DESTINY-Breast03 Phase 3 Study Results

Most Reported Adverse Events (≥15% all grades) Preferred term, n (%) AEs all causes Dato-DXd + D N=29 All Grades, Grade Grade Grade ≥15% of patients 1 2 3 Stomatitis 20 (69) 8 (28) 8 (28) 4 (14) 13 Alopecia 19 (66) 6 (21) 0 (45) 13 Nausea 19 (66) 6 (21) (45) Constipation 11 (38) 8 (28) 3 (10) Fatigue 11 (38) 9 (31) 2 (6.9) Rash 9 (31) 8 (28) 1 (3) 0 Vomiting 5 (17) 3 (10) 2 (6.9) 0 Data cutoff: November 15, 2021 0 O O O 0 0 ◆ Low rates of diarrhea reported (4 [14%]; all Grade 1) Daiichi-Sankyo ◆ No cases of ILD/pneumonitis or neutropenic events were reported ◆ 13.7% of patients required dose reduction due to stomatitis ◆ Updated TMGs and prophylaxis for stomatitis are being implemented ILD, interstitial lung disease; TMG, trial management guide. ESMO BC 2022 #166 Mini Oral 80 60

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