Rare Occurrence of Inhibitors in Von Willebrand Disease: A Case Report

Introduction: Type 3 Von Willebrand Disease (VWD) is the least common but the most severe form of a disease, with a prevalence of about 0. 5 to 1 per million in Western countries. The prevalence of type 3 VWD in the developing countries, with a high degree of consanguinity, is about 6 per million. Moreover, due to underdiagnosis of the milder cases, the prevalence of type 3 VWD is about 50% of the cases. Rarely, some patients develop the Von Willebrand Factor (VWF) inhibitors, which may subsequently develop severe anaphylactic reactions on further exposure to the VWF containing factor replacement therapy. The prevalence of inhibitor development in patients with type 3 VWD has been shown to be in the range of 5.8 to 9.5%. In the absence of a gold standard assay for the quantitation of VWF inhibitors, a correct diagnosis and management of these patients are often challenging.Objectives: The objective of this study is to standardize the Bethesda assay for the VWF inhibitors and to estimate the VWD inhibitor titer in two cases of congenital type 3 VWD, which developed the VWF inhibitors.Results and Conclusions: We could successfully standardize the Bethesda assay for the quantitation of VWF inhibitors in two patients with congenital type 3 VWD with inhibitors.

Efficacy of rFVIIIFc for First-Time Immune Tolerance Induction (ITI) Therapy: Final Results from the Global, Prospective VerITI-8 Study

Introduction: Inhibitor development is a major complication of factor VIII (FVIII) replacement therapy, affecting approximately 30% of people with severe hemophilia A (Peyvandi et al Lancet 2016). Inhibitor eradication is the standard of care to restore responsiveness to FVIII; however, ITI regimens often require frequent high-dose factor injections over a long period (DiMichele et al Haemophilia 2007; Carcao et al Haemophilia 2021). Median (interquartile range [IQR]) time (months) to negative titer in the International ITI Study with high-dose FVIII was 4.6 (2.8-13.8) (n=31); negative titer to normal recovery was 6.9 (3.5-12.0) (n=23); and normal recovery to tolerance was 10.6 (6.3-20.5) (n=22) (Hay and DiMichele Blood 2012). Recombinant factor VIII Fc fusion protein (rFVIIIFc) is an extended half-life (EHL) FVIII that showed potential benefits for ITI in retrospective clinical data and case reports (Malec et al Haemophilia 2016; Groomes et al Pediatr Blood Cancer 2016; Carcao et al Haemophilia 2021). VerITI-8 (NCT03093480) is the first prospective study of rFVIIIFc in first-time ITI and follows on from the reITIrate (NCT03103542) study of rFVIIIFc for rescue ITI (Königs et al Res Pract Thromb Haemost, ISTH 2021). Aim: Describe outcomes in the verITI-8 study of first-time ITI with rFVIIIFc over 48 weeks in subjects with severe hemophilia A and high-titer inhibitors. Methods: VerITI-8 is a prospective, single-arm, open-label, multicenter study exploring efficacy of rFVIIIFc for first-time ITI in people with severe hemophilia A with high-titer inhibitors. Initial screening was followed by an ITI period in which all subjects received rFVIIIFc 200 IU/kg/day until tolerization or 48 weeks had elapsed (Figure). This was followed by tapered dose reduction to standard prophylaxis and follow-up. Key inclusion criteria included males with severe hemophilia A, high-titer inhibitors (historical peak ≥5 Bethesda units [BU]/mL), and prior treatment with any plasma-derived or recombinant standard half-life or EHL FVIII. Key exclusion criteria included coagulation disorder(s) other than hemophilia A and previous ITI. The primary endpoint was time to tolerization (successful ITI) with rFVIIIFc defined by inhibitor titer <0.6 BU/mL, incremental recovery (IR) ≥66% of expected IR (IR ≥1.32 IU/dL per IU/kg) (both at 2 consecutive visits), and t ½ ≥7 hours (h) within 48 weeks. Secondary endpoints included number of subjects achieving ITI success, annualized bleed rates (ABR), and adverse events (AEs). Results: Sixteen subjects were enrolled and received ≥1 rFVIIIFc dose. Median (range) age at baseline was 2.1 (0.8-16.0) years, and historical peak inhibitor titer was 22.4 (6.2-256.0) BU/mL (Table). Twelve (75%), 11 (69%), and 10 (63%) subjects, respectively, achieved a negative inhibitor titer, an IR >66%, and a t½ ≥7 h (ie, tolerance) within 48 weeks. Median (IQR) times in weeks to achieve these markers of success were 7.4 (2.2-17.8), 6.8 (5.4-22.4), and 11.7 (9.8-26.2) (ie, 2.7 [2.3-6.0] months to tolerance), respectively. One subject achieved partial success (negative inhibitor titer and IR ≥66%), and 5 subjects failed ITI, of which 2 had high inhibitors throughout, 2 experienced an increase in inhibitor levels, and 1 recorded a negative inhibitor titer at 282 days. Most bleeds occurred in the ITI period when median (IQR) ABRs (n=13) were 3.8 (0-10.1) overall, 0 (0-2.6) for spontaneous, 1 (0-4) for traumatic, and 0 (0-3.1) for joint. During tapering, median (IQR) ABRs (n=10) were overall, 0 (0-2.4); spontaneous, 0 (0-0); traumatic, 0 (0-1.3); and joint, 0 (0-0). All 16 subjects experienced ≥1 treatment-emergent AE (TEAE), the most frequent of which was pyrexia in 7 subjects (44%). One subject reported ≥1 related TEAE (injection site pain). Nine subjects (56%) experienced ≥1 treatment-emergent serious AE (TESAE). TESAEs occurring in ≥2 subjects included vascular device infection, contusion, and hemarthrosis. No treatment-related TESAEs, discontinuations due to AEs, or deaths were reported. Conclusions: rFVIIIFc is the first EHL FVIII with prospective data for first-time ITI in patients with severe hemophilia A with historical high-titer inhibitors. Evaluated within a 48-week timeframe, rFVIIIFc offered rapid time to tolerization (median 11.7 weeks; 2.7 months) with durable responses in almost two-thirds of subjects and was well tolerated. Optimizing ITI to eradicate inhibitors remains a priority. Figure 1 Figure 1. Disclosures Malec: CSL Behring: Consultancy; Genentech: Consultancy; HEMA Biologics: Consultancy; Pfizer: Consultancy; Sanofi: Consultancy, Research Funding; Takeda: Consultancy; Bioverativ: Consultancy, Research Funding, Speakers Bureau; Shire: Consultancy; Bayer: Consultancy. Van Damme: Pfizer: Consultancy; Shire: Consultancy; Bayer: Consultancy. Chan: Bioverativ: Consultancy. Jain: Sanofi: Ended employment in the past 24 months; Takeda: Current Employment, Current holder of stock options in a privately-held company. Sensinger: Sanofi: Current Employment, Current holder of stock options in a privately-held company. Dumont: Sanofi: Current Employment, Current holder of stock options in a privately-held company. Lethagen: Sobi: Current Employment, Current holder of stock options in a privately-held company. Carcao: Bayer, Bioverativ/Sanofi, CSL Behring, Novo Nordisk, Octapharma, Pfizer, Roche, and Shire/Takeda: Research Funding; Bayer, Bioverativ/Sanofi, CSL Behring, Grifols, LFB, Novo Nordisk, Pfizer, Roche, and Shire/Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. Peyvandi: Roche: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Sobi: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Ablynx, Grifols, Kedrion, Novo Nordisk, Roche, Shire, and Sobi: Other: Personal Fees. OffLabel Disclosure: adheres to routine clinical practice

Diagnosis and Treatment of Acquired Hemophilia: One Single-Center Experience from PR. China

Objective: To deepen the understanding of the clinical manifestations of acquired hemophilia A for timely and correctly treatment. Methods: The clinical data of the acquired hemophilia A patients diagnosed in the hospital from Jan 2006 to Mar 2021 were retrospectively analyzed, and the relevant literature was reviewed. Results: 17 patients with acquired hemophilia A, male: female =10: 7, median age 61 years (19 to 78 years), were diagnosed and treated in the hospital with the median time from the onset to diagnosis 21 days (2 days to 6 months). Six patients had comorbidity, including hepatitis B carrying, chronic myelomonocytic leukemia, diabetes, hypertension and positive autoantibodies, pemphigoid and gastric cancer, respectively. Other 11 patients were healthy before the onset. All patients had large large ecchymosis of skin, and one case was combined with hematuria, and one case with retroperitoneal hematoma. All patients had APTT extension (45s-144.7s) and the prolonged APTT could not be corrected with normal mixed plasma with and without incubation at 37℃ for 2 hours. FVIII activity was 1% - 8.9% and inhibitor titer 2 - 128 Bu/ml. All patients with bleeding were with prothrombin complex/recombinant activated coagulation factor VII, some of them with pd-coagulation factor FVIII preparations. Inhibitors were removed with prednisone acetate (1 case) + chemotherapy (1 case), prednisone acetate / + CTX (11 cases) + chemotherapy (1 case), prednisone acetate/prednisolone + mabthera (2 cases) + CTX (1 case), respectively. The removal time of inhibitor was from 8 days to 4 years. During the treatment process, two patients developed lower extremity venous thrombosis, and one patient was complicated with lung infection. Conclusion: Patients with unexplained bleeding and prolonged APTT should be conducted normal mixed plasma correction test, coagulation factor activity and inhibitor titer examination. After correctly diagnosis, bypass agents /coagulation factor VIII preparations should be given timely for hemostasis, protocol based on glucocorticoid + CTX/mabthera to remove the inhibitor and symptomatic treatment for patients with primary comorbidity disease at the same time. Disclosures No relevant conflicts of interest to declare.

ADAMS-TS13 Inhibitor Level and Risk of Relapse in Acquired Idiopathic Thrombotic Thrombocytopenic Purpura

Introduction: Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy due to reduced activity of ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type 1 motif, 13). This disorder can be due to a congenital deficiency state or be acquired (immune TTP (iTTP)) due to an antibody which either inhibits or causes clearance of ADAMTS13. The aim of our study was to determine whether ADAMTS13 inhibitor titer at initial presentation could serve as a predictor of refractory disease and relapse in iTTP. We also measured clinical outcomes across different gender and racial subgroups. Methods: The United States Thrombotic Microangiopathy (USTMA) iTTP registry was used to extract patient information for two academic institutions in Eastern North Carolina. Descriptive statistics were used to analyze the data. The first iTTP episode recorded in the data base was used as the index episode. All patients included in the final analysis had an ADAMTS13 activity of <10%. An inhibitor level of 5 Bethesda units was arbitrarily chosen as the cutoff between low (<5) and high (>/5) inhibitor level. Response time was defined as the number of days of plasma exchange (PEX) required to achieve a platelet count of 150,000 for two consecutive days. Relapse was defined as occurrence of a new episode of iTTP 30 days after achievement of response. Refractory disease was defined as persistence of thrombocytopenia or absence of a sustained platelet count increment or platelet counts of < 50,000 despite 4-7 days of plasma exchanges and steroid treatment. Rituximab resistance was defined as lack of platelet recovery to more than 150,000 within 11 to 14 days of administration of the first dose of Rituximab. Results: A total of 161 patients with iTTP were identified. Ten patients had ADAMTS13 activity >10% and 15 patients did not have a reported inhibitor level. These subjects were not included in the final analysis. The cohort had 28% male (n =38/136) and 72% (n=98/136) female patients. There were more African American patients 73% (n=99/136) than Caucasians 24% (n=32/136). There were also 2 Hispanic, 1 Native American and 2 patients with unidentified race. Median ADAMTS3 inhibitor titer was 1.05 (Range 0-87). Forty three patients with ADAMTS13 activity <10 % had an inhibitor level of 0 (i.e undetectable).They were included in the low inhibitor group. Overall, 88% patients (n=120/136) had low inhibitor level and only 12% (n=16/136) had a high inhibitor. Thirteen percent females (n=13/98) and 8% (n=3/38) males had a high inhibitor level (p=0.387). Fourteen percent (n=14/99) African Americans and 6 % (n=2/32) Caucasians had a high inhibitor, p=0.23. In the low inhibitor group 30% (n=36/120) patients suffered at least one episode of relapse whereas 31% (n=5/16) had relapsed in the high inhibitor group. The median time to response was 6 days (range 1-76) in the low inhibitor group and 7 days (range 4-20) in the high inhibitor group (p=0.61). While looking at the various subgroups, median time to response for males was 6 days (range 4-21), females 6 days (range 1-76) , African Americans 6 days (range 3-29) , and Caucasians 6 days (range 1-76). The frequency of refractory disease was 31 % (n=5/16) in the high inhibitor group and 29% (n=34/119) in the low inhibitor group. At the time of enrollment in the registry, Rituximab was not a part of first line therapy. Only 26 out of 136 patients had received Rituximab. In the low inhibitor group 5 patients displayed Rituximab resistance whereas there were no patients in the high inhibitor group with Rituximab resistance. Conclusion: When evaluating patients presenting with iTTP in two centers in North Carolina, no correlation was found between a high inhibitor levels of >/ 5 Bethesda units and risk of relapse or refractory disease. A larger study is needed to evaluate this further. Disclosures No relevant conflicts of interest to declare.

Rituximab Monotherapy Is Effective for Inhibitor Eradication with Concomitant Porcine Factor VIII Followed By Emicizumab for Bleed Control in Acquired Hemophilia a

Introduction Acquired hemophilia A (AHA) is a rare bleeding disorder in which acquired auto-antibodies to endogenous Factor VIII (FVIII) resulting in decreased FVIII activity. AHA can lead to life-threatening bleeding, with effective treatment requiring both immunosuppressive therapy (IST) and bypassing agents such as recombinant activated Factor VII (rFVIIa) or activated prothrombin complex concentrates (APCC) (Tiede et al. Haematologica 2020). Some, including our group, have begun using emicizumab as well (Knoebl et al. Blood 2020). IST is required for inhibitor eradication, but regimens are heterogenous and have not been systematically compared in the literature. While there is no standard of care IST in these patients, most patients in the literature receive multiple agents, including corticosteroids, mycophenolate mofetil, cyclosporine, and/or rituximab in combination. We report in a prospective cohort that for IST, rituximab monotherapy is an effective strategy. An updated treatment algorithm is offered that has been effective for treatment of these patients at our institution, which adds emicizumab therapy after initial bleed control. Methods We analyzed clinical, pharmacy, and laboratory data from 24 patients treated with rpFVIII at the University of North Carolina for AHA from July 2015 to June 2021. All patients were initially treated according to our previously established dosing algorithm with recombinant porcine FVIII, and the last five patients have received emicizumab after initial factor dosing (see Figure 1). 17 of the patients who received rituximab and were followed at our center subsequently attained inhibitor eradication, six of those received only rituximab therapy. Investigational review board approval was obtained for our data collection and analysis. Patients who did not receive rituximab, failed to reach an inhibitor level <0.5 BU, or who were lost to follow up were excluded from the analysis. For patients that fit the inclusion criteria, the time between date of the first rituximab infusion and the date of inhibitor eradication was calculated. Results All patients in our cohort who we followed until inhibitor eradication (17 of 24 patients) had eradication of inhibitors after a median of 143 days from initiation of immunosuppression. For patients treated with rituximab monotherapy for inhibitor eradication (6 of 17), this goal was reached in a median of 134.5 days (range 76-191 days). For those who received agents in addition to rituximab and have reached inhibitor eradication to date (9 of 17 patients), median days from initiation of immunosuppression to inhibitor eradication was 137.5 days (range 11-485) (P = 0.43 on Mann-Whitney test). Patients were treated as previously reported by our group per an algorithm that starts recombinant porcine FVIII without waiting for a porcine inhibitor and at lower than FDA recommended dosing. Subsequent doses for bleed control are titrated according to one-stage, clot based FVIII activity. This report also includes 5 new patients who, after initial bleed control per our algorithm, were initiated on emicizumab while awaiting inhibitor eradication. There was no correlation between time to rituximab initiation and time to inhibitor eradication in both those who received rituximab monotherapy and those who had multiple IST agents. There was also no significant difference in initial inhibitor titer between groups with median initial inhibitor titer of 104 BU in the rituximab monotherapy group, and 70 BU in the multiple IST agents group (see Figure 3). Conclusions Rituximab monotherapy appears to be an effective strategy for inhibitor eradication in acquired hemophilia A. In the context of bleed treatment with porcine factor, followed by emicizumab, a standardized, algorithmic approach can be effectively employed for these patients. Though any patients have inhibitor recurrence, as is described in the literature, with emicizumab available, bleeding can be avoided with regular monitoring. Emicizumab given while re-eradicating an inhibitor can prevent morbidity of this disease. Figure 1 Figure 1. Disclosures Ellsworth: Takeda: Other: Salary supported as part of NHF-Takeda Clinical Fellowship Award. Key: Uniqure: Consultancy, Other: Participation as a clinical trial investigator; Grifols: Research Funding; Takeda: Research Funding; BioMarin: Honoraria, Other: Participation as a clinical trial investigator; Sanofi: Consultancy. Ma: Accordant: Consultancy; Takeda: Honoraria, Research Funding. OffLabel Disclosure: Emicizumab is not approved for use in Acquired Hemophilia A and this represents an OFF LABEL use of the drug.

Inhibitor Index in the Clot Waveform Analysis-Based Mixing Test Differentiates among Hemophilia A without and with Inhibitors, and Lupus Anticoagulant

Background The mixing test is used to identify the pathway to follow-up testing and is also useful for the investigation of lupus anticoagulant (LA) positivity. “To completely correct” indicates clotting factor deficiency, while “to not correct” indicates the presence of a clotting factor inhibitor including LA. “Index of circulation anticoagulant” and/or “percent correction” is used to interpret the results of mixing studies, but it does not accurately differentiate factor inhibitors from LA. Aim To precisely differentiate hemophilia A (HA), HA with inhibitor (HA-inh), and LA using the clot waveform analysis (CWA)-based mixing test. Methods Plasma samples from HA, LA, and HA-inh including acquired HA were incubated with normal plasma in 9:1, 1:1, and 1:9 mix ratios. From activated partial thromboplastin time CWA at 0-minute (immediately) and 12-minute incubation, the ratios of CWA parameters at 12 minutes/0 minute (inhibitor index) were assessed. Results The inhibitor index values of CWA parameters obtained using the mixing test in a 1:1 ratio demonstrated a significant difference between HA-inh and LA but could not differentiate LA from HA-inh completely. Plasmas used for the mixing tests in 9:1 and 1:9 ratios were able to fully distinguish between HA-inh (>0.5 BU/mL) and LA. These indices significantly correlated with inhibitor titer below 40 BU/mL (r > 0.90), possibly estimating FVIII inhibitor titer from the inhibitor index. Plasmas in HA and LA could be distinguished by mixing in a 1:1 ratio at 0 minute (immediately). Conclusion The inhibitor index from CWA-based mixing tests with a 12-minute incubation could differentiate among HA, HA-inh, and LA quickly.

Thromboelastography in pre-surgery monitoring in Hemophilia A with high inhibitor titer: case report and literature review

The development of factor VIII inhibitors (allo-antibodies) continues to be a major complication in the management of severe forms of hemophilia A, especially as far as treatment and treatment response monitoring is concerned. The need to implement a reliable laboratory assay is all the more obvious if major surgery occurs, when conventional tests (activated partial thromboplastin time APTT, prothrombin time PT, factor VIII level) are of no avail and there is a very fragile balance between bleeding and thrombosis.We report the case of a 32 year-old patient diagnosed with severe Hemophilia A, referred to the Comprehensive Center for the Diagnosis and Treatment of Hemophilia of the Fundeni Clinical Institute for a multidisciplinary assessment in view of a total left hip arthroplasty due to aseptic necrosis of the femoral neck.Workup showed a high inhibitor titer (>200 BU). Taking into consideration the interindividual variability of the response to bypassing agents, as well as the bleeding risk associated with a major orthopedic surgery, we used thromboelastography (TEG) to assess the patient’s response to aPCC (activated prothrombin complex concentrate) and rFVIIa (activated recombinant factor VII). The findings helped select the optimal replacement scheme to ensure perioperative hemostasis.

Low-Dose Immune Tolerance Induction for Hemophilia a Children with Poor-Risk High-Titer Inhibitors

Background: Low-dose immune tolerance induction (ITI) +/- immunosuppression as a practical ITI strategy in China showed a relatively satisfactory success rate and economic advantages in pilot study. However, the outcome still needs to be verified by larger cohort. Aim: To report the efficacy of this low-dose ITI +/- immunosuppression strategy in hemophilia A children ≥ 10 BU. Methods: This was a single center, prospective study in 53 hemophilia A subjects from Sep 2016 to Apr 2019. All subjects having ≥ 10 BU receiving ~50IU/kg FVIII every other day using domestic intermediate purity pdFVIII/VWF products, either alone or in combination with rituximab and prednisone judging by inhibitors and ITI response. Results: Finally, 46 subjects received this strategy at a median of 3.2 (IQR, 2.3-6.5) years old, their pre-ITI inhibitor titer was median 30.0 (range, 10.1-416) BU. Analysis at median 15.1 (range 3.0-34.4) months follow-up, success (inhibitor <0.6BU) was achieved in 32 (69.6%) subjects, partial success (inhibitor <5BU but >0.6BU) in 11 (23.9%) subjects, and failure in 5 (10.9%) subjects. Between subjects administered ITI-alone and ITI- immunosuppression, no significant difference was observed in time to success (median 8.5; IQR 6.7-11.7 vs 10.2; IQR 5.1-25.1, P=0.164). The mean monthly bleeding rate on ITI was 0.49 which declined 59.3% compared with pre-ITI period. Subjects administered ITI-immunosuppression (0.54 ± 0.46) was higher than ITI-alone (0.42 ± 0.69) although with no significantly difference (P=0.089). Seven (21.9%) subjects experienced inhibitor recurrence, 4 subjects treated with ITI-alone, 3 with ITI-immunosuppression. Recurrence occurred at a median of 4.8 (range, 2.8-10.8) months after successful ITI with inhibitor titer transiently rising to median 0.7 (range, 0.7-1.5) BU. Conclusion: This low-dose ITI +/- immunosuppression therapy in subjects with pre-ITI inhibitor ≥ 10 BU showed a success rate similar to other high/intermediate-dose regimen for the whole inhibitor patients. The subjects treated with ITI-immunosuppression did not showed higher recurrence at present, while a longer time follow-up is still needed. Disclosures Poon: Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bioverativ/Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees; World Federation of Hemophilia: Other: Not-for-profit organization affiliation: volunteer ; Novo Nordisk: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Participation in sponsored research; CSL-Behring: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Grant Funding; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Grant Funding; Takeda/Shire: Consultancy, Membership on an entity's Board of Directors or advisory committees; Octapharma: Consultancy, Membership on an entity's Board of Directors or advisory committees.