Extractables and Leachables from Single Use Systems and Multi-Use Equipment Used in Pharmaceutical and Biotherapeutic Manufacturing
Leachables from single use systems (SUS)and multi-use manufacturing equipment (MUE) that migrate into drug or biological products have a potentially negative impact on safety. To evaluate this risk, extraction studies are performed under conditions designed to simulate the use of the equipment. The goal of these extraction studies is to identify as extractables the leachables that could migrate into the product. The extractables profile can then be used to set operational limits on the SUS or MUE as needed. Further toxicological assessment may be required based upon the observed levels of leachables.
Leachables are compounds that migrate into drug or biological products from materials encountered in the manufacturing process. Plastics and elastomers components are the most common sources of organic leachables and metal components are the most common sources of inorganic leachables. Examples of common organic leachables can be seen in Table 1. Any component of the manufacturing equipment with direct contact with a liquid that eventually becomes part of the final product is a potential source of leachables. Examples of SUS and MUE components that can give rise to extractables include filters, hoses, bioreactor bags, connectors and filling needles. Manufacturing equipment that is not directly in contact with a liquid that enters the final product is unlikely to be a source of leachables. Leachables present a potential risk to the patient both from the toxicity of the leachable and from the possible negative impact upon stability and efficacy of the final product.
The manufacturers of drugs, biologics and biotherapeutics are required to evaluate the risk of leachables from SUS and MUE used in the manufacturing process. Many equipment vendors will provide extractables results for their components generated in many different model solvent systems that bracket the pH, polarity, and ionic strength of most aqueous based drug products. The vendor extractables testing is typically performed according to the “white papers” issued by the Bioprocess Systems Alliance (BPSA) and the BioPhorum Operations Group (BPOG). A scientific based assessment comparing the extractive power of the drug product that will be manufactured using the equipment to the vendors conditions of contact in the extractables testing has to be performed to demonstrate that the vendor extractables profiles were generated under “worst case” conditions. Any “gaps” identified in the correlation of the vendor extractables data to the conditions used in manufacturing can bead dressed utilizing a simulated-use extraction study. As part of the assessment, a justification can be made to exclude components of the manufacturing train from the simulated-use extraction study if there will be significant dilution of leachables or potential removal of the leachables during purification techniques (such asrecrystallization and diafiltration).
In a simulated-use extraction study, the components of the SUS or MUE are extracted with a model solvent or placebo under representative conditions of contact encountered during manufacturing. The sample extracts are analyzed by GC-MS, LC-MS and ICP-MS to identify all of the organic and inorganic. Any pre-treatment of the components that would be done during manufacturing (e.g. pro-active flushing of filters and tubing) should be done on the sample before the start of the simulated-use extraction study.
I. Simulated Use Extraction
A. Sample Extraction
In a simulated use extraction study, the extraction solvent is selected to closely mimic the drug product. The extraction conditions are usually static storage at the temperature intended for temperature for a minimum of two time points. The first time point is the intended routine time the individual component would be in contact with the product and the final time point would represent the longest allowable time the product would be in contact with the product.
B. Extractable Analysis
The sample extracts are analyzed by GC-MS,LC-MS and ICP-MS. The goal of these analysis is to identify as many extractables as possible and to semi-quantitatively determine the level of each extractable. Since the methods are designed to detect unknowns, these methods cannot be validated. Results from these analyses are reported as the amount of the extractable (usually in µg) per weight (usually in g) or surface area (usually in cm2) of the component.
C. Analytical Evaluation Threshold
At the completion of the extractables analysis, a list of extractables is generated. The challenge at this point is to only report extractables that present a toxicological risk. To evaluate the toxicity of each observed extractable, the safety concern threshold (SCT) is used.
The SCT is the absolute highest acceptable exposure of a patient to a leachable in drug product and is usually expressed in terms of µg of leachable per day. If an SCT is not known, the recommended SCT by the Product Quality Research Institute (PQRI) for a parenteral drug is 1.5 µg of each individual leachable per day (1). The PQRI selected this SCT as representing a threshold below which leachables would have negligible safety concerns from carcinogenic and non-carcinogenic toxic effects.
To apply the SCT to a given product, an analytical evaluation threshold (AET) is calculated based on the SCT of an individual leachable (usually in µg) per day, the number of doses of the drug product administered per day, the number of doses contained in the container closure system, and the volume of product in the container closure system . The AET is defined as follows:
The AET will have units of µg/mL of the product and can be converted to the sample extracts based upon the extraction conditions.
D. Interpretation of Results
If quality manufacturing equipment has been selected and the extraction conditions were appropriately selected, the number of extractables observed will usually be small. From the generated extractables profile,only the extractables above the AET present a risk to patient safety.
As is commonly observed, in some cases the levels of extractables will increase over time until it rises above the AET. If a time can be identified where the extractables levels are below the AET, the manufacturing process should be modified to limit the exposure time thus ensuring the extractable levels will stay below the AET in the final product. This is commonly sufficient to eliminate the risk from leachables from manufacturing components.
In rare cases, changes to the manufacturing process are not sufficient to reduce the risk from a specific extractable. In this case a toxicological assessment to determine a compound specific SC is recommended to fully evaluate the risk from the specific extractable.
Leachables present a unique challenge in assuring drug product safety and efficacy. The experimental approach presented represents a rational experimental approach to evaluate this risk. When properly executed and interpreted, a simulated use extraction can be used to evaluate and minimize the risk of leachable from manufacturing equipment.
The authors would like to thank Michael Ruberto of Material Needs Consulting for his contributions to this white paper.
1. “TheProduct Quality Research Institute (PQRI) Leachables and Extractables Working Group Initiatives for Parenteral and Ophthalmic Drug Product (PODP)”, PDA JPharm Sci and Tech 2013, 67 430-447