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In March, AstraZeneca signed a deal with Japanese drug maker Daiichi Sankyo that would pay up to $6.9 billion — $1.35 billion up front and $5.55 billion if sales and regulatory targets are hit — for a single experimental cancer drug. On Wednesday, data from that drug are being presented at the San Antonio Breast Cancer Symposium and published in the New England Journal of Medicine.

The new drug, trastuzumab deruxtecan, was tested in a clinical trial of 184 breast cancer patients whose tumors tested positive for a marker called HER2 and who had previously received cancer treatments including Roche’s Kadcyla. There was a response, meaning tumors shrank by at least 30%, in 112 patients, or 60.9% of those tested. Those responses lasted for a median of 14.8 months.


Though the trial is small and lacks a control group, those results are striking. In the clinical trials in which Kadcyla was approved, the drug shrank tumors by 30% or more in 44% of patients, and those responses lasted a median of 13 months. (That said, directly comparing trials is fraught with risks and can be misleading.)

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