The overarching hypothesis of this study is that brexpiprazole (BREX) (2 or 4 mg/day), relative to placebo, will reduce alcohol consumption and modulate the neural substrates of moderate-severe Alcohol Use Disorder (AUD), and that genotype at a variable number tandem repeat polymorphism (VNTR) in the DAT1/SLC6A3 gene will predict BREX effects. Participants will be non-treatment-seeking AUD individuals, and will be prospectively randomized to medication on the basis of their DAT1 VNTR genotype. Since BREX affects both cortical and striatal neurophysiology, the investigators will use functional magnetic resonance imaging (fMRI) to test its effects on cortical (right inferior frontal gyrus; rIFG) activation associated with response inhibition and on striatal activation elicited by alcohol cues, and will explore whether either of these measures mediates BREX effects on drinking in the natural environment vs. a bar-lab setting, which may reflect different aspects of lost control over drinking.
Aim 1: Test BREX effects on inhibition-related cortical activation and alcohol cue-elicited striatal activation, and evaluate whether DAT1 VNTR genotype predicts these effects.
Hypothesis 1: There will be a linear effect of BREX dose, relative to placebo, in increasing inhibition-related rIFG activation and reducing cue-elicited ventral striatum (VS) activation, and these effects will be greater among DAT1 9R carriers than 10R homozygotes.
Aim 2: Test BREX effects on drinking in the natural environment and alcohol self-administration in the bar lab, and evaluate whether DAT1 VNTR genotype predicts these effects.
Hypothesis 2: There will be a linear effect of BREX dose, relative to placebo, in reducing natural drinking and alcohol self-administration, and these effects will be greater among DAT1 9R carriers.
Aim 3: Test inhibition-related cortical activation and cue-elicited VS activation as mechanisms of action for BREX's effects on natural and bar-lab drinking.
Hypothesis 3: Cue-elicited VS activation will mediate BREX effects on natural drinking, while inhibition-related rIFG activation will mediate its effects on bar-lab drinking.
This study will recruit up to 250 study participants with Alcohol Use Disorder (AUD) who are not seeking treatment for AUD. Individuals will complete an initial phone screen to assess inclusion/exclusion criteria that can be determined over the phone, and eligible participants will subsequently be scheduled for an in-person screening session. After giving informed consent, participants will complete a medical screening and psychiatric assessment, and biological samples (blood and urine) will be collected. Participants who remain eligible after this screening session will be randomly assigned to take one of two doses of brexpiprazole (2 milligram (mg) or 4 mg per day) or matched placebo for 14 days. Both investigators and participants will be blind to medication group assignments. After the in-person screening session, there are five study visits. 1) Day 1 of study medication: participants will complete a one-hour-long functional magnetic resonance imaging (fMRI) brain scan and take the first dose of study medication. 2) Day 7: participants will return to the lab for a brief check-in at which medication side effects will be assessed. 3) Day 13: blood and urine samples will be collected again; participants will take that day's dose of medication in the lab and then complete another one-hour-long fMRI brain scan. 4) Day 14: participants will take the last dose of medication in the lab and then complete a day-long procedure in which alcohol will be administered. 5) Day 15: participants will be debriefed and compensated $600 for study participation.
