Pharmaceutical Cocrystals: Formulation Approaches to Develop Robust Drug Products

Phase transformation of an active pharmaceutical ingredient in the solid state can influence the physicochemical properties and consequently drug product performance. The neat cocrystal of Ertugliflozin l-pyroglutamic acid (ERTLPG), trade name Steglatro, though stable at high temperature and humidity conditions, dissociated into the amorphous free form of ertugliflozin in the presence of excipients. The influence of the physicochemical properties of excipients on the physical stability of the cocrystal was investigated to gain a mechanistic understanding of cocrystal dissociation in tablet formulations. The test tablet formulations containing cocrystal and excipient(s) were prepared and stored at stressed conditions. Note that cocrystal dissociation was observed at these conditions in the presence of excipients. An FT-Raman spectroscopy method in combination with a partial least-squares (PLS) regression model was utilized to evaluate the cocrystal dissociation. To evaluate the effect of excipients on cocrystal dissociation, a binary excipient compatibility study was conducted. Excipients used for a binary formulations study were categorized into four classes based on their physicochemical properties as a function of the physical stability of the cocrystal in the binary tablet/powder formulations. The results revealed that there is a good correlation between excipient properties (at least pH and hygroscopicity) and cocrystal dissociation in the formulations. Finally, to mitigate cocrystal dissociation in sold oral dosage forms, i.e., tablets, research tablet formulations that contained cocrystal particles coated with hydrophobic silica and a pH modifier were prepared and stored at accelerated stability conditions (40 °C/75% RH) for up to 4 weeks. The research tablet formulations demonstrated improved physical stability of the cocrystal at accelerated conditions. The present study suggests that, in general, there is a propensity of basic excipients to induce cocrystal dissociation that contain acidic coformers during drug product manufacturing and storage. Our findings from the current study demonstrated an in-depth mechanistic understanding of factors influencing cocrystal dissociation and mitigation strategies that will aid to develop robust solid oral dosage forms.