Introduction: Cabozantinib, an inhibitor of MET, AXL, and VEGF receptors, significantly improved overall survival (OS) and progression-free survival (PFS) versus placebo in patients with previously treated advanced hepatocellular carcinoma (HCC). In this exploratory analysis, outcomes were evaluated according to plasma biomarker levels., Methods: Baseline plasma levels were evaluated for MET, AXL, VEGFR2, HGF, GAS6, VEGF-A, PlGF, IL-8, EPO, ANG2, IGF-1, VEGF-C, and c-KIT for 674/707 randomized patients; and Week 4 levels were evaluated for MET, AXL, VEGFR2, HGF, GAS6, VEGF-A, PlGF, IL-8, and EPO for 614 patients. OS and PFS were analyzed by baseline levels as dichotomized or continuous variables and by on-treatment changes at Week 4 as continuous variables; biomarkers were considered potentially prognostic if p < 0.05 and predictive if p < 0.05 for the interaction between treatment and the biomarker. Multivariable analyses adjusting for clinical covariates were also performed., Results: In the placebo group, high levels of MET, HGF, GAS6, IL-8, and ANG2 and low levels of IGF-1 were associated with shorter OS in univariate and multivariable analyses; these associations were also observed for MET, IL-8, and ANG2 in the cabozantinib group. Hazard ratios for OS and PFS favored cabozantinib over the placebo at low and high baseline levels for all biomarkers. No baseline biomarkers were predictive of a treatment benefit. Cabozantinib promoted pharmacodynamic changes in several biomarkers, including increases in VEGF-A, PlGF, AXL, and GAS6 levels and decreases in VEGFR2 and HGF levels; these changes were not associated with OS or PFS., Conclusion: Cabozantinib improved OS and PFS versus placebo at high and low baseline concentrations for all biomarkers analyzed. Low baseline levels of MET, HGF, GAS6, IL-8, and ANG2 and high levels of IGF-1 were identified as potential favorable prognostic biomarkers for survival in previously treated advanced HCC. Although cabozantinib promoted pharmacodynamic changes in several biomarkers, these changes were not associated with survival., Competing Interests: G.K.A.-A. reports research grants from Acta Biologica, Agios, AstraZeneca, Bayer, Beigene, Berry Genomics, BMS, Casi, Celgene, Exelixis, Genentech/Roche, Halozyme, Incyte, MabVax, Puma, QED, Sillajen, and Yiviva and consulting fees from Agios, AstraZeneca, Autem, Bayer, Beigene, Berry Genomics, Celgene, CytomX, Debio, Eisai, Lilly, Exelixis, Flatiron, Genentech/Roche, Gilead, Helio, Incyte, Ipsen, Loxo, Merck, MINA, Polaris, QED, Redhill, Silenseed, Sillajen, Sobi, Therabionics, Twoxar, Vector, and Yiviva. J.-F.B. reports personal fees from Ipsen, Bayer, Eisai, Roche, AstraZeneca, and BMS. Y.-W.C. reports payment to employer from Exelixis for statistical analysis during the conduct of the study. A.L.C. reports grant and nonfinancial support from Exelixis during the conduct of the study, including support of the parent study and funding of editorial support; honoraria and advisory/consulting fees from AstraZeneca, BMS, Exelixis, Ipsen, Bayer, and Merck; honoraria, advisory/consulting fees, and speaker bureau fees from Eisai, Novartis, and Ono Pharmaceutical; honoraria, advisory/consulting fees, and travel and accommodation expenses from Genentech/Roche and IQVIA; speaker bureau fees and travel and accommodation expenses from Bayer Yakuhin; and speaker bureau fees from Amgen Taiwan; A.L.C. is an editorial board member of Liver Cancer. A.E.-K. reports personal fees and nonfinancial publication support from Exelixis during the conduct of the study; personal fees from Genentech/Roche, BMS, Eisai, and Merck; grants and personal fees from AstraZeneca; personal fees from Bayer, Gilead, QED, Agenus, ABL Bio, Pieris, Cytomx, and EMD Serono; and grants from Astex. R.K.K. reports research funding grants to institution for conduct of clinical trials from Exelixis; research funding grants to institution for conduct of clinical trials and Steering Committee membership from Agios, AstraZeneca, BMS, and Merck; research funding grants to institution for conduct of clinical trials from Bayer, Lilly, EMD Serono, Novartis, QED, and Taiho; IDMC membership and advisory board fees from Genentech/Roche; personal fees for travel support and advisory board participation from Ipsen; and advisory board fees from Gilead and Exact Sciences. H.Y.L. reports no conflicts of interest. P. McAdam reports payment to employer from Exelixis for statistical analysis during the conduct of the study. P. Merle reports advisory board fees from Roche, Bayer, Lilly, Merck, Eisai, and AstraZeneca and grants and advisory board fees from Ipsen and Genosciences. T.M. reports consultancy fees from AstraZeneca, Bayer, Eisai, Ipsen, and Roche and research grants from BTG and Bayer. J.-W.P. reports grants from Ipsen-Exelixis, Genentech/Roche, AstraZeneca, and Merck and personal fees from Ipsen-Exelixis, Genentech/Roche, Bayer, Eisai, and AstraZeneca. L.R. reports grants to institution for the CELESTIAL trial, medical writing assistance, and nonfinancial support from Exelixis during the conduct of the study; consulting/advisory role fees from Amgen, ArQule, AstraZeneca, Basilea, Bayer, BMS, Celgene, Eisai, Exelixis, Genenta, Hengrui, Incyte, Ipsen, IQVIA, Lilly, Merck, Nerviano Medical Sciences, Roche, Sanofi, Servier, and Zymework; honoraria/lecture fees from AbbVie, Amgen, Bayer, Eisai, Gilead, Incyte, Ipsen, Lilly, Merck Serono, Roche, and Sanofi; travel expenses from Ipsen; and research funding grants to institution from Agios, ARMO BioSciences, AstraZeneca, Beigene, Eisai, Exelixis, Fibrogen, Incyte, Ipsen, Lilly, Merck, Nerviano Medical Sciences, Roche, and Zymeworks. B.-Y.R. has nothing to disclose. E.W. reports employment and stock ownership from Exelixis., (Copyright © 2021 by S. Karger AG, Basel.)