Optimized anti-CD3 arm in the generation of t-cell bispecific antibodies for immunotherapy

A CD3 antigen binding fragment, comprising a heavy chain variable region and a light chain variable region, wherein:

• the heavy chain variable region has the amino acid sequence of SEQ ID NO:
• 15 and the light chain variable region has the amino acid sequence of SEQ ID NO:
• 2;
• or
• the heavy chain variable region has the amino acid sequence of SEQ ID NO:
• 22 and the light chain variable region has the amino acid sequence of SEQ ID NO:
• 2;
• or
• the heavy chain variable region has the amino acid sequence of SEQ ID NO:
• 23 and the light chain variable region has the amino acid sequence of SEQ ID NO:
• 2;
• or
• the heavy chain variable region has the amino acid sequence of SEQ ID NO:
• 24 and the light chain variable region has the amino acid sequence of SEQ ID NO:
• 2;
• or
• the heavy chain variable region has the amino acid sequence of SEQ ID NO:
• 25 and the light chain variable region has the amino acid sequence of SEQ ID NO:
• 2;
• or
• the heavy chain variable region has the amino acid sequence of SEQ ID NO:
• 26 and the light chain variable region has the amino acid sequence of SEQ ID NO:
• 4.