Experimental mRNA vaccine cuts risk melanoma returns by 42%

By Meg Tirrell, CNN

(CNN) — When the news arrived in August that what could be the first personalized mRNA cancer vaccine had succeeded in a late-stage clinical trial in melanoma, oncologists and the public alike were exhilarated. And that was before its makers had even disclosed just how well the therapy worked.

Now they have. Patients who got the experimental vaccine, along with the approved drug Keytruda, had a 42% lower risk of their cancer coming back after surgery or of dying than if they got Keytruda alone, opening a path for an entirely new way to treat the disease.

“This new vaccine is something that we’ve never really seen before in terms of the efficacy that it has demonstrated and the way that it works,” Dr. Michael Postow, chief of the melanoma service at Memorial Sloan Kettering Cancer Center, told CNN.

The vaccine is called intismeran autogene until it receives a brand name.

The results are set to be presented Saturday in Madrid at a meeting of the European Society for Medical Oncology. Merck and Moderna, the developers of the experimental vaccine, released the data early, on Thursday, after reports that they’d been published online and then taken down.

Based on the results, the companies are “engaging with regulatory authorities,” they said in a news release, implying that they may file for US Food and Drug Administration approval imminently. They’re also testing the technology in many other cancer types, including lung and pancreatic cancers.

From Covid to cancer

The experimental vaccine uses the same mRNA technology that underpins Moderna’s vaccine for Covid-19, but instead of training the immune system to fight a viral invader, it helps it deploy more forcefully against cancer cells.

And it’s tailor-made for each individual patient, based on the genetic signature of their tumor. Once the cancer is removed through surgery, a sample is sequenced, and the vaccine is designed based on the markers in the tumor most likely to generate an immune response.

“This personalized cancer vaccine is a specific type of treatment that boosts the body’s immune response only against the cancer cells that are there,” Postow said, “and therefore it is a much more targeted immune boost directly against that patient’s individual tumor.”

Postow worked with patients enrolled in the trial, including 59-year Beth Ryzyk, who was diagnosed with stage IIIC melanoma in December 2023. That stage means the cancer was a certain thickness in the skin and had spread to her lymph nodes, raising the risk it could come back after surgery.

“We wish that surgery alone would be curative, but we know from many, many studies that patients in that situation have a very high likelihood of it coming back at some place, either in additional lymph nodes or other parts of the body like the bones or liver or lung or brain,” Postow said.

Patients are then prescribed therapy to try to prevent that from happening, in what’s called the adjuvant setting – meaning after a primary treatment; in this case, surgery. That’s typically a drug like Keytruda, which itself was revolutionary when approved in 2014. It works by enabling the immune system to unleash itself on cancer cells that previously may have remained hidden.

Building on Keytruda’s success

Keytruda was famously used to treat President Jimmy Carter for melanoma that had spread to his liver and brain. Carter announced that he was cancer-free in December 2015.

Ryzyk, like the other 1,136 participants in the trial, still doesn’t know whether she received the experimental vaccine or a placebo along with Keytruda (which all patients received) – although she suspects that she got the vaccine because after every treatment, she felt “a little sick, just a little flu and kind of down the next day.”

The experimental vaccine – or the placebo – was given as an intramuscular injection every three weeks for up to nine doses, while Keytruda was administered via intravenous infusion every six weeks for up to about a year, so Ryzyk didn’t always receive them at the same time.

What she does know is that more than a year after finishing treatment in the trial, she’s still cancer-free.

“I’m good; sometimes I even forget about it,” Ryzyk told CNN. “It’s always in the back of your mind … but they’re watching.”

The trial results, showing a 42% reduction in the risk that cancer recurred, were from a median of about two years after treatment. The trial will continue so other measures can be assessed, including the durability of the effect, as well as the most important metric: overall survival, whether the treatment helps patients live longer.

The companies said that at this point, it’s too early to say, “but a favorable trend” in improving overall survival “has been observed.”

Moderna’s rollercoaster ride

Despite results that oncologists such as Postow view as very positive, Wall Street reacted negatively to the news Thursday, sending Moderna’s stock price down 18% before the market closed. Merck’s shares declined 1.8%.

Analysts such as Trung Huynh at financial firm RBC Capital Markets pointed out that the results weren’t quite as strong as those seen in an earlier, smaller trial but said in a research note that the FDA is likely to approve the therapy next year.

Investors in Moderna in particular are keen to see evidence that this approach works not just for melanoma but other cancer types, given the biotech company’s rollercoaster fortunes in delivering mRNA vaccines for Covid-19 and then facing a flattening of demand once the acute phase of the pandemic passed.

They see a salvation in the application of mRNA technology in cancer treatment; Moderna’s stock more than doubled in price in August on the news that the trial had succeeded, and it has continued climbing since. Even with Thursday’s drop, the shares were up more than 500% year-to-date, noted William Blair analyst Myles Minter, who called the results “great data.”

Ryzyk said she hopes that others have a chance to benefit from this new way of treating cancer and that it won’t be priced out of reach for patients. Drug companies typically don’t announce the cost until a medicine is approved.

After ringing the bell at her treatment center last spring to signify the end of her therapy there, Ryzyk said, she’s returned to a life she loves, filled with travel with her husband.

“We’re in full-on retirement mode,” Ryzyk said, noting that they’ve got grown children but no grandkids yet, what she called a “sweet spot” for being able to explore the world. “We can just up and go. So we’re going.”

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