Recent Developments in PET and SPECT Radiotracers as Radiopharmaceuticals for Hypoxia Tumors

Hypoxia, a deficiency in the levels of oxygen, is a common feature of most solid tumors and induces many characteristics of cancer. Hypoxia is associated with metastases and strong resistance to radio- and chemotherapy, and can decrease the accuracy of cancer prognosis. Non-invasive imaging methods such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) using hypoxia-targeting radiopharmaceuticals have been used for the detection and therapy of tumor hypoxia. Nitroimidazoles are bioreducible moieties that can be selectively reduced under hypoxic conditions covalently bind to intracellular macromolecules, and are trapped within hypoxic cells and tissues. Recently, there has been a strong motivation to develop PET and SPECT radiotracers as radiopharmaceuticals containing nitroimidazole moieties for the visualization and treatment of hypoxic tumors. In this review, we summarize the development of some novel PET and SPECT radiotracers as radiopharmaceuticals containing nitroimidazoles, as well as their physicochemical properties, in vitro cellular uptake values, in vivo biodistribution, and PET/SPECT imaging results.

Automated summary

Hypoxia, a common feature of solid tumors, can induce many cancer characteristics and is associated with metastases and resistance to therapy. Non-invasive imaging methods using hypoxia-targeting radiopharmaceuticals have been used for tumor hypoxia detection and therapy. Nitroimidazoles, which can selectively bind to intracellular macromolecules under hypoxic conditions, have been the focus of PET and SPECT radiotracer development for imaging and treatment of hypoxic tumors. This review summarizes the development of novel PET and SPECT radiotracers containing nitroimidazoles, including their physicochemical properties, cellular uptake values, biodistribution, and imaging results.