PROS1 and neoplasm: For example, covalent aptamers targeting the S-protein and the RBD domain of SARS-CoV-2 were developed and showed increased detection sensitivity and enhanced virus neutralization compared to their non-covalent analogs.57,127 Moreover, aptamer crosslinking or transfer of ligands has been utilized for targeted protein degradation, leading to cancer cell killing and a reduction of tumor burden in mouse xenografts.143,155