NIH researchers identify a novel opioid candidate, DFNZ, that delivers potent pain relief without respiratory depression, tolerance, or strong addiction signals in preclinical studies.
Written By: Mahathi Palivela, PharmD
Reviewed By: Pharmacally Editorial Team
Researchers at the National Institutes of Health (NIH) have reported the discovery of a novel opioid compound that may offer potent pain relief while avoiding key risks associated with traditional opioids, according to a study published in Nature.
Re-examining Nitazenes for Safer Therapeutic Potential
The research team investigated nitazenes, a class of synthetic opioids first developed in the 1950s but later abandoned due to extreme potency. These compounds selectively target mu-opioid receptors, which play a central role in pain modulation.
The scientists aimed to redesign this class to retain analgesic effects while reducing safety risks. Their work led to the identification of a modified compound, DFNZ, derived from an initial formulation called FNZ.
Distinct Pharmacology with Sustained Pain Relief
In preclinical studies using animal models, FNZ demonstrated rapid brain entry lasting only five to ten minutes. However, its metabolite DFNZ produced prolonged analgesia lasting at least two hours.
DFNZ showed high efficacy at the mu-opioid receptor but displayed a distinct pharmacological profile. Unlike conventional opioids, it produced sustained pain relief without causing respiratory depression, a major cause of opioid-related fatalities.
Reduced Signals of Dependence and Withdrawal
Repeated dosing of DFNZ did not lead to tolerance, dependence, or significant withdrawal symptoms. Among 14 standard withdrawal indicators, only mild irritability was observed in treated animals.
In behavioral studies assessing addictive potential, animals initially self-administered DFNZ. However, drug-seeking behavior stopped quickly once the drug was replaced with saline. This contrasts with drugs such as heroin, morphine, and fentanyl, where drug-seeking typically persists even after removal.
Neurochemical Profile May Explain Lower Addiction Risk
Further analysis showed that DFNZ increases dopamine levels in the brain’s reward circuitry, but in a slow and sustained manner. It does not trigger rapid dopamine spikes that are associated with strong drug-cue learning, craving, and relapse.
This mechanism may explain its reduced reinforcing effects compared with conventional opioids.
Expert Perspective
Nora D. Volkow, director of the NIH’s National Institute on Drug Abuse, emphasized that while opioids remain essential for pain management, their risks of addiction and overdose remain significant. She noted that developing effective analgesics without these drawbacks could provide major public health benefits.
Senior author Michael Michaelides, Ph.D., highlighted that DFNZ demonstrates an unusual pharmacological profile, combining high analgesic efficacy with safety features typically associated with lower-efficacy opioids.
Implications and Next Steps
The findings challenge the longstanding assumption that highly potent mu-opioid receptor agonists cannot be developed into safe therapeutics. The researchers suggest DFNZ could have potential applications not only in pain management, including surgical and cancer-related pain, but also in the treatment of opioid use disorder.
The team plans to conduct further preclinical studies to support regulatory submissions for human clinical trials.
References
NIH researchers discover pain-relieving drug with minimal addictive properties, April 1, 2026, National Institutes of Health (NIH) https://www.nih.gov/news-events/news-releases/nih-researchers-discover-pain-relieving-drug-minimal-addictive-properties.
Gomez, J.L., Ventriglia, E.N., Frangos, Z.J. et al. A µ-opioid receptor superagonist analgesic with minimal adverse effects. Nature (2026). https://doi.org/10.1038/s41586-026-10299-9
About the Writer
Mahathi Palivela is pursuing PharmD and has a strong interest in Clinical Pharmacy and Patient safety. She is passionate about handling and analyzing patient data, and translating clinical insights into clear, meaningful summaries. She aims to apply this interest in Medical Writing and Pharmacovigilance, focusing on improving patient outcomes through careful data interpretation and communication.