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©2021 by The International Society for Stem Cell Research. All rights reserved.

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3.1 Classifying Stem Cell-, Cell-, and Tissue-based Interventions

Recommendation 3.1.1: Stem cells, cells, and tissues that are substantially manipulated or used in a non-homologous manner must be proven safe and effective for the intended use before being marketed to patients or incorporated into standard clinical care. 

The therapeutic use of substantially manipulated stem cells, cells, or tissues or minimally manipulated stem cells, cells, or tissues for non-homologous treatments is complex, speculative, and has been shown to have risks to recipients. These products should be thoroughly tested in preclinical and clinical studies and evaluated by regulators as drugs, biologics, and advanced therapy medicinal products. 

Minimally Manipulated Stem Cells, Cells, and Tissues

Minimally manipulated cells and tissues, such as, in some cases, fat tissue transferred from one part of the body to another, are generally subject to fewer regulatory requirements. When a stem cell-, cell-, or tissue-based intervention is claimed to be minimally manipulated and exempt from regulatory oversight on this basis, the responsibility rests on the clinician to invite independent scrutiny of their process of manipulation, such that scientific and regulatory experts can determine the proper level of regulatory oversight. When there is uncertainty or disagreement about the regulatory status of particular interventions, it is best to contact legally authorized regulatory bodies and seek their guidance concerning how specific interventions are classified. The US Food and Drug Administration, European Medicines Agency, Australian Therapeutic Goods Administration, Japanese Ministry of Health, Labour, and Welfare, and other regulators have released detailed standards to delineate when manipulation of cell-based products can no longer be considered minimal or their use homologous, and must therefore be subject to regulatory oversight as an advanced therapy product.  

Substantially Manipulated Stem Cells, Cells, and Tissues

Substantially manipulated stem cells, cells, and tissues are subjected to processing steps that alter their original structural or biological characteristics. These processes can include isolation and purification processes, tissue culture and expansion of the cells, genetic manipulation, or other steps. For example, the extraction of cells from adipose tissue using enzymatic digestion, ultrasonic cavitation, or other means involves processing steps that can alter the original function of the cells imbedded in the tissue. The safety and efficacy profile of such an intervention needs to be determined for its particular indication using rigorous research methods. Safety and efficacy cannot be assumed because the composition of the intervention may differ from the original source tissue. Demonstration of safety and effectiveness will depend on the particular intervention and the specific condition targeted. Both to protect patients from risks and to help ensure that promising interventions are studied, it is critical that cells and tissues that have been substantially manipulated are evaluated by national regulators as drugs, biologics, and advanced therapy medicinal products.

Non-homologous Use of Stem Cells, Cells, and Tissues

Non-homologous use occurs when the stem cells, cells, or tissue are repurposed to perform a different basic function in the recipient than the cells or tissue originally performed prior to being removed, processed, and transplanted or otherwise delivered. For example, delivering adipose-derived stromal cells into the eye with the intent to treat macular degeneration would be a non-homologous use because the basic function of adipose tissue is not the trophic support of the retina. As with substantially manipulated cells and tissues, the non-homologous use of stem cells, cells, and tissues has potential benefits but can also pose serious risks. In the case of using adipose-derived stromal cells to treat macular degeneration, for example, there are well-documented reports of vision loss (Kuriyan et al., 2017). Such reports serve as a reminder that cells and tissues, depending on how they are administered, can cause serious harm. The benefit-risk ratio for non-homologous uses will depend on the particular intervention and the specific use. To protect patients from risks, and to ensure that necessary research is conducted, it is important that the safety and effectiveness of non-homologous uses be rigorously evaluated by regulators following the completion of well-designed and carefully controlled preclinical and clinical studies. 

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