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Hemophilia B is a blood clotting disorder caused by deficient activity of coagulation factor IX (FIX). Multiple recombinant FIX proteins are currently approved to treat hemophilia B, and several gene therapy products are currently being developed. Codon optimization is a frequently used technique in the pharmaceutical industry to improve recombinant protein expression by recoding a coding sequence using multiple synonymous codon substitutions. The underlying assumption of this gene recoding is that synonymous substitutions do not alter protein characteristics because the primary sequence of the protein remains unchanged. However, a critical body of evidence shows that synonymous variants can affect cotranslational folding and protein function. Gene recoding could potentially alter the structure, function, and in vivo immunogenicity of recoded therapeutic proteins. Here, we evaluated multiple recoded variants of F9 designed to further explore the effects of codon usage bias on protein properties. The detailed evaluation of these constructs showed altered conformations, and assessment of translation kinetics by ribosome profiling revealed differences in local translation kinetics. Assessment of wild-type and recoded constructs using a major histocompatibility complex (MHC)-associated peptide proteomics assay showed distinct presentation of FIX-derived peptides bound to MHC class II molecules, suggesting that despite identical amino acid sequence, recoded proteins could exhibit different immunogenicity risks. Posttranslational modification analysis indicated that overexpression from gene recoding results in suboptimal posttranslational processing. Overall, our results highlight potential functional and immunogenicity concerns associated with gene-recoded F9 products. These findings have general applicability and implications for other gene-recoded recombinant proteins.

Thrombin generation (TG) assays are used widely to investigate both diseases and drugs that impact thrombosis and bleeding. TG assays were also instrumental in the identification of thrombogenic impurities in immune globulin products, which were associated with thrombotic adverse events in patients. TG assays are therefore now used by quality control laboratories of plasma derivative drug manufacturers and regulatory agencies responsible for the safety testing and release of immune globulin products. In this protocol, we describe a robust and sensitive version of the TG assay for quantitative measurement of thrombogenic activity in immune globulin products. Compared with the version of the assay commonly used in clinical laboratories that compares individual patient plasma samples with normal donor samples, our TG assay is suitable for quick (170-260 min) semiautomated analysis of multiple drug samples against the World Health Organization international standard for factor XIa. Commercially available reagents can be used for the assay, and it does not require specialized equipment. The protocol can be easily adapted for the measurement of the procoagulant activity of other biopharmaceuticals, e.g., coagulation factors.

Summary. Background: Tissue factor pathway inhibitor (TFPI) is a major regulator of clotting initiation and a promising target for pro- and anticoagulation therapy. The aptamer BAX499 (formerly ARC19499) is a high-affinity specific TFPI antagonist designed to improve hemostasis. However, it is not clear how stimulation of coagulation onset by inactivating TFPI will affect spatial and temporal clot propagation. Objective: To examine the BAX499 effect on clotting in a spatial, reaction-diffusion experimental system in comparison with that of recombinant activated factor VII (rVIIa). Methods: Clotting in plasma activated by immobilized tissue factor (TF) was monitored by videomicroscopy. Results: BAX499 dose-dependently improved coagulation in normal and hemophilia A plasma activated with TF at 2 pmole m−2 by shortening lag time and increasing clot size by up to ∼2-fold. The effect was TFPI specific as confirmed by experiments in TFPI-depleted plasma with or without TFPI supplementation. Clotting improvement was half-maximal at 0.7 nm of BAX499 and reached a plateau at 10 nm, remaining there at concentrations up to 1000 nm. The BAX499 effect decreased with TF surface density increase. RVIIa improved clotting in hemophilia A plasma activated with TF at 2 or 20 pmole m−2, both by shortening lag time and increasing spatial velocity of clot propagation; its effects were strongly concentration dependent. Conclusions: BAX499 significantly improves spatial coagulation by inhibiting TFPI in a spatially localized manner that is different to that observed with rVIIa.

This review is focused on the epidemiology of venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), associated with pregnancy. Superficial vein thrombosis, a less hazardous and less studied type of thrombosis in pregnant women, is beyond the scope of this review. This study discusses the VTE incidence rate in women from developed countries for both antepartum and postpartum periods and for subpopulations of women affected by additional risk factors, such as thrombophilias, circulatory diseases, preeclampsia of varying degrees of severity, and Caesarean section. To minimize bias due to historical changes in medical and obstetric practices, lifestyle, diet, etc., this review is generally limited to relatively recent studies, i.e., those that cover the last 35 years. The absolute risk or incidence rate was used to ascertain risk of VTE associated with pregnancy. For the studies where the direct incidence rates of VTE were not reported, we calculated an estimate of the observed but not reported absolute incidence rates using the data presented in respective articles.

BACKGROUND Thrombotic events (TEs) are serious adverse events that can occur following administration of clotting factors (CFs). OBJECTIVES To evaluate occurrence of same-day TEs for different CF products and potential risk factors. METHODS A retrospective cohort study of individuals exposed to CF products during 2008-2013 was conducted using a large commercial insurance database. CF products were identified by procedure codes, and TEs were ascertained via diagnosis codes. Crude same-day TE rates (per 1000 persons exposed) were estimated overall and by congenital factor deficiency (CFD) status, CF products, age and gender. Multivariable logistic regression analyses were used to control for confounding. Laboratory analysis was used to compare the procoagulant activities of FIX products. RESULTS Of 3801 individuals exposed to CFs, 117 (30.8 per 1000) had same-day TEs recorded. The crude same-day TE rate was higher for CF users without CFD, 70.2 (102 of 1452), as compared with those with CFD, 6.4 (15 of 2349) (RR, 11.0; 95% CI, 6.4-18.9). For individuals without CFD, a significantly increased same-day TE risk was identified for factor IX complex (OR, 6.92; 95% CI, 3.11-15.40), factor VIIa (OR, 9.42; 95% CI, 4.99-17.78) and other products when compared with fibrin sealant. An increased risk of a TE was found with older age (≥ 45 years), history of TEs and underlying health conditions. The laboratory identified elevated procoagulant activity in Profilnine(®) and Benefix(®) . CONCLUSIONS The study shows an increased same-day TE risk for CF users without CFD and suggests substantial off-label CF use. The study findings also show elevated same-day TE rates for different CF products and suggest the importance of product properties and patient factors.

Background In recent years, a number of tissue factor pathway inhibitor (TFPI) antagonists have been developed to serve as bypassing agents to improve hemostasis in hemophilia A. Since TFPI antagonists and FVIII concentrates are procoagulants, their combined effect on spatial clot formation could be potentially pro-thrombotic. Objective To investigate the cooperative effect of TFPI inhibition and supplementation of FVIII in hemophilia A in a spatial, reaction-diffusion experiment in vitro . Methods Plasma was collected at different time points from hemophilia A patients undergoing prophylaxis and was supplemented in vitro with TFPI inhibitor BAX499 (formerly ARC19499) at concentrations from 0 up to 600 nM. Clotting propagation in recalcified plasma activated by a surface with immobilized tissue factor (TF) was monitored by videomicroscopy. Results Increasing concentration of BAX499 improved coagulation for all hemophilia A plasma samples activated with TF at 1.6 pmole/m 2 by shortening lag time and increasing initial clot growth velocity and clot size. In contrast, plasma concentration of FVIII had little effect on lag time, but increased spatial clot growth velocity. There was a decrease in the BAX499 efficiency as FVIII concentration increased (lag time shortened by 50% if FVIII:C 30%). Conclusions The results indicate that BAX499 has an effect on clotting in hemophilia A plasma at low FVIII concentrations, however has little effect at high FVIII concentrations.