An experimental opioid drug designed to alleviate acute pain without the risk of abuse or addiction has “enormous” potential to treat some types of chronic pain, according to pain management experts.
“There’s a great opportunity for drugs like that. We really need to find something that doesn’t have rewarding properties that doesn’t lead to addiction,” said Lynn Webster, MD, past president of the American Academy of Pain Medicine, who was the lead investigator in initial studies of the drug.
The injectable analgesic – which for now has clunky name CR845 – was developed by Cara Therapeutics (NASDAQ: CARA), a Connecticut biopharmaceutical company. The company recently released the results of human abuse liability studies of CR845 on recreational drug users — who gave it very low scores for drug “liking” and making them feel “high.”
“The results are especially encouraging because CR845 was administered by rapid intravenous injection, which provides the fastest delivery of the highest level of drug into the bloodstream, a critical determinant of abuse liability,” said Derek Chalmers, PhD, President and CEO of Cara Therapeutics.
Unlike other narcotics, CR845 doesn’t act on opioid receptors in the brain and central nervous system – which can cause side effects such as respiratory depression, nausea, vomiting, and the euphoria that can lead to abuse and addiction. Instead, CR845 acts on receptors in nerve endings – in what is known as the peripheral nervous system.
“It doesn’t enter the brain very well, if at all. It has minimal brain entry. So it works peripherally as an analgesic. And as a result it didn’t demonstrate any rewarding properties. That means it wasn’t liked, it doesn’t have any liking effect, and it does not have any significant abuse potential,” Webster told National Pain Report.
Cara Therapeutics hopes to begin Phase III clinical studies on CR845 in early 2015. If those efficacy studies are successful and it gets FDA approval – which could take years – the drug is most likely to be used as an injectable analgesic to treat acute pain caused by injuries or surgery.
But someday it could also become available in pill form to treat chronic pain.
“I think it can be. I don’t see any reason why eventually it couldn’t become an oral medication,” says Webster. “Initially this is going to be hospital based, for emergency rooms or acute care. But if it is effective as an analgesic, because of the low abuse potential this would be an enormous opportunity to (use) a safer, more effective analgesic that would avoid some of the rewarding properties of the current opioids. I would hope they would develop it.”
But because CR845 primarily works on the peripheral nervous system, Webster and other experts say it most likely won’t be effective treating spinal pain or other types of chronic pain that originate in the central nervous system.
“You may see it being useful for something like arthritis, where there is constant pressure and inflammation of joints that create the pain. But it’s not likely to be effective for other types of central nervous system pain, like fibromyalgia. It’s probably not going to work for that,” said Bob Twillman, PhD, Deputy Executive Director of Policy and Advocacy for the American Academy of Pain Management.
“I think there’s a huge need for it. I think the potential is fantastic. What this is most likely to replace is a lot of the short acting medications that we use for acute pain. It may have some applications for chronic pain, but for the most part this is going to be an acute pain medication. “
But even if CR845 is only approved for acute pain, Twillman says it could be a major step forward in reducing the risk of opioid addiction.
“All of the people who first get exposed to opioids in the context of some sort of injury or having their wisdom teeth pulled, surgery or whatever; those folks get this medication instead and never have that first exposure to an opioid that could eventually lead them to a substance abuse problem.”