Patient Characteristics
Of 63 patients with metastatic breast cancer were enrolled in this study, 62 patients received study drug and were included in the analysis. The primary cohort included 41 patients unselected for BRCA1/2 mutations or breast cancer subtype, and the expansion cohort included 21 patients who all had BRCA1/2 deleterious mutations.
Table 1 shows the baseline characteristics of patients in these two cohorts. Most patients had an ECOG score of less than 2 and one patient in the primary cohort was male. The primary cohort included TNBC (54%), HR+ (37 %), and HER2+ (10%) patients, while the expansion cohort included predominantly HR + patients (57%). Nine of 41 (22%) patients in the initial cohort had BRCA1/2 mutations compared to all subjects in the expansion cohort. The most common metastatic sites were lymph nodes in the primary cohort and bone lesions in the expansion cohort. The median number of prior chemotherapeutic, hormonal, or HER2 directed regimens was 3 (range, 1–9) in the primary cohort and 2 (range, 0–9) in the expansion cohort. A total of 14 patients (34%) in the primary cohort and eight patients (38%) in the expansion cohort had received prior platinum therapy for metastatic disease.
Table 1
Characteristics | Primary Cohort (n = 41) | Expansion Cohort (n = 21) | Total (n = 62) |
Median age, yr (range) | 50 (31–68) | 46 (29–81) | 48 (29–81) |
Female sex, no. (%) | 40 (98) | 21 (100) | 61 (98) |
ECOG Performance Status, no. (%) | | | |
0 | 21 (51) | 11 (52) | 32 (52) |
1 | 17 (42) | 9 (43) | 26 (42) |
2 | 3 (7) | 0 (0) | 3 (5) |
Subtypes, no. (%) | | | |
TNBC | 22 (54) | 8 (38) | 30 (48) |
HR + HER2- | 15 (37) | 12 (57) | 27 (44) |
HER2+ | 4 (10) | 1 (5) | 5 (8) |
BRCA mutation status, no. (%) | | | |
BRCA1 | 3 (7) | 9 (43) | 12 (19) |
BRCA2 | 6 (15) | 12 (57) | 18 (29) |
Sites of disease, no. (%) | | | |
Bone | 26 (63) | 15 (71) | 41 (66) |
Lung | 23 (56) | 10 (48) | 33 (53) |
Liver | 20 (49) | 12 (57) | 32 (52) |
CNS | 7 (17) | 6 (29) | 13 (21) |
Lymph nodes | 29 (71) | 9 (43) | 38 (61) |
Prior lines therapies for metastatic diseases, median (range) | 3 (1–9) | 2 (0–9) | 3 (0–9) |
Prior platinum treatment, no. (%) | 14 (34) | 8 (38) | 22 (36) |
Response to Treatment
Of 62 patients who received treatment, 10 patients had no follow-up imaging due to rapid clinical progression (7 in the primary cohort and 2 in the expansion cohort) or early death (one subject in the expansion cohort). Thirty-four patients in the primary cohort and 18 patients in the expansion cohort were evaluable for response (Table 2).
Table 2
Best objective response to treatment a
Response, n (%) | Primary Cohort (n = 41) | Expansion Cohort (n = 21) | Total (n = 62) |
CR | 1 (2) | 0 | 1 (2) |
PR | 3 (7) | 3 (14) | 6 (8) |
SD | 13 (32) | 10 (48) | 23 (37) |
PD | 17 (41) | 5 (24) | 22 (35) |
NE | 7 (17)b | 3 (14)c | 10 (16) |
ORR | 4 (9) | 3 (14) | 7 (11) |
CBR at 4 mo | 11 (27) | 9 (43) | 20 (32) |
a This table shows the number of patients with each response (%) in the primary cohort, the expansion cohort and the total study population; the denominators used in all calculations consisted of the total numbers of patients in each group; The subgroup analyses by status of BRCA1/2 mutation and the prior platinum treatment are presented in Table 3; |
b 7 patients had no follow-up imaging due to rapid clinical progression; one of these patients had a BRCA2 mutation; |
c Patients had no follow-up imaging due to rapid clinical progression (n = 2) or early death (n = 1); |
Abbreviations: CR, Complete response; PR, Partial response; SD, Stable disease; PD, Progressive disease; NE, Non-evaluable; ORR, objective response rate; CBR at 4 mo, Clinical benefit rate at 4 months |
In the combined overall population of 62 patients, the ORR (CR + PR) was 12% (7/62) and the CBR at 4 months was 32% (20/62); the primary cohort had a 10% (4/41) ORR and 27% (11/41) CBR at 4 months, while the BRCA1/2 expansion cohort had a 14% (3/21) ORR and 43% (9/21) CBR at 4 months. The waterfall plots demonstrated the best overall response of evaluable patients in each cohort (Supplemental Fig. 1). In the primary cohort (n = 34 evaluable, Supplemental Fig. 1A), all four patients who achieved CR or PR had BRCA1/2 mutations. Thirteen patients in this cohort, including one who had an unconfirmed partial response, demonstrated stable disease according to RECIST 1.1 criteria. Seventeen patients had PD, including eight with stable target lesions but with non-target progression or new lesions elsewhere. In the BRCA1/2-positive expansion cohort (n = 18 evaluable, Supplemental Fig. 1B), three patients achieved PR, an additional 10 patients had SD, and five patients had PD, including one patient who achieved SD in target lesions but had new lesions. Combining both cohorts, all seven patients who had achieved a response (CR or PR) were BRCA1/2 carriers, including five patients with BRCA2 mutations and two patients with BRCA1 mutations (Fig. 1). There were no responses in patients without BRCA1/2 mutations (Figs. 1 and 2).
In an exploratory subgroup analysis stratified by prior platinum treatment (Table 3), the ORR was 15% (6/40) among platinum-naïve patients versus 5% (1/22) among platinum-exposed patients. The CBR at 4 months was 38% (15/40) in the platinum-naïve group compared to 23% (5/22) in the platinum-exposed group.
Table 3
Subgroup responses to treatment by BRCA1/2 mutation status and prior platinum treatment
Response n (%) | BRCA1/2 mutation | Prior platinum treatment | BRCA mutation | No BRCA mutation |
| Yes (n = 30) | No (n = 32) | Yes (n = 22) | No (n = 40) | Prior platinum Tx (Yes, n = 11) | Prior platinum Tx (No, n = 19) | Prior platinum Tx (Yes, n = 11) | Prior platinum Tx (No, n = 21) |
CR | 1 (3) | 0 | 0 | 1 (3) | 0 | 1 (5) | 0 | 0 |
PR | 6 (20) | 0 | 1(5) | 5 (13) | 1 (9) | 5 (26) | 0 | 0 |
SD | 12 (40) | 11 (34) | 5 (23) | 18 (45) | 3 (27) | 9 (47) | 2 (18) | 9 (43) |
PD | 7 (23) | 15 (47) | 11 (50) | 11 (28) | 4 (36) | 3 (16) | 7 (64) | 8 (38) |
NE | 4 (13) | 6 (19) | 5 (23) | 5 (13) | 3(27) | 1 (5) | 2 (18) | 4 (19) |
ORR | 7 (23) | 0 | 1 (5) | 6 (15) | 1 (9) | 6 (32)* | 0 | 0 |
CBR at 4 mo | 14 (47) | 6 (19) | 5 (23) | 15 (38) | 3(27) | 11 (58)* | 2 (18) | 4 (19) |
* P < 0.01 comparing this group to all other groups by the Fisher’s Exact test |
Abbreviations: CR, Complete response; PR, Partial response; SD, Stable disease; PD, Progressive disease; NE, Non-evaluable; ORR, objective response rate; CBR at 4 mo, Clinical benefit rate at 4 months |
In the subgroup analysis based on BRCA1/2 mutation status (Table 3 and Fig. 1), the ORR was 23% (7/30) among BRCA1/2 carriers compared to 0% (0/32) among non-carriers. Of these seven patients, six had no previous platinum treatment (Fig. 2) and one had prior platinum exposure but did not have documented progression on platinum therapy. The CBR at 4 months was 47% (14/30) for BRCA1/2 carriers versus 19% (6/32) for non-carriers. Furthermore, platinum-naïve patients with BRCA1/2 mutations had an ORR of 32% (6/19) and a 4-month CBR of 58% (11/19), while platinum-exposed patients with BRCA1/2 mutations had an ORR of 9% (1/11) and a 4-month CBR of 27% (3/11; Table 3 and Fig. 2).
Comparing the different subtypes of metastatic breast cancer (Supplemental Table 1), the ORRs were 19% (5/27), 17% (1/6), and 3% (1/29) for HR+, HER2 + and TNBC, respectively, while the 4-month CBR rates were 41% (11/27), 50% (3/6), and 21% (6/29) for HR+, HER2 + and TNBC, respectively.
Survival analysis
The median PFS was 2.1 months (90% CI, 1.8 to 3.0 mo) in the overall population (Fig. 3A), and 1.8 months and 3 months in the primary and expansion cohorts, respectively (Supplemental Fig. 2). The median PFS among BRCA1/2 carriers was 3.3 months (90% CI, 2.3 to 6.2 mo) compared to 1.8 months (90% CI, 1.6 to 2.3 mo) among non-carriers (HR: 0.48, p = 0.006; Fig. 3B). Among patients who had not received prior platinum therapy, the median PFS was 2.7 months (90% CI, 1.9 to 4.0 mo) compared to 1.9 months (90% CI, 1.3 to 2.3 mo) among patients who had received prior platinum therapy (HR: 0.45, p = 0.005; Fig. 3C). Patients who were BRCA1/2 carriers without prior platinum therapy had a significantly prolonged progression-free survival (mPFS 6.2 mo; 90% CI, 3.7 to 7.3 mo) compared to other groups (HR: 0.34, p = 0.0003; Fig. 3D). One patient, a BRCA2 carrier who had no prior platinum therapy, had a durable complete remission for at least 5 years as of last contact. No significant difference in PFS was observed by breast cancer subtype (Supplemental Fig. 3).
Safety
All 62 patients who received at least one dose of veliparib and TMZ were considered for safety evaluation. Patients had a median treatment duration of 9 weeks (range 0.1 to 85 weeks), with a median daily dose of 60 mg (range, 40 to 80mg) for veliparib and 200 mg (range, 75 to 480 mg) for TMZ. A total of 27 and 26 patients had a dose delay on veliparib and TMZ respectively; 29 patients (47%) had a dose modification on TMZ.
Of the 62 patients, one patient received only one dose of veliparib and TMZ and experienced no treatment-related adverse events. The most common all-grade AEs were thrombocytopenia, nausea, fatigue, anemia, and leukocytosis (Table 4), and the most frequent grade 3 or higher AEs were thrombocytopenia, neutropenia, leukocytosis, nausea, and vomiting. The most common AEs that caused dose delays or modifications were thrombocytopenia and neutropenia. One patient discontinued study treatment due to prolonged thrombocytopenia. Another patient died of sepsis after receiving 4 cycles of treatment.
Table 4
Treatment-related adverse events
Event | All Grade | Grade3 | Grade 4 | Grade 5 |
n (%) (Total n = 62) |
Thrombocytopenia | 51 (82) | 20 (32) | 11 (18) | |
Nausea | 45 (73) | 6 (10) | | |
Fatigue | 37 (60) | 4 (6) | | |
Anemia | 36 (58) | 4 (6) | 1 (2) | |
Leukocytosis | 33 (53) | 10 (16) | | |
Neutropenia | 32 (52) | 13 (21) | 4 (6) | |
Vomiting | 21 (34) | 5 (8) | | |
Lymphopenia | 19 (31) | 4 (6) | | |
Anorexia | 13 (21) | 1 (2) | | |
ALT, SGPT | 12 (19) | 0 | | |
Alkaline phosphatase | 10 (16) | 0 | | |
Headache | 10 (16) | 2 (3) | | |
Constipation | 9 (15) | 0 | | |
Diarrhea | 9 (15) | 1 (2) | | |
Hypokalemia | 9 (15) | 1 (2) | | |
AST, SGOT | 8 (13) | 0 | | |
Hyperglycemia | 7 (11) | 0 | | |
Febrile neutropenia | 3 (5) | 2 (3) | 1 (2) | |
Dyspnea | 3 (5) | 1 (2) | 1 (2) | |
Anxiety | 2 (3) | 1 (2) | | |
Allergic reaction | 1 (2) | 1 (2) | | |
Infection, lung | 1 (2) | 1 (2) | | 1 (2) |
Hypoxia | 1 (2) | 1 (2) | 1 (2) | |