Definition

The tosylate salt form of varlitinib, an orally bioavailable inhibitor of the epidermal growth factor receptor family with potential antineoplastic activity. Varlitinib selectively and reversibly binds to both EGFR (ErbB-1) and Her-2/neu (ErbB-2) and prevents their phosphorylation and activation, which may result in inhibition of the associated signal transduction pathways, inhibition of cellular proliferation and cell death. EGFR and Her-2 play important roles in cell proliferation and differentiation and are upregulated in various human tumor cell types. Due to the dual inhibition of both EGFR and Her-2, this agent may be therapeutically more effective than agents that inhibit EGFR or Her-2 alone.