The present invention relates to a method in a continuous chromatography system configured to operate with at least three columns adapted for cyclic use for continuous purification of a sample comprising a target product when feeding the continuous chromatography system with the sample.
An important factor in process chromatography is binding capacity of a chromatography column for the solute. The binding capacity directly influences the productivity and cost of the chromatography step. The binding capacity is defined either in terms of dynamic/breakthrough capacity or as the maximum binding capacity. The dynamic capacity depends on the conditions at which the solution flows through a column packed with chromatography medium, and may be represented as a ratio between column volume and feed flow rate, a so called residence time. The maximum binding capacity represents a breakthrough capacity of the column if the residence time was infinitely long.
An initial breakthrough capacity is defined as the amount of binding solutes taken up by a column at the point when the solutes are first detected in the effluent. The breakthrough capacity can also be defined as a capacity at a given percentage of breakthrough, where the percentage represents the amount of binding solute present in the effluent from the column, expressed in percent of the solute present in the feed. According to this definition the maximum binding capacity will be equal to breakthrough capacity at 100% of breakthrough, i.e., at the point where no more solute can bind to the column. Therefore, in order to determine maximum capacity, the breakthrough capacities are measured at different levels of breakthrough, where the levels are defined by levels of concentration of solutes measured in the effluent from the column during sample loading.
Often these concentrations are determined by continuously monitoring a signal in a flow through a detector placed in the effluent line. The plot of these concentrations (signal) against time (or volume or mass loaded) is called a breakthrough curve. Location of the breakthrough on a chromatogram and its shape is related to how much solute the column is capable of binding and how quickly all adsorption sites are saturated with the solute. It also shows how much more solute can be bound to the column at any given time.
Breakthrough binding capacity for the solute is, in the presence of the impurities, one of the most critical parameters to optimize when developing a purification protocol. Because impurities often have similar light adsorbing properties as the solute determination of binding breakthrough capacities is a tedious and laborious work. In a typical experiment effluent from the column is collected in series of fraction, which are subsequently analysed using high resolution analysis techniques for the product in question, such HPLC, biological assays, ELISA, mass spectrometry, etc. Thus the determination of binding capacities for a chromatography column is rather complicated and in cases where the feed solution concentration is randomly varying during the feed application onto a chromatography column the true breakthrough capacities are close to impossible to measure accurately.
Accurate measuring is important if one wants to operate a column at the optimum process conditions. For instance, it can be shown that under certain conditions a maximum productivity of a capture chromatography step is obtained when the solute of interest reaches a certain value of its concentration in the column effluent, for instance a 10% of its initial concentration. If the breakthrough capacity is determined according to the method described above, it is impossible to terminate loading of the column at exact 10% breakthrough if either feed concentration or process conditions, including flow rate and/or chromatography media properties, vary with time in unpredictable manner.
Furthermore, accurate determination of breakthrough capacities at different levels of breakthrough under varying process conditions is also important in the case of continuous chromatography. Continuous chromatography can be realised by a system operating using simulated moving bed technology, wherein the connections between the columns is changed to facilitate a continuous feed of sample into the system. However, continuous chromatography may also be realised using moving bed technologies, wherein the columns are moved to facilitate continuous feed of sample.
In continuous chromatography, several identical, or almost identical, columns are connected in an arrangement that allows columns to be operated in series and/or in parallel, depending on the method requirements. Thus, all columns can be run in principle simultaneously, but with slightly shifted method steps. The procedure can be repeated, so that each column is loaded, eluted, and regenerated several times in the process. Compared to ‘conventional’ chromatography, wherein a single chromatography cycle is based on several consecutive steps, such as: load the sample, wash, elution, strip, Clean-In-Place (CIP) and re-equilibration, before the column may be used for another batch, in continuous chromatography based on multiple identical columns all these steps occur simultaneously but on different columns each.
Continuous chromatography operation results in better utilization of chromatography resin, reduced processing time and reduced buffer requirements, all of which benefits process economy.
Continuous chromatography is an example of periodic counter current process, because periodically all the chromatography columns comprising the system are simultaneously moved in the direction opposite to the sample flow. The apparent movement of the columns is realized by appropriate redirections of inlet and outlet stream to/from the columns.
Historically, essential factors for a reliable continuous process are:
1) the quality of the columns used, and more specifically the similarity or even identity between columns,
2) constant feed composition, and
3) hardware reliance, for instance constant flow rate delivered by pumps, valve functionality, etc.
If the columns are not identical, the theoretical calculations typically used to design continuous chromatography process will not be correct, and it will become difficult to design an efficient and robust continuous chromatography process. The same argument applies if feed concentration and flow rates vary with time in an unexpected manner.
Therefore, for scale-up considerations, having identical columns, reliable pumps in the system is essential. However, the packing of a column with a chromatography media is very complex in order to obtain repeatable results. Even small differences in the number of plates or other packing properties can have a huge effect on the end result. Furthermore, since capacities of chromatography resins typically change during resins lifetime/usage the process conditions chosen for a fresh resin may not be applicable for a resin that has been used for several times. If also the feed solution concentration will vary it will be even more complicated to design an efficient continuous chromatography process that would operate at its optimum all the time.
An example of continuous chromatography, configured to operate with three or four columns, is ÄKTA™ pcc 75 produced by GE Health Care (description available from www.gelifesciences.com/AKTA).
The process performance of the ÄKTA™ pcc 75 is monitored through trend curves for UV, amount of target molecules in elution peaks, and sample volume loaded on each column per cycle.
However, the large amount of data generated by the continuous chromatography system makes it difficult to detect deviating behaviour of the system performance in real time.
Thus, there is a need to introduce a process for handling large amount of data to identify deviating behaviour in the overall system performance in real time.
An object of the present disclosure is to provide methods and devices configured to execute methods and computer programs which seek to mitigate, alleviate, or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination.
The object is achieved by 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. The method comprises: 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.
An advantage is that the efficiency of the purification process in an continuous chromatography is increased.
Another advantage is that it is possible to plan and perform maintenance of the continuous chromatography in advance, and thereby minimizing the down-time of the system.
Further objects and advantages may be obtained from the detailed description by a skilled person in the art.
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.
In
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.
The sample containing the target product is exploited in a cell free extraction process, e.g. by filtration, centrifugation or another technique.
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.
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.
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.
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.
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.
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.
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.
The capture step 13 may comprise a continuous chromatography 20, as illustrated in
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
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.
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
The continuous chromatography comprises at least three columns and the principle of operations in a three columns (3C) setup is described in connection with
In
In
In
The continuous chromatography illustrated in
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 ΔUVmax, wherein ΔUV is calculated using equation (1)
The difference between the baseline UV 55 and the UV signal at 100% breakthrough for a fully loaded column is defined as ΔUVmax, 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
The breakthrough curve (dashed curve 50) and the baseline 55 are the same as shown in
The solid line 70A 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 70B), column C (wide dashed line 70C) and column D (dot-dashed line 70D).
The real time trend analysis may be based on a relative comparison between columns and/or an absolute comparison between cycles for each column.
In
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.
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.
Apart from the first cycle for column A, all curves 74A-74D 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.
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.
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.
According to another aspect, the detected parameter in step 81 is target product concentration in sample introduced in each column of the continuous chromatography.
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.
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.
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.
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.
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.
The method described in connection with
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.
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
According to another aspect, at least part of the processing circuitry and/or historic data is realised in a cloud implementation.
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
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 1st) is fed with sample from the cell culture process and the outlet of column D is connected with the inlet of column A (denoted 2nd). 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.
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
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
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.
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 1st) is fed with sample from the cell culture process and the outlet of column A is connected with the inlet of column B (denoted 2nd). 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.
To return to the main screen a button 104 is provided for the user.
Number | Date | Country | Kind |
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1622342.2 | Dec 2016 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/084478 | 12/22/2017 | WO | 00 |