The immune system, no longer hamstrung, could do its job.
Each year, lung cancer quietly claims 1.8 million lives — a toll that has long resisted medicine's best efforts. Now, researchers at the Francis Crick Institute in London have identified a conditional but meaningful breakthrough: pairing a drug that silences a rogue genetic mutation called KRAS with immunotherapy may successfully control certain lung cancers, specifically those whose tumors already hum with immune activity. The discovery is less a cure than a map — one that tells scientists not only where a promising path may lie, but also where previous clinical trials may have wandered off course by enrolling the wrong travelers.
- Lung cancer remains the world's deadliest cancer, killing 1.8 million people annually, with only one in four patients surviving beyond five years — a statistic that has driven urgent searches for new treatment combinations.
- KRAS, a gene mutated in roughly a third of all lung cancers, actively suppresses the immune system and shields tumors from attack, making it both a formidable enemy and a precise therapeutic target.
- In laboratory mice, the combination of a KRAS-blocking drug and immune checkpoint immunotherapy successfully controlled cancer — but only in 'immune hot' tumors already populated with active immune cells ready to fight.
- In tumors where the immune system was already dormant, the combination failed entirely, revealing that ongoing clinical trials may be testing this therapy on exactly the patients least likely to benefit.
- Researchers are now calling for smarter trial design — screening patients for 'immune hot' tumors before enrollment — while also investigating how to counter the resistance that will inevitably develop as these drugs see wider use.
Lung cancer kills roughly 1.8 million people every year, and only about one in four survives past five years. For decades, researchers have searched for treatments that might shift those numbers. Scientists at the Francis Crick Institute in London now believe they may have found a promising direction: pairing a drug that blocks a specific genetic mutation with immunotherapy, which enlists the body's own immune system to fight cancer.
The mutation in question is KRAS — a gene that normally governs whether cells grow or die. When it mutates, it runs unchecked, occurring in roughly one-third of all lung cancers and one-fifth of all cancers globally. The first drug designed to block mutated KRAS was approved in 2021, but approval is not the same as knowing how to use it best. Researcher Julian Downward and his team set out to test whether blocking KRAS worked better alongside immunotherapy in laboratory mice.
What they found was striking but conditional. In tumors they called 'immune hot' — packed with active immune cells primed to fight — the combination successfully controlled cancer. Blocking KRAS caused immune-suppressing cells in the tumor environment to decrease while cancer-killing T-cells increased. The immune system, no longer undermined, could do its job. But in tumors where the immune system was already struggling, the combination failed entirely.
This distinction carries serious implications for ongoing clinical trials. Most have enrolled patients who did not respond to immunotherapy alone — precisely the wrong population, the researchers argue, since those patients are unlikely to have 'immune hot' tumors. Co-author Miriam Molina Arcas noted that there is still much to learn about when KRAS inhibitors are most effective and how they can be safely combined with other treatments. Future trials, the team insists, must identify and recruit patients with 'immune hot' tumors before enrolling them. Researchers are also exploring how to address the resistance to these drugs that will inevitably emerge — one more piece of a much larger puzzle still being assembled.
Lung cancer kills roughly 1.8 million people every year. Of those diagnosed, only about one in four survives past five years. It remains the leading cause of cancer death worldwide. For decades, researchers have chased treatments that might shift those numbers. Now, scientists at the Francis Crick Institute in London believe they may have found a promising direction: pairing a drug that blocks a specific genetic mutation with immunotherapy, a treatment that enlists the body's own immune system to fight cancer.
The mutation in question is KRAS, a gene that normally helps control whether cells grow or die. When it mutates, it goes haywire—and this happens in roughly one-third of all lung cancers. The same gene is implicated in about one-fifth of all cancers globally, including melanoma, bowel cancer, and pancreatic cancer. In 2021, the first drug designed to block the mutated version of KRAS was approved for use in certain lung cancer patients. But approval of a drug is not the same as understanding how to use it best.
The real question researchers wanted to answer was whether blocking KRAS worked better when combined with immunotherapy—specifically, a type called immune checkpoint blockade. Immunotherapy has transformed cancer treatment for some patients, but most do not respond to it at all. The team, led by researcher Julian Downward, decided to test the combination in laboratory mice to see what would happen.
What they found was striking but conditional. In tumors they called "immune hot"—meaning tumors packed with active immune cells ready to fight—the combination successfully controlled cancer. The mutated KRAS gene, it turned out, was actively weakening the immune system's ability to respond while simultaneously creating an environment that helped the tumor survive. When the researchers blocked KRAS, those protective factors for the tumor disappeared. Immune-suppressing cells in the tumor environment decreased. Cytotoxic T-cells, the kind that kill cancer cells, increased. The immune system, no longer hamstrung, could do its job.
But there was a catch. In tumors that were not "immune hot"—where the immune system was already struggling to mount a response—the combination treatment failed. This distinction matters enormously for how future trials should be designed.
Several clinical trials are already underway, testing KRAS inhibitors combined with immune checkpoint blockade. But most of them have enrolled patients who did not respond to immunotherapy alone. That is precisely the wrong population, the researchers argue. If a patient's tumor did not respond to immunotherapy by itself, it is likely not an "immune hot" tumor and therefore unlikely to respond to the combination either. The trials, in other words, may be testing the therapy on people least likely to benefit from it.
Miriam Molina Arcas, a co-author of the study, emphasized that KRAS inhibitors are still new territory. "There's still a lot to learn about when they are most effective and which other treatments they can safely be combined with," she said. The implication is clear: future trials need to be smarter about patient selection. They need to identify and recruit people whose tumors are "immune hot" before enrolling them. That is where the combination is most likely to work. The researchers are also exploring how to help the immune system destroy cancer cells that develop resistance to RAS inhibitors—a problem that will inevitably arise as more patients receive these drugs. The study, published in Science Advances, is one piece of a much larger puzzle that oncologists are still assembling.
Citações Notáveis
There's still a lot to learn about when they are most effective and which other treatments they can safely be combined with to give patients the best chance of living longer.— Miriam Molina Arcas, co-author, Francis Crick Institute
As the mutation is present in about one-third of lung cancer cases, it is a promising therapeutic target.— Julian Downward, researcher, Francis Crick Institute
A Conversa do Hearth Outra perspectiva sobre a história
Why does it matter whether a tumor is "immune hot" or not?
Because the combination only works if the immune system is already primed to fight. If the immune cells are already dormant or suppressed, blocking KRAS alone won't wake them up. You need both conditions: a responsive immune system and the removal of the genetic brake that KRAS mutation creates.
So the trials happening now might be failing for the wrong reason?
Exactly. They're enrolling patients whose tumors didn't respond to immunotherapy in the first place. Those tumors are probably not "immune hot." So when the combination doesn't work, it's not because the combination is bad—it's because they're testing it on the wrong patients.
How do you identify an "immune hot" tumor before you treat someone?
That's the practical challenge the researchers are pointing to. You need better diagnostic tools to measure immune cell activity in a tumor before deciding on treatment. Right now, that's not standard practice.
What happens to patients whose tumors develop resistance to these KRAS inhibitors?
That's the next frontier. The researchers are already thinking about it. They're looking at ways to stimulate the immune system further, or perhaps combining KRAS inhibitors with other drugs. Resistance is inevitable; the question is how quickly it develops and what you do when it does.
Why is KRAS such an important target?
It's everywhere. One-third of lung cancers have it. One-fifth of all cancers have some RAS mutation. If you can crack the code on how to treat KRAS-mutant cancers effectively, you're potentially helping millions of people across multiple cancer types.