CXCR4 and prostate cancer: Among CXCR4 domain mimetics, POL6326 (known as Balixafortide, developed by Spexis), is an orally bioavailable 14-amino acid macrocyclic peptide that has been investigated for its potential in treating solid tumors such as prostate cancer and HER2-negative metastatic breast cancer, as well as for imaging [91, 92].