CXCL12 and small cell lung carcinoma: In a phase II study (NCT01439568 [22]) of LY2510924, a cyclic peptide that blocks the binding of the ligand SDF-1 (CXCL12) to CXCR4 [16, 21], there was no difference in median PFS for patients with ED-SCLC treated with LY2510924 plus CE and CE [23].