This episode focuses on the crucial role of starting materials in drug substance (API) development and the regulatory considerations surrounding their selection. Starting materials are defined as specific substances that become significant structural parts of the final API molecule, and the episode emphasizes that their designation is not arbitrary but carries significant regulatory weight. The conversation explores how companies must justify their choice of starting materials, providing a solid rationale for why a specific substance is appropriate as the starting point. The key factors regulators consider are examined.

The discussion emphasizes the material's role in the synthetic pathway, its quality and purity, and the number of chemical steps between the starting material and the final API. Risk assessment is highlighted as an indispensable tool for managing potential problems and sources of variability in the starting material's manufacturing process. The importance of aligning with quality by design (QbD) principles is emphasized, along with the underlying philosophy of being proactive and building quality into the product from the beginning. The episode details the deep understanding required when manufacturing the best quality drug.