A bifunctional aptamer-siRNA chimera targeting ACE2 for the inhibition of SARS-CoV-2 S pseudovirus entry and replication.

The relentless evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the emergence of immune-evasive variants underscore an urgent need for novel therapeutic strategies that are resilient to viral mutations. Targeting conserved host factors essential for viral entry represents a promising approach to overcome this challenge. Here, we report the development of a bifunctional therapeutic platform targeting the primary human receptor for SARS-CoV-2, angiotensin-converting enzyme 2 (ACE2). Using systematic evolution of ligands by exponential enrichment (SELEX), we isolate a high-affinity DNA aptamer, designated AA2, that binds to human ACE2 with a dissociation constant ( Kd) of 5.41 ± 1.23 nM. Molecular docking and competitive binding assays confirm that AA2 sterically hinders the interaction between the viral spike receptor-binding domain (RBD) and ACE2. Consequently, AA2 demonstrates potent neutralization of SARS-CoV-2 S pseudovirus entry into host cells. To achieve a synergistic antiviral effect, we engineer an aptamer-siRNA chimera (AsiC) by conjugating AA2 to a short interfering RNA (siRNA) targeting the GFP coding region of the pseudovirus genome. This AsiC construct significantly represses viral replication compared to aptamer or siRNA treatment alone, validating a dual mechanism of action that combines receptor blockade with targeted gene silencing. This study establishes a robust proof-of-concept for an ACE2-targeted AsiC, representing a new class of dual-function antiviral therapeutics with the potential to effectively combat current and future ACE2-dependent coronaviruses.