Prometheus Laboratories Research Articles

(089) CORRELATIONS BETWEEN IMMUNOHISTOCHEMICAL STAINING AND PAIN-RELATED ASSESSMENTS IN PATIENTS WITH NEUROPROLIFERATIVE VESTIBULODYNIA

Abstract Introduction Mast cell accumulation and nerve proliferation has been hypothesized to lead to pain symptoms for patients with neuroproliferative vestibulodynia (NPV). A clinically suspected diagnosis of NPV can be confirmed by examining immunohistochemical (IHC) staining of excised vestibular specimens. Compared to controls, specimens from NPV patients have been found to contain >8 mast cells per high-power field (HPF) and increased density of nerves. Objective To assess for correlations between patient reported pain-related measures and computer-assisted histometry of excised vestibulectomy specimen IHC staining with CD117 (marker for mast cells) and PGP9.5 (marker for nerves) in a cohort of histopathologically confirmed NPV patients. Methods Patients (n=65) with lifelong or acquired NPV undergoing vestibulectomy had IHC-staining of excised vestibular tissue. Tissue sections from the 1:00-11:00 and/or 12:00 regions of the vestibule were examined and high-resolution images were captured using a microscope at 100x and 200x magnification. A minimum of 2 photomicrographs per magnification were taken for each tissue section that included epithelial basement membrane and adjacent subepithelium representative of the majority of immunostained tissue. Fractional area of positive immunostaining of all photomicrographs was determined using computer-assisted histometry by ImageJ. Mean fractional area was determined from 3 separate measurements of each photomicrograph. Correlations were made between density of IHC staining and the following assessments: pain domain of the Female Sexual Function Index (FSFI), the Short Form McGill Pain Questionnaire (SF-MPQ), and cotton-tipped swab testing. We also examined correlations with the Patient Global Impression of Improvement (PGI-I), a treatment response index and indirect assessment of pain. Data were analyzed using Spearman correlations and the Mann-Whitney test. Results The study cohort had a median age of 26 (IQR = 23-31) years and experienced symptoms for a median duration of 11 (IQR = 6-15) years. While all patients reported high levels of pain (median FSFI pain domain score = 0.0), there were no correlations between CD117- or PGP9.5-immunopositive mean fractional area and FSFI pain domain or SF-MPQ scores. There was no difference in immunopositive mean fractional area between lifelong and acquired NPV. A positive correlation between fractional area of CD117 immunostaining in the 1:00-11:00 region of the vestibule and cotton-tipped swab test pain score approached but did not reach statistical significance (r = 0.24, p = 0.063). No correlations were observed between immunostaining and PGI-I or cotton-tipped swab testing scores. Likewise, SF-MPQ domain scores had no correlation to PGI-I or cotton-tipped swab testing. Median cotton-tipped swab testing pain scores were significantly higher (p < 0.001) in patients with lifelong NPV (7.6) compared to those with acquired NPV (5.7). Conclusions Our findings suggest that the high levels of pain experienced by NPV patients over a prolonged period of time may be dissociated from the density of mast cells and nerves in vestibular tissue. We postulate that any potential threshold of mast cell accumulation and increased nerve density that results in symptoms of vestibulodynia has been exceeded in our patient cohort. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Dare Bioscience; Pfizer; Prometheus Laboratories; Sprout Pharmaceuticals.

COMPARING REAL-WORLD OUTCOMES, MEASURED AS 12 AND 24-MONTH IBD-RELATED SURGERIES, BETWEEN INFLIXIMAB DOSE OPTIMIZED PATIENTS USING THERAPEUTIC DRUG MONITORING (TDM) VS AN UNOPTIMIZED CONTROL GROUP, IN A LARGE US COMMUNITY-BASED GASTROENTEROLOGY PRACTICES

Abstract BACKGROUND Anti-TNFs such as infliximab (IFX) continue to be the standard of care to treat moderate-to-severe IBD. Remission and reducing detrimental outcomes are achievable goals when therapeutic drug monitoring (TDM) is implemented to assist with IFX therapy optimization. TDM aids in achieving & maintaining adequate drug exposure to avoid loss of response by offering actionable information to guide treatment adjustments. The value of TDM has been described in numerous studies which show that optimization of anti-TNFs correlates with improved clinical outcomes & the use of TDM is recommended by IBD guidelines and expert consensus. A potential evidence gap is the lack of real-world outcomes data when Anser®, a TDM test, is implemented in a community setting. OBJECTIVE Describe & compare the real-world outcomes, measured as IBD-related surgeries, in IFX dose optimized patients using Anser® TDM as part of ongoing IBD care as compared to a no TDM control group in a community-based practice setting. METHODS De-identified patient charts from a US-based community gastroenterology practice were analyzed for all patients (ages 8 to 89) treated with IFX from 2016 to 2022. Matching records to Prometheus Laboratories test results were then tokenized. Two cohorts were structured, Anser TDM as part of ongoing IBD care & no TDM. Groups were matched by propensity score, baseline disease, demographics, and comorbidities for comparison. Real-world outcomes were accessible via Lynx.MD online database. Analysis was conducted, stratifying patients as all IFX patients or anti-TNF naïve patients (TNF-N), to compare the percentage of IBD-related surgeries for 12 or 24-month outcomes. IBD surgeries were recorded in patient charts as colectomies, surgeries for fistula, bowel perforations, drainage of abscesses, adhesiolysis and other surgical bowel procedures. Statistical analysis was completed by Lynx.MD. RESULTS The size of Anser TDM (n= 235 to 337) and no TDM (n= 223 to 321) cohorts varied depending on the analysis criteria. Crohn’s disease was majority (2/3) and median age ranged from 36 to 39. For all IFX patients the 12-month outcomes of any IBD surgery was 1.2% for Anser TDM vs 6.5% for no TDM (5.4%, P=0.001). For TNF-N patients, the rate was 1% and 6.8%, respectively (5.7%, P=0.001). The results for 24-month outcomes for all IFX patients were 4.1% for Anser TDM vs 9.8% for no TDM (4.1%, p=0.016), and 4.3% vs 9% respectively for TNF-N (4.8%, P=0.06). CONCLUSIONS Real-world outcomes data for 12 and 24-months demonstrate that the Anser IFX TDM group had significantly lower rates of IBD surgeries for all patients, including for 12-month outcomes in TNF-N. This finding provides the first analysis, on Anser® TDM used to optimize patient’s IFX dosing, in comparison to a matched cohort of no TDM patients within the same community gastroenterology clinic setting.

B-341 Analytical Performances of Homogeneous Mobility Shift Assay for Infliximab and Biosimilars and Resulting Exposure Assessments in Large Cohort of Patients With Inflammatory Bowel Diseases

Abstract Background Biosimilar for infliximab (IFX) are currently available for the treatment of various immune mediated inflammatory diseases including inflammatory bowel disease (IBD). We have validated the homogenous mobility shift assay (HMSA) for IFX biosimilars and describe exposure from a large population of patients with IBD treated with IFX and biosimilars. Methods Validation of the biosimilars, infliximab-dyyb (Inflectra®) and infliximab-abda (Renflexis®), was conducted in a reference clinical laboratory (Prometheus Laboratories, Inc.) for performance equivalence to the 1st international World Health Organization (WHO) IFX standard (16/170) by HMSA. The evaluated performance characteristics consisted of accuracy, precision, sensitivity, specificity, range, and linearity using spiked human serum. Following validation and implementation in the clinical laboratory, the drug median with interquartile range (IQR) and antibody to drug (ATI) prevalence and percentage relative to low-titer antibody cut-point of 10 U/mL (Am J Gastroenterol 2021;00:1-12), using de-identified patients, was evaluated by comparing treatment with IFX or the two validated biosimilars. Results The reportable range for the biosimilars was 0.98 μg/mL (precision: 5.5% CV; accuracy: 110.7% recovery) to 34 µg/mL (precision: 6.3% CV; accuracy: 105.4% recovery). Biosimilar intra-day, inter-day precision (CV) and accuracy (% recovery) across the reportable range were 3.8%, 3.6% and 105.1%, respectively. Furthermore, HMSA calibrated with IFX originator or biosimilar showed congruent results when compared to calibration with the WHO standard for the determination of drug concentrations using 20 clinical samples spanning the reportable range (Fig. 1). Median drug concentrations with IQR were 10.9 µg/mL (4.8–19.7 µg/mL) for infliximab originator, 9.8 µg/mL (3.9–18.1) for infliximab-dyyb, and 9.5 µg/mL (3.6–18.3) for infliximab-abda over a three-year period of testing, which also demonstrated similar ATI positivity rates. Conclusion HMSA is validated to be used as a tool for therapeutic drug monitoring (TDM) of patients treated with IFX originator and biosimilars.

B-340 Performance of a Quality System for Targeted Monoclonal Antibodies in a Reference Clinical Pharmacokinetic Laboratory

Abstract Background The homogenous mobility shift assay (HMSA) laboratory developed test (LDT) quantifies monoclonal antibody drug and anti-drug antibody levels and is useful for the management of inflammatory bowel diseases (IBD). We report the implementation and performance of a quality system for these LDTs, as well as longitudinal trends of exposure and immunization prevalence from a reference clinical pharmacokinetic (PK) laboratory (Prometheus Laboratories, Inc.). Methods Quality control (QC) HMSA data was evaluated to verify conformance to specifications for infliximab (IFX), adalimumab (ADA), vedolizumab (VDZ), ustekinumab (UST) and their respective anti-drug antibodies (antibody to IFX [ATI], ADA [ATA], VDZ [ATV], and UST [ATU]). A QC panel consisting of five serum specimens spanning the reportable range per each drug or anti-drug antibody LDT was established, stored at subzero temperature, and tested monthly over a period of two years. Acceptable performance consisted of 80%–120% accuracy from the target value. All specimens were blinded to operator and processed with the clinical PK load of testing. Exposure and immunization prevalence over three years of testing was evaluated. All patient data were de-identified before analysis. Median drug level (interquartile ranges [IQR]), and anti-drug percent positivity by international classification of disease was also estimated (ICD-10 based). Results The QC results establish that the drug (IFX, ADA, VDZ, UST) and anti-drug (ATI, ATA, ATV, ATU) LDTs report acceptable performance with 80%–120% accuracy over the two-year evaluation period. Median drug concentrations with IQR were assessed for the clinical sample set differentiated by disease classification as depicted in Fig. 1. Anti-drug positivity levels were higher for ATI (mean: 11.5%) and ATA (mean: 13.6%) than those from ATV (mean 2.0%) and ATU (mean: 0.6%). Conclusion The QC data presented supports the performance of HMSA for therapeutic drug monitoring (TDM) of IBD and other immune mediated inflammatory diseases.

Economic burden related to fistulas or strictures among commercially insured patients with Crohn's disease in the United States.

BACKGROUND: Crohn's disease (CD) is a chronic, progressive, immune-mediated gastrointestinal condition that can lead to fistulizing or stricturing complications. OBJECTIVE: To quantify the burden of illness related to fistulas and/or strictures in patients with CD. METHODS: Using the Optum Research Database from October 2015 to December 2019, patients with CD were classified according to 1 of 3 condition cohorts: CD with fistula (CD-F), CD with stricture (CD-S), or CD with fistula and stricture (CD-FS). Each cohort was matched to a nonfistula, nonstricture CD cohort. Postdiagnosis per patient per year (PPPY) costs and health care resource utilization were assessed, accounting for variable lengths of follow-up periods. Multivariable generalized linear models were used to estimate the adjusted mean costs in each cohort. RESULTS: The CD-F, CD-S, and CD-FS cohorts included 1,317; 4,650; and 894 patients, respectively. The mean age of patients within the CD-S and their comparator cohorts was higher than in the CD-F or CD-FS cohorts (59.9 vs 49.5 vs 49.6 years). At baseline, cardiovascular disease was the most common comorbidity across all condition and comparator cohorts. Condition cohorts had 2-4 times more inpatient visits, 5-8 times more surgical visits, and 2-3 times more endoscopies PPPY than comparator cohorts. Compared with their respective comparator cohort, patients in the 3 condition cohorts had higher medication, medical, and total health care costs. CONCLUSIONS: This study demonstrates a significant economic burden related to fistulas and/or strictures among patients with CD, highlighting the importance of prevention, early recognition, and appropriate management of CD-related complications. DISCLOSURES: Yanni Fan, Ling Zhang, Jennifer S Thompson, and Kimberly G Brodovicz are employees of Boehringer Ingelheim. Rhonda L Bohn, Monik C Jiménez, and Stephani Gray (Bohn Epidemiology, LLC) are paid consultants to Boehringer Ingelheim. Gil Y Melmed reports receiving grants from Pfizer; consulting fees from Boehringer Ingelheim, AbbVie, Arena, BMS, Celgene, Entasis, Ferring Lilly, Fresenius Kabi, Medtronic, Samsung Bioepis, Janssen, Takeda, Pfizer, Prometheus Labs, and TechLab. We conducted a retrospective study using administrative claims data from the Optum Research Database, a database of a commercially insured population in the United States. All patient data were anonymized and deidentified; therefore, informed consent was not necessary. Restrictions apply to the availability of these data because of a contract between Optum and Boehringer Ingelheim, and data are thus unavailable to the public. For enquiries on the dataset analyzed in this study, please contact Optum (https://www.optum.com).

P381 Ustekinumab trough levels are associated with sonographic transmural healing in Pediatric Inflammatory Bowel Disease

Abstract Background Transmural healing (TH) assessed by intestinal ultrasound (IUS) is associated with improved inflammatory bowel disease (IBD) outcomes. This study evaluates the relationship between ustekinumab trough levels (UTL) and sonographic TH in children with IBD treated with ustekinumab (UST). Methods Children (<18 years) with IBD treated with maintenance UST and undergoing IUS examination and serum UTL (Prometheus Labs, CA) at a single tertiary center between July 2020 and October 2022 were prospectively recruited. Children who underwent IUS and UTL on 2 events >6 months apart were included in a per-event analysis. Primary outcome was the comparison of UTL between children with and without TH, defined as bowel wall thickness (BWT) ≤3 mm and no hyperemia (BWH) on color Doppler, using the Mann-Whitney U test. Area under the receiver operating curve (AUROC) determined the optimal UTL cut-point to detect TH. Secondary outcome was the comparison of UTL for each IUS parameter. Descriptive statistics summarized the data as frequencies and percentages for categorical variables and median [interquartile range] for continuous variables. A p-value of significance was set to <0.05. Results Overall, 50 IUS exams on 129 bowel segments were performed in 44 children with IBD, 34:10 Crohn’s disease (CD):ulcerative colitis (UC)/IBD-U treated with UST, median [IQR] age 14.9[13.2-16.6] years, 22(50%) female, and disease duration 3.83[1.98-5.32] years (Table 1). 18(41%) children were treated with standard dose UST of 90mg every 8 weeks and had significantly lower UTL compared to 26(59%) treated with escalated dosing of 90 mg every 4 or 6 weeks (7.4[4.8-12.7] ug/ml vs. 11.6[6.1-19.3] ug/ml, p=0.002). Median time between UTL and IUS was 0 days [0-11.25]. Overall, 24(55%) children (18(53%) CD, 6(60%) UC/IBD-U) achieved TH. Higher UTL was associated with TH (13.1[6.1-17.5] ug/ml) compared to children without TH (5.7[4.2-13.9] ug/ml; p=0.010) (Figure 1A). Higher UTL was also associated with TH in children with CD (11.7[5.3-17.0] ug/ml) compared to children with CD without TH (5.5[4.2-11.0] ug/ml; p=0.013) (Figure 1B). Optimal UTL cut-point to detect TH was 11.4 ug/ml for all children (AUROC=0.647, sensitivity=62%, and specificity=69%) and children with CD (AUROC=0.661, sensitivity=59%, specificity=79%). Median UTL for all children was associated with lymphadenopathy (p=0.02) but no other individual IUS parameters (Table 2). Conclusion Higher maintenance UTL are associated with sonographic TH in children with IBD. Future prospective studies are needed to determine if targeting higher UTL levels during induction and maintenance UST therapy promotes TH.

S824 Cost-Effectiveness of Precision-Guided Dosing in Adult Crohn’s Disease Patients Initiating Infliximab Maintenance Therapy

Introduction: Crohn’s disease (CD) patients that lose response to biologics experience reduced quality of life (QoL) and costly hospitalizations. Precision-guided dosing provides clinicians with a comprehensive pharmacokinetic (PK) profile that allows for the next biologic dose to be personalized. We analyzed the cost-effectiveness of infliximab (IFX) Precision-guided dosing relative to two IFX dose intensification strategies (DIS). Methods: We developed a hybrid (Markov and decision tree) model of CD patients who had a clinical response to IFX induction and entered IFX maintenance in “remission” or “mild symptoms” health states. The analysis took a US payer perspective, a time horizon of 2 years in the base case, and a cycle length of 4 weeks. There were 3 comparators for IFX dosing: Precision-guided dosing, dose intensification based on symptoms, inflammatory markers, and trough IFX concentration (DIS1), and IFX dose intensification based on symptoms alone (DIS2). Patients that failed IFX initiated ustekinumab (UST), followed by vedolizumab, and conventional therapy. Transition probabilities for IFX were estimated from real-world clinical PK data and interventional clinical trial (PMID: 34978325; 29317275) patient-level data. All other transition probabilities were derived from published randomized clinical trials and cost-effectiveness analyses. Utility values were sourced from previous health technology assessments. Direct costs included biologic acquisition and infusion, surgeries and procedures, conventional therapy, and lab testing. The primary outcomes were total discounted costs, total quality-adjusted life years (QALYs), and incremental cost-effectiveness ratios (ICERs). The robustness of results was assessed via one-way sensitivity and scenario analyses. Results: Total costs and QALYs at 2 years are presented in Table. The ICERs of Precision-guided dosing relative to DIS1 and DIS2 were 171,810 and 127,990, respectively. One-way sensitivity analyses (Figure) demonstrated that the cost-effectiveness of Precision-guided dosing was most sensitive to the time between IFX doses. Precision-guided dosing had the lowest proportion of patients requiring a new biologic through 2 years (0.5% vs 2.4% and 27.7% for DIS1 and DIS2, respectively). Conclusion: Precision-guided dosing provides substantial clinical and QoL benefits for adult CD patients by maintaining clinical remission and avoiding IFX failure; it is cost-effective relative to other DISs at a WTP of $175,000/QALY.Figure 1.: Precision-guided Dosing ICER Relative to DIS2 † Varied by ±10% * Varied by ±5% CD: Crohn's disease, DIS: dose intensification strategy, ICER: incremental cost-effectiveness ratio, IFX: infliximab, M-S: moderate-severe, PMPM: per member per month, Rem: remission Table 1. - Base Case Results (2-year Horizon Discounted) DIS Total QALYs Total Costs ICER Relative to Precision-guided Dosing ICER Relative to DIS1 ICER Relative to DIS2 Incremental NMB vs DIS1 (WTP $150,000/QALY) Incremental NMB vs DIS1 (WTP $50,000/QALY) Incremental NMB vs DIS2 (WTP $150,000/QALY) Incremental NMB vs DIS2 (WTP $50,000/QALY) Precision-guided Dosing* 1.572 $50,753 - 171,810 127,990 -$765 -$4,274 $1,816 -$6,436 DIS1† 1.537 $44,725 171,810 - 95,581 - - $2,581 -$2,162 DIS2 ‡ 1.489 $40,191 127,990 95,581 - -$2,581 $2,162 - - DIS: dose intensification strategy, ICER: incremental cost-effectiveness ratio, NMB: net monetary benefit, QALY: quality-adjusted life year, WTP: willingness to pay.*Model informed precision dosing with homogenous mobility shift assay (Prometheus Laboratories).†Dose intensification based on a combination of symptoms, inflammatory markers and proactive therapeutic drug monitoring. Corresponds to cohorts 1 and 2 of the TAILORIX clinical trial.‡Dose intensification reactive on symptoms only. Corresponds to cohort 3 of the TAILORIX clinical trial.

S814 Bile Acid Malabsorption Is a Common Risk Factor for Diarrhea in Adults With Mucosal Healing in Crohn’s Disease

Introduction: Bile acid malabsorption (BAM) accounts for over one-quarter of patients with diarrhea-predominant irritable bowel syndrome (IBS-D) and chronic diarrhea. However, the prevalence of BAM in adults with Crohn’s disease (CD) independent of ileal resection is not well characterized. We herein aim to identify the prevalence of BAM and determine its associations with diarrhea in adults with mucosal healing of CD on ileocolonoscopy. Methods: We analyzed a prospective cohort of adults with CD enrolled at a single institution biobank who underwent ileocolonoscopies from Jun 2014 to Mar 2021. Exclusion criteria were isolated upper GI CD (n=1) or prior bowel resection (n=9). Diarrhea was defined as an average of >3 liquid or very soft stools per day (SF>3) on the 2-item patient-reported outcome (PRO-2) measure over a 7-day period starting 48 hours before beginning bowel preparation. Endoscopic remission was defined as ≤2 on the Simple Endoscopic Score for Crohn's Disease (SES-CD). Histologic remission was defined as Geboes score < 2B.0 on biopsies from pre-determined ileocolonic segments (terminal ileum; ascending, descending, and rectosigmoid colon). Serum concentrations of 7α-hydroxy-4-cholesten-3-one (7C4), a precursor bile acid synthesis, were measured by liquid chromatography and mass spectrometry (Prometheus Laboratories) with BAM defined as a concentration ≥48.3 ng/mL (PMID: 30448597). We performed univariable analysis (χ2) and multivariable logistic regression to identify factors associated with diarrhea. Results: In 181 patients with CD in endoscopic remission, 29% (53/181) had diarrhea, and 29% (40/136) of those with 7C4 testing had BAM. Increased risk for diarrhea existed among those with BAM (OR 4.6, 95% CI 2.1-10.3, p< 0.01) and females (OR 2.2, 95% CI 1.1-4.3, p=0.02) (Table). On multivariate analysis, only BAM was a predictor of diarrhea (aOR 4.0, 95% CI 1.5-10.8, p< 0.01), but gender, ethnicity, and CD phenotype/location/duration were not predictors (Figure). Of the 57 patients with CD in endoscopic and histologic (endo-histologic) remission, BAM remains a risk factor for diarrhea (26%, 15/57; OR 35.8, 95% CI 6.9-184.2, p< 0.01). Conclusion: Bile acid malabsorption occurred in 29% and 26% of our cohort of adults with Crohn’s disease in endoscopic remission and endo-histologic remission, respectively, and conferred a 4-fold increased risk for diarrhea despite mucosal healing in Crohn’s disease.Figure 1.: Multivariable analysis of factor associated with diarrhea in adults with Crohn’s disease in endoscopic remission Key: aOR; adjusted odds ratio. CD, Crohn’s disease. Multivariable analysis of factor associated with diarrhea in adults with Crohn’s disease in endoscopic remission. Independent variables gender, ethnicity; CD phenotype, location, duration; and bile acid malabsorption. Dependent variable: diarrhea (SF >3) or diarrhea (stool frequency, SF >3). Table 1. - Crohn’s disease in Endoscopic remission (N=181) Characteristics n (%) Diarrhea (n=53) No Diarrhea (n=128) p-value OR (95% CI) p-value Gender 0.02 Female 36 (68%) 63 (49%) 2.2 (1.1-4.3) 0.02 Male 17 (32%) 65 (51%) Ref / Ethnicity 0.38 Caucasian Non-Caucasian 39 (74%) 101 (80%) 0.7 (0.3-1.5) 0.38 Missing n=1 14 (26%) 26 (20%) Ref / CD phenotype 0.08 Inflammatory Stricturing 18 (43%) 65 (63%) Ref / Fistulizing 12 (29%) 20 (19%) 2.2 (0.9-5.3) 0.0871 Missing n=36 12 (29%) 18 (17%) 2.4 (1.0-5.9) 0.0551 CD disease location Ileal Colonic Ileocolonic Missing n=22 0.14 22 (47%) 36 (32%) 1.5 (0.6-3.4) 0.38 14 (28%) 31 (28%) Ref / 12 (26%) 45 (40%) 0.6 (0.3-1.6) 0.33 CD duration 11 (21%)16 (31%)25 (48%) 31 (25%)51 (41%)43 (63%) 0.23 Ref0.9 (0.4-2.1)1.6 (0.7-3.8) /0.790.25 < 5 years 5-15 years >15 years Missing n=4 Bile acid malabsorption < 0.01 < 0.01 Yes No 22 (52%) 18 (19%) 4.6 (2.1-10.3) Missing n=45 20 (48%) 76 (81%) Ref Key: CD, Crohn’s disease; OR, odds ratio.

S725 linical Utility of Precision-Guided Dosing Tool for Infliximab During Maintenance Therapy of Inflammatory Bowel Disease

Introduction: A precision-guided dosing tool that uses Bayesian data assimilation was developed to forecast Infliximab (IFX) exposure. Our objective was to establish the utility of the tool in clinical decision making during IFX maintenance therapy when used reactively, to address inadequate disease control that results from suboptimal exposure, and proactively, to sustain exposure commensurate with disease remission in inflammatory bowel disease (IBD). Methods: Blood specimens were collected, anytime beyond 20 days after a prior infusion in a prospective study (EMPOWER). Pharmacokinetic (PK) testing was conducted at Prometheus Laboratories (San Diego, CA). Serum IFX, antibodies to IFX (ATI) and albumin concentrations were all imputed with dosing regimen and weight in a Bayesian data assimilation tool to produce individualized PK profiles that forecasted IFX concentration and time to trough concentration below pre-specified thresholds (e.g., < 10 µg/mL). Forecasted exposure at various dosing regimens was also provided. Physician’s global assessment of disease activity was collected with the decision to change IFX dosing that resulted from PK test results. Statistical analysis consisted of Mann-Whitney and Fisher Exact test as appropriate. Results: A total of 111 patients were assessed by 21 physicians. A change in IFX dose regimen was initiated in 51 patients (46%). Inadequate exposure and forecasted IFX levels below 10 µg/mL associated with dose intensification (76%, median IFX 6.3 µg/mL) (p< 0.01), with lower remission rate (23.5%) achieved in that group as compared to two other groups having better disease control and PK profiles (p< 0.001) (Table). Forecasted IFX levels below 10 µg/mL were associated with 4-fold higher likelihood of active disease (OR=4.1; 95%CI: 1.7-9.4) as compared to IFX levels above 10 µg/mL (p< 0.01). Time to trough below 10µg/mL was shorter in active disease (median: 46 days, IQR: 32-59) than in remission (median 57 days, IQR: 48-69) (p< 0.001). As presented in Figure, dose intensification using a 5 mg/kg every 4 weeks dosing regimen forecasted 2.3-fold higher IFX levels as compared to a 10 mg/kg every 8 weeks dosing regimen (median of 17.1 vs 7.4 µg/mL, respectively) (p< 0.001). Similar results were observed among patients presenting with disease remission. Conclusion: Our study suggests that the precision-guided dosing tool provides clinical utility and helps with dose adjustments in both interval changes as well as dose intensification.Figure 1.: Forecasted IFX Exposure at various dose and interdose intervals, given the individual PK parameters Table 1. - Patient Characteristics (n=111), by treatment intervention based on test results Variable IFX Dose RegimenReductionN=17 IFX Dose RegimenContinuationN=60 IFX Dose RegimenIntensificationN=34 OverallPopulationN=111 Patient Characteristics Age (years) 16 (14-19) 32 (18-45) 32 (17-46) 26 (16-44) Female (%, n/N) 44.1% (7/17) 43.3% (26/60) 44.1% (15/34) 43.2% (48/111) CD/UC/Indeterminate 13/3/1 36/15/8 22/9/3 71/27/12 Weight (Kg) 64 (43-76) 71 (61-92) 69 (61-92) 70 (60-84) Dose mg/Kg 10.0 (9.0-10.4) 8.2 (5.0-10.0) 5.5 (5.0-10.0) 8.0 (5.1-10.0) Interdose interval (weeks) 6 (5-8) 8 (6-8) 8 (6-8) 8 (6-8) PGA Remission Status, remission (%, n/N) 70.6% (12/17) 41.7% (25/60) 23.5% (8/34) 40.5% (45/111) Clinical PK Measurements Measured IFX levels (µg/mL) 23.3 (17.2-28.5) 12.9 (7.2-20.6) 8.0 (5.2-14.7) 12.5 (7.2-20.9) ATI status (%, n/N) 0% (0/17) 10.0% (6/60) 11.8% (4/34) 9.0% (10/111) Albumin (g/dL) 4.1 (4.0-4.3) 4.0 (3.6-4.2) 3.9 (3.7-4.2) 4.0 (3.7-4.2) Clearance (L/day) 0.19 (0.15-0.22) 0.27 (0.20-0.33) 0.28 (0.22-0.35) 0.25 (0.19-0.31) Time to Trough < 10 µg/mL (weeks) 11 (10-12) 7 (6-9) 6 (4-7) 7 (6-9) Forecasted Trough (µg/mL) 26.2 (20.1-34.5) 12.7 (8.6-17.6) 6.3 (3.1-9.4) 11.6 (6.5-19.5) Forecasted Trough < 10 µg/mL 0% (0/17) 31.7% (19/60) 76.5% (26/34) 40.5% (45/111)

209 Association of hidradenitis suppurativa with a Crohn’s disease panel

Hidradenitis suppurativa (HS) is a chronic, debilitating inflammatory skin disease. Crohn’s disease (CD) is among the most reported comorbid disorders in HS patients. Concurrent HS and CD are frequently associated with perianal disease that requires immunosuppressive therapy and surgery. We sought to identify unrecognized IBD associated with HS using a commercially available panel of serologic, genetic, and inflammatory markers with high specificity and sensitivity for CD (CD+) (IBD-sgi™ Panel, Prometheus Laboratories, San Diego).

1415-P: Risk–Benefit Data from the Worldwide EndoBarrier (EB) Registry

Uncertainty exists re risk:benefit of proximal intestinal exclusion with EB, a novel endoscopic duodenal jejunal liner device for obesity, both with and without diabetes. In view of this, during 2017, an independent, secure, on line registry was established under the auspices of the Association of British Clinical Diabetologists, for the collection of safety and efficacy data worldwide. As of December 2021, data had been entered on 10patients {age 52.1 ± 10.3 year, 53% male, 87% diabetes, BMI 41.1 ± 8.9 kg/m2} and showed many benefits (Table 1) . There were 43 (4.2%) SAEs and 139 (13.9%) less serious AEs (Table 2) . All SAE patients made a full recovery and most derived significant benefit. The benefits of EB therapy are likely to reduce the complications of diabetes. This international data from the EB registry suggests that the likely benefits of EB, far outweigh the risks Disclosure R.E.J. Ryder: None. J.P. Teare: None. A. Ruban: None. M. Haluzik: Advisory Panel; Boehringer Ingelheim International GmbH, Novo Nordisk A/S, Sanofi. Speaker's Bureau; Abbott Diabetes, AstraZeneca, Lilly Diabetes, Novartis AG. L. Munro: None. H. Frydenberg: None. J.J. McMaster: None. S. Fishman: None. R.V. Cohen: Advisory Panel; GI Dynamics. Research Support; Johnson &amp; Johnson, Medtronic. C.M. Aboud: None. G.J. Holtmann: Research Support; AbbVie Inc., Allergan, Arena Pharmaceuticals, Inc., Bayer, Bristol Myers, Datapharm Australia Pty Ltd Commonwealth Laboratories, Pty Limited, Eli Lilly Australia Pty Limited, F.Hoffmann-La Roche Limited, Falk Foundation, Falk GmbH and Co Kg, GI Therapies Pty Ltd, Gilead Sciences Pty Limited, MedImmune Ltd Celgene Pty Limited, Mylan, Nestle Pty Ltd, Prometheus Laboratories, Quintiles Pty Limited, Servatus, Takeda Development Center Asia, Pty Ltd, Vital Food Processors Ltd. C. de Jonge: None. J. Greve: Advisory Panel; GI Dynamics. Other Relationship; Bariatric Solutions International, Ethicon, Inc. J.C. Mason: None. H. Sourij: Advisory Panel; AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Daiichi Sankyo, Eli Lilly and Company, Merck Sharp &amp; Dohme Corp., Novo Nordisk. Research Support; Boehringer Ingelheim International GmbH, Sanofi. Speaker's Bureau; Amgen Inc., AstraZeneca, Boehringer Ingelheim International GmbH, Eli Lilly and Company, Merck Sharp &amp; Dohme Corp., Novartis AG, Novo Nordisk. R. Drummond: Research Support; Fractyl Health, Inc. Speaker's Bureau; AstraZeneca, Bristol-Myers Squibb Company. B. McGowan: Advisory Panel; Johnson &amp; Johnson, Lilly, Novo Nordisk. Research Support; Novo Nordisk. Speaker's Bureau; AstraZeneca, Novo Nordisk. Stock/Shareholder; Reset Health. S.A. Amiel: Advisory Panel; Medtronic, Novo Nordisk. Other Relationship; Sanofi. M. Yadagiri: None. P. Sen Gupta: None. K. Laubner: None. J. Seufert: Advisory Panel; Abbott, Sanofi-Aventis Deutschland GmbH. Research Support; Boehringer Ingelheim International GmbH. Speaker's Bureau; Abbott Diabetes, AstraZeneca, Bayer AG, Boehringer Ingelheim International GmbH, Lilly, Novo Nordisk, Sanofi-Aventis Deutschland GmbH. Funding Association of British Clinical Diabetologists

P117 point-of-care intestinal ultrasound for the detection of postoperative Crohn’s disease endoscopic recurrence

Abstract Background In patients with Crohn’s disease (CD), following an ileocolic resection (ICR), colonoscopy is the gold standard for the detection of endoscopic recurrence (ER). Colonoscopy, however, is invasive and not easily accepted by patients, particularly for repeated monitoring. In contrast, intestinal ultrasound (IUS) has the advantage of being non-irradiating, non-invasive, well-tolerated, and easy to repeat. The goal of this study was to assess the accuracy of IUS for ER in CD. Methods This was a cross-sectional study of CD patients who underwent IUS during a postoperative clinic visit within 30 days of a planned colonoscopy. Parameters on IUS included bowel wall thickness (BWT), bowel wall hyperemia (BWH; modified Limberg score 0-III), layer stratification, inflammatory fat, and complications. C-reactive protein (CRP), fecal calprotectin (FC), endoscopic healing index (EHI; Prometheus Labs, CA) and Harvey Bradshaw Index (HBI) were also measured. ER was defined as a Rutgeerts Score (RS) &amp;gt; i2. Primary outcome was the association between IUS parameters and ER. Secondary outcomes were the association of IUS parameters with other markers of disease activity. Results Eighteen CD patients (9 female; 29 [19–40] years old), underwent IUS examination 45 [29–99] months post-ICR during a routine clinic visit. Seven (39%) patients were on ustekinumab, four (22%) on adalimumab, two (11%) on infliximab, one (6%) on vedolizumab, and four (22%) on no therapy. ER was found in eight (44%) patients. BWT and BWH in the neo-terminal ileum and BWH at the ileocolic anastomosis were the only IUS parameters associated with ER (Table 1). Neo-terminal ileum BWT was 4.0 [3.2–4.8] mm in patients with ER compared to 2.0 [1.5–2.6] mm without (p=0.04). Neo-terminal ileum BWH was abnormal in six (75%) patients with ER compared to 0% without (p=0.007). BWT of 3.2 mm was the optimal cut point for predicting ER with an: AUROC of 0.82, positive predictive value of 100%, negative predictive value of 97.3%, sensitivity of 75%, and specificity of 100% (Figure 1) vs. a CRP of 10.4 mg/L (AUROC = 0.54) or FC of 1146 µg/g (AUROC = 0.56). Significant correlations were observed between neo-terminal ileum BWT and RS (ρ=0.51, p=0.04) and between BWT and CRP (ρ=-0.56, p=0.023). No correlation was observed between BWT and FC (ρ=-0.04, p=0.91), BWT and EHI (ρ=-0.04, p=0.91), or BWT and HBI (ρ=0.09, p=0.75). Conclusion IUS is a feasible, accurate, non-invasive monitoring tool for detection of postoperative CD recurrence. Larger prospective studies are needed to determine how IUS can be integrated in the monitoring of CD patients after surgery.

Longitudinal Vaccine-Induced Humoral Immune Response in Cancer Patients

Background: Longitudinal studies of mRNA vaccine-induced response demonstrate robust protection up to six months in healthy patients; however, evaluation of sustained response in cancer patients are lacking.Methods: In a prospective cohort study, 366 (291 vaccinated) patients [171 (145) solid tumors, 195 (146) hematologic malignancies] were enrolled and followed from November 2020 through September 2021. Antibody levels [anti-spike (IgG-(S-RBD)) and anti-nucleocapsid (IgG-N) immunoglobulin] were measured at three timepoints. Trajectories, peak, and persistence of antibody levels over time and frequency of breakthrough infections were evaluated by tumor type and timing of treatment relative to vaccination.Findings: At peak response (median=42 days after dose 1, interquartile range =26–57), 87.0% and 90.2% of patients were seropositive after two-dose BNT162b2 and mRNA-1273 vaccination (median IgG-(S-RBD)= 2,259 v. 9,804 AU/ml, p=0.002), respectively. Antibody response persisted longer in cancer patients receiving mRNA-1273 compared to BNT162b2 (p=0.003). Overall, patients with solid tumors attained higher peak (8,323 v. 1,128 AU/ml, p=0.001) and sustained antibody levels after 4–6 months (1,637 v. 353 AU/ml, pInterpretation: Our study shows variation in sustained antibody responses across cancer populations receiving various therapeutic modalities with important implications for vaccine booster timing and patient selection.Funding: NCI U54CA260591; NIH P01DK046763; NIH U01DK062413; K23HL153888; Cedars-Sinai Medical Center; Cedars-Sinai Precision Health Initiative; F. Widjaja Foundation Inflammatory Bowel and Immunobiology Research Institute; the Erika J. Glazer Family Foundation; and The Leona M. and Harry B. Helmsley Charitable Trust.Declaration of Interest: NM holds a consultant or advisory role at Amgen, Kite, Epizyme, TG Therapeutics, ADC Therapeutics, and has research funding from Miltenyi, Teva, and Amgen. JG holds a consultant or advisory role at EMD Serono; Elsevier; Exelixis; QED Therapeutics; Natera, Basilea, HalioDx, Eisai, Janssen. KR holds a consultant or advisory role at Amgen, AstraZeneca, Blueprint, Boehringer Ingelheim, Daiichi Sankyo, EMD Soreno, Genentech, GSK, Janssen, Lilly, Merck KGA, Mirati, Seattle Genetics, Takeda. JD holds a consultant or advisory role Kite Pharma and Morphosys. RB holds a consultant or advisory role at Genomic Health, Astra Zeneca, Biotheranostics, Pfizer; She is on the Speakers Bureau for Genentech, Seattle Genetics; she has research funding from Seattle Genetics, Ichnos Biosciences, Merck. JB has received research funding from Janssen. GYM has consulted for AbbVie, Arena Pharmaceuticals, Boehringer-Ingelheim, Bristol-Meyers Squibb/Celgene, Entasis, Janssen, Medtronic, Pfizer, Samsung Bioepis, Shionogi, Takeda, Techlab, and has received research funding from Pfizer for an unrelated investigator-initiated study. RV is on the Speaker’s Bureau for: Amgen, Bristol Myers Squib, Glaxo Smith Klein, Janssen, Karyopharm, and Takeda Pharmaceuticals. DM holds a consultant role for Prometheus Biosciences, Prometheus Laboratories, Pfizer, Takeda, Gilead, Palatin Technologies, and is a shareholder for Prometheus Biosciences. AM holds a consultant or advisory role at Novartis and Morphosys and has research funding from Amgen and Pfizer. All remaining authors have no COI to report.Ethical Approval: The study was approval by the institutional review board and all participants provided written informed consent.

Phase I Trial of Regulatory T-Cell Donor Lymphocyte Infusion Plus Daily Low-Dose Interleukin-2 for Steroid-Refractory Chronic Graft-Versus-Host Disease

Low-dose daily Interleukin-2 (IL-2) therapy expands regulatory T cells (Treg) in vivo in patients with chronic graft-versus-host disease (cGvHD). Clinical improvement, primarily partial response, is seen in 50-60% of those treated. We hypothesized that infusion of fresh Tregs prior to low dose IL-2 may augment clinical and immune responses. In a Phase 1 study, we administered fresh Treg-enriched lymphocyte infusions (Treg-DLI) obtained from the original stem cell donor, without in vitro stimulation or expansion, followed by daily low-dose IL-2 as therapy for cGvHD. Methods: 24 recipients of 7-8/8 HLA-matched allogeneic hematopoietic stem cell transplants with steroid-refractory cGvHD on stable immune suppression received escalating doses Treg-DLI: 5 each at 0.1, 0.3, or 1x106 cells/kg plus an expansion cohort of 9 at 1x106/kg. Non-mobilized leukapheresis products were CD8/CD19 co-depleted, then positively selected for CD25+ Tregs via the CliniMACS system (Miltenyi). IL-2 was administered at 1x106 U/m2/day for 8 weeks after Treg-DLI infusion. Subjects: The first 22 subjects had a median age of 48 (range, 23-68), median of 3 cGvHD sites (range, 1-6), and median of 2 prior therapies in addition to steroids (range, 0 -5). Four had prior IL-2 exposure. Median time from cGvHD diagnosis to enrollment was 26 months (range, 7- 84). Manufacturing: All Treg-DLI products met release criteria. Median CD8 and CD19 log-depletions were 4.5 and 4.6, respectively. Released products contained a median of 92.6% CD4+CD25++ cells and 88.2% CD4+CD25+CD27low Tregs, a 24.8-fold enrichment (range, 12.7-43.4). At the highest targeted dose level, a median of 0.98x106 cells/kg were infused (range, 0.64-1.0). Safety: In the 21 subjects evaluable for safety, there were no infusional AEs, no DLTs, and no cases of relapse. 2 subjects underwent a 50% dose reduction of IL-2 for Grade 2 flu-like symptoms and injection site irritation, at provider discretion. Grade 3 AEs possibly related to therapy were dyspnea and edema in 1 subject. At median follow-up of 26 months, 17 subjects are alive. 2-year survival is 82% (95% CI, 54-95%). Response: At 8 weeks, 2 of 5 subjects in Cohort 1 (1 partial response (PR), 1 stable disease with minor response (SDMR)), 4 of 5 subjects in Cohort 2 (2 PR, 2 SDMR), and 8 of 11 subjects at the highest cell dose (1 complete response(CR), 3 PR, 4 SDMR) demonstrated clinical benefit. Response rate (CR+PR) was 33%; clinical benefit rate (CR+PR+SDMR) was 67%. 11 subjects opted to continue IL-2, for a median of 14.5 months (range, 3-39). Of 4 subjects previously on IL-2 alone, 2 were responders (CR, PR) and 1 each had mixed response and SDMR, respectively. Interestingly, 3 subjects with SDMR at 8 weeks manifested PR on extended IL-2. No impact of Treg-DLI dose was observed. At 6 months, median prednisone dose was 15mg (range, 5-40), down from 30mg daily at baseline (range, 5-80). Correlative Immunology: Treg counts and the ratio of Treg to conventional T cells (Tcon) rose over time. Higher Treg:Tcon ratios at baseline (p=0.08) and at 2 weeks into therapy (p=0.03) were associated with clinical response (Figure 1). Breadth of diversity within Treg T-cell receptor β (TCRβ) sequences (Shannon's entropy) and selective expansions of individual Treg clones (clonality) were low in cGvHD subjects at baseline, as compared to normal donors (p<0.01) and to Treg-DLI products (p<0.001). Treg TCRβ entropy increased in cGvHD subjects after 8 weeks of therapy (p<0.05), and resulting entropy was comparable to normal donors (n=16, Figure 2). This normalization was independent of clinical response and persisted through 6 months (n=8). Treg TCRβ clonality trended upwards at 8 weeks but did not reach levels seen in normal donors. Entropy and clonality of CD8 and Tcon TCRβ populations in cGvHD subjects were comparable to normal donors and did not change with therapy. Conclusions: GMP-grade manufacture ofCD25+ enriched Treg-DLI is feasible. In combination with low-dose IL-2, Treg-DLI is safe and has clinical efficacy in steroid-refractory cGvHD, including in those with inadequate responses to IL-2 alone. TCRβ population diversity specifically in Tregs is normalized with therapy. The incremental benefit of adding Treg-DLI to therapy with IL-2 alone on clinical responses, normalization of immunologic diversity, and functional suppressive activity, including at timepoints beyond 8 weeks, is the subject of ongoing analyses. [Display omitted] DisclosuresNikiforow:Kite Therapeutics: Membership on an entity's Board of Directors or advisory committees. Armand:Affimed: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Infinity: Consultancy; Otsuka: Research Funding; Merck & Co., Inc.: Consultancy, Research Funding; Sequenta/Adaptive: Research Funding; Genmab: Consultancy; Roche: Research Funding; Tensha: Research Funding; Pfizer: Consultancy, Research Funding; Sigma Tau: Research Funding. Antin:Gentium SpA/Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Koreth:Millennium Pharmaceuticals: Research Funding; Prometheus Labs: Research Funding; Kadmon Corp: Membership on an entity's Board of Directors or advisory committees; Takeda Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Amgen Inc.: Consultancy.

Individual Patient Dose-Escalated Low-Dose Interleukin-2 for Steroid-Refractory Chronic Graft-Vs.-Host Disease in Children and Adults: Safety, Efficacy and Immune Correlates

CD4+CD25+FoxP3+ regulatory T cells (Treg) are broadly suppressive and play a central role in the prevention of chronic graft-versus-host disease (cGVHD) after allogeneic hematopoietic cell transplantation (HCT). Daily subcutaneous (SC) low-dose interleukin-2 (IL-2) at a fixed dose of 1x106 IU/m2/day in adult patients with refractory cGVHD induces selective Treg expansion and leads to clinical responses in 50-60% of evaluable participants (NEJM 2011, Blood 2016). During daily fixed-dose IL-2 therapy, plasma IL-2 levels rose rapidly by week 1, but subsequently decreased over time. The lower IL-2 levels were associated with a decline in Treg proliferation despite daily IL-2 administration (Sci Transl Med 2013), possibly due to IL-2 sequestration via binding to constitutively-expressed high affinity IL-2 receptors on Treg. We reasoned that IL-2 dose escalation at the time of anticipated fall in plasma IL-2 levels would avoid tachyphylaxis and maximize IL-2 induced Treg numbers in vivo.We conducted a phase 1 trial of individual patient IL-2 dose escalation over 8 weeks in adult and pediatric patients with steroid-refractory cGVHD. Daily SC IL-2 was initiated at 0.67x106 and 0.33x106 IU/m2/day in the adult and pediatric cohorts, respectively. Each participant had dose escalations at weeks 2 and 4 to a maximum dose of 2x106 IU/m2/day in adults and 1x106 IU/m2/day in children. We studied 18 HCT recipients (10 adult: 100% HLA-matched, 100% PBSC grafts, 40% prior aGVHD; 8 pediatric: 87.5% HLA-matched, 87.5% BM grafts, 28.6% prior aGVHD). Median age was 57 years (range, 33-71) in the adult cohort and 12 years (range, 5-22) in the pediatric cohort. The median time from HCT and from cGVHD onset to start of IL-2 treatment was 3 years (range, 1-12.1) and 597 days (range, 234-4336) respectively. Participants had a median of 2 cGVHD organ sites (range, 1-5) and 3 prior cGVHD therapies (range, 1-4) at enrollment. The cohorts did not differ in terms of time since cGVHD onset and number of failed therapies prior to enrollment.Individually dose-escalated IL-2 was well tolerated in children with 1 participant requiring dose reduction for electrolyte imbalances. In the adult cohort, 1 participant withdrew due to cGVHD progression, 1 required dose reduction for injection site reactions and 2 were unevaluable (1 IL-2 hold >1 month, 1 non-compliance). Seven grade 3 AEs were reported for six participants (electrolyte imbalance, vomiting, infection, increased ALT and soft tissue neoplasm); none relapsed. At week 8, objective cGVHD responses (PR) were seen in 7 of 8 pediatric participants (88%), but in only 1 of 8 evaluable adult participants (13%). cGVHD response sites included skin (n=4), joint/fascia/muscle (n=1), lung (n=4), and GI tract (n=2). Eight pediatric and 4 adult participants with clinical benefit (PR or SD with minor response) continued extended duration IL-2 therapy up to 120 weeks.Plasma IL-2 levels were higher in adults at weeks 1 and 2, but immune responses were similar between the 2 cohorts. Dose escalated IL-2 induced a >10-fold increase in median Treg count/µL that peaked at week 6. There were no significant changes in CD4 Tcon, CD8 T cell or B cell count. NK cell count increased >5-fold by week 8. The median Treg:Tcon ratio increased 6-fold from a baseline of 0.05 (Q1-Q3, 0.024-0.114) to a week 5 peak of 0.312 (Q1-Q3, 0.203-0.37). Compared with fixed daily dosing of IL-2 (Blood 2016), the individually dose escalated IL-2 schedule had a slower initial rise in Treg number and Treg:Tcon ratio (Figure 1). This likely reflects the lower starting doses in this study. The maximum IL-2 dose in the adults was twice the previously defined MTD but did not improve Treg expansion. Despite lower IL-2 doses, pediatric patients had a superior clinical response and a trend toward a better immunologic response compared with the adults.We demonstrate for the first time that low-dose IL-2 is safe in children with advanced steroid-refractory cGVHD and results in a high clinical response rate. A maximum dose of 1x106 IU/m2/day was well tolerated by pediatric patients in the extended duration phase and durably maintained Treg numbers above baseline. Five pediatric patients that continued IL-2 therapy for >20 weeks have reduced or discontinued steroid therapy. In adults, intrapatient dose escalation above fixed-dose MTD was not clinically tolerated and did not result in greater Treg expansion or clinical improvement relative to fixed daily dosing. [Display omitted] DisclosuresNikiforow:Kite Therapeutics: Membership on an entity's Board of Directors or advisory committees. Armand:Sequenta/Adaptive: Research Funding; Affimed: Research Funding; Roche: Research Funding; Merck & Co., Inc.: Consultancy, Research Funding; Infinity: Consultancy; Genmab: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Otsuka: Research Funding; Pfizer: Consultancy, Research Funding; Tensha: Research Funding; Sigma Tau: Research Funding. Antin:Gentium SpA/Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Koreth:Prometheus Labs: Research Funding; Amgen, Inc: Consultancy.

Phase II Trial of Natalizumab (Tysabri®) with Corticosteroids As Initial Treatment of Gastrointestinal Acute Graft Versus Host Disease

Background: Graft-vs.-host disease (GVHD) is caused by allorecognition of host antigens by tissue-specific donor lymphocytes. We have previously demonstrated that α4ß7 integrin is upregulated on both naïve and memory T cell subsets in patients who subsequently developed intestinal acute GVHD (Chen, BMT 2013). This integrin interacts with endothelial cell adhesion molecules and mediates homing of lymphocytes to the gastrointestinal (GI) tract. Natalizumab (Tysabri®, Biogen Inc.) is a selective adhesion molecule inhibitor, acting directly against the α4 subunit of α4 integrins. Given the poor outcomes of GI GVHD when treated with corticosteroids alone, we initiated a phase II study to determine the safety and efficacy of natalizumab in combination with corticosteroids for the initial treatment of acute GI GVHD.Methods: Subjects with new-onset, acute GVHD of the lower GI tract were eligible to participate. Other organ involvement was permitted but not required. Biopsy confirmation of GI GVHD and exclusion of infectious causes of diarrhea were required. Natalizumab was given at a dose of 300 mg IV, with a second dose permitted 4 weeks later in the event of an incomplete response. An initial corticosteroid dose of 2 mg/kg of methylprednisolone was suggested, but dosing and dose reductions were at the discretion of the treating physician. Steroids could be initiated up to 7 days prior to the initiation of natalizumab while biopsy and infectious disease specimens were being analyzed. The primary endpoint was GVHD-free survival rate 56 days from enrollment. Secondary endpoints included response rates at day 28 and 56, steroid dose at days 28, 56, 100, 180 and 365, incidence of systemic infections at day 56 and 180, and overall survival.Results: 18 subjects were enrolled and received at least one dose of natalizumab. Subjects had a median age of 63.5 years, and 12 were male. Fifteen had a non-myeloablative transplant, 12 had a matched unrelated donor, and all had received PBSCs. All subjects had newly diagnosed acute GI GVHD at time of enrollment; 4 had concomitant cutaneous and 1 had concomitant hepatic involvement. Stage 1, 2, 3, and 4 GI involvement was noted in 7, 4, 4, and 3 subjects respectively, corresponding to overall grade II GVHD in 7 and grade III in 11 subjects. Sixteen patients had data for response assessment. The day 56 GVHD-free survival rate was 37.5%. The overall response rate (PR+CR) for GI GVHD at day 28 and day 56 was 75% and 62.5% respectively. All surviving subjects except one achieved steroid dose reduction by day 56, with a median reduction of 61.6%. Three patients experienced treatment-related toxicity possibly related to natalizumab; one subject had grade 2 hepatic toxicity, one had grade 4 encephalopathy, and one developed hepatic failure. Three subjects have developed chronic GVHD. Four subjects had documented infections with bacteria (2), yeast (1), and viral pathogens (1- polyomavirus). Six subjects had measurable JC viremia prior to initiation of natalizumab and 8 subjects had measurable JC viremia at day 56, although only 1 subject had a viral load greater than 1000 copies/ml. No subject has developed JC-associated disease. Seven subjects have died. Causes of death include GVHD (2), disease relapse (2), and organ failure (3). With a median follow-up of 180 days, the 6 month overall survival was 52% (95% CI 25-74%).Conclusion: Natalizumab in combination with corticosteroids as initial treatment of acute gastrointestinal GVHD is feasible and well tolerated. These early results suggest a higher rate of response at day 56 than is typically observed with steroids alone. Inhibition of T-cell homing to the GI tract may improve GI GVHD response and potentially mitigate progression of acute GVHD. DisclosuresKoreth:Kadmon Corp: Membership on an entity's Board of Directors or advisory committees; Amgen Inc.: Consultancy; Prometheus Labs: Research Funding; Takeda Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Millennium Pharmaceuticals: Research Funding. Armand:Bristol-Myers Squibb: Consultancy, Research Funding; Tensha: Research Funding; Affimed: Research Funding; Sequenta/Adaptive: Research Funding; Merck & Co., Inc.: Consultancy, Research Funding; Roche: Research Funding; Genmab: Consultancy; Pfizer: Consultancy, Research Funding; Infinity: Consultancy; Otsuka: Research Funding; Sigma Tau: Research Funding. Antin:Gentium SpA/Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Cutler:Pfizer: Consultancy; Pharmacyclics: Consultancy; Kite: Consultancy; Bristol-Myers Squibb: Consultancy; Incyte: Consultancy; Astellas: Consultancy.

T Follicular Regulatory (TFR) Cell Deficiency during Chronic Graft-Versus-Host Disease Is Improved By Low-Dose IL-2 Therapy

Background: Chronic Graft versus Host Disease (cGVHD) reflects the inability to achieve immune tolerance after allogeneic stem cell transplantation (allo-SCT) resulting in the persistence of allo and auto-reactive T cells and B cells. We previously showed that regulatory T cells (Treg) are decreased in patients with cGVHD and may be rescued by low dose IL-2 therapy resulting in improved Treg number and survival and clinical improvement of cGVHD symptoms. More recently, we showed that circulating T follicular helper cells (cTFH) have increased function during cGVHD, thus stimulating B cells to produce auto and allo-antibodies involved in cGVHD. T follicular regulatory cells (TFR) regulate the germinal center (GC) reaction and suppress B cell differentiation and immunoglobulin secretion. TFR reside primarily in lymphoid tissues but also circulate in small numbers. In the present study we characterized the numbers and function of blood CD3+CD4+CD45RA-CD25hiFoxP3+CXCR5+ TFR in healthy donors (HD; N=18) and allo-SCT patients (N=64).Results: Patients undergoing allo-SCT showed a significant reduction of circulating TFR (cTFR) compared to HD (median: 0.08% vs 0.34% of CD4+T respectively, p<10-4). Moreover, patients with active cGVHD (N=37) had significantly lower cTFR frequency compared to patients with no cGVHD (N=15) (median: 0.034 vs 0.18% of CD4+, p=0.0012) and resolved cGVHD (N=12) (median: 0.034 vs 0.14, p=0.02). Interestingly, cTFR values tended to be negatively associated with cGVHD grade (median cTFR %: 0.11 vs 0.029, p=0.004 for mild vs moderate; 0.11 vs 0.012, p=0.005 for mild vs severe; 0.029 vs 0.012, p=0.2 for moderate vs severe). The numeric reduction of cTFR in cGVHD patients appears to be a consequence of decreased survival as attested by lower BCL-2 expression (median: 1831 vs 1939, p=0.037 in active cGVHD and without cGVHD, respectively). This favors the survival of TFH effector cells (CD4+CD45RA-CXCR5+ excluding CD25hiFoxP3+) as measured by the ratio of expression of BCL-2 in effectors/regulators in active compared to no cGVHD (BCL-2 E/R ratio: 1.26 vs 1.14, p=0.0013 respectively). Similar to tonsil TFR, blood TFR exhibit suppressive functions in in vitro assays. Purified TFR were co-cultured with TFH and memory B cells at different ratios. The addition of TFR was associated with a significant reduction of plasmablast (PB) generation (CD27hiCD38hiCD19+ cells) (Figure 1A, t-test: p=0.0087) and IgG production (Figure 1B, t-test: p=0.0087). Human cTFR in vivo display similar suppressive function toward B cells, as analysis of active cGVHD patients revealed an inverse correlation between TFR and PB frequency in the peripheral blood (Spearman test: r = -0.49, p=0.003) (Figure 1C). As IL-2 has been shown to enhance regulatory T cells, we assessed its impact on the GC reaction in vitro . Purified TFH and memory B cells from HD were co-cultured at different doses of IL-2 from 0 to 100 IU/mL, simulating a germinal center reaction in vitro . Low dose IL-2 starting at 10 IU/mL was associated with a suppressive effect on PB generation and IgG production that peaked at 50 IU/mL reflecting the high expression level of IL-2 high affinity receptor (CD25). We also evaluated the capacity of IL-2 to restore in vivo cTFR:cTFH ratio using mass cytometry (CyTOF) in a cohort of patients receiving IL-2 (1x106 IU/M2/day) for 12 weeks as previously described (Koreth et al, Blood 2016). We observed an improvement of blood cTFR:cTFH ratio over the course of IL-2 therapy, with a maximum ratio observed at 2 weeks, and subsequently decreasing to reach baseline values after stopping IL-2 (Figure 2).Conclusion: Our results confirm that blood TFR exert a suppressive function as evidence by an inverse correlation with PB and in vitro suppression of memory B cell Ig production. This suppressive subset is deficient in patients with cGVHD due to altered TFR survival, thus favoring imbalance toward TFH effectors which may promote a GC reaction in vivo resulting in PB and memory B cell pathogenic Ig production. By enhancing TFR, low-dose IL-2 therapy promotes effective control of the GC reaction. [Display omitted] DisclosuresForcade:Neovii: Other: Travel grant. Koreth:Millennium Pharmaceuticals: Research Funding; Amgen Inc.: Consultancy; Prometheus Labs: Research Funding; Kadmon Corp: Membership on an entity's Board of Directors or advisory committees; Takeda Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Nikiforow:Kite Therapeutics: Membership on an entity's Board of Directors or advisory committees. Armand:Roche: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Sequenta/Adaptive: Research Funding; Affimed: Research Funding; Merck & Co., Inc.: Consultancy, Research Funding; Sigma Tau: Research Funding; Otsuka: Research Funding; Pfizer: Consultancy, Research Funding; Infinity: Consultancy; Tensha: Research Funding; Genmab: Consultancy. Antin:Gentium SpA/Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees.

Optimizing Checkpoint Blockade As a Treatment for Relapsed Hematologic Malignancies after Allogeneic Hematopoietic Cell Transplantation

Optimizing Checkpoint Blockade As a Treatment for Relapsed Hematologic Malignancies after Allogeneic Hematopoietic Cell Transplantation

Extra-Corporeal Photopheresis Plus Low-Dose Interleukin-2 for Steroid-Refractory Chronic Graft-Vs.-Host Disease: Efficacy, Safety and Immune Correlates

CD4+CD25+FOXP3+ regulatory T cells (Treg) are dominant suppressors of innate and adaptive immune effector cells that enhance tolerance. Treg augmentation can control immune activation underlying chronic graft-versus-host disease (cGVHD). In prior studies, daily subcutaneous (SC) low-dose interleukin-2 (IL-2) therapy for 8-12 weeks induced preferential Treg expansion in-vivo, with objective clinical responses in over half of evaluable participants (NEJM 2011, Blood 2016). Alternative immunomodulatory approaches like extra-corporeal photopheresis (ECP) also have efficacy in cGVHD and may function via Treg augmentation. Combining ECP plus IL-2 could offer therapeutic synergy.We report on a prospective single arm phase 2 trial of twice-weekly ECP (weeks 1-16) plus sequential low-dose IL-2 (1x106 IU/m2/d SC, weeks 9-16) for treatment of steroid-refractory cGVHD. The study enrolled 25 participants (48% male, 88% HLA-matched, 100% PBSC grafts, 52% prior aGVHD). Median participant age was 62 years (range, 34-76). Median time from HSCT and from cGVHD onset to start of treatment was 919 days (range, 177-2842) and 524 days (range, 58-2697) respectively. Participants had a median of 3 cGVHD organ sites (range, 2-5). The median follow-up time in survivors is 16 months (range, 2.1-26).ECP plus IL-2 was well tolerated: 1 participant withdrew due to IL-2 adverse effects (AE) (myalgia, fatigue), and 3 were additionally unevaluable (1 cardiac arrest; 1 parainfluenza infection, 1 still undergoing treatment). None required IL-2 dose reduction. There were four grade 3 AEs during the 16-week study (1 participant had dehydration/hypotension/syncope, possibly IL-2-related;1 had ECP-related anemia). None experienced relapse. At week 16, cGVHD objective partial responses (PR) were documented in 14 of 21 evaluable participants (67%). None had cGVHD progression. Response sites included skin (n=9/18), joint/fascia/muscle (n=7/16), liver (n=1/1), lung (n=2/9), and GI tract (n=3/5). 18 participants with clinical benefit (PR, and stable disease with minor response) proceeded to extended ECP plus IL-2 therapy.Immunologically, 8 weeks of ECP alone did not induce significant changes in buffy coat WBC or absolute lymphocyte count (ALC). Peripheral blood CD3 T cell counts/µL fell, with a median CD8 and CD4 conventional T cell (Tcon) decrement of -109 (Q1, Q3: -220, -13; p<0.001) and -68 (Q1, Q3: -244, -19; p=0.023), respectively, at week 8 (Figure 1A). There was an early fall in Treg cell counts/µL, with a median decrement of -4 (Q1, Q3: -9, 0; p=0.033) at week 4, without change in NK or B cell counts or Treg:Tcon ratio. The addition of low-dose IL-2 thereafter induced a >5-fold increase in median Treg count/µL (p<0.001), from a baseline of 9 (Q1, Q3: 5, 17) at week 8 to a peak of 72 (Q1, Q3: 22, 186) at week 10, plateauing at 50 (Q1, Q3: 33, 71) at week 16 (Figure 1A). No significant change in CD4 Tcon or B cell count was noted. NK cell count increased 1.7-fold (p=0.009). The median Treg:Tcon ratio increased 4-fold (p<0.001): from a baseline of 0.06 (Q1, Q3: 0.03, 0.08) at week 8 to a peak of 0.26 (Q1, Q3: 0.12, 0.42) at week 12, and remained elevated at 0.17 (Q1, Q3: 0.14, 0.34) at week 16 (Figure 1B). Treg count and Treg:Tcon ratio remained elevated in responders during extended ECP plus IL-2 therapy.Immunologically, clinical responders had a higher median Treg count/µL vs. non-responders after 1 and 6 weeks of IL-2 therapy (21 vs. 11, p<0.001; 73 vs. 29, p=0.016 respectively). Treg:Tcon ratio at week 2 and 6 after IL-2 therapy was also higher in responders (0.29 vs. 0.15, p=0.038; 0.28 vs. 0.13, p=0.016 respectively). Applying our previous cutoffs (Blood 2016), Treg:Tcon ratio ≥0.2 after 1 week of IL-2 was also predictive of clinical response (p=0.05).In summary, in steroid-refractory cGVHD, ECP was associated with a fall in peripheral CD8, CD4 Tcon, and Treg counts. The addition of low-dose IL-2 thereafter induced profound Treg and NK cell augmentation. Clinical responses (PR) to combination ECP plus IL-2 therapy were documented in 67% of the evaluable participants. Those with early rise in Treg count and Treg:Tcon ratio after the addition of IL-2 were likelier to benefit. However, the overall clinical efficacy of ECP plus IL-2 did not appear markedly higher than low-dose IL-2 alone. [Display omitted] DisclosuresKoreth:Prometheus Labs: Research Funding; Kadmon Corp: Membership on an entity's Board of Directors or advisory committees; Millennium Pharmaceuticals: Research Funding; Takeda Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Amgen Inc.: Consultancy. Armand:Bristol-Myers Squibb: Consultancy, Research Funding; Merck & Co., Inc.: Consultancy, Research Funding; Sequenta/Adaptive: Research Funding; Sigma Tau: Research Funding; Tensha: Research Funding; Affimed: Research Funding; Roche: Research Funding; Pfizer: Consultancy, Research Funding; Genmab: Consultancy; Infinity: Consultancy; Otsuka: Research Funding. Antin:Gentium SpA/Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees.

Genetic Ontogeny Defines Distinct Prognostic Subgroups in AML Patients Age 60 and Older Following Hematopoietic Stem Cell Transplantation

▪BackgroundThe prognosis for older adults diagnosed with acute myeloid leukemia (AML) is poor. The response to conventional chemotherapy in these patients is frequently brief, and long-term survival is largely limited to those who undergo allogeneic hematopoietic stem cell transplantation (HSCT). However, mortality after transplantation HSCT is also high, with deaths attributable both to relapsed AML and to transplant-related complications. There is thus a critical need for strategies that can reliably discern older AML patients who are most likely to benefit from current transplantation approaches and those for whom novel approaches should be developed.We have previously shown that genetic characteristics can divide AML patients into three clinically distinct categories: (1) TP53 -mutated AML; (2) “secondary-type” AML, defined by mutations in any of eight genes with high specificity for the presence of antecedent myelodysplastic syndrome; and (3) “de novo” type AML, defined by absence of TP53 and secondary-type mutations. We showed that older patients with de novo-type AML have improved response to standard induction chemotherapy and significantly superior event-free survival than those with either secondary-type or TP53- mutated AML. Since disease burden prior to HSCT has been linked to post-HSCT outcomes, we hypothesized that diagnostic ontogeny classification would be associated with relapse and survival among older AML patients receiving HSCT in first complete remission.MethodsWe identified AML patients age 60 or older who underwent HSCT at Dana-Farber Cancer Institute (DFCI; Boston, MA) in first complete remission between 2012-2016, for whom next-generation sequencing of the diagnostic AML sample was available. Based on targeted gene panel sequencing of recurrent myeloid driver alterations, we classified AML as TP53 -mutated, secondary-type (SRSF2, SF3B1, U2AF1, ZRSR2, BCOR, ASXL1, EZH2, or STAG2 mutations), or de novo type (neither TP53 mutation nor secondary-type mutations). We extracted data on clinical outcomes from the medical record and assessed the impact of diagnostic AML genetics on overall survival and cumulative incidence of relapse following HSCT.ResultsFifty-five patients met inclusion criteria, with a median age of 67 (range 60-76). All had received intensive induction chemotherapy; nine (16.4%) received myeloablative conditioning regimens, while the remainder received reduced intensity regimens. Of the 55 patients, 13% (n=7) had TP53 mutations, 40% (n=22) had secondary-type mutations, and 47% (n=26) had de-novo type mutations. Patients with de-novo type mutations had significantly superior 2-year overall survival than those with secondary-type mutations, who in turn had significantly superior survival than those with TP53 mutations (82.2% versus 48.1% versus 14%, p<0.001 for all comparisons, Figure 1A). These differences reflected a significant difference in the 2-year cumulative incidence of relapse following HSCT (100% for TP53 versus 56.7% for secondary-type versus 33.4% for de-novo type mutations, p<0.001 for all comparisons, Figure 1B).ConclusionIn our cohort of older AML patients who underwent HSCT in first complete remission after intensive induction chemotherapy, genetic ontogeny classification at the time of diagnosis was significantly associated with overall survival and rate of relapse after HSCT. Our findings, which merit further evaluation in a larger cohort, suggest that genetic classification of ontogeny can form the basis of a robust prognostic model that accurately predicts post-HSCT outcomes in older AML patients. [Display omitted] DisclosuresKoreth:Amgen Inc.: Consultancy; Millennium Pharmaceuticals: Research Funding; Prometheus Labs: Research Funding; Kadmon Corp: Membership on an entity's Board of Directors or advisory committees; Takeda Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Nikiforow:Kite Therapeutics: Membership on an entity's Board of Directors or advisory committees. Armand:Sigma Tau: Research Funding; Sequenta/Adaptive: Research Funding; Affimed: Research Funding; Infinity: Consultancy; Bristol-Myers Squibb: Consultancy, Research Funding; Genmab: Consultancy; Roche: Research Funding; Pfizer: Consultancy, Research Funding; Merck & Co., Inc.: Consultancy, Research Funding; Tensha: Research Funding; Otsuka: Research Funding. Antin:Gentium SpA/Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees. Lindsley:MedImmune: Research Funding; Jazz Pharmaceuticals: Consultancy; Takeda Pharmaceuticals: Consultancy.