RAD001 and Erlotinib in Patients With Neuroendocrine Tumors

Preclinical data suggest that concomitant inhibition of two non-redundant amplified pathways (mTOR and EGFR) can reverse drug resistance and more profoundly affect tumor growth than targeting either pathway alone. EGFR inhibitors may abrogate feedback loops that stimulate upstream signaling events such as PI3K and Akt in the face of mTOR inhibition. Although ErbB receptors signal through mTOR-dependent mechanisms, mTOR-independent ErbB receptor signaling also occurs in cancer. Furthermore, deregulation of apoptotic pathways like the PI3K/Akt/PTEN axis (e.g. via PTEN loss of function or AKT gene amplification) may lead to resistance to EGFR inhibitors. Treatment with an inhibitor of mTOR may reverse this resistance. Targeting the mTOR and EGFR pathways concurrently may more effectively inhibit tumor growth than inhibiting either pathway alone. The compelling preclinical data, coupled with modest single agent activity seen with EGFR inhibition and mTOR inhibition in neuroendocrine tumors (NETs), provides a strong rationale for studying the activity of concomitant pathway inhibition in patients with advanced NETs. Support for this strategy also stems from the fact that EGFR inhibitors can be safety combined with mTOR inhibitors in humans. Emerging data from a phase I study of RAD001 plus erlotinib in patients with previously treated advanced non-small cell lung cancer (NSCLC) suggests that the two agents can be safely combined at the following doses: RAD001 5 mg PO q D and erlotinib 150 mg PO qD. Of note, the original dose selections for RAD001 and erlotinib for this study stem directly from phase I studies with this combination (RAD001 5 mg PO qD plus erlotinib 150 mg PO qD). The modified dose selections (RAD001 5 mg PO qD plus erlotinib 100 mg PO qD) are the result of integrating discussions with the study sponsor, preliminary safety data from the first few patients enrolled in this study (suggesting that some patients tolerate full-dose therapy and others do not) and additional phase I data suggesting that the maximum tolerated dose (MTD) in some patient populations is lower than in others, e.g. the MTD in breast cancer patients is RAD001 2.5 mg PO qD and erlotinib 100 mg PO QD (Mayer et al. American Society of Clinical Oncology (ASCO) 2009 Breast Cancer Symposium, Abstract #254).