The present invention relates to a modified protein that is a combination of (i) an L-asparaginase and (ii) one or more (poly)peptide(s), wherein the (poly)peptide consists solely of proline and alanine amino acid residues. The modified protein can be formed in a number of ways, including chemical conjugation between the L-asparaginase and the (poly)peptides or by expressing the modified protein as a fusion protein. Also provided herein are nucleic acids encoding the modified protein, vectors and/or host cells comprising same, as well as processes for their production. Compositions comprising the modified protein and their use in medicine, particularly in the treatment of cancer, are disclosed. In another aspect of the invention, the L-asparaginase can be derived from