Oxidation

Oxidation describes a chemical process involving loss of electrons from molecules, often occurring through reactions with reactive oxygen species or other oxidising agents, leading to structural changes that can alter biological function, stability, or activity. In pharmaceutical contexts, oxidation is a common degradation pathway affecting both small molecules and biologics, with susceptibility influenced by molecular structure, environmental conditions, and formulation composition.

The biopharmaceutical industry closely monitors oxidation as a critical quality attribute, particularly for therapeutic proteins where oxidation of methionine, tryptophan, or cysteine residues may reduce potency, alter receptor binding, increase aggregation, or change immunogenicity risk. Formulation development incorporates strategies to minimise oxidation through oxygen control, use of antioxidants, chelators to reduce metal-catalysed oxidation, and selection of stabilising excipients. Analytical characterisation employs mass spectrometry to identify oxidised residues, chromatography to detect oxidised variants, and functional assays to confirm biological impact. Regulatory submissions require stability data demonstrating oxidation control within acceptable limits. As biologics complexity increases and advanced modalities expand, oxidation management remains essential for ensuring consistent therapeutic performance.