin concentrations at week 54. Overall, however, the diagnostic accuracy of baseline fT3/fT4 ratio to predict PNR to anti-TNF treatment was modest, limiting its clinical utility.

Abstract Background Patients with Inflammatory bowel disease (IBD) receiving anti-TNF or JAK-inhibitor therapy have attenuated responses to COVID-19 vaccination. We aimed to determine how IBD treatments affect neutralising antibody responses against the currently dominant Omicron BA.4/5 variants. Methods We prospectively recruited 329 adults (68 healthy controls (HC) and 261 IBD) who had received three doses of COVID-19 vaccine at nine UK centres. The IBD population was established (>12 weeks therapy) on either thiopurine (n=60), infliximab (IFX) (n=43), thiopurine & IFX combination (n=46), ustekinumab (n=43), vedolizumab (n=46) or tofacitinib (n=23). Pseudoneutralisation assays were performed and the half maximal inhibitory concentration (NT50) of participant sera was calculated. The primary outcome was anti-SARS-CoV-2 neutralising response against wild-type (WT) virus and the BA.4/5 variant after the second and third doses of anti-SARS-CoV-2 vaccine, stratified by immunosuppressive therapy, adjusting for prior infection, ethnicity, vaccine type and age. Results Heterologous (two doses adenovirus vaccine, third dose mRNA vaccine) and homologous (three doses mRNA vaccine) vaccination strategies significantly increased neutralising titres against both WT SARS-CoV-2 virus and the BA.4/5 variants in HCs and IBD (fig 1). Antibody titres against BA.4/5 were significantly lower than antibodies against WT virus in both groups (Geometric Mean Ratio (GMR) [95% CI], 0.11 [0.09, 0.15], P<0.0001 in healthy participants; GMR 0.07 [0.06, 0.08], P<0.0001 in IBD patients). Multivariable models showed that neutralising antibodies against BA.4/5 after three doses of vaccine were significantly lower in IBD patients on IFX (GMR 0.44 [0.20, 0.97], P=0.042), IFX and thiopurine combination (GMR 0.34 [0.15, 0.77], P=0.0098) or tofacitinib (GMR 0.37 [0.15, 0.92], P=0.032), but not in patients on thiopurine monotherapy, ustekinumab or vedolizumab. Breakthrough infection was associated with lower neutralising antibodies against WT and BA.4/5 (P<0.05). Conclusion A third dose of COVID-19 vaccine based on the WT spike glycoprotein boosts neutralising antibody titres in patients with IBD. However, responses are lower against the currently dominant variant BA.4/5, particularly in patients taking anti-TNF or JAK-inhibitor therapy. Breakthrough infections are associated with lower neutralising antibodies and immunosuppressed IBD patients may receive additional benefit from bivalent vaccine boosters which target Omicron variants. Financial support was provided as an Investigator Sponsored Research Grant from Pfizer Limited.

Vitamin D has a regulatory role in innate and adaptive immune processes. Previous small studies have reported that low pre-treatment vitamin D concentrations are associated with primary non-response and shorter drug persistence to anti-TNF therapy. We sought to assess whether pre-treatment 25-hydroxyvitamin D concentrations predicted primary non-response and non-remission to infliximab and adalimumab in patients with Crohn’s disease recruited to the PANTS (Personalised Anti-TNF Therapy in Crohn’s disease) study. We used composite endpoints using the Harvey Bradshaw Index (HBI) in adults and the short paediatric Crohn’s disease activity index (sPCDAI) in children, corticosteroid use, and C-reactive protein (CRP) to define primary non-response (Figure 1). Remission was defined as CRP of ≤3 mg/L and HBI of ≤4 points (short paediatric Crohn’s disease activity index ≤15 in children), without corticosteroid therapy or exit for treatment failure. 25-hydroxyvitamin D concentrations were measured in stored baseline serum samples and cut-offs for vitamin D status were: deficiency < 25nmol/L, insufficiency 25-50nmol/L and adequacy/sufficiency > 50nmol/L. Samples from 659/898 infliximab (526 Remicade; 133 biosimilar CT-P13) and 448/605 adalimumab (448 Humira) treated patients included in the effectiveness analysis of the PANTS study were included. Overall, 17.1% (189/1107; 95% confidence interval [CI] 15.0 - 19.4%) and 47.7% (528/1107; 95% CI 44.8 - 50.6%) patients had vitamin D deficiency and insufficiency, respectively. At baseline, 22.2% (246/1107) patients were receiving some form of vitamin D supplementation. Multivariable linear regression analysis confirmed that baseline sampling during non-summer months (Figure 2), South Asian ethnicity, lower serum albumin concentrations, higher HBI and nontreatment with vitamin D supplements were independently associated with lower vitamin D concentrations (Figure 3). Primary non-response at week 14 and non-remission at week 54 occurred in 19.3% (116/600; 95% CI 16.4 - 22.7%) and 58.8% (351/597; 95% CI 54.8- 62.7%) patients treated with infliximab and 25.3% (100/396; 95% CI 21.2- 29.8%) and 65.3% (246/377; 95% CI 60.3- 69.9%) of patients treated with adalimumab, respectively. Pre-treatment vitamin D status did not predict response or remission status to anti-TNF therapy at week 14 (infliximab Ppnr = 0.87, adalimumab Ppnr = 0.18) or non-remission at week 54 (infliximab P = 0.12, adalimumab P = 0.59) (Figure 4). Vitamin D deficiency is common in patients with active Crohn’s disease. Unlike previous studies, pre-treatment serum 25-hydroxyvitamin D concentration did not predict primary non-response to anti-TNF treatment at week 14 or non-remission at week 54.

Abstract Background Robust COVID-19 vaccine-induced antibody (Ab) responses are important for protective anti-viral immunity. Data are urgently needed to determine whether vaccine-induced immunity is impacted by commonly used immunosuppressive drug regimens in IBD. Methods We prospectively recruited 447 adults (90 healthy controls and 357 IBD) at nine UK centres. The IBD study population was established (>12 weeks therapy) on either thiopurine monotherapy (n=78), infliximab (IFX) monotherapy (n=61), thiopurine & IFX combination therapy (n=70), ustekinumab (uste) monotherapy (n=56), vedolizumab (vedo) monotherapy (n=62) or tofacitinib (tofa) monotherapy (n=30). Participants had two doses of either ChAdOx1 nCoV-19, BNT162b2 or mRNA1273 vaccines. The primary outcome was anti-SARS-CoV-2 spike (S1 RBD) Ab concentrations, measured using the Elecsys anti-SARS-CoV-2 spike (S) Ab assay, 53–92 days after second vaccine dose, in participants without prior infection, adjusted by age & vaccine type. Secondary outcomes included proportions failing to generate protective Ab responses (defined cut-off anti-S concentration 15U/mL, which correlated with 20% viral neutralization). Results Geometric mean S Ab concentrations (figure 1) were lower in patients treated with IFX (153U/mL;p<0.0001), IFX and thiopurine combination (109U/mL;p<0.0001), tofa (430U/mL;p<0.0001) and uste (561U/mL;p=0.013) compared to controls (1596U/ml). No differences in S Ab concentrations were found between controls and thiopurine monotherapy-treated patients (1020U/mL;p=0.62), nor between controls and vedo-treated patients (944 U/mL;p=0.69). In multivariable modelling (figure 2), lower S Ab concentrations were independently associated with IFX (FC 0.10 [95% CI 0.07–0.14], p<0.0001), tofa (0.36 [95% CI 0.19–0.69],p=0.002) and uste (0.56 [95% CI 0.31–1.00],p=0.049), but not with thiopurine (0.77 [95% CI 0.54–1.11],p=0.17) or vedo (1.01 [95% CI 0.61–1.68],p=0.96). mRNA vaccines (3.67 [95% CI 2.72–4.96],p<0.0001) and older age (0.82 [95% CI 0.73–0.91],p=0.0003) were independently associated with higher & lower S Ab concentrations respectively. Protective Ab responses were generated by all thiopurine monotherapy, vedo, tofa and healthy control participants, but not by 11% of patients on IFX monotherapy, 13% on thiopurine & IFX combination therapy and 4% on uste. Conclusion COVID-19 vaccine-induced Ab responses are significantly reduced in patients treated with IFX, or tofa, and to a lesser extent with uste. No significant reduction was seen in vedo or thiopurine monotherapy-treated patients. Our data suggest that 3rd primary or booster vaccine doses for IBD patients might be tailored to an individual’s immunosuppressive treatment. Financial support was provided as a Research Grant by Pfizer Ltd.

Abstract Background Anti-TNF treatment failure is common. Primary non-response and loss of response are frequently caused by low anti-TNF drug levels mediated, principally, by the formation of anti-drug antibodies which can be mitigated by concomitant immunomodulator use. Previous small studies in patients with IBD suggest that antibodies formed prior to treatment can bind drug and impair the pharmacokinetics, efficacy and safety of the anti-TNF drugs. We sought to determine the prevalence, neutralising capacity and clinical relevance of pre-treatment antibodies to infliximab and adalimumab in in anti-TNF-naïve patients with active luminal Crohn’s disease. Methods The Personalised Anti-TNF Therapy in Crohn’s Disease study (PANTS) is a UK-wide, multicentre, prospective observational cohort reporting treatment failure rates of the anti-TNF drugs infliximab and adalimumab in Crohn’s disease. The prevalence of antibodies to infliximab and adalimumab at baseline in all patients were measured using IDKmonitor ELISA assays and neutralising capacity in positive cases was determined using the iLite™ cell-based assays. Associations between baseline antibody status, subsequent immunogenicity and drug levels, and response status were assessed using Mann-Whitney U tests and chi-squared analyses, respectively. Results In the PANTS cohort, at baseline, pre-treatment anti-TNF antibodies were detected in 7.3% (112/1525) patients. Pre-treatment antibodies to infliximab were more common (6.3% 96/1525 vs 2.4% 36/1525, p<0.01) and of higher levels (median (IQR) infliximab: 23.9 (14.2 – 55.2) AU/ml vs adalimumab: 7.2 (6.3 – 10.4) AU/ml, p<0.0001) than adalimumab. A minority (1.3% (20/1525)) of patients had anti-drug antibody reactivity to both drugs. None of the detected anti-drug antibodies had demonstrable anti-TNF neutralising capacity detected by our iLite™ cell-based assay. No associations were seen between baseline antibody reactivity, subsequent immunogenicity, drug levels or response status at week 14 or week 52. Conclusion Pre-treatment anti-drug antibodies are common. However, they do not neutralise anti-TNF drug activity invitro, promote drug clearance or influence clinical response to anti-TNF drugs. Further work is required to understand this cross-reactivity and to determine the exact nature of the antibodies detected in drug naïve individuals.

Abstract Background Antibody responses following SARS-CoV-2 infection or a single-dose of SARS-CoV-2 vaccine are impaired in patients with inflammatory bowel disease treated with anti-TNF compared to those treated with vedolizumab, a gut-selective anti-integrin α4β7 monoclonal antibody. Here we sought to determine if patients treated with infliximab have attenuated serological and T cell responses and an increased risk of breakthrough COVID-19 infection following primary SARS-CoV-2 vaccination. Methods Anti-spike (S) receptor binding domain (RBD) antibody concentration in 2306 infliximab-treated patients were compared to a cohort of 1045 vedolizumab-treated patients. Our primary outcome was anti-S RBD antibodies 2 to 10 weeks after a second dose of the BNT162b2 or ChAdOx1 nCoV-19 vaccines. Secondary outcomes were anti-spike T cell responses, durability of vaccine responses and risk of breakthrough infections following two doses of vaccine. Results Anti-S RBD antibody concentrations were lower in patients treated with infliximab than in those treated with vedolizumab, following a second dose of BNT162b2 (567.3 U/mL [6.1] vs 4601.1 U/mL [5.3], p <0.0001) and ChAdOx1 nCoV-19 (183.9 U/mL [5.0] vs 789.4 U/mL [3.5], p <0.0001) vaccines (Fig. 1). Vaccination with the BNT162b2 vaccine compared to the ChAdOx1 nCoV-19 was independently associated with a 3.7-fold [95% CI 3.30 – 4.13] higher anti-S RBD antibody concentration (p < 0.0001) (Fig. 2). There were no significant differences in the magnitude of anti-spike T cell responses observed in infliximab- compared with vedolizumab-treated patients after one or two doses of either vaccine. Antibody half-life was shorter in infliximab- than vedolizumab-treated patients following two-doses of BNT162b2 (4.0 weeks [95% CI 3.8 – 4.1] vs 7.2 weeks [95% CI 6.8 – 7.6]) and ChAdOx1 nCoV-19 (5.3 weeks [95% CI 5.1 – 5.5] vs 9.3 weeks [95% CI 8.5 – 10.2], p value < 0.0001). Breakthrough SARS-CoV-2 infections were more frequent (5.8% (202/3467) vs 3.9% (66/1691), p = 0.0032) and the time to breakthrough shorter in patients treated with infliximab than vedolizumab (p = 0.0023) (Fig. 3). Higher anti-S RBD antibody concentrations following a second dose of SARS-CoV-2 vaccine protected against breakthrough SARS-CoV-2 infection: overall, for every 10-fold rise in anti-S RBD antibody level we observed a 0.8-fold reduction in odds of breakthrough infection ([95% CI 0.70 – 0.99], p = 0.035). Conclusion Infliximab was associated with attenuated, less durable vaccine induced anti-S RBD antibody responses and a 50% increase in breakthrough SARS-CoV-2 infection. Further follow-up is required to assess whether third primary doses can mitigate the effects of infliximab on anti-S RBD antibody responses.

Anti-TNF (aTNF) treatment failure in patients with IBD is common. International guidelines recommend switching out of class when aTNF drug levels are therapeutic and within class with an immunomodulator when aTNF drug levels are suboptimal and associated with antibody development. We sought to define the: 1) risk of immunogenicity to a second aTNF stratified by immunogenicity to the first aTNF and 2) rates of drug persistence to a second aTNF in patients with pharmacodynamic or immunogenic failure of their first aTNF drug. We performed a retrospective cohort study across 32 UK hospitals. 870 patients (444 male, 630 (72%) Crohn’s disease) who had both infliximab and adalimumab therapeutic drug monitoring performed by our service from May 2013 to November 2020 were identified. Drug and antibody levels were measured using the IDKmonitor® drug tolerant ELISA assays. Treatment failure included primary nonresponse, secondary loss of response, adverse drug reactions and IBD-related surgeries, and was identified by case note review. Immunogenic failure was defined as treatment failure with suboptimal drug levels (infliximab level <2 mg/L, adalimumab level <6 mg/L) with an antibody concentration ≥10 AU/ml. Pharmacodynamic failure was defined as treatment failure despite adequate drug levels. Patients who developed immunogenicity to adalimumab (first) were more likely to develop immunogenicity to infliximab (second) (63% vs 40%, p = 0.004), and patients who developed immunogenicity to infliximab (first) were more likely to develop immunogenicity to adalimumab (second) (33% vs 19%, p = 0.002) (Fig 1). Patients who developed: antibodies and undetectable drug, low drug levels, or low drug levels with immunogenicity to infliximab (first), were more likely to develop these outcomes to adalimumab (second) (all p<0.001). There was no difference in drug persistence to second aTNF in patients with pharmacodynamic and immunogenic treatment failure (Fig 2). In patients with immunogenic (but not pharmacodynamic) failure, commencing an immunomodulator at the time of switching to second aTNF drug was associated with longer drug persistence than in patients treated with an immunomodulator throughout or not all (Fig 3). Immunogenicity to the first aTNF was associated with immunogenicity to the second aTNF, irrespective of drug sequence. Commencing an immunomodulator at the time of switching to second aTNF was associated with improved drug persistence in immunogenic, but not pharmacodynamic, failure. However, 50% of patients remained on second aTNF at 5 years in both groups, suggesting switching in-class may be appropriate irrespective of the cause of treatment failure to first aTNF.

Abstract Background Anti-TNF (aTNF) treatment failure in patients with IBD is common. International guidelines recommend switching out of class when aTNF drug levels are therapeutic and within class with an immunomodulator when aTNF drug levels are suboptimal and associated with antibody development. We sought to define the: 1) risk of immunogenicity to a second aTNF stratified by immunogenicity to the first aTNF and 2) rates of drug persistence to a second aTNF in patients with pharmacodynamic or immunogenic failure of their first aTNF drug. Methods We performed a retrospective cohort study across 32 UK hospitals. 870 patients (444 male, 630 (72%) Crohn’s disease) who had both infliximab and adalimumab therapeutic drug monitoring performed by our service from May 2013 to November 2020 were identified. Drug and antibody levels were measured using the IDKmonitor® drug tolerant ELISA assays. Treatment failure included primary nonresponse, secondary loss of response, adverse drug reactions and IBD-related surgeries, and was identified by case note review. Immunogenic failure was defined as treatment failure with suboptimal drug levels (infliximab level <2 mg/L, adalimumab level <6 mg/L) with an antibody concentration ≥10 AU/ml. Pharmacodynamic failure was defined as treatment failure despite adequate drug levels. Results Patients who developed immunogenicity to adalimumab (first) were more likely to develop immunogenicity to infliximab (second) (63% vs 40%, p = 0.004), and patients who developed immunogenicity to infliximab (first) were more likely to develop immunogenicity to adalimumab (second) (33% vs 19%, p = 0.002) (Fig 1). Patients who developed: antibodies and undetectable drug, low drug levels, or low drug levels with immunogenicity to infliximab (first), were more likely to develop these outcomes to adalimumab (second) (all p<0.001). There was no difference in drug persistence to second aTNF in patients with pharmacodynamic and immunogenic treatment failure (Fig 2). In patients with immunogenic (but not pharmacodynamic) failure, commencing an immunomodulator at the time of switching to second aTNF drug was associated with longer drug persistence than in patients treated with an immunomodulator throughout or not all (Fig 3). Conclusion Immunogenicity to the first aTNF was associated with immunogenicity to the second aTNF, irrespective of drug sequence. Commencing an immunomodulator at the time of switching to second aTNF was associated with improved drug persistence in immunogenic, but not pharmacodynamic, failure. However, 50% of patients remained on second aTNF at 5 years in both groups, suggesting switching in-class may be appropriate irrespective of the cause of treatment failure to first aTNF.