OA 14.05 Phase 2 Basket Trial of Ado-Trastuzumab Emtansine in Patients with HER2 Mutant or Amplified Lung Cancers

Abstract

Human epidermal growth factor receptor 2 (HER2, ERBB2) mutation and amplification each occurs in 2% of lung cancers, resulting in receptor dimerization and oncogenic signaling with in vitro sensitivity to trastuzumab. Ado-trastuzumab emtansine is a HER2 targeted antibody drug conjugate linking trastuzumab with the anti-microtubule agent emtansine. Patients with advanced HER2 mutant or amplified lung cancers were enrolled into separate cohorts in a basket trial of ado-trastuzumab emtansine, treated at 3.6mg/kg IV every 3 weeks. The primary endpoint was overall response rate (ORR) using RECIST v1.1. A separate cohort included patients with HER2 mutant lung cancers assessed using PERCIST, with pre-treatment 89Zr-trastuzumab PET as correlative imaging. A Simon two stage optimal design was used with type I error rate under 2.7% (and a family wise error rate across baskets under 10%), power of 89%, H0 10%, H1 40%. Other endpoints include progression-free survival (PFS) and toxicity. HER2 testing was performed on tumor tissue by next generation sequencing (NGS), fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC). A total of 33 patients were identified by NGS and enrolled. The first HER2 mutant cohort completed accrual of 18 patients with ORR of 44% (8/18 confirmed, 95% CI 22-69%), rejecting null hypothesis. The median PFS was 4 months, and median PFS for responders was 6 months (range 4-11 months). The PERCIST measured HER2 mutant cohort accrued 9 patients, there were 2 confirmed partial responses (PR) in 5 patients evaluated. The HER2 amplified cohort accrued 6 patients, with 3 confirmed PR observed including 1 with concurrent EGFR sensitizing mutation and resistance to erlotinib. Toxicities included grade 1 or 2 including infusion reaction, thrombocytopenia and transaminitis, there were no treatment related deaths. Of the 27 patients in the HER2 mutant cohorts, there were 18 (67%) exon 20 insertions and 9 (33%) point mutations; responders were seen across mutation subtypes (A775_G776insYVMA, G776delinsVC, V659E, S310F, L755P). Concurrent HER2 amplification was observed in 4 of 27 patients by either NGS or FISH. IHC ranged from 0 to 3+ and did not predict response. Of the 6 patients in the HER2 amplified cohort, 2 had concurrent HER2 mutation and 1 had concurrent EGFR L858R mutation. Ado-trastuzumab emtansine is active and well tolerated in patients with advanced HER2 mutant or amplified lung cancers as identified by NGS. While cohort expansion is ongoing, this study has met its primary endpoint in patients with HER2 activating mutations. Further development is warranted.