Application and Advantages:
As Therapeutic Agents
Antibody fragments often have better tissue penetration due to their smaller sizes and the absence of Fc-mediated receptor binding. For the treatment of solid tumors, deep tissue penetration is an important factor in determining the efficacy of an antibody drug. Also, for antibody drugs that do not target directly to tumor cells (e.g. Avastin is targeting VEGF), removing Fc may reduce the side effect due to the interactions between Fc with cellular proteins.
As Imaging and Diagnostic Agents
Comparing to full-length antibodies, antibody fragments have better tissue penetration and faster body clearance, which are two important factors for imaging agents. Also, as diagnostic agents, antibody fragments often give lower background due to the absence of the serum anti-Fc antibody interaction with Fc.
As Antibody-Drug Conjugate (ADC)
The use of Antibody fragment in ADC offers several advantages: The faster clearance from the body can reduce the cytotoxicity of ADC; The deeper tissue penetration may improve better efficacy; The free Cys residues in Fab molecules can enable site-specific linkage of cytotoxic payload to antibody molecules.