[en] Objective: The main objectives of this work were to obtain ¹⁷⁷Lu-DOTA-Minigastrin with high radiochemical purity (RP) and specific activity (SA) as high as possible, using locally produced medium SA ¹⁷⁷LuCl3 (range 6,36-9,73 Ci/mg of ¹⁷⁶Lu), and to carry out in vitro and in vivo stability tests. Materials and methods: For a typical labelling, 20 or 15 μg of DOTA-MG (pi Chem, Austria) dissolved in ammonium acetate buffer pH 6 were mixed with 1mCi of ¹⁷⁷LuCl3 (SA = 6,36, 7,52 y 9,73 Ci/mg). The solution was incubated for 30 min. at 80 C degrees (pH 5,5). The stability assays in saline (SS) were carried out by incubation of the radiopharmaceutical with SA of 0.05 mCi/ μg of peptide in 80 μ of SS for 24 and 48 h at room temperature. The stability assays in human serum (HS) were carried out by incubation of 2.5 μ of ¹⁷⁷Lu-DOTA-MG with SA of 0.05 mCi/ μg of peptide in 500 μl of HS for 15 min. and 2 h at 37 C degrees. The samples were centrifuged at 3000 xg for 5 min. The supernatant (SN) was taken and acetonitrile (ACN) was added in a ratio 2:3 (SP:ACN). The solution was centrifuged at 3000 xg for 5 min. and the resulting supernatant was concentrated by ultra-filtration (Vivaspin 500, Sartorius). The concentrated SN was analyzed by Reverse Phase High Performance Liquid Chromatography (RP-HPLC) in order to determine the radiochemical purity. The serum protein binding was calculated taking into account the relation between the pellets activity in respect to the total activity. Bio distributions of ¹⁷⁷Lu-DOTA-MG in normal mice were done at 15 and 30 min., 1 and 4 h p.i. The results were expressed as percentage of injected activity per gram of tissue (%IAgr). Results: 20 μg of peptide were labelled with different SA ¹⁷⁷LuCl3 (6,36, 7,52 and 9,73 Ci/mg of ¹⁷⁶Lu) resulting in high radiochemical purities 96,31 %, 98,95 % and 97.57 %, respectively (SA 0.05 mCi/μg of peptide). 15 ug of peptide were labelled with ¹⁷⁷LuCl3 (SA 7,52 Ci/mg of ¹⁷⁶Lu) obtaining a final SA of 0.066 mCi/ μg of peptide. The radiochemical purity was higher than 90 %. The radio chromatogram of the labelled peptide sample showed two peaks. The main peak had a retention time (RT) between 11,9-12,2 min. The lower peak at RT 11,6 min. belong to a aminoacid methionin oxidated specie. The stability studies in HS showed that the lower peak was growing with the incubation time since 22,2% at 15 min. until 68,9% at 24 h. On the other hand, the percentage of free ¹⁷⁷Lu was constant with the incubation time in HS. In the case of SS stability for the radiopharmaceutical with S.A. 0,066, the 11.6 min peak growing rate was lower than the mentioned above but the percentage of free ¹⁷⁷Lu was higher than before (aprox. 10 % of free ¹⁷⁷Lu). The protein binding for the incubation of labelled peptide in HS was 21,1 % at 15 min. and 23,55 % at 2 h. Bio distributions studies in normal mice showed a fast blood clearance 1,5% IA/g at 30 min p.i and fast renal excretion 9,44 and 2,31 % IA/g at 30 min and 4 h p.i, respectively. It was observed a high accumulation in intestine at 4 h p.i. Conclusion: High RP (≥95,0 %) ¹⁷⁷Lu-DOTA-MG with different final SA (0,05 and 0,066 mCi/μg of peptide) was obtained using medium SA ¹⁷⁷Lu (6,36-9,73 Ci/mg of ¹⁷⁶Lu) locally produced (Research Reactor RA-3, Centro Atomico Ezeiza). One oxidated specie of the labelled peptide was observed as a chromatogram peak at RT 11,6 min. This peak grew up fast between 24 and 48 h post labelling. Although this oxidation process did not affect the complexation of ¹⁷⁷Lu with the DOTA-MG. The stability of the product at 15 min and 2 h showed a chromatographic shape similar to SS stability. Bio distributions studies showed a fast blood clearance and renal excretion, but a high accumulation in intestine. It will be necessary to carry out studies at later times in order to confirm this performance. At the moment It was carrying out dosimetric studies in normal mice and posterior extrapolation to humans. In the near future, It was expected to make radiolabelling and receptor binding assays with higher SA ¹⁷⁷Lu than before. (author)