ABSTRACT
OBJECTIVE: In the recent time, endoradionuclide therapy for metastatic castration-resistant prostate carcinoma employing 177Lu-PSMA-617 has yielded encouraging results and several clinical trials with the agent are currently ongoing. Routine preparation of 177Lu-PSMA-617 patient doses can be made simpler and convenient, if the ingredients essential for radiolabeling are made available in a ready-to-use lyophilized form. METHODS: PSMA-617 freeze-dried kit was formulated and used for the preparation of 177Lu-PSMA-617 clinical dose with high radiochemical purity using low/medium specific activity 177Lu. Detailed radiochemical studies were performed to determine the maximum activity and volume of 177LuCl3, which can be added in the kit for the formulation of 177Lu-PSMA-617. Studies were also performed to determine the shelf life of the kit to ensure its long-term usage. Studies were performed in buffer as well as human serum medium to determine the stability of the 177Lu-PSMA-617 complex after storing in respective media up to 7 days postpreparation. About ten patient doses of 177Lu-PSMA-617 were administered, and posttherapy scans were acquired. RESULTS: The formulated freeze-dried kit of PSMA-617 could be radiolabeled with an average percentage radiochemical purity > 98.53 ± 0.38. The freeze-dried kit was found suitable for tolerating up to 0.5 mL of 177LuCl3 (in 0.01 N HCl) and specific activity of 555 MBq/µg (15 mCi/µg) for the preparation of the patient dose of 177Lu-PSMA-617. The 177Lu-PSMA-617 complex prepared using the freeze-dried kit of PSMA-617 was observed to maintain % radiochemical purity (RCP) of 96.74 ± 0.87 and 94.81 ± 2.66, respectively, even after storing up to 7 days in buffer and human serum, respectively. 177Lu-PSMA-617 prepared using the in-house formulated freeze-dried kit of PSMA-617 exhibited accumulation in metastatic lesions picked up in a pretherapy PET scan. Reduction in number as well as size of lesions was observed in posttherapy scans acquired after two months of administering the first therapeutic dose of 177Lu-PSMA-617. CONCLUSIONS: The freeze-dried kit of PSMA-617 could be used for the preparation of 177Lu-PSMA-617 with high radiochemical purity (>98%) in a reproducible manner. 177Lu-PSMA-617 prepared using the developed kit was successfully evaluated in patients suffering from metastatic prostate cancer.
Subject(s)
Dipeptides/isolation & purification , Dipeptides/therapeutic use , Heterocyclic Compounds, 1-Ring/isolation & purification , Heterocyclic Compounds, 1-Ring/therapeutic use , Lutetium/isolation & purification , Lutetium/therapeutic use , Prostate-Specific Antigen/isolation & purification , Prostate-Specific Antigen/therapeutic use , Prostatic Neoplasms/radiotherapy , Radioisotopes/isolation & purification , Radioisotopes/therapeutic use , Radiopharmaceuticals/isolation & purification , Radiopharmaceuticals/therapeutic use , Animals , Dipeptides/pharmacokinetics , Drug Compounding/methods , Drug Stability , Freeze Drying , Heterocyclic Compounds, 1-Ring/pharmacokinetics , Humans , In Vitro Techniques , Lutetium/pharmacokinetics , Male , Nuclear Pharmacy/methods , Pharmacy Service, Hospital , Positron Emission Tomography Computed Tomography , Prostate-Specific Antigen/pharmacokinetics , Prostatic Neoplasms/diagnostic imaging , Prostatic Neoplasms/pathology , Prostatic Neoplasms, Castration-Resistant/diagnostic imaging , Prostatic Neoplasms, Castration-Resistant/pathology , Prostatic Neoplasms, Castration-Resistant/radiotherapy , Radiochemistry/methods , Radiochemistry/standards , Radioisotopes/pharmacokinetics , Radiopharmaceuticals/pharmacokinetics , Rats , Rats, Wistar , Tissue DistributionABSTRACT
Lutetium-177-labeled PSMA inhibitor has emerged as a promising modality for targeted therapy of prostate carcinoma. A protocol for regular multidose formulation of ready-to-use 177Lu-PSMA-617 has been developed based on detailed and systematic radiochemical investigations. The formulation meets the requirements of clinical use and can be shipped to nuclear medicine centres for administration up to 4 days from the date of formulation. The reported protocol would be useful toward facilitating widespread clinical utilization of 177Lu-PSMA-617 in the management of prostate cancer.