1460. Imipenem/Cilastatin (IMI)/Relebactam (REL) in Hospital-Acquired/Ventilator-Associated Bacterial Pneumonia (HABP/VABP): Subgroup Analyses of Critically Ill Patients in the RESTORE-IMI 2 Trial

Background HABP/VABP are serious infections associated with high mortality. Critically ill patients (pts) are at particularly high risk of adverse clinical outcomes. In the RESTORE-IMI 2 trial, IMI/REL was non-inferior to PIP/TAZ in primary and key secondary endpoints. We evaluated outcomes specifically in critically ill pts, according to several definitions, from that trial. Methods Randomized, controlled, double-blind, phase 3 trial in adult pts with HABP/VABP. Lower respiratory tract (LRT) specimens were obtained ≤48 hours prior to screening. Pts were randomized 1:1 to IMI/REL 500 mg/250 mg or PIP/TAZ 4 g/500 mg, given IV every 6 h for 7-14 d. The primary endpoint was Day 28 all-cause mortality (ACM) and the key secondary endpoint was clinical response at early follow-up (EFU; 7-14 d after completing therapy) in the modified intent-to-treat (MITT) population (randomized pts with ≥1 dose of study drug, excluding pts with only gram-positive cocci present on baseline Gram stain). This analysis assessed efficacy outcomes specifically in pts in the ICU and in pts with APACHE II score ≥15, both prespecified subgroups. In post-hoc analyses, outcomes were also specifically assessed in the subgroups of pts with moderate/severe renal impairment (creatinine clearance < 60 mL/min) and pts who received vasopressors. Results Of MITT pts (n=531) at baseline, 66.1% (175 IMI/REL, 176 PIP/TAZ) were in the ICU, 47.5% (125 IMI/REL, 127 PIP/TAZ) had APACHE-II score ≥15, and 24.7% (71 IMI/REL, 60 PIP/TAZ) had moderate/severe renal impairment. Further, 20.9% (54 IMI/REL, 57 PIP/TAZ) received vasopressors within 72 h of first dose of study drug and/or during the study. In each subgroup, baseline demographics, clinical characteristics, and causative LRT pathogens (mostly Enterobacterales, P. aeruginosa, and A. calcoaceticus-baumannii complex) were generally comparable between treatment arms. In pts with APACHE-II score ≥15, Day 28 ACM and clinical response rates with IMI/REL were favorable compared to PIP/TAZ (Table). Day 28 ACM was also favorable with IMI/REL in patients receiving vasopressors. Remaining outcomes were similar between treatment arms. Conclusion IMI/REL is an efficacious treatment option for critically ill pts with HABP/VABP. Table. Primary and key secondary efficacy outcomes by subgroup (MITT population) Disclosures Luke F. Chen, MBBS MPH MBA FRACP FSHEA FIDSA, Merck & Co., Inc. (Employee, Shareholder)Merck & Co., Inc. (Employee, Shareholder) Maria C. Losada, BA, Merck & Co., Inc. (Employee, Shareholder) Kathryn A. Mahoney, PharmD, Merck (Employee, Shareholder) Jiejun Du, PhD, Merck & Co., Inc. (Employee, Shareholder) Michelle L. Brown, BS, Merck & Co., Inc. (Employee, Shareholder) Robert Tipping, MS, Merck & Co., Inc. (Employee, Shareholder) Katherine Young, MS, Merck & Co., Inc. (Employee, Shareholder)Merck & Co., Inc. (Employee, Shareholder) C. Andrew DeRyke, PharmD, Merck & Co., Inc. (Employee, Shareholder) Joan R. Butterton, MD, Merck & Co., Inc. (Employee, Shareholder) Amanda Paschke, MD MSCE, Merck & Co., Inc. (Employee, Shareholder)