Use of Engineered Autologous BOEC for Gene Therapy of Canine Hemophilia A.

Hemophilia A is an attractive candidate disease for corrective gene therapy because relatively small amounts of the missing protein, FVIIII, have a significant biological effect. We previously described a novel approach: intravenous administration of ex vivo expanded BOEC (blood outgrowth endothelial cells) engineered to express FVIII. Robust therapeutic results were obtained using NOD/SCID mice and human BOEC stably transfected to express human FVIII (

WBCT (nl = 8-12 min) needs to be <20 min to reflect >0.1% FVIII activity; but the observed WBCT are clearly improved compared to baseline. One dog (E64) was treated for a mouth bleeds on d37 in cycle 2, and d36 in cycle 3. One animal (E64) developed hypotension and tachypnea during one of the infusions (probably because cells were not kept sufficiently in suspension) but recovered. Four of the infusions were associated with mild transient thrombocytopenia. Based on these initial scale-up experiments, it appears that use of engineered BOEC for gene therapy is an approach worthy of continued study, as cell doses can be increased and other improvements in the method are readily envisioned. It has a number of advantages, including use of autologous carrier cells with which any expression vector can be paired, ex vivo exposure to vector rather than in vivo, use of BOEC expansion in culture to simultaneously achieve vector expansion, and the ability to chose a clone of engineered cells having a single, known (and studied) insertion site.