Immunogenicity and safety of re-exposure to recombinant human thrombin in surgical hemostasis.

BACKGROUND: This Phase 4, open-label study evaluated the immunogenicity and safety of a second exposure to recombinant human thrombin (rThrombin) in adult patients with previous exposure to rThrombin. STUDY DESIGN: Topical rThrombin was applied as a hemostatic aid during a surgical procedure (day 1). Adverse events and clinical laboratory abnormalities were monitored to day 29 (study end). Immunogenicity samples were collected on days 1 and 29. Thirty-one patients were treated at 9 study sites; 30 patients completed the study. RESULTS: Mean age was 59.5 years; 61.3% of patients were male. Study operations types included spinal (n = 23 of 31; 74.2%), arterial reconstruction or peripheral arterial bypass (n = 4; 12.9%), arteriovenous vascular access procedure (n = 3; 9.7%), and other (n = 1; 3.2%). A median of 10 mL rThrombin (1,000 IU/mL; range 5 to 60 mL) was prepared per patient. Median elapsed time since previous rThrombin exposure was 1.3 years (range 19 days to 3.3 years). Recombinant human thrombin was not observed to be immunogenic; no patients (n = 0 of 30, 0%; 95% CI 0.0%, 11.6%) became positive for anti-rThrombin product antibodies at day 29, approximately 1 month after the second exposure to rThrombin. The most commonly reported adverse events were procedural pain (n = 23 of 31, 74.2%), constipation (n = 8, 25.8%), and nausea (n = 8, 25.8%) All adverse events and clinical laboratory abnormalities were considered unrelated to treatment. For the majority of patients, maximal severity of any adverse event was mild or moderate. CONCLUSIONS: The immunogenicity and safety results of this Phase 4 rThrombin trial suggest that patients with known previous exposure may be safely re-exposed to topical rThrombin.

Safety and pharmacokinetics of recombinant factor XIII-A2 administration in patients with congenital factor XIII deficiency.

Congenital factor XIII (FXIII) deficiency is associated with a tendency for severe bleeding, a risk for spontaneous abortion, and a high rate of spontaneous intracranial hemorrhage. This phase 1 escalating-dose study was developed to evaluate the safety and pharmacokinetics of a single administration of human recombinant FXIII-A2 (rFXIII-A2) homodimer in adults with congenital FXIII deficiency. Pharmacokinetics and activity of rXIII and changes in endogenous B subunit levels were assessed. Recombinant FXIII-A2 homodimer were complexed with endogenous FXIII-B subunits to form an FXIII-A2B2 heterotetramer with a half-life of 8.5 days, similar to that of endogenous FXIII. The median dose response was a 2.4% increase in FXIII activity based on unit per kilogram rFXIII administered. After the administration of rFXIII-A2, clot solubility normalized as measured by clot lysis in urea. Clot strength and resistance to fibrinolysis, as assessed by thromboelastography, also improved. Safety reviews were conducted before each dose escalation; no serious adverse events, including bleeding or thrombosis, were noted during the study. In addition, there was no evidence of the generation of specific antibodies to rFXIII or yeast proteins. Recombinant FXIII appears to be a safe and potentially effective alternative for FXIII replacement in patients with FXIII deficiency.

Safety and pharmacokinetics of recombinant factor XIII in healthy volunteers: a randomized, placebo-controlled, double-blind, multi-dose study.

Factor XIII (FXIII) is a plasma transglutaminase that covalently cross-links fibrin proteins to one another and to other proteins, increasing the mechanical strength of blood clots. Endogenous FXIII is the final enzyme in the clotting cascade and circulates as a heterotetramer comprising 2 FXIII-A subunits and 2 FXIII-B subunits. Recombinant human FXIII A2 (rFXIII) homodimer is produced in Saccharomyces cerevisiae. Upon injection, rFXIII combines with the free FXIIIB subunit that circulates in excess to form the rA2B2 tetramer. In this placebo-controlled, double-blind, multi-dose study, the safety, pharmacokinetics, and pharmacodynamics of rFXIII were studied in 24 healthy volunteers, who were randomized in 2 cohorts of 12 subjects each. In each cohort, 8 subjects received 5 daily intravenous doses of rFXIII (10 or 25 U/kg), and 4 subjects received placebo. Recombinant FXIII was well tolerated. No deaths or serious adverse events occurred. The type and frequency of adverse events showed no pattern or dose response. No clinically significant changes in haematology, serum chemistry, or urinalysis laboratory values were observed. No clinical coagulopathy or thrombosis was observed. Recombinant FXIII did not produce any anti-yeast or anti-FXIII antibodies. After 5 daily doses of rFXIII, accumulation indices indicated a 3 to 4fold accumulation of rFXIII in plasma. The elimination half-life, estimated for rFXIII as the heterotetramer, ranged from 228-346 hours for the 10U/kg dose group and 167-197 hours for the 25U/kg dose group. The safety, pharmacokinetic, and immunogenic profile of rFXIII suggests it may have potential use in patients with congenital or acquired FXIII deficiency.