How does the Moderna cancer vaccine that sent stocks surging 177% work?

Moderna stocks almost tripled on Wednesday (August 19) after the pharma giant completed trials of its new cancer vaccine. Called intismeran autogene, the new drug was given alongside Merck’s immunotherapy Keytruda. Researchers have noted that it reduced the chances of high-risk melanoma, a serious type of skin cancer, returning or spreading

Wednesday (August 19) was a good day for Moderna, the American pharmaceutical company based in Massachusetts. The biotech company not only saw a breakthrough in a cancer vaccine trial, but it also saw its stocks climbing 177 per cent in a single session.

The soaring stocks is a complete turnaround for the company whose shares have seen a decline recently after demand for the Covid-19 vaccine has waned.

But what is this cancer vaccine that Moderna is developing? And what does the trial reveal about this vaccine’s efficacy?

What is Moderna’s personalised cancer vaccine?

On Wednesday, pharmaceutical giants Moderna and Merck announced that their experimental vaccine treatment has shown signs of preventing cancer from returning or spreading in a study of high-risk melanoma patients.

Advertisement

Called Intismeran Autogene, it is based on the same messenger ribonucleic acid (mRNA) technology behind Covid-19 vaccines.

Researchers note that Intismeran is the first of its kind autogene therapy that relies on studying a patient’s cancer mutations, making mRNA sequences of those mutations and giving them back to the patient so their immune systems can recognise the tumour signals in the same way it would a virus — in what’s known as a therapeutic vaccine.

Georgina Long, the study’s principal investigator, UNSW professor and medical director of Melanoma Institute Australia, told ABC News that the way this vaccine works is that it takes a sample of the patient’s tumour, identifies its unique mutational signature, also known as a “fingerprint”, and then uses messenger RNA tech to fight it.

This messenger RNA tech became prevalent during the Covid-19 pandemic, when Moderna and Pfizer developed vaccines that were highly effective against serious forms of the illness.

The new drug developed by Moderna is based on the mRNA technology used for some Covid-19 vaccines. File image/Reuters

What did the trial reveal about the Moderna vaccine?

On Wednesday (August 19), the two pharma companies released interim results from phase three of their trial. The two firms noted that people with melanoma who received intismeran, jointly developed by Moderna and Merck, and Merck’s pembrolizumab (Keytruda), lived longer without any recurrence of their cancer, as well as had fewer incidences of their cancer spreading, compared to those receiving Keytruda alone, which is the current standard treatment.

Advertisement

In the trial, 1,137 high-risk patients with stage 2b to 4 melanoma that had been surgically removed were enrolled. Volunteers were randomised to receive ​up to nine doses ​of Keytruda plus the personalised vaccine or Keytruda alone for about one year.

Then in January, the firms revealed that the combined treatment of Intismeran with Keytruda reduced the risk of recurrence or death by 49 per cent after five years.

Detailed results of the study have not been released but are expected to be shared at an upcoming medical meeting, according to the drugmaker.

Nevertheless, the results are a positive sign for researchers and Moderna. Stephane Bancel, Moderna’s chief executive, told CNN, “This is a new chapter in cancer care.”

“For many years, the idea of creating an mRNA treatment designed specifically for an individual patient’s cancer was aspirational,” Bancel said in a statement. “We are now helping turn that vision into a reality.”

Other scientists and health experts also noted that the results from the vaccine seemed promising. Dr Janice Mehnert, who directs the melanoma medical oncology program at NYU Langone Health, told NBC News, “I’m just excited to see science win on this one. The idea of this incredibly novel, innovative idea actually panning out after years of work and literally over 1,000 patients is above and beyond what I would have liked to see.”

Advertisement

Dr Elias Sayour, a paediatric oncologist at the University of Florida, also echoed similar comments. In a New York Times report, he was quoted as saying, “It’s a big deal. The results could help usher a whole new wave of therapeutic treatments for cancer.”

The new vaccine is significant in medical research and the fight against cancer, say many experts. Representational image/Reuters

When will the Moderna cancer vaccine be available to patients?

According to Moderna president Stephen Hoge, thousands of patients who have undergone high-risk melanoma surgery could benefit as early as 2027.

This is a huge deal for patients of melanoma — a type of skin cancer. In 2023, in the US alone, more than 1.5 million people were living with this form of cancer.

Moreover, Moderna’s Bancel also told TIME that they were experimenting intismeran in stage 1 lung cancer. And while the testing is in very initial stages, he is optimistic since “from a scientific standpoint there is no scientific sense that it would work in melanoma and not work in another tumour type”.

How did the market react to the news of the vaccine?

Shortly after the news of the trial results was announced, Moderna stock soared about 177 per cent. Even Merck saw an upward movement of its stock — it climbed 12 per cent.

According to a Financial Times report, the results of the trial added $44bn to Moderna’s market capitalisation, taking it to $69.6 billion. Moreover, Moderna became the second-best performer in the S&P 500 index so far in 2026, trailing only memory group Sandisk.

Even Elon Musk hailed Moderna after its stocks zoomed upwards. Responding to an X post, he noted, “Despite its obvious misuse during Covid, mRNA has tremendous promise for curing diseases. Artificial RNA essentially makes curing diseases a software problem.”

It’s also a huge turnaround for the pharma giant, which has witnessed a significant stock drop in recent times. In fact, in 2025, the company laid off 10 per cent of its workforce, citing sagging sales and loss of important government contracts.

With inputs from agencies