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Personalized Neoantigen Vaccine Induces Rapid and Robust
Immunological Responses in Thai Melanoma and Renal Cell
Carcinoma Patients
Piriya Wongkongkathep, Pimpayao Sodsai, Nussara Pakvisal, Worawan Bunrasmee, Nittaya Boonnak,
Tawanchay Sangcharoen, Poorichaya Somparn, Nattiya Hirankarn*, Virote Sriuranpong, Trairak Pisit
Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital, Thai Red Cross
Society
*Corresponding Author E-mail: nattiya.h@chula.ac.th
Abstract
Background: Cancer immunotherapy with a personalized neoantigen peptide vaccine is a novel treatment
modality showing global promise but is not yet clinically available in Thailand. This
approach harnesses the specificity of the immune system to target tumor-specific epitopes
presented by the patient’s HLA molecules.
Methods: We conducted a Phase I clinical trial to assess safety, feasibility, and early immunological
responses in patients with advanced melanoma (n=9) and renal cell carcinoma (n=3).
Individualized neoepitopes (~10-20 peptides per patient) were identified using whole-exome
sequencing, RNA-seq, immunopeptidomics, and in-house bioinformatics. GMP-manufactured
synthetic long peptides were formulated with poly-ICLC and delivered intramuscularly
over a 12-week schedule. Peripheral blood mononuclear cells (PBMCs) were collected
longitudinally to assess T cell responses using IFN-γ ELISPOT and flow cytometry.
Results: The vaccine was safe and well tolerated, with only mild (grade 1–2) adverse events. All 12
patients mounted de novo T cell responses against at least one neoantigen. On average,
46% of tested peptides induced measurable IFN-γ responses, with activation detectable
as early as two weeks post-priming. Flow cytometry confirmed both CD4+ and CD8+ T
cell activation, with a shift toward effector and terminal memory phenotypes. Responses
were significantly stronger to mutant peptides compared to wild-type counterparts, and one
patient exhibited epitope spreading to non-vaccine peptides.
Conclusions: This first-in-Thailand study demonstrates that intramuscular administration of personalized
neoantigen peptide vaccines is safe and capable of inducing rapid, mutation-specific T cell
responses without checkpoint inhibitors. These findings support further clinical development
and application of this approach for cancer immunotherapy.
Harmony in health: Innovation for Sustainable Medicine
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