Improved small scale production of iodine-124 for radiolabeling and clinical applications

This work describes a small-scale production of iodine-124 using a 16.5 MeV cyclotron, and a subsequent validation of the formulated sodium [124I]iodide solution for routinely clinical applications.

Iodine-124 (¹²⁴I) was produced via the ¹²⁴Te(p, n)¹²⁴I reaction using a 16.5 MeV GE PETtrace® cyclotron. Irradiation was performed with a pre-prepared solid target consisting of [¹²⁴Te]TeO₂ (99.93%) and Al₂O₃. Different layer thicknesses, irradiation and extraction parameters were tested. After irradiation at the cyclotron, the shuttle with irradiated material was transferred fully automatically via a tube system to the Comecer ALCEO^® Halogen 2.0 extraction unit. Iodine-124 was subsequently extracted in form of sodium [¹²⁴I]iodide ([¹²⁴I]NaI) in 0.05 N aqueous NaOH solution, followed by reconstitution and validation for preclinical and clinical uses.

Good result was achieved using a beam degradation foil of 500 µm thickness in combination with beam currents between 10 and 15 µA. Under these conditions, up to 150 MBq no-carrier-added [¹²⁴I]NaI was obtained after a 2 h irradiation time in less than 500 µl 0.05 N NaOH. Isolation of [¹²⁴I]NaI, including evaporation and extraction at the ALCEO^® Halogen EVP unit was accomplished in 90 min 24 h after production (irradiation), the amount of iodine-123 as assessed by gamma-ray spectroscopy was less than 1.5%. The undesirable iodine-125 was not detectable by gamma spectroscopy. The extracted [¹²⁴I]NaI could be used directly for radiolabeling purposes, and after buffering with phosphate buffered saline (PBS) and sterile filtration for clinical applications.

Through the optimized conditions for irradiation and extraction, iodine-124 was produced in good radiochemical yields and high radionuclide purity. The generated injectable [¹²⁴I]NaI solution was sterile, non-pyrogenic and ready for preclinical and clinical applications after a sterile filtration through a 0.22 µm membrane filter.