611 Background: Dual blockade of ErbB receptors combined with chemotherapy compared with single-agent blockade improves efficacy in HER2-positive disease. FB-8 is single arm, Phase I dose-escalation study to determine safety and tolerability of weekly paclitaxel (P), the irreversible tyrosine kinase inhibitor, neratinib (N) and trastuzumab (T) in women with metastatic, HER2-positive breast cancer (MBC). Methods: Women with measurable or non-measurable MBC (ECOG PS 0 - 2) received P (80 mg/m2 IV days 1, 8, 15 of 28-day cycle), T (4 mg/kg IV, then 2 mg/kg IV weekly), and N (oral, daily). N was dose-escalated using 3+3 design at 120 mg, 160 mg, and 240 mg, dose-limiting toxicity (DLT) determined in cycle 1. All patients (pts) received prophylactic anti-diarrheals. Results: All pts were taxane and trastuzumab pre-treated, with mean of 4 prior regimens. At N=120 mg, there was 1 DLT, grade (gr) 3 diarrhea with dehydration. Three more pts were enrolled; none experienced DLT. At N=160 mg, there were no DLTs. At N=240 mg, 2 of 3 pts had DLTs: one gr 3 diarrhea and dehydration, one gr 3 diarrhea, dehydration, and gr 3 mucositis. After de-escalation to N=160 mg, 3 more pts were added. If N=160 mg is well tolerated, a 200 mg cohort is planned. 12 pts completed cycle 1. Efficacy data are available on 10: CR 1, PR 3, SD 1 (8+months). One pt* had resolution of non-target disease (skin and breast mass). 4 pts were off-study before the first scan (DLT 3 and progressive disease 1) and are considered non-responders (NR). The most frequent grade 3-4 adverse event was diarrhea, 3 pts. Conclusions: Dual anti-HER blockade with N, T combined with P is tolerable and highly active in pts pre-treated with anti-HER2 agents and chemotherapy. This combination will be studied in a phase II neoadjuvant breast cancer trial (NSABP FB-7). We thank Pfizer, Inc and Puma Biotechnology, Inc for their support. [Table: see text]
Phase I dose-escalation trial of tucatinib in combination with trastuzumab in patients with HER2-positive breast cancer brain metastases
