CXCR4 and melanoma: Finally, CTCE-9908 is a CXCL12 analog that strongly blocks the CXCR4/CXCL12 axis, leading to reduced tumor growth and metastases in various preclinical models including osteosarcoma and melanoma [190], esophageal cancer [95], breast [191, 192] and prostate cancer [193, 194].