A new, plant-based anti-cancer treatment is showing promising signs in horses with melanoma, German researchers have learned.
Betulinic acid, already used for treating human melanomas, could become an effective and safer alternative for treating equine melanoma compared to traditional chemotherapies, said Reinhard Paschke, PhD, Prof. Dr. habil., of Martin Luther University, in Halle, Germany.
Betulinic acid comes from the bark of white birch and similar trees. It attacks cancer cells by breaking down the membranes of the mitochondria—the cell’s “energy factory.” If a cancer cell’s mitochondria malfunctions, it lacks energy and, therefore, will die.
Paschke said he decided to test betulinic acid on equine melanomas when the owner of a gray horse contacted him after reading his research on melanoma treatment in dogs two years ago.
In their pilot study, he and colleagues tested the effects of betulinic acid, as well as two man-made derivatives, on the cells of two kinds of equine melanoma lines in a laboratory setting. The two derivatives are easier to work with because they dissolve better in water, Paschke said. All three of the products caused both kinds of cancer cells to die, mostly within 24-48 hours of treatment; the most effective treatment was actually one of the derivatives (NVX-207), which caused “high cytotoxicity” (high amount of cell death), he said.
The researchers then moved on to a tolerance study in live animals. The purpose of that experiment was not to test the drug’s efficacy, but to make sure horses can handle the treatment plan safely and without serious side effects. The team treated only two horses for this phase: two gray Warmblood mares aged 13 and 18. The scientists injected NVX-207 directly into the melanoma tumors on the mares weekly for 19 weeks.
Regular clinical observation and blood work showed that the mares tolerated the treatment very well. “Neither clinical nor clinicopathological adverse effects of the compound were noted,” the researchers reported. However, the weekly injections into the tumor do cause the horses discomfort, Paschke noted.
“Intratumoral application means stress for the horses, unfortunately,” he said. “The best application would be a cream or an ointment, but we have not developed that (yet).”
Still, the stress of the injections has to be weighed against the benefits of the treatment, he added. Melanoma can spread to other parts of the body and lead to pain, disability, and death.
Current treatments, mainly with the chemotherapy cisplatin, have limited success rates and carry health risks to the horse owner or treating veterinarian when manipulating such a strong anti-cancer drug, Paschke said. Human exposure to the drug can result in adverse effects such as nausea, bone marrow suppression, and kidney problems.
“Local chemotherapy with cisplatin or a local excision only shows successful results for small tumors,” said Paschke. “But due to the high amount of melanoma (in gray horses generally and in each individual gray horse) and the risks when administering cisplatin, a new treatment strategy has to be found.”
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