The use of biological starting materials in the development of allogeneic cell-based therapies poses several challenges, whether due to availability of appropriate donors, complicated global logistics, or lack of global regulatory harmonisation around technical testing requirements. Sponsors must pay attention to adventitious agent safety requirements, which vary from region to region, and can also be affected by emerging disease threats, as was the case with the recent COVID-19 pandemic. Dr Elena Meurer, principal consultant and director at Biopharma Excellence, and Dr Jennifer Sales, consultant at Biopharma Excellence, explore these complexities.