Buprenorphine Analogs to Treat Relapse

Abstract

Substance use disorders (SUDs) – the overuse and dependence on at least one substance – have a lifetime prevalence of ~10% in the U.S. While buprenorphine (BUP) treatment reduces relapse rates, it is only marginally effective, as 70% of SUD patients relapse within a year. Due to BUP’s marginal effectiveness and abuse potential, there is a need to improve SUD therapies that prevent relapse to multiple drugs of abuse after exposure to stress, drug‐associated context and drug priming. Here we evaluate BUP and two analogs for their ability to inhibit cocaine‐ and stress‐induced relapse using a conditioned place preference (CPP) paradigm. Pharmacologically, BUP is a potent (sub nM) partial agonist at the m‐opioid receptor (MOR) with potent antagonist activity at the k‐(KOR), and d‐opioid receptors (DOR). In vitro BUP can act as a weak (mM) partial agonist at the nociceptin/OrphaninFQ (NOP) receptor with uncertain in vivo consequences. We measured in vitro potency and efficacy using [35S]GTPgS functional assays in CHO cells separately expressing DOR, KOR, MOR or NOP. Since NOP receptor agonists reduce relapse in animal models, we compared BU10119 with NOP agonist activity (EC50 = 120 nM ± 20; EMAX = 44% ± 5%) or BU12004 with NOP antagonist activity (KB = 190 nM ±30) to BUP (EC50 = 1300 nM ± 320; EMAX = 39% ± 7%). Furthermore, BU12004 and BU10119 were MOR antagonists (KB = 0.42 nM ± 0.08 and KB = 1.1 nM ± 0.2, respectively) with less abuse liability than the MOR partial agonist BUP (EC50 = 0.79 nM ± 0.31; EMAX = 34% ± 6%). BUP, BU10119, and BU12004 were all potent antagonists at DOR and KOR. BU10119 (1.0 mg/kg) attenuated cocaine‐primed reinstatement in CPP, but 10 mg/kg BU12004 did not. BUP trended toward reduced drug‐primed reinstatement. The in vivo rank order of BU10119 >BUP >BU12004 matches the rank order for NOP agonism in vitro. Additionally, 1.0 mg/kg of either BU10119 or BU12004 blocked swim stress‐primed reinstatement, ostensibly due to their KOR antagonist activity. Taken together, BU10119 provides a promising lead to treat SUDs with better effectiveness and reduced abuse potential compared to BUP.Support or Funding InformationSupported by NIDA R01 DA07315 and 035316.