A team of researchers at the National Institutes of Health (NIH) has reported encouraging results from the first human clinical trial of resiniferatoxin (RTX), a non-addictive, plant-based therapy aimed at alleviating intractable cancer pain.
RTX, a compound derived from the cactus-like Euphorbia resinifera plant, was administered via a single injection into the spinal fluid (lumbar intrathecal space) of patients with advanced-stage cancer. Participants in the trial, who had not found relief through standard treatments—including high-dose opioids—experienced a 38% reduction in their worst pain levels and a 57% decrease in opioid use.
“The effects are immediate,” said Dr. Andrew Mannes, lead study author and chief of the NIH Clinical Center’s Department of Perioperative Medicine. “This represents a new class of drugs with the potential to restore a sense of normal life to people facing extreme cancer pain.”
The trial enrolled patients with terminal, end-stage cancer—about 15% of cancer patients fall into this category, where conventional treatments no longer provide effective pain relief. A single dose of RTX delivered sustained pain relief, significantly reducing the need for sedative opioids and allowing patients to reconnect with their families and daily lives.
RTX works by targeting a specific sub-group of pain-transmitting nerve fibers.
It activates the TRPV1 ion channel, also known as the heat and pain receptor, in a way that causes an overload of calcium inside the nerve cells. This overload disables the nerve’s ability to transmit pain, essentially “cutting” the pain-specific communication line between the body and brain, without affecting other sensations like touch, pressure, or motor function.
“RTX selectively targets the TRPV1 neurons—arguably the most crucial for pain transmission,” said Dr. Michael Iadarola, senior study author and long-time NIH pain researcher. “Unlike broad methods like surgery or chemicals that affect all nerve types, RTX allows for precision pain relief while preserving other vital nerve functions.”
Originally identified as an irritant in Euphorbia resin more than 2,000 years ago, RTX was developed into a therapeutic agent through decades of basic NIH research into cellular pain pathways. Scientists visualized how RTX floods pain-sensing cells with calcium, which formed the basis for launching human trials.
Importantly, RTX does not produce a “high” or addiction risk like opioids. Its targeted mechanism offers hope for broader applications beyond cancer pain, including chronic nerve injuries (neuromas), post-surgical pain, trigeminal neuralgia (facial pain), and oral inflammation after head and neck radiation.
“This is a simple, targeted, and highly selective approach that paves the way for personalized pain medicine,” added Iadarola.
The next phase includes larger-scale clinical trials to seek FDA approval and expand RTX’s clinical use. This research was supported by the Intramural Research Program of the NIH Clinical Center and the NIH’s National Institute of Neurological Disorders and Stroke.
.jpg)
.jpg)
0 Comments