From laboratory to clinic: Bridging regulatory and manufacturing gaps in stem cell-based therapies

Table 1 Representative regulatory frameworks for cell and gene therapies (non-exhaustive)

Jurisdiction	Key guidelines/regulations	Remarks
United States (FDA)	RMAT designation (21st Century Cures Act, 2016)[18]; multiple cell and gene therapy guidance documents (e.g., potency testing, viral safety)	Offers expedited development pathways; regulated under biologics framework
EU (EMA)	ATMP GMP guidelines (EudraLex Vol 4 Part IV, 2017)[17]; ATMP Regulation EC 1394/2007	Dedicated GMP annex for ATMPs; emphasizes risk-based quality management
Japan (PMDA)	Regenerative Medicine Act (2014); PMDA technical guidance on cell therapies	Conditional and time-limited approvals; includes nonclinical safety assessments, such as iPSC tumorigenicity[23]
China (NMPA)	Trial guidelines for stem cell products (2015-2023); GMP management updates (2022)[11,19]	Developing regulatory framework with a parallel “drug-like” pathway
WHO	TRS 1048 Annex 3 (2023); previous TRS 878 (1998) tumorigenicity recommendations	Defines ATMP categories and promotes regulatory harmonization[13,15]
PIC/S	GMP Annex 2A for ATMPs (effective May 2021)[12]	Supports global harmonization of GMP requirements, aligned with EU standards
ICH	Q5A(R2) Viral Safety (November 2023)[28]; additional quality modules	Emphasizes viral safety and risk-based management for biotech products

FDA: Food and Drug Administration; RMAT: Regenerative medicine advanced therapy; ATMPs: Advanced therapy medicinal products; EU: European Union; EMA: European Medicines Agency; GMP: Good manufacturing practice; PMDA: Pharmaceuticals and Medical Devices Agency; iPSC: Induced pluripotent stem cell; NMPA: National Medical Products Administration; WHO: World Health Organization; PIC/S: Pharmaceutical Inspection Co-operation Scheme; ICH: International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use.

Table 2 Representative cell expansion yields across culture platforms[48-50]

Culture platform	Typical cell density (cells/mL)
2D Multilayer Systems (CellSTACK, Hyperflask)	Approximately 2 × 105 to 6 × 105
Stirred-Tank Bioreactors (microcarrier/vertical-wheel)	Approximately 5 × 105 to 1.7 × 106
Hollow-Fiber Bioreactors (high surface area cartridges)	Approximately 1 × 107 to > 1 × 108

Reported yields vary depending on cell source, seeding density, media composition, and harvest/resuspension volume.

Table 3 Critical quality attributes and assays for advanced therapy medicinal product manufacturing

Attribute	Example assays/methods	Guideline references
Identity	Flow cytometry (cell surface markers), PCR for unique genes	EMA/ICH guidance, pharmacopoeias
Purity	Sterility testing, mycoplasma PCR, endotoxin (LAL assay)	Ph.Eur./USP
Viability	Dye exclusion (trypan blue, 7-AAD), metabolic activity assays	CBER/EMA guidance
Potency	Functional bioassays (e.g., MSC-mediated T-cell suppression)	Case-specific; often ICH Q6B
Genetic stability	Karyotype, array CGH, NGS for mutations	CBER draft guidance, ISSCR recommendations
Tumorigenicity	Soft agar colony formation, injection into immunodeficient mice[23]	WHO TRS 878, FDA draft guidance
Viral safety	Filtration of spent media, adventitious virus testing panels	ICH Q5A(R2)[27]
Exosome-specific	Particle size analysis (NTA), exosome marker proteins (CD63, CD81)[16]	MISEV2018 standard

PCR: Polymerase chain reaction; EMA: European Medicines Agency; ICH: International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use; Ph.Eur.: European Pharmacopoeia; USP: United States Pharmacopeia; 7-AAD: 7-aminoactinomycin D; CBER: Center for Biologics Evaluation and Research; MSC: Mesenchymal stem cell; CGH: Comparative genomic hybridization; NGS: Next-generation sequencing; ISSCR: International Society for Stem Cell Research; WHO: World Health Organization; FDA: Food and Drug Administration; NTA: Nanoparticle tracking analysis; MISEV2018: Minimal Information for Studies of Extracellular Vesicles 2018.