Prophylaxis for Hemophilia in the Era of Extended Half-Life Factor VIII/Factor IX Products.

There are two main bioengineering approaches to extending the half-life of factor (F)VIII or FIX products used for hemophilia replacement therapy. These are fusion to Fc-immunoglobulin G (FVIII and FIX) or to albumin (FIX) or pegylation/glycopegylation (FVIII and FIX). Four FVIII and three FIX products are in clinical development or have recently been licensed in regions of the world. The reported half-life extension is approximately 1.5-fold for FVIII and 2.5-fold, or even longer, for FIX. Clinical trials have shown promising results with respect to extension of dose intervals and efficacy in the treatment and prevention of bleeding events. The role of these products in clinical practice has been discussed in terms of either improving convenience and adherence through prolongation of the interval between infusions or maintaining current intervals thereby increasing trough levels and the safety margin against bleeds. This review of extended half-life products addresses the possibilities and problems of their introduction in hemophilia treatment. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.