A targeted drug shrank breast cancer brain tumors in mice
Original title: Preclinical modeling of trastuzumab deruxtecan in a mouse model of brain metastatic triple-negative breast cancer identifies two contributors to efficacy.
How far along is this research?
- Lab cells
- Animals
- Review
- Tested in people
This was done in animals, not people. Most findings at this stage never become treatments.
This was only done in mice and in lab tests.
The short version
In mice, a targeted drug lowered breast cancer tumors in the brain.
What was studied. Scientists gave mice a drug called trastuzumab deruxtecan, or T-DXd. The mice had triple-negative breast cancer that had spread to the brain. The drug was compared with a look-alike drug that cannot grab the HER2 target.
What they found. The higher dose cut brain tumors by 49% compared with the look-alike drug. The lower dose cut them by 30%, but that result was too small to count. Fewer tumor cells were growing, and 5 times more tumor cells died. When the team removed HER2 from the cancer cells, the drug stopped working in the mice.
What this means, and what it doesn't
What it could mean: The drug has already worked in people with advanced breast cancer that has low or very low HER2. This mouse work suggests it may still reach tumors in the brain, even when HER2 levels are very low. It also points to a second way the drug may get inside tumor cells.
What it doesn't mean: This does not mean the drug is proven for brain tumors in people. The work was done in mice and in lab tests, not in patients. It is early science about how the drug works, not a new treatment plan. It is not a cure, and it does not change the care your doctor offers today.
Source: PubMed, October 24, 2026 · Read the original
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