Blocking the association between the severe acute respiratory syndrome coronavirus 2
(SARS-CoV-2) spike protein receptor-binding domain (RBD) and the human
angiotensin-converting enzyme 2 (ACE2) is an attractive therapeutic approach to prevent
the virus from entering human cells. While antibodies and other modalities have been
developed to this end,
d
-amino acid peptides offer unique advantages, including
serum stability, low immunogenicity, and low cost of production. Here, we designed
potent novel D-peptide inhibitors that mimic the ACE2 α1-binding helix by
searching a mirror-image version of the PDB. The two best designs bound the RBD with
affinities of 29 and 31 nM and blocked the infection of Vero cells by SARS-CoV-2 with
IC
50
values of 5.76 and 6.56 μM, respectively. Notably, both
D-peptides neutralized with a similar potency the infection of two variants of concern:
B.1.1.7 and B.1.351
in vitro
. These potent D-peptide inhibitors are
promising lead candidates for developing SARS-CoV-2 prophylactic or therapeutic
treatments.