A team of Lawrence Livermore National Laboratory (LLNL) researchers has discovered a promising new treatment to counteract the effects of fentanyl and related opioids.
The new treatment could, over time, be a boon to doctors and medical professionals dealing with the crisis of fentanyl, a drug whose lethal effects has killed more than 210,000 Americans during the past three years.
Discovered under a three-year grant from the Defense Threat Reduction Agency (DTRA), the treatment is described in a paper published today online in the American Chemical Society (ACS) journal, ACS Central Science.
"The development of a medical countermeasure candidate for the treatment of exposure to a variety of opioids is a really exciting advancement in the fight to counter the opioid epidemic," said Audrey Williams, the director of LLNL's Forensic Science Center.
"What is so unique about this work is the combination of the chemical synthesis, pharmacokinetics, computational modeling, chemical characterization, and both in vitro and in vivo testing capabilities at LLNL to surmount this major challenge."
Kris Kulp, the leader of the Lab's Biosciences and Biotechnology Division, noted that neutralizing the toxic effects of the public health threat of fentanyl is a pressing need for the nation.
"This cross-disciplinary team combined unique Lab capabilities to discover a potential medical countermeasure against fentanyl and related synthetic opioids that could significantly impact the lives of our friends and neighbors," Kulp said.
"The success of this project highlights the power and importance of our research and re-emphasizes why combining scientific expertise is necessary for solving the most challenging problems."
The fentanyl treatment discovered by LLNL scientists is subetadex, a compound first developed more than two decades ago in 2002 and one that had not apparently ever been tested against fentanyl until it was done by LLNL.
Currently, the main drug used to counter fentanyl overdoses is naloxone (or narcan), which works well but doesn't remain active in the body for long and needs to be re-administered, said LLNL biologist Mike Malfatti, a co-author of the ACS Central Science paper. Naloxone has a half-life (time until only half of the material is remaining) of between 30 to 80 minutes.
"Subetadex has a longer half-life (about 7.5 hours) than naloxone and acts to encapsulate the opioid, preventing it from binding to opioid receptors in the body," Malfatti said.
In their studies, the Lab team found that when in vivo models were exposed to sub-lethal fentanyl doses, the recovery times were significantly faster when subetadex was administered.
The observed recovery times were reduced from about 35 minutes to about 17 minutes for fentanyl, from about 172 minutes to about 59 minutes for carfentanil and from about 18 minutes to about 12 minutes for remifentanil.
"Collectively, the data presented herein validates subetadex as a solid platform from which further research work can be launched for the development of a medical countermeasure against the effects of fentanyl and its analogs," the researchers wrote.
One of the paper's co-authors, LLNL biologist Heather Enright, called the team's development and testing of subetadex from computational modeling and screening to in vivo efficacy remarkable.
"This effort is another great example of the outstanding science that has resulted from LLNL's multidisciplinary approach to tackling major challenges in the threat assessment and medical countermeasure space," Enright said.
When project principal investigator Carlos Valdez, a chemist in the Lab's Forensic Science Center, and his team started looking at compounds to counter fentanyl, they originally settled on a drug called sugammadex.
Like subetadex, sugammadex was developed in 2002 and it is a cyclodextrin, or a sugar molecule bound together in rings of various sizes.
The Lab researchers' interest in sugammadex was piqued because of the drug's ability to bind the anesthetic rocuronium for patients who after surgery were not clearing it in a timely fashion, leaving them with prolonged numbness in their bodies. Sugammadex was found to bind the rocuronium effectively and facilitate its excretion from the patient.
"We wanted to test if a similar compound could counter the effects of fentanyl by binding the opioid and speeding up its clearance from the affected individual," Valdez said. "Sugammadex was tested in our laboratory, but it was ineffective in binding fentanyl due to its large cavity that did not allow for the opioid to fit tightly in its interior.
"After other cyclodextrins were tested, we were excited to discover subetadex, a smaller version of sugammadex, was able to bind fentanyl extremely well, thus preventing it from reaching its biological target."
In their experiments testing the binding of different compounds, the team used a technique known as nuclear magnetic resonance (NMR).
"We found by NMR that the subetadex was binding to fentanyl quite well and that it was not letting go of it," Valdez said. "That was a big moment. When you find a compound that does something already, you get excited because you know as a chemist that you can come in and can modify that compound to make it even better."
Work by LLNL scientists to discover a medical countermeasure against fentanyl started in 2015 when researchers received an internally funded Laboratory Directed Research and Development (LDRD) grant. The LDRD funding enables the undertaking of high-risk, potentially high-payoff projects at the forefront of science and technology.
In their quest to discover a medical countermeasure for fentanyl, Valdez estimates that he and his team members tested at least 50 different compounds before hitting success with subetadex.
Initial in vitro toxicity assessments that include hemolytic activity and cholesterol binding propensity show that subetadex has a non-toxic profile, and is comparable to sugammadex, which is a Food and Drug Administration-approved drug.
A pharmacokinetic study, employing a carbon-radiolabeled version of subetadex and LLNL's unique bioaccelerator mass spectrometry capability, showed a rapid clearance of subetadex from major organs, such as the heart, liver, brain and kidney, during the studies.
For their future work, the team hopes to increase the half-life of subedatex, so that it could be used prophylactically or as a preventative measure for first responders or the military, Malfatti said. The team also may want to expand the range of the drug as a broad-spectrum treatment against more opioids.
In addition to Valdez, Malfatti and Enright, other team members are: Summer McCloy, Esther Ubick and Edward Kuhn (retired), all lab technicians; Alagu Subramanian, a summer student; Doris Lam and Nicholas Be, both biologists; Saphon Hok and Brian Mayer, both chemists; and Edmund Lau, a computational chemist. The paper is dedicated to Victoria Lao, a team member who died of cancer last year during the paper's preparation.
