The United States Pharmacopeia has added an in vitro cell-based assay for the batch release of two insulins (glargine and lispro) as an alternative to the rabbit blood sugar bioidentity assay to Chapter <121> Insulin Assays. The rabbit assay, which requires 8-24 animals per batch, is not required in the European Union. Sanofi, which exports insulin to the US, began to validate an experimental in vitro test as an alternative to the rabbit assay in 2012, which was accepted in 2016 (see Hack et al., 2017, doi:10.14573/altex.1708091) and included in the guideline in December 2020.