DESTINY-Breast03 Phase 3 Study Results
Conclusions
Daiichi-Sankyo
HER3-DXd demonstrated clinically meaningful and durable antitumor activity in a heavily pretreated
population of patients with HER3-expressing BC
• Durable antitumor activity was demonstrated across BC subtypes: HR+/HER2- (ORR, 30%; median DOR, 7.2 months),
TNBC (ORR, 23%; median DOR, 5.9 months), and HER2+ (ORR, 43%; median DOR, 8.3 months)
• Antitumor activity was also demonstrated across the range of HER3 expression
• The safety profile was manageable with a low rate of discontinuation due to TEAES (10%)
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• The rate of adjudicated treatment-related ILD was 7%; most cases were grade 1 and 2
Grade ≥3 hematological toxicities were manageable; no grade ≥3 thrombocytopenia resulted in treatment discontinuation
nor in a grade ≥3 bleeding event
As a similar safety profile was seen with 4.8 mg/kg and 6.4 mg/kg, a 5.6 mg/kg dose, currently used
in NSCLC, is being evaluated in BC to refine dose optimization
These data provide encouraging evidence of antitumor efficacy with a manageable safety profile
and warrant further evaluation of HER3-DXd across clinical and histopathological BC subtypes
ASCO 2022 #1002 Oral
94
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