Shares in Moderna and Merck, known as MSD outside of the US and Canada, soared after their personalised cancer vaccine helped cut the recurrence of melanoma in a large, late-stage trial, an important milestone for the embattled mRNA-based technology.

The trial met its main goal of showing that the vaccine, combined with Merck’s immune drug Keytruda, reduced melanoma recurrences more than the immunotherapy alone. The study also met a key secondary goal of slowing the cancer’s spread to new areas of the body, the companies said in a statement on Wednesday.

The study, the first positive final-stage trial for any mRNA-based cancer therapy, is a welcome respite for both companies. It provides the strongest evidence yet that the technology that made Moderna a household name during the pandemic will have a successful second act. For Merck, facing a patent loss for its best-selling drug Keytruda, it offers a key new market for future growth.

Moderna shares more than doubled in pre-market trading in New York, while Merck rose almost 9 per cent.

Details on how much the shot improved recurrence-free survival — the amount of time a patient lives without their cancer coming back — weren’t released. The trial remains ongoing to assess whether patients who get the vaccine live longer.

Melanoma is the most serious form of skin cancer. In the US, roughly 112,000 people are diagnosed with it each year and about 8,500 people die from it, according to the American Cancer Society.

The companies will discuss filing for approval with regulators and will present the data at an upcoming medical meeting, according to the statement. In an interview, Moderna chief executive Stéphane Bancel said the product could be approved as soon as 2027, depending on the outcome of the regulatory review.

“It is an extraordinary milestone for mRNA science,” Bancel said.

Still, questions remain about the cost and feasibility of producing such bespoke cancer treatments at scale. And the companies will need to prove that the vaccine works in other tumor types beyond melanoma.

The two companies have been working on the science behind the vaccine, called intismeran autogene, for more than a decade. Developed using the messenger RNA technology that powered Moderna’s Covid-19 shot, the companies customize each shot based on a patient’s specific tumor mutations.

It takes about six weeks to make the shot. Scientists take a sample of the patient’s tumor, either from existing tissue or a new biopsy, and analyze it for mutations.

An algorithm identifies which are most likely to provoke an immune response, and up to 34 of them are used to produced the personalized vaccine, said Jane Healy, head of oncology early development at Merck. During that waiting period, patients continue to receive Keytruda.

In the trial, the mRNA vaccine was given in combination with Merck’s Keytruda to patients after their tumors were surgically removed. A control group of patients in the study were treated with Keytruda alone, a standard treatment used to prevent recurrence in patients at risk.

The goal is for the two drugs to work together to train the body’s immune system to attack any remaining cancer cells.

Moderna’s stock had shot up 113 per cent from the beginning of the year through Tuesday’s close on the prospects of the cancer shot. The melanoma trial was seen as a crucial early test of how well the approach would work. Merck and Moderna are testing it in other types of cancer, including lung cancer, but the melanoma studies are the furthest along.

Scientists have long chased the idea of a vaccine that could turn the body’s own defenses against cancer, teaching the immune system to recognize a tumor’s molecular fingerprints and destroy the cells that remain. But, until now, it’s proven very difficult to get them to work.

“Therapeutic vaccines have been something of a holy grail in cancer. People have been trying to do this for, you know, over 100 years in one way or another,” Healy said in an interview several weeks before the results were released. She said one potential benefit of such a shot would be extending survival without adding many more side effects.

The companies said earlier this year that skin cancer patients in a mid-stage trial who got the mRNA shot with Keytruda were 49% less likely to die or have their cancer return after five years than those who received Keytruda alone. --Bloomberg