This clinical trial is focused on studying Major Depressive Disorder (MDD), a condition characterized by persistent feelings of sadness and loss of interest. The study specifically targets individuals with moderate-to-severe anhedonia, which is a reduced ability to feel pleasure, and who have not responded adequately to their current antidepressant treatments. The trial will test a new medication called Aticaprant, which is taken as a tablet, to see if it can help improve symptoms when used alongside existing antidepressant medications.

The purpose of the study is to evaluate how effective and safe Aticaprant is in improving depressive symptoms in adults with MDD. Participants will be randomly assigned to receive either Aticaprant or a placebo, in addition to their current antidepressant. The study will be conducted in a double-blind manner, meaning neither the participants nor the researchers will know who is receiving the actual medication or the placebo. This helps ensure the results are unbiased. The study will last for a period of 43 days, during which participants will be closely monitored for any changes in their symptoms and overall health.

After the initial study period, there will be an open-label extension phase where all participants will have the opportunity to receive Aticaprant. This phase allows researchers to gather more information about the long-term effects and safety of the medication. Throughout the study, participants will undergo regular assessments to track their progress and any side effects they may experience. The ultimate goal is to determine if Aticaprant can be a beneficial addition to current treatment options for those struggling with MDD and anhedonia.