A Phase 2 interventional study of ACP-211 and Placebo in Major Depressive Disorder (MDD) and Depressive Disorder, Treatment-Resistant, sponsored by ACADIA Pharmaceuticals Inc.. Recruiting at 28 sites in United States. Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2026-11-05.
Sponsored by ACADIA Pharmaceuticals Inc. · Phase 2, Interventional, and Treatment
The goal of this clinical trial is to learn if ACP-211 can help treat adults with major depressive disorder (MDD) who have not improved with antidepressant therapy (ADT), including those with treatment resistant depression (TRD).
The main questions the study aims to answer are:
3,041 studies on the registry are indexed under Depressive Disorder, Major; 588 are open to participants now.
This study's planned enrollment of 153 is above the median of 79 across 2,530 interventional studies indexed under Depressive Disorder, Major.
Browse Depressive Disorder, Major studies →ACADIA Pharmaceuticals Inc. is the lead sponsor of 41 studies on the registry; 5 are open to participants now.
Of its 26 completed or terminated interventional studies of FDA-regulated products, 24 (92%) have results posted.
Counted across the registry records on this site, refreshed daily.
The criteria were revised on the registry on Nov 5, 2026. See what changed
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Additional inclusion/exclusion criteria apply. Participants will be evaluated at Screening to ensure that all criteria for study participation are met.
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ACP-211 600 mg, administered orally twice weekly
Drug: ACP-211
ACP-211 300 mg, administered orally twice weekly
Drug: ACP-211
Matching placebo, administered orally twice weekly
Drug: Placebo
ACP-211 monotherapy
Placebo control
Change From Baseline in Montgomery-Åsberg Depression Rating Scale (MADRS) Total Score at Day 28
The MADRS is a clinician-rated scale that assesses the severity of depressive symptoms. It consists of 10 items, each scored from 0 (no symptoms) to 6 (severe symptoms), resulting in a total score range of 0 to 60. Higher scores indicate greater depression severity.
Time frame: Baseline and Day 28
Change From Baseline in MADRS Total Score at Day 2
The MADRS is a clinician-rated scale that assesses the severity of depressive symptoms. It consists of 10 items, each scored from 0 (no symptoms) to 6 (severe symptoms), resulting in a total score range of 0 to 60. Higher scores indicate greater depression severity.
Time frame: Baseline and Day 2 (24 hours postdose)
Change From Baseline in MADRS Total Score at Scheduled Postbaseline Visits
Time frame: Baseline through Day 28
Change From Baseline in Clinical Global Impression-Severity (CGI-S) Score at Scheduled Postbaseline Visits
The CGI-S is a clinician-rated assessment of illness severity scored on a 7-point scale ranging from 1 (normal, not at all ill) to 7 (among the most extremely ill). Higher scores indicate greater illness severity.
Time frame: Baseline through Day 28
Proportion of Subjects in Remission at Scheduled Postbaseline Visits (MADRS ≤10)
Time frame: Up to Day 28
Proportion of Subjects With Response at Scheduled Postbaseline Visits (≥50% Reduction From Baseline in MADRS Total Score)
Time frame: Up to Day 28
Proportion of Subjects With Sustained Response From Day 2 Through Day 28
Subjects achieving sustained response, defined as a ≥50% reduction from Baseline in MADRS total score, with onset by Day 2 and maintained through the end of the double-blind treatment period.
Time frame: Day 2 through Day 28
Proportion of Subjects With Clinical Global Impression of Improvement (CGI-I) Score of 1 or 2 at Scheduled Postbaseline Visits
The CGI-I is a clinician-rated assessment of change in illness relative to Baseline. Scores range from 1 (very much improved) to 7 (very much worse). This outcome evaluates subjects with a score of 1 (very much improved) or 2 (much improved).
Time frame: Up to Day 28
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Plan to share: No
No publications or documents are linked to this record.
Started Nov 2025 (actual). Primary completion is estimated for Aug 2027, 21 months after the start.
Of 96 industry-sponsored phase 2 interventional studies under Depressive Disorder, Major, half reached primary completion within 17 months of starting (the median), counting those still running; a quarter within 11 and three quarters within 23. This study's planned 21 months is above that.
Counting every sponsor, half of 195 studies reached it within 22 months; a quarter within 14 and three quarters within 37.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
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