In a typical tablet or capsule formulation, the active drug is often present as a crystalline solid. This solid emerges from the relationships between the individual atoms within the crystal, which confer a distinct set of physical properties. Then, it follows that if we modify the packing arrangement of the individual molecules within these crystals, we can modulate their properties. This can be achieved by crystal engineering.

Crystal engineering has also seen teams arrange multiple drug molecules within the same crystal, resulting in dramatic improvements to drug properties in the lab. The success of drugs like SEGLENTIS® and Entresto® have revitalised interest in these forms, but controversy surrounding their translation has prompted this reconsideration of their clinical utility. I reflect on the current academic, clinical, and commercial interest in multidrug multicomponent crystals, drawing parallels with developments pre-Bragg, contributing to a nuanced understanding of the potential and limitations of crystal engineering in pharmaceutical applications.