This study is testing a new drug called **NMRA-335140** for people with **Major Depressive Disorder (MDD)**, which is a serious condition that makes you feel very sad for a long time. The study has two parts: a **Screening Period** lasting up to 35 days, and a **6-week Treatment Period** where participants will get either the study drug or a placebo (a pill with no medicine). After 6 weeks, if you complete the study and agree, you might be able to join a longer study to keep getting the drug.

To join, you must have MDD confirmed by a test and your current depression symptoms must have been present between 4 weeks to 12 months. You can't join if you've tried a lot of medicines that didn't work, have certain mental health disorders, or have serious problems with alcohol or drugs.

• The study lasts for up to **11 weeks** (including screening).
• You must visit the study site multiple times for check-ups.
• This study is **double-blind**, meaning neither you nor the doctors will know who gets the real drug or placebo.