Monitoring Performance in Continuous Chromatography

Abstract

The present invention relates to a method for monitoring operational status in continuous chromatography configured to operate with at least three columns adapted for cyclic use for continuous purification of a target product when feeding the continuous chromatography with a sample containing the target product. The method comprises detecting (81) at least one parameter indicative of a selected function in the continuous chromatography, performing (82) real time trend analysis of the detected parameter to identify a deviating behaviour of the selected function, and initiate (83) actions to eliminate or reduce the effect of the identified deviating behaviour where by the performance of the continuous chromatography is maintained.

Claims

1. A method for monitoring operational status in a continuous chromatography configured to operate with at least three columns and configured for continuous purification in a cyclic operation, wherein the continuous purification is performed on a sample comprising a target product, wherein the method comprising: a) detecting at least one parameter indicative of a selected function in the continuous chromatography; b) performing real time trend analysis of each of the at least one detected parameter to identify a deviating behaviour of the selected function; and c) initiating actions to eliminate or reduce the effect of the identified deviating behaviour, whereby the performance of the continuous chromatography is maintained.

2. The method according to claim 1, wherein the selected function in the continuous chromatography is indicative of operational status of at least one column.

3. The method according to claim 2, wherein the selected function in the continuous chromatography is column capacity, and step a) is performed for each column in the continuous chromatography.

4. The method according to claim 3, wherein the detected parameter in step a) is load volume and/or time of sample for each column to a predetermined capacity, and the trend analysis in step b) is performed over time.

5. The method according to claim 3, wherein multiple cycles for each of the at least three columns are performed and the detected parameter in step a) is related to cyclic performance, and the trend analysis in step b) is performed based on cycle number.

6. The method according to claim 3, wherein the detected parameter in step a) is load volume and/or time of sample for each column to a predetermined capacity, and the trend analysis in step b) is performed by comparing load time between columns present in the continuous chromatography.

7. The method according to claim 2, wherein the continuous chromatography comprises at least four columns and when the operational status of a particular column indicates that action is needed to maintain performance of the continuous chromatography, wherein step c) further comprises: c1) removing the particular column from the columns used by the continuous chromatography for continuous purification; and c2) performing actions to reinstate the operating status of the particular column.

8. The method according to claim 7, wherein the operational status indicates that the operational status of the particular column can be reinstated in-place, and the action performed in step c2) comprises running a conditioning process of the particular column.

9. The method according to claim 7, wherein the operational status indicates that the particular column has to be replaced, and the action performed in step c2) comprises removing the particular column from the continuous chromatography and replacing it with a new column.

10. The method according to claim 1, wherein the detected parameter in step a) is target product concentration in sample introduced in each column of the continuous chromatography.

11. A continuous chromatography configured to operate with at least three columns and configured for continuous purification in a cyclic operation, wherein the continuous purification is performed on a sample comprising a target product, wherein the continuous chromatography comprises: sensors configured to detect at least one parameter indicative of a selected function in the continuous chromatography; and processing circuitry configured to perform real time trend analysis of each of the at least one detected parameter to identify a deviating behaviour of the selected function, and to initiate actions to eliminate or reduce the effect of the identified deviating behavior; whereby operational status is monitored and the performance of the continuous chromatography is maintained.

12. The continuous chromatography according to claim 11, wherein the processing circuitry has access to historic data of the at least one detected parameter stored in a database, and the trend analysis is further based on the historic data.

13. The continuous chromatography according to claim 12, wherein at least part of the processing circuitry and/or historic data is realized in a cloud implementation.

14. A computer program for monitoring operational status in a continuous chromatography, comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to claim 1.

15. A computer-readable storage medium carrying a computer program for monitoring operational status in a continuous chromatography according to claim 14.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 illustrates an overview of a bioprocess purification system designed to purify a target product using continuous chromatography.

[0027] FIG. 2 illustrates a continuous chromatography with an arbitrary number of columns, based on a simulated moving bed technology.

[0028] FIGS. 3a-3c illustrate the principle of three column chromatography.

[0029] FIGS. 4a-4d illustrate capacity utilization for conventional batch chromatography operation compared to multi-column chromatography operation.

[0030] FIG. 5 illustrates an overview of two-step breakthrough in continuous chromatography.

[0031] FIG. 6 illustrates UV signal detectors used for dynamic control in continuous chromatography.

[0032] FIGS. 7a and 7b illustrate data used for trend analysis.

[0033] FIG. 8 illustrates a process for improving the efficiency in an continuous chromatography.

[0034] FIG. 9 illustrates a graphical interface for a continuous chromatography in a first occasion.

[0035] FIGS. 10a-10d illustrate graphs for monitoring operational status of columns in a continuous chromatography.

[0036] FIG. 11 illustrates a graphical interface for a continuous chromatography in a second occasion.

[0037] FIG. 12 illustrates a real time evaluation interface.

DETAILED DESCRIPTION

[0038] A continuous chromatography is designed for purification of target products (such as proteins, biomolecules from cell culture/fermentation, natural extracts) in continuous downstream processes using periodic counter current chromatography, as explained in background section. The technology employs three or four chromatography columns to create a continuous purification step. The columns are switched between loading and non-loading steps, such as wash and elution. Continuous chromatography supports process intensification by reducing footprint and improving productivity. In addition, continuous chromatography is especially suited for purification of unstable molecules, as the short process time helps to ensure stability of the target product.

[0039] In FIG. 1, an overview of a bioprocess purification system, configured to purify a target product using a separation process is shown. The bioprocess purification system comprises a number of steps related to Cell culture 11, Hold 12, Capture 13, Viral inactivation 14, Polish 15 and Delivery 16.

[0040] In a fully continuous process the cell culture step 11 may be a perfusion type culture which comprises continuous addition of nutrients for cell growth in perfusion culture and continuous removal of product and waste through drain and filtration. E.g. using an Alternate Tangential Filtration (ATF) filter. The step may comprise process control for viable cell density (VCD), and the next step in the process starts when VCD reaches a pre-determined value. The VDC may be controlled by adapting the components of the cell culture media fed to the culture or by addition of certain components directly to the culture. Alternatively, the cell culture is of batch type.

[0041] The sample containing the target product is exploited in a cell free extraction process, e.g. by filtration, centrifugation or another technique.

[0042] The hold step 12 is an optional step depending on process needs, e.g. if a filter is in-line before capture step 13. The step may comprise process control on weight, and the next step in the process starts when a pre-determined volume value is reached, or alternatively after a certain time period or when a pre-determined mass is reached. The hold step may be used both for collecting a volume of filtered feed from a perfusion cell culture or from a batch culture.

[0043] The capture step 13 comprises a continuous chromatography that may have a filter in-line before the capture step. The continuous chromatography may be run as periodic counter current chromatography with a continuous feed of sample from the cell culture step 11, directly or via the hold step 12, containing the target product. The capture step comprises multiple batch elutions, and process control using in-line UV-sensors handles variation in feed concentration and resin capacity. The next step starts when a pre-determined amount value (e.g. volume, mass or time) is reached.

[0044] In the viral inactivation step 14, different options for virus inactivation is available depending on process needs. One option is to use batch mode with low pH for 30-60 minutes in hold up tank. The step may comprise process control on volume, time, temperature and pH. The next step starts when a pre-determined time is reached.

[0045] The polish step 15 may be straight through processing (STP) with a connected batch step or continuous chromatography with a continuous load step, or a combination thereof. The flow rate is adjusted to perfusion rate required by producer cells, which means that the flow rate is determined by the preceding step. The step may comprise process control for UV, flow and volume, and the next step starts when a pre-determined volume and amount is reached, alternatively when a timeout is reached.

[0046] The delivery step 16 may comprise a virus removal step, e.g. a viral filter, before an ultra-filtration step. The delivery step may be used as concentration step for batch addition of sample from polish step. The delivery step may comprise continuous or batch delivery of product and may comprise continuous or batch removal of waste. The step may comprise process control for pH, conductivity, absorbance, volume and pressure, and delivery is achieved when a pre-determined product concentration in a pre-defined environment is reached.

[0047] An automation layer 17 is used for handling decision points for next step in the process. Different type of sensors (not shown), both in-line sensors and off-line sensors, are integrated into the process flow to monitor different parameters that may be used for providing the automation layer 17 with data that could be used to handle the decision points. Sensors include but are not limited to only measure flow, VCD, weight, pressure, UV, volume, pH, conductivity, absorbance, etc.

[0048] It should be noted that UV an example of a parameter that could be monitored to detect the composition of the sample being purified. However, other parameters may be used operating in other frequency ranges, such as IR, fluorescence, x-rays, etc.

[0049] The capture step 13 may comprise a continuous chromatography 20, as illustrated in FIG. 2. Sample containing the target product is fed into the continuous chromatography 20 via inlet 21 and the eluted target product is available at outlet 22. The continuous chromatography 20 comprises multiple columns A, B, . . . , N, and each column is provided with a column inlet 23 and column outlet 24. The column inlet 23 and column outlet 24 of each column is connected to a valve system 25 configured to connect the columns cyclically to the inlet 21 and the outlet 22 to achieve continuous purification of the target product. Example of a system configuration having three columns is described in connection with FIG. 3a-3c.

[0050] The continuous chromatography 20 is further provided with buffer inlet 26 and waste outlet 27 in order to be able to perform the required operations. An in-line sensor 28 may provide after the column outlet 24 of each column or be assigned to the process flow and integrated into the valve system 25. Important parameters, such as UV, is measured to control the process, as described below. Another in-line sensor 28 may be provided before the column inlet 23 of each column in order to be able to directly evaluate performance of each column. An in-line inlet sensor 26 may also be provided to monitor the composition of the sample fed into the continuous chromatography 20

[0051] The continuous chromatography may also comprise off-line sensors 29, which are designed to extract material from the process and thereafter evaluate selected parameters before the material is disposed of as waste.

[0052] The principle behind the continuous chromatography is to keep at least two columns in the loading zone which allows for overloading of the first column without risk of product loss, as the breakthrough will be caught by downstream columns, as described in connection with FIGS. 4a-4d.

[0053] The continuous chromatography comprises at least three columns and the principle of operations in a three columns (3C) setup is described in connection with FIGS. 3a-3c. The 3C setup features two parallel flows: one for loading of the two columns in the loading zone, and one for the non-loading steps, e.g. elution and regeneration of the third column.

[0054] In FIG. 3a, illustrating step 1, column A and B are in the loading zone. Column A can be overloaded without sample loss, as column B catches the breakthrough from column A. In this way, the utilization of the resin binding capacity is maximized.

[0055] In FIG. 3b, illustrating step 2, the overloaded column A is switched and column B becomes the first column and column C becomes the second column in the loading zone. The overloaded column A will now be subjected to the non-loading steps, such as elution and regeneration in a parallel workflow.

[0056] In FIG. 3c, illustrating step 3, the overloaded column B in the loading zone is switched. Now column C becomes the first column and column A the second column in the loading zone, while column B is subjected to elution and regeneration in the parallel workflow. These three steps are repeated in a cyclic manner until required target product volume, mass or amount is reached (or until resin lifetime is reached and columns needs to be repacked or exchanged).

[0057] The continuous chromatography illustrated in FIG. 2 may utilize more than three columns, and in a four column (4C) setup, the same principle applies. However, the non-loading steps can become limiting in a 3C setup, and the non-loading steps can be split on two columns and run in parallel utilizing a third flow path in the 4C setup. The 4C setup allows for balancing the loading and non-loading steps. More columns will lead to a more flexible system, while the complexity of the valve system 25 becomes increasingly complicated. However, some continuous chromatography have sixteen or more columns.

[0058] FIGS. 4a-4b illustrate capacity utilization for conventional batch chromatography operation compared to multi-column chromatography operation. FIG. 4a illustrates the total available capacity 40 of a chromatography resin and breakthrough curve is indicated by 30. As is apparent from the graph, when a small volume is loaded the product will be captured in the resin, but at large volumes a substantial part of the product will breakthrough and be wasted in a batch operation.

[0059] FIG. 4b illustrates the sample load 41 at 10% breakthrough. The product below the breakthrough curve 30 will be wasted if not reused in another column. The capacity 42 typically used in batch operations is illustrated in FIG. 4c, and capacity 43 used in continuous chromatography is illustrated in FIG. 4d. Note that the product breakthrough 44 is captured by the columns downstream in the loading zone.

[0060] Dynamic control functionality, which allows for some variations in feed composition, may be implemented in the continuous chromatography. The principle of dynamic control is based on the relative difference in UV signals before and after each column at breakthrough. The difference between the baseline UV and the UV signal at 100% breakthrough for a saturated column is defined as UV.sub.max, wherein UV is calculated using equation (1)

[00001]$\begin{array}{cc}.Math.\mathrm{UV}=100\frac{{\mathrm{UV}}_{\mathrm{BT}}-\mathrm{Baseline}}{{\mathrm{UV}}_{\mathrm{sample}}-\mathrm{Baseline}}& \left(1\right)\end{array}$

[0061] FIG. 5 illustrates the two-step breakthrough, displaying the central UV signals used for dynamic control. Curve 50 shows the UV.sub.BT (i.e. the post column breakthrough curve), curve 51 shows the UV.sub.sample (i.e. the pre column feed line), and reference numeral 55 indicates the baseline. Reference numeral 52 indicates total signal from target product and impurities in the sample being fed into the column, reference numeral 53 indicates signal from impurities (background), and reference numeral 54 indicates UV.sub.max (signal from target product).

[0062] The difference between the baseline UV 55 and the UV signal at 100% breakthrough for a fully loaded column is defined as UV.sub.max, where the desired level is process-dependent. A continuous chromatography may use UV detectors assigned to the process stream and not to the separate columns. Hence, each breakthrough curve may be generated based on signals from two UV detectors as illustrated in FIG. 6.

[0063] The breakthrough curve (dashed curve 50) and the baseline 55 are the same as shown in FIG. 5. Curve 60 is UV of the sample fed into the column, curve 61 is UV of the breakthrough after the column and curve 62 is UV of the flow through (waste).

[0064] FIG. 7a is a graph illustrating peak amount calculated after the elution step for each column. The calculation is an integration of the measured amount after elution and is measured in mg of the target product (y axis) and the x axis is run time.

[0065] The solid line 70.sub.A indicates the peak amount calculated for column A, and the curve is amount is adjusted in steps approximately every 175 minutes. The same applies for column B (dashed line 70.sub.B), column C (wide dashed line 70.sub.C) and column D (dot-dashed line 70.sub.D).

[0066] The real time trend analysis may be based on a relative comparison between columns and/or an absolute comparison between cycles for each column.

Example

[0067] In FIG. 7a, the peak amount for columns A, B and D indicate a similar performance regarding the expected yield from the columns (around 62 mg per cycle). However, the peak amount for column C starts at the expected level (as indicated by 71) but after eight cycles, the peak amount is only 90% of the expected level (as indicated by 72), and thus a warning is issued within the system indicating that action is required and maintenance is scheduled to eliminate (or reduce) the effect column C has to the overall efficiency of the continuous chromatography.

[0068] If the peak amount for column C goes below the 80% of the expected level (as indicated by 73), immediate action may be needed to ensure full functionality.

[0069] FIG. 7b is a graph illustrating loading volume of sample (y axis) into each column A-D over run time (x axis). The solid line 74.sub.A is the measured loading volume for column A, and the curve is amount is adjusted in steps approximately every 60 minutes. The same applies for column B (dashed line 74.sub.B), column C (double dot-dashed line 74.sub.C) and column D (dotted line 74.sub.D).

[0070] Different boundary conditions (lines 75-79) are indicated in the graph, which may be used to identify trends that indicate a deviating behaviour. If, for instance, the loading volume is more than 20% higher than the expected level (as indicated by 75) immediate action is required to maintain proper functionality in the system. This is illustrated for column A, which exceeds the +20% level (as indicated by 79) after the first cycle. This may be an indication that the concentration of target product in the sample fed into the column is too low. However, this is only shown for column A during the first cycle and may be a result of the start-up process.

[0071] Apart from the first cycle for column A, all curves 74.sub.A-74.sub.D show the same behaviour, which is a steady declining behaviour and after 7-8 cycles, the lower warning level (as indicated by 76) is passed and this indicate that the concentration of target product in the sample is increasing. Action may be needed to ensure proper functionality.

[0072] FIG. 8 illustrates a method for monitoring operational status in continuous chromatography. The continuous chromatography is configured to operate with at least three columns adapted for cyclic use for continuous purification of a target product when feeding the continuous chromatography with a sample containing the target product.

[0073] The flow starts in step 80 and proceeds to step 81, wherein at least one parameter indicative of a selected function in the continuous chromatography is detected. Examples of parameters that may be detected (either by themselves or in combination) are UV, flow, pressure, pH, etc. The purpose of detecting one or more parameters are because they are linked to different functions. In one embodiment, the selected function in the continuous chromatography is indicative of operational status of at least one column.

[0074] In another embodiment, the selected function in the continuous chromatography is column capacity, and parameter(s) is/are detected for each column in the continuous chromatography. According to one aspect, the detected parameter is load volume of sample for each column to a predetermined capacity.

[0075] According to another aspect, the detected parameter in step 81 is target product concentration in sample introduced in each column of the continuous chromatography.

[0076] The flow continues to step 82, wherein real time trend analysis of the detected parameter is performed to identify a deviating behaviour of the selected function. Real time trend analysis may be performed over time (for instance when load volume is detected), or based on cycle number when multiple cycles for each of the at least three columns are performed and the detected parameter in step is related to cyclic performance.

[0077] According to another aspect real time trend analysis may be performed by comparing load volume and/or time between columns present in the continuous chromatography, when the detected parameter is load volume and/or load time of sample for each column to a predetermined capacity.

[0078] In step 83, actions to eliminate or reduce the effect of the identified deviating behaviour are initiated whereby the performance of the continuous chromatography is maintained.

[0079] According to one aspect of the invention, the continuous chromatography comprises at least four columns and when the operational status of a particular column indicates that action is needed to maintain performance of the continuous chromatography, additional step 84 is performed in which the particular column is removed from the columns used by the continuous chromatography for continuous purification, and step 85 is performed in which actions to reinstate the operating status of the particular column is performed.

[0080] The action performed in step 85 may comprise running a conditioning process of the particular column, when the operational status indicates that the operational status of the particular column can be reinstated in-place as indicated by 86. Furthermore, the action performed in step 85 may alternatively comprise removing the particular column from the continuous chromatography and replacing it with a new column as indicated by 87 when the operational status indicates that the particular column has to be replaced.

[0081] The method described in connection with FIG. 8 may be implemented in a continuous chromatography configured to operate with at least three columns adapted for cyclic use for continuous purification of a target product when feeding the continuous chromatography with a sample containing the target product as disclosed in connection with FIG. 2.

[0082] The continuous chromatography comprises sensors configured to detect at least one parameter indicative of a selected function in the continuous chromatography, processing circuitry configured to perform real time trend analysis of the detected at least one parameter to identify a deviating behaviour of the selected function, and to initiate actions to eliminate or reduce the effect of the identified deviating behaviour, whereby operational status is monitored and the performance of the continuous chromatography is maintained.

[0083] According to one aspect, the processing circuitry has access to historic data of the at least one detected parameter stored in a database, and the trend analysis is then further based on the historic data, as described in connection with FIGS. 7a and 7b.

[0084] According to another aspect, at least part of the processing circuitry and/or historic data is realised in a cloud implementation.

[0085] The method described above may be implemented in a computer program for monitoring operational status in a continuous chromatography. The computer program comprises instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to the different variations described in connection with FIG. 8. The computer program for monitoring operational status in a continuous chromatography may be stored on and carried by a computer-readable storage medium.

[0086] FIG. 9 illustrates a graphical interface 90 for a continuous chromatography at a first occasion. The graphical interface is divided into several areas having different purposes. In the lower part of the graphical interface, a time line 91 is used to illustrate the projected run time, the executed run time 92a of the process, and the planned process 92b. Information pointers are illustrated to highlight certain events 93 that needs to be handled during the projected run time, such as scheduled maintenance, to prevent unscheduled downtime of the production.

[0087] The main area comprises an overview 94 of the chromatography process illustrating the process of each column A-D of the continuous chromatography. At the first occasion, column D (denoted 1.sup.st) is fed with sample from the cell culture process and the outlet of column D is connected with the inlet of column A (denoted 2.sup.nd). This means that column D and A are in the loading phase. The loaded column C (denoted Elution) is eluted and the outlet of column C is treated in subsequent steps in the bioprocess purification system. Column B (denoted CIP) was previously eluted and is cleaned to be able to be loaded with sample in a the future. The overview also include a possibility to adjust the purification method manually as indicated by 95. However, the planned process 92b is preferably not altered since this may influence the uptime of the system.

[0088] The main screen also comprises an area 96 illustrating operational status of the columns A-D, which are described in more detail in connection with FIGS. 10a-10d. Performance of each column A-D is shown in 97, indicating where in the process each column is and also a real time trend indication. in this case, the performance of column B is highlighted and action is needed to ensure proper functionality. This may be planned and is the reason for the maintenance scheduled in the near future, as indicated by the first information pointer 93.

[0089] Certain key data, which are important for the process are presented in a separate area 98. Examples of key data is Total yield, Baseline, AUV. In order to be able to monitor and evaluate in real time, a button 99 is provided to switch between trend curves and the main screen. An example of an evaluation interface is shown in connection with FIG. 12.

[0090] FIGS. 10a-10d illustrate graphs for monitoring operational status of columns A-D in a continuous chromatography. FIG. 10a illustrate the UV Flow through of column A, FIG. 10b illustrate the conductivity during regeneration for column B, FIG. 10c illustrate the UV Elution for column C and FIG. 10d illustrate the UV breakthroughbaseline for column D.

[0091] FIG. 11 illustrates a graphical interface 100 for a continuous chromatography at a second occasion. The graphical interface 100 is divided into the same areas as described in FIG. 9.

[0092] However, the time line 91 is adjusted to compensate for the time elapsed between the first occasion and the second occasion. The is used to illustrate the projected run time, the executed run time 101a has been adjusted as well as the planned process 101b.

[0093] The overview 94 of the chromatography process illustrating the process of each column A-D of the continuous chromatography is updated. At the second occasion, column A (denoted 1.sup.st) is fed with sample from the cell culture process and the outlet of column A is connected with the inlet of column B (denoted 2.sup.nd). This means that column A and B are in the loading phase. The loaded column D (denoted Elution) is eluted and the outlet of column D is treated in subsequent steps in the bioprocess purification system. Column C (denoted CIP) was previously eluted and is cleaned to be able to be loaded with sample in a the future.

[0094] FIG. 12 illustrates a real time evaluation interface, which is activated when an operator press the evaluation button 99, as described in connection with FIG. 9. The most important areas are still available in the evaluation interface, i.e. time line 91, performance 97 and key data 98. The major area of the evaluation interface shows a chromatogram 102 illustrating comparisons between selected parameters detected by sensors in the continuous chromatography. Different columns may be selected, as indicated by 103.

[0095] To return to the main screen a button 104 is provided for the user.