Harding JJ, et al. - In this single-center, open-label, phase 1 trial, researchers tested the safety and tolerability of pegylated arginine deiminase (ADI-PEG 20) and modified FOLFOX6 (mFOLFOX6) for treatment-refractory hepatocellular carcinoma (HCC) and other advanced gastrointestinal tumors. They also determined the recommended phase 2 dose (RP2D) of ADI-PEG 20. They used a 3 + 3 dose escalation design and employed a RP2D expansion cohort to define the objective response rate (ORR). Also, they evaluated progression-free survival (PFS), overall survival (OS), and explored pharmacodynamics and immunogenicity. Findings revealed acceptable safety profile and favorable efficacy of concurrent mFOLFOX6 plus ADI-PEG-20 when administered intramuscularly at 36 mg/m² weekly relative to historic controls. Thrombocytopenia, neutropenia, leukopenia, anemia, and fatigue were the most common adverse events.