Alto Neuroscience, Inc. operates as a clinical-stage biopharmaceutical company that engages in the psychiatry drug development business. The company develops ALTO-100 for the treatment of patients with major depressive disorder (MDD) and post-traumatic stress disorder; ALTO-300, a small molecule melatonergic agonist and serotonergic antagonist with antidepressant properties to treat patients with MDD; and ALTO-101, a novel small molecule phosphodiesterase 4 inhibitor for the treatment of cognitive impairment associated with schizophrenia. It also develops ALTO-203, a novel small-molecule histamine H3 receptor inverse agonist 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 for the treatment of MDD. In addition, the company develops novel pharmacodynamically synergistic combinations and an AI-enabled biomarker platform that combine sources of information on patients brain activity and behavior to identify patients to respond to novel product candidates. Alto Neuroscience, Inc. was incorporated in 2019 and is based in Los Altos, California.