NLX-266 is a biased agonist of the serotonin 5-HT<sub>1A</sub> receptor. It acts specifically as a very-high-affinity and selective ERK1/2-biased serotonin 5-HT<sub>1A</sub> receptor agonist (K<sub>i</sub> = 0.0447nM; = 0.437nM; = 94%), with selectivity for ERK1/2 signaling over multiple other pathways. The drug produces antidepressant- and antiparkinsonian-like effects in rodents, with much greater efficacy than certain other serotonin 5-HT<sub>1A</sub> receptor agonists like buspirone and gepirone. It shows favorable pharmacokinetics in rodents. The chemical synthesis of NLX-266 has been described. NLX-266 was developed by Neurolixis. It was first described in the scientific literature in 2025.