Moderna’s mRNA Skin Cancer Vaccine Shows Early Promise in a New Study

Coming off the success of its mRNA vaccine for COVID-19, Moderna announced on Dec. 13 that it achieved encouraging results when it turned its vaccine technology against cancer.

The company reported in a release that among 157 people with stage 3 or stage 4 melanoma, a personalized cancer vaccine that Moderna developed with Merck—created using mRNA genetic material from each patient’s respective tumors—reduced the risk of recurrence or death by 44% compared to standard care.

“For the first time ever, we have evidence that it’s possible to develop a functional immune response that can treat patients’ cancer from a randomized controlled trial,” says Dr. Stephen Hoge, president of Moderna.

In the study, patients were randomly assigned to receive one of two treatments. One group was treated with the drug pembrolizumab, or Keytruda, an existing medication that releases the brake that the immune system normally has on attacking cancer cells, since cancer cells grow from the body’s own cells. The other group received Keytruda and a personalized cancer vaccine using mRNA technology. All of the patients had surgery to remove their melanoma, and for the vaccine group, Moderna scientists biopsied and genetically sequenced those tumors, then identified nearly three dozen genetic, personalized tumor flags, in the form of mRNA, for each patient’s immune system to recognize. These were then combined and injected in patients’ arms—in the same way that the COVID-19 vaccine delivered instructions to target the virus’ spike protein genes. Except in this case, the immune system was trained to target and destroy melanoma cells rather than a virus.

In the trial, patients received up to nine doses of the personalized cancer vaccine. “It’s much easier for the immune system to get hold of a virus and prevent a viral infection than it is to destroy cancer,” says Hoge. “So it takes a lot more doses to get the immune system built up with the right force and strength against [cancer] antigens to impact a patient’s cancer.”

More from TIME

Read More: The Race to Make a Vaccine for Breast Cancer

Patients were treated and monitored for at least two years. The company has only reported patient outcomes so far—not details of the vaccinated patients’ immune responses, such as their T-cell levels, which vaccines train to recognize and eliminate pathogenic cells. They are collecting that data and will provide that analysis in future presentations or publications.

Hoge says the key to the vaccine’s success is that it was tailored to each patient’s tumor, allowing each patient to mount a precise and targeted response to their cancer. The flexibility of the mRNA technology makes that possible, as COVID-19 vaccine development demonstrated. New COVID-19 shots with different viral targets were created and manufactured in about six weeks by both Moderna and Pfizer-BioNTech, makers of another mRNA COVID-19 vaccine. It also took about six weeks for Moderna’s scientists to generate each personalized mRNA cancer vaccine.

Hoge says the patients will be followed for at least one more year, and possibly more after completing the treatment. The company’s scientists will monitor how long-lasting the immune response is, and how well it holds up to future recurrences or metastases. If the results are confirmed, Hoge says it may also be possible to use the vaccine in people at earlier stages of the disease, or even in people without melanoma who are at higher risk for it to prevent them from developing tumors in the first place.

“We’re not there yet, and there is more work to do to figure out if we can push the 44% reduction even further,” he says. “But I do think this is a transformational moment for the field [of cancer treatment], for the company, and, we hope, for patients. We had a lot of success going after viruses, but nobody has ever demonstrated that mRNA vaccines could work in a randomized controlled trial in cancer. We are starting to show with data that they absolutely can, and that they can have a bigger impact in other fields than the one for which they became famous.”

BioNTech has also been working on mRNA cancer vaccines since before the pandemic. Its scientists have tested versions of its vaccine in smaller studies without rigorous controls yet.