BETHESDA, MD 26 December 2013—FDA on December 23 announced approval of recombinant coagulation factor XIII A-subunit, or Tretten, for the prevention of bleeding in patients with a congenital deficiency of factor XIII A subunit.
Factor XIII, also known as fibrin-stabilizing factor, has two A subunits and two B subunits. According to the National Center for Biotechnology Information, the A subunits have enzymatic activity but the B subunits do not.
The United States has 67 people with factor XIII deficiency, according to the World Federation of Hemophilia's most recently available global survey.
The labeling (PDF) for recombinant coagulation factor XIII A-subunit recommends a dosage of 35 IU per kilogram of body weight once monthly. Each dose is to be given by i.v. injection. The goal is to achieve a trough factor XIII activity level that is >10% of the normal value for people who do not have the deficiency.
Reconstitution of the contents of a vial of Tretten in accordance with the labeling's instructions should yield a solution containing 667–1042 IU of recombinant coagulation factor XIII A-subunit per milliliter. This solution must be used within three hours. To facilitate the measurement of a small volume for i.v. administration, 0.9% sodium chloride injection may be added to the coagulation factor solution. The dose should be injected at a rate not greater than 1–2 mL/min.
During the clinical trials of the coagulation factor product in patients with congenital factor XIII A-subunit deficiency, the most common adverse reactions were headache, pain in an extremity, pain at the injection site, and an increase in the level of D dimer. The product's labeling says this increase in D dimer occurred without evidence of thromboembolic events.
Manufacturer Novo Nordisk said Tretten should be available to U.S. patients in early 2014.
The company will supply the product in single-use vials containing 2000–3125 IU of lyophilized recombinant coagulation factor XIII A-subunit. The exact amount of factor XIII A subunit is stated on the carton and vial. Each carton contains a vial of lyophilized coagulation factor, a vial of diluent, and a vial adaptor for use in adding the diluent to the coagulation factor and preparing the dose for administration.
Vials of the lyophilized coagulation factor should be stored at 2–8 °C and protected from light.
FDA said Tretten is the first recombinant product available to patients with congenital factor XIII A-subunit deficiency to routinely prevent bleeding.
Factor XIII concentrate, produced by pooling human plasma from U.S. donors, was approved by FDA in 2011.