Amotosalen hydrochloride (S-59) is a light-activated, DNA-, RNA-crosslinking psoralen compound, which is used to neutralise pathogens[1].
When activated by light, Amotosalen binds to the nucleic acid of the pathogen and prevents replication. Light-activated Amotosalen binds and permanently crosslinks DNA, preventing replication and thus stopping proliferation of donor T cells[1].
[1]. Amotosalen: Allogeneic Cellular Immunotherapies system, INTERCEPT Plasma System, INTERCEPT Platelet System, S 59. BioDrugs. 2003;17(1):66-8.