HER2 Drug Trio Extends Survival in Phase II Study of Breast Cancer Leptomeningeal Metastasis

Overview

• Published in Nature Cancer, the multicenter TBCRC049 Phase II trial treated 17 women with newly diagnosed HER2-positive leptomeningeal disease using tucatinib, trastuzumab and capecitabine.
• Median overall survival reached 10 months versus a 4.4-month historical benchmark, with 41% alive at 18 months and median time to central nervous system progression of about seven months.
• Clinical activity in the central nervous system included improved neurologic deficits in 7 of 12 evaluable patients and a 38% composite leptomeningeal objective response (5 of 13).
• Pharmacokinetic testing detected tucatinib and its metabolite in cerebrospinal fluid at levels comparable to plasma, supporting central nervous system penetration.
• Adverse events were largely manageable, though one patient discontinued for liver enzyme elevation, and interpretation is limited by the single-arm design and early closure from slow accrual after FDA approval.