As well as selec on of a suitable polymer and processing method, the drug-to-polymer ra o is cri cally important. While a drug loading below the solubility limit ensures a thermodynamically stable ASD (at a given temperature and humidity/water content), higher drug loadings are o en required and instead kine c stabiliza on by the polymer must be relied upon to prevent undesirable physical changes during storage and administra on . Tradi onally, inhibi on of drug crystalliza on during storage and drug release has been considered the most important parameters to control during the development of ASDs . However, more recently, amorphous-amorphous phase separa on (AAPS) has also been revealed to be cri cally important. Substan al progress has been made over the last few years into understanding such phase separa on, both during storage (as a func on of temperature and rela ve humidity) , and more recently during drug release in aqueous media .