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.
