ACP-211 Monotherapy for Major Depressive Disorder With Inadequate Antidepressant Response

This study is testing ACP-211, a new drug, in adults with major depressive disorder (MDD) who have not responded well enough to at least two different antidepressants — sometimes called treatment-resistant depression. **You may be eligible if...** - You are between 18 and 65 years old - You have a clinical diagnosis of major depressive disorder (MDD) - You have not had an adequate response to at least 2 antidepressants, including at least one failure during your current depressive episode - You are currently taking an approved antidepressant at a stable dose - Your depression symptoms are severe based on standard rating scales (MADRS ≥28, CGI-S ≥4, QIDS-SR16 ≥16) - If you can become pregnant, you have a negative pregnancy test and agree to use contraception; males must use barrier protection **You may NOT be eligible if...** - You have certain personality disorders or persistent depressive disorder - You have had a recent substance use disorder (excluding caffeine or nicotine) - You are pregnant or unwilling to use contraception - You do not meet the severity thresholds on the depression rating scales Talk to your doctor to see if this trial is right for you.