The goal of this clinical trial is to learn if DT-101 can treat depression in adults. The effect of DT-101 will be compared to placebo. Subjects will attend the clinic every couple of weeks complete general health checks and complete questionnaires.

The purpose of this study is to compare DT-101 and placebo in adult participants with MDD. The study will also evaluate how safe and well tolerated the study drug is. The clinical study staff will check participants' suitability to take part in the clinical research study by performing physical and neurological examinations, obtaining blood and urine samples, conducting clinical assessments and reviewing medical and treatment history. These tests and assessments will continue throughout the study with the purpose of checking the participants' ongoing suitability and to collect data to analyze the effect that DT-101 may have on their depression symptoms. Participants will also have blood samples taken to allow analysis of how DT-101 is absorbed and used by the body (PK sampling), some blood samples may be retained in order to perform future research that may be useful when looking at whether genetics affects how a person responds to DT-101 (PGx sampling)

Inclusion Criteria:

• The participant is able to read, understand and communicate in the local language used at the study site, and is willing to provide written informed consent
• Male or female (assigned at birth, inclusive of all gender identities) participant must be 18 to 75 years of age, inclusive at the time of signing the informed consent.
• Has recurrent depression (defined as at least one prior episode excluding the current one), as diagnosed by DSM 5-TR (Diagnostic and Statistical Manual of Mental Disorders, 2022).

Exclusion Criteria:

• Pregnant or breastfeeding or plans to become pregnant during the study.
• Unstable medical condition or unstable chronic disease.
• Significant neurological abnormality.
• History of moderate or severe alcohol or drug use disorder as per DSM-5-TR in the 6 months prior to Screening.
• History of seizure.
• In the investigator's opinion, the participant is not capable of adhering to the protocol requirements.