ACE2-PNA conjugates exploit viral endocytosis for targeted intracellular delivery and exhibit dual antiviral efficacy against SARS-CoV-2.

The COVID-19 pandemic and its protracted consequences underscore the urgent need for more effective antiviral strategies. Current antiviral strategies face a persistent challenge achieving sufficient viral suppression while minimizing off-target toxicity, particularly against such highly mutable viruses. Here, we describe a Receptor-Drug Conjugate (RDC) strategy, in which a therapeutic payload is covalently linked to a decoy receptor, enabling virus-triggered targeted intracellular delivery. Angiotensin-converting enzyme 2 (ACE2), as the essential receptor for SARS-CoV-2 entry, has been widely exploited for virus-neutralizing strategies. Targeting SARS-CoV-2 as a proof-of-concept, we conjugated peptide nucleic acids (PNAs) designed to target the viral ORF1ab region (±30 bp) to ACE2-Fc. The ACE2-PNA conjugate demonstrated superior inhibitory efficacy against multiple SARS-CoV-2 variants relative to ACE2-Fc alone. We confirmed that ACE2-PNA retains the extracellular neutralization activity of soluble ACE2, while being selectively internalized into virus-infected cells via virus-mediated endocytosis. Owing to its inherent protease resistance, the PNA component remains intact upon cytoplasmic entry and subsequently exerts antisense inhibitory activity against viral RNA. The mechanistic feasibility of ACE2-PNA was further validated in a mouse model. Collectively, RDC represents a novel virus-triggered targeted delivery platform that confers dual antiviral efficacy through extracellular virion neutralization and intracellular inhibition of viral replication. It has significant implications for reducing off-target toxicity and enhancing antiviral potency, and is furthermore readily adaptable to diverse viral pathogens and therapeutic payloads.