DESTINY-Breast03 Phase 3 Study Results

Baseline HER3 Membrane Expression by BOR HR+/HER2- cohorta n=74 (blue lines represent the mean) 100- HER3 membrane positivity, %b 75- 50 25 25 0 PR n=20 SD n=38 PD n=10 NE n=6 BOR TNBC cohorta n=26 (blue lines represent the mean) 100- HER3 membrane positivity, %b 75. 50 50 25 PR n=3 SD n=18 PD n=3 NE n=2 BOR Antitumor responses across a broad range of baseline HER3 membrane expression BOR, best overall response. a Pre-treatment HER3 positivity from patients in the dose expansion cohorts. b Percent HER3 membrane positivity was centrally assessed by HER3 IHC. ASCO 2022 #1002 Oral Daiichi-Sankyo 90 90

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