Bypassing Agents Research Articles

Tranexamic acid as adjunct therapy to bypassing agents in haemophiliaApatients with inhibitors

Haemophilia patients with inhibitors require bypassing agents (BPA) like activated prothrombin complex concentrate (aPCC) and recombinant activated factor VII (rFVIIa) to control bleeds. Adjunct tranexamic acid (TXA) may improve haemostasis. The objective of this study was to investigate safety and haemostatic effect of TXA given in combination with BPA. Healthy volunteers (N=5) and haemophilia inhibitor patients (N=6) were enrolled in a prospective case crossover design. Controls were treated with TXA 20mgkg(-1) orally (O.R.) Patients were treated with aPCC 75IUkg(-1) intravenous (I.V.) on day 1 followed by TXA 20mgkg(-1) O.R. combined with aPCC 75IUkg(-1) I.V. on day 2. A 14-day washout occurred before crossover to rFVIIa 90μgkg(-1) I.V. ±TXA. Safety evaluation and blood sampling processes were performed at baseline, 15, 30, 60, 120, 180 and 240min post treatment. Primary outcome was maximum clot firmness (MCF) evaluated by whole blood thromboelastometry using a TF+tissue plasminogen activator-based assay. Healthy controls showed a 20-fold increase in MCF following TXA. Adjunct TXA to aPCC or rFVIIa induced a significant increase in MCF (P<0.0001) reaching levels indistinguishable from healthy controls treated with TXA (P>0.05). Infusion of aPCC or rFVIIa alone induced only 3-10 fold increase in MCF from baseline, with a decline in MCF starting after 60-120min. TXA did not increase the endogenous thrombin potential. No clinical or laboratory signs of thromboembolic events, disseminated intravascular coagulation, or hypercoagulability were observed. Combination of aPCC or rFVIIa with TXA normalizes clot stability in haemophilia patients with inhibitor as compared to healthy controls. No clinical or laboratory adverse events were observed.

Surgeryand Invasive Procedure With Bypassing Agents In Hemophilic Patients With Inhibitors: A Single Center Experience

Inhibitory antibodies to factor VIII (FVIII) or factor IX (FIX) are one of the most important complications of managing patients with hemophilia A and B. For hemophiliacs with inhibitors, recent advances in the use of bypassing agents such as recombinant activated FVII (rFVIIa, NovoSeven®) and Factor VIII Inhibitor Bypassing Activity (FEIBA®) have enabled them to aggressively manage their diseases in emergency or elective surgery. This report shows an updated evaluation of the safety and effectiveness of bypassing agents in the treatment of peri-operative bleeding in this patient population. We reviewed the cases of patients with hemophilia and inhibitors underwent surgery or other invasive procedures between May 2008 and July 2013 using bypassing agents or high dose FVIII concentrates at a single center. Thirty two procedures (23 orthopedic surgeries and 9 other surgeries and procedures) were conducted in 16 hemophilia patients with inhibitors. The median age of the patients was 30.5 years old (range, 7-52). Most patients (14/16, 87.5%) are hemophilia A and 2 patients (12.5%) were hemophilia B. The median titer of inhibitors at procedures was 15 BU (range, 0.7-1900). Patients with low responding inhibitors were 2 cases, and high dose factor VIII concentrates were used. Most patients had high responding inhibitors and one of two bypassing agents was used. Twenty one cases were covered using FEIBA®, nine with rFVIIa initially. The median duration of hospitalization was 14 days (range, 1-58). In most cases, bleeding stopped or controlled well. But, in 5 cases, patients’ bleeding was controlled by sequential bypassing therapy. 4 cases were performed at emergency conditions, and those are segmental resection of small bowel, craniectomy with intracerebral hematoma removal, exploratory thoracotomy, and angiography with embolization. Efficacy of bypassing agents at various surgeries and procedures, based on final patient outcome, was 93.8% (30/32). Two deaths occurred at emergency condition as a result of hypovolemic shock secondary to intracranial hemorrhage or retroperitoneal bleeding. Good control of hemostasis can be achieved with bypassing agents in hemophilia patients with inhibitors undergoing invasive procedures. If surgery or procedure would perform at emergency condition, more active and aggressive management should be needed. The use of bypassing agents in peri-operative period can allow invasive procedure and surgery to be safe and successful in hemophilic patients with inhibitors. Disclosures: No relevant conflicts of interest to declare.

Thrombin Generation Assay During Orthopaedic Surgery In Hemophilia A With and Without Inhibitors: Results From In Vivo Studies

BackgroundAlthough surgery is considered the major haemostatic challenge in patients with hemophilia, laboratory monitoring is limited to the measurement of factor VIII (FVIII) levels in response to concentrate infusions and the global effect of replacement therapy on the activation and maintenance of coagulation activation has never been investigated. Moreover, in hemophilia complicated by inhibitors no routine coagulation monitoring is available to assess haemostasis during surgery in patients receiving by-passing agents (BPA; namely, recombinant activated FVII, rFVIIa and activated prothrombin complex concentrate, aPCC). Thrombin generation assay (TGA) may be used to monitor haemostatic treatment both in inhibitor and non-inhibitor patients with hemophilia. The aims of this study were to investigate if the use of TGA in the surgical setting is able to provide information on global coagulation activation during FVIII replacement therapy and if it is related to the haemostatic and clinical response after BPA therapy in patients with inhibitors. MethodsThrombin generation was assessed in vivo in platelet-rich (PRP) and platelet-poor (PPP) plasma with the addition of corn trypsin inhibitor (CTI) in 17 patients with severe hemophilia A (9 with high-responding inhibitors) aged 5-59 years (median: 39) undergoing orthopaedic surgery at a single center. Four main parameters of the thrombin generation curve were evaluated: lagtime, endogenous thrombin potential (ETP), peak and time-to-peak. TGA was assessed once daily prior and 30 minutes after concentrate administration (FVIII or BPA) starting from the first pre-operative infusion and for at least the 4 consecutive post-operative days. Peri- and post-operative FVIII and BPA dosing and regimens were established according to our practice irrespective of TGA results. In non-inhibitor patients, FVIII levels were measured on the same blood samples drawn for TGA. ResultsIn the group of 8 non-inhibitor patients TGA values increased after the first FVIII concentrate infusion (i.e. pre-operative bolus), however during the post-operative period, when FVIII trough levels were maintained above 50 IU/dL in all patients, TGA was scarcely sensitive to the significant variation observed in FVIII levels prior (median: 74 IU/dL) and after (median: 155 IU/dL; p<0.001) FVIII daily infusions. A correlation between TGA parameters and FVIII levels was observed only for ETP and peak measured in PPP+CTI. No bleeding complication was observed in non-inhibitor patients, therefore no correlation between laboratory measurements and clinical outcome could be done. In the group of 9 inhibitor patients TGA values always increased after BPA administration however the test was not able to distinguish different haemostatic responses with respect to the type of drug (either rFVIIa or aPCC), the dose used and/or the occurrence of bleeding complications (n=5). Moreover, a lack of haemostatic response was detected by TGA over the post-operative period irrespective of treatment adjustments in all inhibitor patients. The results obtained in inhibitor patients were consistent both in PRP and PPP, with or without CTI. Finally, in both inhibitor and non-inhibitor patients TGA values after drug administration (either BPA or FVIII concentrates) were far from reaching normal values obtained in 17 healthy male controls. ConclusionsOur results indicate that TGA is not a suitable tool to monitor hemophilia treatment in the surgical setting. In fact, in non-inhibitor patients TGA was moderately sensitive to the haemostatic response to FVIII replacement therapy as compared to FVIII levels monitoring. On the other hand, in inhibitor patients TGA was not able to predict either the haemostatic response to different BPA and/or dosing regimens nor the risk of bleeding complications. Disclosures:No relevant conflicts of interest to declare.

Clinical use and the Italian demand for activated prothrombin complex and activated recombinant factor VII concentrates.

The activated prothrombin complex concentrate (aPCC, Factor Eight Inhibitor Bypassing Activity, FEIBA, Baxter, Deerfield, IL, USA) and the recombinant activated factor VII concentrate (rFVIIa, NovoSeven, Novo Nordisk A/S, Bagsvaerd, Denmark) are the so-called “by-passing agents”, i.e. products able to promote haemostasis through mechanisms alternative to the physiological tenase complex, in which a phospholipid-dependent reaction occurs with factor (F) X as the substrate, activated (a) FIX as the enzyme and FVIIIa as a cofactor1. The mechanism(s) of action of these agents are still not completely elucidated. The aPCC, which contains activated FII, FIX, FX and small amounts of FVII, is thought to facilitate thrombin generation on the platelet surface. This product was first introduced in clinical practice in 1975, as a therapeutic agent for haemophilia B when specific FIX concentrates were not available, and in the current vapour-heated formulation in 19852. The rFVIIa concentrate was specifically developed to provide a therapeutic approach in haemophilia with inhibitors, being able at high concentrations to enhance platelet-surface FXa generation, irrespective of the presence of FVIII or FIX3. The first use of rFVIIa was reported in 1988, and the product was registered in Europe in 1996 and in the United States in 1999. aPCC and rFVIIa are the mainstay of treatment of patients with congenital and acquired haemophilia (AH) with inhibitors4–6, in whom efficacy and safety of such agents have been documented over more than three and two decades of clinical use, respectively. As a specific replacement agent, rFVIIa is indicated in patients with factor VII deficiency7 and, as an alternative haemostatic agent, in patients with Glanzmann’s thrombasthenia (GT) and alloantibodies and/or platelet transfusion refractoriness8. Because of the rarity of the other recognised indications for treatment, most clinical and literature data regarding bypassing agents have been generated in the setting of congenital haemophilia with inhibitors. Before presenting the Italian demand for aPCC and rFVIIa in this 5-yr analysis, the clinical use of bypassing agents in the management of patients with bleeding disorders, in particular in those with congenital haemophilia and inhibitors, with the numerous challenges and open issues, will be concisely reviewed.

Diagnostic and therapeutic status of haemophilia in Latin America

Abstract The Latin American net of Prophylaxis and Immune Tolerance (RED LAPI) was established in 2010 and comprises a group of physicians dedicated to improving the diagnosis, treatment and quality of life of haemophilia patients in Latin America. The countries represented at RED LAPI are: Argentina, Chile, Uruguay, Venezuela, Colombia, Peru, Honduras, Guatemala, Paraguay, Dominican Republic, Bolivia, Ecuador and Panama. Analysis of the provision of care for haemophilia patients suggests a lack of consistent care both across and within Latin America countries. While some patients receive prophylaxis and immune tolerance induction (ITI), others are not even properly diagnosed, due to variation in patient’s health insurance. Few countries in Latin America have a national program that registers all patients’ information. Therefore, in many countries it is difficult to identify local, regional and national data regarding the number of diagnosed patients, type of hemophilia, severity, and the kind of treatment. With respect to patients with inhibitors, some countries rely on bypass agents for the treatment of bleeding episodes while a few are able to do ITI. This paper summarises available data obtained by a survey of RED LAPI members regarding the diagnosis and treatment of haemophilia in their countries, as well as the incidence of inhibitors and the treatments available to patients. Based on this analysis, the aim is to propose plans to improve the current situation of haemophilia patients in Latin America.

The Reversal of Inhibitors in Congenital Hemophilia

Hemophilias A and B are heritable bleeding disorders characterized by deficient baseline levels of factor VIII (fVIII) and factor IX (fIX), respectively. Standard treatment for acute bleeding events and for prophylaxis in patients with severe disease consists of recombinant fVIII and fIX infusions. The development of alloantibodies, or inhibitors, is a serious complication of congenital hemophilia that may impair the effectiveness of fVIII and fIX, leading to increased morbidity and cost of therapy. When inhibitors are present, bypassing agents such as recombinant activated factor VII and factor eight inhibitor bypass agent are available for treatment of bleeding events. Although usually effective, they are costly treatments. Immune-modulatory therapy may reverse inhibitors, allowing fVIII and fIX to be used again. Immune tolerance induction is the chief treatment option to decrease inhibitor levels, but about 20-30% of patients fail this treatment. Alternatively, multiple immune-modulating agents have been tried with limited success. Rituximab, an anti-CD20 monoclonal antibody, is one therapy that has been successful in reducing inhibitor titers in multiple case reports. Although current evidence is limited and questions regarding its use and place in therapy still exist, this agent shows promise for the future.

Liver-Directed Adeno-Associated Viral Gene Therapy for Hemophilia

Hemophilia A and B are monogenic bleeding disorders resulting from loss of functional coagulation factors VIII or IX, respectively. Prophylactic treatment requires frequent intravenous injections of exogenous factor VIII (F.VIII) or factor IX (F.IX), due to the short half-life of both factors. Hemophilia patients are at risk of developing neutralizing antibodies to F.VIII (~25-30%) or F.IX (~2-4%), which require the use of expensive bypass agents and immune tolerance induction protocols. Viral vector mediated liver gene transfer of F.VIII or F.IX offers an alternative treatment for hemophilia with easily defined clinical endpoints and no need for strict regulation of coagulation factor expression, as both proteins circulate as inactive zymogens. Adeno-associated viral (AAV) vectors are derived from a non-pathogenic human virus that efficiently transduce non-dividing cells, such as hepatocytes, and provide stable transgene expression. In vivo liver gene transfer of AAV-F.VIII and -F.IX vectors has restored hemostasis in murine and canine hemophilia models long-term, and has also been shown to induce immune tolerance. Consequently, two Phase I/II clinical trials have been conducted, based on hepatic AAV-FIX gene transfer to patients with severe hemophilia B. The first trial, utilizing serotype 2, demonstrated transient correction, which was limited by a cellular immune response against the viral capsid. However, sustained therapeutic expression has been achieved in a second trial, using AAV8 for expression of a codon-optimized F.IX transgene. Translation of F.VIII gene transfer studies into the clinic may require additional optimization of gene transfer and vector to effectively express the larger cDNA of F.VIII.

Thrombin Generation Assay Is Not Able to Predict Hemostatic Efficacy of by-Passing Agents in Patients with Hemophilia and Inhibitors: Results From in Vivo Studies

AbstractAbstract 41 BackgroundTherapy with by-passing agents (BPA) in patients with hemophilia and inhibitors still lacks a laboratory test able to assess the hemostatic response, often unpredictable by clinical assessment. Thrombin generation assay (TGA) has been used in order to guide therapeutic choices in this setting by testing the response after spiking in vitro haemophilic plasma with BPA. MethodsIn this study, thrombin generation was assessed in vivo in platelet-rich (PRP) and platelet-poor (PPP) plasma with the addition of corn trypsin inhibitor in 15 patients with severe hemophilia A and high-responding inhibitors aged 5–73 years (median: 34). Four main parameters of the thrombin generation curve were evaluated: lagtime, endogenous thrombin potential (ETP), peak and time-to-peak. TGA was assessed in 11 patients prior, 30 minutes and 3 (rFVIIa 120 and/or 270 mcg/kg) or 6 (aPCC 80 IU/kg) hours after drug injection in a non-bleeding state and a minimum wash-out period of 48 hours from the last BPA injection. It was also assessed once daily prior and 30 minutes after BPA administration in 9 patients undergoing orthopaedic surgery (7 major and 2 minor procedures). Haemostatic treatment to cover surgical procedures and post-operative period was established irrespective of TGA measurements. ResultsIn the group of 11 patients who received BPA in a non-bleeding state, the values of the parameters of the TGA curve were highly variable between patients as well as in the same patient both in PRP and in PPP (ANOVA p<0.01). Overall, ETP increased after drug administration in all cases, with similar results obtained in PRP (median ETP increase: 585 nMxmin, IQR: 226–997) and PPP (median increase: 552 nMxmin, IQR: 415–1013) and no difference observed with respect to product type and/or doses used. In all patients who underwent surgery but one, no changes in the TGA curve were obtained after drug administration at least twice during a 7-days post-operative period. Moreover, no difference in TGA results were observed according to the type of BPA used, but few data referable to aPCC administration were available. Five post-operative bleeding complications were observed: 4 were major complications due to excessive bleeding for more than 5 days irrespective of treatment dosing intensification and 1 was a minor complication controlled by increasing BPA dosing; baseline ETP values as well as ETP increases after repeated BPA administrations in the presence of a bleeding complication were similar (in PRP and PPP) to those detected in the absence of bleeding complications. Moreover, for those patients who underwent TGA measurement both in a non-bleeding state and during surgery, there was no correlation between the values obtained in the two different settings. ConclusionsOur data show that the high variability of TGA values observed between different subjects and in the same subject does not allow to use this test to predict and/or monitor the hemostatic efficacy of BPA in hemophilic patients with inhibitors. Disclosures:No relevant conflicts of interest to declare.

Trace FVIII Augments Rfviia Induced Thrombin Generation and Improves Hemostasis in Hemophilia A Patients with Inhibitors: A clinical Cohort Study

AbstractAbstract 40Treatment of Hemophilia A patients with inhibitors is challenging, as correlation between inhibitor level and hemostatic response to therapy may be limited. Thrombin generation (TG) assays may be used to monitor hemostasis and/or predict patients' response to various bypass agents. Since combination of excess FVIII and bypassing agents may potentiate improved TG in inhibitor plasma tested in-vitro, we aimed to define the therapeutic feasibility of co-administration of rFVIIa and FVIII in hemophilia A patients with inhibitors. Patients and Methods:Following consent, blood was sampled from 15 hemophilia patients (age: 0.5–46y) with inhibitor (0.5–668 BU). Platelet poor plasma (PPP) was prepared, spiked and incubated with excess FVIII. Ex-vivo kinetics of FVIII neutralization over time was evaluated by sequential measurements of residual FVIII activity. We then used recalcification induced-TG (performed in PPP supplemented with 4μM phospholipids), to measure the ex-vivo response to increasing concentrations of FVIII (0–200%) and rFVIIa (0–6.8μg/ml), alone or in combination. Based upon these ex-vivo studies, an individually tailored therapeutic regimen of concomitant bolus doses of rFVIIa and FVIII was applied to nine hemophilia patients with inhibitors. Results:FVIII ex- vivo measurements post incubation detected either rapid or slow neutralization- not correlating with inhibitor level. Flat baseline TG curves were recorded for all inhibitor patients, with variable responses to FVIII and/or rFVIIa. Combined spiking with FVIII and rFVIIa dramatically increased rFVIIa induced ETP (762.7 ±305.7 as compared to 339.3±179.9 nM/min with rFVIIa only) and peak height (48.7±23.6 vs 23.7±16.6) in all patients’ plasma samples. Based upon individual ex vivo assays, concomitant bolus doses of rFVIIa (120–200 mcg/kg) and FVIII (50–100 U/Kg), were applied to 9 patients, for a total of 333 episodes during study period (February 2010-Septemeber 2012). Patients during immune tolerance received rFVIIa prophylaxis with combined rFVIIa/FVIII dosing applied 3 times weekly. For most mild- moderate joint bleeds hemostasis was defined as satisfactory following a single combined dose. Severe bleeding episodes or target joint bleeds responded to 2–8 (median:3) combined doses, applied every 12 hours. During study period the median number of spontaneous joint bleeds decreased from 4 to 1 per month. Neither thrombosis nor any other complications evolved. Conclusions:Prediction of individual therapy response may be achieved by pre-analytical studies, assessing FVIII neutralization kinetics as well as ex-vivo TG responses to combined bypass/FVIII therapy. Such studies enabled treatment of inhibitor patients according to individually tailored regimens. We confirmed for the first time that the in- vitro advantage of combining FVIII and rFVIIa, indeed accounts for improved hemostasis and may safely be applied to inhibitor patients. Disclosures:No relevant conflicts of interest to declare.

Adverse Events in Treatment of Inherited Factor VII Deficiency: Final Analysis of the STER.

AbstractAbstract 2279 IntroductionNo evidence-based guidelines are available for the treatment of Factor VII deficiency. Replacement therapy (RT) is still influenced by different factors as rarity of the disorder, availability and supply of products and economic reasons. All RTs are not exempt of side effects and scanty data is available about the safety of the products currently used. Aim of this study was to analyze adverse events (AEs) of RTs for congenital Factor VII deficiency, as reported in Seven Treatment Evaluation Registry (STER). Design and MethodsFVII deficiency patients treated for bleeding episodes, prophylaxis, and surgery were investigated for RT-related AEs over a period of 8 years. STER is a prospective, observational, multicenter, web-based registry created to collect and describe data on treatment modalities and outcomes in patients with this rare bleeding disorder. Decisions on type of RT and schedules were autonomously taken by enrolling physicians. The STER reported the following information: AE clinical description, evaluation (serious or not), and potential association with the type of treatment adopted (likely, unlikely). Any AE was evaluated at the time of treatment and after 30 days or more if needed. ResultsSTER enrolled 223 patients for 308 different treatments with the following products: recombinant activated Factor VII (rFVIIa, n=241), plasma-derived Factor VII concentrates (pdFVII, n=31), Fresh Frozen Plasma (FFP, n=30),Prothrombin Complex Concentrate (PCC, n=5) and one case treated with Factor Eight Inhibitor Bypass Agent (FEIBA). Overall, fifteen AEs were recorded in 11 patients (8 M, 3 F; mean age: 31,7 y; range: 4m–75): twelve (80%) occurred in a surgical setting (n=138) while three (20%) for treatments for bleeding episodes (n=116). Among the individuals with reported AEs, 14 received rFVIIa and 1 was given pdFVII. Nine AEs were judged as likely related and six as unlikely related to the product.One AE event was life-threatening, seven were reported as serious, and seven as not serious. Likely-related AEs were the following: thrombosis (n=4;1 arterial thrombosis, 1 Superficial Vein Thrombosis, 2 Cerebral Infarctions), 2 cases of inhibitor development and 3 other (headache, hypertension and mild re-bleeding). In detail, inhibitor occurred in 2/125 (1.6%) of those in whom a centralized screening could be done, both high responders (20 and 10.4 BU max titres), one following pdFVII and one after rFVIIa (both previously exposed to pdFVII and FFP). All thrombotic episodes followed surgery. ConclusionIn the STER, AEs mainly occurred in surgical patients with an ovarall prevalence of thrombosis of < 4%. Inhibitor development occurred in less than 2% of the study population, in previously exposed patients. Finally, AE were not reported to significantly affect the patient’s management. Disclosures:Mariani:Novonordisk: Consultancy, Honoraria. Ingerslev:Novonordisk: Consultancy.

High dose of human plasma‐derived FVIII‐VWF as first‐line therapy in patients affected by acquired haemophilia A and concomitant cardiovascular disease: four case reports and a literature review

Haemostatic control is the first priority in acquired haemophilia A (AHA) and recent consensus recommendations suggest using bypassing agents (BAs) (recombinant activated FVII (rFVIIa) and activated prothrombin complex concentrate) as first-line treatment of bleeds. FVIII concentrates, both plasma-derived and recombinant, may be used with low inhibitor titre, minor haemorrhagic episodes and when bypassing drugs are not available [1]. The use of BAs may be associated with thrombotic complications, especially in the elderly with cardiovascular comorbidity, and should be carried out cautiously, as a literature review reported that 7% of patients treated with rFVIIa experienced thrombotic events [2]. Efficacy of FVIII concentrates in AHA has been reported since the early 1990s. Yet the published reports are retrospective, include few patients and deal with heterogeneous populations (see Table 1). Two main protocols have been recorded in the literature [3,4], but FVIII is often used at a much lower dosage. For instance, the data provided by the EACH2 Registry [5] reporting that the efficacy of FVIII treatment is lower than using BAs would show median doses inferior to those recommended in the literature (initial mean dose 50 U kg , total mean dose for patient 20 000 U, period-treatment range 4–6 days). This letter reports on the experience of our Centre in the use of high-dose human plasma-derived FVIII-VWF (HP-FVIII-VWF) concentrates in four patients affected by AHA and concomitant cardiovascular disease treated with a standardized protocol and include a review of the literature on the usage of HP-FVIII in the treatment of AHA.

PdFVIII/VWF may be an alternative treatment for old medical patient with acquired haemophilia A and systemic vascular disease?

Acquired Haemophilia is a severe, rare and potentially life-threatening bleeding that affects both males and females with an incidence of 1.5cases/million/year. Mucocutaneous haemorrhages or haematomas are the typical expression of this disease as a consequence of a decrease in FVIII activity and the presence of a FVIII inhibitor, which differs from congenital haemophilia. We report a case of a 71year-old-man who presented with spontaneous haematomas and severe anaemia and suffered from vascular disease. At admission, all haemostatic and laboratory data were diagnostic for idiopathic AHA. Treatment with by-passing agents such as rFVIIa was contraindicated because of the risk of thromboembolic events. Despite the fact that administration of FVIII concentrates in AHA is recommended only in patients with an inhibitor titre<5.0BU, the physicians decided to use pdFVIII/vWF with corticosteroids in this patient. One month later, the FVIII was within the normal range and the inhibitors had disappeared. In our case, pdFVIII/vWF resulted in a safe and effective alternative for the treatment of acquired haemophilia A in a patient at high thromboembolic risk.

Cost effectiveness of prophylactic treatment with activated prothrombin complex concentrate in a patient with inhibitor-positive hemophilia A

Patients with hemophilia and high titers of inhibitors are hard to treat during bleeding events and consequently are more likely to incur high treatment costs and to experience deterioration in quality of life. We report here the case of a boy with hemophilia A and high titers of inhibitors who responded well to prophylactic activated prothrombin complex concentrate (APCC) treatment. Previously, he had to be hospitalized frequently because of painful bleeding of target joints of the knee and ankle. At the age of 4 years and 3 months, APCC prophylaxis at a dose of 60 U/kg, three times a week, was initiated together with on-demand therapy with recombinant factor VIIa. This reduced the frequency and severity of bleeding and ended the need for hospitalization. This, together with a decreased requirement for bypass agents, APCC treatment significantly reduced the cost of treatment for this patient.

Feasibility of Using Thrombin Generation Assay (TGA) for Monitoring Bypassing Agent Therapy in Patients With Hemophilia Having Inhibitors

Monitoring bypassing agent therapy and observing concordance with clinical hemostasis is crucial in vital hemorrhages and major surgeries in patients with hemophilia having inhibitor. We aimed to investigate the value of the thrombin generation assay (TGA) and thromboelastography (TEG) for monitoring hemostasis in patients with hemophilia having inhibitor, during supplementation therapy with bypassing agents. The study group consisted of 7 patients with hemophilia having factor VIII inhibitor. All patients were male. The median age of the participants was 10 years. Age range was 6 to 32 years. The median inhibitor level was 10 Bethesda units (BU), with a range of 5 to 32 BU. A total of 17 bleeding episodes were evaluated. Both TEG and TGA tests were assessed in addition to clinical responses. Assessments were made prior to bypass agent therapy such as recombinant factor VIIa (rFVIIa) or activated prothrombin complex concentrate (aPCC) for bleeding episodes, during the first hour and 24 hours after either intervention in patients. No relation between clinical response and TGA or TEG parameters was found in patients. There was no difference between clinical responses after rFVIIa and aPCC treatments. However, after aPCC treatment, endogenous thrombin potential and peak thrombin levels and also TEG R, K, and alpha angle degrees were significantly higher. In conclusion, we found that the clinical effectiveness of bypass therapy in hemophilia cannot be assessed by TGA and TEG.

Ischemic stroke after recombinant factor VIIa treatment in acquired hemophilia A patient

Acquired hemophilia is a rare, life-threatening coagulopathy in adults caused by the development of autoantibodies against factor VIII. Bypass agents such as recombinant factor VIIa (rFVIIa) are usually preferred for bleeding control; however, thromboembolic complications may occur. We report here a case that presented with extensive cutaneous and mucosal bleedings due to factor VIII inhibitors and was treated successfully with rFVIIa and steroid therapy, but was complicated with a life-threatening thromboembolic attack during follow-up.

Thrombin Generation Test in Patients with Hemophilia and Inhibitors Treated with by-Passing Agents: Results From In Vivo Studies

Abstract 1216 Background:The development of inhibitors is the most serious complication of modern hemophilia therapy. Patients with inhibitors are often treated with by-passing agents (namely, aPCC and rFVIIa) whose haemostatic efficacy is not always predictable even in the same subject. Indeed clinical response to by-passing therapies may vary between patients and the lack of a specific laboratory test aimed at monitoring their ability in triggering blood coagulation and at correlating clotting activation to clinical outcome renders the management of these drugs somehow empirical. The thrombin generation (TG) test is a global coagulation assay that may serve as a candidate in this setting. Recently, dose tailoring of by-passing agents was performed using in vitro spiking experiments in order to establish the most adequate doses to cover elective surgery in hemophilic patients with inhibitors. Methods: In this study TG capacity was evaluated for the first time in vivo by drawing plasma samples from hemophilic patients with inhibitors treated either with aPCC or rFVIIa in a non-bleeding state after a minimum wash-out period of 3 days from the last infusion. TG test was performed in platelet-rich (PRP) and platelet-poor (PPP) plasma with the addition of corn trypsin inhibitor (CTI, final concentration 18.3 mcg/ml). Blood was drawn at baseline, 30 minutes, 3 hours (if rFVIIa), 6 hours (if aPCC) and 24 hours after drug administration. Four parameters of the TG curve were evaluated: lagtime, endogenous thrombin potential (ETP), peak and time to peak. Patients were defined as responders to by-passing agents when able to control mild/moderate bleeding episodes by home treatment with those drugs. Results: Eight patients with hemophilia A and high-responding inhibitors (historical peak above 5 BU/ml) with a median age of 33 years (IQR: 20–38) received rFVIIa at a standard dose of 90–120 mcg/kg and aPCC at a dose of 80 IU/kg. In 6 patients the TG test was performed also after the administration of a rFVIIa dose of 270 mcg/kg. Four patients were responders to aPCC, one to rFVIIa, 2 to both drugs and one was non-responder to both. Median values of the TG curve observed at baseline and 30 minutes after drug administration are shown in the Table. Similar variations in the TG curve were observed after administration of either rFVIIa or aPCC or after the administration of rFVIIa at the 2 different dosages. By evaluating only the patients responders to aPCC (n=4), there was no difference in the TG curves obtained after the administration of aPCC or rFVIIa. Conclusions: Our preliminary results show that the in vivo administration of by-passing agents causes an increase of TG capacity in hemophilic patients with inhibitors. However, the extent of such increase does not seem to be related neither with the type nor with the dose of these drugs. The evaluation of TG curve in response to by-passing agents will be performed also in haemophilic patients with inhibitors who underwent or will undergo major surgical procedures.Lagtime (min)ETP (nM x min)Peak (nM)Time to peak (min)PPPPRPPPPPRPPPPPRPPPPPRPBaseline aPCC9.913.223123510.97.922.927.6Baseline rFVIIa 90–120 mcg/kg1012.6179104.28.84.721.722.5Baseline rFVIIa 270 mcg/kg12.424.579.7622.62.622.526.930 minutes post-infusion aPCC5.911.3897921.2393416.447.430 minutes post-infusion rFVIIa 90–120 mcg/kg4.45.891394967.826.412.621.530 minutes post-infusion rFVIIa 270 mcg/kg5.810.471986742.626.214.934.2 Disclosures:No relevant conflicts of interest to declare.

Bypassing Agents in Children with Inhibitors: How Much Do We Use and How Much Is Too Much?

Abstract 1217 Background:Children with hemophilia A and high-titer inhibitors suffer frequent severe bleeding events and often respond to bypassing agents more poorly than adults resulting in increased dosing and cost. Aims: This study was conducted to determine the amount and variability of bypass agent therapy currently given to children with inhibitors at a large combined adult and pediatric hemophilia treatment center in comparison to treatment of adult inhibitor patients. Methods: All subjects were enrolled onto a single institution prospective inceptional cohort study of bleeding disorders with appropriate IRB-approved consent and assent. All children who developed high-titer inhibitors were treated with immune tolerance induction, and children treated with bypassing agents primarily represent difficult inhibitors. Data regarding treatment agents, dose and duration were extracted for 24 bleeding events in 6 children in comparison to comparable data on 26 bleeding events in 5 adults with high-titer inhibitors. Treatment decisions were made clinically by academic hematologists in consultation with hemophilia nurses, patients and parents based on perceived severity of bleeding events and therapeutic response. Treatment was given as recombinant factor VIIa (NovoSeven, N, n=28), prothrombin complex concentrates (FEIBA, F, n=10) or alternating doses of both (A, n=12). Median results for individual children and aggregated adult data are shown on Table 1. Children received seven times the treatment doses and duration compared with adults. In addition, children received both N and F for half of the bleeding events, while this was used for only one adult event. Treatment duration in children was not affected by initial dose or dose frequency of N (p > 0.05 for both). Bleeding events were severe and difficult to manage; significant long-term morbidity in these 6 children include ankle arthropathy in 3, elbow contracture following compartment syndrome in 2 and quadrucep pseudotumor in 1. [Display omitted] Discussion:Children with hemophilia A and inhibitors experience bleeding episodes that are poorly responsive to both N and F, resulting in higher dosing, longer duration and enormous costs. Children require better inhibitor therapies. Clinical trials of new bypassing agents designed specifically for children are urgently needed. Disclosures:No relevant conflicts of interest to declare.

A Novel FVIIa Variant with Increased Potency and Duration of Effect Compared to Wildtype FVIIa. A Study in a Dog Model of Hemophilia A

Abstract 2252Hemophilia patients are treated by replacement therapy, receiving the plasma-derived or recombinant clotting factor in which they are deficient. A significant number of hemophilia patients, however, develop inhibitory antibodies against the factor they receive, becoming refractory to replacement therapy. In these inhibitor patients, hemostasis can be achieved using bypass agents, activated plasma-derived prothombin complex concentrates (aPCC) or recombinant activated Factor VIIa (FVIIa). However, these treatments do not match the efficacy seen in traditional replacement therapy. To overcome this limitation, 813, a modified recombinant human Factor VIIa with enhanced biological properties was developed using a rational protein design approach. 813 was selected from a series of FVIIa variants and is characterized by increased catalytic activity and prolonged duration of effect in vivo. Compared to recombinant wild-type FVIIa, 813 has 7-fold increased catalytic activity, measured by the rate of Factor Xa generation in vitro, both in the presence and absence of tissue factor (TF).813 was studied in Factor VIII (FVIII)-deficient dogs with NovoSeven RT (wt-FVIIa) as comparator. The FVIII-deficient dogs exhibit a severe hemophilia A phenotype, with less than 1% normal coagulant activity. Dogs were dosed intravenously with 813 or wt-FVIIa and blood and plasma were collected at various time points post dosing. Plasma FVIIa levels were measured using a FVIIa-specific clotting assay. Starting from initial peak plasma levels, a time-dependent decrease in FVIIa plasma concentration was observed for wt-FVIIa and variant. Compared to wt-FVIIa, 813 exhibited a smaller volume of distribution (35–48 mL/kg vs. 108–134 ml/kg), a lower rate of clearance (10–18 mL/hr/kg vs. 45 mL/kg/hr) and consequently an increased dose adjusted exposure. Hemophilia A dogs have a prolonged activated partial thromboplastin time (aPTT); treatment with wt-FVIIa or 813 led to a dose-dependent decrease in aPTT. At equivalent doses the peak effect of 813 on decreasing aPTT was approximately two-fold compared to wt-FVIIa. Similar dose-dependent effects were observed when studying whole blood clotting profiles by thromboelastography (TEG). Treatment effects were seen for all TEG parameters monitored (time to clotting onset, rate and strength of clot formation). However, compared to wt-FVIIa, 813 given at equivalent doses caused significantly stronger effects on all TEG parameters; acute peak effects on TEG parameters measured for 813 at 10 ug/kg, were similar to those seen with 50 ug/kg wt-FVIIa. This difference became even more pronounced when monitoring treatment effect over time. All dogs used in this study were monitored throughout the study for possible treatment-related changes; both 813 and wt-FVIIa were well tolerated. No overt adverse events, no significant changes in plasma clinical chemistry or cellular blood counts were observed.In conclusion, 813 is a novel FVIIa protein with increased potency, prolonged duration of effect and a preclinical safety profile comparable to wt-FVIIa. 813 is currently in early clinical development for acute and prophylactic treatment of hemophilia patients with inhibitors. Disclosures:Pittman:Pfizer: Employment. Weston:Pfizer: Employment. Shields:Pfizer: Employment. Parng:Pfizer: Employment. Arkin:Pfizer: Employment. Madison:Catalyst Biosciences: Employment. Nichols:Pfizer: Research Funding. Fruebis:Pfizer: Employment.

Intra-Patient Variability in Recombinant Activated FVII (rFVIIa) Dosing Over 3 to 8 Year Periods in Patients with Congential Hemophilia with Inhibitors Experiencing Frequent Acute Bleeding Episodes: Analysis From the Hemostasis and Thrombosis Research Society (HTRS) Registry,

Abstract 3314 BACKGROUND:For congenital hemophilia patients who develop inhibitors to factors VIII or IX, the management of bleeding episodes can be complex, and often requires use of bypassing agents (BPA) such as rFVIIa (NovoSeven® RT). While some have reported on the variability in responsiveness to BPAs between patients, with the implication that some patients are more or less responsive to particular agents, few trial or registry data sets have sufficient long-term data to capture the intra-patient variability in dosing for specific bleed types or locations to identify if treatment is individualized on a patient basis or instead on a bleed-by-bleed basis by the hematologist and patient/caregiver. The HTRS Registry is a multi-center, longitudinal database of bleeding episodes and treatment patterns for bleeding disorder patients, with a particular focus on the treatment of acute bleeding episodes in inhibitor patients. METHODS:The HTRS registry recorded data between January 2004-March 2011 for 2,053 bleeding episodes in 134 inhibitor patients. From these data, we identified US patients with 75 or more rFVIIa-treated bleeding episodes and analyzed for intra-patient variability using descriptive statistics and graphical representations. RESULTS:5 patients (3 hemophilia A from 2 centers, 2 hemophilia B from 1 center) were identified with 568 rFVIIa-treated bleeds (28% of total recorded). Patients were White and Non-Hispanic, and ranged in age from 2.2 to 13.7 years old at the time of first reported bleed (2000–2005) and from 6.2 to 17.6 years old at the time of last reported bleed (2004–2008). Patients had 95–162 documented bleeds (mean 113.6) over 38–98 months (mean 62.5), with between 1 and 2.7 bleeds per month (mean 2.0). Median total dose per bleeding episode and interquartile ranges (IQR, 25%-75%) are shown below.Patient numberrFVIIa Trx BleedsStatisticTotal rFVIIa Dose Per Episode (mcg/kg)All BleedsTraumaticSpontaneousJointMuscleA162Median663.5816640640692IQR480–940524–1000469–906480–940465–927B106Median640595640600745IQR470–1000427.5–867480–1000414–820540–1140C103Median630855630675790IQR370–1109483–1363400–900450–1131485–1095D102Median570600600600540IQR360–960360–990424 –960480–960360–1485E95Median711474724.5774430IQR273–840354–592.5297–840492–840258–765Median total dose per episode for all bleeds varied from 570 to 711 mcg/kg, with the minimum reported dose of 50 mcg/kg and maximum of 43,200 mcg/kg. There was some variability but no consistent pattern across patients when comparing median doses for traumatic, spontaneous, joint, muscle and mucosal bleeds. The ratios of IQR/median and range/median total dose were also variable across patients and often across types within patients.The variability in total dose across bleed types/locations can also be demonstrated graphically as in the figures below (patient A, IQR - shaded, median – dotted line). Furthermore, initial doses were consistently above US package insert recommendations of 90 mcg/kg and high initial doses (>250 mcg/kg) were seen throughout 2002–2006. [Display omitted] [Display omitted] CONCLUSIONS:While registry data are subject to a variety of biases, they are able to capture real world data across patient populations that allows for assessment of variability between patients. In the case of the longstanding HTRS registry, we have the ability to also examine in a limited way differences in dosing within 5 individual patients across a 3–8 year period of childhood and adolescence. Surprisingly, or perhaps not so surprisingly, these exploratory analyses seem to indicate that treatment may be individualized by the hematologist (and hemophilia treatment center) and patient/caregiver for every bleed, and that even in individuals with many spontaneous, traumatic, or joint bleeds, treatment varies between mild bleeds treated with as little as one dose and severe bleeds or surgeries requiring prolonged treatment. Given the challenges of documentation of home treatment within medical records and consequently limited information available for assessment in registries, further analysis of co-variates that can account for these intra-patient variations (e.g. increasing frequency of target joint bleeds, extent of trauma, concurrent activities/sports/camp) will require prospective observational diary or registry studies that can capture additional information. Disclosures:Neufeld:Novo Nordisk Inc.: Consultancy, Research Funding. Off Label Use: rFVIIa (NovoSeven) is approved for the treatment of bleeding episodes in congenital hemophilia with inhibitors; doses shown in this abstract might differ from the US prescribing information. Cooper:Novo Nordisk Inc.: Employment.

Factor VIII Supplementation Improves Recombinant VIIa Initiated Thrombin Generation in Hemophilia A Inhibitor Patient Plasmas

Abstract 28▪▪This icon denotes a clinically relevant abstractHemophilia A is an X-linked recessive disorder that is caused by a deficiency or defect of factor VIII (fVIII) coagulant protein. Approximately 20–30% of patients with severe hemophilia A develop antibodies (Abs) against fVIII (inhibitors) following fVIII replacement therapy, which makes bleeding episodes more difficult to control. Patients with inhibitors are treated with fVIII-bypassing agents such as recombinant factor VIIa (rfVIIa) or activated prothrombin-complex concentrate. However for unknown reasons, some patients display poor hemostatic response to bypass therapy and improved treatment options are needed. Thrombin generation assays provide an in vitro methodology for monitoring bypass therapy in hemophilia (Turecek PL et al. Pathophysiol Haemost Thromb 2003; Varadi K et al. Haemophilia 2004). Recently, it was demonstrated by us and others that combination of fVIII and by-passing agents potentiates in vitro thrombin production in hemophilia A inhibitor plasma (Klintman J et al. Br J Haematol 2010). In our study we investigated the potentiation fVIII confers to fVIIa initiated in vitro thrombin generation using a panel of anti-fVIII Abs with known epitopes. We showed that kinetics of inhibition and Ab epitope were the dominant factors influencing ability of fVIII to potentiate in vitro thrombin production. Specifically, monoclonal Abs targeting only 2 of 11 epitopes, 1 of 3 non-overlapping A2 epitopes and 1 of 2 non-overlapping C2 epitopes, inhibited thrombin generation in a manner that could not be recovered by fVIII supplementation. Here, we analyzed in vitro thrombin generation in epitope-mapped plasmas from 10 patients with hemophilia A and long-standing inhibitors after addition of fVIIa alone or in conjunction with fVIII. Methods: FVIII inhibitor plasmas from 10 patients with hemophilia A were obtained as part of an IRB approved study at the Emory Comprehensive Hemophilia Center. FVIII inhibitor titers and inhibitor kinetics were determined using a modified Bethesda assay. Samples were classified as having type II inhibitors if undiluted plasma resulted in incomplete inhibition of residual fVIII activity (Meeks SL et al. Blood 2007). Thrombin generation assays were carried out in the presence of 2.25 μg/ml recombinant fVIIa in the presence or absence of 1 U/ml recombinant full-length fVIII using reagents purchased from DiaPharma (West Chester, OH). The parameters analyzed include endogenous thrombin potential (area under thrombin generation curve), peak thrombin concentration, time to peak thrombin, lag time (time to 1/6th of peak thrombin) and index velocity (Vi-peak thrombin divided by time to peak minus lag time). Domain specific epitope mapping was carried out using direct ELISA and human/porcine domain hybrid fVIII proteins. Results: Domain mapping of the Abs in the plasmas identified 2 plasmas with predominantly anti-A2 Abs, 4 with predominantly anti-C2 Abs, 2 with both anti-A2 and anti-C2 Abs, and 2 with antibodies that were porcine fVIII cross-reactive (see Table). Plasmas with inhibitor titers less than 25 BU/ml were more responsive to fVIII supplementation with 6 of 7 having increased thrombin generation. Plasmas harboring even trace anti-A2 Abs were more resistant to increased thrombin generation with fVIII supplementation than plasmas with anti-C2 Abs alone. Conclusion: This study suggests a more favorable response to fVIII supplementation of rfVIIa may be predicted by the presence of anti-C2 Abs or inhibitory titers less than 25 BU/ml. In conjunction with our previous monoclonal Ab data, further mapping of epitopes within the fVIII A2 and C2 domains may help improve the ability to predict positive responses to fVIII supplementation of by-passing agents.PatientInhibitor Titer (BU/ml)DomainFVIII InhibitorThrombin Generation (fVIII + fVIIa vs. fVIIa)122A2Type IIIncreased242A2Type IIEqual384C2, small A2Type IEqual47C2Type IIncreased58C2Type IIIncreased620C2Type IEqual78C2Type IIncreased842C2, small A2Type IEqual922Porcine cross-reactiveType IIIncreased105.2Porcine cross-reactiveType IIncreased Disclosures:No relevant conflicts of interest to declare.