Results from INTerpath-001, a Phase 3 trial of a personalised mRNA cancer vaccine, appeared online on Thursday 22 October, two days before their scheduled presentation at the ESMO Congress in Madrid. Given alongside immunotherapy after surgery, the vaccine reduced the risk of melanoma returning, or death, by 42%. The same approach is now in Phase 3 trials in lung cancer.
Lung Cancer Europe is in Madrid for ESMO 2026, where several lung cancer trials are also reporting results this weekend.
How the INTerpath-001 results leaked before ESMO 2026
INTerpath-001 was due to be presented on Saturday 24 October as the lead late-breaking abstract in the ESMO Presidential Symposium, the congress's highest-profile session.
Conference results are shared with journalists in advance under embargo, an agreement not to publish before a set date and time. This gives reporters time to read the data and seek independent comment, and means the full findings are released together.
At around 17:30 UK time on Thursday, the data appeared on an oncology news website and was removed shortly afterwards. ESMO confirmed the embargo had been breached and, as the data were now public, released the abstract and lifted the embargo on the full dataset. Moderna and MSD (known as Merck in the US and Canada) then published their official results.
INTerpath-001 results: 42% lower risk of melanoma returning
The trial tested intismeran autogene, also known as mRNA-4157 or V940, in 1,137 people with high-risk melanoma (stage IIB to IV) whose cancer had been completely removed by surgery.
All participants received pembrolizumab (Keytruda), an immunotherapy already used after melanoma surgery. Two thirds also received intismeran and the rest received a placebo. Neither participants nor their doctors knew who had which.
Compared with pembrolizumab alone, adding intismeran:
reduced the risk of melanoma returning, or death, by 42%
reduced the risk of melanoma spreading to distant parts of the body, or death, by 38%
Moderna and MSD describe it as the first positive Phase 3 result for a personalised mRNA cancer treatment.
Why Moderna shares fell after the leak
Moderna's share price had nearly quadrupled since August, when the companies announced the trial had met its goals without releasing the data. After Thursday's leak, shares fell by as much as 25%, trading was briefly halted, and the stock closed more than 17% lower. MSD closed down about 1.8%.
Investors had expected results closer to an earlier, smaller Phase 2b trial, where five-year follow-up showed a 49% reduction in the risk of recurrence or death. Analysts at Bernstein described the fall as investors selling once the news was out. The share price reflects investor expectations; the benefit seen by trial participants is unchanged.
How personalised mRNA cancer vaccines work
Intismeran is given to people who have already had surgery for cancer, to lower the chance of the cancer coming back.
After surgery, each person's tumour is genetically analysed to find mutations present in the cancer cells and absent from healthy cells. A treatment is then made for that individual, coding for up to 34 of these mutations. It trains the immune system to recognise cancer cells carrying them, while pembrolizumab helps immune cells attack.
Each treatment requires tumour sequencing and individual manufacture. Cost and production time will be central questions for health systems.
Personalised cancer vaccine trials in lung cancer
Moderna and MSD are testing intismeran in non-small cell lung cancer (NSCLC) through several trials:
INTerpath-002: Phase 3, 868 people with stage II to IIIB NSCLC completely removed by surgery, comparing intismeran plus pembrolizumab with pembrolizumab alone after surgery and chemotherapy
INTerpath-009: Phase 3, people with stage II to IIIB NSCLC who received pembrolizumab and chemotherapy before surgery and still had cancer cells in the removed tissue
INTerpath-014: Phase 3, 876 people with high-risk stage I NSCLC removed by surgery, comparing intismeran with or without pembrolizumab given as an injection under the skin, against placebo
INTerpath-013: Phase 2, people with advanced squamous NSCLC starting their first treatment
Most of these trials involve early-stage lung cancer, where surgery provides the tumour tissue needed to make each treatment.
Melanoma and lung cancer differ in their biology and in how they respond to immunotherapy. The lung cancer trials will need to report their own results before conclusions can be drawn for people living with lung cancer. Independent experts, including Professor Alan Melcher of the Institute of Cancer Research, have cautioned against assuming a single melanoma trial will translate across cancer types.
When could the personalised cancer vaccine be approved?
The full INTerpath-001 results will be presented at ESMO on Saturday 24 October. They have not yet been published in a peer-reviewed journal.
The results come from a planned interim analysis. The trial continues, to measure whether the treatment helps people live longer overall.
A US regulatory filing is in preparation, and Moderna expects a US launch in 2027. No European timeline has been announced. In Europe, approval would go through the European Medicines Agency, followed by national decisions on pricing and reimbursement in each country.
Lung Cancer Europe at ESMO 2026: access and affordability
President Debra Montague, Vice President Angeliki Souri and Head of Operations Melanie De Coster are in Madrid, meeting advocates and organisations from across the cancer community. Lung cancer trials reporting at ESMO this year cover small cell lung cancer, lung cancers with KRAS or EGFR mutations, and antibody-drug conjugates.
On Saturday, Debra Montague presents Lung Cancer Europe's research on the cost of lung cancer. We asked 1,161 people with lung cancer and their carers across 28 countries about the financial impact. Two in three were struggling.
Those findings bear directly on treatments like intismeran. Medicines made for one person at a time are likely to carry a high price, and people in lower-income European countries already wait more than 600 days for access to new medicines.
As personalised vaccine trials in lung cancer progress, Lung Cancer Europe is calling for:
access to clinical trials for people living with lung cancer in every European country
clear communication about what the evidence shows at each stage, so people can make informed decisions about their care
planning for pricing and access to begin before approval, so new treatments reach people across Europe without long delays
Sources
BBC News: First personalised cancer vaccine cuts risk of disease returning in major trial. https://www.bbc.co.uk/news/articles/cq0ld9g9e913o
Reuters: Merck/Moderna cancer vaccine cuts risk of death or recurrence in melanoma by over 40%. https://www.reuters.com/legal/litigation/merckmoderna-cancer-vaccine-cuts-risk-death-or-recurrence-melanoma-by-over-40-2026-10-22/
CNBC: Moderna shares plunge after cancer vaccine data leaks. https://cnbc.com/2026/10/22/moderna-stock-cancer-vaccine-data-leak.html
Merck and Moderna INTerpath clinical programme backgrounder. https://www.merck.com/wp-content/uploads/sites/124/2026/08/Merck-Moderna_INTerpath_Clinical-Program-Backgrounder.pdf
ClinicalTrials.gov: INTerpath-002. https://clinicaltrials.gov/study/NCT06077760