CINCINNATI — A new study reveals a potential fix for one of the deadliest side effects of immune checkpoint inhibitors, drugs that have reshaped cancer care since 2011. These medications, including blockbuster names like Keytruda and Opdivo, unleash the immune system on tumors. But in roughly 2% of patients, they trigger myocarditis, an inflammation of the heart muscle that kills about half of those affected.

Scientists at Cincinnati Children’s report they engineered a mouse model mimicking this exact complication. Their experiments zeroed in on CD8 T cells producing tumor necrosis factor, or TNF, as the main culprit. Those T cells turn autoreactive, attacking healthy heart cells alongside cancer ones.

Blocking TNF signaling through the TNFR2 receptor halted the heart damage entirely in the mice. The anti-tumor effects stayed intact. Details appear in the Journal of Experimental Medicine on Feb. 20, 2026.

“This study makes a very important discovery that shows how to uncouple anti-tumor efficacy from cardiac toxicity,” said Chandrashekhar Pasare, DVM, PhD, director of the Division of Immunology at Cincinnati Children’s. Pasare co-led the work with Jeffery Molkentin, PhD, director of the Division of Molecular Cardiovascular Biology. MD-PhD student Kathrynne Warrick served as first author.

Immune checkpoint inhibitors work by disabling proteins that let tumors evade T cells. The first one, Yervoy, won U.S. approval for metastatic melanoma that year. Its pioneers, James Allison and Tasuku Honjo, claimed the 2018 Nobel Prize in Medicine for the breakthrough.

ICI-related myocarditis strikes fast, often causing fatal arrhythmias. The Cincinnati team showed it stems from TNF-driven T cells targeting cardiac antigens, not from tumors wearing out anti-cancer immunity. They tested TNFR2-specific blockade, a precise intervention now in early antibody development.

“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 arrhythmias,” Molkentin said. “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 findings could extend beyond hearts. Researchers plan to test if similar TNF tactics shield other organs from ICI side effects, which hit lungs, skin and intestines too. Human trials hinge on proving safety for focused TNF inhibitors and nailing optimal dosing duration.

Cancer patients now live longer thanks to ICIs. Drugs like Keytruda, from Merck, and Opdivo, from Bristol Myers Squibb, rack up billions in sales yearly. Yet the heart risk has shadowed their success. This mouse data offers a first clear path around it.

Pasare’s team published under the title “Immune checkpoint inhibitor-induced myocarditis is dependent on CD8 T cell-derived TNF and TNFR2 signaling.” The DOI is 10.1084/jem.20251717.