DESTINY-Breast03 Phase 3 Study Results

HER3 Membrane Expression Over Time HR+/HER2- cohort n=85 TNBC cohort n=31 PR SD PD NE PR SD PD NE 100- 100- HER3 membrane positivity, %b 25 25. 50 75 75 0 Archival Pre-treatment Visit HER3 membrane positivity, %b 50 25- 75- 0- Archival Pre-treatment Visit HER3 membrane expression changed dynamically, but this was not associated with clinical activity EOT, end of treatment. a On-treatment biopsy taken at cycle 2 day 3 or cycle 3 day 3. b Percent HER3 membrane positivity was centrally assessed by HER3 IHC. ASCO 2022 #1002 Oral 91 Daiichi-Sankyo

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