Formulation of patient dose of [¹⁷⁷Lu]Lu‐Trastuzumab using in‐house developed freeze‐dried kit: A path forward for clinical translation

Abstract

Trastuzumab is a US‐FDA‐approved humanized monoclonal antibody used for the treatment of human epidermal growth factor receptor 2 (HER2)‐positive breast cancer. The aim of the present work is to optimize a freeze‐dried formulation of DOTA‐Trastuzumab conjugate for the preparation of patient doses of [177Lu]Lu‐Trastuzumab for radioimmunotherapy of breast cancer. The formulation of [177Lu]Lu‐Trastuzumab usually takes a long time, and thus, such a process is not suitable for the routine preparation of this agent in hospital radiopharmacies. To circumvent this, a pre‐synthesized DOTA‐Trastuzumab conjugate as a freeze‐dried formulation is proposed. In the present work, DOTA‐Trastuzumab conjugate was subjected to a freeze‐drying process after the addition of optimized amounts of radioprotectant and cryoprotectant. [177Lu]Lu‐DOTA‐Trastuzumab was prepared by incubating the lyophilized powder of the kit vial with medium‐specific activity 177LuCl3. The final radiochemical purity of [177Lu]Lu‐DOTA‐Trastuzumab, prepared using freeze‐dried kit, was determined to be >95%. To ascertain the reproducibility of the procedure, six consecutive batches of the freeze‐dried formulation were prepared, radiolabeled, and evaluated by carrying out both in vitro and ex vivo studies. The consistency of the results of all the six consecutive batches confirmed the robustness and utility of the in‐house optimized freeze‐dried formulation for the preparation of patient doses of [177Lu]Lu‐Trastuzumab at hospital radiopharmacies.