Background: Poor outcome in pancreatic cancer (PDA) is associated partly with stromal hyaluronan (HA) accumulation, which compromises chemotherapy perfusion. PEGPH20, PEGylated recombinant human hyaluronidase, potentiates chemotherapy by depleting HA in tumors. Methods: In an ongoing, phase II, open-label, randomized study of PEGPH20+nab-paclitaxel (Nab)+Gemcitabine (Gem) (PAG) vs Nab+Gem (AG) in previously untreated stage IV PDA, pts receive PEGPH20 3 µg/kg twice weekly (C1), then weekly (C2+) with standard AG dosing. HA status was tested retrospectively. After a temporary clinical hold (Apr-Jul 2014) for an imbalance in thromboembolic (TE) events (29% PAG vs 15% AG), the protocol was amended to exclude high-TE-risk pts and add enoxaparin (LMWH) prophylaxis. Endpoints are PFS and TE events (primary); PFS and ORR by HA level and OS (secondary). Efficacy and safety data through Dec 2014 are for pts enrolled up to clinical hold (Stage 1); TE data are through Sep 2015 (Stage 2). Results: 135 pts were treated (74 PAG, 61 AG). PFS results are shown below (median follow-up 7 mo). In HA-high pts receiving PAG vs AG, ORR was 52% (1 CR) vs 24% (P=.038); ORR was 37% vs 38% in HA-low pts. OS was 12 mo vs 9 mo (HR=0.62) despite 12/23 PAG pts discontinuing PEGPH20 at clinical hold. Common ADRs (PAG vs AG) included peripheral edema (58% vs 31%), muscle spasms (55% vs 1.6%), and neutropenia (32% vs 18%). TE events were: Stage 1 42% vs 25% (no LMWH); Stage 2 (with LMWH; 40 mg/d or 40 mg/d increased to 1 mg/kg/d) 28% vs 29%; (1 mg/kg/d) 5% vs 6%; overall (40 mg/d or 1 mg/kg/d) 13% each arm (to be updated). Conclusions: Pts with HA-high tumors receiving PAG, vs AG, showed significant improvements in PFS and ORR and a trend toward improved OS. PAG was well tolerated, with TE events reduced with LMWH prophylaxis. A global phase III trial of PAG will initiate Q1 2016. Clinical Trial Information: NCT01839487. Clinical trial information: NCT01839487