For some cancer patients, immune checkpoint inhibitors (ICIs) have significantly improved survival rates. These treatments, which include well-known drugs such as Keytruda and Opdivo, work by helping the immune system recognize and attack cancer cells. However, a small percentage of patients—about 2%—experience a severe side effect: the immune system attacks heart tissue, leading to myocarditis. This condition can be fatal in about half of those affected.
Researchers at Cincinnati Children's have identified a potential method to reduce this risk. Their findings were published on February 20, 2026, in the Journal of Experimental Medicine. The study was led by Kathrynne Warrick, an MD-PhD student, with Hyeon Sook Pasare and Jeffery Molkentin serving as co-corresponding authors.
Since the approval of Yervoy in 2011 for metastatic melanoma treatment in the United States, ICIs have changed outcomes for many types of cancer. The importance of this therapy was recognized when James Allison and Tasuku Honjo received the Nobel Prize in Medicine in 2018 for their work on immune checkpoint inhibition.
To better understand why ICIs sometimes cause myocarditis, the Cincinnati Children’s team developed a mouse model that closely mirrors how this complication occurs in humans. Through their experiments, they discovered that CD8 T cell–derived tumor necrosis factor (TNF) is a key driver behind ICI-induced myocarditis.
The researchers also found that the problem arises not from existing cancer-specific T cells becoming exhausted but from new "autoreactive" T cells being produced. These T cells target healthy heart muscle cells as well as cancer cells.
Further tests showed that blocking TNF signaling through the TNFR2 gene product could prevent inflammation from starting in heart tissue—at least in mice.
"Checkpoint inhibitors allow TNF signaling to trigger CD8 T-cells that are specific to antigens on cardiac myocytes, which in turn leads to life-threatening arrythmias," Molkentin says. "We used a targeted TNF blockade method to prevent this cycle in our mouse models. If these results can be replicated in humans, TNF blockade should prevent cardiac toxicity without compromising the anti-tumor benefits of ICIs."
The team notes that more research is necessary before applying these findings to people. They need to determine whether a focused TNF inhibitor would be safe for human use and how long it would need to be administered. Antibodies targeting TNFR2 are still under development. Researchers also want to see if similar strategies could help prevent other immune-related side effects caused by ICIs.
