Comparability of MSC manufacturing protocols for clinical trials

Background & Aim Mesenchymal stromal cells (MSC) are clinically applied for their immunomodulatory and regenerative capacities. Despite promising results, comparison of the many different trials is hampered by the heterogeneity in MSC manufacturing protocols. Understanding and delineation of the impact of different production methods by harmonized QC-tests and in-process controls in this respect, will be crucial to optimize MSC therapy for use in larger groups of patients. Methods, Results & Conclusion In our center, MSC are generated from bone marrow mononuclear cells (BM-MNC) using ficoll density centrifugation and subsequent expansion steps in T-flasks. After passaging 3 times, MSC are harvested and cryopreserved in a typical product size of 300 × 106 cells. Previously, changes in our clinical MSC manufacturing protocol involved changes in antibiotics and providers of raw materials such as ficoll and albumin. For GMP-conform change of control validation, comparability studies were performed and >30 real-time manufacturing procedures before and after these changes were compared for classical release criteria such as identity, purity and potency as well as by in-process tests and controls. Notwithstanding the seemingly small changes, the change in ficoll e.g. modulated the BM-MNC subsets composition of the initial MSC culture. Moreover, changing the antibiotics-regimen significantly decreased the population doubling level and decreased the drug product yield at second passage. Despite these differences, identity and purity of the drug products were comparable for both manufacturing protocols. In conclusion, even minor changes in a clinical manufacturing protocol can have a significant impact on MSC production and possibly also on its therapeutic characteristics. Our results indicate that for proper comparisons between trial results, detailed harmonization of production methods but also verification of this by standardized QC testing is needed. This will be the key for optimizing and and proper comparison of cell therapies.