Impassion130: Updated Overall Survival (Os) From A Global, Randomized, Double-Blind, Placebo-Controlled, Phase Iii Study Of Atezolizumab (Atezo) Plus Nab-Paclitaxel (Np) In Previously Untreated Locally Advanced Or Metastatic Triple-Negative Breast Cancer (Mtnbc).

1003 Background: IMpassion130 evaluated atezo (anti–PD-L1) + nP vs placebo + nP in 1L mTNBC. The primary PFS analysis found that atezo + nP significantly improved PFS in intent-to-treat (ITT) and PD-L1+ pts vs placebo + nP, with efficacy driven by the PD-L1+ population. At that time, the 1st interim OS analysis was conducted (Schmid, NEJM 2018). Here we report the 2nd interim OS analysis. Methods: Eligible pts had histologically documented locally advanced or mTNBC, ECOG PS 0-1 and tumor tissue for PD-L1 testing. Pts were randomized 1:1 to IV atezo 840 mg or placebo on d1 and d15 + nP 100 mg/m2 on d1, d8 and d15 of each 28-d cycle until progression (stratification factors: prior taxanes, liver metastases, PD-L1 on tumor-infiltrating immune cells [IC]). RECIST 1.1 PFS (in ITT and PD-L1+ pts) and OS (tested in ITT and, if significant, PD-L1+ pts) were co-primary endpoints. Results: OS data are shown (Table). As of data cutoff (Jan 2, 2019), 9% of pts in the atezo + nP arm and 3% in the placebo + nP arm were still on treatment. Statistical significance was not demonstrated in ITT pts, but a 7.0-month improvement in median OS was observed in PD-L1+ pts with atezo + nP (25.0 mo) vs placebo + nP (18.0 mo; HR, 0.71 [95% CI: 0.54, 0.93]). A 4.5-mo safety update (Schneeweiss, ASCO 2019, submitted) showed that atezo + nP remained tolerable. Conclusions: The 2nd IMpassion130 interim OS analysis was consistent with the 1st analysis, confirming clinically meaningful OS benefit with atezo + nP in previously untreated PD-L1+ mTNBC. Clinical trial information: NCT02425891. [Table: see text]