Pertuzumab (P) with trastuzumab (T) and chemotherapy (CTX) in patients (pts) with HER2-positive metastatic gastric or gastroesophageal junction (GEJ) cancer: An international phase III study (JACOB).

Abstract

TPS4150 Background: Human epidermal growth factor receptor 2 (HER2) is overexpressed in ~20% of gastric cancers. Specific targeting of HER2 by T in combination with CTX has demonstrated significantly improved overall survival (OS) vs CTX in pts with advanced gastric or GEJ cancer (Bang Lancet 2010). In HER2-positive 1L metastatic breast cancer the combination of T plus docetaxel with a second HER2-targeted antibody, P, demonstrated significant improvement of progression-free survival (PFS) and OS vs placebo+T+docetaxel (Baselga NEJM 2012; Swain SABCS 2012). Based on these positive findings with HER2-targeted therapies in gastric and breast cancer, JACOB, a double-blind, placebo-controlled, randomized Phase III study, is designed to evaluate efficacy and safety of P+T+CTX in pts with HER2-positive 1L metastatic gastric or GEJ cancer. Methods: Pts will be randomized 1:1 to receive P+T+cisplatin+fluoropyrimidine or the same regimen replacing P with placebo, q3w (P: 840 mg; T: 8 mg/kg first dose, then 6 mg/kg; cisplatin: 80 mg/m2; 5-fluorouracil: 800 mg/m2/24 h given continuously for 120 h or capecitabine: 1000 mg/m2 bid for 14 days). P/placebo+T will be given until progressive disease (PD) or unacceptable toxicity. On or before Cycle 6, CTX should only be discontinued for PD or unacceptable toxicity. Continuation of CTX after Cycle 6 is at the discretion of pt and physician. Randomization will be stratified by region (Japan vs North America/Western Europe/Australia vs Asia [excluding Japan] vs South America/Eastern Europe), prior gastrectomy, and HER2-positivity (IHC 3+ vs IHC 2+ and ISH+). Primary endpoint: OS; secondary endpoints include PFS, objective response rate, duration of response, clinical benefit rate, safety, pharmacokinetics of P, and patient-reported outcomes. Tumor and blood samples for biomarker evaluation will be collected. The study is estimated to have 80% power to detect a significant improvement in OS at a two-sided α-level of 5% (HR=0.777), with ~502 deaths required for the primary analysis. Target enrollment is 780 pts from ~200 sites and 35 countries; FPI is planned for April 2013. NCT01774786 Clinical trial information: NCT01774786.