CYP2B6 polymorphisms and suicidal behaviour in people living with HIV treated with efavirenz-containing combination antiretroviral therapy: a global case–control study

Background: We analysed the association between host genetic risk scores (GRSs) predicting efavirenz (EFV) plasma levels and exposure and suicidal behaviours in participants in one of several global antiretroviral therapy (ART) clinical trials linked to the International Network for Strategic Initiatives in Global HIV Trials (INSIGHT). Methods: We conducted a matched case-control study (two controls per case) on suicide or grade-4 suicidal ideation/attempts or depression. Cases and controls were matched by EFV initiation strategy, study, and follow-up time. CYP2B6-based GRS classified participants as extensive, intermediate, or slow metabolisers. EFV and its metabolites (8-hydroxy-EFV and 7-hydroxy-EFV) were measured in plasma. Conditional logistic regression was used to analyse the associations between GRS categories, EFV levels, and suicidal behaviour. Results: Among 74 cases and 146 controls, 128 (58.2%) started EFV-containing first-line treatment. Of the treatment-experienced participants, 35% were on EFV at entry. Pre-existing psychiatric conditions and recreational drug-use were more common in cases (16.2%, 25.7%) than in controls (0.7%, 9.6%). On comparing cases to controls, more cases were extensive metabolisers (52% vs. 45%), but there were fewer slow metabolisers (8% vs. 13%). The unadjusted odds ratio (OR) for suicidal behaviour per one more minor allele was 0.76 (95% CI: 0.49-1.18). The OR for being a case vs. a control was 0.57 (95% CI: 0.38-0.86) per doubling of the EFV plasma level. Conclusion: CYP2B6-based GRS for cytochrome P450 enzymatic activity appeared not to be associated with suicidal behaviour in individuals living with HIV treated with EFV-containing ART combinations. CYP2B6-based GRS effectively predicted EFV exposure, but suicidal behaviour appeared more likely in extensive (normal) metabolisers.