A cancer vaccine seems to be closer than ever

Scientists are on the cusp of fulfilling a decades-long quest: to use vaccines to teach the immune system to spot and destroy cancer cells. News that an mRNA cancer vaccine developed by Merck & Co. and Moderna Inc. kept melanoma from returning in a large, late-stage trial marks a critical next chapter for a technology beleaguered by post-pandemic political backlash and years of false starts before then, according to the Tribune News Service.

The concept of cancer vaccines has been kicked around for over a century, and in the past 20 years, we’ve seen countless hopeful headlines about promising early-stage treatments. None of it panned out. Coaxing the body into fighting its own battles turned out to be a lot harder than it sounds.

mRNA is finally moving the field beyond the “hope” and “promise” phase. Merck & Moderna’s Phase 3 study combining the personalised mRNA-based vaccine intismeran with the immunotherapy Keytruda is offering the evidence needed to prove that cancer vaccines really can work.

There’s still plenty to do to show their potential extends beyond melanoma and into other kinds of cancer. But there’s enough data out there now to get excited, as reflected by Moderna’s stock price, which more than doubled on Wednesday. Success in this late-stage trial was critical to proving that mRNA is more than just a one-trick pony for combatting infectious diseases. (To be clear, it has been a stunningly effective one-trick pony that benefitted billions of people around the world coming out of the COVID-19 pandemic.) Long before the word “COVID” had entered the modern lexicon, companies developing mRNA technology were focused on its potential in cancer. In fact, Merck and Moderna have been working together to develop bespoke cancer vaccines for more than a decade. The design of such a vaccine sounds straightforward. Scientists genetically sequence a patient’s tumor to pinpoint the mutations driving their cancer.

Strands of mRNA carrying the instructions for building those mutated proteins are then packed inside a vaccine (intismeran contains mRNA strands that encode for up to 34 of them). Think of it like handing immune cells a series of mugshots of the enemy so they know exactly whom to attack — not only in the near term, but ideally for years to come.

That’s the bigger dream of cancer vaccines, that patients could be spared the constant anxiety their disease could at any moment roar back. Finally, that feels much closer to reality, but just how close remains to be seen. Merck and Moderna delivered their results via press release, and didn’t include numbers to show the magnitude of intismeran’s benefit to patients.

Still, what we know so far is impressive. Adding the vaccine to treatment with Keytruda lengthened the time before people’s melanoma returned, as well as the time before tumours appeared in other parts of the body. And in June, the companies reported results from a smaller study that followed patients for five years and found intismeran and Keytruda lowered the chances of melanoma returning or metastasising by 49% compared to Keytruda alone. Moreover, Keytruda, which has become the standard of care in melanoma since its arrival in 2014, has already greatly improved and extended people’s lives. The cancer vaccine “hurdled an already high bar,” said Michael Postow, chief of melanoma service at Memorial Sloan Kettering Cancer Center. “That’s quite a big achievement.”

Merck plans to share the full data from the intismeran study at an upcoming medical meeting or in a journal, and oncologists will comb through it to understand not only how much longer it can keep cancer from recurring or spreading, but whether certain patients fare better than others. They will also be looking for clues about how the vaccine fits into current treatment strategies.