A safety review of topical bovine thrombin-induced generation of antibodies to bovine proteins

BACKGROUND: Topical bovine thrombin has been used to accelerate attainment of hemostasis in the surgical setting for >60 years, and its immunogenicity has been widely reported. Although the development of antibodies is inherent in the introduction of any non-self-therapeutic protein such as bovine-sourced thrombin, there are questions about the relationship between the presence of antibodies to constituents of the therapeutic protein preparation and the occurrence of clinically relevant adverse events (AEs). OBJECTIVE: This review examines the proposed mechanisms for the immunogenicity of topical bovine thrombin preparations and summarizes available evidence from randomized clinical trials, observational studies, and case reports to explore possible relationships between the reported immunogenicity of topical bovine thrombin and the occurrence of AEs. METHODS: A search of MEDLINE (1966-August 2008) for studies published in English was conducted using the Medical Subject Heading terms surgery, antibodies, and hemorrhage, as well as equivalent key words for bovine, adverse events, and thrombin. For inclusion in the review, studies had to report clinical or laboratory safety data for patients exposed to topical bovine thrombin during surgery. RESULTS: The evidence suggests that patients with repeated perioperative exposure to topical bovine thrombin have a 3- to 10-fold greater risk for development of antibodies to topical bovine thrombin than do patients with no history of surgery-related exposure to this agent. Early case reports associated the development of anti-bovine protein antibodies with bleeding and/or thrombotic complications. However, in one prospective, randomized controlled trial comparing topical bovine thrombin with topical recombinant human thrombin, 99.5% of patients in each treatment arm developed postoperative AEs. In an-other, 54% and 55% of patients in the respective treatment arms developed postoperative AEs. In a prospective, randomized controlled trial that compared topical bovine thrombin and plasma-derived human thrombin, 95.5% of patients in each treatment arm developed postoperative AEs. CONCLUSIONS: Repeated perioperative exposure to topical bovine thrombin may increase both the prevalence and titers of antibodies to >or=1 protein contained in nonhomogeneous topical bovine thrombin preparations. However, the evidence reviewed does not support a definitive association between preoperative or postoperative generation of anti-bovine protein antibodies and an increased risk of AEs in surgical patients treated with topical bovine thrombin.