Alto Neuroscience, Inc. operates as a clinical-stage biopharmaceutical company in the United States. The company's product pipeline includes ALTO-100, which is in Phase 2b clinical trial for the treatment of patients with bipolar depression (BPD). It also develops ALTO-300, a small molecule melatonergic agonist and serotonergic antagonist with antidepressant properties, which is in Phase 2b clinical trial to treat patients with major depressive disorder (MDD); ALTO-101, a novel small molecule phosphodiesterase 4 inhibitor that is in Phase 2 proof-of-concept (POC) trial for the treatment of cognitive impairment associated with schizophrenia; ALTO-203, a novel small-molecule histamine H3 receptor inverse agonist, which is in Phase 2 POC trial to treat patients with MDD and higher levels of anhedonia; and ALTO-202, an investigational orally bioavailable antagonist of the GluN2B subunit of the NMDA receptor that is in Phase 1 clinical trial for the treatment of MDD. The company was incorporated in 2019 and is headquartered in Mountain View, California.