A Food and Drug Administration advisory committee voted 27-0 on Jan. 14 against recommending agency approval of oxycodegol, a new type of opioid molecule designed to slow passage of the drug through the blood-brain barrier and hence cause less of a “high” and potentially blunt the drug’s abuse potential.
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But the panel, which includes members from both the Anesthetic and Analgesic Drug Products Advisory Committee and the Drug Safety and Risk Management Advisory Committee, unanimously shared the opinion that the data submitted by the drug developer, Nektar, failed to clearly demonstrate the drug’s safety and efficacy.
“There was a lot of ambiguity [in the data] about safety and efficacy, and this is too important an issue to have so much ambiguity,” summed up Ronald S. Litman, DO, professor of anesthesiology and critical care at the University of Pennsylvania in Philadelphia and chair of the combined committee.
“The subliminal message” that would surround oxycodegol if it received FDA approval would be that it is a “safer” opioid, “and that would make it a blockbuster drug, and for that to happen you need data that [prove] the benefits outweigh risks, but we didn’t see those data. It was all speculation, and we can’t approve a potential blockbuster opioid in the middle of a public health opioid crisis based on speculation,” commented Steve B. Meisel, PharmD, system director of medication safety for Fairview Health Services in Minneapolis and a committee member.
According to Nektar, oxycodegol is a new molecular entity that combines a morphinan pharmacophore, oxycodol, with a six-unit chain of polyethylene glycol, a design that slows movement of the drug into the brain by about an hour after an oral dose when compared with oxycodone. It works as a full mu opioid receptor agonist that inhibits the nociceptive pathways while it reduces reinforcing or euphoric effects and other negative CNS-mediated side effects because of its slowed entry into the central nervous system.
But, as became apparent during the course of the day’s presentations and questions, while the clinical evidence in general supported this mechanism, the data were flawed by many limitations and caveats. FDA staffers critiqued the company’s data set for a variety of issues, including testing dosages that were “arbitrary and flawed,” evidence for “high oral abuse potential” in one study, including “a high rate of euphoria” of 17% even at the recommended dosage level (and a higher euphoria incidence at a higher dosage), limited information on additional pain medications that enrolled patients had used both before enrollment and during the study, and possible enrollment bias. Many panel members also raised concerns that included the efficacy data coming from a single randomized study, incomplete data on possible hepatic toxicity, no data to address potential abuse via injection or inhalation, a very modest demonstrated increment in pain relief, and abuse potential studies that relied on a single dose of the drug.
On the other hand, many committee members, and others in the pain field, applauded the general concept behind oxycodegol and urged the developer to run additional studies and collect more data for a future FDA application.
There has been “a lot of controversy” about oxycodegol, often centered on the question “why do we need another opioid,” commented Steven P. Cohen, MD, professor of anesthesiology, neurology, and pain medicine and chief of pain medicine at Johns Hopkins Health in Baltimore. “Having another opioid on the market with a different pain indication and possibly lower abuse potential” would be welcome and “almost certainly would not result in more prescriptions or abuse,” said Dr. Cohen, who was not a committee member but addressed in an interview the need for new and effective pain medications that offer an alternative to conventional opioids. “Patients who might otherwise be prescribed a different opioid might receive oxycodegol instead,” he suggested. But first, the developing company will need to collect a lot more clinical data than it has reported so far.