Future Pain Pills

By Roger Chriss, PNN Columnist

The Food and Drug Administration announced this week that it would require drug makers to conduct new studies on the effectiveness of opioid pain medication and whether long-term use of the drugs lead to addiction. The FDA’s unprecedented action was due in no small part to a 60 Minutes report that said the agency “opened the floodgates” to the opioid crisis by approving the use of opioids for chronic pain. 

With opioid medication coming under scrutiny again – and perhaps more regulatory action – this is a good time to assess where we stand with development of newer and safer painkillers.  

Many analgesics already on the market have too many risks or too few benefits. A recent meta-analysis in JAMA concluded that opioids “may provide benefit for chronic noncancer pain, but the magnitude is likely to be small.”

And a new Cochrane review on acetaminophen (Tylenol) for hip or knee osteoarthritis found “only minimal improvements in pain and function.”

So new analgesics, whether safer opioids or non-opioid drugs, are urgently needed. Fortunately, there has been significant progress.

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NKTR-181, from Nektar Therapeutics, is a new kind of opioid under “fast track” FDA review. It was designed with safety in mind, because it enters the nervous system slowly as a result of its unique chemical structure. NKTR-181 is the only abuse-deterrent opioid in the drug development pipeline designed to reduce the “high” and “drug liking” that can lead to addiction. Practical Pain Management recently gave it four out of five stars as a future analgesic.

Desmetramadol, from Syntrix Pharmaceuticals, is another opioid in early testing. Developed with support from the National Institute on Drug Abuse, desmetramadol is designed as a safer version of tramadol, a Schedule IV opioid. Researchers are looking at the results of a recent clinical trial to see whether the new drug “provides the safety and pain relief of tramadol without its metabolic issues.”

VX-150, from Vertex Pharmaceuticals, is a sodium channel inhibitor that late last year finished a “proof-of-concept” Phase II trial successfully. It acts specifically on sodium channels to block the pain caused by small fiber neuropathy. Because these channels are not expressed in the brain, VX-150 should have few if any cognitive side effects. Phase III clinical trials are expected to start later this year.

Tanezumab, from Pfizer and Eli Lilly, just completed a Phase III clinical study for chronic low back pain. The results showed that tanezumab injections were associated with a statistically significant improvement in low back pain compared with placebo. Tanezumab is also being studied as a treatment for osteoarthritis, although there are some lingering concerns about its side-effects.

Finally, the novel compound AT-121 from Astraea Therapeutics is showing promise as a non-addictive opioid analgesic. Researchers created AT-121 to bind to both the mu opioid receptor and the FQ peptide receptor, a combination that blocks the unwanted side effects of current opioid analgesics. Preclinical testing of AT-121 in animals found that it was more potent than morphine, but did not produce physical dependence or tolerance at high doses. The National Institute on Drug Abuse recently called AT-121 a “promising alternative to opioid pain medications.”

Improved understanding of the nervous system and of chronic painful disorders is also contributing to drug development. A recent review in Frontiers in Pharmacology looks at emerging “safer opioids” that provide effective pain relief with fewer side effects. The review explains that the new goal of drug developers is to target opioid receptors in injured or diseased tissues, while avoiding the brain to reduce cognitive side effects and minimize risk of abuse, addiction and overdose.

And new genetic research is identifying genes involved in painful neuropathies. For instance, a recent case report found that a variant in the gene PMP22 is linked to painful peripheral neuropathy in Charcot-Marie-Tooth Disease.

With the prevalence of chronic pain increasing as the population ages, the development of safer, more effective analgesics is critical. Advances in drug development techniques and better understanding of painful disorders should accelerate the process.  

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Roger Chriss lives with Ehlers Danlos syndrome and is a proud member of the Ehlers-Danlos Society. Roger is a technical consultant in Washington state, where he specializes in mathematics and research.

The information in this column should not be considered as professional medical advice, diagnosis or treatment. It is for informational purposes only and represents the author’s opinions alone. It does not inherently express or reflect the views, opinions and/or positions of Pain News Network.