Best Practices for Sterility Assurance in Fill/Finish Operations

Published on: 
BioPharm International, BioPharm International-11-01-2015, Volume 28, Issue 11
Pages: 14–19

Two experts discuss best practices to achieve acceptable sterility assurance levels for aseptically filled products.

Whether outsourcing aseptic techniques to a third party, or performing these tasks in an academic setting or in an in-house laboratory, certain tools, technologies, and standard operating procedures are necessary to ensure sterility across settings. Because many biologics cannot be terminally sterilized, isolators and restricted access barrier systems (RABS) are typically the go-to tools manufacturers use to ensure product sterility.

To gain some insight into how to best prepare sterile, parenteral products, BioPharm International spoke to experts in both the theory and the practice of sterile drug preparation. Specifically, the publication spoke to Bivash Mandal, PhD, a senior research specialist at the Plough Center for Sterile Drug Delivery Systems in the University of Tennessee Health Science Center, and Bernd Stauss, senior vice-president of production/engineering at Vetter Pharma-Fertigung GmbH & Co.

The Plough Center for Sterile Drug Delivery Systems announced in August 2015 that it is installing three PODs from G-CON Manufacturing in a new facility on campus to manufacture drugs for sponsors and train professionals on cGMPs for the large-scale production of pharmaceuticals (1). Although the location currently has the capacity to manufacture small-volume parenteral preparations for clinical investigation, the facility expansion, which began in September 2015, will allow the university to manufacture drugs for preclinical and clinical trials. The PODs are slated to be up and running by 2016.

Vetter is an outsourcing company that has helped guide dozens of product approvals for biopharmaceutical compounds and specializes in the commercial filling and packaging of parenteral drugs. In the past few years, Vetter has focused on innovation in the field, combining the advantages of isolators and RABS to create a new approach in sterility assurance, which the company calls its “Improved RABS Concept.” The technique features an accelerated process cycle and an automated decontamination function for increased operational excellence in aseptic processes (2).

Equipment TrendsBioPharm: What are the trends in the use of RABS and isolators? Is use of this type of equipment the best way to ensure the sterility of one’s fill/finish processes?

Mandal: Aseptic processing is a complex manufacturing technology that can be achieved by using aseptic cleanrooms (manned human-scale cleanrooms), isolators/restricted access barrier systems (RABS), or both. As far as the industrial trends are concerned, some firms have taken a mix-and-match approach. RABS and isolators can be used in the manufacture of biologics, including vaccines, gene therapies, and protein-based drugs. Often, biologic products are preservative-free, contain growth media, and are easily susceptible to contamination. Another area that demands the use of RABS and isolators is the manufacture of sterile drug products with toxic, cytotoxic, and highly potent molecules, which require stringent barriers to protect personnel who are handling these materials. In general, RABS and isolators are being used for smaller-volume and high-value pharmaceuticals. The benefit/cost balance has to be considered when discussing the use of barriers: RABS and isolators come with a high price tag and are associated with additional expenses related to the operation of a cleanroom, such as energy costs, operating costs, testing costs, and gown costs.

Because it has been established that the personnel working in cleanrooms can be a major source of contamination, RABS and isolators are preferred as a means of a physical barrier to separate people from filling processes. According to FDA guidance on aseptic processing, isolators and closed RABS are superior in their ability to control contamination and reduce validation workload. Operators must use these advanced technologies with caution because the use of RABS and isolators alone does not guarantee the sterility of products. In both isolators and RABS, for instance, operators use glove ports, and glove ports need to be inspected on a daily basis. Moreover, gloves are considered a primary route of contamination, and they are a common cause of failure in isolator technology. Complete automation and use of robotic technology in conjunction with isolators and RABS should be developed to eliminate the human interventions that are performed using glove/sleeve assemblies.

Stauss: There are two distinct technologies dominating the fill/finish process: isolators and RABS. Each technology has its advantages. With isolator technology, the processing takes place in systems that are entirely shut off from the outside environment. As it pertains to sterility assurance levels (SAL), isolators are often considered the best solution due to the automatic decontamination processes involved. However, isolators need extensive decontamination and preparation processes following a batch to enable a safe change in product.

RABS technology also achieves the SAL currently required by regulatory authorities. With this technology, the physical barriers of a production plant are limited; a RABS requires installation in a higher-class environment (at least ISO 7, with the RABS located in an ISO 5 area). Conversely, this system provides flexibility and high-capacity utilization for multi-product filling lines; this is a reason why RABS are often found at CDMOs [contract development and manufacturing organizations]. When choosing between isolator and RABS technology, each company has to make the decision that best fits their production situation and needs.

BioPharm: What equipment is common for those performing fill/finish operations?

Mandal: For fill/finish operations, liquid-filling equipment (manual/semiautomatic/automatic), peristaltic pumps, filtration apparatuses, a lyophilizer (if required), a vial/ampoule sealer/crimper (semiautomatic/automatic), and a biosafety cabinet (hood) are required. During fill/finish operations, it is also required to monitor the environmental air quality by passive sampling using settling plates and active sampling using a centrifugal sampler and an impactor-type sampler. A laser particle counter can monitor the total particulate count of the environmental air.



Quality MeasurementsBioPharm: What have been some common performance gaps when it comes to environmental monitoring?

Mandal: Some of the common performance gaps in environmental monitoring include not following standard operating procedures, not monitoring in all aseptic processing areas, inadequate corrective actions, not responding in a timely fashion to out-of-limit results, inadequate personnel training, failure to validate the cleaning and sanitization procedures, failure to trend environmental monitoring data, failure to identify common microorganisms, and inadequate documentation of deviations.

BioPharm: How are aseptically manufactured drug products best evaluated for their sterility?

Stauss: Proving the sterility of manufactured drug products is crucial to a drug manufacturer. In the first step, the design of the applied primary packaging materials needs to meet integrity requirements. Successful product integrity testing using deterministic or probabilistic methods is the basis for enabling sterility in manufactured drug products. After the integrity of the package design is established, incoming packaging materials are routinely tested to ensure they meet specifications.

Equipment surfaces that come into contact with sterilized drug product or sterilized primary packaging materials, as well as any crucial equipment in the cleanroom, needs to be sterilized by using validated sterilization methods. Moist-heat and dry-heat sterilization are the most commonly used sterilization methods. Furthermore, the aseptic processing operations need to be tested for their ability to produce sterile products via process simulations (media fill). During media fill, microbiological growth medium is exposed to product contact surfaces to simulate the exposure that the product may undergo during manufacturing. The sealed containers filled with the medium are then incubated at defined temperatures to detect microbial contamination.

During manufacturing, varying controls like bioburden and endoburden testing of product and filter integrity testing are performed. Another important aspect is the environmental monitoring of the surroundings. Before release of a batch, a sterility test in an isolator is performed to further demonstrate sterility of the filled batch.


Mandal: Aseptically manufactured drugs must be sterile, pyrogen-free, particulate-free, stable, and isotonic. Sterility testing must be conducted on every batch of a product that is manufactured. FDA consistently emphasizes that sterility testing is to remain a current good manufacturing practice. Chapter <71> of the United States Pharmacopeia (USP) states that sterility tests on parenteral dosage forms are not intended to be used as a single criterion for the acceptability of a product (3). Sterility assurance is achieved primarily by the validation of the sterilization processes and the aseptic processing procedures.

Ideally, every vial/syringe/ampoule manufactured must be tested for its sterility. Because sterility testing is a destructive process, however, testing each individual unit is not possible. USP <71> provides guidance for the minimum number of articles that need to be tested from each manufactured batch.

The sterility test can be performed by two different methods: by the direct inoculation method or by the membrane filtration method. In the direct inoculation method, a predetermined amount of product is added directly to the medium under aseptic conditions and incubated. In the membrane filtration method, the contents of the product to be tested are filtered through an appropriate-sized filter, such that if any microorganisms were to be present, they would be retained on the filter. This filter is then washed with specified solutions to remove any retained product, and finally, the filter is incubated with medium at appropriate conditions for at least 14 days.

Two different media must be used for testing, irrespective of the testing method used. Fluid thioglycollate medium (FTM) is used to culture primarily anaerobic microorganisms, although it can support the growth of aerobic microorganisms as well. Trypticase soy broth (TSB), also called the soybean casein digest medium, is used to test for the presence of fungi and aerobic microorganisms. If a particular drug product inhibits the growth of bacteria, such as is the case with beta-lactam antibiotics, the formulation of the medium can be modified to include certain agents that can deactivate the antibiotics, such as beta-lactamase. Alternatively, the membrane filtration method can be used.

A failure of the sterility test is indicated by a growth in one or more of the incubated samples. There is no such thing as a false positive in the sterility testing of an aseptically manufactured product. A comprehensive written investigation follows, which includes identification of the bacteria, specific conclusions, and corrective actions. A sterility test that is positive may be indicative of production, personnel, or laboratory problems. The most commonly found microorganisms in sterility test failures include, but are not limited to: Staphylococcus aureusPseudomonas aeruginosaEscherichia coliEnterobacter aerogenesNeisseria gonorrhoeaeAspergillus niger, and Candida albicans.



Fill/Finish best practicesBioPharm: Can you describe some best practices for decontamination?

Stauss: The goal of a service provider to the biopharmaceutical industry is to provide its customers with reliable and efficient aseptic production processes, which are supported by safe and effective cleaning and decontamination processes. 

Automated decontamination of RABS reduces downtime, increases capacity utilization, and improves overall equipment effectiveness. Prior to the start of the decontamination process, format parts are cleaned offline, in full, and automatically to remove particles, silicon, or residues, for example. This automated cleaning process represents an important advantage as compared to isolators, where a manual cleaning process is normally applied.

Mandal: As an alternative to formaldehyde-based sterilization, vaporized hydrogen peroxide (VHP) was introduced in the mid-1980s to clean and decontaminate equipment and machinery in the healthcare industry. Since then, the use of VHP has been steadily increasing due to the following advantages:

  • Efficacy in rapid decontamination of machines at ambient temperatures and low concentrations

  • Strong history of use and positive efficacy data on a broad range of bacteria, fungus, spores, and viruses

  • Proven efficacy testing with biological indicators and chemical indictors

  • Ability to kill resistant spores

  • Use within a controlled process with real-time concentration monitoring

  • No toxic byproducts with its use (VHP is a green solution)

  • Associated with less exposure risk to personnel and products outside of a decontamination zone

  • A favorable safety profile (Typical concentrations used are 150-700 ppm as compared with formaldehyde [8000-10000 ppm] and chlorine dioxide 350-1500 ppm)

  • No lengthy aeration period

  • No residue

  • A strong material and component compatibility profile

  • Registered by the Environmental Protection Agency (EPA)

  • Approved by FDA.

Case studiesBioPharm: Can you describe some of your most challenging fill/finish projects and what you did to overcome obstacles that were presented?

Mandal: The Plough facility at the University of Tennessee has been manufacturing small-scale batches for preclinical and Phase I clinical trials for sponsors. We have been using an aseptic cleanroom with manual intervention and semiautomatic filling lines. Most of the challenges we have faced were mechanical or instrument-oriented.

One of the projects (manufacture of a sterile solution of polysaccharide) had issues with the filling line clogging when the filling operation was halted to switch personnel. The formulated product was good, however, and was still within acceptable limits of viscosity. Upon investigation, we found that residual solution-which is in contact with the filling needle tips-evaporated in the laminar flow. We were unable to remove the clot with high pressure. The problem was solved by running the entire fill continuously, without interruptions.

Another challenge was with a project focused on a parenteral that was made up of an oily solution. The process required us to overlay nitrogen to protect the product from oxidation. After stoppering the product, the vial stopper eventually became pushed out in time. The solution to the problem was to crimp the vial in a reasonable amount of time after stoppering.

Recently, we had a project on the preparation and aseptic fill/finish of a liposomal product containing a cytotoxic chemotherapeutic. Liposomal products are notoriously challenging fill/finish projects because of issues with filtration, drug loading, filter compatibility, and particle-size distribution. Compatibility of the filter was an important issue due to the drug being adsorbed in the filter. The proper control of the filtration pressure was crucial, because there is an increased occurrence of drug loss from liposomes during filtration at higher pressures.

Additionally, the containment of the cytotoxic chemotherapeutic proved challenging. Special procedures should be adopted to deactivate the drug contaminated materials after fill/finish. Cleaning validation of the equipment should be conducted in order to obviate cross-contamination.

Stauss: Based on our day-to-day experiences in customer projects, we see the overall market is increasingly becoming more challenging, particularly in areas such as:

  • An increase in high-value products in smaller batch sizes

  • The continuous increase in regulatory requirements, including anticounterfeiting activities

  • Ever-more complex supply chains on the customer side, which have resulted in more complicated requests for CDMOs.

High-value products are often based on complex compounds. They demand high accuracy on the filling line and have an increased sensitivity to manufacturing processes and environmental conditions. A good example of a difficult fill/finish project is the handling of a highly sensitive API that requires very small fill volume in a syringe. Small filling volumes in such circumstances create significant demands on all production areas, including process design, technical equipment, and packaging material. This, in turn, creates high demands on the operating staff. In such cases, packaging material and processes need to be adapted to meet the requirements of a product. Using the correct application technique of the silicone coating on a syringe is a good example of a common packaging challenge.

Comprehensive project management is necessary to handle such a project successfully, taking into consideration the needs of both the product and the customer. To proactively enable a successful product launch, every potential impediment to the best outcome in fulfilling product requirements--including manufacturing processes, use of technical equipment, and proper staffing, to name a few-must be taken into account during the project phase.

1. The University of Tennessee Health Science Center, “New Plough Center for Sterile Drug Delivery Systems to Expand UTHSC’s National and Global Position as a Pharmaceutical Manufacturer,” Press Release, accessed Oct. 13, 2015.
2. Vetter, “Vetter Embarks on a 300 Million Euro Investment Strategy for Further Development to its Manufacturing Sites and to Make Available Additional Manufacturing Capacities," Press Release, accessed Oct. 13, 2015.
3. USP, USP General Chapter <71>, “Sterility Tests,” USP 29–NF 24 (US Pharmacopeial Convention, Rockville, MD, 2006).

Article DetailsBioPharm International
Vol. 28, No. 11
Pages: 14–19

When referring to this article, please cite it as R. Hernandez, "Best Practices for Sterility Assurance in Fill/Finish Operations," BioPharm International 28 (11) 2015.