Moderna Stock Plunges 18% As Leaked Melanoma Vaccine Data Underperforms
Moderna (MRNA) stock dropped 18% after leaked late-stage trial data for its melanoma vaccine showed a 42% risk reduction, lower than an earlier study's 49%. The stock fell to $202.63, wiping $17B off its market value. Partner Merck also saw losses. Full results are due at a cancer conference on Saturday.
How this was made

The 30-second read
Why it matters
The leak precedes the official conference presentation, creating uncertainty around the trial's final readout.
Market read
Moderna's share price fell sharply on the first report of weaker trial data, signaling immediate trading risk.
What to watch
Potential for Merck's Keytruda combination to drive future sales despite the current miss.
Background
Moderna's personalized melanoma vaccine is part of its oncology portfolio, co‑developed with Merck's Keytruda.
Ticker impact
Leaked late‑stage melanoma vaccine data showed a 42% risk reduction versus 49% previously, triggering an 18% stock plunge.
likely continued downside as investors reassess the vaccine's market potential
First disclosure of under‑performing trial data; the stock already fell 26% intraday and closed down 18%.
Market effects
Biotech sector may see broader risk‑off pressure on oncology pipelines.
U.S. biotech stocks could face heightened volatility in the near term.
Global investors tracking cancer‑therapy developments may adjust exposure.
Counterpoint
If the vaccine still meets regulatory endpoints, the dip could be an overreaction.
Key entities
- companyModerna, Inc.
Biotech firm developing the melanoma vaccine.
- companyMerck & Co.
Partner providing Keytruda for the combination therapy.



