Q-VD-OPh (quinolyl-valyl-O-methylaspartyl-[-2,6-difluorophenoxy]-methyl ketone) is a broad-spectrum caspase inhibitor, provides a cost-effective, non-toxic, and highly specific means of apoptotic inhibition and provides new insight into the design of new inhibitors.

It is significantly more effective in preventing apoptosis than the widely used inhibitors, ZVAD-fmk and Boc-D-fmk. Q-VD-OPh is also equally effective in preventing apoptosis mediated by the three major apoptotic pathways, caspase 9/3, caspase 8/10, and caspase 12. In addition to the increased effectiveness, Q-VD-OPh was not toxic to cells, even at high concentrations. Q-VD-OPh is equally effective at inhibiting the three major apoptotic pathways, it can inhibit recombinant caspases 1, 3, 8, and 9 with IC50 values ranging from 25 to 400 nM2. The effectiveness of Q-VD-OPh as an apoptotic inhibitor is evidenced by the complete suppression of an apoptotic inducer capable of inducing substantial cell death in less than 4 hours. Q-VD-OPh protected against the substantial apoptosis induced by actinomycin D. In addition, Q-VD-OPh alone exhibited little or no toxicity, even at extremely high concentrations [2].