WRG-28 is a selective, extracellularly acting DDR2 allosteric inhibitor with an IC50 of 230 nM. WRG-28 uniquely inhibits receptor-ligand interactions via allosteric modulation of the receptor. WRG-28 inhibits tumor invasion and migration, as well as tumor-supporting roles of the stroma, and inhibits metastatic breast tumor cell colonization in the lungs by targeting DDR2.