Upgrading Monocytes Therapy for Critical Limb Ischemia Patient Treatment: Pre-Clinical and GMP-Validation Aspects

Advanced cell therapy medicinal products (ATMP) are at the forefront of a new range of biopharmaceuticals. The use of ATMP has evolved and increased in the last decades, representing a new approach to treating diseases that are not effectively managed with conventional treatments. The standard worldwide recognized for drug production is the Good Manufacturing Practices (GMP), widely used in the pharma production of synthesized drugs but applying also to ATMP. GMP guidelines are worldwide recognized standards to manufacture medicinal products to guarantee high quality, safety, and efficacy. In this report, we describe the pre-clinical and the GMP upgrade of peripheral blood mononuclear cell (PBMC) preparation, starting from peripheral blood and ending up with a GMP-grade clinical product ready to be used in patients with critical limb ischemia (CLI). We also evaluated production in hypoxic conditions to increase PBMC functional activity and angiogenic potential. Furthermore, we extensively analyzed the storage and transport conditions of the final product as required by the regulatory body for ATMPs. Altogether, results suggest that the whole manufacturing process can be performed for clinical application. Peripheral blood collected by a physician should be transported at room temperature, and PBMCs should be isolated in a clean room within 8 h of venipuncture. Frozen cells can be stored in nitrogen vapors and thawed for up to 12 months. PBMCs resuspended in 5% human albumin solution should be stored and transported at 4 °C before injection in patients within 24 h to thawing. Hypoxic conditioning of PBMCs should be implemented for clinical application, as it showed a significant enhancement of PBMC functional activity, in particular with increased adhesion, migration, and oxidative stress resistance. We demonstrated the feasibility and the quality of a GMP-enriched suspension of monocytes as an ATMP, tested in a clean room facility for all aspects related to production in respect of all the GMP criteria that allow its use as an ATMP. We think that these results could ease the way to the clinical application of ATMPs.