Moderna’s Cancer-Vaccine Data Leak Spurs Panic Selling. Wall Street Wanted a Cure.

Moderna stock sold off after an oncology news website leaked trial results that were set to be presented at a medical conference. (Adam Glanzman/Bloomberg)

Key Points

Moderna and Merck released Phase 3 trial data showing their cancer vaccine combined with Keytruda reduced melanoma recurrence or death by 42%.
Moderna stock fell 18% on Thursday after the data leaked, as some investors had hoped for results showing an effective cure.
The trial results represent the first positive Phase 3 trial for an mRNA-based cancer therapy.

Moderna stock narrowly avoided its worst trading session on record after leaked data for its cancer-vaccine candidate triggered a wave of selling. But were investors right to panic?

Moderna and partner Merck were set to present an expanded dataset for their vaccine, intismeran autogene, at the annual meeting of the European Society for Medical Oncology (ESMO) this weekend. However, the embargo on the study was “breached,” ESMO later confirmed, prompting the organization and the partners themselves to release the results on Thursday.

The late-stage trial centered on patients who were at high risk of their melanoma returning after it had been surgically removed. The vaccine, tailored to the mutations in each patient’s tumor, was administered with Merck’s Keytruda, while other trial participants received Keytruda alone.

The combined treatment reduced the risk of cancer recurrence or death from any cause—known as recurrence-free survival—by 42%. It also lowered the chance of distant metastasis or death by 38%, achieving a key secondary endpoint. These findings represent the first positive Phase 3 trial for an mRNA-based cancer therapy.

While the results received a warm reception from the medical community, they failed to generate a similar reaction on Wall Street. Moderna stock sank 18% on Thursday and looked set to extend those losses as it fell 4.4% in premarket trading Friday. Merck, meanwhile, fell 2% on Friday morning after closing down 1.8% the previous session.

Bernstein analysts described the selloff as a “sell the news event” in a research note Thursday, calling the data “meaningful validation of Moderna’s individualized neoantigen platform.” Wells Fargo, similarly, posited that the slump “may be overdone.”

However, others conceded that the data—while solid on their face—may have fallen short of the most elevated expectations. BMO Capital Markets analyst Evan Seigerman noted that some investors were looking for a read-through to other tumor types. “These results are not enough to drive confidence amidst elevated expectations,” he concluded.

More results are expected—Moderna and Merck are testing intismeran in nine trials across various solid tumors.

Citi analyst Geoff Meacham similarly suggested that some investors were “assigning value to an effective-cure narrative,” even though the 42% figure versus Keytruda alone was “a clinically meaningful advance” with consistent efficacy regardless of disease risk level.

Investors sold anyway. Moderna’s stock spiraled Thursday as the leaked data spread rapidly across social media. At its lowest point, shares fell more than 26% to $180.80, putting them on track for their largest single-day percentage drop on record.

One of the most widely circulated talking points was that the data fell short because Moderna didn’t “cure cancer”—a point Meacham acknowledged. Supporting that level of confidence likely would have required an effect exceeding the “paradigm-shifting” 0.40 hazard ratio achieved by Rasonque, Revolution Medicines pancreatic cancer pill, which ignited its own investor frenzy earlier this year.

While the latest results establish intismeran as clinically relevant in melanoma, success in a relatively easier-to-treat cancer doesn’t automatically translate to malignancies with different biology, Meacham wrote. He emphasized that additional positive studies “remain necessary to support the broader platform value previously embedded in shares.”

Skeptical investors may have also seized on the 38% distant metastasis metric, which measures how well the treatment prevents cancer from spreading to other parts of the body or death. TD Cowen analyst Tyler Van Buren pointed out that the result was “less exceptional” than the benefit on lowering recurrence risk.

Questions remain about whether the data offer a read-through for other mRNA-based cancer vaccines —which, historically, hasn’t been a given. Earlier this year, BioNTech and Roche halted a trial of autogene cevumeran as a treatment for bladder cancer, citing a shifting standard of care. In August, a mid-stage trial in colorectal cancer was also terminated.

Several other vaccines showed promising immune responses in early testing but failed to improve disease-free or overall survival in later trials. As individual mRNA platforms rely on distinct technologies, intismeran autogene’s success in melanoma won’t necessarily translate to other platforms.

Speaking at a conference last week, Moderna President Stephen Hoge characterized intismeran as “a long shot by any stretch of the imagination” in its early development days.

Still, he emphasized that the company continues to explore the vaccine’s potential across other indications. “We have a lot of exploring to do, and we have to prioritize where we explore,” Hoge said.

Intismeran may have stumbled on Wall Street, but the real test is only beginning.

Write to Mackenzie Tatananni at mackenzie.tatananni@barrons.com

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