Treating melanoma in horses is challenging, particularly when lesions are present in critical areas. A clinical study evaluated the use of betulinic acid (BA, found in the bark of plane and birch trees) based on its many properties as an anti-parasitic and anti-inflammatory substance with anti-cancer activity [Weber, et al. Betulinic acid shows anticancer activity against equine melanoma cells and permeates isolated equine skin in vitro. BMC Veterinary Research 2020, vol. 16, no. 44; https://doi.org/10.1186/s12917-020-2262-5].
While melanomas are reported to comprise nearly 4% of neoplastic disease in horses, approximately 60% progress to malignancy and visceral metastases. In cases where surgical excision is difficult or might result in untenable tissue damage, other treatment options are invaluable, particularly for topical treatment.
The study demonstrated that use of 1% BA in “Basicreme DAC” reaches high concentrations in the skin layers when combined with 20% medium-chained triglycerides. To reach melanoma cells in a live horse, the topical compound must be able to penetrate the stratum corneum. This objective was achieved with in vitro equine skin samples. Within 24 hours of tissue exposure to the drug, antiproliferative and cytotoxic effects were observed.
The investigators stated, “The compound is able to not only affect the melanoma cell’s metabolism, but also to inhibit the proliferation of equine melanoma cells in vitro and therefore potentially stop tumor growth in vivo.”
There might be some unintended consequences since it was also found that normal equine dermal fibroblasts are sensitive to BA. It is thought that these would be minor inflammatory effects, yet further trials need to be conducted in living horses.
