IVPRP also solved a third big problem: delivery. By using the highly expressive albumin gene to produce other proteins, they avoid having to reach a large number of cells -- a tiny number of modified cells (less than 1% in most cases) can produce enough protein to cure the disease.
SB-728 has always worked great for the cells it could biallelically modify, but getting enough cells modified has taken years. IVPRP gets around that by needing to modify only very few cells to succeed.
Although long-time board participants have heard it all before many times, the IVPRP really is an amazing medical innovation and its value should become clear soon after the first trial begins.