TECHNICAL FIELD

The field of this invention is related to adsorptive devices and processes, of which chromatography is an example. More specifically, this invention relates to hyper-productive chromatography systems, chromatographic devices and chromatography processes. This invention also relates to chromatographic devices incorporating different media, having different distribution networks, configurations and stacking features.

BACKGROUND OF THE INVENTION

Adsorptive processes and devices are widely used in the analysis and purification of chemicals, including synthetic and naturally-derived pharmaceuticals, blood products and recombinant proteins.

Chromatography is a general separation technique that relies on the relative affinity or distribution of the molecules of interest between a stationary phase and a mobile phase for molecular separation. The stationary phase typically comprises a porous media imbibed with solvent. The mobile phase comprises a solvent, which can be aqueous or organic, that flows through the interstitial space that exists between the spaces occupied by the stationary phase.

Columns with associated end caps, fittings and tubing are the most common configuration, with the media packed into the tube or column. The mobile phase is pumped through the column. The sample is introduced at one end of the column, the feed end, and the various components interact with the stationary phase by any one of a multitude of adsorptive phenomena. The differential adsorptive interaction between the components and media leads them to traverse the column at different velocities, which results in a physical separation of the components in the mobile phase. The separated components are collected or detected at the other end of the column, the eluent end, in the order in which they travel in the mobile phase. In one type of adsorptive process, referred to as capture and release process, the process involves multiple steps, first to load the media, then to wash it, and then to elute it.

Chromatographic methods include among other methods, gel chromatography, ion exchange chromatography, hydrophobic interaction chromatography, reverse phase chromatography, affinity chromatography, immuno-adsorption chromatography, lectin affinity chromatography, ion affinity chromatography and other such well-known chromatographic methods.

Adsorptive media comes in many forms, most typically in the form of beads. The beads are conventionally packed into columns, with the column walls and ends immobilizing the beads into a fixed adsorptive bed, a bed being a porous three dimensional structure containing the stationary phase (in this case the beads) and the pore space through which the mobile phase flows/permeates (the space between the beads). Adsorptive media may also be formed into cohesive beds that retain their shape by virtue of the cohesion in the media; just like beds made with beads, these beds have two distinct regions, one occupied by the stationary phase and another occupied by the mobile phase; this type of media are referred to as monolithic media, or simply as monoliths. Media may also be formed in the shape of fabrics or webs, which can be stacked to form an adsorptive bed. Beds made of monoliths are cohesive in 3 dimensions, whereas beds made of webs are cohesive only in 2 dimensions; beds made of beads alone have no cohesion, requiring the column to maintain its shape.

Planar adsorptive processes and devices have been in use. Examples of planar adsorptive processes are paper chromatography and thin layer chromatography. In these processes, the adsorptive bed has a planar geometry in contrast to the cylindrical geometry of conventional chromatography beds. The mobile phase typically flows through the stationary phase by virtue of the capillarity of the porous medium, which draws the solvent into the porous space of the media. These processes do not require that the fluid pressure be contained since the fluid is not being pumped. More recently, a form of planar chromatography has been developed in which the fluid is pumped; this process is referred to as over-pressure planar chromatography (OPPC). OPPC requires that the media be contained in apparatus that maintains the shape of the bed in spite of the pressures used. In all cases, the planar adsorptive beds used in these processes are very thin, usually no thicker than a millimeter, making them suitable for analytical applications.

Membrane-based adsorptive devices have been developed. In these devices the adsorptive media is either supported by or embedded into a flat micro-porous membrane, which is then fabricated into filtration devices. Two or more of these membranes may be stacked to form an adsorptive bed with a longer flow path; however, the number of layers that can be stacked is limited by the low hydraulic permeability of microfiltration membranes. Such filtration devices are characterized by the fact that the fluid being treated flows through the adsorptive media in a direction substantially perpendicular to the planar dimension of the media. The virtue of membrane adsorbers is their fast kinetics, enabling them to have short bed depths and high feed rates. However, the same attributes that confer them with fast kinetics severely and limit their capacity. Additionally, the intrinsic geometry of existing membrane adsorbers limit their scalability, the largest ones typically being no larger than 5 liters.

Furthermore, the bed depth, or absorptive path length, important in purification steps requiring resolution, is limited in membrane-based devices due to the low hydraulic permeability of microporous membranes. Membrane absorptive media is expensive, because the high cost of the membrane substrate and the challenges of functionalizing the membrane surface with absorptive chemistry. Finally, membrane-based adsorptive devices inherently have low capacity, and as a result membrane adsorption devices have found applicability primarily in “polishing” steps (e.g., virus and DNA removal) where the adsorptive load is negligible, rather than in the core capture/purification steps.

Conventional chromatographic devices require that beads must be packed into a column. The quality of this packing determines the performance of the adsorbing bed. This adds another source of variability to the chromatographic process and must be validated before use. Furthermore, beds packed with beads are prone to voiding, a phenomenon whereby the beads settle into a denser structure resulting in the creation of voids and in non-homogeneities in the packing density of the bed, all of which results in a deterioration of performance. This is especially true in columns packed with soft beads.

BACKGROUND OF THE INVENTION

Adsorptive processes and devices are widely used in the analysis and purification of chemicals, including synthetic and naturally-derived pharmaceuticals, blood products and recombinant proteins. Chromatography is a general separation technique that relies on the relative affinity or distribution of the molecules of interest between a stationary phase and a mobile phase for molecular separation. The stationary phase typically comprises a porous media imbibed with solvent. The mobile phase comprises a solvent, which can be aqueous or organic, that flows through the interstitial space that exists between the spaces occupied by the stationary phase.

Columns with associated end caps, fittings and tubing are the most common configuration, with the media packed into the tube or column. The mobile phase is pumped through the column. The sample is introduced at one end of the column, the feed end, and the various components interact with the stationary phase by any one of a multitude of adsorptive phenomena. The differential adsorptive interaction between the components and media leads them to traverse the column at different velocities, which results in a physical separation of the components in the mobile phase. The separated components are collected or detected at the other end of the column, the eluent end, in the order in which they travel in the mobile phase. In one type of adsorptive process, referred to as capture and release process, the process involves multiple steps, first to load the media, then to wash it, and then to elute it.

Chromatographic methods include among other methods, gel chromatography, ion exchange chromatography, hydrophobic interaction chromatography, reverse phase chromatography, affinity chromatography, immuno-adsorption chromatography, lectin affinity chromatography, ion affinity chromatography and other such well-known chromatographic methods.

Adsorptive media comes in many forms, most typically in the form of chromatographic beads. The beads are conventionally packed into columns, with the column walls and ends immobilizing the beads into a fixed adsorptive bed, a bed being a porous three dimensional structure containing the stationary phase (in this case the beads) and the pore space through which the mobile phase flows/permeates (the space between the beads).

Conventional chromatographic devices require that beads must be packed into a column. The quality of this packing determines the performance of the adsorbing bed. This adds another source of variability to the chromatographic process and must be validated before use. Furthermore, beds packed with beads are prone to voiding, a phenomenon whereby the beads settle into a denser structure resulting in the creation of voids and in non-homogeneities in the packing density of the bed, all of which results in a deterioration of performance. This is especially true in columns packed with soft beads.

While it is theoretically possible to achieve high operational velocities exceeding 2000 cm/hr with rigid particles, beads such as AbSolute (Novasep Process Pompey, France) or silica beads packed in columns, it is generally not possible to use softer beads such as agarose and polymethylmethacrylate microspheres (PMMA) at high velocities exceeding 400 cm/hr.

Furthermore silica particles are not generally used to purify monoclonal antibodies. Velocities higher than 400 cm/hr are even less possible with production-scale columns having diameters of 20-200 cm (Sigma=0.02-0.2/cm). Where Sigma is a specific surface area of the adsorptive bed, defined as the surface area of solid support divided by the volume of the bed, a measure of the level of support imparted to the packed bed by the walls of the adsorptive device. In the case of a conventional column sigma equals four divided by d (where d equals the diameter of the column).

Some silica bead based processes can theoretically be run at a velocity of 2000 cm/hr, however this is not possible with agarose or PMMA beads. It is also difficult to scale up lab processes to manufacturing volumes (e.g., exceeding one liter). However, even beds packed with rigid beads may be compressible, leading to undesirable increases in pressure drop and possibly voiding if run at very high velocities.

SUMMARY

The special demands imposed on pharmaceutical manufacturing processes make it highly desirable that such processes be easily scaled-up. In particular, there are many advantages to processes that can be scaled-up without having to reset or redevelop the processing conditions. Such processes are referred to in the industry as linearly-scalable processes; in essence, the parameters that define the separation process and operating conditions remain unchanged as the process moves from the laboratory bench (i.e., discovery), where the column can be as small as several milliliters, to the process development laboratory (e.g., columns of several liters), to clinical manufacturing, to large-scale manufacturing, where the chromatography column can be as large as several hundred liters. Existing chromatographic devices are not linearly scalable, their design and geometry requiring significant alterations as the device size increases, thereby introducing uncertainties and unwanted risks as processes evolve from drug discovery, to clinical trials, to small-scale and then to large-scale manufacturing.

An adsorptive bed to receive a liquid flow, according to one embodiment, includes a housing having a first surface, a scaffold disposed within the housing in contact with the first surface. The scaffold includes a stress absorbing substantially rigid structure and a plurality of open cells disposed within the rigid structure. The adsorptive bed further includes a plurality of adsorptive beads filling the plurality of open cells forming a packed bed of the plurality of adsorptive beads and the scaffold restricts movement of the plurality of adsorptive beads, absorbs compressive stress induced by a hydraulic pressure gradient along a direction of the liquid flow and transfers a portion of the induced compressive stress to the first surface of the housing. Such a device enables the use of adsorptive bead-based media in planarly cohesive adsorptive beds. Such a device can be linearly scaled to operate from the process development laboratory scale, to clinical manufacturing, to large-scale manufacturing.

Aspects of the present invention relate to absorptive devices that have the high capacity of beads but the operational advantages of webs, and in particular webs that have the properties of native agarose in rigid form. Other aspects of the present invention relate to linearly scalable devices and absorptive devices that provide the flexibility to develop new purification processes beyond the conventional batch chromatography processes.

A chromatographic method to process a liquid includes providing an adsorptive bed comprising as described above, processing the liquid using a rapid cycling controller and operating at a pressure of greater than 100 psi. A chromatography system includes devices using the adsorptive bed described above and additionally include at least one pump and at least one valve controlling a liquid feed stream and a rapid cycling controller coupled to the at least one pump and at least one valve. Such a technique and corresponding system allows operation of adsorptive bed packed in a chromatography column or an adsorptive bed is sealed in a monolithic block to operate at higher flow rates and pressures than can be achieved with conventional devices.

Another general aspect includes an adsorptive device including a shell including a chamber, chromatographic media disposed within the shell chamber, a distribution network fluidly coupled to the chromatographic media and an inlet port and an outlet port coupled to the distribution network.

One general aspect includes a method of performing a hyper-productive chromatography process including: providing a stackable chromatographic cassette, loading a sample to be processed, operating the stackable chromatographic cassette having an adsorptive chromatographic bed having a volume greater than 0.5 liter by establishing a flow at a linear velocity greater than 500 cm/hr and having a residence time of the loading step of less than one minute.

Such a technique and corresponding system allows operation of adsorptive bed to operate at higher flow rates and/or pressures than can be achieved with conventional devices. Such technique also enables higher productivity with lower residence times and/or the use of smaller beads and/or softer beads and/or beads with larger pores than are used in conventional columns.

In other embodiments the linear velocity is greater than 1000 cm/hr; the residence time in a load step is less than 0.5 minute. In another embodiment the residence time in a load step is less than 0.25 minute. In another embodiment, the chromatographic cassette is characterized by a linear pressure drop vs. velocity curve over a velocity range of zero to about 1200 cm/hr.

Other techniques include operating at a total cycle productivity of greater than about 60 gram per liter per hour (g/l/hr) (glh), with media having an average bead size less than about 50 micron at velocities greater than about 500 cm/hr. Still other techniques include operating at a total cycle productivity of greater than 100 glh with media having an average bead size less than about 40 micron at velocities greater than about 800 cm/hr. Another technique includes operating at a total cycle productivity of greater than 150 glh with media having an average bead size less than about 30 micron at velocities greater than about 1000 cm/hr. Another technique includes operating at a total cycle productivity of greater than 200 glh with media having an average bead size less than about 30 micron at velocities greater than about 1000 cm/hr.

The system may also include hyper-productive chromatography system and process, a method of performing a hyper-productive chromatography process including: providing at least one chromatographic cassette having an adsorptive chromatographic bed having a bed volume greater than one liter and including one of: compressible chromatographic adsorptive media, semi-compressible chromatographic adsorptive media, soft chromatographic adsorptive media. The method also includes placing the at least one chromatographic cassette in a cassette holder. The method also includes loading a sample to be processed. The method also includes operating the chromatographic adsorptive bed by establishing a flow at a velocity greater than 1000 cm/hr and having a residence time in a loading step is less than one minute. In other embodiments the bed volume is greater than ¼ liter and the flow velocity is greater than 500 cm/hr.

Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium. Chromatography cassettes described herein include Chromassettes® manufactured by SPF Technologies, LLC of Somerville, Mass.

