The recently added PD 90780 (Axon 2174) is an inhibitor of NGFs binding to the P75 NGF-receptor, a.k.a. Low-Affinity Nerve Growth Factor Receptor (RTK class VII, Trk receptor family). In general, mature NTs bind preferentially to Trk and p75NTR, whereas proneurotrophins, which contain an N-terminal domain proteolytically removed in “mature” forms, interact with p75NTR and through their N-terminal domains, with the sorting receptor sortilin. p75NTR interacts with Trks and modulates Trk signaling but is also independently coupled to various prosurvival and proapoptotic signaling systems. Depending on the operative ligands, co-expression of Trk or other receptors, and expression of downstream signaling elements, p75NTR promotes cell survival or death and modulates neurite outgrowth[1].