Solubility is a key concern for any drug delivery system or technology. Unfortunately, industry pipelines are full of compounds with poor solubility and poor permeability – and it’s unlikely that the problem will ever be completely eliminated. Pharmaceutical pipelines full of poorly soluble and poorly permeable compounds present significant challenges for established delivery platforms, particularly transdermal drug delivery and controlled release technologies, driving a growing interest in more innovative drug delivery methods. As such, many poorly soluble compounds are formulated as immediate release drug products to first improve the aqueous solubility of the API. Switching these to controlled release requires significant innovation because achieving both solubilization and controlled release is not straightforward. Nevertheless, solving these challenges is critical when it comes to managing the lifecycle of poorly soluble products.
Traditional approaches to improve drug solubility include drug-salt formation, complexation and polymorph selection; however we are seeing a growing number of compounds that are so insoluble that these standard techniques are inadequate. This has led to new formulation approaches for the pharmaceutical industry; for example, the application of amorphous solid dispersion techniques such as spray drying and hot melt extrusion and development of novel polymers that are specifically designed for these processes. Matching an API to the optimal solubility enhancement technology is challenging due to the great variety of available polymers, techniques and the complexity of pipeline APIs and difficulties in predicting polymer-API interactions. That’s why we often see companies taking multiple formulations into early phase development – if one candidate fails, there’s another to take its place. We also advise companies to consider the impact of polymer variability on final product performance – a Quality-by-Design approach to polymer properties and their impact on performance helps ensure robust performance of the finished product.
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