scholarly journals Thein Vitroprocoagulant Effects of Standard and Extended Half-Life Recombinant Factor IX Concentrates in Patients on Prophylaxis with Emicizumab

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 18-19
Author(s):  
Elena G Arias-Salgado ◽  
Ihosvany Fernandez-Bello ◽  
Elena Monzón Manzano ◽  
Paula Acuña ◽  
Sara García Barcenilla ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Alternative Treatment ◽  
Half Life ◽  
Research Funding ◽  
Factor Ix ◽  
University Hospital ◽  
Limiting Factor ◽  
Chromogenic Substrate ◽  
Low Concentration ◽  
Procoagulant Effect

Introduction: Emicizumab is a humanized, monoclonal, bispecific antibody that binds factor (F) FX and FIXa allowing thrombin generation in the absence of FVIII, which is used for routine treatment of patients with Hemophilia A (HA) with and without inhibitors. Plasma level of FIX will be an important limiting factor for the formation of the FX-FIXa-emicizumab ternary complex in the absence of FVIII, suggesting the potential use of FIX concentrates to regulate the procoagulant function of emicizumab and therefore, to use it as an alternative treatment in certain circumstances to stop or prevent bleedings in patients on prophylaxis with emicizumab. At the present time there are several recombinant FIX concentrates with differences in their content of activated FIX (FIXa) and in their half-life (standard or extended) that may differ in their procoagulant effects when combined with emicizumab. Aim: The aim of this study was to evaluate if there were differences in thein vitroprocoagulant effects of two recombinant FIX concentrates, one with standard half-life (rFIX Nonacog Alfa, BeneFIX®, Pfizer) and the other with extended half-life (rFIX fused to rAlbumin, Albutrepenonacog Alfa, Idelvion®, CLS Behring) in samples from patients on prophylaxis with Emicizumab. Methods: This is a prospective and transversal pilot study that was approved by the Ethics Committee from La Paz University Hospital. Two patients with haemophilia A (HA) with inhibitors in prophylaxis with emicizumab were recruited and one haemophilia B (HB) patient was included as a control for the effects of FIX. Blood samples were collected in tubes with corn trypsin inhibitor (CTI, Haematologic Technologies, USA), to block thecontact phase and to only evaluate coagulation mediated by the extrinsic pathway. Levels of FIXa in concentrates of FIX were quantified using the Spectrozyme® FIXa chromogenic substrate (LOXO) and measuring the increase in OD at 405 nm. Rotational thromboelastometry (ROTEM) was performed using whole blood activated by a low concentration of tissue factor solution (final dilution 1:50,000 of EXTEM reagent) plus recalcification. Parameters evaluated in ROTEM were CT (cloting time), defined as time until detection of a clot firmness of 2 mm; and CFT (clot formation time), defined as time between detection of a clot firmness from 2 to 20 mm. Calibrated automated thrombogram (CAT)was performed using platelet free plasma (PFP) activated by low concentration of tissue factor plus phospholipids (PPP-Reagent LOW®, Stago). Parameters evaluated in CAT were: Peak, defined as maximum thrombin concentration reached, in nM; and ETP, defined as the total amount of thrombin generated over time, in nMxmin. Results: The presence of FIXa activity assayed by a chromogenic substrate was not detectable with 20 IU of Idelvion while BeneFIX® showed a specific concentration-dependent FIX activity that was blocked with the serine protease inhibitor EGR-chloromethylketone (Figure 1). ROTEM (Figure 2) and CAT (Figure 3) results showed that the addition of increased concentrations of both concentrates of rFIX produces an enhanced procoagulant effect of Emicizumab similar to the effect produced by the addition of the bypassing agent rFVIIa (NovoSeven®, NovoNordisk). These results also showed that it is necessary three-four times higher concentration (U/dl) of Idelvion® to get similar procoagulant effects that those obtained with BeneFIX®. The higher procoagulant effects of BeneFIX® were also observed in samples of a patient with severe HB. Conclusion: Global coagulation assays suggest that increasing endogenous FIX levels with two rFIX concentrates that have different FIXa content and half-life, produce an enhanced procoagulant effect of Emicizumab opening the idea of the use of these concentrates as an alternative treatment for bleedings in patients with inhibitors on prophylaxis with Emicizumab. Further studies need to be performed to evaluate the procoagulant activity of the concomitant use of different rFIX concentrates and Emicizumab, and to assess security of this therapeutic approach. This work was supported by grants from FIS-FONDOS FEDER (PI19/00631 and P19/00772). EMM holds a predoctoral fellowship from Fundación Española de Trombosis y Hemostasia (FETH-SETH). Disclosures Fernandez-Bello: Novartis:Speakers Bureau;Stago:Speakers Bureau;Takeda:Research Funding, Speakers Bureau;NovoNordisk:Current Employment, Research Funding, Speakers Bureau;Roche:Speakers Bureau;SOBI,:Research Funding;Pfizer:Speakers Bureau.García Barcenilla:Pfizer,:Speakers Bureau;Takeda:Research Funding, Speakers Bureau;Roche:Speakers Bureau;Bayer:Speakers Bureau;Novartis:Speakers Bureau;NovoNordisk:Research Funding, Speakers Bureau.Alvarez Román:Roche:Speakers Bureau;Novartis:Speakers Bureau;Takeda:Research Funding, Speakers Bureau;Pfizer,:Research Funding, Speakers Bureau;Bayer:Consultancy;SOBI,:Consultancy, Research Funding, Speakers Bureau;Grifols:Research Funding;NovoNordisk,:Research Funding, Speakers Bureau.Martín:NovoNordisk:Speakers Bureau;SOBI:Research Funding;Pfizer:Research Funding, Speakers Bureau;Roche:Speakers Bureau;Novartis:Speakers Bureau.Rivas Pollmar:Novartis:Speakers Bureau;Roche:Speakers Bureau;Pfizer:Speakers Bureau.Canales:Roche:Honoraria;Celgene:Honoraria;Roche:Honoraria;Janssen:Honoraria;Novartis:Honoraria;Sandoz:Speakers Bureau;Sandoz:Honoraria;Janssen:Speakers Bureau;iQone:Honoraria;Sandoz:Honoraria;Gilead:Honoraria;Takeda:Speakers Bureau;Novartis:Honoraria;Karyopharm:Honoraria;Janssen:Honoraria;Takeda:Speakers Bureau;Janssen:Speakers Bureau;Roche:Speakers Bureau;Sandoz:Speakers Bureau;Roche:Speakers Bureau;Karyopharm:Honoraria.Butta:Grifols:Research Funding;Novartis:Speakers Bureau;ROCHE:Research Funding, Speakers Bureau;Pfizer:Speakers Bureau;SOBI:Speakers Bureau;Takeda:Research Funding, Speakers Bureau;NovoNordisk:Speakers Bureau.Jimenez-Yuste:F. Hoffman-La Roche Ltd, Novo Nordisk, Takeda, Sobi, Pfizer, Grifols, Octapharma, CSL Behring, Bayer:Honoraria;F. Hoffman-La Roche Ltd, Novo Nordisk, Takeda, Sobi, Pfizer:Consultancy;Grifols, Novo Nordisk, Takeda, Sobi, Pfizer:Research Funding.

scholarly journals Evaluation of the in Vitro Procoagulant Effect of Factor IX Concentrates in Patients on Prophylaxis with Emicizumab

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1118-1118
Author(s):  
Ihosvany Fernandez-Bello ◽  
María Teresa Alvarez Román ◽  
Mónica Martín ◽  
María Isabel Rivas Pollmar ◽  
Sara García Barcenilla ◽  
...  
Keyword(s):  
Plasma Levels ◽  
Research Funding ◽  
Thrombin Generation ◽  
Standard Dose ◽  
Venous Access ◽  
Factor Ix ◽  
Limiting Factor ◽  
Procoagulant Effect ◽  
Bypassing Agents

Introduction: The incidence of bleeding in patients with severe (S) haemophilia A (HA) on prophylaxis with emicizumab is similar to that seen in patients with moderate-mild HA, therefore these patients will require administration of factor (F) VIII concentrates (patients without inhibitors) or bypassing agents (patients with inhibitors) in case of acute bleeding or surgery. In the absence of FVIII, thrombin generation is guided by the FIX plasma levels that becomes the limiting factor for the formation of the FX-FIXa-emicizumab ternary complex. We hypothesize that the increment of level of FIX in patients on prophylaxis with emicizumab would increase their procoagulant function. Objectives: To measure the in vitro procoagulant effect of increasing factor IX activity in patients on prophylaxis with emicizumab. Material and Methods: We performed a study in 6 patients on prophylaxis with emicizumab (2 patients with inhibitors) and 20 healthy controls. We evaluated the in vitro procoagulant effect of therapeutic concentrations of recombinant activated FVII (rFVIIa), activated prothrombin complex concentrate (aPCC) and several concentrations of FIX using global assays as thrombin generation test (CAT) and thromboelastometry (ROTEM). Results: In correspondence with our hypothesis, our ROTEM results indicated that increasing concentration of FIX up to 110% was able to normalize the procoagulant capacity of all patients. Further increment of in vitro FIX concentrations up to 125% had a procoagulant effect similar to what would be obtained after one standard dose of 90 mcg/kg rFVIIa. In regard to aPCC, we needed to increase FIX levels up to 200 IU/dl to achieve a procoagulant effect similar to what would be obtained with a dose of 2.5 IU/kg of aPCC. CAT showed total normalization of thrombin generation in all patients with levels of 125 IU/dl of FIX which support the idea of normalization of procoagulant function of patients on prophylaxis with emicizumab in response to low increments of FIX. Moreover, similar to ROTEM, 200 IU/dl of FIX had comparable procoagulant effect to concentrations of aPCC that would be obtained after one dose of 2.5 IU/kg aPCC. With these results we might speculate on a possible good safety profile of this high level of FIX in patients on prophylaxis with emicizumab if we take into account that 2.5 IU/kg aPCC is 20 times lower than aPCC dose [50 IU/kg] used in HAVEN-1 with no associated incidence of thrombotic events, however, more studies are needed to explore this hypothesis. Conclusions: In vitro increment of FIX plasma levels enhances in vitro procoagulant function of patients on prophylaxis with emicizumab opening the idea of an alternative hemostatic treatment in this type of patient. The use of FIX concentrates with much longer half-life compared to FVIII concentrates or bypassing agents in patient on prophylaxis with emicizumab might produce longer period of time with a normalized haemostatic function which might speed up the recovery, might reduce the incidence of bleeding complication and would require much less number of administrations, this later of paramount importance in patients with limited venous access. However, more studies should be addressed to confirm these results. Moreover, and even more important, prothrombotic risk of combinatory therapy with FIX and emicizumab should be carefully studied in pre-clinical studies. NB holds a tenure track grant from FIS-FONDOS FEDER (CP14/00024). Disclosures Fernandez-Bello: Novartis, Pfizer, ROCHE, Stago: Speakers Bureau. Alvarez Román:Novartis: Speakers Bureau; Novo Nordisk: Speakers Bureau; Bayer: Speakers Bureau; CSL Behring: Speakers Bureau; Roche: Speakers Bureau; Sobi: Speakers Bureau; Amgen: Speakers Bureau; Shire (Takeda): Research Funding, Speakers Bureau. Martín:Novartis, Pfizer, ROCHE, Novo Nordisk: Speakers Bureau; SOBI: Research Funding. Rivas Pollmar:Novartis, Pfizer, ROCHE, Novo Nordisk: Speakers Bureau; SOBI: Research Funding. García Barcenilla:SOBI: Research Funding; Bayer, Pfizer, Takeda, Novartis: Speakers Bureau. Canales:Sandoz: Honoraria; Gilead: Honoraria; Karyopharm: Honoraria; Janssen: Honoraria, Speakers Bureau; Takeda: Speakers Bureau; SOBI: Research Funding; Celgene: Honoraria; iQone: Honoraria; F. Hoffmann-La Roche Ltd: Honoraria, Speakers Bureau; Novartis: Honoraria. Butta:Novartis: Consultancy; Roche, Pfizer: Speakers Bureau. Jimenez-Yuste:Bayer, CSL Behring, Grifols, Novo Nordisk, Octapharma, Pfizer, Roche, Sobi, Shire: Consultancy, Honoraria, Other: reimbursement for attending symposia/congresses , Research Funding, Speakers Bureau.

scholarly journals Extended Half-Life Factor VIII/Factor IX Products: Assay Discrepancies and Implications for Hemophilia Management

2020 ◽  
Vol 40 (S 01) ◽  
pp. S15-S20
Author(s):  
Jens Müller ◽  
Georg Goldmann ◽  
Natascha Marquardt ◽  
Bernd Pötzsch ◽  
Johannes Oldenburg
Keyword(s):  
Factor Viii ◽  
Half Life ◽  
In Vitro Study ◽  
Factor Ix ◽  
University Hospital ◽  
Spiked Plasma ◽  
Structural Differences ◽  
The University ◽  
Life Factor

AbstractDue to structural differences between extended half-life (EHL) factor VIII (FVIII) or FIX products and equivalent plasma wild-type molecules used for assay calibration, reagent-dependent discrepancies during monitoring of FVIII- and FIX-replacement therapies with EHL products have been described. To assess the performance of available one-stage clotting and chromogenic substrate assays on the Siemens Atellica COAG 360 analyzer, an in vitro study using spiked plasma samples was performed. The described results confirm previously described findings and allowed allocation of each EHL product to an appropriate assay. In addition, corresponding EHL product–specific analytes were defined within the order entry system of the University Hospital Bonn. The requirement of product-specific FVIII and FIX assays complicates patient monitoring and demonstrates the need for both continuous education and communication between treating physicians and the coagulation laboratory.

Effect Of Combined Heparin- and Antithrombin-Binding Exosite Mutations On Human Factor IX(a) Coagulant Activity, Thrombin Generation, and Protease Half-Life In Human Plasma

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2333-2333
Author(s):  
Pamela R. Westmark ◽  
Pansakorn Tanratana ◽  
John P. Sheehan
Keyword(s):  
Human Plasma ◽  
Half Life ◽  
Research Funding ◽  
Thrombin Generation ◽  
Human Factor ◽  
Factor Ix ◽  
Hemophilia B ◽  
Coagulant Activity ◽  
Plasma Half Life

Abstract Introduction Hemophilia B is an X-linked genetic disorder characterized by defective factor IX activity. Recombinant factor IX (rFIX) is employed as protein replacement for the treatment and prophylaxis of bleeding episodes. Antithrombin is the primary plasma inhibitor of activated factor IX (FIXa), and inhibition is enhanced by heparin/heparan sulfate. We hypothesize that selective disruption of protease interactions with heparin and antithrombin via mutations in the respective heparin- and antithrombin-binding exosites may enhance rFIX(a) efficacy by prolonging protease half-life in vivo. Aim To assess the effect of mutations in the FIX(a) heparin- and antithrombin-binding exosites on traditional coagulant activity, thrombin generation, and protease half-life in human plasma. Methods Human FIX cDNA constructs with alanine substitutions (chymotrypsinogen numbering) in the heparin exosite (K126A, K132A, K126A/K132A), antithrombin exosite (R150A), or both (K126A/R150A, K132A/R150A, K126A/K132A/R150A) were expressed in HEK293 cell lines. Recombinant zymogens were purified from conditioned media, and a portion activated to protease with human factor XIa. Zymogen and protease forms were characterized in APTT-based clotting assays, and tissue factor (TF) and FIXa-initiated thrombin generation (TG) assays in pooled human FIX-deficient plasma, respectively. Comparisons were made with human plasma-derived factor IX (pFIX) and recombinant FIX wild type (WT). Protease half-life in pooled, citrated human plasma was determined using a novel assay that detects FIXa activity by TG response. Results Zymogen coagulant activities (% WT ± S.E) were: pFIX 105.2 ± 2.8, WT 100 ± 7.1, K132A/R150A 75.8 ± 3.4, K126A 63.3 ± 2.3, R150A 62.4 ± 4.0, K132A 30.9 ± 1.0, K126A/R150A 27.0 ± 2.1, K126A/K132A 20.6 ± 9.2, and K126A/K132A/R150A 7.3 ± 3.8. Similarly, protease coagulant activities were: WT 100 ± 6.1, pFIXa 98.4 ± 11.4, K132A 91.4 ± 1.6, K132A/R150A 84.9 ± 2.8, R150A 77.1 ± 5.8, K126A 39.5 ± 2.4, K126A/R150A 25.3 ± 2.8, K126A/K132A/R150A 10.9 ± 0.6, and K126A/K132A 9.3 ± 0.6. In contrast to their relative coagulant activities, FIX K126A (1.9-fold), R150 (1.6-fold), and K132A/R150A (1.3-fold) supported increased peak thrombin concentrations during TF-triggered TG; pFIX, FIX K132A and K126A/R150A were similar to WT; and FIX K126A/K132A/R150A (0.6-fold) and K126A/K132A (0.2-fold) demonstrated marked reductions in peak thrombin relative to WT. In the FIXa-initiated TG assay, FIXa K126A/R150A and K132A/R150A (1.5-fold) demonstrated significantly increased peak thrombin concentrations; pFIXa, FIXa K132A, R150A, and K126A (0.8-1.0 fold) were similar to WT; while FIXa K126A/K132A and K126A/K132A/R150A demonstrated markedly reduced (0.2-0.3 fold) and delayed peak thrombin concentrations. In pooled, citrated FIX-deficient plasma, FIXa WT (40.9 ± 1.4 min) and K126A/K132A (37.2 ± 0.7 min) demonstrated similar half-lives, while FIXa R150A, K126A/R150A, and K132A/R150A all had half-lives > 2 hr. Conclusions Single exosite mutations resulted in mild to moderate reductions in coagulant activity, while the double mutation in the heparin exosite (K126A/K132A) markedly reduced activity, likely due to a synergistic effect on cofactor binding. Traditional coagulant activity did not accurately represent the ability of the mutant proteins to support thrombin generation. Despite variable reductions in coagulant activity, FIX K126A, K132A, R150A, K126A/R150A and K132A/R150A supported levels of plasma thrombin generation that were equal to or greater than FIX WT. The plasma half-life of FIXa WT activity was remarkably lengthy, and while mutations in the heparin exosite had negligible effects, R150A in the antithrombin exosite substantially increased protease half-life, consistent with a primary role for antithrombin in the plasma inhibition of FIXa. Thus, single exosite mutations did not significantly disrupt the procoagulant function of human FIX(a), and combined exosite mutations (K126A/R150A and K132A/R150A) maintain or enhance plasma thrombin generation while disrupting exosite-mediated regulatory mechanisms. The combination of intact procoagulant function with disruption of antithrombin- and heparin-mediated regulation of FIX(a) will potentially enhance in vivo recovery, prolong plasma half-life, and enhance the efficacy of hemophilia B replacement therapy. Disclosures: Sheehan: Novo Nordisk Access to Insight Basic Research Grant: Research Funding; Bayer Hemophilia Awards Program: Research Funding; Diagnostica Stago: reagents, reagents Other.

scholarly journals Real Life Experience in Clinical Practice with Recombinant Coagulation FVIII-Fc Fusion Protein

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 4929-4929
Author(s):  
Teresa Álvarez Roman ◽  
Elena Monzón Manzano ◽  
Ihosvany Fernandez-Bello ◽  
Mónica Martín ◽  
María Isabel Rivas Pollmar ◽  
...  
Keyword(s):  
Half Life ◽  
Research Funding ◽  
Hemophilia A ◽  
Trough Level ◽  
Real Life ◽  
University Hospital ◽  
Severe Hemophilia ◽  
Median Dose ◽  
La Paz ◽  
Before And After

Introduction: Efmoroctocog alfa (Elocta®) is a recombinant coagulation FVIII-Fc (rFVIIIFc), a fully recombinant fusion protein produced in human embryonic kidney cells, with an extended half-life used for the treatment and prevention of bleeding in patients with severe hemophilia A. Using rFVIIIFc for the treatment of severe hemophilia A patients received the approval of reimbursement in Spain at the end of 2016. Therefore, there are no many comparative data published about real life use of rFVIIIFc. Objective: This work aims to describe characteristics of the treatment of severe hemophilia A patients with rFVIIIFc and to compare its results with those previously obtained employing other FVIII products. Methods: This was an open-label non-interventional retrospective study reviewing patient characteristics and treatment outcomes before and after the use of rFVIIIFc. The La Paz University Hospital Ethics Committee approved the experimental protocol. Patients with severe hemophilia A without inhibitors being treated with rFVIIIFc since at least six months before study approval by Ethics Committee were included. The following data were collected for patients included in the study: dose (IU/kg) and prophylaxis treatment regimen, number of spontaneous and traumatic bleedings, annual bleeding rate (ABR) and FVIII trough level. The statistical analysis on the variables listed above comparing before and after rFVIIIFc usage was performed by the Biostatistics Unit of La Paz University Hospital with the statistical package SPSS v.18.0 (SPSS Inc., Chicago, IL, USA). Results: Twenty two severe hemophilia A patients (median age: 20 years old, ranging from 6 to 63 years) on prophylaxis with rFVIIIFc were considered to be included in this study, but two were excluded due to lack of data. Median follow-up period was 14 months (ranging from 6 to 28 months). Nineteen severe hemophilia A patients have been previously treated with rFVIII (two of them with other extended half-life product) and one with plasma-derived FVIII. Eight of the ten severe hemophilia A patients who presented an ABR greater than 0 with previous treatments reduced their ABR when treated with rFVIIIFc (Table 1). Among those patients with an ABR=0 with previously used FVIII products, only one increased to an ABR=1 when treated with Elocta® due to a traumatic bleeding. Table 1 shows ABR across all patients before and after rFVIIIFc. There was no difference in dose per injection between other FVIII products and rFVIIIFc (median dose for patients treated with other FVIII products: 46.0 IU/kg, ranging from 26 to 65 IU/kg; median dose for patients treated with rFVIIIFc: 46.5 IU/kg, ranging from 26 to 65 IU/kg). Nevertheless, a reduction was observed in administration frequency. Among the twelve patients who received treatment with other FVIII products every 48 hours, eleven came to receive rFVIIIFc 3 times a week and the one previously receiving a plasma-derived FVIII, to twice a week. Five of the patients receiving treatment 3 times a week reduced its frequency to twice per week. Three patients maintained the same schedule of administration. To note, one of the two patients receiving another prolonged half-life product maintained the schedule of treatment and the other reduced its frequency from every 48 hours to 3 times a week. FVIII trough level in plasma (% of FVIII), expressed as median (25th-75th percentile), was 1.1 (0.1-4.0) for rFVIIIFc treatment and 0.2 (0.0-1.9) for other FVIII products (p=0.06). Conclusions: 85% of the severe hemophilia A patients from our cohort reduced the weekly dose administration after beginning treatment with rFVIIIFc. Most of the patients increased plasma trough level of FVIII with rFVIIIFc. 45% of patients reduced and 40% kept their ABR=0 when they changed rFVIIIFc. These data suggest that treatment with rFVIIIFc gives a higher protection to severe hemophilia A patients. However, further research with larger sample size is required to investigate this. This work was supported by SOBI. NB holds a tenure track grant from FIS-FONDOS FEDER (CP14/00024). Disclosures Álvarez Roman: Takeda: Research Funding; Amgen: Consultancy, Speakers Bureau; NovoNordisk: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Bayer: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; Roche: Consultancy, Speakers Bureau; CSL Behring: Consultancy, Speakers Bureau; Sobi: Consultancy, Speakers Bureau. Fernandez-Bello:Novartis, Pfizer, ROCHE, Stago: Speakers Bureau. Martín:SOBI: Research Funding; Novartis, Pfizer, ROCHE, Novo Nordisk: Speakers Bureau. Rivas Pollmar:Novartis, Pfizer, ROCHE, Novo Nordisk: Speakers Bureau; SOBI: Research Funding. García Barcenilla:Bayer, Pfizer, Takeda, Novartis: Speakers Bureau; SOBI: Research Funding. Canales:SOBI: Research Funding; iQone: Honoraria; Karyopharm: Honoraria; Novartis: Honoraria; Takeda: Speakers Bureau; Gilead: Honoraria; Celgene: Honoraria; Janssen: Honoraria, Speakers Bureau; F. Hoffmann-La Roche Ltd: Honoraria, Speakers Bureau; Sandoz: Honoraria. Butta:Roche, Pfizer: Speakers Bureau; Novartis: Consultancy. Jimenez-Yuste:Bayer, CSL Behring, Grifols, Novo Nordisk, Octapharma, Pfizer, Roche, Sobi, Shire: Consultancy, Honoraria, Other: reimbursement for attending symposia/congresses , Research Funding, Speakers Bureau.

IB1001, an Investigational Recombinant Factor IX, Pharmacokinetics in Pediatric Patients with Hemophilia B.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2225-2225
Author(s):  
Edward D. Gomperts ◽  
Shashikant Apte ◽  
Utpal Chaudhuri ◽  
Joseph M John ◽  
Vijay Ramanan ◽  
...  
Keyword(s):  
Half Life ◽  
Research Funding ◽  
Pediatric Patients ◽  
Robust Regression ◽  
Factor Ix ◽  
Hemophilia B ◽  
Maximum Plasma ◽  
Recombinant Factor Ix ◽  
In Vivo Recovery

Abstract Abstract 2225 Introduction IB1001 is a recombinant factor IX product being investigated for the treatment and prevention of bleeding in individuals with hemophilia B. Pharmacokinetics (PK) in adults (>12 years) demonstrated that IB1001 had results similar to the currently available recombinant FIX with respect to parameters such as terminal phase half-life and incremental recovery. We report the interim findings from a PK assessment in children <12 years, with severe hemophilia B (FIX <2%), >50 prior exposure days to FIX, and no history of or currently detectable inhibitor to FIX. Methods Non-randomized, open-label PK study with patients receiving 75±5 IU/kg of IB1001 following a washout period of ≥4 days from a previous FIX infusion. Factor IX levels were determined pre-infusion and at 15–30 minutes, 4–6, 24–26, and 68–72 hours post-infusion. Additional samples could be drawn at 1–3 and 10–14 hours. Calculated PK parameters were: half-life (β-phase t1/2, determined using a robust regression approach [Lee ML et al. XVIth ISTH Congress, Florence, Italy, 1997]) but generally assuming a single compartmental model because of the small number of points, maximum plasma concentration (Cmax), in vivo recovery (IVR) and AUC(0-∞) (determined by the trapezoidal rule). In addition, the AUC(0-t) and mean residence time (MRT) were calculated. Results When compared to the findings previously reported with IB1001 in adult (≥12 years of age) subjects (Martinowitz U et al. Haemophilia, 18, 2012), the results in pediatric patients demonstrate a more rapid metabolism of factor IX as is indicated by the shorter terminal half-life (mean±SD of 19.3±7.8 h versus 29.6±18.2 h in adults) and the smaller AUC0-∞ (mean±SD of 1059±264 versus 1668±598 in adults). In addition, the in vivo recovery was lower (mean±SD of 0.69±0.21) versus that seen in adults (mean±SD of 0.98±0.22). These results are similar to those reported by Berntorp et al (Haemophilia, 7, 2001) with nonacog alfa. Conclusions The pharmacokinetics of IB1001 has previously been shown to be non-inferior to nonacog alfa, another recombinant factor IX, in hemophilia B individuals >12 years of age. The current study is intended to provide information on children <12 and, particularly, <6 years of age. IB1001 is metabolized faster and has a lower recovery than the comparable findings in patients >12 years of age. Although the study is ongoing, these may represent important implications for the potential use of IB1001 in pediatric patients. Disclosures: Gomperts: Inspiration Biopharmaceuticals Inc: Consultancy. Apte:Inspiration Biopharmacauticals Inc: Research Funding. Chaudhuri:Inspiration Biopharmaceuticals Inc: Research Funding. John:Inspiration Biopharmaceuticals Inc: Research Funding. Ramanan:Inspiration Biopharmaceuticals Inc: Research Funding. Liesner:Inspiration Biopharmaceuticals Inc: Research Funding. Shapiro:Inspiration Biopharmaceuticals Inc: Honoraria, Research Funding. Mills:Inspiration Biopharmaceuticals Inc: Employment. Lee:Inspiration Biopharmaceuticals Inc: Employment.

Pharmacokinetics Of Recombinant Factor IX Fc Fusion Protein (rFIXFc) In Pediatric Subjects With Hemophilia B: An Interim Analysis Of The Kids B-LONG Study

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3599-3599
Author(s):  
Kathelijn Fischer ◽  
Roshni Kulkarni ◽  
Myles Bradbury ◽  
Margaret V. Ragni ◽  
Savita Rangarajan ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Half Life ◽  
Interim Analysis ◽  
Research Funding ◽  
Factor Ix ◽  
Hemophilia B ◽  
Employment Equity ◽  
Advisory Committees ◽  
Age Cohorts ◽  
Equity Ownership

Abstract Introduction Prophylaxis with factor IX (FIX) is the optimal treatment for patients with hemophilia B; however, due to the short half-life of currently available FIX products, frequent injections may be required to prevent bleeding episodes. To prolong half-life and reduce injection frequency, a long-acting recombinant FIX Fc fusion protein (rFIXFc) consisting of one rFIX molecule covalently linked to the Fc domain of immunoglobulin G1 (IgG1) was developed. In a phase 3 study in adults and adolescents, rFIXFc had a 2.43-fold increase in half-life and 50% reduction in clearance (CL) compared with FIX (BeneFIX®) (J Thromb Haemost. 2013;11[2]:241). The Kids B-LONG study (NCT01440946) was designed to evaluate the pharmacokinetics (PK), safety, and efficacy of rFIXFc prophylaxis in previously treated pediatric subjects with hemophilia B. The objective of this planned interim analysis was to determine the PK parameters of rFIXFc in subjects enrolled in Kids B-LONG and compare these parameters to their pre-study FIX PK parameters. Methods This multicenter, open-label, phase 3 study is currently enrolling previously treated subjects aged<12 years with severe hemophilia B (≤2 IU/dL endogenous FIX), at least 50 exposure days (EDs) to FIX products, and no inhibitors to FIX. Subjects are stratified into two age cohorts (<6 and 6 to<12 years of age). A weekly prophylactic regimen of 50-60 IU/kg of rFIXFc is administered to all subjects, with subsequent dose and interval adjustments based upon PK data and bleeding frequency. Subjects will continue treatment until they achieve 50 EDs. The primary endpoint is the incidence of inhibitor formation. A sequential PK analysis is performed to compare the PK parameters of rFIXFc with that of pre-study FIX products. PK sampling of pre-study FIX occurs at baseline prior to first dose of FIX (50 IU/kg) and at 5 additional time points through 48 hours. PK sampling of rFIXFc occurs prior to first dose of 50 IU/kg rFIXFc and at 7 additional time points through 168 hours following the first dose; a washout period of 96 hours is required before the first dose of both pre-study FIX and rFIXFc. Plasma FIX activity is measured using the one-stage clotting assay calibrated against a commercially available FIX plasma standard and the FIX activity-over-time profiles are analyzed by non-compartmental analysis (NCA) using the PK data analysis software Phoenix™ WinNonlin 6.2.1.51. A data cut-off date of 23 April 2013 was used to report PK data in this interim analysis. Results At the time of this interim analysis, 24 subjects were enrolled and had received at least one dose of pre-study FIX and/or rFIXFc. Of 18 subjects with evaluable PK profiles, 15 had complete PK profiles for both pre-study FIX (BeneFIX®, Haemosolvex®, or Alphanine®) and rFIXFc. A comparison of PK parameters for rFIXFc versus FIX for both age cohorts is presented in Table 1. rFIXFc had a more than 3-fold prolongation in half-life and a more than 60% reduction in CL compared to the FIX products. Conclusion In comparison to currently available FIX products, rFIXFc had a prolonged half-life and reduced CL in pediatric subjects, which was similar to previous observations in adults and adolescents. The final analysis of the Kids B-LONG study will provide further PK information and evaluate the safety and efficacy of rFIXFc in children. Disclosures: Fischer: Biogen Idec, Baxter, Novo Nordisk, Bayer: Membership on an entity’s Board of Directors or advisory committees; Baxter, Bayer, Novo Nordisk, Pfizer: Research Funding. Kulkarni:Biogen Idec, Novo Nordisk, Baxter : Membership on an entity’s Board of Directors or advisory committees. Ragni:Biogen Idec: Membership on an entity’s Board of Directors or advisory committees; Bristol Myers Squibb, Smith Kline Glaxo, Tacere Benitec: Consultancy; Baxter, Bayer, Biogen Idec, Bristol Myers Squibb, CSL Behring, Merck, Novo Nordisk, Pfizer, Smith Kline Glaxo: Research Funding. Rangarajan:Baxter, Pfizer: Research Funding; Biogen Idec : Membership on an entity’s Board of Directors or advisory committees. Dong:Biogen Idec: Employment, Equity Ownership. Li:Biogen Idec: Employment, Equity Ownership. Jiang:Biogen Idec: Employment, Equity Ownership. Nugent:Biogen Idec: Employment, Equity Ownership. Pierce:Biogen Idec: Employment, Equity Ownership. Allen:Biogen Idec: Employment, Equity Ownership.

scholarly journals Evaluation of a Blood Coagulation Factor IX Variant That Functions Independently of Factor VIII As an Alternative Treatment for Hemophilia A

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1110-1110
Author(s):  
Viola J.F. Strijbis ◽  
Ka Lei Cheung ◽  
Pavlina Konstantinova ◽  
Ying Poi Liu ◽  
Sander J van Deventer ◽  
...  
Keyword(s):  
Factor Viii ◽  
Tissue Factor ◽  
Alternative Treatment ◽  
Active Site ◽  
Research Funding ◽  
Thrombin Generation ◽  
Hemophilia A ◽  
Activation Mechanism ◽  
Hek293 Cells ◽  
Synergistic Enhancement

The serine protease factor IXa (FIXa) serves an important role in coagulation by catalyzing the proteolytic activation of factor X (FX) together with its cofactor VIIIa (FVIIIa). Being a critical protease in coagulation, the FIXa structure has evolved to be subjected to strict regulatory mechanisms. While FIXa displays considerable structural homology with other coagulation serine proteases, its active site is uniquely controlled by the 99-loop that blocks access to the active site pocket. Cofactor-mediated interaction of FIXa with its substrate FX induces a conformational change that allows for active site engagement and substrate catalysis. Previously, the molecular constraints of the 99-loop were lifted due to specific modifications in both the 99-loop (K265A), the S1 active site subpocket (V181I, I383V), and the L6F substitution, thereby generating FIX-FIAV [Quade-Lyssy et al. J. Thromb. Haemost. 2014]. As a result, this variant is capable of functioning independently of factor VIII (FVIII). Moreover, FIX-FIAV was demonstrated to ameliorate the hemophilia A phenotype both in vitro and in vivo. To further evaluate its therapeutic potential, FIX-FIAV was stably expressed in HEK293 cells and purified by ion-exchange and hydrophobic interaction chromatography. Evaluation of the kinetics of tissue factor-factor VIIa (TF-FVIIa) activation of FIX-FIAV revealed kinetic parameters similar to those of human wild-type FIX(-WT). Analysis of FIX activation intermediates that are formed upon proteolysis by TF-FVIIa or factor XIa demonstrated prolonged formation of FIX-FIAVα, while no FIXa-WTα could be observed. This is consistent with delayed cleavage at position 180, likely resulting from the V181I substitution in FIX-FIAV. Given that the activation mechanism of FIX-FIAV is unperturbed, we next assessed the specific FVIII clotting activity and demonstrated that FIX-FIAV exhibited significant FVIII-like clotting activity (56 ± 4 U/mg) as opposed to FIX-WT (<13 U/mg). These values correlate with up to 28% of FVIII-independent activity for FIX-FIAV at FIX plasma levels (5 ug/mL), confirming that FIX-FIAV has the potential to enhance thrombin generation in FVIII deficiency. To validate this, tissue factor-initiated (0.5 or 1.0 pM) thrombin generation was assessed in FVIII-immunodepleted plasma, leading to a severely reduced thrombin peak (88% or 81% reduction, respectively) relative to conditions with 100% FVIII. Addition of FIX-FIAV (5 ug/mL) partially restored thrombin generation, demonstrated by an up to ~30% increase in both thrombin peak and endogenous thrombin potential. Evaluation of the FVIII-independent activity of FIX-FIAV in severe hemophilia A patient plasma with or without an inhibitor resulted in an up to 18% or 32% FVIII-like activity, respectively, demonstrating efficacy of FIX-FIAV in the presence of FVIII inhibitors. Although unlikely, it remains to be determined whether specific FVIII-inhibitors may impact FIX-FIAV function. Adding 100% FVIII or low- to mid-range therapeutic concentrations of the bispecific antibody emicizumab to FVIII-deficient plasma incubations with FIX-FIAV resulted in a synergistic enhancement of thrombin generation, demonstrated by a 9-fold increase in thrombin peak. This is consistent with the previously demonstrated hyperactivity of FIX-FIAV in a cofactor-dependent system. In contrast, no synergistic effect on thrombin generation was observed when combining FIX-FIAV with physiologically relevant concentrations of FEIBA or NovoSeven. Summarizing, FIX-FIAV is characterized by a preserved mechanism of activation in addition to being capable of sustaining therapeutic levels of coagulation activity in FVIII deficiency. This provides support for the use of FIX-FIAV as an alternative treatment for hemophilia A. Disclosures Strijbis: uniQure Biopharma B.V.: Research Funding. Konstantinova:uniQure Biopharma B.V.: Employment. Liu:uniQure Biopharma B.V.: Employment. van Deventer:uniQure Biopharma B.V.: Employment. Bos:uniQure Biopharma B.V.: Membership on an entity's Board of Directors or advisory committees, Research Funding.

Platelet-Derived Beta Thromboglobulin: A Potential Novel Activator of Coagulation Factor X

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 2276-2276
Author(s):  
Karl Egan ◽  
Hui Ma ◽  
Barry Kevane ◽  
Áine Lennon ◽  
Elaine Neary ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Research Funding ◽  
Protein C ◽  
Thrombin Generation ◽  
Chromogenic Substrate ◽  
Factor X ◽  
Advisory Committees ◽  
Activated Platelets ◽  
Procoagulant Effect ◽  
Inhibitory Antibodies

Abstract Background During clotting, factors IXa and VIIa participate in the activation of Factor X, leading to thrombin generation. This process occurs on the surface of activated platelets. Activated platelets release an array of proteins that can modulate thrombin generation. This includes platelet factor 4 (PF4), a chemokine that modulates coagulation by promoting protein C activation and by attenuating the anticoagulant activity of activated protein C. PF4 shares significant homology with another protein released in high concentration by platelets, β-thromboglobulin (βTG). The physiological effects of βTG, including effects on blood coagulation, are poorly characterized. The aim of this study was to assess the effect of βTG on blood coagulation. Methods The effect of purified human βTG on coagulation was determined using the prothrombin time (PT), activated partial thromboplastin time (APTT), calibrated automated thrombography (4µM phospholipids ± 1pM tissue factor (TF)) and chromogenic FX and prothrombin activation assays. Mass spectrometry and surface plasmon resonance (SPR) were used to assess the composition of the purified βTG preparation and to measure protein-protein interactions respectively. Results Mass spectrometry confirmed the absence of TF, FVIIa, FVIIIa, FIXa, FVa, and FXa in the βTG preparation. In normal pooled plasma, βTG dose-dependently increased the rate and extent of TF stimulated thrombin generation. In the absence of βTG, the lagtime was 9±1 min, which was shortened in a dose-dependent manner upon incubation with βTG (100µg/ml; 5±1 min, p<0.05). Incubation with βTG (50µg/ml) also shortened the APTT (35±1 to 25±1 secs, p<0.05) and reduced the lagtime to thrombin generation (26±5 to 7±1 min, p<0.05) and increased the peak thrombin generation (60±30 to 97±23nM, p<0.05) in the absence of an exogenous TF stimulus. Immunodepleted plasmas and inhibitory antibodies were used to determine the underlying mechanism of action. In FVIII-deficient plasma, thrombin generation was not observed in the absence of an exogenous TF stimulus. However, upon incubation with βTG (50µg/ml), thrombin generation was observed and peak thrombin generation increased from 1±1 to 75±12nM IIa (p<0.05). βTG also shortened the APTT in FVIII-deficient plasma from 131±8 to 103±14 secs (50µg/ml, p<0.05). The procoagulant effect of βTG in FVIII-deficient plasma was not inhibited by TF or FVIIa inhibitory antibodies, suggesting that the effect was independent of the intrinsic tenase complex, TF or FVIIa. Interestingly, homologous PF4 did not induce thrombin generation in FVIII-deficient plasma (peak thrombin generation was 75±12nM v 0±0nM IIa upon incubation with 50µg/ml βTG and PF4 respectively). The procoagulant effect of βTG persisted when thrombin generation was independent of FV activation (supplementation of FV-deficient plasma with FVa). In contrast, the effect was not observed when thrombin generation was independent of FX activation (supplementation of FX-deficient plasma with FXa). Collectively, these data raised the possibility that βTG may modulate FX activation. To investigate this hypothesis, chromogenic FX activation was measured. Cleavage of a FXa-specific chromogenic substrate was observed upon incubation of βTG with FX, suggesting a direct effect of βTG upon FX activation. No measurable chromogenic substrate cleavage was observed upon incubation with βTG or FX alone. In contrast, βTG did not induce prothrombin activation, measured using a thrombin-specific chromogenic substrate. Using SPR, βTG was found to bind directly to immobilised FX (KD 1.36±0.7x10-7 M). The kinetics of the interaction between βTG and FX was lower than that between FIXa and FX (KD 4.25±1.90 × 10-9 M). Conclusion In conclusion, we have identified that βTG is a potential novel platelet-derived activator of coagulation FX. Moreover, βTG is capable of inducing thrombin generation in immunodepleted FVIII and FIX-deficient plasma, a finding that may be of translational relevance to patients with haemophilia. Disclosures Ní Áinle: Actelion Pharma: Research Funding; Leo Pharma: Research Funding; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Bayer: Membership on an entity's Board of Directors or advisory committees; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Membership on an entity's Board of Directors or advisory committees.

scholarly journals Efficacy and Safety of Recombinant Factor IX-FIAV and Bypassing Agents in Thrombin Generation Analyses in Hemophilia A Patient Plasma: The FIVITAS Study

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 3192-3192
Author(s):  
Lorenzo G.R. Romano ◽  
Viola J.F. Strijbis ◽  
Ka Lei Cheung ◽  
Ying Poi Liu ◽  
Andrew C. McCreary ◽  
...  
Keyword(s):  
Research Funding ◽  
Safety Assessment ◽  
Thrombin Generation ◽  
Hemophilia A ◽  
Lag Time ◽  
Factor Ix ◽  
Procoagulant Effect ◽  
Bypassing Agents ◽  
A Minor

Abstract Factor (F)IX-FIAV, a FIX variant with four amino acid substitutions that functions independently of the cofactor VIIIa, has been previously shown to ameliorate the hemophilia A (HA) phenotype in vivo [Quade-Lyssy et al. J. Thromb. Haemost. 2014]. Here we evaluated the efficacy of purified recombinant FIX-FIAV in severe, moderate, and mild hemophilia A patient plasma employing thrombin generation and intrinsic clotting activity (aPTT) analyses. The combination of FIX-FIAV with current hemophilia A therapeutics was used for preclinical safety assessment. Plasma was obtained from 21 HA patients, seven per HA phenotype, with a median age of 38 years [interquartile range (IQR) 27.5 - 49.5]. The plasma levels of FIX, FX, prothrombin, and antithrombin of all included patients were within the normal range. To determine the effect of FIX-FIAV on FXIa-triggered thrombin generation parameters (lag time, endogenous thrombin potential (ETP)), plasma was spiked with 100% (5 µg/ml in severe/mild) or 125% (6 µg/ml in moderate) FIX-FIAV prior to analysis. FIX-FIAV significantly shortened the lag time in all patient plasmas irrespective of disease severity (Figure 1) with an overall median of 4.4 min [IQR 3.6 - 6.9] in the absence of FIX-FIAV vs. 3.1 min [IQR 2.4 - 4.5] in the presence of FIX-FIAV (p&lt;0.0001, Table 1). Similar observations were obtained following aPTT analyses: median clotting time of 115.5 sec [IQR 105 - 173.9] without vs. 97.7 sec [IQR 91.8 - 136.2] with 100% FIX-FIAV (p = 0.0039). Conversion of the thrombin generation lag time to FVIII-like activity using a FVIII calibration for each individual patient plasma revealed that FIX-FIAV mitigated the HA phenotype from severe to moderate, from moderate to mild, and from mild to normal (Table 1). Interestingly, following the addition of FIX-FIAV a minor but significant decrease in ETP was observed for non-severe HA patient plasma (p = 0.016 for mild and p = 0.016 for moderate), while FIX-FIAV increased the median ETP in severe HA plasma by 2.1-fold (p = 0.22) (Figure 2, Table 1). This may result from competition between the added FIX-FIAV and endogenous FIX for interaction with residual functional FVIII. In line with this, experiments performed in the presence of an anti-FVIII antibody that inhibits FVIII activity significantly enhanced the ETP in all patient plasmas (p = 0.016 for each individual severity, Figure 2) in addition to shortening the lag time (Figure 1). Next, we evaluated the combination of FIX-FIAV with bypassing agents (1 IU/mL aPCC or 1.5 mg/mL rFVIIa) in nine patient plasmas, three per phenotype. Addition of aPCC or rFVIIa to FIX-FIAV-spiked plasma did not significantly affect aPTT clotting times nor ETP values in comparison to adding aPCC or rFVIIa only, respectively. The median lag time shortened significantly, albeit modestly, for the combination of FIX-FIAV with aPCC in comparison to conditions with aPCC only: 5.2 min [IQR 3.0 - 6.4] vs. 5.5 min [IQR 3.6 - 7.7], p = 0.0078, respectively. Similar findings were obtained when combining FIX-FIAV with rFVIIa relative to rFVIIa only: median lag time 4.9 min [IQR 2.2 - 6.1] vs. 5.3 min [IQR 3.3 - 8.8], p = 0.0039. Hence, no substantial synergistic effect was observed when combining FIX-FIAV with bypassing agents aPCC or rFVIIa for HA. In contrast, combining approximate hemostatic levels (55 µg/ml) of emicizumab, a bispecific antibody mimicking FVIIIa, with FIX-FIAV resulted in a ~1.1-fold reduced lag time and ETP relative to emicizumab alone (p = 0.016 and p = 0.004 respectively). This is suggestive of a minor synergistic procoagulant effect, which is consistent with the FIX(a)-FX(a) bridging capacity of emicizumab. In conclusion, FIX-FIAV could serve as a potential treatment for hemophilia A as it mitigates the hemophilia A phenotype in patient plasma, also in the presence of an inhibitory anti-FVIII antibody. While further safety assessment is warranted, no severe procoagulant effects were observed for the combination of FIX-FIAV with conventional hemophilia A therapeutics. Figure 1 Figure 1. Disclosures Romano: Swedish Orphan Biovitrum B.V.: Other: Travel grant and aforementioned Research Funding in the form of the Young Investigator's Award 2020, Research Funding. Liu: uniQure Biopharma B.V.: Current Employment. McCreary: uniQure Biopharma B.V.: Ended employment in the past 24 months. Leebeek: Roche: Other: DSMB member of a study sponsored by Roche; uniQure Biopharma B.V.: Consultancy, Research Funding; Swedish Orphan Biovitrum B.V.: Other: Travel support, Research Funding; Biomarin: Consultancy; CSL Behring: Consultancy, Research Funding; Shire/Takeda: Consultancy, Research Funding. Bos: VarmX B.V.: Research Funding; uniQure Biopharma B.V.: Research Funding.

Endotoxin-Induced Tissue Factor in Human Monocytes is Dependent upon Protein Kinase C Activation

1993 ◽  
Vol 70 (05) ◽  
pp. 800-806 ◽  
Author(s):  
C Ternisien ◽  
M Ramani ◽  
V Ollivier ◽  
F Khechai ◽  
T Vu ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Tissue Factor ◽  
Factor Ix ◽  
Transcriptional Level ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Human Monocytes ◽  
Kinase C ◽  
Pkc Activation

SummaryTissue factor (TF) is a transmembrane receptor which, in association with factors VII and Vila, activates factor IX and X, thereby activating the coagulation protease cascades. In response to bacterial lipopolysaccharide (LPS) monocytes transcribe, synthesize and express TF on their surface. We investigated whether LPS-induced TF in human monocytes is mediated by protein kinase C (PKC) activation. The PKC agonists phorbol 12- myristate 13-acetate (PMA) and phorbol 12, 13 dibutyrate (PdBu) were both potent inducers of TF in human monocytes, whereas 4 alpha-12, 13 didecanoate (4 a-Pdd) had no such effect. Both LPS- and PMA-induced TF activity were inhibited, in a concentration dependent manner, by three different PKC inhibitors: H7, staurosporine and calphostin C. TF antigen determination confirmed that LPS-induced cell-surface TF protein levels decreased in parallel to TF functional activity under staurosporine treatment. Moreover, Northern blot analysis of total RNA from LPS- or PMA-stimulated monocytes showed a concentration-dependent decrease in TF mRNA levels in response to H7 and staurosporine. The decay rate of LPS-induced TF mRNA evaluated after the arrest of transcription by actinomycin D was not affected by the addition of staurosporine, suggesting that its inhibitory effect occurred at a transcriptional level. We conclude that LPS-induced production of TF and its mRNA by human monocytes are dependent on PKC activation.

Sign in / Sign up

Export Citation Format

Share Document