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Background: Human lung cancer expresses high levels of PD-L1,which may inhibit anti-cancer immune responses.MPDL3280A,a human monoclonal Ab containing an engineered Fc-domain designed to optimize efficacy and safety,targets PD-L1,blocking PD-L1 from binding its receptors,including PD-1 and B7.1.Methods: Pts with squamous or nonsquamous NSCLC received MPDL3280A Ⅳ q3w at doses between 1-20 mg/kg in a Ph I expansion study.Pts were treated for up to 1 y.Objective response rate(ORR)was assessed by RECIST v1.1.Reported ORR includes u/cCR and u/cPR.Results: As of Jan 10,2013,53 NSCLC pts were evaluable for safety and treated at doses of ≤1(n=2),10(n=10),15(n=19)and 20 mg/kg(n=22).Pts had a median age of 61 y(range 24-83 y),98%were PS 0-1,89%had prior surgery and 55%had prior radiotherapy.98%of pts received prior systemic therapy.Pts received treatment for a median duration of 106 days(range 1-324)of MPDL3280A.The incidence of all G3/4 AEs,regardless of attribution,was 34%,including pericardial effusion(6%),dehydration(4%),dyspnea(4%)and fatigue(4%).No G3-5 pneumonitis or diarrhea was reported.37 NSCLC pts enrolled prior to Jul 1,2012,were evaluable for efficacy.RECIST responses were observed at dose levels between 1 and 20 mg/kg,with all responses ongoing or improving.An ORR of 24%(9/37)was observed in pts with squamous and nonsquamous histologies,including several with rapid tumor shrinkage.Additional pts had delayed responses after apparent radiographic progression(not included in the ORR).The 24-week PFS was 48%.Analysis of biomarker data from archival tumor samples demonstrated a correlation between PD-L1 status and efficacy.Pts who were PD-L1 tumor status–positive showed an ORR of 100%(4/4)and a PD rate of 0%(0/4),while pts who were PD-L1 tumor status–negative showed an ORR of 15%(4/26)and a PD rate of 58%(15/26).Updated data will be presented.Conclusions: Treatment with MPDL3280A was well tolerated,with no pneumonitis-related deaths.Rapid and durable responses were observed.PD-L1 tumor status correlated with response to MPDL3280A.