The present invention relates to the use of a protein characterized in that it comprises or is constituted by the NOV protein, represented by the sequence SEQ ID NO: 2, or a fragment of this protein, providing that this fragment exhibits an angiogenesis-inhibiting activity, or any sequence derived from the sequence SEQ ID NO: 2 or from a fragment defined above, providing that this derived sequence exhibits an angiogenesis-inhibiting activity, or any sequence homologous to the sequence SEQ ID NO: 2 or to a fragment defined above, providing that this homologous sequence exhibits an angiogenesis-inhibiting activity,for the preparation of a medicament intended for the treatment of pathologies requiring the inhibition of endothelial proliferation or of pathologies requiring the inhibition of endothelial activation.