Dual specificity antibody fusions

A dual specificity antibody fusion protein comprising an antibody Fab fragment or an antibody Fab′ fragment with specificity for an antigen of interest, said fragment being fused to two single domain antibodies that have specificity for serum albumin, wherein one single domain antibody is fused to the C-terminus of the light chain of the Fab fragment or the Fab′ fragment and the other single domain antibody is fused to the C-terminus of the heavy chain of the Fab fragment or the Fab′ fragment, and wherein one single domain antibody is a VH domain comprising the sequence given in SEQ ID NO:

• 62 for CDR-H1, the sequence given in SEQ ID NO:
• 63 for CDR-H2 and the sequence given in SEQ ID NO:
• 64 for CDR-H3, and the other single domain antibody is a VL domain comprising the sequence given in SEQ ID NO:
• 65 for CDR-L1, the sequence given in SEQ ID NO:
• 66 for CDR-L2 and the sequence given in SEQ ID NO:
• 67 for CDR-L3, wherein the VH domain is fused to the C-terminus of the heavy chain of the Fab fragment or the Fab′ fragment and the VL domain is fused to the C-terminus of the light chain of the Fab fragment or the Fab′ fragment.