354 Background: Tivozanib hydrochloride (T) is a potent, selective, tyrosine kinase inhibitor of all 3 VEGF receptors with a long half-life. T has shown tolerability and has extended progression-free survival (PFS) compared with sorafenib (S; median 11.9 months vs. 9.1 months; p =0.042) in a phase III trial (TIVO-1) as initial targeted therapy for pts with mRCC. We report results of PFS subgroup analyses from TIVO-1. METHODS Pts with clear-cell mRCC, prior nephrectomy, and ≤1 prior treatment for mRCC were randomized to T (n=260) or S (n=257). Cox proportional hazards model was used to evaluate PFS. RESULTS Significant improvement in PFS by T vs. S was observed for the following prespecified subgroups: white, Eastern Cooperative Oncology Group (ECOG) performance status 0, ≥1 year since diagnosis, no prior treatment, ≥2 metastatic sites, North America/Western Europe, baseline systolic blood pressure (SBP) ≤140 mm Hg, and baseline diastolic BP (DBP) ≤90 mm Hg. Exploratory subgroup analysis showed a similar significant improvement by T vs. S in Memorial Sloan-Kettering Cancer Center (MSKCC) favorable prognostic group, and pts who developed hypertension on study had significantly longer PFS than pts with normal BP. The improvement in PFS by T vs S was more marked for the subgroups that developed hypertension (selected subgroups shown in the table). CONCLUSIONS PFS subgroup analyses showed a consistent advantage with T vs. S for mRCC. CLINICAL TRIAL INFORMATION NCT01030783. [Table: see text].