Phase 2 trial of afatinib, an ErbB family blocker, in solid tumors genetically screened for target activation

The efficacy of afatinib, an irreversible ErbB Family Blocker, was evaluated in patients who had 1 of 4 categories of solid tumors with epidermal growth factor receptor/human epidermal growth factor receptor 2 (EGFR/HER2) gene amplification or EGFR-activating mutations.

Patients with previously treated but ErbB inhibitor-naive esophagogastric, biliary tract, urothelial tract, or gynecologic cancers (lung cancers were excluded) harboring EGFR/HER2 gene amplification or high polysomy were identified by fluorescence in situ hybridization (FISH). Tumors were also screened for EGFR mutations. The primary endpoint was the objective response rate; secondary endpoints included the clinical benefit rate, pharmacokinetics, and safety.

Of 385 prescreened patients, 38 had FISH-positive tumors (10 with EGFR amplification and 29 with HER2 amplification or high polysomy [1 tumor had EGFR/HER2 high polysomy]; none had EGFR-activating mutations), and 20 patients received treatment with afatinib 50 mg daily. The objective response rate was 5% (1 of 20 patients), and the best objective response included 1 complete response. Eight patients experienced stable disease. The most frequently reported adverse events were diarrhea, rash, and decreased appetite. The trial closed early because of slow recruitment.

Single-agent afatinib activity was limited, yet encouraging, in selected tumors that were screened prospectively for target activation. The implementation of a biomarker-driven approach using a low-frequency biomarker for patient selection across multiple tumor types can be challenging.