A stromal cell-derived factor 1 (SDF-1; CXCL12) analog and inhibitor of C-X-C chemokine receptor type 4 (CXCR4), with potential antineoplastic activity. Upon administration, PTX-9908 selectively targets and binds to CXCR4, thereby preventing the binding of CXCR4 to its ligand SDF-1. This inhibits receptor activation and results in decreased proliferation and migration of CXCR4-overexpressing tumor cells. The G protein-coupled receptor CXCR4, which is overexpressed in several tumor cell types, promotes tumor angiogenesis, tumor cell proliferation, survival, invasion and metastasis. SDF-1, a major chemotactic factor, plays a key role in mediating cell trafficking via selective binding to CXCR4.