Antidepressant Trial With P2X7 Antagonist JNJ-54175446

This trial will be a multi-centre, phase II, randomised, double blinded, placebo-controlled, parallel group trial. The research team estimates that the majority of the participants will be recruited through the trial website, posters and research databases. In order to better assess the suitability of the interested participants, interested participants are required to answer pre-screening questions. Only those who might be suitable to take part will be invited to a screening visit to continue with the rest of the trial screening procedures. The trial will consist of 3 phases - a screening phase, treatment phase of 8 weeks and follow up phase. This includes a total of 6 clinic visits and will be spread over about 15 weeks. Each clinic visit will last between 1.5 hours to 5 hours. Participants will have to be fasted overnight (10 hrs) prior to baseline visit 1 and visit 4 for biomarker blood samples. At these visits, breakfast will be provided after sample collection. The list below outlines the study schedule and key assessments applicable to a participant who passes the pre-screening questions: Screening phase clinic visit Participants who are interested in taking part will be invited to attend a screening visit in the clinic which lasts about 4 hours. At this visit the trial team will discuss the trial further and answer any queries the participants may have. If the participants agree, they will then provide informed consent prior to any screening tests and procedures being undertaken. An alcohol breath test and urine drug screen will be carried out. Urine samples will be taken for urinalysis. Blood samples will be taken for safety assessments including full blood count, clinical chemistry tests, thyroid function tests, pregnancy and Follicle-stimulating hormone test (if applicable). Biomarker blood samples will also be taken for genetic analysis of P2X7 receptor and analysis of C-reactive protein (CRP) for eligibility check, and for other biomarker assays including genetic analysis. Other screening assessments include a review of the participant's medical and medication history, review of their depressive disorder and self-reported stress, and a physical examination. Vital signs will be measured and participants will have an electrocardiogram (ECG) performed. Participants will also be introduced to the other trial activities that will have to be carried out in their homes. This includes collection of saliva samples, the use of activity monitoring device and completion of daily sleep diary. Screening phone call Once results from the genetic analysis of the P2X7 receptor and CRP levels are available (about 1 to 2 weeks after the screening visit), the results will be returned to the site team who will then inform the participant by phone whether they are eligible. If eligible, a baseline clinic visit will be arranged. During this call, eligible participants will be reminded that saliva sample collection packs will be sent in the post, to collect saliva samples at specific time points and return them to the research team. Participants will also be sent an activity monitoring watch and sleep diary; participants should start wearing the watch everyday for at least 7 days prior to baseline visit and record their sleep. Baseline/Treatment phase Visit 1 Participants will be asked to fast a minimum of 10 hours and attend a baseline site visit (Day 1) which would last approximately 5 hours. At this visit, the participant's diagnosis of major depressive episode will be re-checked to ensure they are still eligible. Fasting blood samples will be taken for full blood count, clinical chemistry, biomarkers and baseline drug concentration analysis. After breakfast is given, an alcohol breath test and urine drug screen will be carried out. Urine samples will be taken for urinalysis and pregnancy test (if applicable). An ECG will be performed and vital signs will be assessed. Participants who continue to meet eligibility will be randomised in 1:1 ratio to receive JNJ-54175446 or placebo. Participants will be asked about any adverse events and concomitant therapies. Various clinical and participant reported questionnaires will be completed to assess stress, depression symptoms and suicidal risk. Participants will be asked to complete a range of online cognition tests, during which heart rate variability measurements will be carried out. Participants will also have a baseline MRI scan which includes completion of a cognitive task during the scan. At the end of the visit, participants will receive 1 bottle of allocated trial drug and will be instructed to take 1 capsule every day within 30 minutes after breakfast. A medication diary will be provided to aid participants in recording their daily administration. Data from the activity watch will be downloaded and a new copy of daily sleep diary will be provided. Visit 2 and Visit 3 Participants will be required to attend a visit to the site at Day 14 ± 2 (Visit 2) and at Day 32 ± 3 (Visit 3), each visit will last approximately 3 ½ hours. Participants do not need to be fasted for these visits. On these days, participants should not take their trial drug at home, they will be asked to take the drug at clinic after their blood and urine collection. At this visit, blood samples will be taken for full blood count, clinical chemistry analysis, CRP and drug concentration analysis. A urine drug screen will be carried out. Urine samples will be taken for urinalysis and pregnancy test (if applicable). Participants will then be asked to take their drug. An ECG will be performed and vital signs will be assessed. Participants will be asked about any adverse events and concomitant therapies. Various clinical questionnaires will be carried out to assess stress, depression and suicidal risk. Participants will be asked to complete a range of online cognition tests. Participant's trial drug compliance will be reviewed through review of the medication diary (visits 2 and 3) and physical counting of returned capsules (visit 3). Data will be downloaded from the activity monitoring device at each of these visits and a new daily sleep diary will be provided. At visit 3, participants will receive the 2nd bottle of allocated trial drug. Telephone checks In order to maintain regular contact with the participants, the research team will contact the participants by telephone 8 to 12 days after visit 2 (phone check #1) and 8 to 12 days after visit 3 (phone check #2). Participants will be asked if they have had any adverse events, any changes to concomitant therapies and if they had been able to take the trial drug according to trial instructions. At phone check #2, participants will also be instructed to collect saliva samples within 7 days before the next visit. The saliva collection packs will be posted to the participants. Visit 4 Participants will attend a clinic visit on Day 56 ± 3 (Visit 4) lasting approximately 5 hours. Participants need to come to the site in fasted condition (minimum of 10 hours) and should not take their trial rug at home, they will be asked to take the drug at clinic after blood and urine collection and breakfast. This will be the final dose for the participants. At this visit, fasting blood samples will be taken for full blood count, clinical chemistry analysis, CRP and biomarkers and drug concentration analysis. A urine drug screen will be carried out. Urine samples will be taken for urinalysis and pregnancy test (if applicable). Participant will then be asked to take their drug. An ECG will be performed and vital signs will be assessed. Targeted physical examination will be carried out. Participants will be asked about any adverse events and concomitant therapies. Various clinical and participant reported questionnaires will be completed to assess stress, depression symptoms and suicidal risk. Participants will be asked to complete a range of online cognition tests, during which heart rate variability measurements will be carried out. The anti-depressant response will be assessed using a clinical scale (MADRS). Participants will also have a post-treatment MRI scan which includes completion of a cognitive task during the scan. Data will be downloaded from the activity monitoring device and the device collected from the participants. All unused drug will be collected from the participants. Follow up visit (Visit 5) A follow-up visit will be scheduled between 7 and 14 days after last dose of administration (visit 4) and will last approximately 1 hour. Blood samples will be taken for full blood count, clinical chemistry and CRP analysis. Urine samples will be taken for urinalysis and pregnancy test (if applicable). An ECG will be performed and vital signs will be assessed. Participants will be asked about any adverse events and concomitant therapies. Targeted physical examination and medical review of symptoms and systems will be carried out and body weight measured. Participants will be asked to complete a depression questionnaire. Home-based trial assessments Participants will be requested to wear the activity monitoring device from 7 days prior to visit 1 (Day -7) up until visit 4, and complete a daily sleep diary. This activity monitoring device will record the participant's activity and sleep patterns. Participants have to self-administer 1 capsule of trial drug daily, preferably in the morning and within 30 min after breakfast. The date and time of administration should be recorded in the medication diary. Participants will have to provide 2 sets of 6 saliva samples each during the trial. Data analysis The primary endpoint is the change between baseline score and score at final dose on visit 4 (week 8) assessed by the MADRS scale. 142 participants will be enrolled. All data will be analysed and summarised in a clinical trial report.