Abstract Hyaluronan (HA) over-accumulation in the extracellular matrix (ECM) of many solid tumors is associated with tumor progression and poor prognosis (Tammi 2008). In preclinical animal models, enzymatic removal of ECM HA with pegylated recombinant human hyaluronidase PH20 (PEGPH20) is associated with remodeling of the tumor stroma, reduction of tumor interstitial fluid pressure, expansion of tumor blood vessels and facilitated delivery of chemotherapy (Thompson 2010, Jacobetz 2012, Provenzano 2012). Additionally, epidermal growth factor receptor (EGFR), a tyrosine kinase essential for cell division and tumor growth, has been implicated in multiple epithelial malignancies and is over expressed in ∼60% of human pancreatic carcinomas (Frolov 2007). Cetuximab (CET), a chimeric monoclonal antibody (mAb), targets EGFR preventing tyrosine kinase mediated phosphorylation and subsequent signal transduction (Enrique 2012). As pancreatic ductal adenocarcinoma (PDA) has been identified as a cancer type that expresses high levels of HA (∼87%; Jiang 2010), studies were conducted to evaluate PEGPH20 enhancement in anti-tumor activity of CET in an EGFR positive HA-overexpressing PDA BxPC3/HAS3 xenograft model (Kultti 2013). In brief, NCr nu/nu mice were inoculated with PDA BxPC3/HAS3 cells adjacent to the tibial periosteum, and tumor growth was monitored with 3D high resolution ultrasonography. When tumors reached ∼200 mm3, mice were treated with: (1) vehicle control; (2) PEGPH20 alone, 1 mg/kg; (3) CET alone, 0.03 mg; (4) CET alone, 0.1 mg; (5) PEGPH20 plus CET, 0.03 mg; or (6) PEGPH20 plus CET, 0.1 mg. Vehicle control or PEGPH20 was given intravenously while CET was administered intraperitoneally starting on study day 0, and then dosed twice weekly for 3 weeks (BIWx3). At study termination, the average tumor growth inhibition (TGI) of CET (0.03 mg) was not significantly different from vehicle-treated animals; however, PEGPH20 alone (78%, p<0.05) and CET alone at 0.1 mg (61%, p<0.05) inhibited tumor growth. The addition of PEGPH20 to the 0.03 mg and 0.1 mg CET groups increased TGI to 88% (p<0.05) for both treatments, relative to vehicle. In a second study, when tumors reached ∼200 mm3, mice were treated with: (1) vehicle control; (2) PEGPH20 alone, 37.5 µg/kg (3 µg/kg human equivalent dose); (3) CET alone, 0.03 mg; or (4) PEGPH20 plus CET. Animals were dosed as described above. At study termination, the average TGI of CET alone was not significantly different from vehicle-treated animals; however, PEGPH20 alone significantly inhibited tumor growth (47%, p<0.05). The combination of PEGPH20 and CET increased TGI to 70% (p<0.05) relative to vehicle. In conclusion, PEGPH20 treatment of HA-overexpressing tumors potentiates the subsequent anti-tumor activity of mAbs, such as CET. Citation Format: Ryan J. Osgood, James F. Skipper, Susan Zimmerman, Rebecca C. Symons, Harold M. Shepard, Daniel C. Maneval, Curtis B. Thompson, David W. Kang. Pegylated recombinant human hyaluronidase PH20 (PEGPH20) enhances cetuximab efficacy in BxPC-3/HAS3 human pancreatic cancer xenografts. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3646. doi:10.1158/1538-7445.AM2014-3646