Fibroblast binding agents and use thereof

A fibroblast activation protein (FAP) binding agent comprising a recombinant heavy-chain-only antibody (VHH) comprising three complementarity determining regions (CDR1, CDR2, and CDR3), wherein:

• (a) CDR1 comprises an amino acid sequence of SEQ ID NO:
• 95 or any one of SEQ ID NOS:
• 87 to 94 or SEQ ID NOS:
• 96 to 115;
• (b) CDR2 comprises an amino acid sequence of SEQ ID NO:
• 121 or any one of SEQ ID NOS:
• 116 to 120 or SEQ ID NOS:
• 122 to 144;
• and
• (c) CDR3 comprises an amino acid sequence of SEQ ID NO:
• 152 or any one of SEQ ID NOS:
• 145 to 151 or SEQ ID NOS:
• 153 to 175.