Developing the First Recombinant Factor XIII for Congenital Factor XIII Deficiency: Clinical Challenges and Successes.

Congenital factor XIII (FXIII) deficiency is a rare, autosomal recessive bleeding disorder with potentially life-threatening consequences. FXIII is composed of two subunits (A and B), and a deficiency or dysfunction of either can result in FXIII deficiency. Traditionally, FXIII deficiency has been managed by infusing plasma-derived products containing FXIII (fresh frozen plasma, cryoprecipitate, and plasma-derived FXIII concentrates), all of which contain both subunits. Despite the increased safety of plasma-derived products, concern remains regarding potential viral safety issues. This review describes the development, from concept to clinical use, of a recombinant FXIII molecule (containing subunit A only; rFXIII-A2) for congenital FXIII-A subunit deficiency. Unmet needs and ongoing challenges in congenital FXIII deficiency are also discussed. Despite the challenges in developing a product for a very rare bleeding disorder, the information gathered on efficacy, safety, and pharmacokinetics of FXIII replacement therapy represents the largest dataset on congenital FXIII-A subunit deficiency in the world. It also provides evidence for the safety and efficacy of monthly prophylaxis with 35 IU/kg of rFXIII-A2 in patients with FXIII-A subunit deficiency. The issues encountered and overcome, along with lessons learned, may be applied to and encourage the development of new recombinant products for other rare bleeding disorders. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.