Science1 publisher2 min readPublished
Blocking MEK let exhausted T cells spend energy more slowly and persist near tumors in lab models
Memorial Sloan Kettering scientists found that blocking MEK let exhausted cancer-fighting T cells conserve energy and persist near tumors in animal studies. Because MEK inhibitors are already FDA-approved, the lab says the approach could be tested in people soon.
The Scientist · Science desk
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What happened
- Sustained MEK activity pushes a T cell into terminal exhaustion, a severely depleted state in which immunotherapy can no longer reactivate it.
- The work extends the same lab's 2020 finding that a T cell's metabolism, the way it turns nutrients into energy, is central to how it becomes exhausted.
- Exhaustion has mattered most for checkpoint inhibitors, the drugs designed to remove the biological restraints that normally limit T cell activity.
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Why it matters
- capability If the finding holds, the drug target becomes a T cell's workload: lowering the demand to make cytotoxic proteins so cells can renew themselves.
- decision Because MEK inhibitors are already FDA-approved for other uses, testing a combination with immunotherapy would reuse an existing drug and could reach patients faster.
- constraint The work is preclinical, so it cannot yet say whether pacing a T cell extends a patient's response or slows an actual tumor.
If exhaustion meant a cell running low on energy, the fix would be to feed it more [1]. Near a tumor, though, these exhausted T cells stayed highly active rather than sluggish [13], and once the researchers added MEK inhibitors the cells divided more while using less energy [14]. Continuous exposure to tumor antigens overburdens the cell's mitochondria [9], and MEK is the signal that sets how many cancer-killing proteins the cell makes [10]. Keep MEK turned up and the cell is driven into terminal exhaustion, the state in which immunotherapy can no longer reactivate it [11].
Tanmana Mitra, the study's first author, said T cell exhaustion is not simply a loss of function. She said it comes from a mismatch between the work the cells are asked to do and the energy they can supply [12][19]. The lab's 2020 work had put metabolism at the center of exhaustion [8]. This paper says where the energy goes. The shift, in Mitra's words, is "from a problem of too little energy to one of excessive energy demand" [15].
Santosha Vardhana, who treats lymphoma at Memorial Sloan Kettering, has watched the clinical version [3]. "A tragic part of T cell exhaustion is that the immunotherapy seems to be working for patients, and then it fades," he said [4]. The lab argues that blocking MEK might slow exhaustion and make immunotherapy more effective [6], and the reason it could move quickly is practical: "FDA-approved MEK inhibitors are already available, so this approach could be tested in humans without much delay," Vardhana said [7]. Exhaustion has mattered most for checkpoint inhibitors, which work by stripping the brakes off T cells [2].
The results come from animal studies and laboratory models [5][18]. The release does not say how much longer the cells lasted or how far tumor growth was held back. Lowering MEK also lowers the cytotoxic output the lab wants from these cells, even as it lets some of them stay active and renew for longer [16], so a trial has to show whether pacing a T cell trades near-term killing power for persistence. The team's own picture is a long road trip: ease off the throttle to keep fuel in the tank [17].
What to watch
- Whether a human trial pairing a MEK inhibitor with a checkpoint inhibitor gets registered or started.
- Whether lowering MEK, which also cuts cytotoxic output, weakens tumor killing in the near term even as persistence improves.
- The quantitative survival and energy-use numbers in the full Immunity paper, beyond the press release.