The ectodomain of the SARS-CoV-2 S glycoprotein encodes the N-terminal S1 subunit, including the receptor binding domain, and, the C-terminal S2 subunit. The junction connecting S1 with S2 contains the furin cleavage site at position R682-R685 (RRAR). Recent structural studies on the SARS-CoV-2 Spike protein showed that this part of the protein is solvent-exposed and disordered. The SARS-CoV-2 Furin Cleavage Site Control-Biotin peptide covers amino acids S673-S691 of the SARS-CoV-2 Spike glycoprotein and encodes for a mutated Furin cleavage site (RRAR to GSAS substitution at residues 682–685). SARS-CoV-2 Furin Cleavage Site Control-Biotin is specifically biotinylated at the C terminus.