The present disclosure relates to compositions of methods of making and compositions small compositions of particles of an active agent. In accordance with the method of production, the active agent is dissolved in an aqueous or aqueous-miscible solvent containing a dissolved phase-separation enhancing agent (PSEA) to form a solution in a single liquid phase. The solution is subjected to a liquid-solid phase separation to cause the active agent to form small spherical particles that are substantially amorphous or non-crystalline and are injectable through fine bore needles at high concentrations. The particles exhibit the pharmacokinetic and pharmacodynamnic properties of the active agent. The disclosure has special application for higher molecular weight proteins such as antibodies.