660. Early Experience with Use of Pemivibart for the Pre-exposure Prophylaxis of Coronavirus Disease 2019

Abstract Background Pemivibart is an investigational monoclonal antibody that is available for emergency use by the U.S. FDA since March 2024 under an emergency use authorization (EUA) for the pre-exposure prophylaxis of COVID-19 in adults and adolescents. Pemivibart is administered every 3 months to patients who have moderate-to-severe immune compromise due to certain medical conditions or receipt of certain immunosuppressive medications or treatments and who are unlikely to mount an adequate immune response to COVID-19 vaccination. The purpose of this study is to report early use of pemivibart.Table 1.Demographics and Treatment Characteristics Methods A retrospective, cohort study was conducted in Infectious Disease and ambulatory infusion centers in patients who received ≥ 1 dose of pemivibart for the pre-exposure prophylaxis of COVID-19. Data collected included demographics, medical history, immune compromised reason for use, treatment details, and adverse events. Results Overall, 42 pts received pemivibart following EUA approval from May 2024 through April 2025. Patient and treatment characteristics are shown in Table 1.Median age was 68 years (IQR 56-73). The most prevalent reason for use of pemivibart was active treatment with immunosuppressive medications (n=29, 69%), followed by moderate or severe immune compromise (n=13, 31%). A total of 29 (69%) patients were previously vaccinated for COVID-19, and 11 (26%) had previous episodes of COVID-19 infection. The pemivibart dose was 4500mg in all infusions with 97 infusions administered to date. Pre-medications were administered in 50 (52%) infusions, primarily acetaminophen and diphenhydramine. The majority (97%) of patients were observed for 2 hours following infusions. Of the 42 patients, 37 remain on therapy. Two patients (5%) experienced adverse events, including one with tachycardia and shortness of breath and one with headache. Reasons for discontinuation are noted in Table 1. No COVID-19 infections have been reported in the patients on pemivibart therapy. Conclusion Pemivibart has been safely administered in a varied immunocompromised population. Although this is a small cohort, COVID-19 infections have not occurred since initiation of pemivibart. Additional study will be warranted to confirm the continued effectiveness of pemivibart in prevention of COVID-19. Disclosures Kimberly A. Couch, PharmD, MA, FIDSA, FASHP, Healix: wages