Strengths and weaknesses of aptamers in comparison with antibodies
| Criteria | Aptamers | Antibodies |
|---|---|---|
| Size | 5–15 kDa | 150–180 kDa |
| • Target accessibility | High | Low |
| • Minimal target size | 60 Da | 600 Da |
| • Tissue/tumor penetration | High | Low |
| • Clearance rate | Rapid | Slow |
| Basic composition | Nucleotides | Amino acids |
| • Resistance to harsh environment conditions (pH and temperature) | High | Low |
| • Shelf-life | Long | Limited |
| • Versatility to chemical | High | Limited |
| • Nuclease degradation | Sensitive; limited half-life in vivo (unmodified) | Resistant; long half-life in vivo |
| Therapeutic efficacy | ||
| • Affinity and specificity | KD, nano/pico | KD, nano/pico |
| • Immunogenicity | Low/none | High |
| • Modulation of target activity | Yes | Yes |
| • Fc-mediated effector | No | Yes |
| Discovery | ||
| • Time | In vitro SELEX, 2–8 weeks | In vivo biological process, 6 |
| Production | ||
| • Scale up | Easy | Hard |
| • Batch to batch variation | None | High |
KD values: dissociation constants