Epidermal growth factor receptor inhibitors in development for the treatment of non-small cell lung cancer

The epidermal growth factor receptor (EGFR) inhibitors erlotinib, gefitinib, and cetuximab have undergone extensive clinical testing and have established clinical activity in non-small cell lung cancer and other types of solid tumors. A number of newer inhibitors are currently in clinical development with different spectra of activity or mechanisms of receptor inhibition. These include monoclonal antibodies, such as panitumumab and matuzumab; dual inhibitors of EGFR and vascular endothelial growth factor receptor, such as ZD6474 and AEE788; inhibitors of multiple EGFR family members, such as lapatinib; and irreversible inhibitors, such as canertinib and HKI272. Preclinical studies suggest that several of these agents may have activity in tumors refractory to erlotinib or gefitinib. Among these agents, ZD6474 has undergone the most extensive clinical testing. The antitumor activity of ZD6474 in these two randomized phase II clinical trials in patients with non-small cell lung cancer was felt to be sufficiently promising to warrant phase III clinical testing. Several of the other EGFR inhibitors are also undergoing advanced clinical testing, either alone or in combination with other agents. EGFR has now been validated as a clinically relevant target, and several different types of agents inhibiting this receptor are currently in development. Future research will be needed to elucidate the role of these agents in patients with EGFR inhibitor-naive and EGFR inhibitor-refractory disease, to define the molecular characteristics that predict response, and to determine whether these drugs should be used in combination with other targeted agents or chemotherapy.

Rationale and clinical experience with epidermal growth factor receptor inhibitors in gynecologic malignancies

The family of epidermal growth factor receptors (EGFRs) is overexpressed in many gynecologic malignancies. Extensive preclinical studies of these receptors demonstrate that they play an important role in supporting the growth of a wide variety of malignancies and that interruption of receptor function or signaling from these receptors leads to inhibition of tumor growth or in certain cases tumor regression. Recently, many therapeutic agents targeting this receptor have entered the clinic and phase II clinical studies have demonstrated activity in lung cancer, colon cancer, and head and neck malignancies. Phase II trials of both small molecule inhibitors of EGFR and antibody-based inhibitors are underway in both cervical and ovarian cancer and emerging data suggests that their activity in unselected women with advanced gynecologic malignancies is very modest. Recently, molecular analysis of lung cancers has identified that the response to small molecule inhibitors of EGFR is highly correlated with activating mutations within the EGFR. It is possible that these agents will be highly effective in a small subset of patients with gynecologic malignancies whose tumors are dependent on EGFR signaling, perhaps through an activating mutation in EGFR or its downstream pathway. Until additional research can identify the subset of patients most likely to benefit from this targeted therapy, treatment for women with gynecologic malignancies with EGFR inhibitors should be limited to investigational trials. It is critical that these trials have access to tissue of responding and nonresponding patients so to determine the rational use of these agents in the treatment of gynecologic malignancies.