Phase 2 Study of NV-5138 in Adults With Treatment Resistant Depression

Inclusion Criteria:

• Male or female, aged 18 to 70 years at Screening.

• Diagnosis of Major Depressive Disorder (MDD) according to the Diagnostic andStatistical Manual of Mental Disorders, 5th Edition (DSM-5) for either recurrent orsingle episode MDD without psychotic features that is confirmed by the MiniInternational Neuropsychiatric Interview (MINI).

• Montgomery-Asberg Depression Rating Scale (MADRS) Total Score of ≥26 for the currentMDE at all Screening visits and Baseline (Day 1).

• CGI-S score of ≥4 (moderately ill or worse) at all Screening visits and Baseline.

• History of inadequate response to ≥2 but ≤4 prior ADT therapies (including thecurrent ADT for the current MDE) ≥ 2 weeks at Screening and ≥ 8 weeks at Baseline.

• Stable therapeutic dose of one of the following ADTs for the current MDE for ≥2weeks prior to Screening and maintain the therapeutic dose throughout the study:citalopram, escitalopram, paroxetine, fluoxetine, sertraline, duloxetine,venlafaxine (IR or XR), desvenlafaxine, or vortioxetine.

• Detectable blood level of the approved ADT at Visits 1 and 2 of the ScreeningPeriod.

Exclusion Criteria:

• MADRS Total Score improvement of ≥25% from the highest to the lowest score at anyvisit during the Screening Period.

• Clinically significant abnormal laboratory profiles, vital signs, orelectrocardiograms (ECGs), per Investigator judgment.

• Judged by the Investigator to be at significant risk for suicide, violence, orhomicide; or answers 'Yes' to items 4 or 5 on the Suicidal Ideation section of theC-SSRS at Screening or at Baseline; or has attempted suicide within the 6 monthsprior to Screening.

• History of psychotic disorder, including but not limited to schizophrenia, MDD withpsychotic features, or bipolar I/II disorder with psychotic features.

• History of PTSD, OCD, panic disorder, intellectual disability, autism, acute stressdisorder, or Cluster A or B personality disorder (per DSM-5 criteria).

• Any condition or procedure that may interfere with the absorption, metabolism, orelimination of the study medication (e.g., cholecystectomy or gastric bypass).

• In the Investigator's opinion, is unlikely to comply with the protocol or isunsuitable for any other reason.

• History of alcohol and/or substance use disorder within 6 months prior to Screeningor is currently using or has positive results at Screening for drugs of abuse or hasa positive alcohol result at any Screening or Baseline visit.