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Published on: September 2, 2020
Intrathecal resiniferatoxin in a dog model: efficacy in bone cancer pain
Dorothy C Brown1, Kimberly Agnello, Michael J Iadarola
1Department of Clinical Studies, University of Pennsylvania, School of Veterinary Medicine, Philadelphia, PA, USA Anesthesia Section, Department of Perioperative Medicine, Clinical Center, NIH, Bethesda, MD, USA.
Abstract:
Resiniferatoxin (RTX) is the most potent among all known endogenous and synthetic agonists for the transient receptor potential vanilloid 1 (TRPV1) receptor, which is a calcium-permeable nonselective cation channel, expressed on the peripheral and central terminals of small-diameter sensory neurons. Prolonged calcium influx induced by RTX causes cytotoxicity and death of only those sensory neurons that express the TRPV1 ion channel leading to selective targeting and permanent deletion of the TRPV1-expressing C-fiber neuronal cell bodies in the dorsal root ganglia. The goal of this project was to provide preclinical efficacy data, that intrathecal RTX could provide effective pain relief and improve function in dogs with bone cancer without significant long-term side effects. In a single-blind, controlled study, 72 companion dogs with bone cancer pain were randomized to standard of care analgesic therapy alone (control, n = 36) or 1.2 μg/kg intrathecal RTX in addition to standard of care analgesic therapy (treated, n = 36). Significantly more dogs in the control group (78%) required unblinding and adjustment in analgesic protocol or euthanasia within 6 weeks of randomization, than dogs that were treated with RTX (50%; P < 0.03); and overall, dogs in the control group required unblinding significantly sooner than dogs that had been treated with RTX (P < 0.02). The analgesic effect was documented in these dogs without any evidence of development of deafferentation pain syndrome that can be seen with neurolytic therapies.
Insights
Resiniferatoxin (RTX) offers a novel approach to pain management by selectively targeting TRPV1-expressing neurons. This study shows intrathecal RTX effectively relieved bone cancer pain in dogs with fewer side effects than standard care.
Area of Science:
- Neuroscience
- Pharmacology
- Veterinary Medicine
Background:
- Resiniferatoxin (RTX) is a potent agonist for the TRPV1 receptor, found on sensory neurons.
- TRPV1 activation leads to calcium influx, causing selective cell death in TRPV1-expressing neurons.
- This mechanism offers potential for targeted neurolysis and pain relief.
Purpose of the Study:
- To evaluate the preclinical efficacy of intrathecal RTX for managing bone cancer pain in dogs.
- To assess functional improvement and long-term side effects of RTX treatment.
- To determine if RTX prevents deafferentation pain syndrome.
Main Methods:
- A single-blind, controlled study involving 72 dogs with bone cancer pain.
- Dogs were randomized to standard analgesics (control) or standard analgesics plus intrathecal RTX (1.2 μg/kg).
- Pain management effectiveness and side effects were monitored over 6 weeks.
Main Results:
- Fewer dogs treated with RTX required analgesic adjustments or euthanasia compared to the control group (50% vs. 78%, P < 0.03).
- Control group dogs needed intervention significantly sooner than RTX-treated dogs (P < 0.02).
- RTX treatment demonstrated analgesic effects without inducing deafferentation pain.
Conclusions:
- Intrathecal RTX provides effective pain relief and functional improvement in dogs with bone cancer.
- RTX offers a potentially safer alternative to traditional neurolytic therapies with minimal long-term side effects.
- RTX selectively targets and eliminates pain-sensing neurons without causing deafferentation pain syndrome.
