Background: In the randomized phase 3 CONCUR trial (NCT01584830), regorafenib significantly improved overall survival (OS) and progression-free survival (PFS) vs placebo (PBO) in Asian patients (n = 136 regorafenib; n = 68 PBO) with treatment-refractory mCRC (HR [95% CI]: OS 0.55 [0.40‒0.77]; PFS 0.31 (0.22‒0.44]). Protein biomarker data from the phase 3 CORRECT trial of mostly Western patients with mCRC identified TIE-1 as a potential predictor of clinical response to regorafenib; however, this association was not significant in multivariable analyses. We present an exploratory protein biomarker analysis of patients in CONCUR. Methods: Sixteen proteins of interest, many of which are involved in angiogenesis, were quantified by multiplex immunoassay or ELISA in plasma samples collected at study entry from 121/204 (59%) patients (n = 83 regorafenib; n = 38 PBO). Potential predictive and prognostic effects were evaluated. Results: The biomarker cohort was representative of the overall study population in major baseline demographic factors, OS (HR 0.61; 95% CI 0.40‒0.93), and PFS (HR 0.25; 95% CI 0.16‒0.39). Elevated levels of ANG-2 (HR 2.46; p = 0.0016) and VEGF-A (HR 1.38; p = 0.03) were associated with poor OS prognosis; however, no significant association with treatment OS benefit for regorafenib vs PBO was observed for either marker (ANG-2: HR 0.76; p = 0.3307; VEGF-A: HR 0.83; p = 0.20). Elevated levels of five plasma proteins were associated with poor PFS prognosis: ANG-2 (HR 1.73; p = 0.0085), VEGF-A (HR 1.30; p = 0.0308), IL-8 (HR 1.67; p = 0.0014), VWF (HR 2.39; p = 0.0029), and IGF-BP2 (HR 1.71; p = 0.0384). Elevated levels of IL-8 (HR 0.70; p = 0.019), VWF (HR 0.53; p = 0.0312), and IGF-BP2 (HR 0.60; p = 0.0336) showed a modest interaction with regorafenib PFS; however, these results did not reach statistical significance after adjustment for multiple testing (p = 0.0045). Conclusions: None of the plasma proteins analyzed were predictive of regorafenib clinical benefit as measured by both OS and PFS in Asian patients with mCRC. These results, as well as those in CORRECT, suggest that rationally selected protein markers are not suitable to predict treatment benefit of regorafenib. Clinical trial information: NCT01584830