LBA43ANTITUMOR ACTIVITY OF PEMBROLIZUMAB (PEMBRO; MK-3475) AND CORRELATION WITH PROGRAMMED DEATH LIGAND 1 (PD-L1) EXPRESSION IN A POOLED ANALYSIS OF PATIENTS (PTS) WITH ADVANCED NON–SMALL CELL LUNG CARCINOMA (NSCLC)

ABSTRACT Aim: The anti-PD-1 antibody pembro has shown durable antitumor activity and acceptable toxicity in treatment-naive and previously treated advanced NSCLC. Correlation between tumor PD-L1 expression and improved pembro antitumor activity has been observed. Methods: 282 pts with treatment-naive or previously treated advanced NSCLC enrolled in randomized and nonrandomized cohorts of the phase 1 KEYNOTE-001 study were analyzed. To inform enrollment, tumor PD-L1 expression was determined prospectively by a prototype IHC assay (PA) in all pts. Samples were independently reanalyzed using a clinical trial IHC assay (CTA). Pembro was given at 2 mg/kg every 3 weeks (Q3W), 10 mg/kg Q3W, or 10 mg/kg Q2W until progression, death, or unacceptable toxicity. Overall response rate (ORR) was assessed per RECIST v1.1 by central review and per immune-related response criteria (irRC) by investigator review. Results: Mature data are available for 262 pts (5.4-mo median follow-up). Grade 3–5 drug-related AEs occurred in 24 (9%) pts, most commonly pneumonitis (n = 5 [n = 3 grade 3, n = 2 grade 4]). ORR (RECIST/irRC) in pts with measurable disease at baseline was 21%/23% overall (26%/47% treatment naive, 20%/18% previously treated) and was similar in pts with squamous (18%/25%) and nonsquamous (23%/23%) histology. ORR was 33%/67% at 2 mg/kg Q3W (n = 6), 21%/22% at 10 mg/kg Q3W (n = 141), and 21%/22% at 10 mg/kg Q2W (n = 115). As assessed by the PA, ORR was 23%/25% in pts with ≥1% PD-L1 staining and 9%/13% in pts with no PD-L1 staining. Preliminary median PFS will be presented, as will data for an additional 20 previously treated pts who received pembro 2 mg/kg Q3W. To date, data for PD-L1 staining using the CTA are available for nearly one-half of pts. In these pts, ORR (RECIST/irRC) was 39%/47% in pts with strong PD-L1 expression (≥50% staining) and 16%/9% in pts with weak/negative PD-L1 expression. Conclusions: Pembro is tolerable and provides antitumor activity in treatment-naive or previously treated advanced NSCLC, regardless of dose/schedule. Pts with strong PD-L1 tumor expression may derive particular benefit from pembro. Disclosure: E.B. Garon: Corporate-sponsored research: Merck, Pfizer, Genentech, AstraZeneca, Novartis, Puma; L. Gandhi: Serves on advisory boards for Genentech/Roche and has received consulting fees from Merck; N. Rizvi: Has served on advisory boards for Bristol-Myers Squibb, Merck, Roche, and AstraZeneca; R. Hui: Has served on advisory boards for Merck; A. Patnaik: Has received research grants from Merck; J-C. Soria: Has served as consultant to Merck; M.A. Gubens: Has served as advisory board member, without compensation, for Celgene and Roche/Genentech, and has received research grants from Merck, Celgene, and MedImmune; S.S. Ramalingam: Has served on advisory boards for Genentech and AstraZeneca; G.M. Lubiniecki, J. Zhang and K. Emancipator: Is an employee of Merck & Co., Inc.; R.Z. Rutledge: Is an employee of and holds stock in Merck & Co., Inc. All other authors have declared no conflicts of interest.