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

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.