The conjugation of biological drugs with polyethylenglycole is widely used to reduce their immunogenicity, thereby enhancing the safety and efficacy of the drugs. For instance, some extended half-life drugs for hemophilia A patients are PEGylated FVIII products. Unfortunately, it was observed that PEG itself, whether derived from PEGylated drugs or present in everyday products (such as cosmetics or medical devices) may induce the production of anti-PEG antibodies, resulting in hypersensitivity reactions and/or loss of efficacy of PEGylated drugs. There is therefore a demand for cost-effective and rapid point-of-care (POC) measurements. To this end, a POC device based on the principle of surface plasmon resonance (SPR) is here presented. The sensor chip is functionalized directly with PEG chains via thiol chemistry and inserted into a holder manufactured in 3D printing technology. The functionalization process has been optimized to recognize anti-PEG antibodies (both IgG and IgM isotypes) and characterized using X-ray Photoelectron Spectroscopy and contact angle measurements. Dose-response curves were obtained using commercially available antibodies, both in buffer solution and in diluted human serum, achieving a limit of detection in the nanomolar range. The reusability of the optical chip was also evaluated and, as proof of concept, plasma from control subjects and hemophilia A patients treated with PEGylated FVIII were measured, comparing the results with standard techniques such as a commercial SPR instrument and an enzyme-linked immunosorbent assay. The results were obtained within 15 min from tenfold diluted human plasma, paving the way for an easy-to-use, small-sized, portable, and low-cost POC device capable of detecting anti-PEG antibodies.

Background: Emicizumab is licensed for treatment of people with hemophilia A (HA) of all ages, with and without factor (F)VIII inhibitors. It is well tolerated, and most of the treatment-related adverse events are of mild intensity and transient. As for other therapeutic proteins, the potential of emicizumab to induce anti-drug antibodies (ADAs) should be considered when a decrease in treatment efficacy is observed. Data from 7 phase 3/3b pivotal studies showed that 5.1% of treated patients developed ADAs, <1% being activity neutralizing. Among them, 1 case required discontinuation of emicizumab due to loss of treatment efficacy. To date, among several thousands of patients treated with emicizumab, 5 cases of ADAs requiring treatment discontinuation have been reported. Objectives: Monitoring anti-emicizumab antibodies in 67 subjects with congenital HA who switched to emicizumab prophylaxis from FVIII products or bypassing agents. Methods: The anti-emicizumab antibodies were tested, depending on patient availability, at baseline and longitudinally at 5, 10, 20, and 50 weeks after the first dose, as well as when clinically required. Results: ADAs were detected in 4 of 67 cases (5.9%) on at least 2 occasions and were not necessarily associated to significant decreased emicizumab concentration, activated partial thromboplastin time prolongation or bleeding episodes. Only 1 of 4 ADA-positive patients required emicizumab discontinuation due to treatment failure. Conclusion: The present findings confirm that the development of anti-emicizumab antibodies is a rare event, particularly those with neutralizing activity. Routine monitoring should be reserved only for patients with clinical manifestations of bleeding when therapy failure is suspected.

Emicizumab is an antibody that mimics the function of factor (F)VIII and has been approved for prophylaxis in hemophilia A patients. However, the development of anti-drug antibodies (ADA) against emicizumab, although rare, can impair its efficacy. In cases with low drug levels or bleeding events, differentiating between ADA- and adherence-related issues can be challenging.We aimed at evaluating the effectiveness of a modified bridging ELISA (Valsecchi et al, JTH 2021) in detecting ADA in patients suspected of developing this response. Clinical and laboratory data were retrospectively collected from six patients with suspected ADA and one with a confirmed case. The modified ELISA was performed blindly to identify potential ADA presence. After a new ADA case was confirmed, it was characterized by assessing its expression over time and neutralizing effect.Five patients had emicizumab levels ≤1 µg/mL, while two had higher levels (13 and 15 µg/mL). Among the patients, two experienced spontaneous bleeding, and four had traumatic bleeding. ADA was detected in two patients, including the one with a known ADA. In ADA-negative patients, emicizumab levels increased following adjustments for compliance or administration issues. The newly identified ADA was neutralizing, blocking emicizumab's binding to factors IX and X. Its pattern of expression was similar to that of the known ADA case, peaking 3 months after the loss of emicizumab efficacy and remaining positive for over a year after emicizumab discontinuation.In bleeding patients with low emicizumab levels, the modified bridging ELISA may effectively differentiate ADA patients from those with other issues leading to decreased emicizumab concentration.

Emicizumab is approved for prophylaxis of patients with hemophilia A (HA). Despite its efficacy in reducing bleeding, some patients on emicizumab still experience hemarthrosis, but no tool is yet available to identify those at a higher risk of spontaneous joint bleeding. This study aimed to evaluate whether laboratory measurements (global coagulation assays and emicizumab concentration) and/or arthropathy scores can distinguish patients at higher risk of spontaneous joint bleeding while on emicizumab prophylaxis. A thrombin generation assay was performed upon the addition of tissue factor and synthetic phospholipids. Nonactivated thromboelastography was performed on citrated whole blood. Emicizumab concentrations were measured using a modified 1-stage factor VIII assay. The degree of hemophilic arthropathy was assessed using the Hemophilia Joint Health Score and Hemophilia Early Arthropathy Detection with Ultrasound (HEAD-US) score. A Cox proportional hazards model was used to evaluate the association between variables and bleeding. The predictive power of these variables was investigated using receiver operating characteristic (ROC) analysis. Forty patients with severe HA, with or without inhibitors, on emicizumab prophylaxis were enrolled in an observational cohort study. Ten of 40 developed spontaneous joint bleeding. None of the laboratory parameters were able to distinguish patients with a higher risk of spontaneous joint bleeding. ROC analysis showed that during emicizumab prophylaxis, only the presence of synovitis and a higher HEAD-US score were associated with spontaneous joint bleeding (area under the curve, 0.84). A greater degree of arthropathy and the presence of synovitis could help predict the risk of spontaneous joint bleeding in patients with HA on emicizumab prophylaxis.

Background The covalent link of polyethylene glycol (PEG) chains to recombinant factor VIII (FVIII) molecule is one of the most established approaches to produce novel therapeutic FVIII products with extended half-life (EHL). To date, three PEGyated-FVIII molecules, rurioctocog alfa pegol, turoctocog alfa pegol, and damoctocog alfa pegol are available for treatment of hemophilia A patients. From the pivotal clinical studies data, they showed comparable safety profile and pharmacokinetic with a mean half-live 1.3-1.7 times longer than the standard non-PEGylated FVIII. Although the PEG polymer is considered non immunogenic, antibodies against PEG, called pre-existing anti-PEG antibodies (APAs), have been reported in persons never treated with PEGylated drugs owing to PEG exposure during the activities of daily living. These antibodies can impact the clinical efficacy of PEGylated drug therapies by accelerating the blood clearance and changing pharmacokinetic. Recently, small amounts of PEG are also included in the lipid nanoparticles of the mRNA SARS-Cov-2 vaccines, BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna). Aim To describe a poor plasma FVIII recovery after the first infusion of a PEGylated FVIII product in two male patients with severe hemophilia A without inhibitor at about one month from the second dose of the BNT162b2 SARS-Cov-2 vaccination. Method About two months after the first dose of the SARS-Cov-2 vaccine and one month after the second, before switching from a standard half-life to a PEGylated FVIII product, patients underwent a PK study by infusion of 50 IU/kg of turoctocog alfa pegol (patient 1) or damoctocog alfa pegol (patient 2). FVIII activity was measured by Chromogenix Coamatic FVIII (Werfen) in plasma samples collected before and after the PEGylated FVIII infusion. Anti-PEGylated FVIII antibodies were searched by means of a home-made ELISA in plasma samples collected before administration of SARS-Cov-2 vaccine and at PK study. The assay was performed by using as capturing substrates each of the licensed PEGylated FVIII product (rurioctocog alfa pegol, turoctocog alfa pegol, and damoctocog alfa). Moreover, a non-PEGylated standard FVIII (Advate®) was employed as control substrate. Results FVIII coagulant activity measured after the infusion of 50 IU/kg of the PEGylated FVIII product showed a very low plasma recovery, 5% for patient 1 and 4% for patient 2. Anti-PEGylated FVIII antibodies reacting with each PEGylated FVIII products were found in plasma samples collected at PK baseline and after FVIII infusion but not in a sample obtained before the SARS-Cov-2 vaccination. No reactivity was found in vitro against the non-PEGylated standard FVIII product (figure). Conclusions Our finding of antibodies reacting with the PEGylated part of the FVIII molecule induced or boosted by BNT162b2 SARS-Cov-2 vaccination supports the view that the administration of the mRNA vaccine could impair plasma FVIII recovery after infusion of a PEGylated product. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Abstract Background Patients with severe hemophilia A may develop inhibitors against factor VIII (FVIII) in around 30% of cases. Recently, the introduction of non-replacement therapies such as emicizumab, a FVIII-mimicking agent administered as a subcutaneous injection, has revolutionized the treatment of patients with inhibitors. However, although rarely, some patients may develop antibodies against this drug. If neutralizing, these antibodies interfere with the activity of the drug, making it ineffective. Mim8 (Novo Nordisk®) is a novel experimental FVIII-mimetic human bispecific antibody that has a similar function as emicizumab, by bridging activated FIX (FIXa) and FX to activate FX, although with a different molecular structure compared to emicizumab. It is currently in phase II clinical trial for subcutaneous treatment of patients with hemophilia A with or without FVIII inhibitors (1, 2). It is currently unknown whether the antibodies developed against emicizumab by patients with hemophilia A could cross-react with Mim8. Aim Our aim was to study the cross-reactivity of anti-emicizumab antibodies developed by patients with hemophilia A against Mim8 with an in-house detection method. Methods We studied the serum of three patients who developed anti-emicizumab antibodies. Plasma from one patient with persistent inhibiting antibodies was collected both during the treatment (thus also containing emicizumab at steady-state levels) and two years after treatment discontinuation due to inefficacy (neutralizing persistent antibodies). Plasma from two patients who developed transient antibodies against emicizumab were also tested in the course of treatment with emicizumab (non-neutralizing transient antibodies). The plate was coated both with emicizumab and with Mim8 provided by the pharmaceutical companies for research purposes. Plasma samples, diluted 1/20, were loaded into the coated wells and incubated 90 min at 37°C. The cross-reactivity to Mim8 was evaluated also by using the affinity purified anti-emicizumab IgG, which was loaded at 5 ug/mL. A properly adapted ELISA method already described (3) was used as reference assay. Then, biotinylated-emicizumab (1.5 ug/mL) or biotinylated-Mim8 (at 2 and 4 ug/mL) were added and the plate incubated 1 hour at 37°C. Moreover, a competition test was performed by using a mixture of biotinylated-emicizumab (1.5 ug/mL) and an excess of Mim8 (at 4, 8 and 40 ug/mL) in the detection phase. Results The Mim8 molecule - either alone, or matched with emicizumab - used both in the capture phase and in the detection phase did not bind to neither patient's plasma antibodies nor to anti-emicizumab purified IgG, which were instead revealed with the reference assay. The binding of the anti-emicizumab antibodies to biotinylated-emicizumab was not inhibited by the addition of Mim8, even at 40 ug/mL. Conclusions Our in-house method showed that anti-emicizumab antibodies do not react with Mim8 in vitro. Observational studies to test whether Mim8 can be used safely in patients with anti-emicizumab antibodies are needed to confirm our findings in vivo as well. References 1. Østergaard et al. A FVIIIa-mimetic bispecific antibody (Mim8) ameliorates bleeding upon severe vascular challenge in hemophilia A mice. Blood. 2021;blood.2020010331. doi:10.1182/blood.2020010331. 2. Valsecchi C et al. J Thromb Haemost. 2021;19(3):711-718. Disclosures Peyvandi: Roche: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Sobi: Consultancy, Honoraria; Takeda: Consultancy, Honoraria.

HaemophiliaVolume 28, Issue 5 p. e141-e144 LETTER TO THE EDITOR Real-world data on emicizumab prophylaxis in the Milan cohort Sara Arcudi, Sara Arcudi orcid.org/0000-0001-5743-9098 Università degli Studi di Milano, Department of Pathophysiology and Transplantation, Milan, ItalySearch for more papers by this authorRoberta Gualtierotti, Roberta Gualtierotti Università degli Studi di Milano, Department of Pathophysiology and Transplantation, Milan, Italy Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorSonia Marino, Sonia Marino Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico di Milano, Department of Biomedical Surgical and Dental Sciences, Milan, ItalySearch for more papers by this authorGabriella Nicolò, Gabriella Nicolò Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico di Milano, Department of Healthcare Professions, Milan, ItalySearch for more papers by this authorEugenia Biguzzi, Eugenia Biguzzi Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorAlessandro Ciavarella, Alessandro Ciavarella Università degli Studi di Milano, Department of Biomedical Sciences for Health, Milan, ItalySearch for more papers by this authorMarco Boscarino, Marco Boscarino Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorSimona Maria Siboni, Simona Maria Siboni Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorLucia Schiavone, Lucia Schiavone Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorCristina Novembrino, Cristina Novembrino orcid.org/0000-0003-1450-9935 Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorCarla Valsecchi, Carla Valsecchi Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorFlora Peyvandi, Corresponding Author Flora Peyvandi flora.peyvandi@unimi.it orcid.org/0000-0001-7423-9864 Università degli Studi di Milano, Department of Pathophysiology and Transplantation, Milan, Italy Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, Italy Correspondence Flora Peyvandi, MD, PhD, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Via Pace 9, 20122 Milan, Italy. Email: flora.peyvandi@unimi.itSearch for more papers by this author Sara Arcudi, Sara Arcudi orcid.org/0000-0001-5743-9098 Università degli Studi di Milano, Department of Pathophysiology and Transplantation, Milan, ItalySearch for more papers by this authorRoberta Gualtierotti, Roberta Gualtierotti Università degli Studi di Milano, Department of Pathophysiology and Transplantation, Milan, Italy Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorSonia Marino, Sonia Marino Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico di Milano, Department of Biomedical Surgical and Dental Sciences, Milan, ItalySearch for more papers by this authorGabriella Nicolò, Gabriella Nicolò Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico di Milano, Department of Healthcare Professions, Milan, ItalySearch for more papers by this authorEugenia Biguzzi, Eugenia Biguzzi Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorAlessandro Ciavarella, Alessandro Ciavarella Università degli Studi di Milano, Department of Biomedical Sciences for Health, Milan, ItalySearch for more papers by this authorMarco Boscarino, Marco Boscarino Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorSimona Maria Siboni, Simona Maria Siboni Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorLucia Schiavone, Lucia Schiavone Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorCristina Novembrino, Cristina Novembrino orcid.org/0000-0003-1450-9935 Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorCarla Valsecchi, Carla Valsecchi Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, ItalySearch for more papers by this authorFlora Peyvandi, Corresponding Author Flora Peyvandi flora.peyvandi@unimi.it orcid.org/0000-0001-7423-9864 Università degli Studi di Milano, Department of Pathophysiology and Transplantation, Milan, Italy Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center and Fondazione Luigi Villa, Milan, Italy Correspondence Flora Peyvandi, MD, PhD, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Angelo Bianchi Bonomi Hemophilia and Thrombosis Center, Via Pace 9, 20122 Milan, Italy. Email: flora.peyvandi@unimi.itSearch for more papers by this author First published: 19 July 2022 https://doi.org/10.1111/hae.14630Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume28, Issue5September 2022Pages e141-e144 RelatedInformation

Increasing number of severe COVID 19 patients develop pulmonary Fibrosis, but the management of this complication is still unclear due to a lack of clinical trials. Aim of this study was to characterize mesenchymal cells (MC) isolated from 10 broncho-alveolar lavage (BAL, at 2 months after discharge) from patients with COVID19 fibrosis (COVID19-f) and to compare them with those isolated from 8 patients with collagen tissue disease-associated interstitial fibrosis(CTD-ILD). BAL fluid (BALf) levels of TGFbeta, VEGF, TIMP2, RANTES, IL6, IL8, and PAI1 were assessed by ELISA. Primary MC foci were cultured and expanded in D-MEM +10% FBS, characterized by flow cytometry and osteogenic and adipogenic differentiation. Collagen 1 production (+/−TGF-beta) was tested by WB and mRNA expression. BALf cytokine and GF levels were comparable in the two groups. Efficiency of MC isolation from BAL was 100% in COVID-f compared to 65% in CTD-ILD. MC antigen surface expression of CD105, CD73, CD90 (>90%, respectively), CD45, CD34, CD19 and HLA-DR (<5%, respectively) was comparable. None of MC samples differentiated in adipocytes, while COVID19-f were positive for calcium deposition. COVID19-f MC showed at WB, higher Collagen 1 production with respect to CTD-ILD with TGF-beta stimulation. Our preliminary data suggest MC from COVID19-f share several features with CTD-ILD but might have a higher response to fibrogenic and differentiation signals

Abstract Introduction Emicizumab is a recombinant, humanized, bispecific antibody restoring the function of missing activated factor VIII (FVIII) by bridging activated FIX (FIXa) and zymogen factor X (FX), medicating the activation of FX. Emicizumab is approved in several countries, at the doses of 1.5 mg/kg once weekly, 3 mg/kg every 2 weeks or 6 mg/kg every 4 weeks, for the prophylaxis of bleeding episodes in patients with hemophilia A with and without inhibitors. The drug has shown a good efficacy either during registration studies as well as in real-world experiences and was well tolerated without significant side effects. The development of neutralizing anti-emicizumab antibodies has been reported in very few cases which frequently required the switch to other products due to inefficacy of the prophylaxis. Patients maintaining a plasma concentration range of the drug within 30-80 ug/ml did not show significant bleeds. However, real life experiences bring the need of personalization of the drug dose. A recent case series presented at ISTH 2021 from Malaysian authors evaluated the efficacy of a dose of emicizumab between 1.7 and 1.9 mg/kg every 4 weeks, showing that even at a lower dose than that approved could be effective for the prevention of bleeding events. Here we report the case of an adult patient with moderate hemophilia A with inhibitor who developed an anti-emicizumab antibody which reduced the concentration of the drug by 50%. Despite that the patient did not report bleeding events in a follow-up period of 18 weeks. Treatment with emicizumab requires further evaluation to understand the best dose for the prevention of bleeding. Case report A 74 years old patient with moderate hemophilia A (FVIII 1-3%) followed at our Center had history of high-titer inhibitor (maximum titer 20 BU). The patient was treated on-demand with plasma-derived FVIII concentrates, when, in Jul 2000, he developed a neutralizing anti-FVIII antibody requiring treatment with activated prothrombin complex concentrates (Feiba). In Nov 2020 the patient was hospitalized for traumatic brain hemorrhage treated with plasma-derived FVIII (inhibitor titer < 5 BU) and subsequently, for the recurrence of inhibitor, with activated prothrombin complex concentrates. In Feb 2021 the patient started prophylaxis with emicizumab at the initial dose of 3 mg/kg once weekly (loading dose), followed by a maintenance dose of 1.5 mg/kg. The patient underwent periodic blood withdrawal for monitoring drug plasma concentration. In Apr 2021 (week 10) drug concentration showed a slight decrease from initial levels, from 39.1 ug/ml (week 5) to 28.3 (week 10) and a weak positivity for an anti-emicizumab antibody was detected. At the following test (week 15) positivity for the anti-emicizumab antibody was confirmed, witnessed by the consistent reduction in drug plasma concentration up to 20.9 ug/ml. During the following weeks, until week 22, drug plasma concentrations were stable (range 17.0-19.4 ug/ml) and positivity for anti-emicizumab antibody remained, as shown in the table. The results of partial Thromboplastin Time (PTT) were consistent with the drug plasma concentrations during the observation period, in which the patient did not developed any bleeding event. Conclusion This case report may corroborate the hypothesis of the efficacy of a reduced dose of emicizumab in patients with hemophilia A. Close laboratory monitoring in patients in prophylaxis with emicizumab is warranted for the evaluation of drug plasma concentration and the prompt detection of anti-drug antibodies, particularly if patient show a reduced therapeutic efficacy. However, in the absence of bleeding events, positivity for anti-emicizumab antibodies should not bring to sudden drug discontinuation. Indeed, in the view of the above, a lower drug plasma concentration than standard might be effective in the prevention of bleeding. 1. Tang ASO et al. July 2021. Efficacy of Reduced-dose Emicizumab in Haemophilia A with Inhibitors: Real World Experience in East Malaysia. ISTH 2021. Figure 1 Figure 1. Disclosures Peyvandi: Takeda: Consultancy, Honoraria; Sobi: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Roche: Consultancy, Honoraria.

BACKGROUND Inflammatory bowel diseases (IBD) are characterized by an increased thrombosis risk of uncertain etiology. Coagulation derangement arising from inflammation may be a triggering factor. We hypothesized that strong inflammation inhibitors (eg, anti-tumor necrosis factor-α drugs) may affect coagulation. METHODS Forty patients with IBD were compared with 57 control patients for coagulation factors and endogenous thrombin potential (ETP), the latter being the most sensitive marker of in vivo pro- and anticoagulation balance. We measured ETP in the presence and absence of thrombomodulin (the physiologic protein C [PC] activator). Coagulation at different timepoints was also assessed for 28 of these patients during infliximab treatment. RESULTS The median ETP (nM thrombin × minutes) and range (minimum-maximum) were each higher in patients at baseline than in control patients in both the absence (2120 [1611-3041] vs 1865 [1270-2337]) and the presence (1453 [464-2522] vs 831 [104-1741]) of thrombomodulin. The ETP ratio (with/without thrombomodulin) was high at baseline (0.73 [0.21-0.90] vs 0.45 [0.07-0.85]). The ETP and ETP ratio declined during treatment and were significantly lower at the end than at baseline. Factor (F) VIII and fibrinogen, which were high at baseline, decreased during treatment and at the end were significantly lower than at baseline. The FVIII/PC ratio, which was high in patients at baseline, declined during treatment and at the end was lower than at baseline. C-reactive protein recorded at the end of treatment was lower than at baseline. CONCLUSIONS Patients with IBD have a procoagulant imbalance as shown by increased ETP at baseline. The ETP decreases during treatment with infliximab, which is related to decreased FVIII and FVIII/PC ratio. This effect is also related to the improvement of inflammation as shown by decreased fibrinogen and C-reactive protein.

Background: The genetically engineered, humanized, bispecific monoclonal antibody emicizumab (Hemlibra) that mimics the cofactor activity of activated factor VIII (FVIII) has been approved for treatment of hemophilia A patients with and without inhibitor. In the pivotal premarketing clinical trials, emicizumab prophylaxis significantly reduced bleeding rates compared with previous treatments and was well tolerated. However, a consequence of this novel therapy may be the host immune response to a foreign protein. Objective: Characterization of the neutralizing anti-emicizumab antibody associated with the loss of treatment efficacy. Patient: A pediatric hemophilia A patient with inhibitor enrolled in the HAVEN2 (Study of Emicizumab Administered Subcutaneously (SC) in Pediatric Participants With Hemophilia A and Factor VIII (FVIII) Inhibitors) clinical trial. Methods: The anti-emicizumab antibody has been characterized with Western blot and enzyme-linked immunosorbent assay (ELISA). The antibody was affinity purified and sequenced. Binding affinity to full-length and papain-digested emicizumab was analyzed using surface plasmon resonance and byo-layer interferometry. Results: The neutralizing anti-emicizumab antibody was highly polyclonal with high-affinity binding mainly to the Fab portion of emicizumab with a small amount of binding to the Fc portion. Molecular interaction experiments between emicizumab and the purified antibody indicated the presence of at least two components with similar affinities. Conclusions: Although the incidence of neutralizing anti-emicizumab antibody is rare, this study highlights the importance of a close monitoring and the need of a simple laboratory assay to promptly detect these antibodies in patients with a history of poor drug efficacy.

Abstract INTRODUCTION: Emicizumab is a humanised bispecific monoclonal antibody, which replaces the function of factor VIII (FVIII) by bridging activated factor IX and factor X. Emicizumab is approved for prophylaxis of patients with Hemophilia A (HA), both with and without inhibitors. Real-world data on the efficacy and safety of emicizumab were recently reported from a few hemophilia treatment centers, but more data are needed to assess the efficacy and safety of emicizumab in comparison to standard prophylactic treatment. OBJECTIVE: To evaluate the safety and efficacy of emicizumab prophylaxis in a single cohort of patients with HA, with and without inhibitors. METHODS: We performed an observational prospective study including patients affected with HA, with and without inhibitors, switched to emicizumab prophylaxis in the post-marketing era. Data regarding inhibitor status, Annualized Bleeding Rate (ABR), cause of bleeding, type and location of bleeds, Emicizumab Plasmatic Concentration [Emi] and activated partial thromboplastin time (aPTT) were collected for each patient. Hemophilia Joint Health Scores (HJHS) and General Health Visual Analogue Scale (GH-VAS) were collected by trained physiotherapists before switching to emicizumab and 12 months after treatment start. RESULTS: A total of 22 patients, 21 with severe and 1 with moderate HA, were enrolled. Twenty patients were without inhibitor against FVIII and 2 adults with inhibitor were previously treated with bypassing agents. All patients started emicizumab prophylaxis with a loading dose of 3 mg/kg once weekly for 4 weeks, followed by a maintenance dosage of 1.5 mg/kg weekly. Within the children cohort, 3 were Previously Untreated Patients (PUPs) and 2 were previously treated with FVIII without developing inhibitor. The ABR showed a reduction of 74% in the entire cohort, as reported in Table 1. When stratifying for age groups, the ABR reduction was 70% for adults and 100% for children. Within the adults, the zero-bleeding patients increased from 2 to 11 patients (from 12 to 64%, respectively). In the adult cohort, 6 patients experienced 11 bleeding events over a mean follow-up of 300 days. Five out of 11 events were experienced in 6 months by a single patient who developed anti-drug antibodies (ADA) against emicizumab around the 5 th week ([Emi] 31.7 ug/ml). The prophylaxis with emicizumab was interrupted due to the treatment failure, which occurred despite spontaneous ADA clearance. Another patient developed ADA around the 9 th week ([Emi] 28.3 ug/ml), but without associated bleedings in up to 14 weeks of follow-up (minimum [Emi] 17 ug/ml). Of the remaining 5 adults who experienced bleedings during emicizumab prophylaxis, one patient developed spontaneous soft tissue bleeding, another one developed a spontaneous hemarthrosis in his target joint and the remaining 3 patients experienced post-traumatic joint bleedings, 2 out of 3 bleedings were in target joints. The analysis of the number of total joint bleedings before and after switching stratified for spontaneous and post-traumatic, revealed a reduction in target joint bleedings of 73% and a reduction of spontaneous and post-traumatic bleeding of 80% and 43%, respectively. All events were managed in outpatient clinic and required only a single infusion of FVIII concentrate. The plasmatic concentrations of emicizumab at steady state were within previous reported normal range for all patients, with exception of the two patients who developed ADA. Interestingly, steady state concentration was higher in children than in adults (median [Emi] 64.9 ug/ml and 49.85, respectively). The HJHS and GH-VAS scores at baseline and after 12 months of emicizumab prophylaxis available in 6 adults showed improvement in joint health and self-perceived global health, as shown in Figures 2 and 3. No thrombotic events were reported in the entire cohort. DISCUSSION: We report our Milan single center experience on the use of emicizumab prophylaxis in children and adults with HA, with and without inhibitors. Our experience shows a good efficacy of emicizumab both in children and adults, with few post-traumatic bleedings occurring mainly in target joints of adult patients. In addition, physician's and self-assessed scores revealed an improvement of patient's joint health after 12 months of emicizumab prophylaxis. Figure 1 Figure 1. Disclosures Peyvandi: Roche: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Sobi: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria.

BACKGROUND:There is a need to identify patients with haemophilia who have a very low or high risk of developing inhibitors. These patients could be candidates for personalized treatment strategies.AIMS:The aim of this study was to externally validate a previously published prediction model for inhibitor development and to develop a new prediction model that incorporates novel predictors.METHODS:The population consisted of 251 previously untreated or minimally treated patients with severe haemophilia A enrolled in the SIPPET study. The outcome was inhibitor formation. Model discrimination was measured using the C-statistic, and model calibration was assessed with a calibration plot. The new model was internally validated using bootstrap resampling.RESULTS:Firstly, the previously published prediction model was validated. It consisted of three variables: family history of inhibitor development, F8 gene mutation and intensity of first treatment with factor VIII (FVIII). The C-statistic was 0.53 (95% CI: 0.46-0.60), and calibration was limited. Furthermore, a new prediction model was developed that consisted of four predictors: F8 gene mutation, intensity of first treatment with FVIII, the presence of factor VIII non-neutralizing antibodies before treatment initiation and lastly FVIII product type (recombinant vs. plasma-derived). The C-statistic was 0.66 (95 CI: 0.57-0.75), and calibration was moderate. Using a model cut-off point of 10%, positive- and negative predictive values were 0.22 and 0.95, respectively.CONCLUSION:Performance of all prediction models was limited. However, the new model with all predictors may be useful for identifying a small number of patients with a low risk of inhibitor formation.

We investigated longitudinally the behaviour of anti-factor VIII (anti-FVIII) IgG subclasses for 6 months from inhibitor development in 43 patients from the Survey of Inhibitors in Plasma-Products Exposed Toddlers (SIPPET) trial who developed persistent or transient inhibitors. We first analysed 43 patients within 60 days post inhibitor detection. Then, 14 of these 43 patients were studied at five time points over 6 months. Our study showed that during the first 60 days, the risk of inhibitor persistence increased with the concomitant presence of an increasing number of IgG subclasses. Over the 6-month period post inhibitor detection, only the IgG2 subclass could be considered a hallmark of inhibitor persistence.

Introduction: Hemostasis has been postulated as a mechanism of liver damage in cirrhosis. Low ADAMTS13/Von Willebrand Factor antigen (VWF:Ag) and high factor VIII/protein C ratio (FVIII/PC) mark platelet hyperaggregation (primary hemostasis) and hypercoagulation (secondary hemostasis), respectively. Aim: To explore the association of such parameters with the severity of the liver disease measured by Child-Pugh, MELD, MELD-Na and their prognostic role on clinical outcome.