An Economic Analysis of Single-Use Tangential Flow Filtration for Biopharmaceutical Applications - Single-use TFF offers the greatest savings in clinical and contract manufacturing, where the scale is


An Economic Analysis of Single-Use Tangential Flow Filtration for Biopharmaceutical Applications
Single-use TFF offers the greatest savings in clinical and contract manufacturing, where the scale is low and changeovers are frequent.

BioPharm International Supplements

Process Example: Single-Use TFF Cassettes

The following economic analysis of an ultrafiltration process demonstrates the savings that can be achieved when using single-use filtration cassettes instead of reusable ones. The analysis takes into consideration the cost of consumables, such as water, CIP solutions, and buffer solutions, as well as labor and overhead costs associated with running a TFF process in a cGMP process. These costs can vary from site to site, so individual site costs can be input to create a customized model.

The membrane surface area of the filtration cassettes chosen for this model was 2.5 m2, an area sufficient to process batch sizes up to approximately 1,000 L. This amount of membrane surface area typically would be used for one ultrafiltration process step in clinical-scale production. In clinical-scale and contract manufacturing, often only four to six batches of product are processed per campaign and then the reusable cassettes are either placed in storage or discarded. This scenario is represented in this particular economic analysis.

Consumables, including the filtration cassettes, buffers, water, and CIP solutions used during the process, also are accounted for in this model.

Cassette costs vary from different manufactures, so an average cost of the reusable cassettes was used. Typically reusable cassettes cost approximately $3,600 per m2. By way of comparison, single-use cassettes are approximately 20% of the cost of reusable cassettes or approximately $800 per m2.

In addition to the cassettes, various buffer solutions are used for the filtration process. Some of the buffers are used for the membrane equilibration and diafiltration operations. More importantly, with reusable TFF, a significant amount of these buffers are used for the CIP portion of the process. In addition to these CIP solutions, purified water is used for flushing the reusable cassettes. These CIP solutions and the need for purified water for flushing the cassettes are eliminated when single-use cassettes are used.

Lastly, labor and overhead costs are considered. These labor and overhead costs (also referred to as factory overhead, factory burden, and manufacturing support costs) refer to both direct and indirect factory-related costs that are incurred when the product is manufactured. Along with costs such as direct material, the cost of labor and overhead must be assigned to each batch produced so that the cost of goods are valued and reported accurately. The overhead includes such things as the electricity used to operate the factory equipment, depreciation on the factory equipment and building, factory supplies, and factory personnel not included as direct labor. Once these costs have been tabulated, they have a significant impact on the cost of the ultrafiltration process. Typical labor and overhead costs for a cGMP approved manufacturing facility range from $2,000 to $3,500 per hour in the United States. In our model, we assumed this cost to be $3,500 per hour.

Table 1. Labor and facility costs, per batch and per campaign (assuming five batches per campaign) for reusable and single-use tangential flow filitration steps, assuming an overhead cost of $3,500 per hour
As mentioned above, implementing single-use cassettes can eliminate many of the non-value–added steps of pre-use and post-use CIP and as a result the overall time of the ultrafiltration process is reduced. As a result, there is increased productivity and the overall cost of manufacturing is reduced. This increase in productivity can be illustrated by tabulating the labor and overhead costs associated with each process step and calculating the total cost savings per batch. Table 1 lists each of the ten primary activities associated with a typical reusable ultrafiltration process. Table 1 also shows the reduced number of process steps needed for a single-use ultrafiltration process. That 2.4-h reduction in processing times translates into total savings for the process of approximately $8,400 per batch.

Table 2. Membrane costs
After identifying the costs for membranes, water, CIP solutions, and buffer, as shown in Tables 2 and 3, we compare these costs in Table 4. Although the cost of cassettes is higher in the single-use model, these higher membrane costs are more than offset by the reduction of costs associated with water and buffer usage and overhead. Over the course of a five-run campaign, the accumulated costs saving is significant in favor of single-use TFF. Figure 4 provides a graphical depiction of this overall cost comparison of reusable and single-use TFF.

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