Treatment of γ-Hydroxybutyric Acid and γ-Butyrolactone Overdose with Two Potent Monocarboxylate Transporter 1 Inhibitors, AZD3965 and AR-C155858

The illicit use of γ-hydroxybutyric acid (GHB), and its prodrug, γ-butyrolactone (GBL), results in severe adverse effects including sedation, coma, respiratory depression, and death. Current treatment of GHB/GBL overdose is limited to supportive care. Recent reports indicate that GHB-related deaths are on the rise; a specific treatment may reduce lethality associated with GHB/GBL. Pretreatment with inhibitors of Monocarboxylate Transporter 1 (MCT1), a transporter that mediates many of the processes involved in the absorption, distribution (including brain uptake), and elimination of GHB/GBL, has been shown to prevent GHB-induced respiratory depression by increasing the renal clearance of GHB. To identify whether MCT1 inhibition is an effective treatment of GHB overdose, the impact of two MCT1 inhibitors, (S)-5-(4-hydroxy-4-methylisoxazolidine-2-carbonyl)-1-isopropyl-3-methyl-6-((3-methyl-5-(trifluoromethyl)-1H-pyrazol-4-yl)methyl)thieno[2,3-day]pyrimidine-2,4(1H,3H)-dione (AZD3965) and 6-[(3,5-dimethyl-1H-pyrazol-4-yl)methyl]-5-[[(4S)-4-hydroxy-2-isoxazolidinyl]carbonyl]-3-methyl-1-(2-methylpropyl)thieno[2,3-day]pyrimidine2,4(1H,3H)-dione (AR-C155858), on the toxicokinetics and toxicodynamics of GHB/GBL was assessed when the administration of the inhibitor was delayed 60 and 120 minutes (post-treatment) after administration of GHB/GBL. AR-C155858 and AZD3965 reduced the toxicodynamic effects of GHB when GHB was administered intravenously, orally, or orally as the prodrug GBL. The impact of these inhibitors on GHB toxicokinetics was dependent on the route of GHB administration and the delay between GHB/GBL administration and administration of the MCT1 Inhibitor. The reduction in GHB plasma exposure did not explain the observed effect of MCT1 inhibition on GHB-induced respiratory depression. The efficacy of MCT1 inhibition on GHB toxicodynamics is likely driven by the pronounced reduction in GHB brain concentrations. Overall, this study indicates that inhibition of MCT1 is an effective treatment of GHB/GBL overdose.