Targeting 124I to the DNA of tumours for PET Imaging and Auger-Radiotherapy

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The aim of this project is to develop a new method of targeting radioactivity to tumours, for detection and treatment, using a radioactive element (iodine-124). Iodine-124 emits a form of radiation called positrons, detected by a new imaging technique - Positron Emission Tomography (PET). Therefore, tumours labelled with iodine-124 can be imaged by PET. Also, iodine-124 is amongst a class of radioactive atoms (called Auger-emitters) that emit a shower of very low energy electrons. This intense focus of radiation damage, can be exploited to kill cancer cells by inflicting lethal DNA damage. To bring the iodine-124 close to the DNA molecule, we will attach it to a DNA-binding drug linked to a tumour-seeking protein, such as an anti-tumour antibody. After injection of the radioactive drug-protein cocktail, PET imaging will be used to assess the extent of tumour targeting, to enable calculation of the amount of cocktail required for successful tumour treatment by further injections. There are some situations where tumour imaging needs to be non-damaging, such as in using PET imaging to assess the success of surgical removal of a tumour. Therefore, we will design an alternative version of the iodine-124-labelled DNA- binding drug with the radioactive atom in a location that will minimise DNA damage from radioactive decay. In this imaging-only scenario, the Auger-emission feature is suppressed whilst still exploiting positron-emission for imaging. The stability of radioactive atoms varies widely, and the half-life of iodine-124 (about four days) is an ideal compromise for imaging and treatment. By contrast, the utility of the most commonly used isotope for PET imaging, fluorine-18, is limited by its half-life of only a few hours. The PET Centre at PeterMac will soon produce iodine-124, joining one of only a few centres throughout the world. Peter Mac has recently lodged a patent application for the technology to be developed in this project.