Pharmacodynamic (Phase 0) Study Using Etaracizumab in Advanced Melanoma Stergios J. Moschos,*w Cindy A. Sander,* Wenjun Wang,*w Shelley L. Reppert,* Laura M. Drogowski,* Drazen M. Jukic,*zy Uma N. M. Rao,y Charalambos Athanassiou,J Manuela Buzoianu,z Maja Mandic,# Laura Richman,z LuAnn McKinney,z Joel Leininger,z David A. Tice,z Luz Hammershaimb,z and John M. Kirkwood*w Summary: AlphaVbeta3 (a v b 3 ) is an important molecule for tumor- induced angiogenesis and is upregulated in metastatic melanoma (MM). We proposed to study the mechanism of action of etaracizumab, a monoclonal antibody targeting a v b 3 , in MM. Patients with MM and biopsiable tumor were treated with etaracizumab in 3 dose cohorts starting from 8 mg/kg. Tumor saturation by etaracizumab using LM609 immunohistochemical staining of tumor sections was the primary endpoint. Subsequent dose cohorts were defined based on the tumor saturation by etaracizumab. Secondary end points were analysis of clinical benefit and changes from baseline of several tumor and peripheral blood biomarkers. Eighteen patients were enrolled at 3 dose levels. Etaracizumab showed better melanoma cell saturation at the 8 mg/kg and 1 mg/kg dose compared with the 4 mg/kg dose and better vascular endothelial cell saturation at 8 mg/kg compared with lower dose groups. Etaracizumab demonstrated an acceptable safety profile. The optimal biologic dose out of those selected for investigation was 8 mg/kg. Patients treated at the highest dose may have had better clinical benefit secondary to suppression of the activated immediate downstream effector of a v b 3 signaling, FAK, in melanoma cells, but this alone did not ultimately affect melanoma cell proliferation or apoptosis. No apparent antiangio- genic or immunomodulatory effects of etaracizumab were noted. Key Words: melanoma, etaracizumab, pharmacodynamic, a v b 3 , FAK (J Immunother 2010;33:316–325) T o date, no systemic therapy alone or in combination with other agents, has improved overall survival of patients with metastatic melanoma (MM). 1 This may be attributed to the empiric administration of systemic therapies over the last 30 years along with intrinsic mechanisms of resistance in melanoma cells. 2 Insight into the molecular profile of melanoma may identify more rational molecular targets worthy of therapeutic consideration. Furthermore, efficiency of early drug development in MM may improve by performing phase 0 clinical trials that can ‘‘weed out’’ the drugs that do not affect targets in the human tumor or do not exhibit the mechanism of action in humans as defined in nonclinical models. 3 Cell adhesion molecules (CAMs) play important roles in cell-cell and cell-matrix interactions, and altered expres- sion of CAMs has been implicated in tumor progression, including melanocytic progression from nevi to melanoma. 4 Integrins are a subgroup of CAMs assembled from different noncovalently associated type 1 transmembrane a and b subunits with important roles in cell motility and cancer cell invasion. 5 a v b 3 recognizes a variety of ligands and is expressed by diverse cell types. Its role in tumor-induced angiogenesis has been extensively studied and reviewed 6 and is one of the major mediators of vascular endothelial growth factor (VEGF)-induced endothelial cell migration. 7 a v b 3 expression is significantly increased with the transition from benign nevi to primary melanoma and ultimately to MM. 8–10 Clustering of a v b 3 results in activation-auto- phosphorylation of focal adhesion kinase (FAK) at tyrosine 397 (Tyr 397 ), and upon interaction with Src this further potentiates FAK activity ultimately regulating multiple cellular functions such as cell growth, survival, and capacity for invasion. 11 In parallel, and/or after the activation of FAK, a v b 3 signaling is mediated through other signal transduction molecules, such as mitogen-activated protein kinase (MAPK) p44/42 (Erk1/Erk2) and protein kinase B (PKB)/Akt, 12 all of which play important roles in melanoma progression. Targeting CAMs as a means to alter melanoma pro- gression has been an area of cancer research 13 see also (http://clinicaltrials.gov/ct2/show/NCT00246012). Etaraci- zumab (Abegrin or MEDI-522, MedImmune LLC, Gaith- ersburg, MD) is a humanized, affinity-matured monoclonal antibody derived from LM609, a murine anti-human a v b 3 integrin that has shown an ability to decrease angiogenesis in vitro and to induce tumor regression in animal tumor models. 14 Several phase I studies of etaracizumab (0.4– 10 mg/kg) administered weekly in patients with solid tumors have demonstrated an acceptable safety profile, lack of immunogenicity, and disease stabilization in a subset of patients. 15,16 Driven by the high expression of a v b 3 in MM, a phase 2 randomized, open-label study of Copyright r 2010 by Lippincott Williams & Wilkins Received for publication May 7, 2009; accepted August 21, 2009. From the *Melanoma and Skin Cancer Program, University of Pittsburgh Cancer Institute; Departments of wMedicine, Division of Medical Oncology; zDermatology, Division of Dermatopathol- ogy; yPathology, University of Pittsburgh School of Medicine; JKairos Instruments, LLC; #Department of Dermatology and Immunology, University of Pittsburgh, Pittsburgh, PA; and zMedImmune, LLC, Gaithersburg, MD. Supported and funded by MedImmune, LLC. Dr Stergios J. Moschos, Dr Wenjun Wang, and Dr John M. Kirkwood have received remuneration from MedImmune for scientific and research services. Dr Manuela Buzoianu, Dr Laura Richman, Dr LuAnn McKinney, Dr Joel Leininger, Dr David A. Tice, and Dr Luz Hammershaimb are employees of MedImmune, LLC. All other authors have declared there are no financial conflicts of interest in regard to this work. Reprints: John M. Kirkwood, Hillman Cancer Center Research Pavilion, Suite 1.32, 5117 Centre Avenue, Pittsburgh, PA, 15232 (e-mail: kirkwoodjm@upmc.edu). CLINICAL STUDY 316 | www.immunotherapy-journal.com J Immunother  Volume 33, Number 3, April 2010