In a significant advancement for cancer immunotherapy, researchers have developed a novel approach using mRNA-encoded nanobodies that effectively combat colorectal cancer in preclinical models. An original study published in eGastroenterology demonstrates how lipid nanoparticle-delivered mRNA producing anti-PD-L1 nanobodies can suppress tumor growth in both sporadic and colitis-associated colorectal cancer, offering new hope for patients with cancers resistant to conventional immunotherapies.
The Challenge of Current Colorectal Cancer Immunotherapies
Colorectal cancer remains the third most common cancer in the United States and the second leading cause of cancer-related deaths. While immunotherapies targeting immune checkpoint molecules like PD-1 and PD-L1 have revolutionized cancer treatment, their effectiveness against colorectal cancer has been limited. Most patients with colorectal cancer have microsatellite stable tumors that respond poorly to these treatments, creating an urgent need for more effective therapeutic strategies.
Conventional monoclonal antibodies used in immunotherapy face several limitations: their large molecular size restricts tumor penetration, they can trigger immune-related adverse effects, and they're costly to produce. Additionally, anti-PD-L1 antibodies have shown disappointing results in treating colitis-associated colorectal cancer, a particularly aggressive form of the disease linked to chronic intestinal inflammation.
Nanobodies: A Superior Alternative
This study turned to nanobodies – unique single-domain antibodies originally discovered in camelids and sharks. These miniature antibodies offer significant advantages over conventional antibodies: their small size (approximately 15 kDa versus 150 kDa for conventional antibodies) allows for better tumor penetration, they have lower immunogenicity, and they demonstrate high stability and binding affinity .
However, nanobodies have their own limitation: their small size leads to rapid clearance by the kidneys, shortening their therapeutic window. To address this, the researchers developed a novel quadruple nanobody format, connecting four individual anti-PD-L1 nanobodies with flexible linkers to create a larger molecule that remains in circulation longer while maintaining excellent tissue penetration.
Innovative Delivery Using mRNA-LNP Technology
Leveraging technology made famous by COVID-19 vaccines, the team used lipid nanoparticles to deliver nucleoside-modified mRNA encoding these anti-PD-L1 nanobodies. This approach bypasses several limitations of conventional nanobody production, which typically requires complex expression systems in bacteria, yeast, or mammalian cells with risks of toxin contamination and misfolding.
The mRNA-LNP platform enables the body to continuously produce therapeutic nanobodies, maintaining effective levels throughout treatment. The researchers engineered both monomeric and quadruple forms of anti-PD-L1 nanobody mRNA and tested their efficacy in multiple mouse models of colorectal cancer.
Superior Performance of Quadruple Nanobodies
The results revealed striking differences between the two formats. While monomeric nanobody mRNA showed some effect against tumor growth, the quadruple nanobody mRNA demonstrated significantly superior efficacy. The larger quadruple nanobody remained in circulation approximately twice as long as the monomeric version, providing sustained therapeutic activity.
In mice with sporadic colorectal cancer tumors, quadruple nanobody mRNA-LNP treatment significantly inhibited tumor progression, with effects becoming apparent after the third injection. Serum analysis confirmed that the quadruple format achieved higher blood levels and slower clearance, explaining its enhanced therapeutic performance.
Effective Against Aggressive Colitis-Associated Cancer
Perhaps most impressively, the quadruple nanobody mRNA-LNP treatment successfully reduced tumor incidence in colitis-associated colorectal cancer – a context where conventional PD-L1 antibodies have failed. The treatment significantly diminished tumor numbers in both wild-type mice and genetically susceptible models that typically develop more aggressive disease.
The researchers uncovered the mechanism behind this success: the treatment fundamentally reshaped the tumor immune microenvironment. It markedly reduced infiltration of myeloid-derived suppressor cells and tumor-associated macrophages – two key cell types that create an immunosuppressive environment allowing tumors to evade immune detection. Simultaneously, it increased infiltration of CD8+ T cells, the immune system's primary cancer-fighting cells.
Direct Impact on Immune Cell Development
The study went further to demonstrate that the nanobody mRNA approach directly affects immune cell development. When researchers treated bone marrow hematopoietic stem cells with nanobody mRNA-LNPs in vitro, the treatment significantly inhibited their differentiation into macrophages and reduced expression of immunosuppressive markers including PD-L1, CD80, CD86, and CD206. This finding suggests the therapy may work not only by activating existing immune cells but also by preventing the development of new immunosuppressive cells that support tumor growth.
Clinical Implications
The research team proposes that human versions of these quadruple anti-PD-L1 nanobody mRNA-LNPs could represent a promising new immunotherapy approach for colorectal cancer patients. The technology combines the advantages of nanobodies – superior tissue penetration and low immunogenicity – with the proven safety and efficacy of the mRNA-LNP delivery platform. While the current study focused on single-agent therapy, the researchers note that combination approaches using multiple nanobodies targeting different immune checkpoints in a single mRNA construct, or combining nanobody mRNA with chemotherapy or radiotherapy, might yield even better results.
In conclusion, this study represents a significant step forward in cancer immunotherapy, demonstrating how advanced molecular engineering combined with cutting-edge delivery technology can overcome limitations of current treatments. As research progresses toward human trials, this approach may soon offer new hope for colorectal cancer patients, particularly those with forms of the disease that currently have limited treatment options.
See the article:
Chu W-M, Ma L, Hew B, et al . Immunotherapy against colorectal cancer via delivery of anti-PD-L1 nanobody mRNA. eGastroenterology 2025; 3 :e100106. doi:10.1136/egastro-2024-100106
About eGastroenterology
eGastroenterology , a BMJ journal partnered with Gut and launched by leading scientists in gastroenterology and hepatology, has been indexed in the Web of Science Core Collection (ESCI), PubMed, DOAJ, Scopus, CAS, ROAD , and many other major international databases within just two years of its launch. The journal is expecting to receive its first Impact Factor in June 2026.
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Immunotherapy against colorectal cancer via delivery of anti-PD-L1 nanobody mRNA