In vivo coagulation activation following infusion of highly purified factor XI concentrate

Combined thrombogenic effects of vessel injury, pregnancy and procoagulant immune globulin administration in mice

Background

Pregnant women are at increased risk of thrombotic adverse events. Plasma derived immune globulin (IG) products, which are used in pregnancy for various indications, may contain procoagulant impurity activated coagulation factor XI (FXIa). Procoagulant IG products have been associated with increased thrombogenicity but their effect in pregnancy is unknown.

Methods

Late pregnant (gestation days 17–20) or early lactation (days 1–3) and control female mice were treated with IGs supplemented with human FXIa then subjected to ferric chloride (FeCl₃) vessel injury. Occlusion of blood vessel was assessed by recording blood velocity in the femoral vein for 20 min using doppler ultrasound laser imaging. FXIa dose was selected by the ability to increase thrombin generation in mouse plasma in vitro.

Results

FXIa produced robust thrombin generation in mouse plasma ex vivo. Following FeCl₃ injury, pregnant and non-pregnant mice receiving IG + FXIa exhibited faster reduction of blood velocity in femoral vein compared to IG alone or untreated controls. In vitro, thrombin generation in plasma samples collected after thrombosis in FXIa-treated animals was elevated and could be reduced by anti-FXI antibody.

Conclusions

Our results suggest that intravenously-administered FXIa may contribute to thrombosis at the site of vascular injury in both pregnant and non-pregnant animals.

Supplementary Information

Supplementary information accompanies this paper at 10.1186/s12959-020-00245-8.

Synergy Between Tissue Factor and Exogenous Factor XIa in Initiating Coagulation

OBJECTIVE

Recent evidence suggests involvement of coagulation factor XIa (FXIa) in thrombotic event development. This study was conducted to explore possible synergies between tissue factor (TF) and exogenous FXIa (E-FXIa) in thrombin generation.

APPROACH AND RESULTS

In thrombin generation assays, for increasing concentrations of E-FXIa with low, but not with high TF concentrations, peak thrombin significantly increased whereas lag time and time to peak significantly decreased. Similar dependencies of lag times and rates of thrombin generation were found in mathematical model simulations. In both in vitro and in silico experiments that included E-FXIa, thrombin bursts were seen for TF levels much lower than those required without E-FXIa. For in silico thrombin bursts initiated by the synergistic action of TF and E-FXIa, the mechanisms leading to the burst differed substantially from those for bursts initiated by high TF alone. For the synergistic case, sustained activation of platelet-bound FIX by E-FXIa, along with the feedback-enhanced activation of platelet-bound FVIIIa and FXa, was needed to elicit a thrombin burst. Furthermore, the initiation of thrombin bursts by high TF levels relied on different platelet FIX/FIXa binding sites than those involved in bursts initiated by low TF levels with E-FXIa.

CONCLUSIONS

Low concentrations of TF and exogenous FXIa, each too low to elicit a burst in thrombin production alone, act synergistically when in combination to cause substantial thrombin production. The observation about FIX/FIXa binding sites may have therapeutic implications.

Factor XI replacement for inherited factor XI deficiency in routine clinical practice: results of the HEMOLEVEN prospective 3-year postmarketing study

Factor XI (FXI)-deficient patients may develop excessive bleeding after trauma or surgery. Replacement therapy should be considered in high-risk situations, especially when FXI levels are below 20 IU dL(-1) . HEMOLEVEN is a human plasma-derived factor XI concentrate available in France since 1992, but there are few data regarding its use by physicians. This prospective study assessed the use, efficacy and safety of HEMOLEVEN in common clinical practice. HEMOLEVEN was evaluated in FXI-deficient patients in 13 French centres in a 3-year postmarketing study. Forty-four patients (30 females, 14 males) received 67 treatments. The median age was 37 years (8 months-91 years). Basal FXI levels were <1 to 51 IU dL(-1) (median: 5.5); 29 patients were severely FXI-deficient (<20 IU dL(-1) ). FXI was administered prophylactically before 43 surgical procedures, 10 invasive procedures, 8 vaginal deliveries, or as curative treatment for six bleeds. The efficacy was assessed as excellent/good in 63, moderate in two and undetermined in two treatments. Seven patients experienced seven adverse effects, including two rated as serious: one sudden massive pulmonary embolism with fatal outcome and one case of inhibitor to FXI. HEMOLEVEN is effective for bleeding prevention in FXI deficiency. However, considering the benefit/risk ratio observed in relation to dosage in this study; firstly, it should be used sparingly due to its potential prothrombotic effect; secondly, new prescription procedures should be defined to adapt the dosage, especially in patients with intrinsic and/or acquired risk factors for thrombosis.

Evidence for factor IX-independent roles for factor XIa in blood coagulation

BACKGROUND

Factor XIa is traditionally assigned a role in FIX activation during coagulation. However, recent evidence suggests this protease may have additional plasma substrates.

OBJECTIVE

To determine whether FXIa promotes thrombin generation and coagulation in plasma in the absence of FIX, and to determine whether FXI-deficiency produces an antithrombotic effect in mice independently of FIX.

METHODS

FXIa, FXIa variants and anti-FXIa antibodies were tested for their effects on plasma coagulation and thrombin generation in the absence of FIX, and for their effects on the activation of purified coagulation factors. Mice with combined FIX and FXI deficiency were compared with mice lacking either FIX or FXI in an arterial thrombosis model.

RESULTS

In FIX-deficient plasma, FXIa induced thrombin generation, and anti-FXIa antibodies prolonged clotting times. This process involved FXIa-mediated conversion of FX and FV to their active forms. Activation of FV by FXIa required the A3 domain on the FXIa heavy chain, whereas activation of FX did not. FX activation by FXIa, unlike FIX activation, was not a calcium-dependent process. Mice lacking both FIX and FXI were more resistant to ferric chloride-induced carotid artery occlusion than FXI-deficient or FIX-deficient mice.

CONCLUSION

In addition to its predominant role as an activator of FIX, FXIa may contribute to coagulation by activating FX and FV. As the latter reactions do not require calcium, they may make important contributions to in vitro clotting triggered by contact activation. The reactions may be relevant to FXIa's roles in hemostasis and in promoting thrombosis.

Pulmonary embolism and fatal stroke in a patient with severe factor XI deficiency after bariatric surgery

We report the case of a 40-year-old woman with a severe factor XI (FXI) deficiency who died from a stroke due to bilateral internal carotid arteries occlusion after a laparoscopic gastric bypass (bariatric surgery). This stroke was probably secondary to a pulmonary embolism with a paradoxical embolism through a previously unknown foramen ovale. This woman who had one severe episode of bleeding before the bypass received for the intervention a single infusion of 27 U/kg of FXI concentrate. A careful evaluation of the bleeding and thrombotic risk was performed before surgery, and despite all preventive measures, this tragic event occurred. The aim of this report is to alert medical teams to carefully balance the benefit-risk of such an intervention in a patient with a severe FXI deficiency.

Successful hip arthroplasty in an adult male with severe factor XI deficiency using Hemoleven®, a factor XI concentrate

Severe factor XI (sFXI) deficiency is a rare bleeding disorder (RBD). FXI replacement is most often required for surgical hemostasis. Plasma, the sole US treatment option, is often complicated by life-threatening allergic reactions. In such circumstances, the FDA offers a mechanism for institution-industry collaboration to facilitate limited use of replacement products licensed abroad. A 58 years old man with sFXI deficiency, required hip replacement. In the past, he received prophylactic plasma for thyroidectomy and experienced a severe allergic reaction. A single use institutional IND FDA application was initiated in collaboration with LFB (Les Ulis, France) to access Hemoleven®, a plasma-derived FXI concentrate. The application required an investigator-initiated IRB-approved protocol for treatment and safety/efficacy monitoring that included: preoperative thrombophilia, FXI inhibitor and pharmacokinetic (PK) evaluations; peri- postoperative administration of ≤ 4 doses of 10-15 U/kg Hemoleven® ; DIC monitoring; postoperative thromboprophylaxis; observation for product efficacy and potential complications. PK study demonstrated the expected 1.8% FXI recovery per U/kg with half-life of 62 hours. Mild D-Dimer elevation was noted 6-9 hours post-infusion. The initial dose (15 U/kg) was administered 15 hours before surgery; subsequently, 3 doses (10 U/kg) were infused every 72 hours. Hemostasis was excellent. No complications were observed. Collaboration allowed for successful patient access to Hemoleven® with excellent PK, safety, and efficacy. This case underscores the need for additional efforts to ensure safe and effective licensed replacement therapies for RBD patients.

Guideline on the selection and use of therapeutic products to treat haemophilia and other hereditary bleeding disorders. A United Kingdom Haemophilia Center Doctors' Organisation (UKHCDO) guideline approved by the British Committee for Standards in Haematology

Evidence-based guidelines are presented on the selection and use of therapeutic products to treat haemophilia and other hereditary bleeding disorders. They include details of therapeutic products available in the UK and they update and replace previous United Kingdom Haemophilia Centre Doctors' Organisation guidelines.

Genetics of coagulation: considerations for cardiac surgery

Genetic variants in the coagulation system have been known since antiquity. Today, because of modern improvements in diagnosis and medical management, the clinician is likely to encounter a spectrum of coagulation factor deficiencies and identified polymorphic variants in the surgical population. Because perioperative hemorrhagic and thrombotic complications are potentially serious, it is important to understand the role that these defects and variants may play in predicting risk and optimizing patient management. The implications of coagulation genetics on the perioperative management of the cardiac surgery patient are reviewed.

Recessively inherited coagulation disorders

Deficiencies of coagulation factors other than factor VIII and factor IX that cause bleeding disorders are inherited as autosomal recessive traits and are rare, with prevalences in the general population varying between 1 in 500 000 and 1 in 2 million for the homozygous forms. As a consequence of the rarity of these deficiencies, the type and severity of bleeding symptoms, the underlying molecular defects, and the actual management of bleeding episodes are not as well established as for hemophilia A and B. We investigated more than 1000 patients with recessively inherited coagulation disorders from Italy and Iran, a country with a high rate of recessive diseases due to the custom of consanguineous marriages. Based upon this experience, this article reviews the genetic basis, prevalent clinical manifestations, and management of these disorders. The steps and actions necessary to improve the condition of these often neglected patients are outlined.

Current therapy for rare factor deficiencies

Haemophilia A and B and von Willebrand disease account for 80-85% of all inherited bleeding disorders. The other 15% are represented by deficiencies of fibrinogen, prothrombin, or factors V, VII, X, XI, or XIII. In addition, acquired factor deficiencies are seen in a variety of conditions ranging from malignancies to autoimmune disorders. The spectrum of symptoms in these conditions varies from severe and life-threatening haemorrhage to a mild bleeding diathesis. The diagnosis depends on demonstration of decreased activity of one of the clotting factors. Due to the rarity of each of the individual factor deficiencies, purified factor concentrates are not as readily available as they are for haemophilia A and B. Treatment of rare clotting factor deficiencies consists of the most purified blood product available that contains the missing factor. Depending on which factor is deficient, either purified concentrates, prothrombin complex concentrates, cryoprecipitate, or fresh frozen plasma can be used. In addition, recombinant factor VIIa is available for treating factor VII deficient patients.

Factor XI deficiency and its management

Factor XI deficiency has a more variable bleeding tendency than haemophilia A or B. Individuals with severe deficiency have only a mild bleeding tendency, which is typically provoked by surgery, but the risk of bleeding is not restricted to individuals with severe deficiency. The bleeding tendency varies between individuals with similar factor XI levels, and sometimes the bleeding tendency of an individual may vary. The reasons for this are not fully understood, although in cases of severe deficiency there is some correlation between phenotype and genotype. Factor XI is activated by thrombin. The role of factor XI in physiological processes has become clearer since this fact was discovered, and the discovery has contributed to a revised model of blood coagulation. Factor XI deficiency occurs in all racial groups, but is particularly common in Ashkenazi Jews. The factor XI gene is 23 kilobases long. Two mutations are responsible for most factor XI deficiency in the Ashkenazi population, but a number of other mutations have now been reported in other racial groups. Individuals with factor XI deficiency may need specific therapy for surgery, accidents, and dental extractions. Several therapies are available which include fresh frozen plasma, factor XI concentrates, fibrin glue, antifibrinolytic drugs, and desmopressin. Each has advantages and risks to be considered. Factor XI concentrate may be indicated for procedures with a significant risk of bleeding especially in younger patients with severe deficiency, but its use in older patients has been associated with thrombotic phenomena. If fresh frozen plasma is to be used it is preferable to obtain one of the virally inactivated products. Fibrin glue is a useful treatment which deserves further study.

Safety of coagulation factor concentrates

Many of the adverse effects of the early crude plasma-derived concentrates were ameliorated by increasing their purity. Ironically, this strategy may have increased the risks of inhibitor formation and pathogen transmission due to the addition of processing steps which can alter the immunogenicity of clotting factors and the use of very large plasma pools, as dictated by economic considerations. In the absence of extremely sensitive donor screening, these large pools have a high probability of contamination with pathogens, which may be only partially offset by their removal during protein purification. One approach to minimize the risk of viral transmission is to use recombinant clotting factors produced without the use of human or animal plasma proteins at any step in the manufacturing or formulation process. However, as these proteins are synthesized in mammalian cells, even they pose a theoretical risk of pathogen transmission. For plasma-derived concentrates, the initial viral burden is minimized by screening individual donations and plasma pools with tests which detect virus-specific antibodies, protein antigens, or nucleic acid. These techniques are supplemented by non-specific viral reduction steps based on physical partitioning and/or inactivation of pathogens which share chemical or physical characteristics. Prion proteins, the putative causative agents of transmissible spongiform encephalopathies, do not share these characteristics with viruses, and it remains to be determined whether they partition into clotting factor concentrates and whether the current strategies can efficiently remove or inactivate them. For all blood-borne pathogens, active immunization (currently available only for hepatitis B and A) and continued surveillance of susceptible recipients are critical approaches to achieving optimal safety of coagulation factor concentrates.

The management of factor XI deficiency

Factor XI deficiency leads to a more variable bleeding tendency than haemophilia A or B. Although severely deficient individuals are likely to bleed excessively especially after surgery in areas of the body with increased fibrinolysis, there is evidence that some partially deficient individuals are at risk of excessive bleeding. This will entail careful planning for surgery. Several therapeutic modalities are available which include fresh frozen plasma, factor XI concentrates, fibrin glue, antifibrinolytic drugs and desmopressin. The advantages and risks of these are considered. Factor XI concentrate may be indicated for procedures with a significant risk of bleeding especially in younger patients with severe deficiency, but its use in older patients has been associated with thrombotic phenomena. If fresh frozen plasma is to be used, it is preferable to obtain one of the virally inactivated products. Fibrin glue is a useful treatment which deserves further study.