NIH Scientists Pioneer Promising Treatment for Intractable Cancer Pain
Photo: RAEANN DAVIES/SHUTTERSTOCK
NIH scientists report that a first-in-human clinical trial of a new therapy based on the plant-derived molecule resiniferatoxin (RTX) shows it is a safe and effective agent for pain control in patients with intractable cancer pain. Researchers tested a single injection of small quantities of RTX into the lumbar cerebral spinal fluid of advanced-stage cancer patients and found it significantly reduced their reported worst pain intensity and opioid usage.
The trial enrolled participants with terminal end-stage cancer who were among the 15% of cancer patients unable to find pain relief from standard-of-care pain interventions, including a vast quantity of opiates.
One injection of RTX provided durable relief; patients’ need for opioids declined sharply and their quality of life improved. They no longer needed to spend significant periods sedated with opioids and, after treatment, were able to re-engage with family, friends and communities.
The researchers believe RTX also has potential to treat many other pain conditions.
RTX is not addictive and doesn’t cause a high. It prevents pain signals from reaching the brain by inactivating a sub-group of nerve fibers which transmit heat and pain signals from damaged tissue. RTX activates the TRPV1 ion channel, which allows an overload of calcium to flood into the nerve fiber and block its ability to transmit pain signals.
Unlike other approaches that use heat, cold, chemicals or surgery to non-selectively interrupt nerves to stop pain, RTX targets the specific sensory pathways of tissue damage, pain and heat. Other sensory pathways remain intact.
RTX is derived from the Euphorbia resinifera plant. Euphorbia extract has been known for 2,000 years to contain an “irritant” substance, which NIH scientists identified how to use for patients through basic research on living cells observed through a microscope. Adding RTX to TRPV1-containing cells under a microscope caused a visible calcium overload.
The next steps include additional, larger clinical trials to move RTX toward eventual approval by the FDA and clinical availability.