Background: PEGPH20 is a PEGylated version of human recombinant hyaluronidase. In preclinical studies, PEGPH20 depleted pancreatic cancers of their high hyaluronan (HA) content. In a genetically-engineered murine model of PDA, PEGPH20 + gemcitabine (Gem) significantly prolonged survival compared to Gem alone. In Ph1 PEGPH20 monotherapy studies, the MTD was 3.0 μg/kg. The most common AEs were musculoskeletal events (MSEs). Methods: This was a dose-escalation study to find the recommended Phase 2 dose (RP2D) of PEGPH20 in combination with Gem in patients (pts) with Stage IV previously untreated pancreatic cancer. Pts received PEGPH20 at 1, 1.6, or 3 μg/kg IV twice a week for Wks 1-4, weekly for Wks 5-7, then 1 wk rest. Dose escalation was based on safety. Gem was given at 1000 mg/m² IV once a week for Wks 1-7, then 1 wk rest. Thereafter, PEGPH20 + Gem were given once a week for 3 wks in 4-wk cycles. Dexamethasone was given pre and post PEGPH20 doses. Results: Of the 28 pts enrolled, the majority had a Karnofsky performance status of 80%, and 85%/19%/26% of pts had liver/lung/visceral metastases. The median age was 58 yrs. Four pts received PEGPH20 at 1 μg/kg, 4 at 1.6 μg/kg, and 20 at 3 μg/kg. The RP2D was 3 μg/kg. Treatment duration ranged from 1-274 days; 5 pts remain on study. Treatment was generally well tolerated. Ten pts had 1 Gem dose reduction, 2 pts had 1 PEGPH20 dose reduction (3 to 1.6 µg/kg), but no pt had a DLT. The most common PEGPH20-related AEs were MSEs (25% Gr1; 18% Gr2) and fatigue (21% Gr1; 11% Gr2). Objective response was assessed by an independent central radiologist using RECIST 1.1. Of the 21 pts evaluable for efficacy, 7 had partial response (PR) for an overall response rate (ORR) of 33%, and 9 had stable disease for ≥ 2 mo. Tumor biopsies from 12 pts were evaluable for HA staining. HA was high in 9 and low in 3. Of the 9 with high HA staining, 5 had PR (56% ORR); HA data were not available for the other 2 PR pts. PK results show dose-dependent exposure consistent with data from PEGPH20 monotherapy studies. Conclusions: PEGPH20 in combination with Gem is generally well tolerated in advanced pancreatic cancer and shows promising efficacy, especially in pts with high intratumoral HA content. Clinical trial information: NCT01453153.