Review of 'Measures to minimize cross-contamination risks in Advanced Therapy Medicinal Product manufacturing'

The paper certainly addresses a critical topic for cell based medicinal products. The title of the paper is very promising but the content does not meet the expectations. The introduction is correct but I would not agree to consider at the same level the three “main” characteristics described for an ATMP, i.e. "safety, consistency and absence of cross-contamination". Actually, cross-contamination is just one aspect of safety (as later described by the authors). The authors refer to the term cross-contamination “to indicate misidentification of one cell line or culture by another”. This is correct but it is not the only meaning of the term in the context of GMP (good manufacturing practice) and the measures described in the paper to avoid cross-contamination do mainly refer to other types of cross-contamination, i.e. microbiological contamination from the environment, personnel, raw materials or donors. This section of the paper is adequate but it is only a brief description of some of the requirements covered in GMP guidelines.

Regarding the main part of the paper (How to prove the absence of cross-contamination in an ATMP) it is difficult to see what is new from their previous paper (references 10 and 11). However, the value of the technique they describe is acknowledged, also to ensure traceability throughout the production process and to the patient, another requirement for cell based medicinal products.

Although the bibliography included in the paper is correct important specific references could have been added, i.e. Directive 2009/120/EC (where somatic cell therapy medicinal products are defined), or Annex 2 of the GMP guidelines (where there specific aspects for ATMP are described).