Indivior announced positive results from its pivotal Phase 3 clinical trial of their investigational opioid use disorder (OUD) treatment, RBP-6000 (buprenorphine depot) injection.

RBP-6000, a sustained-release formulation of buprenorphine, uses the Atrigel delivery system that consists of a polymeric solution of a biodegradable poly-(DL-lactide-co-glycolide) co-polymer dissolved in the solvent N-methyl pyrrolidone (NMP). After injection, the depot releases buprenorphine over a 1-month period as the polymer biodegrades.

In the trial, 504 treatment-seeking adults aged 19–64 years were randomized to RBP-6000 (n=404) or placebo (n=100). Suboxone (buprenorphine and naloxone) sublingual film was administered during induction to suppress opioid withdrawal symptoms and to verify there were no allergies to buprenorphine. Study patients were randomized to either 6 once-monthly 300mg doses (300/300mg), 2 once-monthly 300mg doses followed by 4 once-monthly 100mg doses (300/100mg), or 6 once-monthly subcutaneous injections of placebo. The primary endpoint was the average percentage of opioid-free weeks (abstinence), measured by urine sample negativity for opioids and also self-reports of no illicitopioid use from Week 5 to 24.  

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Results showed that at Month 6, the RBP-6000 groups demonstrated abstinence rates of 41.3% (300/300mg dose) and 42.7% (300/100mg dose) vs. 5% for placebo (P<0.0001), a statistically significant difference.

There were no unexpected safety findings in the study and the profile was similar to that of transmucosal buprenorphine. Severe treatment-emergent adverse events were seen in both RBP-6000 dose groups (6.9% each) and placebo (4%). The most commonly reported adverse events were headache, constipation, nausea, injection site pruritus, vomiting, insomnia, and upper respiratory tract infection. 

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