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    How cancer vaccines work, from shared antigens to personalised mRNA

    Cancer treatment vaccines aim to treat existing cancer by strengthening the immune response against it, unlike preventive vaccines.[1] The newest are personalised mRNA vaccines encoding up to 34 neoantigens from a patient's own tumour; one met its phase 3 endpoints in melanoma in August 2026.[2][3]

    Editor reviewedStrict sourcingUpdated Cancer immunotherapyHealth and medicineLife sciences

    Most vaccines prevent disease. Cancer treatment vaccines instead try to treat a cancer that already exists by strengthening the immune response against it.[1] Personalised mRNA versions produced a phase 3 success in 2026.[3]

    Three kinds of treatment vaccine

    Some vaccines are made from a patient’s own tumour cells. Others use marks shared by many tumours. A third kind uses immune “messenger” cells called dendritic cells.[4] One dendritic-cell vaccine, sipuleucel-T, is approved for advanced prostate cancer.[4]

    NCI distinguishes autologous tumour-cell vaccines, shared-antigen vaccines and dendritic-cell vaccines; the approved example of the last is sipuleucel-T in advanced prostate cancer.[4] Oncolytic viruses are a related approach: T-VEC, based on herpes simplex virus type 1, was the first FDA-approved oncolytic virus therapy, and in August 2026 the FDA gave accelerated approval to another, vusolimogene oderparepvec, with nivolumab in PD-1-refractory melanoma.[5][6]

    How a personalised mRNA vaccine is made

    Every tumour has its own set of mutations. Some create new marks, called neoantigens, that look foreign to the immune system. For a personalised vaccine, scientists read the tumour’s mutations, choose the most promising marks and write instructions for them into mRNA. The vaccine then teaches the body’s T cells to look for those marks.[2]

    Individualised neoantigen therapies are designed per patient from tumour sequencing; intismeran autogene encodes up to 34 neoantigens in a synthetic mRNA.[2] Immunogenicity is the first test: in a phase 1 solid-tumour trial, autogene cevumeran induced neoantigen-specific T-cell responses in 71% of patients, and in pancreatic cancer vaccine-induced CD8+ clones had an estimated average lifespan of 7.7 years.[7][8]

    What the trials show

    In melanoma, a personalised vaccine plus the checkpoint drug Keytruda lowered the chance of the cancer returning in a mid-sized trial, and then met its goals in a larger phase 3 trial of 1,137 patients in 2026.[9][3] In pancreatic cancer, patients whose immune systems responded to the vaccine stayed cancer-free longer.[10] But a colorectal cancer trial of a vaccine given alone was stopped in August 2026.[11] In a small 2026 breast cancer study without a comparison group, 11 of 14 vaccinated patients stayed cancer-free for up to six years.[12]

    KEYNOTE-942 (n=157) gave an RFS hazard ratio of 0.561 for mRNA-4157 plus pembrolizumab, with 18-month RFS of 79% versus 62%.[9] Its phase 3 successor, INTerpath-001 (n=1,137), met RFS and DMFS endpoints, but effect sizes had not been published as of the August 2026 announcement.[3][13] The pancreatic data compare vaccine responders with non-responders (median RFS not reached vs 13.4 months), which is not a randomised comparison.[10] BioNTech’s colorectal monotherapy trial ended on an overall-survival imbalance, while its pancreatic combination trial continues.[11] In adjuvant triple-negative breast cancer (n=14, single arm), an individualised mRNA vaccine induced mostly de novo T-cell responses that stayed functional for years, with 11 patients relapse-free for up to six years.[12] Shared-neoantigen designs are an alternative to per-patient manufacturing: the vaccine Nous-209, encoding 209 frameshift peptides common to mismatch-repair-deficient tumours, induced responses in all 37 evaluable Lynch syndrome carriers in a phase 1b/2 trial.[14]

    What comes next

    Merck and Moderna plan to present INTerpath-001 at a medical meeting and discuss filings with regulators.[13] Details of the programmes are on personalized-neoantigen-vaccines.

    Questions readers ask

    How is a cancer treatment vaccine different from a preventive vaccine?

    Treatment vaccines target cancer that already exists by strengthening the body's defences against it, while prevention vaccines guard against cancer-causing agents.[1]

    What is in a personalised mRNA cancer vaccine?

    Intismeran autogene, for example, is a synthetic mRNA coding for up to 34 neoantigens tailored to an individual patient's tumour.[2]

    Do personalised cancer vaccines work?

    Evidence is mixed. A phase 3 melanoma trial combining one with Keytruda met its endpoints in August 2026, but BioNTech ended a colorectal trial of its vaccine used alone that same month after an overall-survival imbalance.[3][11]

    Are any cancer treatment vaccines already approved?

    Yes. The dendritic-cell vaccine sipuleucel-T is approved for advanced prostate cancer.[4]

    Sources

    Each numbered claim is a statement we checked against the sources listed with it. Status shows how well established it is.

    1. [1]

      Cancer treatment vaccines treat existing cancer by strengthening the body's defences against it, unlike preventive vaccines that guard against cancer-causing agents. confirmedas of 2026-10-10

    2. [2]

      Intismeran autogene (mRNA-4157/V940), co-developed by Merck and Moderna, is an individualised mRNA therapy encoding up to 34 neoantigens chosen from each patient's tumour. confirmedas of 2026-08-19

    3. [3]

      Merck and Moderna announced on 19 August 2026 that the 1,137-patient phase 3 INTerpath-001 trial of intismeran autogene plus Keytruda in resected stage IIB-IV melanoma met its primary endpoint of recurrence-free survival and key secondary endpoint of distant metastasis-free survival versus Keytruda alone. confirmedas of 2026-08-19

    4. [4]

      Treatment vaccines can be custom-made from a patient's own tumour cells, built on antigens shared by many tumours, or made from dendritic cells; the dendritic-cell vaccine sipuleucel-T is approved for advanced prostate cancer. confirmedas of 2026-10-10

      • Cancer Treatment Vaccines · National Cancer Institute · 2019-09-24 · Types of cancer treatment vaccines (retrieved 2026-10-10)
    5. [5]

      Talimogene laherparepvec (T-VEC), based on herpes simplex virus type 1 and used in melanoma, was the first FDA-approved oncolytic virus therapy. confirmedas of 2026-10-10

    6. [6]

      On 6 August 2026 the FDA granted accelerated approval to Replimune's oncolytic virus vusolimogene oderparepvec (Tudriqev) with nivolumab for advanced melanoma that progressed on PD-1 therapy; 24.2% of 91 evaluable patients responded, and confirmatory trials are required. confirmedas of 2026-08-06

    7. [7]

      In a phase 1 trial across advanced solid tumours, autogene cevumeran induced neoantigen-specific T-cell responses in 71% of patients. confirmedas of 2025-01-01

    8. [8]

      A 2025 follow-up estimated that vaccine-induced CD8+ T-cell clones in pancreatic cancer responders had an average lifespan of 7.7 years. confirmedas of 2025-03-01

    9. [9]

      In the randomised phase 2b KEYNOTE-942 trial of 157 patients with resected melanoma, mRNA-4157 plus pembrolizumab lengthened recurrence-free survival versus pembrolizumab alone (hazard ratio 0.561), with 18-month recurrence-free survival of 79% versus 62%. confirmedas of 2024-02-01

    10. [10]

      In a 16-patient pancreatic cancer study, the individualised mRNA vaccine autogene cevumeran induced new neoantigen-specific T cells in 8 patients, and these responders had longer recurrence-free survival than non-responders (median not reached vs 13.4 months). confirmedas of 2023-06-01

    11. [11]

      On 28 August 2026 BioNTech ended a phase 2 trial of autogene cevumeran monotherapy in resected colorectal cancer after its data monitoring board saw a numerical overall-survival imbalance between arms; the pancreatic cancer trial IMcode003 continues. confirmedas of 2026-08-28

    12. [12]

      In a 2026 Nature report on 14 patients with triple-negative breast cancer given an individualised neoantigen mRNA vaccine after standard treatment, vaccine-induced T-cell responses persisted for years and 11 patients remained relapse-free for up to six years; the study had no control group. confirmedas of 2026-02-18

    13. [13]

      Merck and Moderna reported no new safety signals in INTerpath-001 and said they plan to present the data at a medical meeting and engage regulators on filings; full results had not been published as of the announcement. confirmedas of 2026-08-19

    14. [14]

      In a 2026 phase 1b/2 trial in 45 people with Lynch syndrome, a hereditary cancer syndrome, the off-the-shelf neoantigen vaccine Nous-209, which encodes 209 frameshift neoantigens shared across mismatch-repair-deficient tumours, caused no intervention-related serious adverse events and induced neoantigen-specific immune responses in all 37 evaluable participants, still detectable at one year in 85%. confirmedas of 2026-01-16

    Revision history (2)
    1. Page created.
    2. Refresh: added 2026 data from an individualised mRNA vaccine in triple-negative breast cancer and the shared-neoantigen vaccine Nous-209.

    Created Oct 10, 2026. Last reviewed by an editor on Oct 10, 2026. Next scheduled review: Jan 10, 2027.

    Cite this page

    "How cancer vaccines work, from shared antigens to personalised mRNA." ContentLora, updated Oct 10, 2026. https://contentlora.com/explain/how-cancer-vaccines-work

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