Pharmacokinetics, safety and efficacy of a recombinant factor IX product, trenonacog alfa in previously treated haemophilia B patients.

INTRODUCTION: Trenonacog alfa (IB1001) is a recombinant factor IX (rFIX) manufactured in Chinese hamster ovary (CHO) cells. IB1001 was evaluated in a multicentre clinical trial with haemophilia B patients. AIM: The aim was to establish IB1001 pharmacokinetic non-inferiority to comparator rFIX, safety and efficacy in previously treated patients (PTPs) with haemophilia B. METHODS: Subjects were severe or moderately severe haemophilia B adult and adolescent PTPs with no history of FIX inhibitors. RESULTS: IB1001 PK non-inferiority to comparator rFIX was demonstrated through ratio of AUC0-∞ in 32 subjects. IB1001 was well tolerated in all 76 treated subjects; the most common adverse drug reaction was headache (2.6% of subjects) and there were no reports of FIX inhibitors. Transient non-inhibitory binding FIX antibodies and anti-CHO cell protein antibodies developed in 21% and 29% of subjects respectively; no safety concerns were associated with development of these antibodies. Prophylaxis (mean duration ± SD: 17.9 ± 9.6 months, mean dose: 55.5 ± 12.9 IU/kg, median 1.0 infusion per week) was effective in preventing bleeds (median annual bleed rate: 1.52, interquartile range: 0.0-3.46). One or two IB1001 infusions resolved 84% of the bleeds, while for 84% of treatments haemostatic efficacy of IB1001 was rated excellent or good. IB1001 haemostatic efficacy for all 19 major surgeries was rated adequate or better than adequate. CONCLUSIONS: IB1001 is safe and efficacious for treatment of bleeds, routine prophylaxis and perioperative management in haemophilia B patients.

F8 haplotype and inhibitor risk: results from the Hemophilia Inhibitor Genetics Study (HIGS) Combined Cohort.

Ancestral background, specifically African descent, confers higher risk for development of inhibitory antibodies to factor VIII (FVIII) in haemophilia A. It has been suggested that differences in the distribution of FVIII gene (F8) haplotypes, and mismatch between endogenous F8 haplotypes and those comprising products used for treatment could contribute to risk. Data from the Hemophilia Inhibitor Genetics Study (HIGS) Combined Cohort were used to determine the association between F8 haplotype 3 (H3) vs. haplotypes 1 and 2 (H1 + H2) and inhibitor risk among individuals of genetically determined African descent. Other variables known to affect inhibitor risk including type of F8 mutation and human leucocyte antigen (HLA) were included in the analysis. A second research question regarding risk related to mismatch in endogenous F8 haplotype and recombinant FVIII products used for treatment was addressed. Haplotype 3 was associated with higher inhibitor risk among those genetically identified (N = 49) as of African ancestry, but the association did not remain significant after adjustment for F8 mutation type and the HLA variables. Among subjects of all racial ancestries enrolled in HIGS who reported early use of recombinant products (N = 223), mismatch in endogenous haplotype and the FVIII proteins constituting the products used did not confer greater risk for inhibitor development. Haplotype 3 was not an independent predictor of inhibitor risk. Furthermore, our findings did not support a higher risk of inhibitors in the presence of a haplotype mismatch between the FVIII molecule infused and that of the individual.

Potency and mass of factor VIII in FVIII products.

Several factor (F) VIII products of different origin and structure are being used for haemophilia A treatment worldwide. The assessment of FVIII concentration in these products is done using activity assays, which are dependent upon the assay and its modifications. To evaluate FVIII products for potency and for FVIII concentration and specific activity, three activity-based assays [activated partial thromboplastin time (APTT), intrinsic FXase and synthetic coagulation proteome] and two immunoassays (ELISA and western blotting) were used in this study with albumin-free full-length recombinant (r) FVIII as a standard. In all activity assays, products A and B (both contain full-length rFVIII) at 1 U mL(-1) showed potency similar to that of the 0.7 nm (1 U mL(-1)) rFVIII standard. Product E (contains truncated rFVIII) was less potent in the APTT (83% of standard) and product C (contains plasma FVIII) was less potent in FXase assays (66%). The ELISA immunoassay revealed that the specific activity of FVIII proteins in products A-C and E varied over a wide range (3900-13 200 U mg(-1)) and was higher for most lots when compared with the standard (5000 U mg(-1)), whereas the specific activity of product D (contains plasma FVIII) was lower than expected (3200-4800 U mg(-1)). (i) FVIII potency estimated in different assays gives dissimilar results; (ii) the specific activity of FVIII in various FVIII products is different and inconsistent. Thus, the administration of an equal FVIII potency in units means the administration of different amounts of FVIII protein, which may partly explain apparent discrepancies in product performance.

Hemophilia therapy innovation: development of an advanced category recombinant factor VIII by a plasma/albumin-free method. Proceedings of a Special Symposium at the XIXth Congress of the International Society on Thrombosis and Haemostasis, July 12-18, 2003, Birmingham, UK.

Replacement therapy for hemophilia A has evolved from the early use of whole blood, citrated plasma, and cryoprecipitate, to purified factor VIII (FVIII) concentrates, first derived from plasma, then produced by recombinant DNA technology. Recombinant FVIII (rFVIII) concentrates have provided improved safety for patients with hemophilia A since they significantly reduce the risk of transmission of blood-borne infections. Nevertheless, human- or animal-derived plasma proteins are still included at some step in preparation of all previously licensed rFVIII, thereby introducing the potential for transmission of human or animal pathogens. Anti-hemophilic factor (recombinant), plasma/albumin-free method (rAHF-PFM), a novel advanced category rFVIII produced without the addition of human or animal plasma proteins, has been developed with the goal of providing the greatest possible margin of safety to hemophilia patients. This report, based on a symposium of the XIXth International Society on Thrombosis and Haemostasis Congress, provides an overview of the rAHF-PFM development program as well as current findings from the global clinical evaluation of rAHF-PFM in pediatric and adult previously treated patients.

Severe antithrombin III deficiency in an infant associated with multiple arterial and venous thromboses.

Inherited antithrombin III (AT-III, heparin cofactor) deficiency is a rare condition, presenting with thrombotic disease in adult life. This paper reports an 8 months old South African Black male infant with multiple large vessel venous and arterial thromboses, and E. coli septicaemia. This was associated with an extremely low plasma AT-III level. Micronodular cirrhosis and intracytoplasmic hyaline globules in the liver cells were present. These globules were eosinophilic, and PAS-positive after diastase. They measured approximately 5 mu to 30 muin diameter, occurred singly in the liver cells and were located mainly in the periportal areas. The histological findings in the liver are similar to those observed in alpha 1-antitrypsin (AAT) deficiency in which the intracytoplasmic globules represent accumulation of altered AAT. Immunochemical studies carried out on formalin fixed tissue failed to detect cross reaction material with anti-alpha 1 antitrypsin or anti-AT III antiserum. This is the first case report of AT-III deficiency presenting in infancy. It is also the first case associated with distinctive liver pathology. The available data presented are insufficient to distinguish between an inborn defect and acquired caused of the severely depressed AT-III plasma level and the distinctive liver pathology.

The reversible antithrombin activity of incubated plasma.

The thrombin time of normal citrated plasma is progressively prolonged on incubation in open glass tubes at 37 degrees C. The phenomenon is dependent on the temperature and duration of incubation, on the pH, and on the concentration of calcium ions present. Platelet-rich citrated plasma fails to exhibit augmented antithrombin activity when similarly incubated, and the addition of washed platelets to platelet-poor plasma inhibits this activity. The clot retarding action of incubated plasma against thrombin is also manifested against Arvin (Ancrod), but not against Reptilase-R. This thrombin time lengthening may be inhibited by incubation with anti-antithrombin III antiserum thus indicating that the phenomenon of thrombin time lengthening is consistent with enhanced activity of antithrombin III. It is unlikely that alterations in the activity of alpha2-macroglobulin, is important in the reduced thrombin-coagulability of incubated plasma. Interference with the polymerisation of fibrin monomers by the physico-chemical changes may contribute to the observed phenomenon.

Dialysis and renal transplant in a hemophiliac.

Hemodialysis was initiated in a mild-moderate hemophiliac at 15 years of age. Hematuria had been a frequent and persisting feature from the age of five years without documented cause. Anemia and proteinuria was first detected at 13 years. A cadaver donor renal transplant was carried out after three months of hemodialysis. Massive intravesical bleeding complicated the immediate post-transplantation period. The allograft rejected after three months and the patient was maintained for eight years on home hemodialysis. A second cadaver donor allograft was carried out at 23 years of age. Again, massive intravesical hemorrhage was a problem post-transplant. The allograft is currently functioning 27 months post-transplant. Factor VIIIc activities have fluctuated between 5% and 40% in the absence of factor infusions.

A multicenter study of recombinant factor VIII (Recombinate) in previously treated patients with hemophilia A. The Recombinate Previously Treated Patient Study Group.

A prospective, open-label multicenter investigation has been conducted to compare pharmacokinetic parameters of recombinant DNA-derived FVIII (rFVIII) and plasma-derived FVIII concentrate (pdFVIII) and to assess safety and efficacy of long-term home-treatment with rFVIII for subjects with hemophilia A. Following comparative in vivo pharmacokinetic studies, 69 patients with severe (n = 67) or moderate (n = 2) hemophilia A commenced a program of home treatment using rFVIII exclusively for prophylaxis and treatment of all bleeding episodes for a period of 1.0 to 5.7 years (median 3.7 years). The mean in vivo half-lives of rFVIII and pdFVIII were both 14.7 h. In vivo incremental recoveries at baseline were 2.40%/IU/kg and 2.47%/IU/kg, respectively (p = 0.59). The response to home treatment with rFVIII was categorized as good or excellent in 3,195 (91.2%) of 3,481 evaluated bleeding episodes. Thirteen patients received rFVIII for prophylaxis for twenty-four surgical procedures. In all cases, hemostasis was excellent. Adverse reactions were observed in only 13 of 13,591 (0.096%) infusions of rFVIII: none was serious. No patient developed an inhibitor to rFVIII.

In vivo recovery and survival of monoclonal-antibody-purified factor VIII concentrates.

In response to reports of discrepant in vitro assays of high-purity concentrates, a double-blind crossover study of in vivo recovery and half-life of two brands of monoclonal-antibody-purified factor VIII concentrates (Monoclate and Hemofil-M) was performed in 23 patients with hemophilia A. In vivo recoveries were close to values predicted from the labelled unitage when plasma samples were assayed by a one-stage method. When a two-stage assay was used, lower recoveries were calculated and the recovery with Hemofil-M was slightly but significantly lower than that with Monoclate. The concentrates were re-assayed in vitro by the two-stage method. Monoclate (which is assayed by the manufacturer using a two-stage method) contained 97% of the labelled potency and Hemofil-M (which is assayed by the manufacturer using a one-stage method) contained 81% of the labelled potency. Differences in in vitro and in vivo assay methods contribute to disparities between expected and observed factor VIII recovery. Clearance of Hemofil-M was significantly faster than that of Monoclate, but volume of distribution at the steady state, mean residence time, and plasma half-disappearance times of the two concentrates were not significantly different.

The impact of clotting factor concentrates on the immune system in individuals with hemophilia.

All reported studies to date, whether comparative or not, have shown a tendency toward a slower decrease in CD4+ numbers in patients receiving very high-purity agents with the rapidity in fall-off being affected by level of CD4+ numbers (low CD4+ numbers decreasing more rapidly), age (older persons showing more rapid CD4+ cell fall-off), and anti-HIV therapy. Clearly, these observations need to be extended in numbers, and the high-purity agents should also be similarly compared with the very high-purity therapies.

Gammagard and reported hepatitis C virus episodes.

Since first licensed in the United States in 1986, Gammagard, an intravenous immunoglobulin produced by the Hyland Division of Baxter Healthcare Corporation, had been considered an effective and safe form of immunoglobulin. Its safety had been proved in patients with immunoglobulin A (IgA) deficiency, including those with the complication of anti-IgA antibodies. However, in early 1994, there were reported episodes of hepatitis C virus transmission associated with administration of Gammagard manufactured during April 1993 and thereafter. The investigations into the mechanisms to account for these events, including the manufacturing processes, are reviewed. The results of studies and analyses by both Baxter and the US Food and Drug Administration, including first- and second-generation enzyme-linked immunosorbent assays, polymerase chain reaction analyses, and the solvent-detergent viral-inactivation manufacturing step, are discussed. Evaluations of donor histories identified a group of donors who contributed to three target lots of the agent and who were subsequently excluded from donor pools. The classification scheme and criteria for all patient reports of hepatitis associated with administration of Gammagard, as well as the classification of all hepatitis C virus episodes, are presented.

Bone mineral density and its association with inherited protein S deficiency.

Two unrelated children with thrombotic disease associated with inherited protein S deficiency and osteopenia have been identified. Measurement of protein S yielded markedly reduced levels of free protein S (less than 12.5%) in both propositi, a normal level of total protein S (79%) in propositus #1, and markedly reduced level of total protein S (34%) in propositus #2. Bone densitometry measurements of the two children revealed trabecular vertebral bone mineral content below two standard deviations. This defect is associated with vertebral body compression fractures in propositus #2. Therefore, it is hypothesized that protein S deficiency is associated with abnormalities of bone mineral density.

Assessment for evidence of non A-non B hepatitis in patients given n-heptane-suspended heat-treated clotting factor concentrates.

Nineteen patients, (2 adults, 17 children) with inherited bleeding disorders were infused with n-heptane-suspended-heated clotting factor concentrates. Twelve of the nineteen were previously untreated. Six patients were infused with Profilnine Heat-Treated and 13 with Profilate Heat-Treated. Five separate centers participated and were given various lots of concentrates for use. Blood from the seventeen children was sampled prior to entry, at infusion, 2 weeks, 6 weeks, 12 weeks and 6 months after the first infusion. The two adults were sampled every 2 weeks. Twelve of the 19 patients were followed beyond six months. Three patients demonstrated a rise in ALT during the first six months of observation with levels above 2.5 times the upper limit of normal. One of these patients showed a parallel increment in a-CMV IgM titer and a second patient, an adult, had previously received many units of single donor blood components. During the second 6 month observation interval, two patients showed a rise in ALT. One of these patients had been exposed to only one lot of concentrate with no other viral cause being determined. Two additional patients had a moderate increase in ALT up to 98 U/L (normal less than 50). No patients were clinically ill or showed jaundice during these episodes. The hepatitis episode at 11 months in the patient using one lot of concentrate, might suggest a non-viral mechanism in this instance. This study indicates that these concentrates may be associated with episodes of ALT above 2.5 times the upper limit of normal in approximately 20% of the patients treated, but the etiology of the raised ALT may not always be Non A-Non B hepatitis.

PROPLEX vs. PROPLEX SX: a controlled double blind study of the effectiveness in treating acute hemarthroses in hemophilia A patients with inhibitors to factor VIII.

A blinded randomized multicenter trial of two non-activated prothrombin complex concentrates was carried out to determine the clinical effectivity in the treatment of acute hemarthrosis in hemophiliac patients with inhibitors. The one product was prepared via DEAE Sephadex chromatography, while the second was fractionated via various precipitation procedures including polyethylene glycol. Equivalence of the two products was established with less than 15% difference in efficacy rates.

Prospective, randomized evaluation of the efficacy of fibrin sealant as a topical hemostatic agent at the cannulation site in neonates undergoing extracorporeal membrane oxygenation.

BACKGROUND: The topical hemostatic effect of fibrin sealant that has been solvent/detergent treated and plasminogen depleted was evaluated in a multicenter prospective, randomized controlled study at the cannulation site wound of infants undergoing extracorporeal membrane oxygenation (ECMO). METHODS: The test group received standard cauterization and Fibrin sealant, while the control group was given cauterization alone to control hemostasis at this site. Efficacy data were available on 173 randomized study subjects of whom 149 met study entry criteria. All were managed according to standard ECMO practice. RESULTS: Fibrin sealant reduced the risk of bleeding, was associated with less shed blood, and was associated with shorter duration of hemorrhage. Further, control infants showed an increased bleeding risk with less depressed fibrinogen levels and prothrombin time elevations >18 seconds prior to ECMO. CONCLUSION: Fibrin sealant is useful as a topical hemostatic agent in patients with coagulopathy not responding to standard surgical techniques.

Activity of intraperitoneal heparin during peritoneal dialysis.

A pharmacokinetic study of intraperitoneal heparin was undertaken in eleven chronic renal failure patients as a guide for its therapeutic use in peritoneal dialysis. The intraperitoneal heparin was assayed as the activated-partial-thromboplastin time (A-PTT) of peritoneal aspirate or outflow dialyzate added to control plasma. This was noted to decay relatively slowly, the mean t 1/2 of heparin in the peritoneal cavity being 10.8 +/- 0.93 hr. The heparin cofactor antithrombin III determined by both immunological and functional methods was found to be present in low concentration in residual peritoneal fluid aspirated prior to commencing dialysis. Generally this was less than one-third of normal plasma values, and with the repeated dilution and outflow sequences of dialysis the cofactor concentrations rapidly fell to negligible levels that were incapable of activating any heparin present. Systemic blood coagulation was unaffected by single 10000 U doses of heparin administered intraperitoneally in that plasma A-PTT values were not lengthened when measured over the ensuing six hours.

A multicenter clinical trial to evaluate the topical hemostatic efficacy of fibrin sealant in burn patients.

Current surgical management of deep partial-thickness and full-thickness burn wounds involves early excision and grafting. Blood loss during these procedures can be profound, thus prompting the use of topical hemostatic agents to control and minimize hemorrhage during grafting. The primary endpoint of this multicenter trial was to evaluate the efficacy of fibrin sealant as a topical hemostatic agent during skin grafting. The secondary endpoint was to obtain data to support the existing safety profile of a human fibrin sealant (FS) in participating patients as indicated by the type, severity, and frequency of any adverse events within the 24-hour postoperative period. A multicenter prospective, open label, Phase III multicenter, randomized, comparative clinical trial evaluated the use of fibrin sealant in burn patients undergoing skin graft procedures. Each patient served as his or her own control in this randomized, unblinded study of the effect on time to hemostasis in donor sites treated with the investigational FS product. At operation, 1 contiguous donor skin harvest site was bisected into 2 equal halves, 1 of which was then randomly selected and treated with fibrin sealant. At the end of the fibrin sealant application, the time to hemostasis in each of the donor site halves was identified by the operating surgeon and recorded by the research coordinator. The use of any other topical hemostatic agents was prohibited. A significant difference (P < .001) was demonstrated in the mean time to hemostasis between the fibrin sealant treated donor sites when compared painwise to the control sites. The significant difference was consistent across the 6 participating study centers. There were no adverse events associated with the use of fibrin sealant. The investigational FS product was shown to be efficacious, because it significantly decreases the time to hemostasis at the donor skin harvest site in patients undergoing skin grafting and was noted not to cause any adverse reactions.