Moderna Stock Explodes Over 100% After Cancer Vaccine Breakthrough

Moderna (MRNA) stock exploded over 100% in Wednesday pre-market trading, hitting $122.51 after the company and Merck (MRK) reported the first positive Phase 3 result for a personalized mRNA cancer vaccine.

The gain is pre-market only for now. Moderna last closed at $62.96 on Tuesday, and regular trading in New York had not yet opened at the time of writing.

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A First for Personalized mRNA Cancer Therapy

The Phase 3 INTerpath-001 trial tested a bold idea. Doctors read the mutations in a patient’s tumor. Moderna then builds a custom mRNA shot for that one person.

Moderna and @Merck today announced positive topline results from the Phase 3 INTerpath-001 trial evaluating adjuvant treatment with intismeran autogene, a novel investigational mRNA-based individualized neoantigen therapy jointly developed by Merck and Moderna, in combination… pic.twitter.com/v4DjH0r823

— Moderna (@moderna_tx) August 19, 2026

Each shot encodes up to 34 tumor targets, known as neoantigens. In effect, it teaches the immune system exactly what to hunt.

The trial enrolled 1,137 people with stage IIB to IV melanoma, an aggressive skin cancer, after surgery. Patients who got the shot plus Merck’s Keytruda stayed cancer-free longer than those on Keytruda alone. Moreover, the combination slowed the cancer’s spread to distant organs.

That matters because Keytruda is today’s standard treatment for these patients. Historically, nothing had beaten it in this post-surgery setting. According to the joint announcement, no mRNA-based cancer therapy had ever passed a Phase 3 test before.

The stakes are large. Merck expects about 112,000 new US melanoma cases and over 8,500 deaths in 2026 alone. An earlier mid-stage trial also cut the risk of recurrence or death by 49% at five years.

“These Phase 3 findings represent a pivotal moment for the field of cancer research. For many years, the idea of creating an mRNA treatment designed specifically for an individual patient’s cancer was aspirational. We are now helping turn that vision into a reality,” Moderna CEO Stéphane Bancel said in the statement.

Safety matched earlier studies, with no new signals reported.

What Comes Next for Moderna Stock

Few stocks needed a win this badly. Moderna peaked above $480 in August 2021, when COVID-19 vaccine sales made it a market favorite. The shares then lost over 90% of their value as that demand faded.

However, the recovery started before Wednesday. The shares had already more than doubled in 2026. Moderna’s stock comeback rests on a flu vaccine approval and a wider pipeline push.

Wednesday’s spike briefly pushed the stock near $130 before it settled around $122. Meanwhile, Merck gained about 6%. The move also rewards investors who tracked Covid-era stock comebacks earlier this year.

Caution still applies. Detailed efficacy figures remain unpublished, and survival data is still being collected. However, the companies plan to present full results at a medical meeting and to discuss filings with regulators.

The same drug combination is also in nine trials spanning lung, bladder, and kidney cancers. For now, one question hangs over the session. Can a pre-market double survive the opening bell?