Background: Severe hemophilia A (HA) negatively impacts health-related quality of life (HRQOL). Objectives: We aimed to analyze HRQOL in adult men with severe HA without inhibitors after valoctocogene roxaparvovec gene transfer in the phase 3 trial GENEr8-1. Methods: Participant-reported outcomes were the hemophilia-specific quality of life questionnaire for adults (Haemo-QOL-A), the EQ-5D-5L instrument, the Hemophilia Activities List (HAL), and the Work Productivity and Activity Impairment Questionnaire: Hemophilia Specific (WPAI+CIQ:HS). Participants completed the questionnaires at baseline and through 104 weeks postinfusion with 6 x 1013 vg/kg of valoctocogene roxaparvovec. Scores were analyzed per participant characteristics and outcomes. Results: For 132 HIV-negative participants, mean change from baseline in Haemo-QOLA Total Score met the anchor-based clinically important difference (CID: 5.5) by week 12; the mean (SD) increase was 7.0 (12.6) at week 104. At week 104, improvement in Consequences of Bleeding, Treatment Concern, Worry, and Role Functioning domain scores exceeded the CID (6). EQ-5D-5L Utility Index scores improved above the CID at week 52, but not at week 104. EQ-5D-5L visual analog scale and HAL scores increased from baseline to week 104. Participants reported less activity and work impairment at week 104 than baseline. Participants with problem joints had lower mean baseline HaemoQOL-A Total and domain scores than those without them, but improved over 104 weeks, except for 11 participants with >= 3 problem joints. Participants with 0 bleeds during the baseline prophylaxis period reported Haemo-QOL-A score improvements above the CID, including in the Consequences of Bleeding domain. Conclusion: Valoctocogene roxaparvovec provided clinically meaningful HRQOL improvement for men with severe HA.

Inborn errors of immunity (IEI) may present with immune dysregulation due to a variety of impairments in tolerance mechanisms. Several lymphocyte subsets have been proposed as biomarkers for immune dysregulation, but their importance in pathomechanisms and monitoring disease activity is unclear. Patients with IEI linked to immune dysregulation were enrolled through referrals and/or from our Jeffrey Modell Foundation registry (over 850 cases [2016 to 2022]). Peripheral blood samples were tested by flow cytometry for biomarkers of immune dysregulation including TCRab CD4-CD8- (DN), T follicular helper (Tfh), regulatory T (Treg) and CD19hiCD21lo B cell subsets. Forty-one IEI patients were identified with ALPS (n=4) or variants in CTLA4 (n=16), NFKB1 (n=9), PI3K (n=8), RAG (n=1) and 22q11del (n=3). Extensive immune phenotyping was available for 78 timepoints from 31 of 41 patients. Compared to healthy donors, expansion was noted in Tfh (52 timepoint; 26 patients), CD19hiCD21lo B (36 timepoints; 21 patients) and DN (32 timepoints; 19 patients) cell populations. A reduction in Treg compartment was observed (42 timepoints; 23 patients). The relative contribution of the four biomarker subsets in specific disorders were variable. Notable was the dual expansion of Tfh and CD19hiCD21lo B cells in patients with NFKB1 variant, whereas DN T cells correlated with Tfh expansion only in CTLA4 deficient patients. Our study investigates the utility of cellular biomarkers of immune dysregulation. Recognition of specific subsets of immune dysregulation may help monitor disease activity and individualize treatment strategies in IEI.

Introduction: Autoimmune cytopenias (AICs) occur in the setting of immune dysregulation and autoimmunity. AICs are known to precede the classical presentation and subsequent diagnosis of primary immunodeficiency disorders (PIDs) in some cases, with a PID spectrum involving B, T, and Treg dysregulation. Conversely, PID patients are also at a markedly increased risk of AICs and patients co-diagnosed with AICs and PIDs face higher mortality rates likely due to delayed diagnosis or improper/delayed therapy. Further, co-diagnosed patients are often refractory to standard treatment. Early screening and diagnosis of PIDs in the setting of AICs could lead to more targeted therapies and potentially better patient outcomes. We intend to investigate biomarkers that differentiate immune dysregulation among those with or without PID in the setting of AIC. Methods: A retrospective analysis comparing clinical history, including symptoms, presence of PID, genetic testing and diagnosis and treatment outcomes was performed on AIC patients in our hospital from 2016 to 2019. We also performed extensive immune phenotyping by flow cytometric analysis. Patients with expansion of CD19hi CD21lo B cells were further evaluated for Tbet+ CD11chi features for potential autoreactivity. Results: Our original cohort of 103 AIC patients included patients who were diagnosed with AIC only (n=52) or co-diagnosed with AIC-PID (n=51). From this cohort, a total of 43 were evaluated for further immune phenotyping, including 35 AIC-PID patients and 8 AIC only patients. Of the AIC-PID patients, 23 (65.7%) had a genetically coded PID, including pathogenic variants in CTLA4, NFKB1, PI3K or partial DiGeorge, while 12 (34.3%) were diagnosed with CVID/CID. Flow cytometry analysis revealed significantly increased T-follicular helper cell (Tfh) population in the AIC-PID group compared to AIC only (p=0.03) and healthy donor (HD) (p=0.004). We saw a similar expansion of CD19hi CD21lo B cells within the AIC-PID group. Conversely, patients with AIC-PID had decreased percentage of T-regulatory cells (Tregs) when compared to AIC only and HD groups. These differences were amplified within the genetically coded AIC-PID patients in Treg and Tfh populations and maintained in CD19hi CD21lo B cells. Further investigation of clinical history within the symptomatic, genetically coded AIC-PID group yielded 3 (33.3%) patients responsive to treatment and 6 (66.7%) patients unresponsive or partially responsive to therapy. Interestingly, nonresponsive patients showed an increased percentage of CD19hi CD21lo B cells. Conclusions: Our analysis demonstrates the potential utility of biomarkers, notably CD19hi CD21lo B cells and their immunological function for detecting underlying PIDs within the setting of AIC patients. Though this B cell population needs further assessment regarding Tbet and CD11c expression, with studies ongoing, these biomarkers may lead to a screening methodology to increase clinical visibility and detection as well as hasten diagnosis of underlying PID and potentially predict response to therapy, therefore increasing effective treatment outcomes for patients co-diagnosed with AIC PID.

Introduction: Among the most challenging complications of hemophilia A is inhibitor formation. A T-cell dependent B-cell response to exogenous factor VIII (FVIII), inhibitors result in a high burden of disease, with poorly controlled bleeding, twice the hospitalizations, 10-fold the cost, and 3.5-fold the mortality of non-inhibitor patients. Thus, a major goal of hemophilia management is to prevent and eradicate inhibitors. With the availability of novel therapies, including eloctate, a recombinant Fc-fusion protein (rFVIII-Fc) which induces regulatory T cells to promote FVIII tolerance, and emicizumab, a bispecific monoclonal FVIII mimetic, we designed the INHIBIT Clinical Trials Platform (X01HL143024), Fig.1. The platform is composed of two linked randomized phase III trials, the Inhibitor Prevention Trial (NCT04303559), comparing rFVIII-Fc vs emicizumab prophylaxis to prevent inhibitors, and the Inhibitor Eradication Trial (NCT04303572), comparing rFVIII-Fc immune tolerance induction (ITI) plus emicizumab vs rFVIII-Fc ITI alone to eradicate inhibitors. The platform uses adaptive design to incorporate historical data (Bayesian priors) on inhibitor formation to increase power and promote efficient use of rare data. Yet, there is equipoise regarding the optimal approach to inhibitor prevention and eradication, and, as clinical practice is changing, we aimed to test the feasibility of the INHIBIT trial design. Methods: To establish design feasibility, we conducted interviews with 30 hemophilia treatment center (HTC) physicians participating in the INHIBIT trials, to determine prophylaxis and tolerance regimens they prescribe and perceived barriers to the INHIBIT trials design. A 4-question survey was subsequently emailed to these physicians to ascertain the initial prophylaxis regimens they prescribe in previously untreated patients (PUPs) with severe hemophilia A, and the initial immune tolerance induction (ITI) they prescribe in high-responding inhibitor patients with severe hemophilia A; if new inhibitors had been observed during emicizumab prophylaxis, and willingness to participate in post-trial surveillance. Results: In interviews, HTC physicians indicated the issues that influenced choice of prophylaxis/ ITI regimen were patient preference, family history of inhibitors, infusion frequency, IV access, port requirement, and family fatigue. In the absence of clinical trials data in PUPs, there was general agreement that emicizumab prophylaxis, with it simpler subcutaneous (SQ) administration, might delay or potentially prevent inhibitors. Survey findings in Table 1 indicated 75% of physicians prescribe extended half-life (EHL) FVIII in a once-weekly prophylaxis regimen, as planned in the Prevention Trial, despite the persistent 27% inhibitor rate (ALong PUPs Trial, Königs et al, ISTH 2020) and potential risks with port use. There was support for the 1:3 preferential randomization to emicizumab in the Prevention Trial due to the simpler SQ route, despite concern it might delay rather than prevent inhibitor formation, although no inhibitors were reported by physician survey with emicizumab use alone. There was also concern that breakthrough bleeds requiring FVIII during emicizumab prophylaxis, might lead to immune activation and inhibitor formation. There was strong agreement, however, in 29 (97%) of physicians to participate in post-trial surveillance for long-term inhibitor outcomes. FVIII ITI was considered essential to eradicate inhibitors, despite the intensity of the infusion regimen. Notably, 60% prescribe emicizumab with FVIII ITI, as planned in the Eradicate Trial, although the every-other-day infusion was considered a potential barrier to participation. Omitting FVIII ITI was not favored due to the risk of inhibitor anamnesis if FVIII treatment was subsequently required for surgery or acute hemorrhages. Despite these concerns, there was agreement to participate in the trials. Discussion: Physician interviews and surveys confirm there is heterogeneity in current hemophilia clinical practice, specifically in initial prophylaxis regimens and in initial immune tolerance regimens, including agent choice and duration. However, there is physician consensus with the INHIBIT trial aims and with the proposed INHIBIT trial regimens to prevent and eradicate inhibitors. Disclosures Ragni: Bioverativ: Membership on an entity's Board of Directors or advisory committees, Research Funding; Alnylam/Sanofi: Membership on an entity's Board of Directors or advisory committees, Research Funding; BioMarin: Membership on an entity's Board of Directors or advisory committees, Research Funding; ATHN: Research Funding; Sangamo: Research Funding. Seaman:Bayer: Consultancy; Genentech: Consultancy; Spark Therapeutics: Consultancy; Takeda: Consultancy. Acharya:Novonordisk: Membership on an entity's Board of Directors or advisory committees; BPL: Membership on an entity's Board of Directors or advisory committees; Bayer Pharma Inc.: Research Funding. Wheeler:Novo Nordisk: Membership on an entity's Board of Directors or advisory committees; Biomarin: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; UniQure: Membership on an entity's Board of Directors or advisory committees. Tarango:Takeda/Shire: Honoraria, Other; Bayer: Consultancy, Other; Sanofi: Honoraria, Other. Dunn:ATHN: Research Funding; Spire: Honoraria; Medscape: Honoraria; World Federation of Hemophilia USA: Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding; BioMarin: Research Funding; uniQure: Consultancy; Genentech, Inc.: Consultancy; Nationwide Children's Hospital: Current Employment. Kulkarni:Sanofi/ Bioverativ, Bayer, Biomarin, Shire/Takeda, Novo Nordisk, Freeline: Other: clinical trial research grants ; Bioverativ/Sanofi, BPL, Genentech, Kedrion, Novo Nordisk, Octapharma, Pfizer, Takeda, Catalyst Bioscience Bayer: Membership on an entity's Board of Directors or advisory committees. Ahuja:Genentech: Consultancy, Honoraria; Sanofi Genzyme: Consultancy, Honoraria; XaTek, Inc.: Consultancy, Patents & Royalties, Research Funding. Chitlur:Takeda: Honoraria; Biovertiv: Honoraria; Agios Pharmaceuticals: Research Funding; Pfizer: Honoraria; Novo Nordisk: Consultancy, Honoraria. Pipe:Apcintex, Bayer, BioMarin, Catalyst Biosciences, CSL Behring, HEMA Biologics, Freeline, Novo Nordisk, Pfizer, F. Hoffmann-La Roche Ltd/Genentech, Inc., Sangamo Therapeutics, Sanofi, Takeda, Spark Therapeutics, uniQure: Consultancy; Siemens: Research Funding; Medical and Scientific Advisory Council to the National Hemophilia Foundation; Medical Advisory Board to World Federation of Hemophilia: Membership on an entity's Board of Directors or advisory committees. Malec:Sanofi Genzyme: Consultancy, Research Funding, Speakers Bureau; CSL: Consultancy; Takeda: Consultancy; Bayer: Consultancy; SOBI: Consultancy. Leissinger:Bayer: Consultancy; Kedrion: Consultancy; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Genentech: Consultancy; HEMA Biologics: Consultancy; Takeda: Consultancy; Uniqure: Consultancy; Spark: Consultancy. Carpenter:Hemostasis & Thrombosis Research Society: Membership on an entity's Board of Directors or advisory committees; American Academy of Pediatrics: Other: PREP Heme/Onc editorial board; Kedrion: Honoraria; Novo Nordisk: Honoraria; Genentech, Inc.: Honoraria; American Thrombosis and Hemostasis Network: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Research Funding; Shire: Research Funding. Knoll:NovoNordisk: Membership on an entity's Board of Directors or advisory committees. Wang:Bioverativ Inc: Honoraria; Bayer: Honoraria; CSL Behring: Honoraria; Biomarin: Honoraria; Genentech: Honoraria; Takeda: Honoraria. Young:Genentech/Roche, Grifols, and Takeda: Research Funding; Bayer, CSL Behring, Freeline, UniQure: Consultancy; BioMarin, Freeline, Genentech/Roche, Grifols, Kedrion, Novo Nordisk, Sanofi Genzyme, Spark, Takeda, and UniQure: Honoraria. Thornburg:Genentech: Speakers Bureau; Spark Therapeutics: Consultancy; Bluebird Bio: Consultancy; Ironwood Pharmaceuticals: Consultancy, Other: Data Safety Monitoring Board; American Thrombosis and Hemostasis Network: Research Funding; Sanofi Genzyme: Consultancy, Other: Data Safety Monitoring Board, Research Funding; NovoNordisk: Research Funding; Biomarin: Consultancy, Speakers Bureau; Bayer Pharmaceuticals: Research Funding; National Hemophilia Foundation: Membership on an entity's Board of Directors or advisory committees, Research Funding. Lucas:CRISPR Therapeutics: Membership on an entity's Board of Directors or advisory committees. Hwang:Shire: Honoraria; Takeda: Honoraria.

The antiphospholipid syndrome is characterized by venous or arterial thrombosis and/or recurrent fetal loss in the presence of circulating antiphospholipid antibodies. These antibodies cause activation of endothelial and other cell types leading to the release of microparticles with procoagulant and pro-inflammatory properties. The aims of this study were to characterize the levels of endothelial cell, monocyte or platelet derived, and tissue factor-bearing microparticles in patients with antiphospholipid antibodies, to determine the association of circulating microparticles with anticardiolipin and anti-β2-glycoprotein antibodies, and to define the cellular origin of microparticles that express tissue factor. Microparticle content within citrated blood from 47 patients with antiphospholipid antibodies and 144 healthy controls was analyzed within 2hours of venipuncture. Levels of Annexin-V, CD105 and CD144 (endothelial derived), CD41 (platelet derived) and tissue factor positive microparticles were significantly higher in patients than controls. Though levels of CD14 (monocyte-derived) microparticles in patient plasma were not significantly increased, increased levels of CD14 and tissue factor positive microparticles were observed in patients. Levels of microparticles that stained for CD105 and CD144 showed a positive correlation with IgG (R=0.60, p=0.006) and IgM anti-beta2-glycoprotein I antibodies (R=0.58, p=0.006). The elevation of endothelial and platelet derived microparticles in patients with antiphospholipid antibodies and their correlation with anti-β2-glycoprotein I antibodies suggests a chronic state of vascular cell activation in these individuals and an important role for β2-glycoprotein I in development of the pro-thrombotic state associated with antiphospholipid antibodies.

Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft tissue sarcomas that arise from peripheral nerve fibers and are derived from Schwann cells, perineural cells, or fibroblasts. MPNST is an aggressive neoplasm in which local recurrence is common and complete excision of the mass should be the goal of surgery. We report a case of MPNST involving the penis in a 14-month-old boy. This is only the second reported case of penile MPNST without evidence of neurofibromatosis 1 and the first of which to occur in a patient this young. (C) 2013 Elsevier Inc.

Abstract Abstract 148 Introduction: The antiphospholipid syndrome (APS) is characterized by venous or arterial thrombosis, and/or recurrent fetal loss in the presence of circulating antiphospholipid antibodies (APL). The pathogenesis of this disorder may involve, in part, the activation of vascular endothelial cells, platelets, and monocytes. Upon activation, these cells shed components of their plasma membranes as microparticles (MP), and procoagulant MPs are associated with an increased risk for thromboemboli. The goal of these studies was to characterize, for the first time, the frequency by which increased levels of endothelial cell, platelet and monocyte-derived microparticles are observed in freshly-obtained, unfrozen plasma from patients with APL. Patients and Methods: Whole citrated (3.2%) blood samples from patients/healthy donors were centrifuged at 1500xg for 15 min, and the supernatant further centrifuged at 13000xg for 2 min to obtain platelet free plasma (PFP). To detect microparticles, and their origin, PFP was labeled with the following conjugated monoclonal antibodies and analyzed by flow cytometry using an LSR II flow cytometer (BD): Annexin V-APC; CD105-PE and CD144-PE (endothelial cells); CD41-PECy5 (platelets); CD14-PE (monocytes); and anti-tissue factor mAb-Alexa Fluor 647 (a kind gift from Dr. Kenneth Mann, Univ of VT). The binding of control antibodies labeled with identical fluorophores as the monoclonal antibodies was subtracted to adjust for nonspecific binding. We assessed microparticles in 47 patients with APL and 144 healthy controls. Results Levels of annexin-V, CD105, CD144, CD41 and tissue factor positive microparticles were significantly higher in patients (47,000±7900, 10,140±2164, 46,690±8783, 127,200±28,050 and 7270±2810 microparticles/ml, respectively) versus controls (17,000±1800, 3,824±374, 17,320±2636, 54,910±7132 and 2,537±747 microparticles/ml, respectively). These differences were statistically significant. In contrast, there was no significant difference in CD14 positive microparticle levels (1035±167 in APL patients versus 1409±465 in controls; p=0.655). Conclusions: Our results demonstrate elevation of annexin V+, CD105+, CD144+, CD41+ and tissue factor-bearing microparticles in freshly-obtained, unfrozen plasma obtained from patients with APL. These results suggest that ongoing activation of platelets and endothelial cells occurs in many patients with APL even in the absence of active thrombosis, and may contribute to the prothrombotic phenotype of these patients. Data is currently being analyzed for associations of microparticle levels with APL serologies, as well as the expression of functional microparticle-associated tissue factor activity. Disclosures: No relevant conflicts of interest to declare.

CD36 is a scavenger receptor that binds multiple ligands, including phosphatidyl serine (PS). Although CD36(-) mice do not have a bleeding diathesis, we show here that they do have significantly prolonged thrombotic occlusion times in response to FeCl(3)-induced vascular injury. Because cell-derived microparticles (MPs) are generated in response to vascular injury and circulate in patients with prothrombotic diseases, we hypothesized that PS exposed on their surfaces could be an endogenous CD36 ligand that transmits an activating signal to platelets. We found that MPs prepared from human ECs, monocytes, or platelets or isolated from blood of normal subjects bound to platelets. Binding was not observed with platelets from CD36(-) donors and was inhibited by an anti-CD36 antibody or by blockade of exposed PS by annexin V or anti-PS IgM. Preincubation of platelets with MPs led to CD36-dependent augmentation of platelet activation in response to low doses of ADP, as assessed by measuring alpha(2b)beta(3) activation, P-selectin expression, and aggregation. Immunofluorescence confocal microscopy of murine carotid thrombi from CD36(-) mice showed a significant decrement in endothelial antigen accumulation, which suggests that CD36 plays a role in MP recruitment into thrombi. These results provide what we believe to be a novel role for CD36 in thrombosis.

Microparticles (MP) are cell membrane derived fragments released as a result of apoptosis or cellular activation that may be prothrombotic. Elevated numbers of microparticles may circulate in inflammatory and thrombophilic disorders. Here, we report a patient with Antiphospholipid Antibody Syndrome (APS) in whom increased levels of circulating microparticles preceded the onset of clinically-detectable deep venous thrombosis (DVT). The patient is a 36 year old Hispanic male with previously diagnosed APS (DRVVT ratio 2.6, ACA IgG > 120, and β2GPI IgG >100, IgA 74) complicated by several DVTs and transient ischemic attacks (TIA). Due to thrombosis on warfarin and enoxaparin, he was maintained on chronic therapy with fondaparinux. Microparticle analysis on three separate occasions was performed as part of an ongoing study of MPs in patients with antiphospholipid antibodies (aPL). The first analysis was performed during routine follow-up when the patient was asymptomatic. The second analysis was performed when the patient presented with complaints of left lower extremity tightness. Physical exam was normal, and Doppler ultrasound of the left lower extremity revealed chronic venous changes but no evidence of acute thrombosis. The patient was followed with plans for serial ultrasound examination. However, two days after this visit, the patient presented with acute DVT, confirmed by venous ultrasound. He was treated with five days of intravenous unfractionated heparin followed by reinstitution of fondaparinux. The third MP analysis was performed two weeks after the diagnosis of DVT. Isolation of MP was performed using a modification of previously described methods [Dignat-George et al, Thromb Haemost 91:668, 2004]. Platelet free plasma (PFP) was labeled with monoclonal antibodies for CD 144 and CD 105 (against endothelial cell VE cadherin and endoglin, respectively), and CD 41 (against platelet integrin αIIb) and analyzed by flow cytometry the same day as collection. Results of these analyses, expressed as number of MP/ml of PFP, are listed below.