Figure 1 illustrates the two options that will be examined in this economic analysis. Option 1 involves a three-unit operation
harvest process: centrifugation, followed by depth filtration, and completed with a concentration and buffer exchange via
tangential flow ultrafiltration–diafiltration (UF–DF). Option 2 involves a two-unit operation process: microfiltration followed
by a concentration and buffer exchange via tangential flow filtration (UF–DF). Table 1 presents a comparison of process performance
under the two options. Under optimal conditions, both options can deliver the desired product recovery (> 80%), harvest time
(<15 hours including sequential UF–DF), and clarification (< 6 NTU). In this study, we perform a cost comparison of these
options under different scenarios, presented in Table 2. Scenarios 1 and 2 involve cost estimation with new equipment but
without discounting for depreciation. These scenarios describe what happens when a company needs to buy all of the processing
equipment and is not likely to be able to use it for other products. An example would be a small company with a single product
that is planning to make a few lots of a product for clinical trials. The use of disposables is examined in scenario 2. Scenarios
3 and 4 involve cost estimation with new equipment and with discounting for depreciation. These are more typical scenarios,
where a company has several products in its pipeline, and will utilize the equipment, with possible minor modifications, for
other product(s). Examples of these would be most medium and large biotech companies and contract manufacturing organizations.
Table 1. Comparison of process performance for option 1 and option 2. Adapted from reference 10.
The following assumptions were undertaken for the economic analysis:
1. Since both of the options described above incorporate a UF–DF unit operation using the same type and number of membranes,
this step is not included in the cost comparison.
Table 2. Different scenarios analyzed in the economic comparison
2. Raw material costs include consumables and are obtained from vendors. It is assumed that the depth filter is single use
and that the microfiltration media can be recycled for 10 cycles. The reuse number is assumed to be low as the feed material
for the microfiltration step is very crude and for our application resulted in significant membrane fouling.
3. Purified water (PW), clean steam, and process air are considered utilities, and are included in the cost of operating the
facility. The facility cost also includes the cost of labor and other costs that are incurred to run the facility.
4. For estimating capital cost, an annual discount rate of 10% is assumed for all equipment (assumes a 10-year equipment life).11 Capital cost also includes the cost for commissioning new equipment, and validation.
RESULTS AND DISCUSSIONS
Scenario 1: As mentioned earlier, this scenario represents a situation in which a small biopharmaceutical company plans to conduct a
manufacturing campaign for a single product. The equipment cost is not discounted for the depreciation. Figure 2 shows a comparison
of the different cost components for the two options. The total cost is similar for the two options. The capital cost is higher
for option 1, since it requires a centrifuge. However, the facility cost is higher for option 2, due to higher usage of purified
water during microfiltration. Raw material costs for both options are relatively minimal.
Figure 2. Cost comparison of options 1 and 2 under scenario 1