GFRA4 and medullary thyroid gland carcinoma: The response to GFRα4 is now under study in humans: NCT04877613 is an open-label phase 1 study aimed to assess the safety of different doses of GFRα4 CAR-T cells in adult patients with recurrent/metastatic MTC (progressive after at least one prior TKI-containing regimen, or in patients that were intolerant to or declined such therapy).