The present invention relates to pre-formulations comprising low viscosity, non- liquid crystalline, mixtures of: a) at least one ester of a sugar or sugar derivative； b) at least one phospholipid； c) at least one biocompatible, oxygen containing, low viscosity organic solvent； wherein the pre-formulation forms, or is capable of forming, at least one liquid crystalline phase structure upon contact with an aqueous fluid； with the proviso that the pre-formulation does not further comprise a liquid crystal hardener. The preformulations are suitable for generating parenteral, non-parenteral and topical depot compositions for sustained release of active agents. The invention additionally relates to a method of delivery of an active agent comprising administration of a preformulation of the invention, a depot composition formed by exposing pre-formulations of the invention to an aqueous fluid, a method of treatment comprising administration of a preformulation of the invention and the use of a preformulation of the invention.
