The disclosure relates to fusion proteins, methods of making fusion proteins, and methods of using fusion proteins, wherein the fusion proteins comprise a functional single-domain antibody (sdAb) or a functional variant thereof and a cytosine deaminase (CD) protein or a functional variant thereof, optionally connected via a peptide linker. The fusion proteins of the disclosure also have CD activity. The disclosure also relates to pharmaceutical compositions or formulations comprising such fusion proteins and pharmaceutically acceptable excipients, as well as medical uses of these fusion proteins.
