Degradation, Carryover, and Toxicity Assessment Challenges in Process Cleaning Validation

BioPharm International contributing editor Cynthia Challener about the challenges associated with establishing residue limits for cleaning process validation in the biopharmaceutical industry.

Challenges of establishing residual limitsBioPharm International: What are the challenges that companies face today when establishing residual limits for cleaning process validation of biopharmaceutical manufacturing processes?
LeBlanc (Cleaning Validation Technologies): The fact that biotech actives are almost universally degraded by cleaning processes using hot, aqueous, alkaline cleaning solutions is the main challenge. The residues left after cleaning are not the native protein (the API), but rather degradants of that protein. It is generally believed that those degraded fragments are less of a hazard (or no worse a hazard) than the native protein, in part due to the immunotoxicity of proteins, which is known to be a function of molecular weight (smaller molecular weight proteins are of less concern). Because of the degradation issue, some companies will actually perform laboratory simulations to measure degradation that may include evaluations to identify smaller fragments (using sodium dodecyl sulfate polyacrylamide gel electrophoresis [SDS-PAGE]) and/or a biological activity test to confirm that the degradants are not biologically active in the same manner as the native protein. The unknown question is whether those fragments are associated with some new toxicity concerns. There is no simple and practical way to answer this question, unless the structure of the API itself can explain the concerns related to the degradants.

Separately, the use of carryover calculations on the bulk manufacturing side of biotech is problematic. Total organic carbon (TOC) and total protein analyses are used for biopharmaceutical cleaning process validation because a specific analytical method for residue determination is not appropriate due to the fact that API residues are degraded. If the total surface area of the equipment train is utilized, however, the ratio of the batch size to the surface area drives limits so low that they are not measureable using these techniques. This issue can be balanced by the fact that it is a reasonable scientific expectation that residues from earlier cleaning steps following fermentation and harvesting will be removed by the various chromatographic purification processes used in downstream processing. For this reason, many companies choose to do a carryover calculation for bulk manufacture based on the equipment surface area after purification. In carryover calculations of this type, one assumes that all of the TOC (if that is the analytical method) is due to the native protein, even though it is known that what is being measured are degraded fragments of that protein and other organic materials.

It has been my belief, however, that the major risk on the bulk side of biotech is not that residues will carry over to the next product and cause a safety concern, but rather that residues will carry over and interfere with the manufacturing process and cause problems, such as a low yield or contamination of the product with extraneous proteins.

BioPharm International: Have the challenges changed over the past decade or so?
LeBlanc (Cleaning Validation Technologies): The newer challenge is setting limits based on a toxicological evaluation, such as the establishment of Acceptable Daily Exposure (ADE) limits to support the Risk-Based Manufacture of Pharmaceutical Products (Risk-MaPP) issued by the International Society for Pharmaceutical Engineering (ISPE) and the Permissible Daily Exposure (PDE) limits established by the European Medicines Agency (EMA). In one sense, setting limits doesn’t make things any easier or any more difficult, because the degraded fragments that are the residues can still carry over to the next product. However, it is still difficult to relate toxicological measurements of the native protein to real safety concerns presented by the residues, which are the degraded fragments.

BioPharm International: What are the best strategies for overcoming these challenges?
LeBlanc (Cleaning Validation Technologies): The best strategy for overcoming these concerns is to perform adequate degradation studies in order to demonstrate that degradation does, in fact, occur. When I bring this up to protein chemists, they generally say that the proteins are degraded from hot aqueous, alkaline, cleaning solutions. They are correct, but it is better to have data that demonstrate that degradation has occurred and the degree of said degradation (molecular weight), as well as data to confirm the lack of biological activity of the proteins (or, at least, the same biological activity as the native protein). A second method for dealing with the “soft” manner in which limits for bulk biopharmaceutical cleaning process validation are set is to establish action/alert levels for TOC or conductivity as part of the routine monitoring of every cleaning event. Such action levels are considered to be part of what  FDA calls “continued process verification” in its process validation guidance (1). These actions can be implemented in order to establish a process capability with trend charts, which can in turn help demonstrate that the cleaning process remains in a state of control.

Inappropriate residual levelsBioPharm International: If inappropriate residual levels are selected, what are the potential consequences? What are the best strategies for dealing with inappropriate residual levels?
LeBlanc (Cleaning Validation Technologies): If inappropriate residue levels are selected for validation protocols, it may lead to production issues for the next product, safety issues with the next product, and/or regulatory inspection issues. The best way to avoid such situations is to stay current with the issues related to cleaning validation in general, and cleaning validation for the biotechnology industry specifically. Using the available resources (such as PDA’s Technical Report #49, Points to Consider for Biotechnology Cleaning Validation (2), it is possible to design an approach to reduce the safety risk to patients and the business risk to manufacturers of excessive residual levels.

BioPharm International: Has the shift to smaller, more flexible manufacturing facilities that produce multiple products had an impact on the risk of residues?
LeBlanc (Cleaning Validation Technologies): The shift to smaller manufacturing facilities has, to my knowledge, been more related to process development and to the fact that more concentrated proteins can be prepared. It has also been tied to the use of disposable (single-use) equipment, which for a development project can shorten the timeline and reduce capital costs. Of course, there are issues with these options, such as extractables and leachables, that require careful consideration. The use of disposables does, however, remove the need to do cleaning validation, although a cleaning and/or decontamination step may still be required for proper disposal.

References
1. FDA, Guidance for Industry, Process Validation: General Principles and Practices (Rockville, MD, January 2011).
2. PDA, Technical Report No. 49: Points to Consider for Biotechnology Cleaning Validation (Bethesda, MD, July 2010).

About the Author
Cynthia A. Challener is a contributing editor to BioPharm International.

Article DetailsBioPharm International
Vol. 27, No. 12
Pages: 46-47
Citation: When referring to this article, please cite it as C. Challener, "Degradation, Carryover, and Toxicity Assessment Challenges in Process Cleaning Validation," BioPharm International27 (12) 2014.