Several fusion proteins have been approved for use in various indications (9, –, 11), including two albumin fusion proteins: Albiglutide, a GLP-1–albumin fusion protein for the treatment of type 2 diabetes (40), and rIX-FP for the treatment of hemophilia B. All have shown improved pharmacokinetics compared with nonfused counterparts in clinical studies, and although it is generally accepted that their half-life extension is due at least in part to FcRn-mediated salvage, FcRn recycling of albumin or albumin-fusion proteins at a cellular level has not been directly examined. The gene discussed is ALB; the disease is hemophilia B.