CoVac501, a self-adjuvanting peptide vaccine conjugated with TLR7 agonists, against SARS-CoV-2 induces protective immunity.

Safe, effective, and economical vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are needed to achieve adequate herd immunity and end the pandemic. We constructed a novel SARS-CoV-2 vaccine, CoVac501, which is a self-adjuvanting peptide vaccine conjugated with Toll-like receptor 7 (TLR7) agonists. The vaccine contains immunodominant peptides screened from the receptor-binding domain (RBD) and is fully chemically synthesized. It has been formulated in an optimized nanoemulsion formulation and is stable at 40 °C for 1 month. In non-human primates (NHPs), CoVac501 elicited high and persistent titers of protective neutralizing antibodies against multiple RBD mutations, SARS-CoV-2 original strain, and variants (B.1.1.7 and B.1.617.2). Specific peptides booster immunization against the B.1.351 variant has also been shown to be effective in improving protection against B.1.351. Meanwhile, CoVac501 elicited the increase of memory T cells, antigen-specific CD8+ T-cell responses, and Th1-biased CD4+ T-cell immune responses in NHPs. Notably, at an extremely high SARS-CoV-2 challenge dose of 1 × 107 TCID50, CoVac501 provided near-complete protection for the upper and lower respiratory tracts of cynomolgus macaques.

Safety, tolerability, pharmacokinetic characteristics, and immunogenicity of MW33: a Phase 1 clinical study of the SARS-CoV-2 RBD-targeting monoclonal antibody.

MW33 is a fully humanized IgG1κ monoclonal neutralizing antibody, and may be used for the prevention and treatment of coronavirus disease 2019 (COVID-19). We conducted a randomized, double-blind, placebo-controlled, single-dose, dose-escalation Phase 1 study to evaluate the safety, tolerability, pharmacokinetics (PK), and immunogenicity of MW33. Healthy adults aged 18-45 years were sequentially enrolled into the 4, 10, 20, 40, and 60 mg/kg dose groups and infused with MW33 over 60 ± 15 min and followed for 85 days. All 42 enrolled participants completed the MW33 infusion, and 40 participants completed the 85-day follow-up period. 34 participants received a single infusion of 4 (n = 2), 10 (n = 8), 20 (n = 8), 40 (n = 8), and 60 mg/kg (n = 8) of MW33. 27 subjects in the test groups experienced 78 adverse events (AEs) post-dose, with an incidence of 79.4% (27/34). The most common AEs included abnormal laboratory test results, vascular and lymphatic disorders, and infectious diseases. The severity of AEs was mainly Grade 1 (92 AEs), and three Grade 2 and one Grade 4. The main PK parameters, maximum concentration (Cmax), and area under the concentration-time curve (AUC0-t, and AUC0-∞) in 34 subjects showed a linear kinetic relationship in the range of 10-60 mg/kg. The plasma half-life was approximately 25 days. The positive rates of serum ADAs and antibody titres were low with no evidence of an impact on safety or PK. In conclusion, MW33 was well-tolerated, demonstrated linear PK, with a lower positive rate of serum ADAs and antibody titres in healthy subjects.Trial registration: ClinicalTrials.gov identifier: NCT04427501.Trial registration: ClinicalTrials.gov identifier: NCT04533048.Trial registration: ClinicalTrials.gov identifier: NCT04627584.

Characterization of neutralizing antibody with prophylactic and therapeutic efficacy against SARS-CoV-2 in rhesus monkeys.

Efficacious interventions are urgently needed for the treatment of COVID-19. Here, we report a monoclonal antibody (mAb), MW05, with SARS-CoV-2 neutralizing activity by disrupting the interaction of receptor binding domain (RBD) with angiotensin-converting enzyme 2 (ACE2) receptor. Crosslinking of Fc with FcγRIIB mediates antibody-dependent enhancement (ADE) activity by MW05. This activity is eliminated by introducing the LALA mutation to the Fc region (MW05/LALA). Potent prophylactic and therapeutic effects against SARS-CoV-2 are observed in rhesus monkeys. A single dose of MW05/LALA blocks infection of SARS-CoV-2 in prophylactic treatment and clears SARS-CoV-2 in three days in a therapeutic treatment setting. These results pave the way for the development of MW05/LALA as an antiviral strategy for COVID-19.