Moderna shares more than doubled on Wednesday, rocketing as much as 177% to a two-year high of $174.38, after the drugmaker announced its experimental melanoma vaccine cleared a major hurdle in a Phase 3 trial — instantly erasing years of investor skepticism about the company's post-pandemic future.

The rally added roughly $30 billion to Moderna's market capitalization in a single session, according to Yahoo Finance. Trading volume blew past 15 times the stock's 50-day average, and short sellers — who held roughly 13.5% of Moderna's available shares — were reportedly staring at record one-day losses.

What the drug actually did

The therapy, known as intismeran autogene and tested under the trial name INTerpath-001, is a personalized mRNA cancer vaccine built individually for each patient and paired with Merck's blockbuster immunotherapy Keytruda. In a trial of 1,137 patients with high-risk, surgically removed stage IIB-IV melanoma, the combination hit both of its primary goals — extending the time before the cancer returned and before it spread to distant parts of the body — according to Fortune. Earlier-stage data cited by analysts had shown the combo cutting the risk of recurrence or death by 49% and the risk of distant spread or death by 59%, compared with Keytruda alone.

"FOR MANY YEARS, THE IDEA OF CREATING AN mRNA TREATMENT DESIGNED SPECIFICALLY FOR AN INDIVIDUAL PATIENT'S CANCER WAS ASPIRATIONAL."

That line came from Moderna CEO Stéphane Bancel, who has spent much of the past two years defending the company's pivot beyond COVID-19 vaccines as sales of its original blockbuster collapsed. Merck's Dr. Dean Y. Li framed the science in blunter terms: "By intervening earlier ... the goal is to increase the possibility of cure."

The good news wasn't confined to Moderna. Merck shares jumped as much as 10%, touching an all-time high near $152.20. Rival mRNA player BioNTech climbed about 20%, Novavax gained roughly 6%, and the Nasdaq Biotechnology Index rose about 4.4% to a record close, according to Yahoo Finance.

Wall Street resets expectations

Analysts scrambled to update their models. Leerink Partners raised its 2032 sales projection for the personalized vaccine to $1.4 billion, up from roughly $1.2 billion previously. "It could be extremely profitable for the company," Peter Andersen, founder of Andersen Capital Management, told Yahoo Finance, describing the scale of the swing in investor sentiment.

The rally is a rare bright spot for a stock that has fallen more than 90% from its pandemic-era peak as COVID vaccine revenue dried up and Moderna's broader pipeline struggled to convince skeptics. Wednesday's data, while still short of a full approval, is the clearest signal yet that the company's bet on personalized cancer vaccines — long dismissed by some as a moonshot — could become a genuine second act.

Moderna and Merck are expected to pursue accelerated regulatory pathways with the new data in hand, though neither company has set a formal filing timeline. Analysts say the next catalyst to watch is overall survival data from future trial updates, which regulators typically weigh heavily before granting full approval for a therapy like this one.