A recent paper in the American Journal of Veterinary Research by Eward et al (2025) has highlighted the a possible novel niclosamide stearate prodrug which shows potential efficacy against naturally occurring canine osteosarcoma in a clinical feasibility study.
This paper investigates the use of a new formulation of niclosamide – an anti-parasitic drug – converted into a stearate prodrug for improved delivery and efficacy against canine osteosarcoma. This formulation of prodrug combats previously known bioavailability issues which limited niclosamide’s chemotherapy use, by enabling both injectable or implantable nanoparticle delivery. The study highlights that in naturally occurring canine osteosarcoma, treatment with NSPT resulted in promising clinical responses, including some dogs achieving extended survival and remission compared to traditional therapies. The results also demonstrated that the new prodrug could inhibit metastasis, especially in the lungs and offered a well tolerated, innovative treatment with potential for translation to human medicine.
Mediolateral radiograph of the right tarsus illustrating osteosarcoma (OSA) of the distal tibia taken from https://www.fitzpatrickreferrals.co.uk/orthopaedics/canine-osteosarcoma/
However, some limitations of the study include a small sample size which limits the generalisability and statistical power of the findings. More extensive clinical trials with larger cohorts are needed to confirm the efficacy and overall safety. Whilst a positive is that this study focuses on naturally occurring canine osteosarcoma rather than models of the disease. The long-term outcomes and potential side effects of the prodrug are not extensively reported, which still leads to questions of durability of response and chronic safety. There is also a lack of mention with regards to combination therapies for canine osteosarcoma and the role of niclosamide stearate alongside these modalities.
Eward, W. C., Pavic, K., Spasojevic, I., Somarelli, J. A., Brighton, H., Cullen, M., Jung, S., Visgauss, J. D., Brigman, B. E., Needham, D., & Suter, S. E. (2025). Novel niclosamide stearate prodrug therapeutic shows potential efficacy against naturally occurring canine osteosarcoma in a clinical feasibility study. American Journal of Veterinary Research (published online ahead of print 2025). Retrieved Nov 25, 2025, from https://doi.org/10.2460/ajvr.24.06.0176**
https://avmajournals.avma.org/view/journals/ajvr/aop/ajvr.24.06.0176/ajvr.24.06.0176.xml open access research paper
