By definition, a sterile product is sterile if it doesn’t contain more than the defined limits for bacterial endotoxins and/or pyrogens, and if it is free of visible particles. To ensure this level of sterility, the manufacture of pharmaceutical products, and more precisely sterile preparations, is subject to special requirements by different regulations. This includes pharmacopoeias – collections of standards and quality specifications that apply to specific countries or regions – as well as guidelines that relate to Good Manufacturing Practices (GMPs).

Having published draft versions of European Commission GMP Annex 1 for Manufacturing of Sterile Products, the pharmaceutical industry is currently focused on a key principle of the sterility best practices for the manufacture of sterile products: Contamination Control Strategy (CCS).

Is CCS a new paradigm?

Yes and No. No because for the pharmaceutical industry contamination control is a key driver for the manufacture of sterile products with the objective of minimising contamination risks from microbial, pyrogen and particles sources. Yes, because contamination control should not be considered individually for each element (For example, process, premises, equipment, personnel, raw materials, components) but collectively – which is what appears to be happening now.

CCS as a concept is about holistically considering all potential risks of contaminations in order to do the right thing the first time for your product and your process. One example of taking a holistic approach is the frequency of environmental monitoring, which must be more frequent for open processes and less so for closed processes. Another example is seen with sterilisation or decontamination, with sterilisation carried out for all product contact surfaces and decontamination carried out for other surfaces to prevent the transmission of microbes from surface to product.

An effective CCS should include the following elements: personnel knowledge; the quality culture and pharmaceutical quality system; contamination controls; validation of controls and monitoring of controls. An effective CCS should be in continuous improvement mode, applying a life cycle approach with a periodical review with changes implemented as necessary.

Main sources of potential contamination

The development of the CCS requires access to all technical details and the assurance that personnel involved in this programme will have the necessary knowledge and information concerning the process and the product. This is in order to evaluate the potential sources and risks of microbial, pyrogen and particulate contaminations. For microbes, the main source of contamination is humans, which account for about 80% of all contaminations. The other contributing factors include the environment in which products are manufactured, water used in the process and raw materials.

Pyrogens, including bacterial endotoxins, are substances that can cause fever in humans. Bacterial endotoxins are lipopolysaccharides produced by gram-negative bacteria, generally waterborne microorganisms such as Escherichia coli. These microorganisms are known to generate biofilms.

Concerning particulate contamination, particles can be visible if their size is at least 50μm, or sub-visible particles if they are unable to be observed by the naked eye.

Barriers and isolators

The manufacture of sterile products should be carried out in an appropriate environment that ensures the absence of microbes, endotoxins/pyrogens and particulates risk for the process, the products and the patient. That is why the pharmaceutical industry has, since the past decade, moved to switch from conventional clean rooms to barrier technologies that include the use of isolators to secure the environmental conditions of manufacturing sterile products, and specifically those that cannot be terminally sterilised.

Isolator technology is designed to avoid and prevent the ingress of contamination from the surrounding environment, including the absence of direct contact of the operators to the inside isolator barrier (Grade A zone).

Aseptic processing simulation

If a product cannot be sterilised in its final container, the preparation should be sterilised by filtration and the filling operations should be performed in compliance with aseptic processing best practices. The objective is to identify, assess, appropriately control and minimise the risk of microbes, pyrogens and particulates contaminations. The effectiveness of aseptic processing operations should be initially and periodically verified, including the performance of aseptic processing simulation (APS) using a nutrient medium or a surrogate in place of the products.

“Analytical methods are applied to evaluate both viable particulate contamination for the air and surfaces and non-viable particulate contamination of the air.”

The APS procedure is complex to prepare and should consider some key points. Firstly, the simulation of manufacturing activities is performed as closely as possible to the routine aseptic manufacturing process. Further, APS should include all critical steps and personnel interventions known to occur during routine production (inherent and corrective interventions) in a manner and frequency similar to a routine aseptic process supported by a risk-based approach.

APS protocol should also identify the worst-case conditions and parameters of the filling line with representative sizes of combinations of container/ closure systems, line speed, filled volume, growth conditions of the microorganisms (selection of the medium, incubation temperature and time), holding times from the routine, duration of the filling operations, number of shifts and campaign period.

At the initial validation, at least three consecutive APS satisfactory runs should be done; then, periodically, a revalidation should be performed, generally every six months. To note, the number of filled units should be sufficient to effectively simulate all representative activities of the aseptic process in compliance with the CCS. After the incubation step, each filled unit should be visually inspected by qualified personnel – the acceptance criterion for APS is absence of microbial growth. At the end of this APS process, the reconciliation of the total number of units from filling operations to final inspection should be evaluated.

Environmental monitoring programme

Environmental monitoring for clean rooms and clean air equipment should consider viable and non-viable particulates contamination and other physical parameters such as temperature, relative humidity and pressure differentials between rooms. This environmental monitoring includes a sampling plan programme for viable and non-viable particulates with three key elements. Firstly, the definition and justification of the sample locations are supported by a risk-based approach in compliance with the CCS. Then the frequency of the samples is defined and justified according to the risk of contamination. After this, analytical methods are applied to evaluate both viable particulate contamination for the air and surfaces and non-viable particulate contamination of the air. The results of this environmental monitoring programme should be evaluated by comparison to action limits and alert levels. The data should also be trended, and when excursions are met, corrective actions and preventive actions should be defined in the objective to minimise the risk of contamination.

Challenge for the future

Environmental monitoring programmes associated with all other parameters and information acquired throughout the manufacture of each batch of sterile processes will generate huge amounts of data. The evaluation and trending of all such data are key challenges for the release of each batch of sterile products for the safety of the patients. To succeed in this objective, a strategy of interpretation using algorithms involving artificial intelligence and a process of archiving these data using data centres must be defined, organised and secured in advance.

Particles exist in huge diversity; they can be classified in the three following categories according to their sources, characterisation, and properties:

  • Extrinsic particles are particles that are foreign to the manufacturing processes and could involve high risks for sterility of the manufactured products.
  • Intrinsic particles may come from the manufacturing process including production equipment and primary packaging materials.
  • Inherent particles are particles related to the dosage form of the product and may be acceptable when their presence is measured, characterised, and determined to be part of the clinical profile.

The key challenges using isolator technology are the following:

  • Isolator design with closed isolator or open isolator and air treatment system including HEPA or ULPA filers
  • Cleaning, disinfection and decontamination using Vapor Hydrogen Peroxide system (VHP)
  • Interventions and manipulation of the operators using gloves/sleeves systems
  • Management of the transfers inside/outside the isolator for the sterile components (for example primary packaging with container and closure systems), the environmental monitoring devices including media plates and swabs
  • Environmental monitoring program inside isolator and for the surrounding area
  • Maintenance activities that present the minimum contamination risk.