The LTD 37 was based on DUPA, which was connectedto PTX via a cleavable S-S-linker (37, Figure ). It was hypothesized that the PSMA targeting of 37 wouldenhance PTX transport ability and tumor selectivity, minimizing adverseeffects. PTX was released invitro after treatment of prodrug 37 with DTT.This was a fast process in contrast to the DUPA-PTX control (connectedwith an ester bond), which was extremely slow. Here, FOLH1 is linked to neoplasm.