A pattern I keep encountering across my addiction psychiatry panel is the patient who did everything right: engaged in buprenorphine maintenance, attended groups, had negative urine screens for eight months, and then herniated a disc. Within six weeks, the pain became the relapse. Not a craving in the traditional sense. A legitimate medical need that the system had no clean answer for, and so the patient self-medicated. This population, chronic pain complicating OUD recovery, shows up in my clinic far more often than most trial protocols seem to anticipate. A 2017 study in the Journal of Substance Abuse Treatment found that 64.4% of patients in OUD treatment carried comorbid chronic pain, and that 61.8% of them had the pain before their first OUD diagnosis. The pain came first. We’ve been treating the sequela and ignoring the substrate.

That’s why I’m watching what Tris Pharma presents at the CPDD 88th Annual Scientific Meeting this week with real attention.

A Different Kind of Opioid Signal

Cebranopadol (TRN-228) acts simultaneously on two receptor systems: the mu-opioid peptide (MOP) receptor, the classic analgesic and addiction-implicated target, and the nociceptin/orphanin FQ peptide (NOP) receptor, a system that functions as a tonal brake on the mesolimbic dopamine circuit. The NOP component is what makes this pharmacologically interesting beyond the pain indication. Preclinical work has long suggested that NOP agonism reduces drug-seeking behavior, blunts stress-induced reinstatement, and modulates the reward salience that drives relapse. The MOP component handles nociception. The argument is that you get analgesia without lighting up the dopamine architecture the way a pure mu agonist does.

Tris reports that cebranopadol has completed Phase 3 for acute pain, with chronic pain Phase 3 studies planned. That’s further along than most clinicians realize. The acute pain data, alongside the human abuse potential studies that have characterized its reduced abuse liability relative to conventional opioids, positions this as more than a reformulation. The mechanism is genuinely novel in clinical development. What CPDD is adding this week is the SUD lens: what does this compound do, behaviorally and neurochemically, in populations already living with opioid dependence?

The mechanistic logic connects to something I’ve observed in my ketamine practice as well. Having treated over 3,000 patients for depression and anxiety with ketamine therapy, the cases that stick with me are patients in early OUD recovery who also carry treatment-resistant depression and pain sensitization. These three conditions share overlapping neurobiological terrain: glutamatergic dysregulation, altered reward processing, and central sensitization. A compound that modulates NOP signaling may be touching that same terrain from a different angle. That’s speculative at this stage, but it’s the kind of mechanistic overlap that should be generating cross-indication hypotheses in trial design right now.

What the Trial Architecture Is Missing

The structural problem in this space is that pain trials and SUD trials are designed and run by entirely separate sponsor teams, with different primary endpoints, different exclusion criteria, and different assumptions about what the patient looks like. A Phase 3 chronic pain trial will often exclude patients with active OUD. A buprenorphine maintenance trial will often exclude patients with uncontrolled pain. The patient in my waiting room, the one who relapsed because her back gave out, qualifies for neither. A PLOS Medicine analysis of 49,727 Medicare patients with comorbid OUD and chronic pain found meaningfully different outcomes depending on which MAT they received, which tells us this population is large enough for powered subgroup analyses, and complicated enough that we should be demanding they be enrolled rather than screened out.

For cebranopadol to fulfill its clinical promise, the field needs trials that deliberately recruit the pain-OUD comorbid patient and use endpoints that capture both dimensions simultaneously. Functional pain interference scores alongside standardized craving and relapse measures. That design requires addiction psychiatry input at the protocol-drafting stage, not as a post-hoc safety review. The FDA’s July 2025 safety labeling updates for long-term opioid prescribing signal that the agency is increasingly attentive to the addiction liability dimension of analgesic development. Sponsors designing cebranopadol’s chronic pain program now have both the regulatory pressure and the mechanistic rationale to build the comorbid population in from the start.

I’ll be reading the CPDD abstracts closely for any signal on abuse potential in active OUD patients and for whether any human data addresses the craving or relapse endpoints. That’s the readout that changes how I think about this class in clinical practice.

References

  1. GlobeNewswire — “Tris Pharma to Present on Dual NOP/MOP Receptor Agonist in Pain Management and Substance Use Disorder at CPDD 88th Annual Scientific Meeting, 2026”
  2. Tris Pharma — Cebranopadol (TRN-228) Pipeline: Phase 3 Acute Pain and Chronic Pain Development
  3. ATTC Network / Journal of Substance Abuse Treatment — “Chronic Pain Prevalent Among Patients with Opioid Use Disorder” (2017)
  4. PLOS Medicine — Methadone vs. Buprenorphine in OUD Patients with Comorbid Chronic Pain (Medicare cohort, n=49,727)
  5. First Word Pharma — Cebranopadol Human Abuse Potential and Acute Pain Efficacy Profile
  6. FDA Drug Safety Communication — “FDA Requiring Opioid Pain Medicine Manufacturers to Update Prescribing Information Regarding Long-Term Use” (July 31, 2025)
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Dr. Leonardo Vando, MD is Principal Investigator of Psychiatry at Vando Medical Services.