Background: Pretreatment neutrophil to lymphocyte (L) (NLR), platelet to L (PLR), and L to monocyte (LMR) levels are established prognostic biomarkers for advanced NSCLC. Plinabulin (Plin) is a well-tolerated, differentiated tubulin-binding agent being developed for neutropenia prevention as a monotherapy and in combination, and for improving the efficacy of anticancer agents. DUBLIN-3 (NCT02504489) was a randomized, single-blinded (pts only), active-controlled Ph3 study in 2^nd/3^rd line stage IIIB/IV, EGFR WT NSCLC with a measurable lung lesion (RECIST 1.1). Pts (N = 559) were randomized 1:1 to Plin/Doc or Doc (21-day (D) cycle (C)). Doc (75 mg/m²) on D1 and Plin (30 mg/m²) on D1/D8 were given by IV infusion with steroid premedication (8 mg PO BID x 3D). Differential WBCs and platelet counts were collected at baseline (pre-steroid), D1, and D8. We analyzed the posttreatment effects of Plin on NLR, PLR, and LMR. Methods: All evaluable Plin/Doc vs Doc pts were included. NLR/PLR/LMR ratios and their respective change from baseline (cNLR/cPLR/cLMR) were obtained from blood draws taken at predose, C1D8, and/or C2D8. For intra/inter-arm overall survival (OS) stratification, baseline median NLR (3.2), PLR (177), and LMR (3.5) values were selected as thresholds. By examining responders & long-term survivors in both arms, posttreatment NLR/LMR and cNLR/cLMR thresholds were established for C1D8 and C2D8. Finally, PFS/OS benefits were stratified to determine the statistical significances of Plin/Doc vs Doc. Results: In agreement with literature, baseline threshold levels for NLR = 3.2, PLR = 177, LMR = 3.5 were statistically significantly predictive of OS in both the Plin/Doc and Doc arms (p values ranging from 0.05 to 0.0001). Plin prevents Doc-induced neutropenia, and post-Doc neutrophil counts were higher on D8 with Plin/Doc vs Plin (p < 0.001). Despite Doc-induced myelosuppression, Plin/Doc responding pts maintained similar NLR/LMR values as baseline at C1D8 and C2D8. After a single Plin dose at C1D8, lower NLR (cutoff = 3.0; 1.2x median value of all pts) and higher LMR (cutoff = 4.5; median value of all pts) thresholds independently predicted PFS/OS benefits of Plin/Doc vs Doc. Further, a higher cNLR threshold (cutoff = 0.25) at C2D8, best predicted Plin/Doc vs Doc in PFS and OS (p < 0.0001 and p = 0.0035 respectively). Conclusions: Bone marrow suppression remains a common serious risk of classical/non-classical cancer drugs. Under these conditions, the addition of Plin offers rapid protection of GMP lineage cells which can be captured by simple blood cell counts. Incorporation of blood-based biomarkers may help enrich NSCLC pts with better sensitivity to Plin/Doc combination than Doc alone. Clinical trial information: NCT02504489.