A fusion protein comprising: (a) at least one variant caspase sequence, and (b) at least one inhibitor of anti-apoptotic proteins, and (c) a tobacco etch virus protease; wherein: (i) the said at least one variant caspase, at least one inhibitor and TEV protease are all separated by recognition sites for the TEV protease, so they can be released from each other upon cleavage by the TEV protease; (ii) the said variant caspase comprises a TEV recognition site, so that upon cleavage by TEV protease two fragments of the caspase are released; wherein the modified caspase is selected from the group consisting of: - variant caspase 3 having SEQ ID no. 5, from which the fragments of SEQ ID no. 9 and 10 are released upon cleavage by the TEV protease; - variant caspase 7 having SEQ ID no. 6, from which the fragments of SEQ ID no. 11 and 12 are released upon cleavage by the TEV protease; - variant caspase 8 having SEQ ID no. 7, from which the fragments of SEQ ID no. 13 and 14 are released upon cleavage by the TEV protease; - variant caspase 10 having SEQ ID no. 8, from which the fragments of SEQ ID no. 15 and 16 are released upon cleavage by the TEV protease; (iii) the said inhibitor of anti-apoptotic proteins is selected from the group consisting of: - Smac/DIABLO (SEQ ID no. 17) and / or - XAF1 (SEQ ID no. 18); (iv) the said recognition sites for TEV protease separating the at least one variant caspase, the at least one inhibitor and the TEV protease are selected from the group consisting of ENKYFQS (SEQ ID no. 3) and ENLYFQG (SEQ ID no.4). (a) at least one variant caspase sequence, and (b) at least one inhibitor of anti-apoptotic proteins, and (c) a tobacco etch virus protease; (i) the said at least one variant caspase, at least one inhibitor and TEV protease are all separated by recognition sites for the TEV protease, so they can be released from each other upon cleavage by the TEV protease; (ii) the said variant caspase comprises a TEV recognition site, so that upon cleavage by TEV protease two fragments of the caspase are released; wherein the modified caspase is selected from the group consisting of: - variant caspase 3 having SEQ ID no. 5, from which the fragments of SEQ ID no. 9 and 10 are released upon cleavage by the TEV protease; - variant caspase 7 having SEQ ID no. 6, from which the fragments of SEQ ID no. 11 and 12 are released upon cleavage by the TEV protease; - variant caspase 8 having SEQ ID no. 7, from which the fragments of SEQ ID no. 13 and 14 are released upon cleavage by the TEV protease; - variant caspase 10 having SEQ ID no. 8, from which the fragments of SEQ ID no. 15 and 16 are released upon cleavage by the TEV protease; - variant caspase 3 having SEQ ID no. 5, from which the fragments of SEQ ID no. 9 and 10 are released upon cleavage by the TEV protease; - variant caspase 7 having SEQ ID no. 6, from which the fragments of SEQ ID no. 11 and 12 are released upon cleavage by the TEV protease; - variant caspase 8 having SEQ ID no. 7, from which the fragments of SEQ ID no. 13 and 14 are released upon cleavage by the TEV protease; - variant caspase 10 having SEQ ID no. 8, from which the fragments of SEQ ID no. 15 and 16 are released upon cleavage by the TEV protease; (iii) the said inhibitor of anti-apoptotic proteins is selected from the group consisting of: - Smac/DIABLO (SEQ ID no. 17) and / or - XAF1 (SEQ ID no. 18); - Smac/DIABLO (SEQ ID no. 17) and / or - XAF1 (SEQ ID no. 18); (iv) the said recognition sites for TEV protease separating the at least one variant caspase, the at least one inhibitor and the TEV protease are selected from the group consisting of ENKYFQS (SEQ ID no. 3) and ENLYFQG (SEQ ID no.4).