Alto Neuroscience, Inc. operates as a clinical-stage biopharmaceutical company in the United States. Its product pipeline comprising ALTO-100, which is in phase 2b clinical trial for the treatment of patients with major depressive disorder (MDD); and which is in phase 2a clinical trial for the treatment of post-traumatic stress disorder. The company 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 MDD; ALTO-101, a novel small molecule phosphodiesterase 4 inhibitor which is in phase 1 clinical 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 1 clinical 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 which is in phase 1 clinical trial for the treatment of MDD. In addition, it develops novel pharmacodynamically synergistic combination and biomarker platform that collects patient-specific data to identify biomarker-characterized patient. The company was incorporated in 2019 and is headquartered in Los Altos, California.