Fitusiran reduces bleeding in factor X-deficient mice.

ABSTRACT: Factor X (FX) deficiency is a rare bleeding disorder manifesting a bleeding tendency caused by low FX activity levels. We aim to explore the use of fitusiran (an investigational small interfering RNA that silences antithrombin expression) to increase thrombin generation and the in vivo hemostatic potential under conditions of FX deficiency. We therefore developed a novel model of inducible FX deficiency, generating mice expressing <1% FX activity and antigen (f10low mice). Compared with control f10WT mice, f10low mice had sixfold and fourfold prolonged clotting times in prothrombin time and activated partial prothrombin time assays, respectively (P < .001). Thrombin generation was severely reduced, irrespective of whether tissue factor or factor XIa was used as an initiator. In vivo analysis revealed near-absent thrombus formation in a laser-induced vessel injury model. Furthermore, in 2 distinct bleeding models, f10low mice displayed an increased bleeding tendency compared with f10WT mice. In the tail-clip assay, blood loss was increased from 12 ± 16 µL to 590 ± 335 µL (P < .0001). In the saphenous vein puncture (SVP) model, the number of clots generated was reduced from 19 ± 5 clots every 30 minutes for f10WT mice to 2 ± 2 clots every 30 minutes (P < .0001) for f10low mice. In both models, bleeding was corrected upon infusion of purified FX. Treatment of f10low mice with fitusiran (2 × 10 mg/kg at 1 week interval) resulted in 17 ± 6% residual antithrombin activity and increased thrombin generation (fourfold and twofold to threefold increase in endogenous thrombin potential and thrombin peak, respectively). In the SVP model, the number of clots was increased to 8 ± 6 clots every 30 minutes (P = .0029). Altogether, we demonstrate that reduction in antithrombin levels is associated with improved hemostatic activity under conditions of FX deficiency.

Plasma-derived human factor X concentrate for the treatment of patients with hereditary factor X deficiency.

INTRODUCTION: Hereditary factor X (FX) deficiency (HFXD) is an autosomal recessive rare bleeding disorder that leads to defects in the FX protein. Depending on the degree of deficiency, patients may be at risk of life-threatening bleeding episodes. Historical treatments for FX deficiency include prothrombin complex concentrates, which can increase the risk of thrombosis, and fresh frozen plasma, which can cause volume overload and transfusion reactions. Plasma-derived FX (pdFX), a single-factor, high-purity, high-potency human FX treatment, was approved in 2015 in the United States and in 2016 in Europe for on-demand treatment and prophylaxis of bleeding episodes and perioperative management of patients with HFXD. METHODS: Five studies that examined the use of pdFX in patients with mild (plasma FX activity [FX:C] ≥5 IU/dL), moderate (FX:C ≥1 and <5 IU/dL), or severe (FX:C < 1 IU/dL) HFXD were reviewed: TEN01, TEN02 and TEN03 were prospective, open-label, multicentre, nonrandomised studies, and TEN05 and TEN06 were multicentre retrospective studies. RESULTS: When used as an on-demand treatment, pdFX was judged by investigators to be successful in treating 41/42 (97.6%), 2/3 (66.6%) and 79/79 (100%) bleeds in TEN01, TEN02 and TEN05, respectively. When used prophylactically, pdFX was judged 'excellent' for the prevention of bleeds in nine (100%) and eight (100%) patients in TEN02 and TEN05, respectively. Perioperative treatment and pharmacokinetics were also assessed. pdFX was safe and well tolerated. CONCLUSIONS: Together, these studies support the use of pdFX for on-demand treatment of bleeding, routine prophylaxis, and perioperative management of bleeding in patients with HFXD.

Preclinical development and characterization of a human plasma-derived high-purity factor X concentrate for therapeutic use.

INTRODUCTION: Hereditary factor X deficiency is a rare bleeding disorder, with limited treatment options. This paper describes the approach to pre-clinical development and characterization of a high-purity plasma-derived factor X concentrate, to achieve orphan drug marketing authorization for the treatment of hereditary factor X deficiency. METHODS: A chromatographic process was developed, to purify factor X from human plasma for fractionation. The product was characterized using in vitro, in vivo and ex vivo tests for potency, purity, thrombogenicity, immunogenicity, toxicity and stability. RESULTS: The production process complied with good pharmaceutical manufacturing practice. It achieved 6000-fold purification and 100-fold concentration of the factor X protein compared to human plasma. The factor X protein was 94%-96% pure. Other residual plasma proteins were well below levels in plasma, minimizing potential interference in hemostasis after therapeutic administration. Effective virus-reduction during manufacture, and the absence of thrombogenicity, toxicity and immunogenic potential were confirmed, addressing the main safety concerns historically associated with plasma-derived therapeutics. The freeze-dried product remained stable between +2°C and +30°C for at least three years. After reconstitution with water for injections, the factor X activity was maintained for at least 48 h at +18°C to +22°C. CONCLUSION: Targeted pre-clinical development of the first highly-purified concentrate to treat hereditary factor X deficiency is described. Following international guidelines for nonclinical safety testing, particular strategies were adopted for unmodified products derived from human blood plasma. This approach may also be relevant to the development of other ultra-orphan medicinal products.

A review of the pharmacokinetics, efficacy and safety of high-purity factor X for the prophylactic treatment of hereditary factor X deficiency.

INTRODUCTION: Hereditary factor X (FX) deficiency (FXD) is a rare autosomal recessive bleeding disorder. Plasma-derived FX (pdFX) is a high-purity FX concentrate approved in the United States and Europe for the treatment and prophylaxis of bleeding episodes and for peri-operative management in patients with hereditary FXD (HFXD). AIM: To review pharmacokinetic dosing, efficacy, and safety data for pdFX as routine prophylaxis for HFXD. METHODS: Summary of the published pharmacokinetic and safety data from TEN01, TEN02, TEN05, and real-world publications of pdFX for prophylaxis. RESULTS: Pharmacokinetic modelling data from the phase 3 TEN01 study supported administration of pdFX 25 IU/kg twice weekly for routine prophylaxis in adolescents/adults (aged ≥12 years). Results from nine paediatric patients in the phase 3 TEN02 study and eight adolescents/adults (aged ≥12 years) in the retrospective data-collection TEN05 study, along with real-world evidence, showed that routine prophylaxis with pdFX ≈40 IU/kg twice weekly in patients aged <12 years and pdFX ≈25 IU/kg twice weekly in patients aged ≥12 years was effective in bleeding prevention. CONCLUSIONS: pdFX was well tolerated in clinical studies, with no new safety signals identified during routine prophylactic use. Based on current evidence, it is recommended that routine prophylaxis with pdFX be initiated at 25 IU/kg twice weekly in adults/adolescents ≥12 years of age, and at a dosage of 40 IU/kg twice weekly in children <12 years of age. Thereafter, FX levels should be closely monitored, and dosages should be adjusted according to clinical response and to maintain trough levels ≥5 IU/dl.

Pharmacokinetics of a high-purity plasma-derived factor X concentrate in subjects with moderate or severe hereditary factor X deficiency.

INTRODUCTION: Hereditary factor X (FX) deficiency affects 1:500 000 to 1:1 000 000 of individuals. There are few published data on the pharmacokinetics (PK) of FX for existing treatments for FX deficiency, and no specific replacement factor concentrate exists. A high-purity plasma-derived FX concentrate (pdFX) has been developed for use as replacement therapy in subjects with hereditary FX deficiency. AIM: This analysis assessed pdFX PK after a single 25 IU kg(-1) bolus dose in subjects with hereditary moderate or severe FX deficiency (plasma FX activity [FX:C] <5 IU dL(-1) ). METHODS: For a baseline PK assessment, blood samples were taken predose and at intervals up to 144 h (7 days) post dose. After ≥6 months of on-demand pdFX treatment and treatment of ≥1 bleed with pdFX, subjects underwent repeat PK assessment. Samples were assayed for plasma FX:C (measured using the clotting and chromogenic assays) and FX antigen. RESULTS: FX:C peaked at 0.4-0.5 h and subsequently declined over the course of 144 h with a biphasic decay curve. PK parameters observed at the baseline (n = 16) and repeat (n = 15) assessments were equivalent, therefore summary PK values were obtained by combining data from both visits (n = 31). The mean terminal half-life and incremental recovery of pdFX was 29.4 h and 2.00 IU dL(-1) per IU kg(-1) respectively. CONCLUSION: This is the most comprehensive PK study to date in subjects with hereditary FX deficiency. These results are consistent with the observed haemostatic efficacy of pdFX and provide the PK data required for the treatment of hereditary FX deficiency using pdFX replacement therapy.

Efficacy, safety and pharmacokinetics of a new high-purity factor X concentrate in subjects with hereditary factor X deficiency.

INTRODUCTION: Hereditary factor X (FX) deficiency is a rare bleeding disorder affecting 1:500 000 to 1:1 000 000 of individuals. Until recently, no specific replacement factor concentrate was available. AIM: The aim of this study was to assess safety and efficacy of a new, high-purity plasma-derived FX concentrate (pdFX) in subjects with hereditary FX deficiency. METHODS: Subjects aged ≥12 years with moderate or severe FX deficiency (plasma FX activity <5 IU dL(-1) ) received 25 IU kg(-1) pdFX as on-demand treatment or short-term prophylaxis for 6 months to 2 years. Subjects assessed pdFX efficacy for each bleed; at end-of-study, investigators assessed overall pdFX efficacy. Blood samples for pharmacokinetic analysis were obtained at baseline and ≥6 months. Safety was assessed by adverse events (AEs), inhibitor development and changes in laboratory parameters. RESULTS: Sixteen enrolled subjects (six aged 12-17 years; 10 aged 18-58 years) received a total of 468 pdFX infusions. In the 187 analysed bleeds, pdFX efficacy was categorized as excellent, good, poor or unassessable in 90.9%, 7.5%, 1.1% and 0.5% of bleeds respectively; 83% of bleeds were treated with one infusion. For pdFX, mean (median; interquartile range) incremental recovery and half-life were 2.00 (2.12; 1.79-2.37) IU dL(-1) per IU kg(-1) and 29.4 (28.6; 25.8-33.1) h respectively. No serious AEs possibly related to pdFX or evidence of FX inhibitors were observed, and no hypersensitivity reactions or clinically significant trends were detected in laboratory parameters. CONCLUSION: These results demonstrate that a dose of 25 IU kg(-1) pdFX is safe and efficacious for on-demand treatment and short-term prophylaxis in subjects with moderate or severe hereditary FX deficiency.

Experience of a new high-purity factor X concentrate in subjects with hereditary factor X deficiency undergoing surgery.

INTRODUCTION: Maintaining haemostasis in surgery is challenging for hereditary rare bleeding disorders in which multi-coagulation-factor concentrates are the only therapeutic option. Hereditary factor X (FX) deficiency affects 1:500 000 to 1:1 000 000 individuals, and no specific replacement FX concentrate has been available. A high-purity, plasma-derived FX concentrate (pdFX) has been developed for patients with hereditary FX deficiency. AIM: Our objective was to assess the safety and efficacy of pdFX in subjects with FX deficiency undergoing surgery. METHODS: Subjects with hereditary mild-to-severe FX deficiency (basal plasma FX activity [FX:C] <20 IU dL(-1) ) undergoing surgery received pdFX preoperatively to raise FX:C to 70-90 IU dL(-1) and postoperatively to maintain levels >50 IU dL(-1) until the subject was no longer at risk of bleeding due to surgery. Efficacy of pdFX was assessed by blood loss during surgery, requirement for blood transfusion, postoperative bleeding from the surgical or other sites, and changes in haemoglobin levels. Safety was assessed by adverse events (AEs), development of inhibitors, and clinically significant changes in laboratory parameters. RESULTS: Five subjects (aged 14-59 years) underwent seven surgical procedures (four major and three minor). Treatment duration was 1-15 days. For each procedure, pdFX treatment was assessed as "excellent" in preventing bleeding and achieving haemostasis. No blood transfusions were required, no AEs related to pdFX were observed, and no clinically significant trends were found in any laboratory parameters. CONCLUSION: These data demonstrate that pdFX is safe and effective as replacement therapy in five subjects with mild-to-severe FX deficiency undergoing surgery on seven occasions.

Importance of pharmacokinetic studies in the management of acquired factor X deficiency.

Up to 14% of individuals with systemic AL amyloidosis develop acquired factor X deficiency, which occurs due to adsorption of factor X onto amyloid fibrils. Although baseline factor X levels are not predictive of bleeding risk in these patients, serious hemorrhagic complications can occur, particularly during invasive procedures. Optimal management strategies to attenuate bleeding risk in these patients are unknown. We describe our experience in the management of acquired factor X deficiency, secondary to systemic AL amyloidosis, in a case series of three patients who received prothrombin complex concentrates (PCCs) for treatment and prevention of bleeding events. We performed a retrospective review extracting information on baseline demographics, laboratory data, pharmacokinetic (PK) studies, and clinically documented bleeding events. Our case series demonstrates that individuals with acquired factor X deficiency secondary to amyloidosis have variable laboratory and clinical responses to PCCs. This is likely due to distinct amyloid loads and fibril sequences, leading to different binding avidities for factor X. Our data emphasize the importance of performing PK testing prior to any invasive procedures to determine the dose and frequency interval to achieve adequate factor X levels for hemostasis, given the variable response between individuals.

Intracranial Hemorrhage as the First Manifestation of Severe Congenital Factor X Deficiency in a 20-Month-Old Male: Case Report and Review of the Literature.

Factor X deficiency (FXD) is a rare bleeding disorder, which can result in severe bleeding symptoms such as intracranial hemorrhage (ICH). The most common bleeding symptoms are epistaxis and gum bleeding. ICH is reported in 9-26% of all patients with FXD, mostly during the first month of life. Here, we present a rare case of a male presenting with ICH at the age of 20 months as the first manifestation of FXD. Secondary prophylaxis with factor X substitution once weekly prevented further bleeding.

Factor X inhibitor: a fulminant presentation and fatal course of a rare syndrome in a 59-year-old male.

Factor X inhibitors are rare. The few cases documented in the literature have occurred after viral prodromes, in association with cancer, or after exposure to antibiotics. Acquired factor X deficiencies are also rare and their etiology is largely unknown. We report a new case of a factor X inhibitor and review prior cases of both factor X inhibitors and non-amyloidosis-related acquired factor X deficiencies.

Management of Acquired Factor X Deficiency Caused by In Vitro Non-neutralizing Anti-factor X Autoantibodies with Pre-emptive Corticosteroid Therapy.

Coagulation factor X (FX) deficiency causes severe hemorrhagic symptoms. We herein report a 90-year-old man with hemorrhagic symptoms and prolongation of prothrombin time (PT) and activated partial thromboplastin time (APTT). Cross-mixing tests showed a factor deficiency pattern, but administration of plasma products was not effective. Acquired coagulation factor deficiency was suspected, and immunosuppressive therapy was started. After the intervention, his hemorrhagic symptoms improved. A decrease in FX activity was later confirmed, and anti-FX autoantibody was retrospectively detected by an enzyme-linked immunosorbent assay. Immediate intervention is important for patients suspected of having acquired coagulation factor deficiency.

Factor X deficiency and pregnancy: preconception counselling and therapeutic options.

Women with factor X deficiency (FXD) who want to become pregnant face uncertain risks to themselves and to an unborn infant from haemorrhagic complications during pregnancy and at parturition. Women with FXD may also experience difficulty achieving pregnancy secondary to haemorrhagic symptoms of the reproductive organs. Case reports describe differences in bleeding phenotypes and pregnancy outcomes that are not easily correlated with prepregnancy bleeding symptoms or factor X levels. The aim of this article is to identify factors for consideration and information to assist the physician in counselling women with FXD who want to become pregnant, and to offer guidelines for management where appropriate. We identified cases of pregnancy among women with FXD and their outcomes from the literature; 15 women with 24 pregnancies were identified and 18 were successful. The women in this small cohort did not have an increased rate of spontaneous abortion, (8.3% vs. 13.5% in the general US population) but did have a 2.5-fold increased risk of preterm labour (37.5% vs. 12.2% in the general US population). The role of prophylaxis to control reproductive haemorrhagic symptoms, including haemorrhagic complications of pregnancy has not yet been defined, but use of prophylaxis may allow more women to be able to attempt pregnancy. Women who had access to a tertiary care centre with a multidisciplinary team including an obstetrician with high-risk obstetric training, a haematologist, a perinatologist, and access to a reference laboratory and blood bank were able in most cases to successfully deliver healthy, term infants.

Efficacy of prophylaxis and genotype-phenotype correlation in patients with severe Factor X deficiency in Iran.

We aimed to evaluate the effect of regular prophylaxis with a Factor X (FX) concentrate for patients with severe FXD in Iran and to assess the correlation of the genotype and phenotype in these patients. Ten patients with severe FXD (FX activity <1%) were enrolled and characterized during 2010-2011. Prophylaxis with 20 IU FX P Behring per kg body weight was administered once a week. FX levels, were monitored at baseline, 15 and 30 min, 1, 3, 6, 12, 24, 48, 72 and 96 h after starting prophylaxis. All patients were followed for 1 year. The mean age of the patients was 15 ± 7.8 years (age range of: 6-27 years). One patient had anaphylactic reaction after the first infusion, and the treatment was stopped. During one-year follow-up after starting prophylaxis, no bleeding symptoms occurred in any patient who tolerated and remained on the prophylaxis programme and all of them had a FX level of 1% or above. The maximum level of FX activity has been observed at 15 min after starting prophylaxis. A level of 1.5-3.5% was detected after 96 h. Homozygous mutations p.Arg40Thr (Arg-1Thr), p.Gly51Arg and p.Glu69Lys were detected in patients with intracranial haemorrhage. In our patients, significant decrease in symptoms without any complication after administration of FX, was demonstrated in all except one patient who had an anaphylactic reaction. It seems that the dose of 20 IU kg(-1) could be probably the best choice for patients with severe FXD, who require regular prophylaxis.

Management of Factor X Deficiency for Vaginal Delivery in a Parturient: A Case Report.

Factor X (FX) deficiency is a rare coagulopathy that may cause bleeding complications in parturients. The literature on rotational thromboelastometry (ROTEM; Instrumentation Laboratory, Bedford, MA) to guide factor repletion and neuraxial placement during partuition is limited. We present a 17-year-old parturient with FX deficiency after vaginal delivery with neuraxial anesthesia without bleeding complications. After FX concentrate administration, thromboelastometry was utilized to risk-stratify and manage her coagulopathy peripartum. Thromboelastometry may be a valuable adjunct to conventional monitoring in patient management. A limitation of this report is that coagulation tests and thromboelastometry were not assessed at identical timepoints.

Response of factor X deficiency to darutumumab in the treatment of AL amyloidosis: a novel finding.

We report a case of progressive light-chain amyloidosis (otherwise known as AL amyloidosis) with acquired factor X (aFX) deficiency with a complete haematological response and rapid normalisation of FX levels following daratumumab monotherapy. To our knowledge, this is the first case report documenting successful treatment with daratumumab of aFX deficiency secondary to AL amyloidosis. The patient responded well to this therapy, with excellent symptomatic and quality of life improvements as well as a reduction in bleeding manifestations. This case highlights the value in considering daratumumab treatment when AL amyloidosis is complicated by FX deficiency.

Severe factor X deficiency in a twin pregnancy.

Factor X deficiency is a rare bleeding disorder inherited in an autosomal recessive fashion. In severe cases with a definitive bleeding phenotype, prophylaxis with prothrombin complex concentrate appears to prevent bleeding very effectively. Management of factor X-deficient pregnant patients continues to be a challenge. We present a new case of successful twin pregnancy in a severe factor X-deficient patient.

[A patient with AL amyloidosis and severe factor X deficiency has been in complete haematological remission with normal factor X activity for 7 years following high-dose chemotherapy. A case study and literature review]. / Pacientka s AL-amyloidózou a závazným deficitem faktoru X je po vysokodávkované chemoterapii jiz 7 let v kompletní hematologické remisi s normální aktivitou faktoru X. Popis prípadu a prehled literatury.

Disturbance of haemostasis and bleeding are rather frequent complications of AL amyloidosis. These are frequently caused by increased fragility of capillaries, thrombocyte function disorders and coagulation cascade defects. The most frequent coagulation disorder is decreased factor X activity. We describe a 34-year old female after hysterectomy for myomatous uterus and metrorhagia. Before the surgery, the attending physicians did not identify any pathological changes suggesting a need for further investigations or presence of AL amyloidosis. Post-surgery development was complicated by life-threatening diffuse haemorrhage. Extended investigations of coagulation cascade revealed reduction of factor X activity to 16%. Targeted histological examination of the resected uterus confirmed AL amyloid deposits consisting of kappa chains. The patient's bone marrow contained certain small level of multiplied kappa chains-expressing plasma cells (< 10%); monoclonal immunoglobulins IgG K and free kappa chains were identified in serum. At that time, the patient did not satisfy the then valid Durie-Salmon criteria for multiple myeloma and thus the patient was diagnosed with primary systemic AL amyloidosis. The patient's condition gradually improved following substitution therapy (Prothromplex, fresh frozen plasma and erythrocyte transfusion) and bleeding slowly ceased so that chemotherapy with VAD (vincristine, adriamycin and dexamethasone) was initiated 6 weeks after the surgery. A total of 8 chemotherapy cycles were administered and complete haematological remission was achieved after the 5th cycle. Administration of the 8 VAD chemotherapy cycles resulted in increased factor X activity; bleeding complications subsided completely, thereby decreasing the risk of life-threatening mucositis-associated haemorrhage. Consequently, tandem high-dose chemotherapy (melphalan 100 mg/m2) with autologous haematopoietic stem cells transplantation was added to the treatment plan. Treatment was completed at the beginning of 2003 and, from that time, the patient is on continuous maintenance therapy with interferon alpha. Seven years from the diagnosis and 6 years from the completion of treatment the patient is in complete haematological remission, with no signs of organic damage caused by AL amyloid and with normal factor X activity. Factor X activity increased at the time when complete haematological remission was achieved after 8 cycles of VAD chemotherapy to 42%, it reached 68% the second year following high-dose chemotherapy, 77% after 5 years and 85% after 7 years. We had considered administration of high-dose chemotherapy in the standard regimen, i.e. following 4 cycles of VAD chemotherapy, as too high risk in the described young female patient. Therefore, we administered 8 cycles of conventional chemotherapy and only after complete haematological remission and partial organ response (factor X activity increased to 42%) were achieved, we added tandem high-dose chemotherapy to the treatment. We thus achieved long-term (7-years so far) complete haematological and organ remission. Increase in factor X activity is explicit over the entire 7-year observational period. We recommend starting treatment of high-risk transplant patients with AL amyloidosis with traditional chemotherapy regimen and, in case of positive haematological and organ treatment response, we recommend re-examination of potential benefits and risks of high-dose chemotherapy with autologous transplantation.

Use of plasma-derived factor X concentrate in neonates and infants with congenital factor X deficiency.

BACKGROUND: Congenital factor X deficiency (FXD) is a rare bleeding disorder that often presents with severe bleeding in the neonatal period. Long-term prophylaxis with infusions of FX-containing products is recommended in patients with FXD and a personal or family history of severe bleeding. A plasma-derived FX concentrate (pdFX) is approved for on-demand and prophylactic therapy in adults and children with FXD. The safety and efficacy of pdFX has been demonstrated in patients <12 years of age, yet limited data exist regarding its use in infants. PATIENTS/METHODS: This retrospective case series details clinical experience using pdFX in four neonates with moderate and severe FXD across four institutions. RESULTS AND CONCLUSIONS: All four patients presented in the first week of life with severe bleeding. Following treatment of the acute bleed, prophylactic pdFX was initiated at an average of 29 days of life and a dose of 69 IU/kg every 48 hours. Incremental recovery (IR) in three infants averaged 1.42 IU/dL per IU/kg (min-max: 1.06-1.67 IU/dL per IU/kg). One patient experienced thrombotic complications in the setting of sepsis. After a median follow-up of 26.5 months, no patient has experienced breakthrough bleeding episodes. Our study supports the use of pdFX in neonates and infants and suggests that higher pdFX dosing of 70 to 80 IU/kg every 48 hours based on the smallest available vial size is feasible. Because of variability in IR, close monitoring of FX activity should be used to guide dosing in this age group.

Genetic analysis of a compound heterozygous patient with congenital factor X deficiency and regular replacement therapy with a prothrombin complex concentrate.

Congenital factor X (FX) deficiency is a rare bleeding disorder with an incidence of one in one million. The proband, a 2-year-old girl, exhibited easy bruising and a history of umbilical cord bleeding at birth. Prothrombin time (> 40 s) and activated partial thromboplastin time (65.0 s) were prolonged. Marked declines in FX activity (< 1%) and FX antigen levels (5%) were also observed. Genetic analysis of the proband identified two types of single-base substitutions, c.353G>A (p.Gly118Asp) and c.1303G>A (p.Gly435Ser), indicating compound heterozygous congenital FX deficiency. Genetic analysis of family members revealed that her father and older sister (5-year-old) were also heterozygous for p.Gly118Asp, and that her mother was heterozygous for p.Gly435Ser. To improve the bleeding tendency, the proband received regular replacement of 500 units of PPSB-HT, a prothrombin complex concentrate (PCC). Following continued regular replacement of 500 units of PPSB-HT once per week, the proband has exhibited no bleeding tendencies and no new bruises have been observed. There are no previous report of the use of PPSB-HT for regular FX replacement. Regular replacement therapy with PPSB-HT may be an effective method for preventative control of bleeding tendencies in FX deficiency.