Table 2.
Representative SARS-CoV-2-targeting therapeutic nanobodies
| Nanobody name | Target | Binding affinity and mechanism | Structure | Neutralizing activity | Protection and/or pharmacokinetics (PK) | Ref. |
|---|---|---|---|---|---|---|
|
| ||||||
| 1E2 4D8 2F2 3F11 5F8 |
RBD | Bound to RBD (EC50 0.996–35.52 nM), blocking the RBD-ACE2 binding | No | Neutralized pseudotyped (IC50 0.9–69 ng ml−1) and live (IC50 0.13–0.51 μg ml−1) SARS-CoV-2 infection | N/A | 156 |
| Ty1 Ty1-Fc |
RBD | Bound to RBD (Kd 5–10 nM), preventing the RBD-ACE2 binding | Yes, cryo-EM structure (for Ty1) | Neutralized pseudotyped (IC50 0.77 μg ml−1 for Ty1; IC50 0.012 μg ml−1 for Ty1- Fc) SARS-CoV-2 infection | N/A | 67 |
| Sb23 | RBD | Bound to RBD, competing its binding with ACE2 | Yes, crystal structure | Neutralized pseudotyped (IC50 0.6 μg ml−1) SARS-CoV-2 infection | N/A | 70 |
| H11-D4 H11-H4 H11-D4-Fc H11-H4-Fc |
RBD | Bound to RBD (Kd 39 and 12 nM for H11-D4 and h11-H4), blocking the RBD-ACE2 interaction | Yes, crystal and cryo-EM structures (for H11-D4 and H11-H4) | Neutralized live (IC50 4–6 nM for H11-H4-Fc; 18 nM for H11-D4-Fc) SARS-CoV-2 infection | N/A | 155 |
| Nb20 Nb21 Nb89 Nb203 Nb213 |
RBD | Nbs 20 and 21 bound to RBD (Kd < 1 pM), overlapping with the ACE2 binding site | Yes, crystal structure (for Nb20) | Neutralized pseudotyped (IC50 0.045–0.133 nM) and live (IC50 0.022–0.154 nM) SARS-CoV-2 infection, with multimeric Nbs improving neutralizing activity against infection of pseudotyped (IC50 1.3–4.1 pM) and live SARS-CoV-2 | N/A | 68 |
| Nb3 Nb6 Nb11 mNb6 Nb3-tri Nb6-tri Nb11-tri mNb6-tri PiN-21 |
RBD | Bound to RBD by inhibiting the RBD-ACE2 interaction (via blocking the binding site or locking the RBD into an inactive conformation) | Yes, crystal (for mNb6) and cryo- EM (for Nb6, Nb11, and mNb6) structures | Neutralized pseudotyped (IC50 2.0–3.9 μM) SARS-CoV-2 infection, with trimeric or matured Nbs enhancing neutralizing activity against infection of pseudotyped (IC50 1.2–400 nM for tri-Nbs; 0.12 nM for mNb6-tri) and live (IC50 0.16–140 nM for tri-Nbs; 0.054 nM for mNb6-tri) SARS-CoV-2 | Prophylactically and therapeutically prevented hamsters from SARS-CoV-2 infection; inhalation treatment inhibited weight loss, with decreased lung viral titers and lung pathology | 69 and 159 |
| C1 H3 C5 C1-trimer H3-trimer C5-trimer C5-Fc |
RBD | Bound to WT or variant RBD (Kd 0.0003–2.523 nM) by overlapping with the ACE2 epitope (for H3 and C5) or a different epitope (for C1) | Yes, crystal (for C1, H3, and C5) and cryo-EM (for C5) structures | Neutralized (IC50 0.025–8.2 nM) infection of SARS-CoV-2 variants (B.1.1.7 or B.1.351) (for C1-trimer, C5-trimer, or H3-trimer) | C5-trimer or C5-Fc therapeutically prevented hamsters from SARS-CoV-2 infection | 158 |
| Nanosota-I Nanosota-IC Nanosota-IC-Fc |
RBD | Bound to RBD (Kd 15.7 pg for Nanosota-1C-Fc), blocking the RBD-ACE2 binding | Yes, crystal structure (for Nanosota-1C) | Nanosota-IC-Fc inhibited infection of pseudotyped and/or live (ND50 0.16 μg ml−1) SARS-CoV-2 and variant (D614G) | Nanosota-IC-Fc prophylactically and therapeutically inhibited hamsters and hACE2-Tg mice from SARS-CoV-2 infection; >10-day half-life and high tissue bioavailability | 63 |
| K-874A | S1 (RBD-NTD) | Bound to S1 region (Kd 1.4 nM) between RBD and NTD of S protein | Cryo-EM structure | Blocked viral membrane fusion, neutralizing SARS-CoV-2 B.1.1.7 variant | Therapeutically protected hamsters from SARS-CoV-2 infection | 157 |
ACE2, angiotensin-converting enzyme 2; Cryo-EM: cryo-electron microscopy; EC50, half maximal effective concentration; hACE2-Tg, human ACE2-transgenic; IC50, half maximal inhibitory concentration; ND50, 50% neutralization dose; Kd, equilibrium dissociation constant; Nbs, nanobodies; RBD, receptor-binding domain; WT, wild-type.