[en] Integrin αvβ3 has a critical role in tumor angio genesis and metastasis. Radiolabelled peptides based on the Arg-Gly-Asp (RGD) sequence have been reported as radiopharmaceuticals with high affinity and selectivity for the αvβ3 integrin. The aim of this study was to label c-DOTA-RGD and c-DOTA-RGDf peptides with ¹⁷⁷Lu and to evaluate their in vitro and in vivo stability as potential specific therapeutic radiopharmaceuticals. Labelled was carried out by direct reaction of ¹⁷⁷LuCl₃ with c-DOTA-RGD peptides in 1 M acetate buffer ph 5.5 at 90^o C for 30 min. Radiochemical purity and stability studies were realized by reversed phase HPLC and I TLC-Sg analyses in human serum and saline solution. Biological recognition was performed using MCF7 tumor cells (positive αvβ3) and in athymic mice with induced MCF7 tumors. Molecular mechanics and quantum mechanics calculations were performed to explain experimental results associated with the molecular recognition. ¹⁷⁷Lu-DOTA-RGD and ¹⁷⁷Lu-DOTA-RGDf were obtained with radiochemical purities > 95%, showing adequate in vitro and in vivo stability and specific binding to □_v□₃ receptors. (Author)