One of the most successful suicide genes is the inducible caspase-9 (iCasp9) gene, where the dimerization of iCasp9 by a small molecule compound can trigger the apoptosis of 90% of the modified T cells within 30 min in GVHD patients and end GVHD without recurrence.124. Here, CASP9 is linked to graft versus host disease.