Brain-derived neurotrophic factor (BDNF) is a growth factor derived from the brain that binds to TrkB receptors, regulating neuronal growth, survival, and synaptic function. PG-003, an alternative peptide to BDNF, is a chemically-synthesized homodimeric cyclic peptide with specific binding ability against the TrkB receptor.

Upon binding, PG-003 induces dimerization of the TrkB receptor, triggering subsequent signaling events in cells as a TrkB agonist. It should be noted that PG-003 is believed to have no binding or agonistic activity towards the p75 receptor, which is a low-affinity nerve growth factor receptor that binds to BDNF.The molecular weight of PG-003 is 5151.66 (acetate), and 10 µg of PG-003 exhibits equivalent activity to 25 µg of human BDNF.