Age

18–75

Sex

ALL

Healthy volunteers

Not accepted

Male and female participants, ages 18 to 75 years, inclusive, at the time of signing the ICF.
Prior diagnosis of MDD without psychotic symptoms (in the current episode) and have confirmatory diagnosis of current MDD (moderate to severe).
Failure to respond (\<50% improvement) to at least 2-5 antidepressant treatments (including the current treatment)
Currently taking a stable dose of at least 1 but no more than 2 oral antidepressants at baseline

Evidence of unstable medical condition
Concurrent use of any prohibited medications or substance use disorder
Diagnosed bipolar disorder or a psychotic disorder or symptoms
Significant current PTSD symptoms or history of PTSD
Clinically significant current impulse control difficulties
Has a history of hypersensitivity or allergic reaction to ALTO-207 or any of its components/excipients
Concurrent or recent participation in another clinical trial for mental illness involving an investigational product or device

ALTO-207 in Adults With Treatment-resistant Depression (TRD)