CAMBRIDGE, Mass.-At 11 a.m. on Wednesday, Moderna's 4,500 employees stopped working. Meetings were canceled, workers stepped off production floors. Staff pushed furniture aside and crammed into the cafeteria inside the company's sleek, open-air headquarters as executives took the stage. Their remarks were broadcast to offices in the U.S. and Europe. Some tuned in from as far away as Asia.

Chief Executive Stéphane Bancel normally talks off the cuff at these sorts of events. But he was too emotional to trust his own memory, relying on a notecard instead. He told the staff that the company's decadeslong pursuit of using mRNA to treat cancer had a major breakthrough with melanoma patients.

The biotech billionaire compared that morning to the day the company announced its Covid vaccine data at the depths of the pandemic. "It is part of our responsibility to try to go after big bets that are hard," he said to the crowd. "Remember to tell your grandchildren one day, Aug. 19, 2026, was the day a new chapter started."

Employees toasted with sparkling wine and hugged. Some cried.

The story of Moderna has been one of profound highs and lows. After its Covid success, the company endured years of pressure from falling vaccine sales, conspiracy theories about its mRNA technology and attacks on its science from everyone from antivaxers on social media to Health Secretary Robert F. Kennedy Jr. Moderna's stock had plummeted more than 90% from its peak with investors thinking it was left for dead. Now, there's something indisputable to celebrate: technology that could have the potential to transform care for many forms of cancer.

"We've done a lot of zigzags, some very painful, some hard but joyful," Bancel said in an interview the day after the results were announced. "What happened in the last week has been amazing."

It is the kind of triumph that few biotech startups enjoy, much less twice. But like all promising science, success in research studies doesn't always translate to success in business. Moderna must still get its experimental drug approved by the U.S. government, which has halted hundreds of millions of dollars of funding for mRNA. Unlike traditional vaccines, Moderna's therapeutic cancer vaccine must be personalized to each patient, meaning it will be costly to make. And the company has yet to share the specific details about how well the treatment actually worked and in what percentage of patients.

"We don't have all of the data yet, and I think that's really needed," said Dr. Drew Weissman, a professor at the University of Pennsylvania who won a Nobel Prize for his work on mRNA technology. "We don't know how long it's going to last. So it certainly is a major milestone to cross, but the game isn't over yet."

Even so, Moderna's stock, which in June was one of the most shorted in the S&P 500, nearly tripled on the news Wednesday. The surge added $44 billion to the company's market value.

The success of its mRNA cancer vaccine, which Moderna has been developing in partnership with Merck for a decade, has been viewed as core to Moderna's survival. Covid put Moderna on the map, but sustainable growth is more likely to come from developing a blockbuster cancer drug.

Greg Byrne, who lives just outside Tucson, Arizona, has had two bouts of melanoma and ended up in an earlier Moderna study of this treatment after having surgery to remove the cancer. He said he has been melanoma-free for two years.

The 87-year-old says he feels healthy and is still able to play golf. He was so confident in the vaccines' success, in fact, that he says he bought Moderna stock when he started the trial two years ago.

The day the news about the vaccine's success came out "was a great day for me," Byrne said. "I have a vested interest."

Moderna was founded in 2010 on the premise that cells could be instructed to create their own medicine using mRNA. A group of scientists including venture-capital firm Flagship Pioneering founder Noubar Afeyan, MIT biomedical engineer Bob Langer and stem-cell biologist Derrick Rossi joined forces to form a company to see if mRNA could be used to teach the body to fight diseases.

In its early days, Moderna poured research and development dollars into the idea that mRNA could be used as a common underlying technology for different types of medicines. But Bancel, who became CEO in 2011, intentionally steered clear of oncology. The company focused instead on rare genetic diseases, where executives thought mRNA would be more likely to work.

In early 2013, Moderna hired physician-turned-McKinsey consultant Stephen Hoge to lead the company's new drug efforts. He showed Bancel scientific abstracts mapping out new mRNA concepts in cancer biology. Bancel told Hoge the company, which had fewer than 100 employees at that point, lacked the capital to explore it.

Later that year, money showed up. Patrick Degorce, an early Moderna investor and hedge-fund manager, reached out to Bancel after losing his wife to lung cancer, curious about the potential of mRNA for cancer. Bancel told him the same thing he'd told Hoge: the company couldn't afford to pursue it.

Degorce asked how much it would take to hire a couple of scientists to start playing with Hoge's ideas. Bancel gave him a back of the envelope estimate: half a million dollars.

Days later, an envelope arrived on Bancel's desk. Inside was a personal check for $500,000, a gift to the company from Degorce. With that, Moderna hired two cancer scientists. The fledgling biotech had an oncology program.

It set out to use mRNA technology to make custom-designed cancer vaccines: A person's tumor would be genetically sequenced-the process of finding mutations-and the company would make bespoke therapeutic vaccines to stimulate the immune system.

"It is a convergence of a lot of technology all at once," said Jeff Coller, an RNA biologist and a professor at Johns Hopkins University, who wasn't involved in the project.

Bancel pressed staff on the likelihood that cancer vaccines could work. The endeavor had become a graveyard for research: Despite more than a thousand attempts by other researchers to produce a therapeutic vaccine for cancer, almost none had succeeded in a meaningful clinical trial.

At the time, cancer drugs known as cell therapies were emerging with astronomical price tags. Bancel and Hoge knew that if they couldn't manufacture this bespoke therapeutic vaccine affordably, it would be doomed. "If it's a $5 million dose, let's not waste time," Bancel told Hoge.

Hoge spent a week holed up in a conference room with Moderna's top chemical engineer, sketching designs and estimating the cost. They were able to figure out a more affordable way to produce the vaccine, but it still was more than they could afford. Bancel and the board knew they'd need a partner.

In the spring of 2016, Bancel and Hoge traveled to New Jersey to pitch Roger Perlmutter, then in charge of research at Merck, the maker of one of the most successful cancer immunotherapy drugs, Keytruda. By the end of the meeting, Bancel and Hoge appeared to win Perlmutter over.

"I'm an immunologist. Stéphane is an engineer. So we come from quite different backgrounds. But the idea of tumor immunology was something that I'd been working on for a very long time," the former Merck executive said, admitting that he and many of his colleagues had doubts. "I had considerable skepticism."

Still, Perlmutter was willing to give it a shot. Merck agreed to pay Moderna $200 million in 2016, which went to funding research to see how the mRNA cancer vaccine would work in combination with Keytruda. Merck left open the possibility of entering into a full joint venture to develop the vaccine together after seeing the results of that study.

The companies conducted safety studies and then, by 2019, were able to start the mid-stage study that could begin to determine whether the vaccine worked. Just six months later, Covid hit. The company, which was fast out of the gate with an mRNA Covid vaccine trial in March 2020, was an obvious candidate for government funding. Moderna won more than a billion dollars from the Trump administration to speed up development of its shot. It was authorized for emergency use that December.

In its first two years, Moderna's vaccine generated roughly $36 billion in sales, cash that would go on to fund its oncology ambitions. The stock peaked near $500 a share.

In 2022, Merck committed to jointly developing and splitting potential profits from the cancer vaccine. A few months later, the companies announced that patients using it with Keytruda had a 44% reduction in the risk of melanoma recurrence or death compared with Keytruda alone, a surprisingly strong result.

"It was like, 'Holy cow guys, this worked-like, it worked,'" Hoge said. "I almost don't believe it."

While energizing to those who had been working on it, the result wasn't going to translate into revenue anytime soon, which is what the company badly needed. Covid vaccine sales were collapsing. In 2023, the company's sales fell by nearly two-thirds.

In the following years, Moderna announced plans to cut jobs and end research programs into things like a pediatric RSV vaccine and other cancer therapies. Under Kennedy, the U.S. government also canceled Moderna's contract to develop mRNA-based vaccines for pandemic influenza viruses.

"We're moving beyond the limitations of mRNA and investing in better solutions," Kennedy said at the time.

Investors were losing faith. Earlier this year, the short interest-a measure of how many people are betting a stock will fall-in Moderna hit 20%, a level signaling intense pessimism.

Tommy Hill, managing partner of a hedge fund that focuses on distressed companies, saw Moderna as an opportunity. He believed the vaccine business was worth more than Wall Street was giving it credit for and took a small stake.