Systematic Evaluation of Single-Use Systems Using Process Simulation Tools - Simulation tools can reveal whether disposables will be economical even after scale-up. - BioPharm International


Systematic Evaluation of Single-Use Systems Using Process Simulation Tools
Simulation tools can reveal whether disposables will be economical even after scale-up.

BioPharm International Supplements

Table 3. Cost-of-goods comparison between the two alternatives
The two options were also compared from an economic perspective. Table 3 and Figure 4 display the breakdown of operating costs for both options and their respective unit production costs. The unit production cost for the disposables option is 24% lower than that of the stainless-steel option ($317/g versus $415/g). The facility-dependent cost, which mainly accounts for the depreciation and maintenance of the facility, is $27 million/year for the single-use option versus $38 million/year for the stainless steel option. The cost of raw materials, which includes the cost of cleaning materials, is also considerably higher for the stainless-steel case. On the other hand, the consumables cost is higher in the case of disposables ($8 million/year versus $5 million/year).

Figure 4
For the base case comparison, it was assumed that both plants manufacture the same product throughout the year (80 batches per year). If frequent product changeovers are required, which is common for clinical manufacturing facilities, then the number of batches per year will go down and the facility-dependent cost (per unit of product) will increase. Because single-use systems facilitate product changeovers (because of reduced validation), the advantages of single-use systems will be greater under those conditions.

Figure 5
For the 2,000-L production bioreactor scale, the disposables option is clearly the preferred alternative. The advantages of the disposables option gradually diminish as the scale increases (Figure 5). For the scale of 8,000 L, the options are roughly equivalent from a cost-of-goods point of view.

Figure 6
The analysis reveals that the single-use systems option for buffer preparation and holding is clearly more economical at smaller scales (under 8,000 L of production bioreactor scale). The main reason is the significantly lower facility-dependent and material costs. The facility-dependent cost is lower in the case of disposables because of the reduced requirement for stainless-steel vessels, CIP skids, piping infrastructure, and utility systems. The cost of materials is lower because of reduced demand for cleaning materials. For scales larger than 8,000 L (of production bioreactor working volume), the stainless-steel option starts to become more attractive. At that scale the number of buffer bags that need to be prepared and transported to the point of use becomes impractically high (Figure 6). The volume of the hold bags is limited to 200 L because they have to be manually transported on a cart to the point of consumption. In addition, multiple buffer preparation skids are required to avoid bottlenecks associated with preparing buffers, which in turn affects the capital investment. Labor costs are also considerably increased because more operators are required to prepare and transport the bags; labor demand for the stainless-steel case does not change much with scale. It is important to note, however, that the 8,000-L scale is not a universal turning point for MAb processes. Increased product titers will most likely result in lower turning points because they are equivalent to higher batch throughputs.

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