Antithrombin (recombinant) (ATryn): Recombinant human antithrombin approved for the prevention of perioperative and peripartum thromboembolic events in hereditary antithrombin-deficient patients

This agent is a recombinant human antithrombin (AT) manufactured via recombinant DNA technology using genetically engineered goats. AT exerts its regulatory effects on hemostasis by inhibiting thrombin and factor Xa through the formation of a complex that is rapidly removed from the circulation. AT (recombinant) was approved on February 6, 2009, for the prevention of perioperative and peripartum thromboembolic events in patients with hereditary antithrombin deficiency.

Efficacy. The efficacy of this agent was assessed by comparing data from 2 prospective, single-arm, open-label studies in which patients were treated with AT (recombinant) with data from patients treated with plasma AT, which were derived from a prospectively designed, concurrently conducted retrospective chart review. In the open-label study, AT (recombinant) was administered as a continuous infusion for ≥3 days beginning 1 day before the surgery or delivery. Patients treated with plasma AT received the agent as single bolus infusions for ≥2 days. Among patients treated with AT (recombinant), 1 patient (3.2%) experienced a confirmed thromboembolic event; in patients treated with plasma AT, no patients experienced a confirmed thromboembolic event (lower 95% confidence bound of difference, –0.167). As the 95% lower confidence bound of difference was greater than the prespecified lower confidence bound of –0.20, AT (recombinant) was determined to be noninferior to plasma AT.

Safety. Patients treated with AT (recombinant) may experience allergic-type hypersensitivity reactions; therefore, patients should be closely monitored and observed for symptoms of a hypersensitivity reaction throughout the infusion. Anticoagulant drugs that use AT to exert their effects may be affected by AT (recombinant) therapy initiation or withdrawal. Coagulation tests should therefore be performed regularly, particularly in the hours immediately after the initiation or withdrawal of AT (recombinant) treatment. The most common adverse events associated with this agent include hemorrhage (intra-abdominal, hemarthrosis, and postprocedural) and infusion-site reaction.