Neutralizing antibodies to SARS-CoV-2 develop as part of the natural immune response and during the course of infection. The main neutralizing mechanism identified thus far for these antibodies consists on the blockade of the interaction between the viral spike protein and its cellular receptor ACE2. Therefore, monoclonal antibodies designed to bind specifically and with high affinity to spike receptor binding domains (RBDs), have gathered much attention for their therapeutic potential.
Recombinant monoclonal antibodies may provide an alternative for COVID prophylaxis and treatment, while the world awaits for an effective and safe vaccine as the ultimate solution to the ongoing pandemic. Based on the Antibody Society's COVID-19 Biologicals Tracker, around 10 monoclonal antibodies entered clinical trials between May and August.
Among the candidates being tested, Regeneron's monoclonal antibody cocktail (REGN10933/ REGN10987) and Eli Lilly's monoclonal antibody (LY3819253), which target the Spike protein and neutralize viral ACE2 receptor binding, have progressed to Phase 3. Before the end of the year, around twelve new SARS-CoV-2 neutralizing monoclonal antibody candidates are anticipated to enter clinical studies. Expectations are high for these studies' outcomes, which may start to trickle in before fall.
Yet, the large and fast paced efforts to advance monoclonal antibody drugs trough clinical studies pale in comparison to those propelling vaccine candidates. To date, based on the RAPS' COVID-19 Vaccine Tracker, more than 40 vaccine candidates are at different stages of preclinical to clinical (Phase1-3) investigation.
| Vaccine Candidate | Immunogen Type | Clinical Phase |
|---|---|---|
| Inactivated vaccine | Inactivated whole-virus | 3 |
| CornaVac | Formalin-inactivated virus | 3 |
| mRNA-1273 | Transcript for perfusion-stabilized SARS-CoV-2 spike trimer | 3 |
| Ad5-nCoV | Replication-defective human type 5 adenovirus encoding SARS-CoV-2 spike protein | 3 |
| BCG | Bacillus Calmette-Guerin (BCG) live attenuated vaccine (Live-attenuated strain derived from Mycobacterium Bovis) | 2/3 |
| AZD1222/Covishield | Chimpanzee adeno-vector encoding codon-optimized full-length SARS-CoV-2 spike protein | 2/3 |
| BNT162b1 | Lipid nanoparticle-formulated nucleoside-modified mRNA vaccine encoding the RBD trimer of SARS-CoV-2 spike protein | 2/3 |
Monoclonal antibody drugs would clearly fill a void in COVID treatment, even after an effective vaccine is developed. This is true for sections of the population failing to respond robustly and appropriately to a vaccination schedule, the immunocompromised, and for those with pre-existent conditions making them vulnerable to critical illness, including but not limited to, cancer, COPD, chronic kidney disease, obesity, heart disease, and Type 2 diabetes.
Results from a new study available on the
preprint server medRxiv, provide further impetus for the therapeutic use of recombinant
monoclonal antibodies with neutralizing activity against SARS-CoV-2.
This new study documents findings from a SARS-CoV-2 outbreak with
“high attack rate”, above 85%, occurring on a Seattle
fishing vessel.
Out of 122 crew members, only 3 people remained without
illness. Importantly, these three individuals were seropositive,
with
anti-SARS-CoV-2 neutralizing antibodies, prior to the outbreak. Based on their findings, investigators
believe that this study may provide the "first direct evidence"
correlating the presence of neutralizing antibodies with protection
against SARS-CoV-2 in humans.
Previous success by Regeneron, in developing an effective recombinant monoclonal antibody therapy for Ebola, further supports this therapeutic strategy. Regeneron's REGN-EB3, consisting of a cocktail of three fully-human antibodies, was highly effective when given soon after Ebola infection leading to a ~90% survival rate.
