Background: Sorafenib has been the only FDA-approved medication for inoperable HCC (iHCC) as first line. Agents with better tolerability and potential to improve progression-free-survival (PFS) are needed. Tivozanib (TIVO) is an inhibitor of vascular endothelial growth factor (VEGF) tyrosine kinase, inhibiting angiogenesis critical in HCC. Methods: This is a phase 1b/2 study with HCC patients (pts) having a measurable disease, Child-Pugh class A, and no prior systemic therapy. Phase 1b portion followed a modified 3 + 3 design; phase 2 portion was a two-stage, single arm, un-blinded study. Adverse events were categorized based on CTCAE, and tumor imaging was assessed per RECIST. Results: At 3 centers with IRB approval, 21 eligible pts were enrolled. In phase 1b, 8 pts were enrolled at a starting dose of 1mg once daily q21days with one week off. Upon escalation to 1.5mg, two pts had dose limiting toxicities (DLTs, grade 3 mucositis and hypertension) and came off study without completing the DLT period. The dose of TIVO was de-escalated to 1 mg, and the accrual of remaining patients to phase 2 portion occurred at 1 mg. In a total of 19 pts, median follow up was 16.9 months (mo). The primary endpoint of median PFS was 5.5 mo. Partial response (PR) was seen in 4/19 (21%) and stable disease (SD) in 8/19 (42%): disease control rate was 63%. Overall survival (OS) at 6 and 12 mo was 58% and 25%. Median OS was 7.5 mo. Three pts have remained on TIVO for > 2 years. Viral loads of hepatitis B and C remained stable during the study. Adverse events (AEs) related to TIVO included grade 3 fatigue (15.7%), decreased appetite (5.3%), pulmonary embolism (5.3%), hand-foot syndrome (5.3%), elevated LFT (10.5%), and grade 4 hypertension (5.3%). Conclusions: TIVO is tolerable at 1 mg in iHCC. In few pts, TIVO had deep and durable responses. Biomarker driven studies of TIVO in the context of immunotherapy are warranted. Acknowledgment: We appreciate support from NCCN. Clinical trial information: NCT01835223