The present invention relates to a biocompatible polymer composition, suitable for in vivo vessel repair, comprising a matrix pre-polymer, a filler and a curing agent, wherein said composition wherein said biocompatible polymer composition is curable in the presence of a curing catalyst at 37.degree. C. to form a cured material with an elongation until rupture of at least 5% and an elastic modulus of at least 1 MPa.