Moderna (MRNA) shares showed impressive growth of more than 100% in premarket trading on Wednesday, reaching $122.51. The reason for such a sharp surge was the publication of the first positive results from the Phase 3 clinical trial of a personalized mRNA cancer vaccine being developed jointly with pharmaceutical giant Merck (MRK).
The explosive growth has so far only been recorded in over-the-counter trading. For context: on Tuesday, Moderna shares closed at $62.96 on the New York Stock Exchange, and at the time of writing this analysis, the main session had not yet begun.
First-ever success for personalized mRNA cancer therapy
This concerns the INTerpath-001 study, which tested a fundamentally new approach. Doctors analyzed mutations in each individual patient's tumor, after which Moderna created a personalized mRNA vaccine encoding up to 34 tumor targets (neoantigens). In essence, the drug teaches the immune system to precisely recognize and attack malignant cells.
The study included 1,137 patients with stage IIB–IV melanoma — one of the most aggressive forms of skin cancer — after surgical removal of the tumor. Key result: patients who received the vaccine in combination with Merck's Keytruda remained relapse-free longer compared to those who took only Keytruda. The combination also slowed the spread of cancer throughout the body.
This is particularly significant because Keytruda is considered the standard of care for such patients, and previously no treatment had surpassed its effectiveness after surgery. Moreover, as emphasized in the companies' joint statement, no mRNA cancer therapy had previously passed a Phase 3 trial successfully.
The scale of the problem is enormous: in the U.S. alone, Merck expects about 112,000 new cases of melanoma in 2026 and more than 8,500 deaths. In an earlier interim study, the combination already reduced the risk of recurrence or death by 49% over a five-year horizon.
"The Phase 3 results are a turning point for oncology. Until recently, the idea of creating an mRNA drug tailored only to a specific patient's tumor seemed unattainable. Now we are bringing that goal closer to reality," said Moderna CEO Stéphane Bancel.
The drug's safety profile remained unchanged — no new side effects were identified.
Outlook for Moderna shares
The market had long been waiting for such a catalyst. Since August 2021, when shares traded above $480 on the wave of COVID vaccine success, the stock has lost more than 90% of its value. However, in 2026, shares have already more than doubled, helped by the approval of a flu vaccine and an expanded product pipeline.
On Wednesday, shares briefly rose to nearly $130, closing near $122. Merck shares gained about 6%. Such growth certainly brings profits to investors who were tracking the rebound of "COVID stocks" earlier this year.
However, caution remains. Full efficacy data have not yet been published, and information on patient survival is still being collected. The companies plan to present all results at a medical conference and discuss them with regulators. The same drug combination is currently being tested in nine trials against lung, bladder, and kidney cancers. The main question remains: will the premarket growth hold after the main trading session opens.
My view: this is not just a corporate success, but a paradigm shift in oncology. However, for investors, it is important to separate the scientific breakthrough from market valuation. The current surge already prices in significant expectations, and volatility after the release of detailed data could be high. A sensible strategy is to follow regulatory steps and survival data rather than chase the emotional impulse.