Hong Kong-listed pharmaceutical stocks plunged sharply, and memory-related stocks also tumbled significantly—what happened?

Meanwhile, Hong Kong-listed pharmaceutical stocks crashed: GenScript Biotech fell 14.5%, Crystal Pharma Holdings and Insilico Medicine both dropped over 10%, while Ascletis Pharma, Ascentage Pharma, Harbour BioMed, CloudOne Therapeutics, and Zai Lab all declined more than 5%. CanSino Biologics—the leading vaccine stock—plunged 6.55%, at one point falling over 9%. The sharp decline in pharmaceutical stocks stemmed primarily from the slump of U.S.-listed vaccine giant Moderna, which dragged down the broader U.S. pharmaceutical sector overnight; Moderna plummeted 8%, yet its market capitalization remained as high as $74.8 billion. Amid persistent declines across the broader Hong Kong stock market, Hong Kong-listed pharmaceutical stocks had demonstrated relatively strong performance overall—benefiting from Moderna’s R&D progress on its melanoma vaccine. CanSino, having built its own mRNA technology platform and widely viewed by the market as the ‘domestic proxy’ for Moderna’s breakthrough cancer vaccine, surged over 62% since August 18. Moderna’s steep drop resulted from three main factors: First, excessive prior gains—the company’s share price skyrocketed from $63 to a peak of $212 in under two months starting August 18, representing a 237% surge and a near-$60 billion increase in market capitalization. Second, exhaustion of short-term catalysts: Following its sharp rally, Moderna was added to the Nasdaq-100 Index, effective October 9. Third, Citigroup turned bearish: although it raised its price target, it slashed its rating from ‘Neutral’ to ‘Sell’, citing that the stock had surged 222% since the interim results of the INTerpath-001 cancer trial were announced—rendering its valuation excessively high.

Moderna plunged up to 26%—setting a record for its largest single-day decline! Clinical data for its melanoma vaccine leaked prematurely, and results fell short of expectations.

Clinical trial data for the personalized melanoma vaccine jointly developed by Moderna and Merck unexpectedly leaked ahead of schedule, failing to meet market expectations and triggering a sharp selloff in Moderna’s shares. This data leak not only dampened investor sentiment but also challenged the long-standing optimistic outlook on mRNA-based cancer therapies. On Thursday, Moderna’s stock plunged as much as 26% intraday—setting a new record for its largest single-day decline—before partially recovering to close down 17.6%; Merck closed down 1.8%. Despite the sharp drop, Moderna’s stock remains up 655% year-to-date. The data showed the vaccine reduced the risk of cancer recurrence by 42% and lowered the risk of distant metastasis (i.e., tumor spread to distant organs) by 38%—results below some investors’ expectations, given the high hopes previously placed on this therapy. The data was originally scheduled for formal release this Saturday at the European Society for Medical Oncology (ESMO) Annual Congress in Madrid—but instead leaked prematurely via unverified accounts on the social media platform X. The leak triggered panic selling across markets. Moderna and Merck subsequently confirmed the leak and announced plans to officially release the full results of the Phase III INTerpath-001 clinical trial. Market caught off guard by premature data leak The leak originated from multiple unverified accounts on X, one of which posted a report attributed to ‘Oncology Central’ detailing the trial results. However, the URL link included in the report was inaccessible. Once the news spread, Moderna’s and Merck’s stocks immediately came under pressure. Only afterward did the two companies confirm the authenticity of the leak. The vaccine’s official name is intismeran autogene, administered in combination with Merck’s blockbuster immuno-oncology drug Keytruda. The trial enrolled over 1,100 patients—all at high risk of melanoma recurrence following surgical resection—and compared outcomes for those receiving the combination therapy versus a control group receiving Keytruda alone.

Moderna sheds about $24 billion as cancer vaccine data triggers 'sell-the-news' retreat

Oct 22, 2026

Moderna shares fell over 25%, wiping out $24 billion in value, following late-stage trial data showing its melanoma vaccine reduced recurrence risk by 42%. Analysts described the reaction as a typical 'sell-the-news' event despite the compelling clinical results.

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