Described is a composition comprising (a) a population of particles of an aripiprazole prodrug having a volume based particle size (Dv50) of less than 1000 nm and (b) at least one surface stabilizer comprising an adsorbed component which is adsorbed on the surface of the aripiprazole prodrug particles and a free component available for solubilisation of the aripiprazole prodrug. The surface stabilizer to prodrug ratio provides the optimal quantity of free surface stabilizer for the purposes of producing a lead-in formulation. Also described are methods of treatment using the aforementioned composition.