Brain-derived neurotrophic factor—a protein belonging to the neurotrophin family that supports neuronal survival, promotes the growth and differentiation of new neurons (neurogenesis), and facilitates synaptic plasticity. BDNF is concentrated in the hippocampus and cortex, brain regions critical for learning and memory.

Low BDNF levels are associated with depression, neurodegenerative diseases, and cognitive decline. Exercise is the most well-established BDNF enhancer in humans. Several peptide compounds modulate BDNF in preclinical studies: Semax increases BDNF expression in rodent brain tissue, Selank affects BDNF-related signaling, and P21 peptide was designed to mimic BDNF’s neurotrophic effects through a different receptor pathway. The gap between preclinical BDNF modulation and clinically meaningful cognitive outcomes in humans remains the central challenge for all of these compounds.