LUX-breast 2: Phase II, open-label study of oral afatinib in HER2-overexpressing metastatic breast cancer (MBC) patients (pts) who progressed on prior trastuzumab (T) and/or lapatinib (L)

Abstract

BACKGROUND: Management of HER2-overexpressing MBC has improved over the past decade. However, pts still develop resistance to currently available HER2-targeted therapies and novel effective treatments are increasingly required as dual targeted combinations are given in early treatment lines already. Current therapies focus on targeting HER2 and do not inhibit all relevant ErbB Family dimers. Afatinib is an oral, irreversible ErbB Family Blocker that inhibits signaling through activated EGFR (ErbB1), HER2 (ErbB2) and ErbB4 receptors and transphosphorylation of ErbB3. Preclinical studies have demonstrated efficacy in T-sensitive and T-resistant human BC xenograft models dependent on ErbB signaling. Efficacy of afatinib in a T-resistant SUM 190 xenograft model has been shown to be increased by addition of IV vinorelbine (V). Afatinib monotherapy has shown promising clinical benefit in 46% of HER2-overexpressing MBC pts who progressed on prior T, with 10% of pts achieving PR. METHODS: This open-label Phase II trial (NCT01271725) investigates efficacy and safety of afatinib alone (40 mg/d) followed by afatinib ‘beyond progression’ plus chemotherapy in 120 pts with HER2-overexpressing MBC, who progressed on prior neoadjuvant and/or adjuvant T and/or L. Pts who progress on afatinib monotherapy receive afatinib plus either weekly paclitaxel (P) 80 mg/m2 or V 25 mg/m2. Eligible pts have confirmed HER2-overexpressing BC, stage IV disease measurable by RECIST 1.1, progressed on T and/or L therapy in either neoadjuvant and/or adjuvant setting, are eligible for retreatment with P or V and should not have been pretreated with P (≤12 months) or V, respectively. Exclusion criteria: inadequate cardiac, renal, hepatic and hematological function, pre-existing gastrointestinal dysfunction, rapidly progressing visceral disease, ILD and active brain metastases. The primary endpoint is objective response (OR) and secondary endpoints include best overall response, duration of OR and PFS; safety will be assessed separately for afatinib mono- and combination therapy. Patient enrollment began in May 2011 in 35 sites and 5 countries.