Moderna Shares Plunge 25% Following Cancer Vaccine Data Leak

On Thursday, October 22, Moderna shares plummeted by as much as 25% following an early leak of partial data regarding the Merck and Moderna cancer vaccine on an oncology website, bypassing the official release. This steep decline seemed contradictory given that the vaccine actually reported positive news, demonstrating a 42% reduction in the risk of melanoma recurrence or death when combined with Merck’s Keytruda. By the market close, the share price settled at $202.63, marking a decrease of $43.18 or 17.57%.

Moderna Stock Drop Follows Cancer Vaccine Data Leak Despite Positive Results

Currently, this market dip appears to be the result of soaring expectations colliding with actual figures. Prior to the leak, shares had nearly quadrupled since August—when the two companies announced trial success while withholding the precise data. Although the plunge wiped out a major portion of that recent surge, Moderna still maintained a year-to-date increase of roughly 587% at the time of writing, operating within a 52-week range spanning from $22.28 to $254.48.

What The Merck Moderna Cancer Vaccine Trial Showed

Designated as INTerpath-001, the Phase 3 trial involved 1,137 melanoma patients who had undergone surgery. Referred to as intismeran autogene, the vaccine analyzes the distinct mutations present in each individual’s tumor to train the immune system to target them.

When administered alongside Keytruda, the treatment lowered the risk of recurrence or death by 42% and decreased the risk of distant spread or death by 38% relative to Keytruda by itself. After a two-year period, 82.2% of patients receiving the combination therapy remained cancer-free, compared to 70% of those receiving only Keytruda. Furthermore, the risk reduction benefit increased to 58% following the completion of the six-month vaccine regimen. These metrics appeared robust on paper, which explains why the sudden sell-off caught many observers by surprise.

Dr. Dean Y. Li, president of Merck Research Laboratories, stated:

“INTerpath-001 is the first Phase 3 study to demonstrate a clinically meaningful improvement in RFS and DMFS over standard-of-care KEYTRUDA in patients with resected melanoma, setting a new benchmark in the adjuvant setting and representing one of the most significant advances in melanoma treatment since the advent of immunotherapy. These results, building on the body of evidence from the Phase 2b study, strengthen our confidence in the curative potential of intismeran autogene when given in combination with KEYTRUDA. Importantly, these data suggest that, by intervening earlier, this approach may offer a tangible opportunity to change the trajectory of a patient’s cancer.”

Why The Moderna Stock Price Fell Anyway

Analysts generally agree that market reaction was driven by valuation expectations rather than scientific shortcomings. Prior to the disclosure, several Wall Street analysts indicated that investors were looking for a risk reduction of 40% or higher, with many having anchored their hopes on the earlier Phase 2b study which suggested a more pronounced effect, according to RBC Capital Markets. Although the 42% figure met that threshold, it did so only narrowly, leading to the price retreat alongside a 1.8% drop for Merck shares. Moderna moved from a previous close of $245.81 down to an intraday low of $180.80, with approximately 49.8 million shares trading hands—more than double the standard 20.2 million daily volume.

Evan Seigerman, an analyst at BMO Capital Markets, attributed the downward movement to inflated expectations rather than deficient efficacy, while UBS analysts similarly characterized the dataset as robust overall. Conversely, Trung Huynh of RBC offered a more cautious perspective, noting that melanoma should have represented the optimal scenario for the vaccine.

What Moderna And Merck Plan From Here

Stéphane Bancel, CEO of Moderna, indicated that both organizations are preparing to submit applications for US regulatory approval, targeting a commercial launch for the vaccine in 2027. Comprehensive trial data is scheduled for an official presentation on Saturday at the ESMO Congress held in Madrid. Additionally, Merck and Moderna are currently evaluating the combination therapy for kidney, bladder, and lung cancers. Nonetheless, this future outlook did little to cushion the immediate market reaction on Thursday.

Moderna Chief Executive Officer Stéphane Bancel offered these remarks:

“From the beginning, we believed mRNA technology could make it possible to develop cancer treatments uniquely matched to each patient’s tumor. The INTerpath-001 results mark a defining moment for that vision and show what’s possible when we rethink how medicines are made. These results reinforce our conviction that mRNA has the potential to fundamentally change how we treat cancer.”

Ultimately, the recent price contraction reflects the lofty benchmarks established by market participants rather than deficiencies in the medical treatment itself. Investors who acquired shares near peak valuations and weathered the downturn will likely focus on upcoming developments, including trial readouts for other oncology indications and the upcoming earnings report scheduled for November 6, which could introduce further volatility.

?Frequently Asked Questions

01Why did Moderna stock drop despite positive cancer vaccine data?

The stock price fell because investors had set exceptionally high expectations ahead of the leak, anchoring their hopes on an earlier Phase 2b study that showed a larger effect. Although the Phase 3 trial’s 42% risk reduction met expectations, it did so only narrowly, triggering profit-taking and a sell-off.

02What are the key results of the INTerpath-001 trial?

The trial showed that combining the Moderna cancer vaccine (intismeran autogene) with Merck’s Keytruda cut the risk of melanoma recurrence or death by 42% and the risk of distant spread or death by 38%, compared to Keytruda alone.

03When is the cancer vaccine expected to launch?

Moderna and Merck are preparing to file for U.S. approval, with expectations to launch the cancer vaccine in 2027.

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