In the realm of pain management, opioids have long reigned supreme due to their potent analgesic properties. Morphine, oxycodone, and their synthetic derivatives have become staples in clinical settings for the relief of acute and chronic pain. Nonetheless, their therapeutic utility is heavily shadowed by severe side effects including respiratory depression, dependence, and tolerance, which have precipitated a global public health concern. The opioid epidemic in the United States exemplifies these challenges, with overdose deaths exceeding 80,000 in 2023 alone. In response to this crisis, scientists worldwide have been actively pursuing novel analgesics that provide effective pain relief without the dangerous liabilities of opioids.
A groundbreaking advancement emerges from a team of researchers at Kyoto University, who have uncovered a new class of oral analgesics that circumvent opioid pathways entirely. Their compound, provisionally named ADRIANA, operates via a mechanism distinct from traditional opioid action—targeting the α2B-adrenoceptor subtype—thereby offering pain relief while mitigating risks related to respiratory and cardiovascular function. The discovery represents a paradigm shift in analgesic pharmacology, poised to redefine clinical pain management and potentially alleviate the burden of opioid dependence.
The team’s exploration was inspired by the biological role of noradrenaline, a neurotransmitter pivotal in the body’s response to stress and pain. Within the sympathetic nervous system, noradrenaline binds to adrenoceptors, of which the α2 subtypes (α2A, α2B, and α2C) play nuanced roles in modulating nociception and vascular tone. Previous pharmacological efforts focused on agonizing α2A-adrenoceptors to achieve analgesia; however, this approach carries a significant risk of destabilizing cardiovascular regulation, prompting the search for alternative receptor targets.
Through meticulous observation, the researchers noted that selectively blocking the α2B-adrenoceptor could indirectly elevate endogenous noradrenaline concentration. This elevation would, in turn, facilitate activation of α2A-adrenoceptors prudently confined within the central nervous system to suppress pain signals without triggering the adverse cardiovascular responses typical of non-selective α2 agonists. The insight laid the groundwork for identifying a molecule that could serve as a selective α2B-adrenoceptor antagonist, an approach previously unexplored in analgesic drug development.
To screen for such selective compounds, the scientists harnessed cutting-edge biochemical technology known as the TGFα shedding assay, a robust method to assess G protein-coupled receptor activity with high specificity. This innovative assay allowed the team to quantitatively measure the functional inhibition of individual α2-adrenoceptor subtypes, empowering them to pinpoint the first ever selective α2B-adrenoceptor antagonist—a milestone achievement in receptor pharmacology.
Preclinical evaluations commenced with administering the candidate compound to rodent models, demonstrating potent analgesic efficacy without observable cardiovascular or respiratory compromise. These promising animal studies paved the way for clinical trials, which were initiated at Kyoto University Hospital under stringent regulatory oversight. The Phase I trial involved healthy volunteers and primarily assessed safety and pharmacokinetics, affirming a favorable tolerance profile. Subsequently, a Phase II trial focused on postoperative patients recovering from lung cancer surgeries, yielding compelling evidence of effective pain mitigation and enhanced recovery trajectories.
Encouraged by these results, the collaborative effort expanded transnationally. Kyoto University partnered with BTB Therapeutics, an innovative venture company stemming from the university itself, to spearhead the next stage: a large-scale Phase II clinical trial conducted in the United States. This trial aims to further elucidate ADRIANA’s therapeutic potential, dosing protocols, and safety across diverse patient populations suffering from various forms of acute and chronic pain.
If brought successfully to market, ADRIANA promises to revolutionize pain management by offering an alternative to opioids that retains comparable analgesic strength with significantly reduced side effects. This development could substantially reduce the dependency on opioids, curbing the incidence of addiction, overdose, and the escalation of the opioid epidemic that has ravaged communities internationally. Moreover, ADRIANA’s novel mode of action may stimulate a broader investigation into GPCR subtype selectivity as a framework for developing safer, more precise medications.
The implications extend beyond therapeutic benefits. As a non-opioid analgesic originating from Japan, ADRIANA also highlights the increasingly vital role of global academic-industry partnerships in tackling pressing health crises. This international collaboration sets a precedent for integrating advanced molecular pharmacology with large-scale clinical evaluation, thereby accelerating the translation of fundamental discoveries into real-world treatments that can improve patient outcomes worldwide.
Masatoshi Hagiwara, a specially-appointed professor at Kyoto University, underscores this vision, emphasizing the drug’s potential not only in acute but also in chronic pain management scenarios. The goal is to broaden access so that a larger segment of the population suffering from debilitating pain can benefit from this new class of analgesics, ultimately improving the quality of life for millions.
The research journey exemplifies the synergy of innovative receptor biology, advanced assay technology, and rigorous clinical science. The team’s publication in the Proceedings of the National Academy of Sciences marks a pivotal contribution to pharmacology, spotlighting the α2B-adrenoceptor as a promising therapeutic target. It illustrates how deepened understanding of receptor subtypes can yield transformative medical interventions.
As ADRIANA moves closer to regulatory approval and clinical adoption, the scientific community and patients alike eagerly anticipate a new era in pain treatment—one less shadowed by the risks of addiction and life-threatening side effects. This breakthrough heralds hope for millions battling pain worldwide and signals a significant step toward curbing the devastating toll of opioid misuse.
Subject of Research: People
Article Title: Discovery and development of an oral analgesic targeting the α2B adrenoceptor
News Publication Date: 4-Aug-2025
Image Credits: KyotoU / Hagiwara lab
Keywords: Analgesics, Opioids, Medical treatments, Drug studies, Clinical trials
