THE DEVELOPMENT AND MANUFACTURE OF BIOLOGICAL PRODUCTS USING BFS
BFS steps in biological manufacturing
Fill–finish operations of biological drug products, particularly proteins or monoclonal antibodies, usually begin with drug
substance (or concentrated bulk) supplied either refrigerated at 2–8 °C for temporary storage, or frozen at <–20 °C for extended
storage. The drug substance is thawed, if necessary, at a defined temperature and process. If the drug substance has a different
concentration from the final drug product, a formulation buffer can be added and mixed together with the drug substance in
a mixing tank, to reach the target concentration as final drug product. The solution is then transferred into a holding tank
through a filter to reduce bioburden level. The holding tank containing formulated product can be used to store the product
for an extended period of time to accommodate manufacturing scheduling. These operation steps, including thawing, dilution,
mixing, and filtration are typically conducted in a Grade C area. Figure 2 illustrates the process flow.
Figure 2: The blow–fill–seal process in the context of biological manufacturing.
Most parts of the BFS machine are located in a Grade C room; only the filling cabinet is controlled under a Grade A condition.
Time-pressure filling, where a pinch valve is used to control the fill volume, is often used in the filling operation. The
flow rate is determined by the pressure applied to the liquid reservoir (or surge tank), and the pinch valve opening time
determines the final fill volume. During the filling process, solution sterilization is achieved by sterilizing-grade filters.
The connection of the BFS machine with filling needles, surge tank, and sterilizing filter usually takes place in a Grade
C environment. The BFS machine is first assembled and cleaned through clean-in-place (CIP) procedures. It then gets connected
to the sterilizing filter, and the entire connection is sterilized under a validated steam-in-place (SIP) cycle, from the
filling needle, all the way to the point of connection with the product tank.
Aseptic processing requires contamination control and sterilization of three main aspects: drug-product solution, primary
container components, and operation environment. The sterilization method for drug product solution in a BFS process is similar
to a conventional fill–finish process, where typical sterilizing grade filters are used. Unlike the component processing steps
in the conventional fill–finish process (i.e., washing, depyrogenation, and siliconization of vials, syringes, and stoppers),
the primary container is formed in the BFS process, and the molding of plastic resin at elevated temperature provides a container
"free" of viable microorganisms and with acceptable endotoxin levels. The ability for a BFS extrusion process to yield product
with acceptable quality has been demonstrated by controlled challenges studies, where LDPE granulates were contaminated with
characterized levels of bacteria spores and endotoxins, then pressessed through a BFS machine using Tropton Soy Broth and
Water for Injection as the filling media (4). Higher fractions of contaminated units were observed with increased challenge
level (or amount of spores and endotoxin in the plastic granulates). The above study demonstrated it is critical to establish
appropriate acceptance limits for bioburden and endotoxin levels on plastic granulates to assure final product quality.
The overall extrusion and molding process of the BFS operation is conducted in a Grade C area. However, the air shower for
the filling shroud of the BFS machine should provide a Grade A condition. European Union guidelines state that, "The condition
should comply with the viable and nonviable limits at rest and viable limit only when in operation" (5). There is potential
risk for airborne contamination before the mold moves to the filling shroud area, where the air shower maintains a Grade A
environment. Recent studies have shown that most of the airborne contamination occurs between the time when the top is cut
from molded containers and when they pass under the air shower (6). The microbial and particulate controls are highly equipment
and site specific. Therefore, a media fill has to be conducted for each specific machine, process, or container type. A recent
survey of the BFS industry provides an excellent overview of the current practices in aseptic BFS technology, showing that
the BFS process has a much lower frequency (about one-tenth) of contaminated media fills compared with conventional processes