The frog-derived bacterium Ewingella americana demonstrated strong anticancer activity by both directly targeting tumor cells and activating immune responses in mice.

A single intravenous dose of Ewingella americana, a bacterium isolated from frog gut microbiota, produced a 100% complete response in a mouse model of colorectal cancer, completely eliminating tumors and outperforming several immune checkpoint inhibitors and chemotherapies in the study.

Notably, Ewingella americana isolated from Japanese tree frogs eliminated tumors with a one-shot intravenous administration in the preclinical model.

Researchers envision expanding this approach across multiple cancer types, while pursuing safer and more effective delivery methods and exploring combination therapies with existing immunotherapies and chemotherapies.

Plans include testing in additional cancers such as breast, pancreatic, and melanoma, improving delivery strategies, and evaluating combinations with current treatments.

The study casts biodiversity as a valuable source for new cancer therapies and references a Gut Microbes publication from December 2025 by Seigo Iwata and Eijiro Miyako as foundational support.

The research highlights biodiversity as a promising reservoir for novel medical technologies, citing the 2025 Gut Microbes paper by Iwata and colleagues.

Tumor-targeting is driven by mechanisms including exploiting the hypoxic tumor microenvironment, leaky vasculature, and tumor-specific metabolism, enabling selective bacterial colonization of cancer tissue.

Ewingella americana preferentially accumulates in tumor tissue due to hypoxia, local immune suppression around tumors, abnormal vasculature, and distinct tumor metabolism, enabling targeted delivery.

Safety is favorable, with rapid clearance from the bloodstream (half-life about 1.2 hours), no detectable presence in major organs, only transient mild inflammation, and no long-term toxicity observed over two months.

Pharmacokinetics and safety show quick systemic clearance, lack of organ colonization, mild transient inflammatory response resolving within days, and no sustained toxicity over 60 days.

The bacterium combats tumors through dual actions: direct cytotoxic effects by accumulating in the tumor and immune activation that brings in T cells, B cells, and neutrophils, triggering cytokine release and cancer cell death.