Core Framework & Diagram What Is Personalized Immunotherapy?
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—— Personalized Immunotherapy: using your own immune system characteristics to tailor a treatment plan.
I. Individualized neoantigen cancer vaccines: turning your tumor mutations into weapons
Every tumor is unique. Cancer cells accumulate tens to thousands of genetic mutations during division, producing abnormal protein fragments — 'neoantigens' — that normal cells don't have. Theoretically, neoantigens are perfect immunotherapy targets: they're tumor-exclusive, normal cells don't express them, so immune attacks targeting neoantigens won't harm normal tissue; they're 'self-made' by tumor cells, and once the immune system forms memory of them, it can continuously monitor for recurrence. But neoantigens are highly individualized — your tumor mutation profile and another patient's are almost certainly not identical. This means neoantigen-targeting vaccines must be individually designed and manufactured for each patient.
In 2023, data that excited the entire tumor immunology world appeared. Moderna and Merck's jointly developed mRNA individualized cancer vaccine (mRNA-4157/V940), in a Phase II clinical trial for melanoma adjuvant treatment (KEYNOTE-942), combined with PD-1 inhibitor pembrolizumab, reduced the recurrence or death risk of high-risk melanoma by approximately forty-four percent compared to pembrolizumab alone. This vaccine's manufacturing process is a complete demonstration of individualized immunotherapy: simultaneously whole-exome sequence patient tumor tissue and normal tissue, identifying tumor-specific somatic mutations; AI algorithms screen the twenty to thirty-four neoantigen sequences most likely to be presented by the patient's own HLA molecules and most likely to activate T cell responses; encode these neoantigen sequences into one mRNA, factory synthesize individualized mRNA vaccine; patient receives vaccine, dendritic cells take up mRNA, translate neoantigen proteins, present to T cells, establishing specific immune memory targeting this batch of tumor mutations. The entire process, from tumor biopsy to vaccine preparation, currently takes about six to eight weeks. With advancing sequencing speed and mRNA synthesis technology, this time is continuously being compressed.
2. TIL therapy and TCR-T: finding the warriors who know the tumor best
Tumor-Infiltrating Lymphocytes (TIL) are T cells that have already entered the tumor interior. The reason they're there is because they've already recognized tumor antigens — they're the immune system cells that 'know this tumor best.' TIL therapy logic is very direct: from surgically resected tumor tissue, isolate these TILs, massively expand them in vitro (usually hundreds to thousands of times), then reinfuse to the patient. In 2023, Steven Rosenberg's team at NCI (NIH) — the founding team of TIL therapy — published a key study in Nature: in standard treatment-failed metastatic cervical cancer patients, TIL therapy achieved a forty-four percent objective response rate, with three patients achieving complete remission — unprecedented results in this extremely poor prognosis population. In the same year, Iovance Biotherapeutics' TIL therapy product Lifileucel (for metastatic melanoma) gained FDA approval — the first approved non-genetically engineered TIL therapy, a milestone for TIL therapy transitioning from 'research tool' to 'commercial product.'
TCR-T cell therapy goes further: first identify from patient tumors the T cell clones targeting specific tumor neoantigens with highest activity, extract their TCR gene sequences, then through genetic engineering introduce this TCR into ordinary T cells — mass-manufacturing T cell troops 'equipped with the most precise antennas.' Several collaborative studies have shown initial clinical efficacy in solid tumors, an important node for TCR-T therapy moving toward broader tumor type applications.
3. Biomarker stratification: finding 'who should use which plan'
Not all patients are suitable for the same immunotherapy options. The most important current immunotherapy response prediction biomarkers: PD-L1 expression — PD-L1 expression level on tumor cell surfaces was the earliest predictive biomarker for PD-1/PD-L1 inhibitors. PD-L1 high expression (usually TPS ≥50% as the high expression threshold) patients have higher response rates to PD-1 inhibitors (like pembrolizumab). But PD-L1's limitations are also clear: some PD-L1 low expression patients still respond, some high expression don't respond — it's a necessary but not sufficient predictive indicator. Tumor Mutational Burden (TMB) — the density of somatic mutations in the tumor genome. More mutations, more neoantigens produced, more targets the immune system 'can recognize,' theoretically better response to immune checkpoint inhibitors. In 2020, FDA approved pembrolizumab for TMB-high (≥10 mut/Mb) solid tumors — the first pan-cancer type immunotherapy approval based on TMB.
Microsatellite Instability High / Deficient Mismatch Repair (MSI-H / dMMR) — tumors with high microsatellite instability or deficient mismatch repair, due to defective DNA repair mechanisms, accumulate large amounts of mutations and neoantigens, with extremely high response rates to PD-1 inhibitors. In 2017, FDA approved pembrolizumab for MSI-H/dMMR solid tumors — the first tumor treatment in history approved based on biomarker (rather than cancer type). This was the true beginning of 'individualized' rather than 'organ location-classified' tumor treatment. Tumor Microenvironment (TME) typing — more refined stratification characterizes the overall immune profile of the TME. From 'hot tumors' (immune cell-rich and functional) to 'cold tumors' (immune cell-scarce or excluded), different 'temperature' tumors respond completely differently to different immunotherapy strategies.
4. Gut microbiome: the hidden variable in personalized immunotherapy
In 2018, almost simultaneously, Science published three independent studies from three different cancer types (melanoma, lung cancer, kidney cancer), proving the same thing: gut microbiome composition is significantly correlated with PD-1 inhibitor treatment response. Specifically: patients with high abundance of specific beneficial bacteria like Faecalibacterium prausnitzii and Akkermansia muciniphila in their gut have higher PD-1 inhibitor response rates and longer progression-free survival; while patients with low microbiome diversity and few short-chain fatty acid-producing beneficial bacteria tend to be 'non-responders.'
Mechanistically, gut microbiome influences systemic immunity through multiple pathways: short-chain fatty acids (SCFA) produced by beneficial bacteria fermenting dietary fiber regulate T cell differentiation direction, enhancing effector T cell infiltration into tumors; specific bacteria (like Akkermansia) activate gut dendritic cells, upregulating whole-body anti-tumor CD8+ T cell responses; patients with high microbiome diversity have more precise immune regulation, lower inflammation background, slower T cell exhaustion rates. In 2022, Robert Vonderheide's team at the University of Pennsylvania published in Nature: melanoma patients who didn't respond to PD-1 inhibitors, after receiving fecal microbiota transplantation (FMT) from 'complete responder' donors, approximately thirty percent showed clinical responses — the first direct proof that changing the microbiome can convert 'non-responders' into 'responders.'
5. The future: from cancer to all immune-related diseases
Although current personalized immunotherapy mainly focuses on cancer, its logic equally applies to all immune-related diseases: autoimmune diseases — different autoimmune disease subtypes have different underlying immune dysregulation mechanisms. Biomarker-based individualized biologic selection (which cytokine pathway should be most targeted) has begun being practiced in rheumatoid arthritis and ankylosing spondylitis. Infectious diseases — predicting patient responses to specific vaccines or anti-infection approaches based on HLA type and TCR library may enable 'individualized vaccination strategies' in the future. Immune aging management — precise measurement of individual immune age and specific deterioration dimensions can guide 'which intervention (exercise, NK cell infusion, Senolytics) is most effective for this older adult' individualized immune aging management plans.
Personalized immunotherapy's ultimate vision is transforming 'immune system uniqueness' from medicine's obstacle ('why didn't this person respond to the same drug?') into medicine's advantage ('precisely because everyone's immune system is different, we can customize the most suitable plan for each person').
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