Impaired migration and lung invasion of human melanoma by a novel small molecule targeting the transmembrane domain of death receptor p75.

Receptor transmembrane domains (TMDs) are crucially involved in relaying ligand information from extracellular to intracellular spaces and represent attractive targets for small molecule manipulation of receptor function. Screening a library of over 8000 drug-like compounds with an assay based on the TMD of death receptor p75, we identified a novel small molecule capable of inhibiting p75-mediated migration of human melanoma cells. Employing medicinal chemistry, a more potent derivative termed Np75-4A22 was identified that blocked nerve growth factor (NGF)-mediated melanoma invasion at sub-micromolar concentrations. The specific interaction of Np75-4A22 with the p75 TMD was confirmed by 2D NMR. Mechanistically, Np75-4A22 was found to antagonize NGF-mediated recruitment of the actin-bundling protein fascin to p75, fascin association with the actin cytoskeleton and filopodia formation. Importantly, preclinical assessment of Np75-4A22 showed high oral bioavailability, low toxicity, and significant inhibition of melanoma lung invasion in mice. These results support further development of this approach as an alternative or complementary strategy for melanoma cancer patients that do not respond to conventional chemotherapy or immune checkpoint inhibitors.