Folate-based radiotracers for nuclear imaging and radionuclide therapy

Folate receptor α (FRα) is overexpressed on numerous tumorous cell types such as ovarian or endometrial cancer cells. Moreover, FRα is absent from most healthy tissues as it is normally expressed only on the surface of proximal tubules cells of kidneys and choroid plexus. Thus, folate-based radiopharmaceuticals have emerged this last two decades as FRα is a target of choice to diagnose and treat numerous cancers. Nuclear imaging is a performing diagnostic technology using highly sensitive detectors and specific radiopharmaceuticals used to detect tumors at an earlier stage. Herein, an overview of the development of folate-based radiopharmaceuticals to detect FRα-positive tumors by nuclear imaging using positron emission tomography (PET) and single photon emission computed tomography (SPECT) is exposed. Strategies developed to improve precursor synthesis, bioavailability, clearance, and affinity to FRα will be detailed. Advances made to decrease kidney uptake open the gate to targeted radionuclide therapy (TRT) using folate-based radiopharmaceuticals to treat FRα-positive tumors. Thus, radiofolates used in TRT and more precisely in a theranostic approach will be depicted in this review.