<p>This study is devoted to investigating the synthesis of a lyophilized kit (LK) based on the peptide ligand DOTA-TATE, which is used for the preparation of the radiopharmaceutical “[¹⁷⁷Lu]Lu-DOTA-TATE, for injection”. This radiopharmaceutical is applied in specialized nuclear medicine clinical laboratories for the treatment of patients with gastroenteropancreatic (GEP) neuroendocrine tumors (NETs). The radiopharmaceutical was prepared by adding the required activity of the [¹⁷⁷Lu]LuCl₃ precursor to the lyophilized kit, followed by incubation under controlled conditions. During the preparation of the lyophilized kit [DOTA-TATE], the amount of the peptide ligand DOTA-TATE was fixed at 100&#xa0;µg per vial. The quantities of the stabilizing agents, ascorbic acid and L-cysteine, were varied in the ranges of 20–150&#xa0;mg/vial and 0.2–1.2&#xa0;mg/vial, respectively. The molar ratio of the peptide ligand DOTA-TATE to the [¹⁷⁷Lu]LuCl₃ precursor used for the synthesis of the radiopharmaceutical “[¹⁷⁷Lu]Lu-DOTA-TATE, for injection” was varied from 2:1 to 6:1 in order to determine the optimal labeling conditions. The optimal composition of the lyophilized kit components was established with DOTA-TATE/ascorbic acid/L-cysteine contents of 100&#xa0;µg/50&#xa0;mg/1.0&#xa0;mg per vial. The preparation of the radiopharmaceutical “[¹⁷⁷Lu]Lu-DOTA-TATE, for injection” with high specific activity and high radiochemical purity was achieved at a peptide ligand DOTA-TATE to radionuclide ¹⁷⁷Lu ratio of 4:1 in the lyophilized kit. The synthesized lyophilized kit [DOTA-TATE] enables the preparation of the radiopharmaceutical “[¹⁷⁷Lu]Lu-DOTA-TATE, for injection” with high quality characteristics directly in clinical settings. The radiopharmaceutical is obtained by adding the required activity of the precursor substance “Lutetium chloride [¹⁷⁷Lu]LuCl₃, no-carrier-added” to the lyophilized kit [DOTA-TATE] at activities up to 10.2 GBq, followed by administration of the freshly prepared radiopharmaceutical to patients.</p>