A Phase I Study of Bevacizumab, Everolimus, and Panitumumab for Patients With Advanced Solid Tumors
EGFr inhibition has been shown to have down-regulatory effects on VEGF expression and
angiogenesis. The combination of anti-VEGF and anti-EGFr targeting is clinically rational,
and preliminarily has shown at least additive, if not synergistic effects [12, 13].
Further, preclinical data has shown that constitutive activation of the AKT pathway is a
mechanism of resistance to EGFr inhibitors . Therefore, inhibition of both EGFr and AKT
pathways by panitumumab and RAD001 may create a synergistic antitumor effect. There is also
rationale that RAD001 and anti-VEGF therapies may be synergistic. Preliminary results from
a Phase I dose escalation study of bevacizumab in combination with RAD001 has reported a
recommended Phase II dose of this combination, and has described a minor response in a
colorectal cancer patient previously refractory to bevacizumab-based therapy, and over 10
months of stable disease in another colorectal cancer patient previous refractory to
bevacizumab-based therapy .
Bevicizumab (Avatstin) is a humanized monoclonal antibody to VEGF. VEGF is known to play a
pivotal role in tumor angiogenesis and is a significant mitogenic stimulus for arterial,
venous and lymphatic endothelial cells. The addition of bevacizumab to chemotherapy has
been shown to increase overall response rate, duration of response and survival for patients
with metastatic colon cancer (4) and is beneficial in first line non-small cell lung cancer
and metastatic breast cancer [1, 2], and second line metastatic colorectal cancer (7). VEGF
signals through phosphoatidylinositol 3-kinase (PI3K) and Akt as well as through the
extracellular regulated kinase (ERK 1/2), a mitogen activated protein kinase (MAPK). VEGF's
multiple biologic actions may be mediated by different pathways. Erikkson demonstrated that
VEGF induced hyperpermeability was highly dependent on activation of the AKT pathway, while
the angiogenic effect was largely unaffected by blocking this pathway and likely depended on
ERK activation .
RAD001 (Everolimus), an oral derivative of rapamycin, selectively inhibits mTOR (mammalian
target of rapamycin), an intracellular protein kinase implicated in the control of cellular
proliferation of activated T-lymphocytes or neoplastic cells. mTOR is considered to be a
downstream component of the PI3K/AKT/TSC pathway, a signalling module known to be heavily
deregulated in many human cancers[4, 5]. In this context, there is an increasing body of
evidence suggesting that AKT regulates mTOR activity[5-7], and that the activation status of
the PI3K/AKT pathway may be indicative of responsiveness to rapamycins such as RAD001.
Specifically, loss of PTEN or constitutive/hyper-activation of AKT has been suggested to
sensitize tumors to the effects of inhibition of mTOR[6-8]. Indeed, RAD001 preferentially
inhibits the proliferation of tumor cells displaying high AKT activity and totally reverses
AKT-driven prostate intraepithelial neoplasia in a mouse transgenic model. Rapamycins
also inhibit downstream signaling pathways of VEGF. The rapamycin-regulated PI3K and p70s6
pathways are known to be involved in mediating VEGF's effects on endothelial cells . In
animal models, rapamycins modestly decrease tumor VEGF expression, and significantly blunt
typical angiogenic responses to VEGF. Everolimus has been shown to inhibit tumor growth and
reduce number of blood vessels in a murine melanoma model, indicating that RAD001 has direct
antiangiogenic effects .
Panitumumab (Vectibix) is a fully humanized monoclonal antibody directed against epidermal
growth factor receptor (EGFr), which is a 170-kD transmembrane glycoprotein with a
cytoplasmic protein kinase domain essential for tumor growth and division. The receptor
binds multiple ligands including epidermal growth factor and transforming growth
factor-alpha (TGF-alpha). The tyrosine kinase intracellular domain of the receptor is
activated via binding of a ligand to EGFr, which in turn initiates a cascade of
intracellular signals. These downstream signaling pathways again include the phosphorylation
of mitogen-activated protein kinase (MAPK) through the ras/raf pathway. Inhibition of these
signaling pathways can result in cell growth arrest and apoptosis, respectively.
1. Sandler, A.B., et al. Randomized phase II/III trial of paclitaxel (P) plus carboplatin
(C) with or without bevacizumab (NSC #704865) in patients with advanced non-squamous
non-small cell lung cancer (NSCLC): An Eastern Cooperative Oncology Group (ECOG)
Trial- E4599. in Proc Am Soc Clin Oncol. 2005.
2. Miller, K.D., et al. E2100: A randomized phase III trial of paclitaxel versus
paclitaxel plus bevacizumab as first line threapy for locally recurrent or metastatic
breast cancer. in American Society for Clinical Oncology. 2005. Orlando, FL.
3. Eriksson, A., et al., Small GTP-binding protein Rac is an essential mediator of
vascular endothelial growth factor-induced endothelial fenestrations and vascular
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cancer. Nature Cancer, 2002. 2: p. 489-501.
5. Krymskaya, V.P., Tumor suppressors hamartin and tuberin: intracellular signaling. Cell
Signal, 2003. 15: p. 729-739.
6. Bjornsti, M.-A. and P.J. Houghton, The TOR pathway: A target for cancer chemotherapy.
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7. Majumder, P.K., et al., mTOR inhibition reverses Akt-dependent prostate intraepithelial
neoplasia through regulation of apoptotic and HIF-1-dependent pathways. Nat Med, 2004.
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8. Noh, W.C., et al., Determinants of rapamycin in breast cancer cells. Clin Cancer Res,
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mediate the mitogenic response of human endothelial cells to vascular endothelial
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12. Spigel, D.R., et al. Bevacizumab and erlotinib in the treatment of patients with
metastatic renal cell cancer (RCC): Update of a phase II multicenter trial. in Proc Am
Soc Clin Oncol. 2005.
13. Saltz, L.B., et al. Randomized phase II trial of cetuximab/bevacizumab/irinotecan (CBI)
versus cetuximab/bevacizumab (CB) in irinotecan-refractory colorectal cancer. in Proc
Am Soc Clin Oncol. 2005.
14. She, Q.B., et al., Resistance to gefitinib in PTEN-null HER-overexpressing tumor cells
can be overcome through restoration of PTEN function or pharmacologic modulation of
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15. Zafar, Y., et al. Preliminary results of a phase I study of bevacizumab (BV) in
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Endpoint Classification: Safety/Efficacy Study, Intervention Model: Single Group Assignment, Masking: Open Label
To determine the MTD/recommended phase II regimen and evaluate safety of panitumumab added to RAD001 plus bevacizumab in adult patients with advanced solid tumors.
Every cycle (28-days)
Herbert I Hurwitz, MD
United States: Institutional Review Board
|Duke University Medical Center||Durham, North Carolina 27710|