Abstract Hyaluronan (HA) accumulates in the extracellular matrix (ECM) of many solid tumors, including those of the prostate, colon, breast, stomach, ovary, and pancreas. This accumulation is associated with tumor progression and a negative clinical outcome. Accordingly, an HA-degrading enzyme, pegylated recombinant human hyaluronidase PH20 (PEGPH20), was developed to target tumor-associated HA in the ECM. Preclinical studies demonstrated that PEGPH20-mediated removal of HA from HA-rich xenograft tumors in mice decreased tumor interstitial fluid pressure and tumor water content resulting in a decompression of tumor vasculature, increased tumor vascular perfusion, tumor growth inhibition (TGI) and enhanced chemotherapeutic activity (Thompson 2010). We further characterized HA expression across multiple human tumor types and identified pancreatic ductal adenocarcinoma (PDA) as the cancer type with the most HA (∼87% express high levels). These observations coupled with a lack of curative therapy for PDA led us to evaluate alternative treatment strategies for PDA. Specifically, using the peritibial BxPC-3 human pancreatic cancer xenograft model, we investigated whether the antitumor activity of Nab-Paclitaxel was significantly enhanced with PEGPH20 treatment. Nude mice were inoculated with human PDA BxPC-3 cells adjacent to the right tibial periosteum, and tumor growth was monitored with ultrasonography. When tumors reached ∼400 mm3 (n≥8/group), mice were staged into 8 treatment groups: (1) vehicle control; (2) PEGPH20 monotherapy, 4.5 mg/kg; (3) Nab-Paclitaxel, 3 mg/kg; (4) Nab-Paclitaxel, 10 mg/kg; (5) Nab-Paclitaxel, 30 mg/kg; (6) Nab-Paclitaxel, 3 mg/kg, plus PEGPH20; (7) Nab-Paclitaxel, 10 mg/kg, plus PEGPH20; or (8) Nab-Paclitaxel, 30 mg/kg, plus PEGPH20. Vehicle or PEGPH20 ± Nab-Paclitaxel was administered intravenously starting on study day 0, and then dosed every third day for 15 days. At study termination, the average TGIs from animals treated with either PEGPH20 alone (12.2%), low dose (3 mg/kg) Nab-Paclitaxel (20.3%), or low dose Nab-Paclitaxel (3 mg/kg) plus PEGPH20 (25%) were not significantly different from vehicle-treated animals. However, Nab-Paclitaxel alone at both 10 mg/kg (61.5%, p<0.01) and 30 mg/kg (73.6%, p<0.01) inhibited tumor growth. High doses of Nab-Paclitaxel (30 mg/kg) ± PEGPH20 was associated with dose-related toxicity. The addition of PEGPH20 to the 10 mg/kg and 30 mg/kg Nab-Paclitaxel groups increased TGI to 71.7% (p<0.01), and 90.8% (p<0.01), respectively, relative to vehicle. These findings suggest that PEGPH20 significantly increases the anti-tumor efficacy of Nab-Paclitaxel in HA-rich PDA tumors at moderate to high Nab-Paclitaxel doses (10 and 30 mg/kg). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5635. doi:1538-7445.AM2012-5635