The present disclosure relates to a combined pharmaceutical composition, adapted for simultaneous, separate, or sequential administration for treating cancer in a subject comprising (a) a conjugate comprising (i) a polypeptide comprising the amino acid sequence of interleukin 15 or derivatives thereof, and ii) a polypeptide comprising the amino acid sequence of the sushi domain of IL-15Ra or derivatives thereof; a polynucleotide coding therefore, or a vector comprising such a polynucleotide; and (b) an antibody antagonizing an immune pathway implicated in the inhibition of T cell activation, or a fragment thereof, a polynucleotide coding therefore, or a vector comprising such a polynucleotide.