The National Institute of Health (NIH) scientists have reported a promising development in the treatment of intractable cancer pain through a first-in-human clinical trial. The therapy involves the use of resiniferatoxin (RTX), a molecule derived from a cactus-like plant, which has shown to be safe and effective for pain control in patients with severe cancer pain.
Lead study author Dr. Andrew Mannes, chief of the NIH Clinical Center Department of Perioperative Medicine, stated, “The effects are immediate. This is a potential new therapy from a new family of drugs that gives people with severe cancer pain an opportunity to return some normality to their lives.”
The trial included participants with terminal end-stage cancer who did not find relief from standard care interventions. A single injection of RTX into the lumbar cerebral spinal fluid led to a 38% reduction in reported worst pain intensity and decreased opioid usage by 57%. Patients experienced improved quality of life and were able to reengage with family and friends.
Senior study author Michael Iadarola, PhD, noted the broader potential applications of RTX: “Targeting specific nerves brings many pain disorders into range of RTX and allows physicians to tailor the treatment to the patient’s pain problem. This interventional approach is a simple path to personalized pain medicine.”
RTX works by preventing pain signals from reaching the brain through its action on TRPV1 ion channels, effectively blocking heat and pain signals while leaving other sensations intact. “Basically, RTX cuts the pain-specific wires connecting the body to the spinal cord,” said Iadarola.
Dr. Mannes emphasized its selectivity: “What makes this unique from all the other things that are out there is this is so highly selective. The only thing it seems to take out is heat sensation and pain.”
Derived from Euphorbia resinifera, RTX’s active substance was identified by NIH scientists through basic research involving living cells observed under a microscope.
Further clinical trials are planned as part of efforts toward FDA approval and wider clinical availability. This research received support from NIH's Intramural Research Program and National Institute of Neurological Disorders and Stroke.
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