Thailand Medical Study on Intramuscular Neoantigen Vaccine Provides Interesting Insights
Nikhil Prasad Fact checked by:Thailand Medical News Team Feb 25, 2026 1 hour, 33 minutes ago
Thailand Medical: Researchers in Thailand have reported encouraging early results from a Phase Ib clinical trial evaluating a personalized cancer vaccine delivered through intramuscular injection in patients with advanced melanoma and renal cell carcinoma. The study focused primarily on safety and immune response, offering new insights into how vaccine delivery methods may influence cancer immunotherapy outcomes.
Personalized intramuscular cancer vaccine shows strong immune activation in early Thai clinical trial.
The research was conducted by
Thailand Medical researchers from Chulalongkorn University and The King Chulalongkorn Memorial Hospital; Khon Kaen University, Prince of Songkla University; the Medical Genetics Center, Thailand and the Wattanosoth Cancer Hospital.
Personalized Vaccines Designed from Tumor Mutations
Each patient’s vaccine was uniquely designed using genetic sequencing of their tumor tissue. Scientists identified cancer-specific mutations known as neoantigens and produced approximately 20 synthetic long peptides tailored to each individual. These peptides were combined with an immune-stimulating agent called poly-ICLC and administered into muscle tissue.
Twelve patients with advanced or metastatic disease participated in the study. Most had already undergone previous treatments, including immune checkpoint inhibitors. The trial’s primary objective was to assess safety, while secondary objectives included measuring immune activation and observing clinical outcomes.
Strong And Rapid Immune Responses
All participants developed measurable neoantigen-specific T-cell responses. On average, 46 percent of the personalized peptides triggered immune activity. Notably, immune responses were detectable within one week of the first vaccine dose and generally peaked after completion of the initial priming schedule.
Importantly, the vaccine stimulated both CD4-positive helper T cells and CD8-positive cytotoxic T cells. Previous peptide vaccine studies using intradermal or subcutaneous routes often generated predominantly CD4 responses. The intramuscular approach in this trial appeared to support a more balanced activation of both immune cell types.
Two patients with the longest survival demonstrated higher levels of terminally differentiated effector memory CD8-positive T cells, suggesting a possible link between immune cell phenotype and clinical outcome. In one case, immune responses persisted for more than four years following vaccination.
Evidence Of Tumor Immune Remodeling
Optional tumor re-biopsies performed in three patients revealed increased infiltration of CD8-positive T cells within tumor tissue after vaccination in two cases. One patient also demonstrated evidence of epitope spreading, where immune responses expanded beyond the original vaccine targets, indicating broader immune engagement.
Safety Profile and Key Findings
The va
ccine was well tolerated. Reported side effects were limited to mild or moderate injection site pain and short-lived fever. No severe immune-related toxicities were observed.
Further analysis identified features associated with stronger immune responses. Peptides predicted to bind both major immune presentation pathways showed higher immunogenicity. Mutations involving small insertions or deletions were more likely to generate immune responses than single-point mutations. Certain amino acid changes, such as proline substitutions, were linked to reduced immunogenicity.
This Medical News report underscores that patients previously treated with immune checkpoint inhibitors were still able to mount significant vaccine-induced immune responses.
Conclusion
Although the study was small and not designed to demonstrate definitive clinical efficacy, it clearly showed that intramuscular administration of personalized neoantigen synthetic long peptide vaccines is safe and capable of inducing rapid, mutation-specific immune responses in heavily pretreated patients. The findings suggest that delivery route plays a meaningful role in shaping immune activation. Larger studies, particularly those combining this vaccine strategy with immune checkpoint inhibitors earlier in treatment, are warranted to determine whether these strong immunologic effects can translate into sustained clinical benefit.
The study findings were published on a preprint server and are currently being peer reviewed.
https://www.medrxiv.org/content/10.64898/2025.12.02.25341434v1
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