In 1999,a C19 peptide was found by phage display to show substantial FGFR1-bindingand even strong FGFR agonist action when dimerized by the c-Jun leucinezipper.38 However, an Fc-fusion of theC19 peptide did not show such mitogenic potential, making it a suitableconstruct for potential targeting of FGFR-expressing cancer cells.Taking advantage of the high affinity of the C19 peptide toward FGFR1,we want to investigate if it can be used as a delivery vehicle fora highly cytotoxic drug, monomethyl auristatin E (MMAE). Here, FGFR1 is linked to cancer.