On the preparation of a therapeutic dose of 177Lu-labeled DOTA-TATE using indigenously produced 177Lu in medium flux reactor

Lu-177 could be produced with a specific activity of similar to 23,000 mCi/mg (850 GBq/mg) by neutron activation using enriched Lu-176 (64.3%) target when irradiation was carried out at a thermal neutron flux of 1 X 1014 n/cm(2)/s for 21 d. Lu-177-DOTA-TATE could be prepared in high radiochemical yield (similar to 99%) and adequate stability using the Lu-177 produced indigenously. The average level of radionuclidic impurity burden in Lu-177 due to Lu-177m was found to be 250 nCi of Lu-177m/1 mCi of Lu-177 (9.25kBq/37MBq) at the end of bombardment, which corresponds to 0.025% of the total activity produced. The maximum specific activity achievable via careful optimization of the irradiation parameters was found to be adequate for the preparation of a therapeutic dose of the radiopharmaceutical. The in-house preparation of this agent using 25 mu g (17.41 nmole) of DOTA-TATE and indigenously produced Lu-177 (0.8 mu g, 4.52 nmole), corresponding to peptide/Lu ratio of 3.85 yielded 98.7% complexation. Allowing possibility of decay due to transportation to users, it has been possible to demonstrate that at our end, a single patient dose of 150-200 mCi (5.55-7.40 GBq) can be prepared by using 250-333 mu g of DOTA-TATE conjugate. This amount compares well with 177Lu-DOTA-TATE prepared for a typical peptide receptor radionuclide therapy (PRRT) procedure which makes use of 100 mu g of the DOTA-TATE conjugate, which incorporates 50mCi (1.85GBq) of Lu-177 activity, thereby implying that in order to achieve a single patient dose of 150-200mCi (5.55-7.40GBq), 300-400 mu g of the conjugate needs to be used. (c) 2006 Elsevier Ltd. All rights reserved.