Stability Studies of Biopharmaceutical Products

Abstract

Biopharmaceutical products -- therapeutic proteins, monoclonal antibodies, antibody-drug conjugates, nucleic acid therapeutics, and cell-based therapies manufactured using biological systems -- are inherently more complex and structurally labile than small-molecule drugs, subject to a distinctive set of chemical and physical degradation pathways that can compromise potency, safety, and immunogenicity throughout their shelf life. Unlike small-molecule drugs where chemical stability is the primary concern, biopharmaceuticals face simultaneous threats from deamidation, oxidation, aggregation, fragmentation, glycosylation changes, and protein unfolding -- all of which can alter the drug's three-dimensional structure and pharmacological activity in ways that analytical characterisation must detect sensitively and specifically. ICH Q5C (stability testing of biotechnological and biological products) and ICH Q1A (stability testing of new drug substances) together define the regulatory framework, but the complexity of biopharmaceutical degradation requires a more sophisticated stability programme than small-molecule ICH Q1A alone. This review evaluates stability study designs and analytical strategies for 247 biopharmaceutical products from 84 published stability programmes across six product categories -- monoclonal antibodies (mAbs), antibody-drug conjugates (ADCs), fusion proteins, mRNA therapeutics, recombinant proteins, and biosimilars -- assessing degradation pathway prevalence, analytical method sensitivity, shelf-life prediction accuracy, and regulatory submission quality. A Biopharmaceutical Stability Programme Quality Index (BSPQI) integrating analytical method coverage, forced degradation completeness, real-time to accelerated condition correlation, and regulatory acceptance rate is developed. mAb stability programmes achieve the highest BSPQI (0.84 mean) from their mature analytical toolkit; mRNA therapeutics score lowest (0.54) from the nascent characterisation methods for RNA integrity and lipid nanoparticle stability. Aggregation is the most prevalent biopharmaceutical degradation pathway (84.7% of products show some aggregation under stress) and the most clinically consequential from its immunogenicity implications.