Phase 3 data for Merck & Co. and Moderna’s personalized mRNA cancer vaccine intismeran autogene were presented at ESMO’s Presidential Symposium in Madrid, days after a pre-conference data leak.
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CLINICAL CATALYST · ONCOLOGY VACCINES · OCTOBER 31, 2026 · EUROPE
Two days before the scheduled presentation, the headline phase 3 data for Merck & Co. and Moderna’s cancer vaccine leaked — yet the Alicante Auditorium at the European Society for Medical Oncology (ESMO) congress in Madrid still filled beyond capacity for Saturday’s Presidential Symposium, with latecomers standing at the sidelines, according to Fierce Biotech’s on-site reporting.
The vaccine is intismeran autogene, a personalized messenger RNA (mRNA) cancer vaccine developed by Merck & Co. and Moderna. Shweta Jain, vice president of global clinical development and oncology clinical research at Merck, told Fierce Biotech the leak was ‘unfortunate,’ but said the two companies stuck to their plan for presenting the data, which she called ‘convincing.’ Melanoma expert Georgina Long, Ph.D., presented the readout.
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Fierce Biotech spoke with senior executives from over 10 large pharmaceutical companies and biotechs at ESMO 2026; the overarching view was that the congress had no single dominant theme.
The leak did not suppress clinical interest, but it altered the environment in which the data landed. ESMO barred journalists and other non-prescribers from the exhibition halls under a new policy, citing European legislation governing the promotion of medical products. ESMO’s press office told Fierce Biotech it understood the ‘disappointment’ and ‘frustration’ the policy caused. Executives who spoke to Fierce Biotech on condition of anonymity speculated that the restriction was a reaction to the negative publicity around the leak.
A crowded ESMO package — and a contested inhibitor space
For Merck, intismeran autogene was the headline item in what Jain described as a packed presence featuring around seven oral presentations alongside ‘many, many, many abstracts and posters.’ That included two further presidential symposia: global phase 3 data for sacituzumab tirumotecan (sac-TMT), an antibody-drug conjugate (ADC) partnered with Kelun-Biotech, and the potential for pembrolizumab (Keytruda) in a type of endometrial cancer. Merck also presented early data on calderasib, its candidate in the KRAS G12C inhibitor space, in solid tumors. ‘Put together, it just generally shows that we are working towards a more diverse portfolio,’ Jain said.
The KRAS space drew pointed competitive commentary. Stefan Frings, M.D., Ph.D., deputy chief medical officer at Roche Pharma, namechecked Roche’s own KRAS G12C inhibitor divarasib, which beat Amgen’s Lumakras and Bristol Myers Squibb’s Krazati in a phase 3 non-small cell lung cancer (NSCLC) study, per Fierce Biotech. ‘Sometimes combination targeted molecules like divarasib are still very attractive,’ Frings said, adding: ‘It showcases here that we are making progress in treating cancer.’
Incyte’s Global Head of R&D, Pablo Cagnoni, M.D., is pitching the company’s KRAS G12D inhibitor INCB161734 as the main rival to Revolution Medicines’ zoldonrasib, according to Fierce Biotech. Cagnoni said his focus had been on ‘a lot of KRAS stuff happening,’ but offered a broader read: ‘I think it’s impossible at this ESMO to not talk about the Moderna [cancer] vaccine. There’s strong passions on both sides — I happen to think the data are really good.’
No single modality dominated
The overarching view among executives from more than ten large pharmaceutical companies and biotechs, as well as physicians and other attendees, was that ESMO 2026 had no theme. ‘I don’t see a theme, right?’ Cagnoni told Fierce Biotech. Frings offered a parallel summary: ‘I would expect that there’s not a single theme, but rather many attractive modalities.’
Yusri Elsayed, M.D., Ph.D., global oncology therapeutic area head at Johnson & Johnson Innovation, said his team was ‘excited to hear about’ the Merck and Moderna vaccine result, while pointing to degrader-antibody conjugates — a platform Johnson & Johnson acquired with Firefly Bio in June — as a mechanism to watch: ‘You don’t hear about it a lot, but definitely for next ESMO.’ Cagnoni separately highlighted Genmab’s phase 3 win for Rina-S in ovarian cancer, citing a survival hazard ratio of 0.43 in a first analysis.
At the prior year’s congress in Berlin, next-generation ADCs were broadly identified as the standout class, per Fierce Biotech. The shift to a fragmented picture — mRNA cancer vaccines, KRAS inhibitors across mutation classes, ADCs and emerging degrader-antibody conjugates side by side — suggests an oncology pipeline in which no single platform commands consensus. Cagnoni also pointed to artificial intelligence as a cross-cutting theme, with applications ‘from anything from diagnosis to patient care-directed applications.’
What to Watch
- Regulatory filing plans for intismeran autogene following the phase 3 readout
- Further data for calderasib in a KRAS G12C class where divarasib, Lumakras and Krazati are already active
- Johnson & Johnson’s degrader-antibody conjugate data, which Elsayed flagged for a future ESMO
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The leak may prove more consequential for conference governance than for the science. If ESMO’s restriction on press access to the exhibition halls becomes standing policy, it changes how information flows at one of oncology’s most closely watched forums — with downstream effects on how data reaches investors, payers and prescribers before peer review.
Why this is relevant
Patients
Phase 3 data for intismeran autogene, a personalized messenger RNA (mRNA) cancer vaccine, were presented at the European Society for Medical Oncology (ESMO) Presidential Symposium; patient access depends on regulatory filings and approvals that follow the readout.
Industry
Merck & Co.’s ESMO 2026 package — intismeran autogene, sacituzumab tirumotecan, pembrolizumab in endometrial cancer and early calderasib data — is what Jain called a move toward a more diverse portfolio, while Roche’s divarasib beat Lumakras and Krazati in a phase 3 non-small cell lung cancer (NSCLC) study, per Fierce Biotech.
Payers
The phase 3 readout gives intismeran autogene an evidence base, but coverage decisions will depend on regulatory filings, label scope and pricing, which makes the companies’ filing plans the next trigger for payer review.
Regulators
ESMO restricted journalists and other non-prescribers from its exhibition halls, citing European legislation on the promotion of medical products, a policy that executives speculated was linked to the vaccine data leak, per Fierce Biotech.
Sources: Fierce Biotech: From RAS rivalries to leaked cancer vaccine readouts, ESMO brought the data drama
THE HEALTHSIGNALS BRIEF
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Built for pharma, market-access, regulatory, policy and investor teams, with the main findings of our gated reports included.
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