Moderna shares MRNA plunged on Thursday after partial data from its closely watched cancer vaccine trial leaked ahead of a scheduled presentation at the European Society for Medical Oncology conference, triggering a sharp sell-off despite results that analysts described as clinically meaningful.
The stock fell as much as 25% during the session, while trading was briefly halted due to volatility.
The stock recuperated some of the losses and was trading down 16% at the time of writing.
The decline followed the circulation of trial results online after oncology news website Oncology Central published information that was subsequently removed.
The European Society for Medical Oncology confirmed that the study abstract’s embargo had been breached and lifted the embargo on the full dataset later on Thursday.
The vaccine, intismeran autogene, is being developed by Moderna in partnership with Merck.
It is designed to be administered alongside Merck’s Keytruda immunotherapy to treat high-risk melanoma patients.
Cancer vaccine reduces recurrence risk by 42%
The trial results showed that adding intismeran autogene to Keytruda reduced the risk of cancer recurrence or death by 42% compared with Keytruda alone.
The combination produced a hazard ratio of 0.58 for recurrence-free survival, which measures the period until cancer returns or a patient dies.
The data also showed that approximately 82% of patients who received the vaccine alongside Keytruda were alive without their melanoma returning after two years, compared with 70% of patients treated with Keytruda alone.
The combination reduced the risk of cancer spreading to distant organs or tissues, or death, by 38% compared with Keytruda alone.
Despite the positive findings, the market reaction suggested investors had anticipated particularly strong results ahead of the detailed Phase 3 presentation scheduled for the weekend.
BMO Capital Markets analyst Evan Seigerman said in a research note that the relative reduction in recurrence or death was clinically meaningful.
He added that the stock’s reaction likely reflected elevated expectations rather than a negative assessment of the treatment’s effectiveness.
Elevated expectations weigh on Moderna shares
Several analysts had outlined expectations for the trial results before the data emerged.
UBS analyst Michael Yee had suggested that a hazard ratio of 0.65 could support a 10% to 20% rally in Moderna shares, while William Blair analyst Matt Phipps indicated that a result of 0.70 or lower would be well received.
Leerink Partners analyst Daina Graybosch had identified a figure below 0.60 as a potentially transformative outcome.
The reported hazard ratio of 0.58 was better than these thresholds, but the shares still declined sharply.
William Blair analyst Myles Minter described the move as a potential sell-the-news reaction, noting that Moderna shares had risen more than 500% this year despite Thursday’s fall.
UBS analysts also described the results as a strong dataset, suggesting that the stock reaction reflected high expectations rather than disappointing efficacy.
However, the reduction in the risk of cancer spreading to distant organs fell short of some Wall Street expectations, according to TD Cowen analyst Tyler Van Buren.
Vaccine offers potential beyond melanoma
Investors view intismeran autogene as a possible source of growth for Moderna beyond its existing vaccine portfolio, which includes products for COVID-19, influenza and respiratory syncytial virus.
Researchers are evaluating the personalised cancer vaccine across nine trials involving different solid tumours.
Positive results could also strengthen confidence in upcoming studies targeting kidney and bladder cancers.
The treatment’s manufacturing process remains a potential challenge.
Because the vaccine is personalised, production can take approximately six weeks.
Merck CEO Robert Davis said the company believes it can reduce that timeline in the future, potentially helping the treatment reach more patients.
Merck shares also declined on Thursday, falling around 1.4%, although the move was smaller than Moderna’s drop.
The sell-off leaves investors weighing the vaccine’s clinical promise against the high expectations already reflected in Moderna’s share price.
While the trial results indicate a meaningful reduction in melanoma recurrence risk, further studies and the treatment’s commercial potential will remain important considerations.
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