© 2016 This randomized phase 2 study demonstrated promising clinical synergism between pemetrexed and intercalated erlotinib in patients with unselected nonsquamous non–small-cell lung cancer (NSCLC) as second-line therapy. EGFR (epidermal growth factor receptor) genotyping by Sequenom multiplex oncogenotyping assay was feasible in 79% of eligible patients using tumor DNA from either archival specimens and/or plasma. Because patients with EGFR-mutant NSCLC respond well to EGFR tyrosine kinase inhibitor monotherapy alone or in combination with bevacizumab, the combination might merit further evaluation as second-line or maintenance therapy against new standards in patients with EGFR wild-type advanced NSCLC. Background Pharmacodynamic separation of pemetrexed and erlotinib avoids negative cellular interactions and results in antitumor synergy in erlotinib-resistant non–small-cell lung cancer (NSCLC) cells, independent of EGFR (epidermal growth factor receptor) genotype. Patients and Methods Patients with platinum-treated metastatic nonsquamous NSCLC were randomly assigned 1:2 to pemetrexed alone (500 mg/m2provided intravenously on day 1) or pemetrexed followed by erlotinib (150 mg provided orally once daily on days 2-17) every 21 days. EGFR genotype was centrally confirmed by Sequenom multiplex oncogenotyping assay. The primary end point was progression-free survival (PFS), which would be considered promising for future study if median PFS was ≥ 4.5 months. Results Of 83 patients enrolled, 79 were randomized to either pemetrexed alone (n = 27) or in combination (n = 52). Fifty-nine (79%) of 75 eligible patients had tumors with confirmed EGFR genotype: 7 with activating mutations and 52 wild type. Median PFS was 4.7 and 2.9 months in the combination and pemetrexed-alone groups, respectively. In patients with EGFR wild-type tumors, median PFS was 5.3 and 3.5 months in the combination and pemetrexed-alone groups, respectively. Objective response rate (29% vs. 10%, P = .17), 6-month PFS (45% vs. 29%, P = .26), and 12-month PFS (23% vs. 10%, P = .28) were all higher in the combination arm. Rash (67% vs. 26%, P = .0007) and diarrhea (44% vs. 11%, P = .003) were significantly more common in the combination arm. Conclusion In patients with unselected or EGFR wild-type advanced nonsquamous NSCLC, pharmacodynamic separation of pemetrexed and intercalated erlotinib had promising antitumor activity without new safety concerns. The combination merits further evaluation as maintenance or second-line therapy against new standards in patients with EGFR wild-type advanced NSCLC.