5-Fluoroorotate: a new liposome-dependent cytotoxic agent.

The potency of 5-fluoroorotate for inhibition of L929 or CV1-P cell growth is increased by encapsulation in negatively charged liposomes. The optimal liposome composition is dipalmitoylphosphatidylglycerol: cholesterol, 67:33. Unextruded large unilamellar liposomes are the optimal size for delivery. This compound is the second transport-negative drug which we have found to exhibit liposome-dependent delivery.