This study is testing a new medicine called NMRA-335140 to see if it helps people with Major Depressive Disorder (MDD) feel better. MDD is a condition where someone feels very sad and loses interest in daily life. The study will last for about 6 weeks, during which some people will get the real medicine and some will get a placebo—a pill that looks the same but has no medicine in it. Nobody, not even the doctors, will know who gets which pill. Before the study starts, there's a Screening Period of up to 28 days to check if you're eligible. If you finish the study and agree, you might be able to join an extension study.

• Study lasts up to 6 weeks, with extra time for screening.
• Participants receive either the test medicine or a placebo.
• To join, you must have had MDD symptoms for more than 4 weeks.