According to the registry entry, the trial was stopped for “Business Reasons.” Those two words are all the public record says about why Merck walked away from mRNA-5671, a cancer vaccine it was developing with Moderna.
The timeline starts in May 2018. The two companies signed a co-development agreement, and Merck put $125 million into Moderna’s Series H financing. Merck ran the clinical work. Moderna made and supplied the vaccine. Merck kept a further right. Should the concept be proven, it could pay Moderna an unnamed amount and take the vaccine forward jointly.
The vaccine, also coded V941, aimed at four common KRAS mutations at once: G12D, G12V, G13D and G12C. The phase 1 study, NCT03948763, began on 26 June 2019. The goal was to establish safety, tolerability and a preliminary dose for a phase 2 study. Patients got 1 mg of vaccine by intramuscular injection every three weeks for nine cycles, and the combination arms added a 200 mg pembrolizumab infusion.
Who it was for
Stage one tested the vaccine on its own and paired with Keytruda. Stage two opened expansion groups for three cancers: lung (non-small cell), colorectal tumours without microsatellite instability, and pancreatic adenocarcinoma. Every patient needed a confirmed advanced or metastatic tumour carrying one of the four mutations.
The exit
On 24 February 2022, Moderna, reporting fourth-quarter 2021 results, disclosed that Merck had ended joint development and returned every right to the vaccine. Moderna gave no reason for Merck’s decision, and said it was assessing whether to continue.
The study itself ran on for a while. The registry records an actual end date of 25 August 2022, with 70 participants enrolled. Moderna’s own pipeline chart, updated 3 November 2022, still listed the KRAS vaccine, mRNA-5671, at phase 1 with worldwide rights held by Moderna.
As of the registry’s last update, on 28 January 2025, the study was listed as terminated.
Sources
- ClinicalTrials.gov record NCT03948763
- Merck halts KRAS mutation cancer vaccine partnership with Moderna (BioSpectator, translated from Korean)
- Moderna KRAS vaccine program slide (Moderna pipeline presentation, last updated November 3rd, 2022)
