DESTINY-Breast03 Phase 3 Study Results
Baseline Characteristics
Median age (range), years
Country, %
ECOG PS, %
Japan
HR+/HER2-
(n=113)
HER3-High and -Low
55.0 (30-83)
TNBC
(n=53)
HER3-High
a
59.0 (30-81)
HER2+
(n=14)
HER3-High
58.0 (37-70)
70.8
86.8
100.0
USA
29.2
13.2
0.0
0
75.4
62.3
85.7
1
24.6
37.7
14.3
HER2 zero
34.5
35.8
0.0
HER2 Low
51.3
54.7
0.0
HER2 status, %b
HER2 High
0.0
0.0
100.0
HER2+ ISH Unknown
11.5
9.4
0.0
Unknown
2.7
0.0
0.0
Lung and/or Liver
90.3
64.2
85.7
Lung
43.4
47.2
42.9
Presence of metastasis (BICR), %
Liver
75.2
34.0
57.1
Brain
10.6
9.4
28.6
Bone
60.2
35.8
50.0
Median sum of diameters (BICR; range), mm
54.0 (10, 182)
44.4 (11, 186)
44.6 (17, 85)
All regimens
7.0 (2-14)
3.0 (1-13)
6.5 (2-11)
Median number of prior cancer regimens
(range), n
In advanced setting
6.0 (2-13)
CT in advanced setting
3.0 (1-7)
2.0 (1-13)
2.0 (1-6)
5.5 (2-11)
4.0 (2-8)
Patients with HER3-expressing metastatic BC with poor prognostic characteristics were heavily pretreated
ASCO-CAP, American Society of Clinical Oncology-College of American Pathologists; BICR, blinded independent central review; CT, chemotherapy; DE/DF, dose escalation/dose finding; ECOG PS, Eastern Cooperative Oncology Group
performance status; ISH, in situ hybridization.
a HER3-high was defined as >75% membrane positivity at 10x; HER3-low was defined as ≥25% and ≤75% membrane positivity at 10x. In DE/DF cohorts, IHC 2+ and 3+ were considered HER3-high. b HER2 status definitions: HER2 zero,
IHC 0; HER2 low, IHC 1+ or 2+ (ISH-); HER2 high, IHC 2+ (ISH+), IHC 3+. Patients with clinically active brain metastases were excluded.
ASCO 2022 #1002 Oral
Daiichi-Sankyo
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