Investigational drug aims to treat equine skin cancer

Photo: New Africa/Adobe Stock

A product development plan for an Investigational New Animal Drug for treating external squamous cell carcinoma (SCC) in horses has been submitted to the FDA by Medicus Pharma based in Philadelphia, Pennsylvania. The product is a dissolvable transdermal doxorubicin-containing microneedle array (D-MNA).¹

SCC is frequently diagnosed in horses, and is the most common equine malignant skin neoplasm. The rate of incidence is estimated to be between 7% and 37% of all skin tumors in horses.² The disease primarily affects adult or aged horses with white or partially white coats. Appaloosa, Belgian, American Paint, and Pinto breeds are particularly susceptible.¹

“In veterinary medicine, where there are only a handful of approved oncology drugs, we believe developing a noninvasive treatment for equine SCC represents an untapped and unmet market opportunity potentially in the range of $250 million,” Raza Bokhari, MD, MBA, executive chairman and CEO, said in a news release.¹ “The submission to the FDA of a novel product development program may provide us a first mover advantage and sets the stage to consider other companion animal species and types of cancer.”

Although SCC can develop anywhere on a horse, the disease typically is seen in nonpigmented or lightly pigmented areas of the head, neck, eyes and external genitalia.^2,3 The disease may appear as open, scaly or crusted skin, and can progress to large tumors and nonhealing wounds.³

“With presumed squamous cell carcinoma, many times the clinical sign of what I'm seeing is diagnostic enough…If you're not quite sure, then I think taking a biopsy sample is very much indicated. So, you can take a little punch biopsy or a snip biopsy and submit that to the pathologist for evaluation to confirm that,” Rachel Allbaugh, DVM, MS, DACVO, said in a 2024 dvm360 interview.

Current treatment for SCC often includes surgical removal of the affected tissue as well as cryotherapy of smaller masses, local injection of a chemotherapy drug, and photodynamic therapy. A topical chemotherapeutic drug in the form of drops, for tumors near the eye, or cream can be prescribed in some cases. In other cases, horses may be administered piroxicam, an oral drug that can slow the return of the cancerous cells.^1,2,4

The investigational D-MNA is a patent protected patch with cellulose based microneedle arrays tip-loaded with doxorubicin, according to Medicus. After the patch is applied, the microneedles penetrate the skin, create a temporary microchannel, and penetrate the tumor. Doxorubicin is then released into the target tumor, eradicating the cancer cells.¹

Medicus’ product development plan was created to support the Minor Use in Major Species (MUMS) designation for the drug that was received in December 2024. A MUMS designation, which must meet requirements to be maintained, entitles Medicus to an extended 7-year period of exclusive marketing following approval or conditional approval of the product, according to Medicus.¹ 

The development plan includes a randomized, double-blind, placebo-controlled clinical study to determine the efficacy of 2 D-MNA dose levels. Investigators plan to conduct the study at multiple locations with up to 50 horses presenting with SCC enrolled.¹

References

1. Medicus Pharma Ltd. Announces submission of product development plan to the Food and Drug Administration (FDA) to treat external squamous cell carcinoma (SCC) in horses. News release. Medicus Pharma. June 9, 2025. Accessed June 10, 2025. https://medicuspharma.com/medicus-pharma-ltd-announces-submission-of-product-development-plan-to-the-food-and-drug-administration-fda-to-treat-external-squamous-cell-carcinoma-scc-in-horses/
2. Sykora S, Brandt S. Papillomavirus infection and squamous cell carcinoma in horses. Vet J. 2017;223:48-54. doi:10.1016/j.tvjl.2017.05.007
3. Young A. Squamous cell carcinoma. University of California-Davis Center for Equine Health Horse Report. November 26, 2025. Accessed June 10, 2025. https://cehhorsereport.vetmed.ucdavis.edu/news/squamous-cell-carcinoma
4. McCafferty C. Advancements in squamous cell carcinoma treatment and management. dvm360. September 20, 2024. Accessed June 10, 2025. https://www.dvm360.com/view/advancements-in-squamous-cell-carcinoma-treatment-and-management