Preclinical Development Effects of Anti-VEGF on Pharmacokinetics, Biodistribution, and Tumor Penetration of Trastuzumab in a Preclinical Breast Cancer Model Cinthia V. Pastuskovas 1 , Eduardo E. Mundo 1 , Simon P. Williams 1 , Tapan K. Nayak 2 , Jason Ho 1 , Sheila Ulufatu 1 , Suzanna Clark 1 , Sarajane Ross 1 , Eric Cheng 1 , Kathryn Parsons-Reponte 1 , Gary Cain 1 , Marjie Van Hoy 1 , Nicholas Majidy 1 , Sheila Bheddah 1 , Josefa dela Cruz Chuh 1 , Katherine R. Kozak 1 , Nicholas Lewin-Koh 1 , Peter Nauka 1 , Daniela Bumbaca 1 , Mark Sliwkowski 1 , Jay Tibbitts 1 , Frank-Peter Theil 1 , Paul J. Fielder 1 , Leslie A. Khawli 1 , and C. Andrew Boswell 1 Abstract Both human epidermal growth factor receptor 2 (HER-2/neu) and VEGF overexpression correlate with aggressive phenotypes and decreased survival among breast cancer patients. Concordantly, the combination of trastuzumab (anti-HER2) with bevacizumab (anti-VEGF) has shown promising results in preclinical xenograft studies and in clinical trials. However, despite the known antiangiogenic mechanism of anti-VEGF antibodies, relatively little is known about their effects on the pharmacokinetics and tissue distribution of other antibodies. This study aimed to measure the disposition properties, with a particular emphasis on tumor uptake, of trastuzumab in the presence or absence of anti-VEGF. Radiolabeled trastuzumab was administered alone or in combination with an anti-VEGF antibody to mice bearing HER2-expressing KPL-4 breast cancer xenografts. Biodistribution, autoradiography, and single-photon emission computed tomography–X-ray computed tomography imaging all showed that anti-VEGF administration reduced accumulation of trastu- zumab in tumors despite comparable blood exposures and similar distributions in most other tissues. A similar trend was also observed for an isotype-matched IgG with no affinity for HER2, showing reduced vascular permeability to macromolecules. Reduced tumor blood flow (P < 0.05) was observed following anti- VEGF treatment, with no significant differences in the other physiologic parameters measured despite immunohistochemical evidence of reduced vascular density. In conclusion, anti-VEGF preadministration decreased tumor uptake of trastuzumab, and this phenomenon was mechanistically attributed to reduced vascular permeability and blood perfusion. These findings may ultimately help inform dosing strategies to achieve improved clinical outcomes. Mol Cancer Ther; 11(3); 752–62. Ó2012 AACR. Introduction Despite advances in prevention, diagnosis, and treat- ment, cancer remains a major health challenge. In the past decade, significant progress has been made in the field of monoclonal antibody (mAb) therapy (1). However, the standard treatment option of single-drug therapy yields limited success due to low rates of complete remission and resistance. There is a growing consensus that the future of cancer treatment for solid tumors with immunotherapy lies in a combination therapy approach (1, 2). Trastuzumab is a humanized mAb that specifically targets the extracellular domain of the human epidermal growth factor receptor-2 (HER2; refs. 3–5). The HER2 gene is amplified or the receptor overexpressed in approxi- mately 15% to 25% of breast cancers (HER2-positive tumors; refs. 6, 7) and is associated with poor prognosis (8). Despite the success of trastuzumab treatment as a single agent (9) or in combination with chemotherapy (10), intrinsic and acquired resistance to trastuzumab treat- ment has led to the investigation of trastuzumab in com- bination with other therapeutic agents (11). In breast cancer, HER2 and VEGF signaling pathways are linked, as upregulation of VEGF occurs in HER2-over- expressing breast cancer in the most aggressive cases (12). VEGF is responsible for recruiting de novo vascularization of the tumor, a process that is critical in all stages of Authors' Affiliations: 1 Genentech Research and Early Development, South San Francisco, California; and 2 Pharma Research and Early Devel- opment, Hoffmann-La Roche Ltd., Basel, Switzerland Note: Supplementary data for this article are available at Molecular Cancer Therapeutics Online (http://mct.aacrjournals.org/). Corresponding Authors: Leslie A. Khawli, Early Development Pharma- cokinetics and Pharmacodynamics, Genentech, Inc., South San Fran- cisco, CA 94080. Phone: 650-225-6509; Fax: 650-742-5234; E-mail: khawli.leslie@gene.com; and C. Andrew Boswell, Phone: 650-467- 4603; Fax: 650-742-5234; E-mail: boswell.andy@gene.com doi: 10.1158/1535-7163.MCT-11-0742-T Ó2012 American Association for Cancer Research. Molecular Cancer Therapeutics Mol Cancer Ther; 11(3) March 2012 752 on April 24, 2020. © 2012 American Association for Cancer Research. mct.aacrjournals.org Downloaded from Published OnlineFirst January 5, 2012; DOI: 10.1158/1535-7163.MCT-11-0742-T