The present invention relates to methods for developing engineered T-cells for immunotherapy and more specifically to methods for modifying T-cells by inactivating at immune checkpoint genes, preferably at least two selected from different pathways, to increase T-cell immune activity. This method involves the use of specific rare cutting endonucleases, in particular TALE-nucleases (TAL effector endonuclease) and polynucleotides encoding such polypeptides, to precisely target a selection of key genes in T-cells, which are available from donors or from culture of primary cells. The invention opens the way to highly efficient adoptive immunotherapy strategies for treating cancer and viral infections.
