Halo 110-101: Early safety results of pegvorhyaluronidase alfa (PEGPH20; PVHA) + cisplatin (C) + gemcitabine (G) ± atezolizumab (ATZ) in patients (pts) with locally advanced or metastatic cholangiocarcinoma (CCA) and gallbladder cancer (GBC).

408Background: Standard of care for CCA/GBC is C-G therapy. MAbs (ATZ, pembrolizumab) targeting PD-L1 show promise in treating CCA/GBC. Hyaluronan (HA), which may impede drug and immune cell access, is high (67%) in CCA/GBC tumors. PEGPH20 enzymatically degrades HA. HALO 110-101 (NCT03267940) evaluates safety and activity of PEG-C-G-ATZ or PEG-C-G versus C-G in CCA/GBC pts. Methods: This study comprises two parts. In Run-In (RI) six pts were enrolled in PEG-C-G arm, then six pts in PEG-C-G-ATZ arm. Eight additional pts may be enrolled for tolerability. In Expansion (EX), up to 50 pts will be enrolled for efficacy. Treatment (Tx) cycle is 21 days (d). PEGPH20 dose is 3 μg/kg on d1, eight and 15 and ATZ dose is 1200 mg (one–three hours after PEGPH20) on d1 (PEG-C-G-ATZ only). C-G is dosed at 25 mg/m2 C and 1000 mg/m2 G on d2 and nine. In C-G arm (EX only), C-G is dosed on d1 and 8. Primary endpoints are ORR (RECIST v1.1), AEs (NCI CTCAE v4.03), laboratory/safety (RI only); secondary endpoints are PK; DOR, D...