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Introduction: Telemedicine has been widely utilized in the healthcare marketplace since the beginning of the COVID-19 pandemic. Over the last 3 years, virtual care has been widely employed in the care of patients with polycythemia vera (PV), essential thrombocythemia (ET) and myelofibrosis (MF) at Mayo Clinic. These rare disorders have few experts; therefore, telemedicine becomes an optimal approach for patients receive expert care even when they are not close to the medical center. 1 Additionally, telemedicine reduces financial burden for the patients. We aim to estimate potential cost savings to patients utilizing telemedicine. Methods: We identified patients with MPN seen at Mayo Clinic, Arizona who have had at least 2 visits (1 or more virtual visits) between March 2020 and June 2022. We extracted retrospective data from electronic medical records (EMR) including sociodemographic data, disease related data and number of visits - both virtual and in person - of the patients identified. The address recorded from the EMR was assumed to be the patient's location at the time of virtual visit. Driving distances were determined using zip codes in Google Maps and the patients were stratified into quartiles based on round trip travel distances. Patients in quartiles 1 through 3 were assumed to have driven while patients in quartile 4 were assumed to have traveled by plane. Patients in quartile 1 were assumed to have 1 travel day including the follow-up visit and no accommodation, patients in quartile 2 were assumed to have 2 travel days including the follow up visit and 1 night of accommodation whereas patients in quartiles 3 and 4 were assumed to have 2 travel days, 1 day for the follow up visit and 2 nights of accommodation. Mileage rate costs were based on US Internal Revenue Service (IRS) standard mileage rates for medical or moving purposes for 2021. 2 Owing to extreme variability in flight costs, flying costs were assumed to be equal to the driving costs. Per diem costs for accommodation and meals and incidentals were based on the US General Services Administration (GSA) 2021 rates for Phoenix 3 with the cost being 75% of the full per diem rate on traveling days via GSA formulaic approach. Results: One hundred and eight patients having 282 virtual visits were identified. Patients ranged from 30 - 87 years with the mean and median age of 65 years and 67 years respectively. Majority of the patients were female (62%) and white (98%) with gender distribution varying by distance. Descriptive statistics of the estimated out-of-pocket costs for patients by distance quartiles are summarized in Table 1a. Mean estimated cost savings ranged from $46.8 to $877.3 with the savings of $43.8 - $1372.2 at extremes. The total cost savings by all patients was $90,306.7. The breakdown of costs by category for each quartile is shown in Table 1b which shows that the majority of costs saved by patients in quartile 1 were due to avoiding costs spent on meals and incidentals (~90% of mean costs) whereas costs saved due to meals and incidentals for patients in quartile 4 were only ~16% of the mean costs. Conclusions: Our research highlighted telemedicine as a cost-effective approach for patients with MPN who received virtual care from March 2020 - June 2022. Study limitations included not weighing costs for childcare or accompanying individuals and using driving costs instead of flying costs, however, these considerations potentially underestimate the actual cost savings to the patient. Additionally, since the median age of this population was 65, we didn't include loss of wages to the analysis, which may further underestimate the costs. Despite concerns over billing, reimbursement, and state licensure, virtual care is being established as a critical part of medicine moving forward. 1. Doolittle, G.C. and A.O. Spaulding, Providing Access to Oncology Care for Rural Patients via Telemedicine. Journal of Oncology Practice, 2006. 2(5): p. 228-230. 2. Internal Revenue Service. Standard mileage rates for 2021. Available at: https://www.irs.gov/tax-professionals/standard-mileage-rates 3. US General Services Administration. Per diem rates. Available at: https://www.gsa.gov/travel/plan-book/per-diem-rates/per-diem-rates-results?action=perdiems_report&fiscal_year=2021&state=AZ&city=&zip=85054

Background: Relapsed DLBCL occurs in up to 40% of patients and has a poor prognosis. Current prognostic tools such as the international prognostic index (IPI) and newer forms (NCCN-IPI) only include baseline clinical features. PET/CT features have not yet been incorporated into prognostic risk models despite being essential for staging and response assessment. Deep learning computer algorithms have consistently demonstrated the ability to analyze imaging data and identify features that are not readily apparent to the human eye. Using a deep learning computer vision model that automatically extracted radiomic features from PET/CTs, we examined the association of changes between baseline PET and interim PET (PET2) radiomic features on survival outcomes and compared the prognostic performance with NCCN-IPI. Methods: Adult patients with newly diagnosed diffuse large B-cell lymphoma (DLBCL) between 2005 and 2015 and enrolled in the prospective MER cohort were included. Native DICOM images from FDG PET/CT scans at baseline and interim PET (PET2, after 2-3 cycles of chemotherapy) were preprocessed for regularity and then segmented using the nnU-Net architecture with an external lymphoma-specific model. Feature extraction and standard uptake value (SUV) characterization were accomplished with PyRadiomics and NiBabel. Our computational method included no manual segmentation correction. Individual radiomics features (n=115) and the % change above (Δ High) and below (Δ low) 50 th quartile from baseline to PET2 were evaluated for association with event free survival (EFS) and overall survival (OS) using a univariate Cox regression model and by Kaplan Meier analysis. EFS was defined as time from PET2 to first systemic relapse or death from any cause. OS was defined as time from PET2 to death from any cause. Additionally, Spearman and Pearson correlation matrices were used to guide feature selection while minimizing collinearity. We then assessed the association of the highest scoring radiomics features with EFS in a multivariate cox regression model. Results: A total of 506 patients had baseline and PET2 scans available for radiomic feature extraction. Median age at diagnosis was 61 years (range 18-90), 43% were females. NCCN-IPI composition and outcomes of our cohort was comparable to the previously published NCCN cohort, with patient distribution and 5-year OS as follows: Low (9%, 5-y OS 83%), Low-intermediate (38%, 5-y OS 49%), High-intermediate (41%, 5-y OS 31%), High (11%, 5-y OS 12%). At a median follow up of 81 months,there were 308 events, and272 patients had died.Several radiomics features were associated with EFS including change in tumor surface area (SA Δ) (HR: 1.75, 95% CI 1.36-2.24, p<0.005, median of 26,927 mm 2, Figure 1A) and change in total metabolic tumor volume (TMTV Δ) (HR: 1.64, 95% CI 1.27-2.10, p<0.005, median of 120,473 mm 3, Figure 1B). As a reference, NCCN-IPI univariate Cox regression analysis of EFS produced a Harrell's C-statistic (c) of 0.624. Single radiomics features of SA Δ and TMTV Δ individually produced unadjusted c-statistics of 0.616 and 0.614 respectively. Combinations of radiomics features (SA Δ, TMTV Δ and NCCN-IPI classification) demonstrated cumulative benefit (c=0.652). Conclusion: Automatic PET-CT radiomic feature extraction using deep learning models is feasible among patients with newly diagnosed DLBCL. The change in tumor SA and TMTV appear to be promising radiomic biomarkers. A low decline in either tumor SA or TMTV by PET2 is associated with higher risk of relapse and poor survival outcomes. As individual characteristics, these features are similar prognostic indicators of EFS as the NCCN-IPI. Further investigation into risk stratification when combining radiomics with clinical and genomic variables is warranted. Figure 1. Event free survival for DLBCL patients with A) a change in tumor surface area by PET2 less than 50% percentile (SA_Δ Low) and greater than 50 th percentile (SA_Δ High) and B) a change in TMTV by PET2 less than 50% percentile (TMTV_Δ Low) and greater than 50 th percentile (TMTV_Δ High).

Introduction: ISB 1342 is a humanized CD38xCD3 bispecific T-cell engager using Ichnos proprietary Bispecific Engagement by Antibodies based on the T cell receptor (BEAT ®) platform, designed to simultaneously bind CD38 on multiple myeloma (MM) cells and CD3ε on T cells, to induce tumor killing. This mechanism of action is different from existing monospecific CD38 targeting therapies and was designed to overcome resistance to daratumumab in MM. ISB 1342 exhibits potent killing of the primary MM cells and MM cell lines with low sensitivity to daratumumab ( Pouleau B. et al. Blood 2023; 142 (3): 260-273). We report here, the updated findings from the weekly dose-escalations of intravenous (IV) and subcutaneous (SC) injections of an ongoing, single-agent phase 1 study (NCT03309111) of ISB 1342 in patients with RRMM. Methods: Adult patients with RRMM that relapsed after or were refractory to prior therapies, including a proteasome inhibitor, an immunomodulatory drug, and an anti-CD38 antibody; received ISB 1342 on a weekly (QW) schedule by IV or SC injection with a priming dose on the first day in 2 parallel dose-escalation schemas. Patients had measurable disease per the International Myeloma Working Group (IMWG) criteria (2016). Dose escalation in the QW schedule began at 0.2/0.3 mg/kg priming/treatment dose and followed a “3 + 3” design. The primary study objectives are to determine the maximum tolerated dose (MTD) and select a recommended phase 2 dose (RP2D) of ISB 1342. Secondary objectives includ evaluation of anti-myeloma activity, pharmacokinetics (PK), pharmacodynamics, and immunogenicity of ISB 1342. Results: As of July 18, 2023, based on ongoing clinical database, 39 subjects had received weekly IV infusions of ISB 1342 in 8 dose-escalation groups from 0.2/0.3 mg/kg to 4.0/16.0 mg/kg as priming/treatment dose; and 7 additional subjects had received weekly SC injections at 2.0/8.0 mg/kg. Two different formulations have been tested in SC group. Median number of cycles administered was 2. The majority were male (57%) and white (74%); 13% were Black or African American. The median age was 69 years (range, 54-76) and the median time since diagnosis was 6.6 years (range, 2.8-22.2). The median number of prior anti-myeloma lines of therapy was 6 (range 1-12). Twenty-one (67%) subjects were considered to be triple-class refractory and 18 (48%) penta-drug refractory. Forty-one (89%) subjects experienced treatment-related adverse events (TRAEs) of any grade. Most TRAEs were grade 1-2, including infusion related reactions (37%), cytokine release syndrome (CRS, 34%, all grade 1or 2), anemia (24%), neutropenia (24%), and thrombocytopenia (17%). Five subjects in SC group (71% of SC) had injection site reaction, all grade 1 or 2. Grade 3 or higher TRAEs occurring in more than 5% of subjects were infusion related reaction (no grade 4), anemia (no grade 4), neutropenia, leukopenia. No Grade 5 TRAE was observed. After QW IV infusion, ISB 1342 serum concentration peaked at the end of infusion and then showed bi-exponential decline. ISB 1342 serum exposures increased in a dose linear fashion across the tested IV infusion dose range. The limited PK data after SC injection suggest slow presentation of ISB 1342 into the systemic circulation leading to lower C max and delayed T max relative to IV. Transient increases in serum cytokines were observed within 24 hours after ISB 1342 dosing, including IFNg, TNFa, IL-2, IL-6 and IL-10. Transient increases in T-cell activation were observed by flow cytometry at 24-48 hours after ISB 1342 dosing at 1.0 / 4.0 μg/kg and above, based on increased expression of CD69 on peripheral blood CD4+ and CD8+ T-cell populations (Figure 1). Comparison of the available data from subjects treated at 2 / 8 μg/kg (Cohort 109) indicated reduced T-cell activation following SC compared to IV administration of ISB 1342. The efficacy signals observed in Cohorts 108 and 109 are consistent with the estimates of the lower boundary of the predicted efficacious dose range using a quantitative systems pharmacology (QSP) model based on preclinical data. Updated clinical data, including response rates and safety data, will be present at the meeting. Conclusions: Treatment with ISB 1342 was well tolerated at higher dose levels evaluated. Observed CRS events were moderate. No increased risk of infection has been observed . Updated safety, efficacy, biomarker and PK data will be presented.

Introduction The Blood and Marrow Transplant Clinical Trials Network 1102 study (BMT CTN 1102, NCT02016781) was a multicenter, biologic assignment trial, where patients aged 50-75 with intermediate-2 or high risk de novo myelodysplastic syndrome (MDS) were assigned to reduced-intensity allogeneic hematopoietic cell transplantation (alloHCT) or best supportive care (non-alloHCT) based on donor availability. A parallel economic evaluation was performed alongside BMT CTN 1102. Here, we report on the financial impact of the treatment protocol on patients using a prospective cost diary study conducted within the trial. Methods BMT CTN 1102 enrollees were offered the option to participate in the parallel cost diary study at the same time of primary study enrollment. The cost diary survey instrument, comprised of 19 questions, covered the domains of out-of-pocket (OOP) costs of healthcare and financial hardship indicators. Surveys were distributed at 1- (1M), 7- (7M), and 19-months (19M) after enrollment. Study participants were grouped by actual treatment received, rather than group assignment. Responses were analyzed using univariate Fisher's exact and Wilcoxon rank sum tests for association. Results Out of 216 enrollee invitations, 138 patients (64%) returned at least one survey. Total completed surveys at the 1M, 7M, and 19M timepoints were 103 (39%), 93 (35%), and 71 (27%), respectively. 50 (36%) completed only one survey, while 41 (39%) completed surveys at all three timepoints. Of all respondents, median age was 67.7 years (IQR: 64.8-70.3), 88 (64%) were male, 128 (93%) white, and 126 (91%) were non-Hispanic. Among respondents of the 1M, 7M and 19M surveys, 82 (80%), 78 (84%), 65 (92%) received alloHCT, respectively. Mean OOP costs by category are presented in Table 1. While alloHCT patients experienced higher OOP costs compared to non-alloHCT patients across all categories (outpatient services, prescription medications, and accommodations for healthcare), none of the comparisons were statistically significant. However, total OOP costs were significantly higher among alloHCT patients at 1 and 7 months (mean over past 30 days, 1M: $889 vs. $217, p=0.046; 7M: $678 vs. $349, p=0.03; 19M: $328 vs. $103, p=0.15). Financial hardship indicators are presented in Table 2. While alloHCT patients experienced greater financial hardship compared to non-alloHCT patients across all categories (mobilized reserve funds, borrowed money to pay for care, developed debt due to care), none of the comparisons were statistically significant. However, alloHCT patients were significantly more likely to experience at least one of these factors of financial hardship at 7 months (1M: 38% vs. 19%, p=0.13; 7M: 42% vs. 13%; p=0.04; 19M: 37% vs. 0%, p=0.08). Discussion Patients with MDS who received alloHCT incurred substantially more OOP costs overall compared to patients who did not receive alloHCT, most notably for accommodations related to alloHCT. Similarly, alloHCT patients were more likely to develop financial hardship, including mobilizing reserve funds, borrowing money, and developing debt. These findings demonstrate that treatment-related OOP expenditures associated with alloHCT are substantial and may pose significant burdens for some populations receiving alloHCT. Financial navigation and assistance, which have been shown to help patients address cost burden in solid tumor settings, should be considered for MDS patients prior to alloHCT. Small final sample sizes limited our analyses significantly; further research into OOP costs and financial hardship among larger cohorts of alloHCT patients are necessary to confirm these findings. Acknowledgement Support for this study was provided by grants #U10HL069294 and #U24HL138660 to the Blood and Marrow Transplant Clinical Trials Network from the National Heart, Lung, and Blood Institute and the National Cancer Institute. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Introduction: Brexucabtagene autoleucel (brexu-cel) is an autologous anti-CD19 chimeric antigen receptor (CAR) T cell therapy approved for adults with relapsed/refractory B-cell acute lymphoblastic leukemia (R/R B-ALL). Bridging therapy, defined as anti-leukemia therapy given between apheresis and lymphodepleting chemotherapy, was permitted on the pivotal ZUMA-3 trial. The optimal bridging therapy is unknown in this setting. Here we report patient and disease characteristics in those receiving bridging therapies prior to brexu-cel and the impact of bridging on clinical outcomes in a large multicenter cohort. Methods and Results: ROCCA includes 25 US institutions contributing retrospective data from 152 B-ALL patients treated with standard of care brexu-cel between 2021-2023. Ninety-nine patients (65%) received bridging therapy, while 53 patients (35%) received no bridging therapy. Bridging therapy consisted of cytotoxic chemotherapy ( n=65, 66%), immunotherapy ( n=26, 26%; 23 inotuzumab, 3 blinatumomab), tyrosine kinase inhibitors (TKI) ( n=20, 20%; 16 ponatinib), steroids only ( n=10, 10%), and intrathecal chemotherapy ( n=22, 22%). The median age of the cohort was 46 (IQR 32-61). Patients were heavily pre-treated with a median of 4 prior lines of therapy. The median days from apheresis to infusion was 33 (IQR 26-42). 119 patients had known pre-apheresis blast counts; the bridging group had higher pre-apheresis blast burden, with 21 of 76 patients (28%) having ≥ 50% blasts compared to only 5 of 43 patients (12%) in the no bridging group ( p=0.02). In addition, more patients who received bridging had pre-apheresis extramedullary disease (32% vs. 15%, p=0.02). All other baseline characteristics were similar between the two groups (Table 1). Fifty-four (54%) patients had response assessment after bridging therapy and prior to brexu-cel infusion. In patients who received inotuzumab for pre-apheresis active disease, defined as ≥ 5% blasts, 6 of 13 (46%) who had post-bridging assessment achieved a complete response (CR; 5 measurable residual disease (MRD)+, 1 MRD-), with a mean proportional reduction in blast burden of 46% from baseline. In contrast, after chemotherapy bridging, only 2 of 16 patients (13%) with pre-apheresis active disease had a CR. Patients receiving chemotherapy bridging had a mean proportional increase in blast burden of 4.4%. In recipients of TKI bridging, 2 of 4 patients (50%) with pre-apheresis active disease had a CR. Compared to no bridging, patients in the bridging group had similar rates of grade 3 or 4 CRS (9% bridging vs. 8% no bridging, p=0.73) and grade 3 or 4 ICANS (34% vs. 26%, p=0.32). In univariate analysis, there was no statistically significant difference in day 28 response with 63 patients (72%) achieving MRD- complete response in the bridging group as compared to 36 patients (78%) in the no bridging group ( p=0.60). Non-relapse mortality was similar between the two groups (17% bridging vs. 9% no bridging, p=0.20). Overall survival (OS) and progression-free survival (PFS) were superior in the no bridging group: 1-year OS 74.7% vs 56.8% (log-rank p=0.04), and 1-year PFS 57.3% vs 41.7% (log-rank p=0.04). In a multivariate analysis stratified by bridging and pre-apheresis disease burden, patients with pre-apheresis blasts ≥ 5% and bridging had worse survival than ≥ 5% blasts and no bridging: 1-year OS 45.3% vs. 87.5% and 1-year PFS 27.7% vs. 64.3% (Figure 1). However, patients with < 5% blasts had similar survival regardless of bridging. Conclusions: In our real-world analysis, adults with R/R B-ALL receiving bridging therapy had a higher disease burden at baseline. Despite greater baseline disease, there were no significant differences in toxicity and day 28 response in those receiving bridging therapy vs. not. While survival was inferior in patients with pre-apheresis active disease who received bridging, this may be confounded by the degree of tumor burden. In patients with < 5% blasts pre-apheresis, bridging did not impact survival. Furthermore, inotuzumab bridging demonstrated the most significant disease debulking. However, the comparisons in this study are limited by the variability in practice for post-bridging disease reassessment and the small proportion of patients with active disease who did not receive bridging. A more uniform approach to peri-CAR disease assessment would enable more robust study of optimal bridging strategies.

Background: Guidelines recommend placement of inferior vena cava (IVC) filters in patients with acute thrombotic episodes and a concurrent contraindication to anticoagulation, however filter placement during or immediately postpartum presents significant technical challenges. The use and complications of IVC filters in the peripartum period is poorly documented in current literature. Objective(s): To evaluate the use of and outcomes related to IVC filters in an obstetric population at a large tertiary care center. Study Design: Retrospective review of all patients at a tertiary academic medical center from 2001-2016 who either conceived with an IVC filter in place or underwent IVC filter placement during the antepartum or postpartum interval. Manual abstraction of each chart was performed, with data stored in a RedCap database. Results: A total of 24 patients were included in the final analysis: 5 with IVC filter placement prior to pregnancy, 7 with antepartum placement, and 12 with postpartum placement. One patient had multiple pregnancies during our study timeframe and was therefore included twice. The cohort of postpartum placement were the youngest mean age (23.7 years), had a higher number of IVC filters placed for polytrauma (n=4), and had the shortest time to removal (135.9 days). The vast majority (91.3%) of IVC filters placed during pregnancy were retrievable filters in the suprarenal position, while most deployed in an infrarenal position (83.3%) when placed prior to conception. Complications encountered included multiple attempts to remove IVC filter, severe angulation, embedded struts, fracture, and one case of cardiac tamponade during filter placement requiring emergent sternotomy and evacuation. Of the filters requiring multiple attempts for removal, in 1 patient (4%) it was unable to be removed despite multiple attempts and the filter was ultimately left in situ. Complications were more common when placement was performed prior to pregnancy or antepartum (40% and 57.1% respectively) versus postpartum (16.7%). From an obstetrical perspective, 1 patient (4%) required early preterm delivery due to preeclampsia; 1 maternal death occurred in a postpartum patient who experienced a massive pulmonary embolism and subsequently died despite emergent thrombectomy and IVC filter placement, and 1 neonatal death occurred due to congenital heart disease following periviable preterm delivery. Conclusion(s): In our study across 16 years at a large academic medical center we identified 23 patients who had an IVC filter placed prior to pregnancy or placed during the antepartum or postpartum periods. Data from our experience suggested a higher incidence of complications with preconceptual and antepartum placement, although the majority of these did not impact clinical outcomes. While not frequently needed, IVC filters remain an option for clinicians treating pregnant and postpartum patients but should be considered a last resource as they can lead to various complications.

Background Socioeconomic status (SES) is associated with cardiovascular health (CVH). Potential differences by sex in this association remain incompletely understood in Black Americans, where SES disparities are posited to be partially responsible for cardiovascular inequities. The association of SES measures (income, education, occupation, and insurance) with CVH scores was examined in the Jackson Heart Study. Methods and Results American Heart Association CVH components (non–high‐density‐lipoprotein cholesterol, blood pressure, diet, tobacco use, physical activity, sleep, glycemia, and body mass index) were scored cross‐sectionally at baseline (scale: 0–100). Differences in CVH and 95% CIs (Estimate, 95% CI) were calculated using linear regression, adjusting for age, sex, and discrimination. Heterogeneity by sex was assessed. Participants had a mean age of 54.8 years (SD 12.6 years), and 65% were women. Lower income, education, occupation (non‐management/professional versus management/professional occupations), and insurance status (uninsured, Medicaid, Veterans Affairs, or Medicare versus private insurance) were associated with lower CVH scores (all P <0.01). There was heterogeneity by sex, with greater magnitude of associations of SES measures with CVH in women versus men. The lowest education level (<high school) versus highest (>high school) was associated with 8.8‐point lower (95% CI: −10.2 to −7.3) and 5.4‐point lower (95% CI: −7.2 to −3.6) CVH scores in women and men, respectively (interaction P =0.003). The lowest (<25 000) versus highest level of income (≥$75 000) was associated with a greater reduction in CVH scores in women than men (interaction P =0.1142). Conclusions Among Black Americans, measures of SES were associated with CVH, with a greater magnitude in women compared with men for education and income. Interventions aimed to address CVH through SES should consider the role of sex.

Abstract Hydrogen sulfide (H 2 S) is a gaseous inflammatory mediator and important signaling molecule for maintaining gastrointestinal (GI) homeostasis. Excess intraluminal H 2 S in the GI tract has been implicated in inflammatory bowel disease and neurodegenerative disorders; however, the role of H 2 S in disease pathogenesis and progression is unclear. Herein, an electrochemical gas‐sensing ingestible capsule is developed to enable real‐time, wireless amperometric measurement of H 2 S in GI conditions. A gold (Au) three‐electrode sensor is modified with a Nafion solid‐polymer electrolyte (Nafion‐Au) to enhance selectivity toward H 2 S in humid environments. The Nafion‐Au sensor‐integrated capsule shows a linear current response in H 2 S concentration ranging from 0.21 to 4.5 ppm ( R 2 = 0.954) with a normalized sensitivity of 12.4% ppm −1 when evaluated in a benchtop setting. The sensor proves highly selective toward H 2 S in the presence of known interferent gases, such as hydrogen (H 2 ), with a selectivity ratio of H 2 S:H 2 = 1340, as well as toward methane (CH 4 ) and carbon dioxide (CO 2 ). The packaged capsule demonstrates reliable wireless communication through abdominal tissue analogues, comparable to GI dielectric properties. Also, an assessment of sensor drift and threshold‐based notification is investigated, showing potential for in vivo application. Thus, the developed H 2 S capsule platform provides an analytical tool to uncover the complex biology‐modulating effects of intraluminal H 2 S.

Abstract Background Interleukin 6 (IL-6) plays important roles in both innate and adaptive immunity, while dysregulated persistent production of IL-6 is involved in pathological development of various diseases associated with inflammation. Targeting the IL-6 pathway has led to many innovative treatment approaches. Siltuximab and Tocilizumab are monoclonal antibodies targeting IL-6 and IL-6 receptors respectively and have been FDA-approved for treatment of Castleman disease (Siltuximab), a rare lymphoproliferative disorder characterized by hyperproduction of IL-6 with an unknown prevalence, autoimmune diseases such as rheumatoid arthritis (Tocilizumab), and both shown potential as treatment for cytokine release syndrome in hospitalized COVID-19 patients. However, the presence of siltuximab can interfere with IL-6 assays, leading to the use of C-reactive protein (CRP) as a surrogate marker to monitor its efficacy. Aim To evaluate potential Siltuximab and Tocilizumab antibody interference on IL-6 measurements in three different IL-6 protein immunoassays. Method: Serum or EDTA plasma sample pools with different IL-6 concentrations ranging from low (2.3 – 11.1 pg/mL, around the reference interval cut-off for each assay) to high (18.5 – 1142 pg/mL), above reference interval cut-off for each assay) were utilized. Various concentrations of Siltuximab or Tocilizumab were spiked into the sample pools (at 10% of total volume) to achieve final concentrations up to 600 µg/mL and up to 300 µg/mL, respectively. Sample spiked with 10% saline were used as no-drug control. Three assays were used to measure IL-6 concentration: Beckman Access IL-6 assay on UniCel DxI 800 (Beckman Coulter), V-PLEX Plus human IL-6 assay on QuickPlex SQ120 (Meso Scale Diagnostics), and a Luminex cytokine panel assay developed in house (R&D systems) with upper reference interval limits of 6.4,1.8 and 5 pg/mL respectively. Results Siltuximab interfered with the measurement of IL-6 for all three assays. A significant interference (&gt; 20% reduction) was observed at even a very low siltuximab concentrations in all three assays (0.05 µg/mL). In the presence of 5 µg/mL or greater Siltuximab, a maximum reduction of 93%, 83%, and 40% was observed for Beckman Access, R&D Luminex assay, and V-PLEX Plus Mesoscale assay, respectively. Tocilizumab did not interfere with the measurement of IL-6 in the three assays when serum was spiked with up to 300 µg/mL of the drug. Conclusion Siltuximab falsely reduce the measured IL-6 concentration on all three immunoassays tested in this study to differing degrees, whereas Tocilizumab does not. Consider the therapeutic range of Siltuximab (84 to 332 µg/mL) for treatment of Castleman disease, and a half-life of 20.6 days, measurement of IL-6 may not be useful in Siltuximab treated patients for an extended time-period.