IL-2 mutant immunoconjugates

The invention relates to an immunoconjugate of an anti-PD1 antibody and an IL-2 mutant. The immunoconjugate comprises an interleukin 2 (IL-2) polypeptide mutant and an antibody or an antigen binding fragment which binds to PD1. Polynucleotides encoding the immunoconjugates, expression vectors, host cells, expression methods, and pharmaceutical compositions are also provided. The invention provides an application of the immunoconjugate in preparation of a medicine composition for treating or preventing cancer, and preferably, the cancer is cancer with low response to anti-PD1 treatment. The immunoconjugate of the anti-PD1 antibody and the IL-2 mutant, provided by the invention, has weakened affinity to an IL-2 receptor and reduced activation capability to cells for expressing the IL-2 receptor, effectively avoids specific activation of tumor T lymphocytes by IL-2 molecules, reduces toxic and side effects and is high in safety; by inhibiting the PD1 signal channel and the activation effect of IL-2 molecules to