Improving Solubility by Crystallographic Disorder: Enabling Peposertib First-in-Human Trials

Peposertib is a small molecule inhibitor of the DNA-dependent protein kinase, currently being evaluated in clinical trials in patients with advanced solid tumours. The active pharmaceutical ingredient (API) exhibits low solubility as a result of the required multi-parameter optimization drug design that in turn necessitated an innovative approach to enable a fast-track first-in -human clinical trial. Peposertib belongs to class II according to the biopharmaceutical classification system (BCS) and class IIb according to the developability classification system (DCS). During polymorphic screening a crystallographically disordered solid-state form (A2D) was discovered which showed significantly increased in vitro performance compared to the thermodynamically stable solid-state form (A2). Disorder occurs along one crystallographic axis and leads to reduced lattice energy and consequently higher solubility. Despite being a metastable morphic form, the solid material of desired form A2D showed very high chemical and physical stability as well as favorable physical properties. These attributes are frequently considerable drawbacks in the case of amorphous materials. A significant challenge when compared to amorphous or highly crystalline phases, which are usually better defined, is the variability in the degree of disorder. This issue was addressed through the development of a process that demonstrated robustness at the manufacturing scale. By employing microstrain analysis, we established a reliable method for material characterization, while thermal analysis further aids in identifying higher crystalline fractions within the disordered bulk material. It allowed fast entry into first-in-human clinical trials with the objective of transitioning to a bio-enabling formulation, which necessitates a more time-consuming development process. To the best of our knowledge, this is the first time a crystallographically disordered phase has not only been discovered but also thoroughly investigated, and consequently utilized to accelerate entry into clinical development.