Product variants are contaminants because they bear properties that are different from those of desired biological products with respect to activity, efficacy, and safety. Thus, such variants can compromise product quality and consistency. In this eBook, Yuval Shimoni explores different types of variants — including primary-sequence variants, undesirable posttranslational modifications, aggregates, and degraded proteins — and explains how their presence can diminish the performance and quality of drug substances and products. He also discusses how product variants form at different…