Cost-Effectiveness of Imipenem/Cilastatin/Relebactam Compared with Colistin in Treatment of Gram-Negative Infections Caused by Carbapenem-Non-Susceptible Organisms

Introduction Imipenem/cilastatin/relebactam (IMI/REL), a combination β-lactam antibiotic (imipenem) with a novel β-lactamase inhibitor (relebactam), is an efficacious and well-tolerated option for the treatment of hospitalized patients with gram-negative (GN) bacterial infections caused by carbapenem-non-susceptible (CNS) pathogens. This study examines cost-effectiveness of IMI/REL vs. colistin plus imipenem (CMS + IMI) for the treatment of infection(s) caused by confirmed CNS pathogens. Methods We developed an economic model comprised of a decision-tree depicting initial hospitalization, and a Markov model projecting long-term health and economic impacts following discharge. The decision tree, informed by clinical data from RESTORE-IMI 1 trial, modeled clinical outcomes (mortality, cure rate, and adverse events including nephrotoxicity) in the two comparison scenarios of IMI/REL versus CMS + IMI for patients with CNS GN infection. Subsequently, a Markov model translated these hospitalization stage outcomes (i.e., death or uncured infection) to long-term consequences such as quality-adjusted life years (QALYs). Sensitivity analyses were conducted to test the model robustness. Results IMI/REL compared to CMS + IMI demonstrated a higher cure rate (79.0% vs. 52.0%), lower mortality (15.2% vs. 39.0%), and reduced nephrotoxicity (14.6% vs. 56.4%). On average a patient treated with IMI/REL vs. CMS + IMI gained additional 3.7 QALYs over a lifetime. Higher drug acquisition costs for IMI/REL were offset by shorter hospital length of stay and lower AE-related costs, which result in net savings of $11,015 per patient. Sensitivity analyses suggested that IMI/REL has a high likelihood (greater than 95%) of being cost-effective at a US willingness-to-pay threshold of $100,000–150,000 per QALY. Conclusions For patients with confirmed CNS GN infection, IMI/REL could yield favorable clinical outcomes and may be cost-saving—as the higher IMI/REL drug acquisition cost is offset by reduced nephrotoxicity-related cost—for the US payer compared to CMS + IMI.