Background: IMpower110 evaluated atezo mono in PD-L1–selected, chemo-naive patients (pts) with nonsquamous (nsq) or squamous (sq) NSCLC. At the interim analysis, IMpower110 met its primary OS endpoint, with a statistically significant and clinically meaningful improvement for atezo vs chemo in TC3 or IC3 wild-type (EGFR/ALK-negative) pts. We report on the safety profile of atezo vs chemo in IMpower110. Methods: 572 pts with stage IV nsq or sq NSCLC, PD-L1 expression ≥ 1% on TC or IC and ECOG PS 0-1 were randomized 1:1 to receive atezo (1200 mg IV q3w) or chemo (4 or 6 21-day cycles). In the chemo arm, nsq pts received cisplatin (cis) 75 mg/m² or carboplatin (carbo) AUC 6 + pemetrexed (pem) 500 mg/m² IV q3w; sq pts received cis 75 mg/m² + gemcitabine (gem) 1250 mg/m² or carbo AUC 5 + gem 1000 mg/m² IV q3w. Safety was assessed in all treated pts (safety evaluable [SE] population [pop]), regardless of PD-L1 expression or EGFR/ALK status. AEs were summarized per MedDRA v22.0 and severity graded per NCI CTCAE v4.0. Immune-mediated AEs (imAEs) were defined per a sponsor-specified list of terms, regardless of whether the events led to systemic glucocorticoid, endocrine therapy, or other immunosuppressants use. Results: At data cutoff (Sep 10, 2018) within the ITT pop, treatment (tx) was ongoing in 90 (atezo: 31.6%) and 25 (chemo: 8.7%) pts, with 13.7 mo of follow-up. Within the SE pop (atezo: n = 286, chemo: n = 263), atezo pts had longer tx exposure (5.3 mo) vs chemo pts (pem, 3.5 mo; gem, 2.6 mo; carbo, 2.3 mo; cis, 2.1 mo). Atezo had a favorable safety profile vs chemo (table); safety data were consistent with data from a pooled atezo mono pop. imAEs occurred in 40.2% (atezo) and 16.7% (chemo) of pts and were Grade (Gr) 3-4 in 6.6% and 1.5%, respectively. Conclusions: Atezo was better tolerated than chemo and imAEs were generally low grade. Overall, the safety experience with atezo mono in IMpower110 was consistent with its known safety profile; no new safety signals were identified. Clinical trial information: NCT02409342

^a Pooled atezo mono-treated pts (cross indications and therapy lines).

^b Gr 3-4 AE/imAE: number of pts whose highest grades of AE/imAE are 3 or 4