The relevance of solid form in drug development has been well established over time. In order to fully understand drug properties, attention has been paid to solid state structure of drug molecules and their relationship to the drug formulation. While each drug developer has had their own strategies and workflows for screening and choosing solid forms of drug molecules, the industry is aware of instances where “the best laid plans” often go awry. This manuscript has summarized several case studies in development programs that display the “good, bad, and ugly” of solid form changes.

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