Keep Formulations Clean
Testing for leachables and extractables is an absolute necessity for drug manufacturersIn an era of increasing regulation of products, devices, and ingredients, the testing for and identification of leachables and extractables in the drug-manufacturing process is more vital than ever.
Extractables are chemical entities released from a single-use manufacturing or storage component under harsh conditions such as high temperature, strong solvents, or other conditions such as a long exposure time. Leachables are chemical compounds that can be released from, or leached off, a single-use component such as a filter or a storage container into a final drug product when that product has been processed or stored under normal conditions.
The identity of the leachable or extractable depends on the raw materials used in the manufacture of the single-use component and the raw materials used in the pharmaceutical processing of the drug formulation. For example, in polycarbonate bottles, there is a concern about the presence of the leachable Bisphenol A (BPA) leaching into the final drug product.
Extractables derive from any of the plastic components used in the workflow. In general, extractable species fall into three main groups: unreacted or partially reacted monomer, resin additives, and film-processing aids. According to Richard Bhella, product manager for ATMI LifeSciences in Bloomington, Minn., an unreacted monomer is a function of the polymer material and its manufacturing process, so selecting a resin for its ultimate molecular weight range uniformity and low levels of unreacted monomer is important.
Resin additives are typically present to stabilize the base resin against degradation from environmental exposure (antioxidants, UV stabilizers, etc.) and generally do more good than harm. These additives represent the bulk of the leachable and extractable (L&E) species encountered in a typical bioprocess film, but normally at extremely low levels (in parts per billion) and are thus generally tolerable. Lastly, film processing aids—added to allow faster or more efficient film extrusion—are the most common L&E risk present in disposables and thus their use should be minimized.
“The type and quantity of chemicals that can become leached or extracted from a polymer film depend substantially on the type and purity of the resin used to make the contact film,” says Bhella. For example, folder films with ethylene vinyl acetate contact layer produces significantly higher levels of L&E than the newer polyethylene films.
Testing for L&ETesting can be performed by either the disposables manufacturer or the end user. “When we talk to customers that purchased disposable components from a vendor without receiving extractables or leachables data from that vendor, we always recommend that they, the customer, gets the testing done,” says Laura Okhio, director of validation services for Sartorius Stedim North America in Atlanta, Ga. Most users prefer to have a company such as Sartorius Stedim perform the testing.
Sartorius Stedim performs testing for leachables in the following way: Each study is conducted with a negative (or “blank”) control exposed to the same extraction conditions as the sample and provides the basis of comparison for the study. The blank is the drug formulation that has not been in contact with the single-use component. Sartorius Stedim performs an extraction for leachables under controlled time and temperature conditions. Then they perform the analysis to make the comparison between the extract and the blank.
“Identification and quantification of L&E species is not particularly challenging, but it does involve the use of a variety of complex and expensive analytical instrumentation; gas and liquid chromatography, mass spectrometry etc. Thus, for most end-users, testing will be outsourced,” says Bhella.
According to Sartorius Stedim’s E&L Strategy Guide, the analytical tools to detect, quantify, and identify extractables and leachables are HPLC-UV and GC-MS. When using HPLC-UV, the detectable compounds are UV active, non/semi-volatiles, hydrophobic, and hydrophilic (unknowns). When GC-MS is used for analysis, they are semi-volatile, volatile, UV, and non-UV active compounds (unknowns). “Other analytical techniques which are non-specific can be applied such as a measurement of the Non-Volatile Residue (NVR) or Total Organic Carbon (TOC). These techniques can provide an overall mass of extractables/leachables, but do not provide specific compound information,” says Okhio.
In their strategy guide, Sartorius Stedim also outlines the procedures for their extractables and leachables studies. For their extractables study, solvents are chosen that mimic those used throughout a customers’ bioprocessing protocol or their product formulation. From the guide, “the test extraction is conducted using exaggerated conditions of time and temperature. For example, an aqueous process/product formulation could be bracketed using water and ethanol at the exaggerated extraction conditions of 72 hours at 50 degrees C. Overall, extractables are conducted with simple extraction media such as low molecular weight alcohol, high pH buffers, low pH buffers, or pure organic solvents.” For the leachables study, the actual process stream solution or final product formulation is used to detect and identify leachables. Again, according to the guide, “the test extraction is conducted using conditions that mimic and target worst-case process/actual parameters.”
According to Sartorius Stedim, leachables studies should be conducted when one or more of the following conditions are met:
- The extractables testing does not sufficiently bracket the process conditions.
- The formulation is unusually complex.
- Liposomes capture organic extractables.
- Any formulation with more than 10% to 20% organic content, such as polyethylene glycol.
- When detected extractables have the known potential to cause safety or efficacy issues (e.g., BPA)
- When the test article is not used in the same configuration as was used for the extractables test.
- When there is a real or perceived need for direct data or there is high regulatory concern.
Once the results of analysis are received, “if we find [mass spectrometric] peaks that are in the extract but not in the blank, we call that a leachable,” says Okhio. The extractable or leachable to be identified depends on the location of the suspect component relative to the position of the final formulation. The idea here is to ensure that the final product, after coming in contact with all the components (stoppers, stirrers, bottles, et cetera) in the workflow, is free of extractables and leachables that could negatively impact the formulation. “Most of our customers do not perform testing for extractables and leachables at the laboratory scale. They wait until phase two or phase three,” says Okhio.
Why Testing is NecessaryTesting for leachables in the final drug formulation is necessary to ensure that the interaction between the single-use component and the drug formulation does not result in any toxic chemical entities, i.e., it is necessary to ensure that the drug formulation is safe for humans, especially in regards to drugs that are inhaled or injected.
“Whether or not a leachable or extractable is toxic depends on the structure of the materials. It depends on the solution in contact with the components,” says Okhio. Like most disposables manufacturers, Sartorius Stedim does not make the assessment of toxicity but it does give the identity of the leachable or extractable. It is then the end-users’ job to consult with a toxicologist to determine if the amount of that chemical is toxic in their drug formulation. And although there are no specific FDA guidelines for extractables and leachables there are organizations such as the PDA and the BPSA that provide recommendations on how to test for them.
“The guidance from the regulatory authorities can sometimes be maddeningly vague and typically relates to the likely levels in the final drug product dose,” says Bhella. “Thus, a risk-based assessment protocol is more appropriate than a blanket threshold concentration.”
One of the leading advisers on L&E industry standards is BioProcess Systems Alliance, an industry body representing manufacturers and users of bioprocess single-use technologies. “Fortunately, the industry and regulators are starting to realize that the L&E profile of medical-grade polyethylene resins is relatively comparable. As the body of data on these films continues to grow, the trend will be towards more and more comfort with their interchangeability,” says Bhella.
Finally, Bhella notes that ATMI LifeSciences, in response to the industry’s concern with L&E, now offers all their single-use bags made from ATMI’s “universal” TK8 bioprocess film. The goal of the new offering is to use the same contact material in all applications, streamlining the film validation process as much as possible.
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