Background: Belagenpumatucel-L (Lucanix) is a therapeutic vaccine comprised of 4 TGF-β2 antisense gene-modified, irradiated, allogeneic NSCLC cell lines. Methods: The trial enrolled patients (pts) without progression after completion of frontline chemotherapy (IIIA-42, IIIB/IV-490). Pts were randomized 1:1 between 4 and 17.4 weeks (w) from the end of frontline chemotherapy. Pts were treated until disease progression or withdrawal. The primary endpoint was overall survival (OS). Secondary endpoints were PFS, RR and safety. Results: 532 pts were enrolled (270 vaccine and 262 placebo), 57% adenocarcinoma (non-SCC), 27% squamous (SCC). Median OS results and safety profile of belagenpumatucel-L was previously reported. A predefined Cox regression demonstrated that the time elapsed between the end of frontline chemotherapy and randomization had a significant impact on survival outcomes (p=0.002). 318 (59.8%) of pts were randomized within 12 w of the completion of chemotherapy (IIIA=13, IIIB/IV=305, 162 vaccine, 143 placebo). Pts with pretreatment radiation (XRT) enrolled within 12 w had median OS of 40.1 m (belagenpumatucel-L) vs. 10.3 m (placebo) (HR 0.45, p=0.014). Median OS of pts treated with concurrent XRT and enrolled within 12 w was not reached (belagenpumatucel-L) and 10.3 m (placebo) (HR 0.34, p=0.04). Conclusions: Although,trial did not meet its predefined end point, a non-statistically significant increase in OS was observed in several subsets of pts who began belagenpumatucel-L within 12 w of the completion of frontline chemotherapy. These data support another Phase III trial with IIIB/IV patients to be randomized within 12 weeks of the completion of frontline chemotherapy. Clinical trial information: 00676507.