Therapeutic compositions containing glutathione analogs

A method of preparing a liposomal formulation containing a compound that is:

• (i) a diester of a compound of formula A
• where:
• each ester is 1–25C;
• YCO is γ-glu or β-asp;
• G* is phenylglycine;
• Z is CH2, O or S;
• and
• X is a hydrocarbon radical which is alkyl (6–8C), benzyl, or naphthyl;
• or a pharmaceutically acceptable salt thereof;
• or
• (ii) a compound of formula I
• where:
• R1 and R2 are each independently linear or branched alkyl (1–25C), cycloalkyl (6–25C),
• heterocycle (6–25C), ether or polyether (3–25G), or R1 and R2 together have 2–20 C atoms
• and form a macrocycle with the remainder of formula I;
• and
• X is as defined above for formula A;
• or a pharmaceutically acceptable salt thereof;
• which method comprises formulating the compound in a liposomal composition
• where the lipids of the liposomal formulation consist of egg phosphatidylcholine and egg phosphatidylglycerol in a ratio of 0.75–1.25:0.75–1.25 by weight and the ratio of lipids to compound is 3.5–4.5:0.5–1.5 by weight.