Picomolar inhibition of SARS-CoV-2 variants of concern by an engineered ACE2-IgG4-Fc fusion protein

Abstract

SARS-CoV-2 enters host cells after binding through its spike glycoprotein to the angiotensin-converting enzyme 2 (ACE2) receptor. Soluble ACE2 ectodomains bind and neutralize the virus, yet their short in vivo half-live limits their therapeutic use. This limitation can be overcome by fusing the fragment crystallizable (Fc) part of human immunoglobulin G (IgG) to the ACE2 ectodomain, but this bears the risk of unwanted Fc-receptor activation and antibody-dependent disease enhancement. Here, we describe optimized ACE2-IgG4-Fc fusion constructs that avoid Fc-receptor activation, preserve the desired ACE-2 enzymatic activity and show promising pharmaceutical properties. The engineered ACE2-IgG4-Fc fusion proteins neutralize the original SARS-CoV, pandemic SARS-CoV-2 as well as the rapidly spreading SARS-CoV-2 variants-of-concern, B.1.17 and B.1.351. Importantly, these variants-of-concern are inhibited at picomolar concentrations proving that ACE-2-IgG4 maintains – in contrast to therapeutic antibodies - its full antiviral potential. Thus, ACE2-IgG4-Fc fusion proteins are promising candidate anti-antivirals to combat the current and future pandemics.

Multimeric ACE2-IgM fusions as broadly active antivirals that potently neutralize SARS-CoV-2 variants

“…Again, the hexameric ACE2-IgM-Fc exhibited very high neutralization efficiency illustrated by the IC50 value of 680 pM, while the monomeric ACE2-IgM-Fc had an IC50 of around 65 nM (Fig. 4f and Table 1), which was similar to a monomeric ACE2-IgG-Fc 8 . The ACE2-Cµ4 monomer was not able to fully neutralize SARS-CoV in concentrations up to 1000 nM (Fig.…”

“…A wildtype sequence of ACE2 was used in this study due to the better thermal stability of this domain compared to an ACE2 with two mutations to abolish its enzymatic activity 17 . However, we have previously shown that ACE2 domains with no enzymatic activity can also be used to obtain ACE2-Fc fusions with minimal impact on the production yields, structure, and virus neutralization properties 8 . We therefore envisage that our approach can be employed to obtain hexameric ACE2-IgM-Fc proteins with enzymatically-inactive ACE2.…”

“…However, mAbs are very specific and vulnerable to escape mutations in new virus variants [3][4][5] . An orthogonal approach to antibodies employs soluble forms of the viral receptor, the angiotensin-converting enzyme 2 (ACE2), that can be used to "trap" and neutralize all coronaviruses that use ACE2 as a primary receptor [6][7][8] . To increase avidity, different fusion partners of ACE2 have been employed, including the Fc parts of IgG antibodies or oligomerization motifs 6,[9][10][11][12] .…”

Comprehensive Evaluation of ACE2-Fc Combination with Neutralization Antibody on Broad Protection against SARS-CoV-2 and Its Variants

“…Our research studied the ACE2-Fc combination strategy with neutralizing antibodies of diverse epitopes. Taking advantage of the broad neutralizing ability of ACE2-Fc demonstrated by many previous researches 4;5 ;8-11, NAb+ACE2-Fc combinations mitigated virus evasion by ACE2-Fc and NAb co-inhibiting the interaction of escaped variants with ACE2 receptor, which broadened the neutralization spectrum of individual NAbs of diverse epitopes, expanding the finding in ACE2-Fc and HLX70 combination 16 .…”

“…They confirmed the ability of the ACE2-Fc to neutralize SARS-CoV-2 pseudovirus and conducted pharmacokinetics studies to demonstrate 5.2 days half-life, sufficient long-lasting bioavailability to justify clinical applications 2;3 . Further, the neutralization by ACE2 decoy receptor was confirmed against authentic virus [4][5][6][7][8][9] and showed promising prophylactic and therapeutic efficacy in animal models 8 .…”