Described is the sequential administration of first a Treg depleting antibody mole- cute selected from antibody molecules, such as an antibody molecule binding specifically to target belonging to the tumour necrosis factor receptor superfamily (TNFRSF), such as a Treg depleting anti-4-1 BB antibody or a Treg depleting OX-40 antibody, and then an immunostimulatory antibody molecule, such as an immunostimulatory anti-4-1 BB anti- body or an immunostimulatory OX-40 antibody, for use in the treatment of cancer. De- scribed are also novel anti-4-1 BB antibodies and novel OX-40 antibodies that may be used in such sequential administration.