NGF and neurodegenerative disease: Small peptide aldehydes had long been used as proteasome inhibitors, further development of these compounds as antibacterial, anticancer, or other therapeutic reagents have also been reported, e.g., fellutamide B was used to reveal the connection of proteasome inhibition and nerve growth factor (NGF) production, which could have potential for the treatment of neuronal injury and neurodegenerative diseases [15,16,17].