Discovery of medium ring thiophosphorus based heterocycles as antiproliferative agents.

Hydrogen sulfide (H 2 S) has been investigated for its potential in therapy. Recently, we reported novel H 2 S donor molecules based on a thiophosphorus core, which slowly release H 2 S and have improved anti-proliferative activity in cancer cell lines compared to the most widely studied H 2 S donor GYY4137 ( 1 ). Herein, we have prepared new thiophosphorus organic H 2 S donors with different ring sizes and evaluated them in two solid tumor cell lines and one normal cell line. A seven membered ring compound, 17 , was found to be the most potent with sub-micromolar IC 50s in breast (0.76 μM) and ovarian (0.76 μM) cancer cell lines. No significant H 2 S release was detected in aqueous solution for this compound. However, confocal imaging showed that H 2 S was released from 17 inside cells at a similar level to the widely studied H 2 S donor GYY4137, which was shown to release 10 μM H 2 S after 12 h at a concentration of 400 μM. Comparison of 17 with its non-sulfur oxygen analogue, 26 , provided evidence that the sulfur atom is important for its potency. However, the significant potency observed for 26 (5.94–11.0 μM) indicates that the high potency of 17 is not entirely due to release of H 2 S. Additional mechanism(s) appear to be responsible for the observed activity, hence more detailed studies are required to better understand the role of H 2 S in cancer with potent thiophosphorus agents. [ABSTRACT FROM AUTHOR]