ENGINEERED FGF‐1 DERIVATIVES LACKING CYSTEINE FOR TREATING CORNEAL ENDOTHELIAL DYSTROPHY

Fibroblast growth factor‐1(FGF‐1) binds and stimulates all members of the FGF class of tyrosine kinase receptors, thus making it a potent agent in tissue regeneration, but its value as a therapeutic is greatly compromised by poor stability and a dependency on heparin as a co‐factor. As the mature form is not exported from cells via the endoplasmic reticulum/Golgi system, its three cysteine residues are all present in reduced form and the presence of these free cysteines limit the biological half‐life of the protein considerably. Substitution of these and other residues has yielded a variety of engineered FGF‐1 derivatives with greatly improved stability and pharmaceutical properties (1), We have tested two of these derivatives, in which the Cys residues have been eliminated, for their ability to stimulate proliferation of corneal endothelial cells as a potential treatment of corneal endothelial dystrophies, such as Fuch's Dystrophy, a condition that leads to the deterioration of the endothelial layer on the back side of the cornea and can only be presently treated effectively by corneal transplants. THX 1011 is a triply substituted derivative in which the Cys at 16, 83 and 117 have been substituted by Val and THX 1114 has the Cys at 16 and 117 changed to Ser and Val, respectively, with the Cys at 83 converted to an internal disulfide bond by mutating the Ala at 66 to Cys. As compared to native FGF‐1 both derivatives were more active stimulators of proliferation of primary cultures of corneal endothelial cells from rabbits or humans with THX 1114 being an order of magnitude more potent than THX 1011. TTHX1011 potently accelerated the regeneration of the corneal endothelium in vivo following cryogenic injury in the rabbit. These data suggest that eFGF‐1s may be a useful therapeutic for corneal endothelial dystrophies. Support or Funding Information Trefoil Therapeutics LLC