Background: LAG-3, an immune checkpoint receptor involved in T-cell regulation, is frequently co-expressed with PD-1. LAG-3 and PD-1 signaling contributes to immune cell exhaustion and reduces the immune response to tumor cells. Dual inhibition of PD-1 and LAG-3 may reactivate the T-cell response better than blockade of either individual pathway. Here, we report combined safety data from 4 trials investigating BI 754111, an anti-LAG-3 mAb, in combination with BI 754091, an anti-PD-1 mAb, in patients with advanced solid tumors. Methods: Data from 2 phase I dose-escalation/expansion trials, 1 phase I imaging trial, and 1 phase II trial were included. Eligible patients had advanced and/or metastatic solid tumors with measurable disease and an Eastern Cooperative Oncology Group performance status ≤1. Patients received BI 754111 (intravenously [iv], 4–800 mg) in combination with BI 754091 (iv, 240 mg fixed dose) every 3 weeks (q3w). Patients remained on treatment until progressive disease or unacceptable toxicity. In each trial, safety was assessed by incidence and severity of adverse events (AEs), and graded according to Common Terminology Criteria for AEs, version 5. Results: Overall, 321 patients were treated with BI 754111 in combination with BI 754091 (200 [62%] male; median age, 63 years [range 18–88]). Median treatment exposure was 85 days (range 9–625). Of these patients, 282 (87.9%) had any AE (G≥3 in 99 [30.8%]). 285 patients received the 600 mg recommended phase II dose of BI 754111 plus BI 754091 240 mg q3w. Median treatment exposure in these patients was 74 days (range, 8–590). The table shows the 3 most common AEs and 4 most common immune-related AEs, and their frequency. 21 (7.4%) patients had AEs leading to study drug discontinuation, most commonly infusion-related reactions (IRRs) in 6 (2.1%) patients. Serious AEs (all-cause) occurred in 77 patients (27.0%), most commonly pleural effusion in 6 (2.1%) and deep vein thrombosis in 4 (1.4%) patients. 2 patients (0.7%) experienced an AE resulting in death (cardiac tamponade and acute kidney injury, both related to underlying diseases). Conclusions: The combination of BI 754111 and BI 754091 had a manageable safety profile, similar to other checkpoint inhibitors. Clinical trial information: NCT03156114, NCT03433898, NCT03697304, NCT03780725.