Pemivibart is less active against recent SARS-CoV-2 JN.1 sublineages

Protection from COVID-19 vaccination is suboptimal in many immunocompromised individuals. In March 2024, the Food and Drug Administration issued an Emergency Use Authorization for pemivibart (Permagard/VYD222), an engineered human monoclonal antibody, for pre-exposure prophylaxis in this vulnerable population. However, SARS-CoV-2 has since evolved extensively, resulting in multiple Omicron JN.1 sublineages. We therefore evaluated the in vitro neutralizing activity of pemivibart against the prevalent forms of JN.1, including KP.2, KP.3, KP.2.3, LB.1, and, importantly, KP.3.1.1, which is now expanding most rapidly. A panel of VSV-based pseudoviruses representing major JN.1 sublineages was generated to assess their susceptibility to pemivibart neutralization in vitro. Structural analyses were then conducted to understand the impact of specific spike mutations on the virus-neutralization results. Pemivibart neutralized both JN.1 and KP.2 in vitro with comparable activity, whereas its potency was decreased slightly against LB.1, KP.2.3, and KP.3 but substantially against KP.3.1.1. Critically, the 50% inhibitory concentration of pemivibart against KP.3.1.1 was [~]6 {micro}g/mL, or [~]32.7 fold higher than that of JN.1 in our study. Structural analyses suggest that Q493E and the S31-deletion mutations in viral spike contribute to the antibody evasion, with the latter having a more pronounced effect. Our findings show that pemivibart has lost substantial neutralizing activity in vitro against KP.3.1.1, the most rapidly expanding lineage of SARS-CoV-2 today. Close monitoring of its clinical efficacy is therefore warranted. These results also highlight the imperative to expand our arsenal of preventive agents to protect millions of immunocompromised individuals who could not respond robustly to COVID-19 vaccines.