Development of a proficiency testing platform for advanced therapies medicinal products (ATMPs)

The development of Advanced Therapy Medicinal Products (ATMPs) is driving major advances in regenerative medicine, particularly in cellular immunotherapies. However, the reliable application of quality control methods remains a major challenge due to the inherent complexity of biotechnological products, especially when assays involve living cells. In this context, Proficiency Testing (PT) programs have proven to be highly effective tools for promoting analytical consistency and enhancing quality across laboratories in a wide range of application fields. This study presents the design and implementation of a PT program specifically adapted to ATMPs. The initiative was publicly funded by Andalusian Regional Government (Spain) and involved ATMP manufacturers, Tissue Establishments, and a Biobank from Spain and France.

Thirteen public ATMPs manufacturers, Tissue Establishments and one Biobank from Spain and France participated in the program. A dedicated web platform was developed to manage participant interactions and data submission, with the primary objective of ensuring anonymization of participants and their results. Standardized samples were simultaneously distributed to all sites to ensure consistency across assays. These included materials for mycoplasma detection, sterility testing, endotoxin quantification, immunophenotyping, cell counting, thawing yield, and growth promotion (cell doublings). At the end of each round, participants received an automated, personalized report benchmarking their performance against peer laboratories.

Across five rounds of proficiency testing involving 13 institutions, 331 valid results were reported from 372 distributed samples (88.9% response rate). Mycoplasma detection showed 77.8% sensitivity and 100% specificity. Sterility testing achieved 97% sensitivity and 100% specificity. Endotoxin assays yielded 100% accuracy across all samples. Immunophenotyping confirmed >95% expression of MSC markers, with minimal hematopoietic contamination. Moderate variability was observed in cell count results, with 57.1% aligning within ±20% of the median reference value. Growth promotion studies revealed superior cell doublings and shorter doublings times with human platelet lysate compared to fetal bovine serum. Thawing yield averaged 41.5%, with similar recovery between manual and automated methods. Satisfaction surveys indicated high approval for sample quality and identification, with constructive feedback on logistics and platform usability. Most participants supported program continuity through financial contribution.

This multicenter initiative highlights the value of interlaboratory comparisons for harmonizing ATMP methodologies. While sterility and endotoxin assays showed high consistency, cell-based techniques remain variable and need further standardization.