2'-FLUOROPYRIMIDINE RNA-BASED APTAMERS TO THE 165-AMINO ACID FORM OF VASCULAR ENDOTHELIAL GROWTH-FACTOR (VEGF(165)) - INHIBITION OF RECEPTOR-BINDING AND VEGF-INDUCED VASCULAR-PERMEABILITY THROUGH INTERACTIONS REQUIRING THE EXON 7-ENCODED DOMAIN

Vascular endothelial growth factor (VEGF) has been implicated in the p athological induction of new blood vessel growth in a variety of proli ferative disorders. Using the SELEX process (Systematic evolution of l igands by exponential enrichment), we have isolated 2'-F-pyrimidine RN A oligonucleotide ligands (aptamers) to human VEGF(165). Representativ e aptamers from three distinct sequence families were truncated to the minimal sequence capable of high affinity binding to VEGF (23-29 nucl eotides) and were further modified by replacement of 2'-O-methyl for 2 '-OH at all ribopurine positions where the substitution was tolerated. Equilibrium dissociation constants for the interaction of VEGF with t he truncated, 2'-O-methyl-modified aptamers range between 49 and 130 p M, These aptamers bind equally well to murine VEGF(164), do not bind t o VEGF(121) or the smaller isoform of placenta growth factor (PlGF(129 )), and show reduced, but significant affinity for the VEGF(165)/PlGF( 129) heterodimer. Cysteine 137 in the exon 7-encoded domain of VEGF(16 5) forms a photo-inducible cross-link to a single uridine residue in e ach of the three aptamers. The aptamers potently inhibit the binding o f VEGF to the human VEGF receptors, KDR and Flt-1, expressed by transf ected porcine aortic endothelial cells. Furthermore, one of the aptame rs is able to significantly reduce intradermal VEGF-induced vascular p ermeability in vivo.