As of October 2025, researchers at the University of California San Diego are working toward human clinical trials for a cancer immunotherapy that uses the cowpea mosaic virus (CPMV), a harmless plant virus. The treatment has demonstrated potent anti-tumor effects in preclinical studies using mice and in clinical studies on pet dogs with cancer.
How the CPMV treatment works
The CPMV immunotherapy is an in situ vaccine, meaning it is injected directly into a tumor to stimulate the immune system to fight cancer.
Immune system awakening: The virus is harmless to human cells but is recognized as a foreign invader by the immune system. This triggers a strong anti-viral immune response.
Broad immune cell recruitment: This reaction recruits an army of immune cells, including neutrophils, macrophages, natural killer cells, B cells, and T cells, to destroy the tumor.
Systemic immune memory: As the immune system fights the treated tumor, it also learns to recognize cancer cells elsewhere in the body. This creates a lasting memory that continues to hunt down and eliminate metastatic cancer cells, preventing recurrence.
Unique immune activation: Unlike other plant viruses, CPMV uniquely triggers multiple interferons (type I, II, and III) and activates a key immune pathway through a receptor called Toll-like receptor 7 (TLR7).
Latest developments and clinical trial status
Research has advanced on several key fronts, moving the therapy closer to human trials.
Promising preclinical safety data: A 2025 study in Toxicology Reports showed that after receiving CPMV injections, test animals showed the desired immune effects without significant negative health consequences.
Efficacy against metastatic cancer: In May 2024, researchers showed that systemically administering the CPMV nanoparticles to mice prevented metastasis from several types of cancer, including colon, ovarian, melanoma, and breast cancer.
Improved manufacturing: A 2025 study in PubMed describes a new, scalable process for purifying CPMV that is compatible with Good Manufacturing Practice (GMP), a necessary step for producing the therapy for human trials.
Path toward human trials: The research team, led by Professor Nicole Steinmetz at UC San Diego, has stated they are "poised to move this work beyond the bench and toward clinical trials".
Low-cost production: The virus can be grown in plants using only soil, sunlight, and water, making it a potentially revolutionary and affordable cancer therapy compared to traditional, expensive treatments. 