This thesis aims at investigating the root causes of aggregate formation during the industrial production of Ticagrelor, an anticoagulant active pharmaceutical ingredient patented by AstraZeneca. The study focuses on the crystallisation stage, where the addition of an antisolvent generates supersaturation, inducing crystal formation. Antisolvent crystallisation is widely used for isolating and purifying pharmaceutical compounds, however, it presents challenges such as the formation of unwanted aggregates that affect particle size distribution (PSD), a critical parameter for product processability, quality and bioavailability. For technical and economic reasons, experiments were conducted using a laboratory-scale reactor designed to replicate as closely as possible the industrial process.