A Phase 2 Trial of Afatinib in Patients with Solid Tumors that Harbor Genomic Aberrations in the HER family: The MOBILITY3 Basket Study

Abstract

Background: Epidermal growth factor receptor (EGFR)- and human epidermal growth factor receptor (HER)2-targeted therapies are approved for the treatment of breast, gastric/gastrointestinal junction (GEJ), and non-small cell lung cancer (NSCLC) with specific molecular aberrations affecting HER family members. Over 10 % of other cancers harbor genomic aberrations affecting HER family members, but their role remains undefined.

Objective: The MOBILITY3 trial evaluated the antitumor activity of afatinib, an oral pan-HER tyrosine kinase inhibitor (TKI) in HER-aberrant tumors outside of the licensed indications.

Patients and methods: In this single-center basket trial, patients with advanced solid tumors that harbor mutations and/or amplifications of any of the HER family members (EGFR, ERBB2, ERBB3, ERBB4) were enrolled. The EGFR-mutated NSCLC and HER2-positive breast cancers were excluded. Participants were treated with oral afatinib 40 mg daily until disease progression or unacceptable toxicity. Objective response rate (ORR) and progression-free survival (PFS) were primary and secondary endpoints, respectively.

Results: The study enrolled 12 patients with 6 tumor types (NSCLC, sarcoma, salivary gland, gastric/GEJ, breast and pancreatic cancer). Objective response rate was 8 % (95 % CI 0.2-38%) and median PFS was 11.4 weeks (95% CI 4.6-33.3 weeks). All 3 patients with salivary gland cancers and 1 patient with ERBB2-mutant NSCLC had clinical benefit (stable disease or partial response lasting > 24 weeks). Due to slow accrual and a lower-than-expected response rate, trial recruitment was terminated before the target of 30 patients were enrolled.

Conclusions: In the MOBILITY3 study (NCT02506517), afatinib demonstrated modest activity in tumors that possess EGFR and ERBB2 aberrations. Clinical benefit seen in all 3 salivary gland cancers supports the growing evidence for the utility of HER-targeted therapies in the treatment of this specific tumor type.