The disclosure relates to pre-formulation compositions comprising a low viscosity mixture of 20 - 80 wt.% of at least one diacyl glycerol and/or a tocopherol b) 20-80 wt. % of at least one phosphatidyl choline (PC) c) 5-20 wt. % of at least one biocompatible, organic mono-alcoholic solvent d) up to 20 wt.% polar solvent e) at least one peptide active agent f) optionally at least one antioxidant wherein the ratio of components a:b is in the range 40:60 to 54:46 wherein the pre-formulation forms, or is capable of forming, at least one liquid crystalline phase structure upon contact with excess aqueous fluid. The peptide active agent may be a somatostatin analogue selected from somatostatin 14, somatostatin 28, octreotide, lanreotide, pasireotide and vapreotide and the antioxidant may be ascorbic acid, EDTA or citric acid. The disclosure also relates to the use of these compositions to treat diseases, including cancer, and pre-filled administration devices and kits containing the formulations.
