In contrast to free oligo‐FdU, intravenous administration of T22‐GFP‐H6‐FdU selectively accumulates and internalizes in CXCR4+ cancer cells, triggering DNA damage and apoptosis, which leads to the selective depletion of CXCR4+ MetSCs and to reduced tumor formation and spheroid formation. Here, CXCR4 is linked to cancer.