The advantage of obtaining different batches of the same active ingredient is that these batches come from different manufacturing runs. Therefore, they have different biological and physiochemical properties: The active pharmaceutical ingredient (API) of each product run, i.e., the drug substance, may contain minute batch-specific variations that depend on a number of exogenous production conditions such as pH, cell culture medium, temperature, and endogenous factors including post-transcriptional and -translational modifications. 

In particular, biosimilar developers ask for reference product batches from different (originator) production runs: obtaining a range of different production batches for a biocompatibility assay helps characterize these batch-specific differences.