A phase 1b study to investigate the potential interactions between ASP8062 and buprenorphine/naloxone in patients with opioid use disorder

Background: There is an unmet need for therapeutics with greater efficacy and tolerability for the treatment of opioid use disorder (OUD). ASP8062 is a novel compound with positive allosteric modulator activity on the γ-aminobutyric acid type B receptor under development for use with standard-of-care treatment for patients with OUD. Aims: To investigate the safety, tolerability, interaction potential, and pharmacokinetics (PK) of ASP8062 in combination with buprenorphine/naloxone (B/N; Suboxone®). Methods: In this phase 1, randomized, double-masked, placebo-controlled study, patients with OUD began B/N (titrated to 16/4 mg/day) treatment upon enrollment (induction, Days 1–4; maintenance, Days 5–18; downward titration, Days 19–26; and discharge, Day 27). On Day 12, patients received a single dose of ASP8062 60 mg or placebo with B/N and underwent safety and PK assessments. Primary endpoints included frequency and severity of treatment-emergent adverse events (TEAEs), clinical laboratory tests, respiratory depression, and suicidal ideation. Secondary endpoints investigated the impact of ASP8062 on B/N PK. Results: Eighteen patients were randomized and completed the study (ASP8062, n = 12; placebo, n = 6). With this sample size typical for phase 1 drug–drug interaction studies, ASP8062 was well tolerated; most TEAEs were mild in severity, and none led to treatment withdrawal. ASP8062 did not enhance substance use-related TEAEs, respiratory depression, or suicidal ideation and did not have a clinically significant impact on the PK of B/N. Conclusions: In this phase 1 study, ASP8062 was safe, well tolerated, and did not enhance respiratory suppression induced by buprenorphine. Trial registration: Clinicaltrials.gov identifier: NCT04447287.