Pyrvinium Pamoate: A Promising Treatment for Merkel Cell Carcinoma

In a groundbreaking study published in the Journal of Clinical Investigation on July 5, 2025, researchers at the University of Arizona Cancer Center have identified pyrvinium pamoate, a medication initially approved by the FDA in 1955 for treating pinworm infections, as a potential therapeutic agent against aggressive Merkel cell carcinoma (MCC). This rare and fast-growing neuroendocrine skin cancer has limited treatment options, leading to a pressing need for effective therapies.

According to Dr. Megha Padi, a senior author of the study and an assistant professor in the College of Science at the University of Arizona, "Merkel cell carcinoma is increasing in incidence. Even though it’s a rare cancer type, it mimics a lot of properties that other cancers have." This aggressive cancer type is associated with a mortality rate three to five times higher than that of melanoma, prompting urgent research into alternative treatment strategies.

The study's findings indicate that pyrvinium pamoate may inhibit the growth of cancer cells and reverse their neuroendocrine characteristics, which are hallmarks of MCC. The researchers conducted laboratory tests that demonstrated the drug's ability to reduce tumor growth in mouse models of MCC. "This is a hypothesis, but some people think the reason an antiparasitic agent could be effective against cancers is that tumors are a little bit like parasites in our body," Dr. Padi explained. "If the pathways they have hijacked to feed themselves are the same, then you get lucky, and you have a tumor type that could be amenable to killing by these antiparasitic drugs."

The exploration of pyrvinium pamoate as a cancer treatment stems from its known role as a Wnt pathway inhibitor. The Wnt signaling pathway is instrumental in the development of various cancers, including MCC. By targeting this pathway, researchers hope to develop a clinically viable treatment protocol for MCC.

Despite the promising results, Dr. Padi cautioned that further research is necessary to optimize treatment protocols and evaluate the long-term efficacy and safety of pyrvinium pamoate in humans. Current treatments for MCC include surgery, radiation, and immunotherapy, but their response rates remain limited, underscoring the need for new therapeutic avenues.

This study adds to a growing body of research examining repurposed medications for cancer treatment. A 2023 study published in the Cancer Research Journal highlighted similar findings, showing that certain antiparasitic drugs could exhibit antitumor properties in diverse cancer types, including breast and colorectal cancers.

As the incidence of Merkel cell carcinoma rises, the findings from the University of Arizona may provide hope to patients and clinicians alike. If further studies confirm these results, pyrvinium pamoate could represent a significant advancement in the fight against one of the most aggressive forms of skin cancer, offering a new line of defense for affected individuals.

In conclusion, the exploration of existing medications like pyrvinium pamoate not only demonstrates the innovative approaches being pursued in oncology but also emphasizes the importance of continued research into repurposing drugs for novel applications, potentially leading to improved outcomes for patients facing aggressive cancers.