Tucatinib, a new targeted therapy, delays disease progression and improves survival in people with previously treated HER2-positive metastatic breast cancer, including those whose cancer has spread to the brain, researchers reported at the San Antonio Breast Cancer Symposium in December.

The Phase II HER2CLIMB study tested the experimental kinase inhibitor in 612 participants. Nearly half had brain metastasis—a group often excluded from clinical trials.

After a year, the risk of disease progression or death was 46% lower for participants randomly assigned to tucatinib plus Herceptin (trastuzumab) and chemotherapy compared with those who received a placebo regimen. Among patients with brain metastasis, everyone in the placebo group worsened, but a quarter of those in the tucatinib group saw no disease progression. Overall survival at one year was 76% in the tucatinib group versus 62% in the placebo group; at two years, the corresponding figures were 45% and 27%.

“These results are unprecedented for late-line therapy in advanced breast cancer and are a major advance for patients who have significant unmet medical need,” says the study’s lead investigator, Rashmi Murthy, MD, of the University of Texas MD Anderson Cancer Center.