Engineered cytokines and uses thereof

A composition comprising:

• an engineered IL-21 cytokine or a functional fragment thereof, that is a variant of a wild type IL-21 cytokine having amino acid residues of SEQ ID NO:
• 1,
• wherein the engineered IL-21 cytokine or a functional fragment thereof comprises at least one amino acid substitution in a region comprising amino acid residues 30 to 135 of SEQ ID NO:
• 1,
• wherein the at least one amino acid substitution in a region comprising amino acid residues 30-135 of SEQ ID NO:
• 1 is at position R34 or P107,
• wherein the at least one amino acid substitution provides for an increased stability of the engineered IL-21 cytokine compared to the wild type IL-21 cytokine, and
• wherein the increased stability is characterized by an increased thermal stability of the engineered IL-21 cytokine compared to that of the wild type IL-21 cytokine when measured in a 75 ug/mL sample using a differential scanning fluorimetry (DSF) spectroscopic method to detect thermal melting measurements by performing a thermal ramp with a 1 degree Celsius/minute heating rate from 20 degrees Celsius to 95 degrees Celsius and measuring backscattered light intensity to detect heat induced aggregation.