ALTO-300 in Depression (ALTO-300-004)

To understand the relationship between baseline biology and change in the Montgomery-Asberg Depression Rating Scale (MADRS) with ALTO-300

The Montgomery-Åsberg Depression Rating Scale (MADRS) measures the severity of depression where smaller scores indicate less depression and higher scores suggest more severe depression. Possible scores for this 10 item version range from 0 to 60. The change from baseline to the end of the study is the primary outcome.

Time frame: Measured 6 times over 8 weeks

To understand the relationship between baseline biology and change in the Clinical Global Impression scale - Severity (CGI-S) with ALTO-300

The Clinical Global Impression scale - Severity (CGI-S) measures the severity of psychopathology in general where smaller scores indicate less illness and higher scores suggest more severe illness. Possible scores for this scale range from 1 to 7. The change from baseline to the end of the study is the primary outcome.

Time frame: Measured 6 times over 8 weeks

Number of Participants with Adverse Events (AEs) as a Measure of Safety and Tolerability of ALTO-300

An adverse event is any untoward medical event that occurs in a participant administered an investigational product, and it does not necessarily indicate only events with clear causal relationship with the relevant investigational product.

Time frame: From the signing of the ICF until the follow-up visit (up to 12 weeks)

Number of Participants With Clinically Significant Vital Signs Abnormalities as a Measure of Safety and Tolerability of ALTO-300

Vital signs measured include blood pressure, heart rate, respiratory rate, temperature, and weight.

Time frame: From the signing of the ICF until the end-of-treatment visit (up to 11 weeks)]

Number of Participants With Clinically Significant Laboratory Abnormalities as a Measure of Safety and Tolerability of ALTO-300

Blood samples for serum chemistry and hematology will be collected for clinical laboratory testing.