Associate Professor and Director of Lymphoid Malignancies Program at UTSW The University of Texas Southwestern Dallas, Texas, United States
Background: Patients with hematologic malignancies are at significantly higher risk for severe COVID-19 due to disease-related and treatment-induced immunosuppression. Despite widespread vaccine availability, many patients fail to mount effective immune responses. On March 22, 2024, the FDA issued Emergency Use Authorization for pemivibart (Pemgarda™), a long-acting monoclonal antibody for pre-exposure prophylaxis in individuals with moderate-to-severe immunocompromise. While initial approval was based on laboratory and pharmacokinetic data, real-world evidence on Pemivibart’s safety and effectiveness in high-risk populations remains limited. This study evaluates adverse reactions and breakthrough infections following Pemivibart use in immunocompromised patients with hematologic malignancies.
Methods: We analyzed 112 adult patients with lymphoid malignancies who received Pemivibart between March 2024 and May 2025. Clinical data included age, sex, vaccine history, adverse reactions, and incidence of COVID-19 infection after Pemivibart. COVID-19 infection was confirmed through antigen or PCR testing. Descriptive statistics summarized the cohort.
Results: All patients had lymphoid malignancies (CLL, n=69 (62% of the cohort)) at various disease and treatment course points. The mean age was 69.6 years; 48.2% were female. The average number of prior COVID-19 vaccine doses was four, and 34 patients (30.4%) received a second Pemivibart dose. Adverse reactions occurred in 6.3% (7/112), including grade 3 anaphylaxis in one (0.9%) patient that resolved with supportive care, and grade 2 infusion-related reactions in two (1.8%) patients, all of which responded well to supportive care. Three patients (2.7%) developed COVID-19 after Pemivibart administration. Of these, two required hospitalizations: one had no history of vaccination or prior pre-exposure prophylaxis; the other had received two vaccine doses without prior pre-exposure prophylaxis. The third patient, who had three vaccine doses and prior pre-exposure prophylaxis, experienced mild symptoms and recovered with supportive care. No COVID-19-related deaths were reported.
Conclusion: Pemivibart was well-tolerated in immunocompromised patients with lymphoid malignancies, with a low incidence of adverse reactions and breakthrough infections. Hospitalizations occurred only in those with minimal prior immunologic protection, highlighting the continued importance of layered COVID-19 prevention strategies. These real-world findings support using Pemivibart as an adjunct to vaccination in high-risk populations and underscore the need for pre-exposure prophylaxis, especially in patients with a compromised ability to generate adequate vaccine-mediated immunity. Detailed data will be provided at the conference.
