Tangential Flow Virus Filtration

Abstract

The virus filter includes a filter member characterized by a first surface and a second surface, and having a thickness extending in a first direction between the first and second surfaces, and a plurality of channels formed in the filter member, each channel having a channel axis, wherein, during use, a solution carrying a viral load flows in a direction parallel to the first surface, and at least a portion of the viral load is removed from the first surface. membrane and propagates in a first direction, and for at least 50% of the channels in the filter element, the channel axis is oriented at an angle between 5 and 85 degrees relative to the first direction.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 816,786, filed Mar. 11, 2019, the entire content of which is incorporated herein by reference.

[0002] This disclosure relates to biotechnology and biomanufacturing.

Background Art

[0003] Mammalian cells containing nucleic acids encoding recombinant proteins are often used to produce therapeutically or commercially important proteins. In the current environment where the product pipeline is diverse, biotechnology companies are increasingly pressured to develop innovative solutions for manufacturing therapeutic protein drug substances with high adaptability and cost - effectiveness.

Summary of the Invention

Problems to be Solved by the Invention

[0004] To perform biomanufacturing on a production scale, several unit operations are implemented as continuous processes. Among these processes, virus removal from the production stream is still a difficult task to perform. This disclosure features systems and methods for performing tangential flow virus filtration (TFVF). TFVF can be implemented on a continuous or semi - continuous basis in order to enable online purification of a wide variety of therapeutic protein drug substances, including recombinant therapeutic proteins, in some embodiments. In a TFVF system, fluid (e.g., process fluid containing one or more products to be purified) can be circulated through a fluid circuit containing a filter element that captures or retains virus particles. A portion of the fluid and its contents do not pass through the filter and are recirculated through another path through the system.

Means for Solving the Problems

[0005] In one aspect, the present disclosure features a filter member having a first surface and a second surface, and having a thickness extending in a first direction between the first and second surfaces, and a plurality of channels formed in the filter member, each of the channels having a channel axis, and a virus filter including the plurality of channels, wherein, in use, a solution holding a virus load flows in a direction parallel to the first surface, at least a portion of the virus load enters the membrane from the first surface, propagates in the first direction, and for at least 50% of the channels in the filter member, the channel axis is oriented at an angle between 5 degrees and 85 degrees with respect to the first direction.

[0006] Embodiments of this filter may include one or more of the following features.

[0007] The channel axis is oriented at an angle between 5 degrees and 75 degrees (e.g., between 10 degrees and 60 degrees) with respect to the first direction. For at least 70% of the channels in the filter member (e.g., for at least 90% of the channels), the channel axis is oriented at an angle between 5 degrees and 85 degrees with respect to the first direction.

[0008] The thickness of the filter member can be 150 micrometers or more (e.g., 300 micrometers or more, 500 micrometers or more). Each member of the plurality of channels can include an opening in the first surface, and the ratio of the total area of the openings to the total area of the first surface can be 0.10 or more (e.g., 0.20 or more, 0.30 or more). Each member of the plurality of channels can have a certain volume, and the ratio of the total volume of the channels to the total volume of the member can be 0.05 or more (e.g., 0.10 or more, 0.20 or more).

[0009] For each of at least some of the members of the plurality of channels, the member channel includes an opening having a first cross-sectional area on a first surface, and this first cross-sectional area can be made smaller than a second cross-sectional area at one position between the first and second surfaces of the member channel. The ratio of the first cross-sectional area to the second cross-sectional area can be 0.95 or less (for example, 0.85 or less, 0.75 or less). At least some of the members can include at least 40% (for example, at least 60%, all) of the members of the plurality of channels.

[0010] The channel axes of the plurality of channels can have a distribution of orientations with respect to a first direction. The distribution of the average orientation can be between 10 degrees and 30 degrees with respect to the first direction (for example, between 30 degrees and 50 degrees, between 50 degrees and 80 degrees). The full width at half maximum (FWHM) value of the distribution of the orientation can be 60 degrees or less (for example, 40 degrees or less, 15 degrees or less).

[0011] For each of at least some of the members of the plurality of channels, the member channel can include one or more secondary channels extending from the channel axis. One or more secondary channels can extend along a secondary axis from the channel axis at an angle between 10 degrees and 80 degrees with respect to the channel axis. One or more secondary channels can extend along a secondary axis from the channel axis at an angle between 50 degrees and 90 degrees with respect to the channel axis.

[0012] One or more of the member channels can include three or more (for example, five or more) secondary channels. The member channel can include an average of five or more (for example, seven or more) secondary channels.

[0013] For each of at least some of the members of the plurality of channels, the member channel can include an opening on the first surface having a first cross-sectional area and a maximum cross-sectional area different from the first cross-sectional area at a position between the first and second surfaces on the first surface. The ratio of the first cross-sectional area to the maximum cross-sectional area can be 0.50 or less (for example, 0.30 or less, 0.10 or less).

[0014] At least some members of the plurality of channels may include more than 50% (e.g., more than 80%) of the plurality of channels. For each of at least some members of the plurality of channels, the member channel can include a maximum cross-sectional area and a minimum cross-sectional area at different positions along the channel axis, and the ratio of the minimum cross-sectional area to the maximum cross-sectional area can be 0.75 or less (e.g., 0.50 or less, 0.30 or less).

[0015] The first surface can be a plane, have a maximum dimension measured in this plane, and the ratio of the maximum dimension to the thickness can be 10 or more (e.g., 20 or more). The porosity of the member can be between 0.3 and 0.9.

[0016] The member is formed from a first material, and each of at least some members of the plurality of channels can include a second material located on the inner surface of the member channel. The first material is selected from the group consisting of polyvinylidene fluoride (PVDF), hydrophilic PVDF, and regenerated cellulose. The second material is selected from the group consisting of cellulose, polyethersulfone, and polyethylene glycol.

[0017] The ratio of the average thickness of the second material on the inner surface of the member channel to the maximum cross-sectional dimension of the member channel can be 0.2 or less (e.g., 0.1 or less, 0.05 or less, 0.02 or less).

[0018] The plurality of channels can be a first plurality of channels, and the filter member can include a first layer characterized by the first plurality of channels and a second layer characterized by a second plurality of channels. The second layer can be in contact with the first layer. At least some members of the first plurality of channels can be in fluid communication with at least some members of the second plurality of channels at the interface between the first and second layers.

[0019] Each of the channels of the second plurality of channels can include a channel axis, and for at least 50% of the second plurality of channels of the second layer, the channel axis is oriented at an angle between 5 degrees and 90 degrees with respect to the first direction. The average orientation of the first plurality of channels with respect to the first direction can be different from the average orientation of the second plurality of channels with respect to the first direction.

[0020] The average angle between the channel axis and the first direction can be greater than the average angle between the channel axis of the first plurality of channels and the first direction. For the second plurality of channels, the average angle between the channel axis and the first direction can be less than the average angle between the channel axis of the first plurality of channels and the first direction.

[0021] The first layer is formed from a first material selected from the group consisting of polyvinylidene fluoride (PVDF), hydrophilic PVDF, and regenerated cellulose, and the second layer is formed from a second material selected from the group consisting of cellulose and regenerated cellulose, polyethersulfone, polyethylene glycol, polyethylene, polypropylene, polyvinylbenzene, polypropylene glycol, polyurethane, polymethylmethacrylate, and polyacrylic acid. The first material and the second material can be different.

[0022] At least some of the first plurality of channels may include a coating material on the inner surface of at least some of the channels. The coating material is selected from the group consisting of cellulose, polyethersulfone, and polyethylene glycol. At least some of the second plurality of channels may include a coating material on the inner surface of at least some of the channels. The coating material is selected from the group consisting of cellulose, polyethersulfone, and polyethylene glycol. At least some of the first plurality of channels may include a first coating material on the inner surface of at least some of the first plurality of channels, and at least some of the second plurality of channels may include a second coating material on the inner surface of at least some of the second plurality of channels.

[0023] Each member of the first plurality of channels can include an opening in the first surface, each member of the second plurality of channels can include an opening in the interface surface between the first and second layers, and the average cross-sectional area of the openings of the first plurality of channels is different from the average cross-sectional area of the openings of the second plurality of channels. The average cross-sectional area of the openings of the first plurality of channels can be larger than the average cross-sectional area of the openings of the second plurality of channels. The ratio of the total area of the openings of the first plurality of channels on the first surface to the area of the first surface can be larger than the ratio of the total area of the openings of the second plurality of channels on the interface surface to the area of the interface surface.

[0024] Each member of the first plurality of channels can have a certain volume in the first layer, each member of the second plurality of channels can have a certain volume in the second layer, and the ratio of the total volume of the first plurality of channels in the first layer to the volume of the first layer can be larger than the ratio of the total volume of the second plurality of channels in the second layer to the volume of the second layer.

[0025] For each of at least some members of the second plurality of channels, the member channels can have an opening having a first cross-sectional area at the interface between the first and second layers and a second cross-sectional area at a position displaced from the interface along the member channel axis, and the first cross-sectional area can be smaller than the second cross-sectional area. The ratio of the first cross-sectional area to the second cross-sectional area can be 0.85 or less (e.g., 0.50 or less). Each member of the second plurality of channels can be oriented with respect to a first direction defined by the channel axis of that member, and the full width at half maximum (FWHM) of the distribution of the orientations of the second plurality of channels can be 20 degrees or less (e.g., 10 degrees or less).

[0026] The embodiments of the filter can also include any combination of features described separately in connection with separate embodiments, and can also include any of the other features described herein, unless otherwise specified.

[0027] As used herein, the term "about" means "approximately" (e.g., plus or minus 10% of the indicated value).

[0028] References herein to "one embodiment," "an embodiment," etc., indicate that the embodiment described may include a particular aspect, function, structure, or characteristic, but not that all embodiments necessarily include that aspect, function, structure, or characteristic. Further, such phrases may, but do not necessarily, refer to the same embodiment referred to in other parts of this specification. Further, when a particular aspect, feature, structure, or characteristic is described in connection with an embodiment, whether explicitly described or not, it is within the knowledge of one of ordinary skill in the art to affect or combine such aspect, feature, structure, or characteristic with other embodiments.

[0029] As used herein, the term "a" before a noun refers to one or more of that particular noun. For example, the phrase "a mammalian cell" refers to "one or more mammalian cells".

[0030] The terms "tangential flow filtration unit" or "TFF unit" are known in the art and refer to a device comprising at least one housing (such as a cylinder) and at least one cross-flow (tangential) viral filter in which most of the surface of the filter is located within the housing so as to be parallel to the flow of fluid (such as a cell culture fluid) passing through the unit. TFF units are well known in the art and are commercially available. The housing can include a first inlet / outlet and a second inlet / outlet, which are positioned such that, for example, fluid passes through the first inlet / outlet, across at least one cross-flow filter, and through the second inlet / outlet. In some examples, a circuit system can include a plurality of TFF units connected in series and / or in parallel. For example, a circuit system including two or more TFF units can include fluid conduits that fluidly connect pairs of adjacent TFF units within the system. In other examples, a circuit system can include two or more sets of two or more TFF units fluidly connected by fluid conduits. Any of the TFF units described herein or known in the art can receive fluid in a first flow direction and a second flow direction.

[0031] The term "tangential flow virus filtration unit" or "TFVF unit" is known in the art and means a device comprising at least one housing (such as a cylinder) and at least one cross-flow (tangential flow) filter in which most of the surface of the virus filter is located within the housing so as to be parallel to the flow of fluid (e.g., cell culture fluid) passing through the unit. The housing can include a first inlet / outlet and a second inlet / outlet, which are positioned such that, for example, fluid passes through the first inlet / outlet, across at least one cross-flow virus filter, and through the second inlet / outlet. In some examples, a circuit system can include a plurality of TFVF units connected in series and / or in parallel. For example, a circuit system including two or more TFVF units can include fluid conduits that fluidly couple pairs of adjacent TFVF units within the system. In other examples, a circuit system can include two or more sets of two or more TFVF units fluidly coupled by fluid conduits. Any of the TFVF units described herein or known in the art can receive fluid in a first flow direction and a second flow direction.

[0032] The term "cross-flow filter" or "tangential flow filter" is known in the art and means a filter designed to be positioned within a TFF unit or TFVF unit such that most of the surface of the filter is parallel to the flow of fluid (e.g., fluid containing a recombinant therapeutic protein) (e.g., a first and a second flow direction). For example, a cross-flow filter can have any shape that allows for filtration of tangential flow, such as a tubular or rectangular shape. A particularly useful cross-flow filter is designed such that when fluid flows across the surface of the cross-flow filter (e.g., flows in one direction and then in two directions), the fluid turbulence or shear stress of the fluid (e.g., cell culture fluid) is reduced. Cross-flow filters are commercially available from, for example, Sartorius, MembraPure, Millipore, and Pall Corporation.

[0033] The term "low-turbulence pump" or "LTP" is known in the art and refers to a device that can move a fluid (e.g., a fluid containing a recombinant therapeutic protein) in a single direction (e.g., a first or second flow direction) within a system or circuit, or a device that can reversibly flow a fluid (e.g., a fluid containing a recombinant therapeutic protein) in two directions (a first and a second flow direction) within a system without inducing large shear stress or fluid turbulence in the fluid (e.g., a fluid containing a recombinant therapeutic protein). When the LTP is used to alternately flow a fluid (e.g., a fluid containing a recombinant therapeutic protein) in the first and second flow directions, the second flow direction is substantially opposite to the first flow direction. Examples of LTPs include peristaltic pumps. Other examples of LTPs are known in the art.

[0034] The term "mammalian cell" means any cell of or derived from any mammal (e.g., human, hamster, mouse, monkey, rat, pig, cow, rabbit). For example, the mammalian cell may be an immortalized cell. In some embodiments, the mammalian cell is a differentiated cell. In some embodiments, the mammalian cell is an undifferentiated cell. Non-limiting examples of mammalian cells are described herein. Additional examples of mammalian cells are known in the art.

[0035] The term "substantially free of" means that a composition (e.g., a liquid medium) contains at least or about 90% less (e.g., at least or about 95%, 96%, 97%, 98%, or at least or about 99% less, or about 100% less) of a particular substance (e.g., a mammalian cell).

[0036] The term "0.5× volume" means about 50% of the volume. The term "0.6× volume" means about 60% of the volume. Similarly, "0.7×", "0.8×", "0.9×", "1.0×" mean about 70%, 80%, 90%, or 100% of the volume, respectively.

[0037] The term "culture" or "cell culture" means maintaining or growing mammalian cells under a controlled set of physical conditions.

[0038] The term "culture of mammalian cells" means a liquid medium containing a plurality of mammalian cells maintained or grown under a controlled set of physical conditions.

[0039] The term "liquid medium" means a fluid containing sufficient nutrients to grow or proliferate cells (e.g., mammalian cells) in vitro. For example, the liquid medium may contain one or more of: amino acids (e.g., 20 amino acids), purines (e.g., hypoxanthine), pyrimidines (e.g., thymidine), choline, inositol, thiamine, folic acid, biotin, calcium, niacinamide, pyridoxine, riboflavin, thymidine, cyanocobalamin, pyruvic acid, lipoic acid, magnesium, glucose, sodium, potassium, iron, copper, zinc, and sodium bicarbonate. In some embodiments, the liquid medium may contain mammalian serum. In some embodiments, the liquid medium does not contain mammalian serum or other extracts (defined liquid medium). In some embodiments, the liquid medium may contain trace metals, mammalian growth hormones, and / or mammalian growth factors. Another example of a liquid medium is a minimal medium (e.g., a medium containing only inorganic salts, a carbon source, and water). Non-limiting examples of liquid media are described herein. Additional examples of liquid media are known in the art and are commercially available. The liquid medium may contain mammalian cells at any density. For example, herein, an amount of liquid medium removed from a bioreactor may be substantially free of mammalian cells.

[0040] The term "animal component-free liquid medium" means a liquid medium that does not contain any components derived from mammals (e.g., proteins or serum).

[0041] The term "serum-free liquid medium" means a liquid medium that does not contain mammalian serum.

[0042] "Serum-containing liquid medium" means a liquid medium containing mammalian serum.

[0043] "Chemically defined liquid medium" is a technical term and means a liquid medium in which all of the chemical components are known. For example, a chemically defined liquid medium does not contain fetal bovine serum, bovine serum albumin, or human serum albumin. The reason is that these preparations usually contain a complex mixture of albumin and lipids.

[0044] The term "protein-free liquid medium" means a liquid medium that does not contain any protein (e.g., any detectable protein).

[0045] The term "agitation" means to stir or otherwise move a portion of the liquid medium within a bioreactor. Agitation is performed, for example, to increase the dissolved O2 concentration in the liquid medium within the bioreactor. Agitation can be performed by any method known in the art, such as using an instrument or a propeller. Exemplary devices and methods for agitating a portion of the liquid medium within a bioreactor are known in the art.

[0046] The term "therapeutic protein drug substance" means a recombinant protein (e.g., an immunoglobulin, a protein fragment, an artificial protein, or an enzyme) that has been sufficiently purified or separated from contaminating proteins, lipids, and nucleic acids (e.g., contaminating proteins, lipids, and nucleic acids present in a liquid medium or from a host cell (e.g., a mammalian, yeast, or bacterial host cell)) and biological contaminants (e.g., viral and bacterial contaminants) and can be formulated into a pharmaceutical without any further substantial purification and / or decontamination steps.

[0047] The term "integrated process" means a process that is carried out using structural elements that function in concert to obtain a particular result (for example, generating a therapeutic protein drug substance from a liquid medium).

[0048] The term "continuous process" means a process in which fluid is continuously supplied from at least a portion of a system. For example, in any of the exemplary continuous biological manufacturing systems described herein, a liquid medium containing a recombinant therapeutic protein is continuously supplied to the system while the system is operating, and the therapeutic protein drug substance is delivered from the system. In another example, a continuous process is a process in which a liquid medium containing a recombinant therapeutic protein is continuously supplied from a bioreactor through a first MCCS. Another example of a continuous process is a process in which a liquid medium containing a recombinant therapeutic protein is continuously supplied from a bioreactor through a first and a second MCCS. Additional examples include a process in which a liquid medium containing a recombinant therapeutic protein is continuously supplied through a first MCCS, a process in which a liquid medium containing a recombinant therapeutic protein is continuously supplied through a first and a second MCCS, or a process in which a fluid containing a recombinant therapeutic protein is continuously supplied through a second MCCS.

[0049] The term "immunoglobulin" means a polypeptide comprising an amino acid sequence of at least 15 amino acids (e.g., at least 20, 30, 40, 50, 60, 70, 80, 90, or 100 amino acids) of an immunoglobulin protein (e.g., a variable domain sequence, a framework sequence, or a constant domain sequence). The immunoglobulin can comprise, for example, at least 15 amino acids of a light chain immunoglobulin, such as at least 15 amino acids of a heavy chain immunoglobulin. The immunoglobulin can be an isolated antibody (e.g., IgG, IgE, IgD, IgA, or IgM). The immunoglobulin can be a subclass of IgG (e.g., IgG1, IgG2, IgG3, or IgG4). The immunoglobulin can be an antibody fragment, such as a Fab fragment, an F(ab’)2 fragment, or an scFv fragment. The immunoglobulin can also be a bispecific or trispecific antibody, or a dimeric, trimeric, or multimeric antibody, or a bispecific antibody, an Affibody® or a Nanobody®. The immunoglobulin can also be a modified protein (e.g., a fusion protein) comprising at least one immunoglobulin domain. Non-limiting examples of immunoglobulins are described herein, and additional examples of immunoglobulins are known in the art.

[0050] The term "protein fragment" or "polypeptide fragment" means a portion of a polypeptide sequence, where this portion is at least or about 4 amino acids in length, at least or about 5 amino acids in length, at least or about 6 amino acids in length, at least or about 7 amino acids in length, at least or about 8 amino acids in length, at least or about 9 amino acids in length, at least or about 10 amino acids in length, at least or about 11 amino acids in length, at least or about 12 amino acids in length, at least or about 13 amino acids in length, at least or about 14 amino acids in length, at least or about 15 amino acids in length, at least or about 16 amino acids in length, at least or about 17 amino acids in length, at least or about 18 amino acids in length, at least or about 19 amino acids in length, or at least or about 20 amino acids in length, or more than 20 amino acids in length. Recombinant protein fragments can be generated using any of the processes described herein.

[0051] The term "modified protein" means a polypeptide that is not naturally encoded by an endogenous nucleic acid present within an organism (e.g., a mammal). Examples of modified proteins include enzymes (e.g., where one or more amino acids have been substituted, deleted, inserted, or added to increase the stability and / or catalytic activity of the modified enzyme), fusion proteins, antibodies (e.g., bivalent antibodies, trivalent antibodies, or bispecific antibodies), and antigen-binding proteins that contain at least one recombinant scaffold sequence.

[0052] The term "multi-column chromatography system" or "MCCS" means a system of two or more interconnected or switchable chromatography columns and / or chromatography membranes. Non-limiting examples of multi-column chromatography systems include periodic countercurrent chromatography systems (PCCs) that include two or more interconnected or switchable chromatography columns and / or chromatography membranes. Further examples of multi-column chromatography systems are described herein and are known in the art.

[0053] The term "capture" means the steps performed to partially purify or isolate (e.g., to a weight purity of at least or about 5%, e.g., at least or about 10%, 15%, 20%, 25%, 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or at least or about 95%), concentrate, and stabilize a recombinant therapeutic protein from one or more other components present in a liquid culture medium or a diluted liquid culture medium (e.g., a medium protein present in or secreted from mammalian cells or one or more other components (e.g., DNA, RNA, other proteins)). Typically, capture is performed using a resin that binds to the recombinant therapeutic protein (e.g., by using affinity chromatography). Non-limiting methods for capturing a recombinant therapeutic protein from a liquid culture medium or a diluted liquid culture medium are described herein, and others are known in the art. The recombinant therapeutic protein can be captured from the liquid culture medium using at least one chromatography column and / or chromatography membrane (e.g., any of the chromatography columns and / or chromatography membranes described herein).

[0054] The term "purification" means the steps carried out to separate a recombinant therapeutic protein from one or more other impurities (e.g., bulk impurities) or components (e.g., liquid media proteins present in or secreted from mammalian cells or one or more other components (e.g., DNA, RNA, other proteins, endotoxins, viruses, etc.)) present in a fluid containing the recombinant therapeutic protein. For example, purification can be carried out during or after the initial capture step. Purification can be performed using a resin, membrane, or any other solid support that binds to the recombinant therapeutic protein or contaminants, (e.g., by using affinity chromatography, hydrophobic interaction chromatography, anion or cation exchange chromatography, or molecular sieve chromatography). The recombinant therapeutic protein can be purified from a fluid containing the recombinant therapeutic protein using at least one chromatography column and / or chromatography membrane (e.g., any of the chromatography columns or chromatography membranes described herein).

[0055] The term "polishing" is a technical term and means the steps carried out to remove residual trace or small amounts of contaminants or impurities from a fluid containing a recombinant therapeutic protein that is close to the final desired purity. For example, polishing can be performed by passing a fluid containing the recombinant therapeutic protein through a chromatography column or membrane absorber that selectively binds to the recombinant therapeutic protein of interest or to small amounts of contaminants or impurities present in the fluid containing the recombinant therapeutic protein. In such an example, the eluate / filtrate of the chromatography column or the membrane absorber contains the recombinant therapeutic protein.

[0056] The term "eluate / filtrate" is a technical term and means a fluid containing a detectable amount of a recombinant therapeutic protein that is discharged from a chromatography column or chromatography membrane.

[0057] The term "filtering" means removing at least a portion (e.g., at least 80%, 90%, 95%, 96%, 97%, 98%, or 99%) of unwanted biological contaminants (e.g., mammalian cells, bacteria, yeast cells, viruses, or mycobacteria) and / or particulate matter (e.g., precipitated proteins) from a liquid (e.g., a liquid medium or fluid present in any of the systems or processes described herein).

[0058] The term "secreted protein" or "secreted recombinant protein" means a protein (e.g., a recombinant protein) that originally contained at least one secretion signal sequence when translated within a mammalian cell and was at least partially secreted into the extracellular space (e.g., a liquid medium) by at least partially enzymatically cleaving the secretion signal sequence within the mammalian cell. One of ordinary skill in the art will understand that a "secreted" protein need not be completely dissociated from the cell to be considered a secreted protein.

[0059] The term "perfusion bioreactor" means a bioreactor containing a plurality of cells (e.g., mammalian cells) in a first liquid medium, and culturing the cells present in the bioreactor includes periodically or continuously removing the first liquid medium and, simultaneously or immediately thereafter, adding a substantially equal amount of a second liquid medium to the bioreactor. In some examples, there is a gradual change (e.g., an increase or decrease) in the amount of the first liquid medium removed and added over a gradual period (e.g., a period of about 24 hours, a period between about 1 minute and about 24 hours, or a period longer than 24 hours) during the culture period (e.g., a daily medium resupply rate). The proportion of medium removed and replaced daily can vary depending on the particular cells being cultured, the initial seeding density, and the cell density at a particular time. The term "RV" or "reactor volume" means the amount of medium present at the start of the culture process (e.g., the total amount of medium present after seeding).

[0060] The term "fed-batch bioreactor" is a technical term and means a bioreactor containing a plurality of cells (e.g., mammalian cells) in a first liquid medium, and culturing the cells present in the bioreactor includes periodically or continuously adding a second liquid medium to the first liquid medium without substantially removing the first liquid medium or the second liquid medium from the cell culture. The second liquid medium may be the same as the first liquid medium. In some examples of fed-batch culture, the second liquid medium is a concentrated form of the first liquid medium. In some examples of fed-batch culture, the second liquid medium is added as a dry powder.

[0061] The term "clarified liquid medium" means a liquid medium obtained from the culture of bacteria or yeast cells that is substantially free (e.g., contains at least 80%, 85%, 90%, 92%, 94%, 96%, 98%, or 99% less) of bacteria or yeast cells.

[0062] The term "unit operation" is a technical term and means a functional step that can be performed in the process of manufacturing a therapeutic protein drug substance from a liquid medium. For example, the unit of operation can be filtering (e.g., removing contaminating bacteria, yeast viruses, or mycobacteria, and / or certain substances from a fluid containing a recombinant therapeutic protein), capturing, removing epitope tags, purifying, holding or storing, polishing, inactivating viruses, adjusting the ionic concentration and / or pH of a fluid containing a recombinant therapeutic protein, and removing unwanted salts.

[0063] "Specific productivity" or "SPR" is a technical term and herein refers to the mass or enzyme activity of a recombinant therapeutic protein produced per mammalian cell per day. The SPR of a recombinant therapeutic antibody is typically measured as mass / cell / day. The SPR of a recombinant therapeutic enzyme is typically measured as unit / cell / day or (unit / mass) / cell / day.

[0064] "Volume production rate" or "VPR" is a technical term and, as used herein, refers to the mass or enzyme activity of a recombinant therapeutic protein produced per day per unit of culture volume (e.g., per liter of bioreactor, vessel, or tubing volume). The VPR of a recombinant therapeutic antibody pharmaceutical is typically measured as mass / L / day. The VPR of a recombinant therapeutic enzyme is typically measured as units / L / day or mass / L / day.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Methods and materials similar or equivalent to those described herein can be used in the practice of this method and system, but the appropriate methods and systems are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, this specification, including definitions, will control. In addition, the methods and examples are illustrative only and not limiting.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0067] Like reference symbols indicate like elements.

[0068] Introduction Biomanufacturing systems are expected to produce a variety of different biological products, including therapeutic drug species such as recombinant proteins, on a large scale. In many such systems, an appropriate cell culture fluid is combined with a flow of growth medium, buffer, and other input reagents in a bioreactor (e.g., a perfusion reactor) to produce a product substance. The process fluid is extracted from the bioreactor and purified, usually by one or more multi-column chromatography purification units, to separate the desired product from the process fluid. Aspects of biomanufacturing systems and their associated components are described, for example, in PCT Patent Application Publication No. WO2018 / 035116, the entire content of which is incorporated herein by reference.

[0069] A biomanufacturing system also typically includes a virus filtration stage or subsystem for removing virus particles from the process fluid. The virus filtration subsystem is generally implemented in a variety of different configurations. For example, some biomanufacturing systems include a pressure-driven virus filtration subsystem. FIG. 1 is a schematic diagram of a pressure-driven virus filtration subsystem 100. The subsystem 100 includes a supply container 102, a transport conduit 106, and a filter unit 108 having an internal filter membrane 110. During operation of the subsystem 100, a fluid 104 (such as a process fluid extracted from a bioreactor or from another component of the biomanufacturing system downstream of the bioreactor) is continuously or batchwise introduced into the supply container 102. The supply container 102 is pressurized such that the gas pressure within the supply container 102 is significantly greater than atmospheric pressure, creating a pressure gradient with respect to the outlet of the subsystem that drives the flow of the fluid 104 from the supply container 102 through the conduit 106 and into the filter unit 108. Upon entering the filter unit 108, the fluid 104 passes through a filter member 110 that filters virus particles.

[0070] The flow of the fluid 104 within the subsystem 100 is completely pressure-driven, and the flux through the filter unit 108 is determined by a single parameter (the supply container gas pressure). Since the gas pressure on the downstream side of the filter member 110, including the product stream 112, is substantially atmospheric pressure, the pressure drop occurs only across the filter member 110. The product stream 112 corresponds to the fluid 104 from which virus particles have been removed.

[0071] In subsystem 100, it should be noted that virus particles, or other process impurities (such as host cell proteins, invisible particles, or the protein product itself), accumulate on the filter member 110. Therefore, the useful life of the filter member 110 is limited to the elapsed time until virus breakthrough or filter clogging occurs and virus particles in the fluid 104 upstream of the filter member 110 are no longer completely captured by the filter member 110 (i.e., a certain number of particles pass through the filter member 110 and appear in the product stream 112). Thus, the subsystem 100 can be realized with a fairly simple configuration, providing effective virus particle filtration. However, since the filter member 110 is prone to fouling during operation, the effect of this type of virus filtration is limited and its cost may increase. Due to the relatively short operating period until the filter member 110 is replaced, the subsystem 100 may be more suitable for batch operation rather than continuous virus filtration operation as part of a continuous biomanufacturing process.

[0072] Figure 2 is a schematic view of a tangential flow filtration subsystem 200. The subsystem 200 includes a supply container 202 that holds a fluid 220 (e.g., a process fluid containing one or more products from a bioreactor). The subsystem 200 is pump-driven and includes a pump 206. During operation, the pump 206 drives the fluid 220 from the supply container 202 through conduits 204 and 208 to a filter unit 210 that includes a filter member 212. The filter member 212 is typically, for example, a flat membrane and is oriented generally tangentially to the direction of flow of the fluid 220 within the filter unit 210. Specifically, within the filter unit 210, the fluid 220 flows from an inlet 224 to an outlet 226 in a direction generally along the length of the filter unit 210 as indicated by arrow 228. As the fluid actively flows in direction 228, a portion of the fluid moves tangentially through the member 212 in the direction of outlet 230. The fluid moving tangentially is filtered by the member 212 to remove viral particles, so the product stream 222 exiting through outlet 230 is free of viral particles. The fluid 220 that does not pass through the filter member 212 exits the filter unit 210 through outlet 226 as a residue and recirculates back to the original supply container 202 via conduits 214 and 218. A flow control device 216 can be used to regulate the pressure of the residue.

[0073] In practice, the rate at which the filtered product stream is produced in the subsystem 200 is controlled by two process variables: the flow rate of the fluid 220 controlled by the pump 206 and the pressure of the residue controlled by the flow control device 216. Pressure drops occur at multiple locations within the subsystem 200 (i.e., between the inlet 224 and the outlets 230 and 226, as well as between the outlet 226 and the supply container 202).

[0074] The tangential flow virus filtration (TFVF) subsystem has several advantages compared to conventional "dead-end" filtration systems such as that shown in FIG. 1. In TFVF, the flux of fluid 220 is maintained across member 212 by the "sweeping" flow motion of fluid 220, whereby a high throughput is obtained per unit area of the filter membrane. Thus, the TFVF subsystem is suitable for realizing a continuous biomanufacturing system. This is because the TFVF subsystem can handle the continuous inflow of process fluid from the bioreactor and produce a continuous outflow of the product stream for further purification and / or analysis. The TFVF subsystem can also be implemented to extend the life of the virus filtration membrane in a batch biomanufacturing system due to the relatively low fouling of the filter provided in the tangential operating mode. The limitations of the TFVF subsystem may in some cases include that the set of filter members available is generally limited and the use of a recirculation pump, which can impose some operating constraints on the subsystem.

[0075] It is possible to implement a TFVF subsystem that is both pressure-driven and pump-driven. Figure 3 is a schematic diagram of such a subsystem 300, which includes a supply container 302, a filter unit 304, and a recirculation pump 306. These components function in the same manner as the corresponding components in Figure 2 above. During operation, the supply container 302 is pressurized by feeding air or other gas from the inlet 312. The fluid 308 flows from the supply container 302 to the filter unit 304 that includes a tangentially oriented filter member 314. As the fluid 308 flows across the entire member 314, a portion of the fluid passes through the membrane 314, which removes virus particles from the fluid, such that the product stream 310 exiting the filter unit 304 is free of virus particles. The fluid that does not diffuse through the filter member 314 exits the filter unit 304 as a residue and is recirculated to the original supply container 302 by the pump 306. Thus, in the subsystem 300, both the pressurized supply container 302 and the pump 306 drive the circulation of the fluid 308 through the subsystem.

[0076] As described above, to control the circulation of the fluid 308 through the subsystem 300, two operating parameters are adjusted: the recirculation flow rate (determined by the pump 306) and the system fluid pressure (by pressurizing the supply container 302). One advantage of the subsystem 300 is that the fluid pressure remains substantially constant in the recirculation portion of the subsystem. That is, the fluid pressure in the supply container 302, the fluid pressure at the inlet of the filter member 314, and the fluid pressure of the residue exiting the filter member 314 are approximately the same. In the subsystem 300, the only significant pressure drop occurs across the filter member 314. As a result, the rate at which the product stream exits the filter member 314 is relatively easy to control.

[0077] Subsystem 300 is an example of a constant-pressure system. By appropriately adjusting pump 306, subsystem 300 can also be operated at a constant tangential flow rate, ensuring that a continuous product stream 310 exits the filter unit 304 at a constant velocity. A constant-pressure, constant-tangential-flow filtration subsystem can also be implemented in another way. FIG. 4 is a schematic diagram showing another example of a filtration subsystem 400, including a supply container 402, a conduit 404 connected between the supply container 402 and the filter unit 406, a conduit 408 connected between the filter unit 406 and the pump 410, and a conduit 412 connected between the pump 410 and the inlet 414 of the supply container 402.

[0078] During operation of subsystem 400, air or another gas is fed from inlet 424 into supply container 402, pressurizing the interior of the supply container. Due to the fluid pressure within supply container 402, a fluid 426 present within the supply container (e.g., a process fluid obtained from a bioreactor, or a process fluid obtained from an intermediate purification stage of a biomanufacturing system) is transported from the supply container through conduit 404 into filter unit 406. Filter unit 406 includes a filter member (not shown in FIG. 4) oriented such that fluid 426 within filter unit 406 flows in a direction that contacts (or nearly contacts) the surface of the filter member. A portion of fluid 426 passes through the filter member and exits filter unit 406 via outlet 430 as product stream 428 with little or no viral load. The remaining fluid 426 exits filter unit 406 as a residue via outlet 432 and is circulated by pump 410 through conduits 408 and 412. Pump 410 drives the flow of the residue back to supply container 402 via inlet 414. As a result, subsystem 400 can continuously filter fluid 426, with a portion of fluid 426 being removed from the subsystem as filtered product stream 428 and the remaining fluid 426 being recirculated to pass through filter unit 406 again. Additional fluid 426 is introduced into subsystem 400 via conduits 416 and one-way valve 418, either before or during operation; the additional fluid 426 is introduced into supply container 402 via inlet 420.

[0079] The structure of the filter unit 406 and the filter member therein is different from the corresponding filter unit in FIG. 3. In FIG. 4, the filter unit 406 includes a hollow fiber-based filter member. FIG. 5 is a schematic cross-sectional view showing an example of the filter member 406. The filter unit 406 includes a filter body 502, a filter member 504, and an outlet 430. The conduits 404 and 408 are connected to internal channels within the filter body 502. As is apparent from FIG. 5, the filter body 502 is formed of hollow fibers, and apertures are formed in the side walls of the fibers. The filter member 504 is in contact with the side walls of the fibers and has a substantially tubular structure. The fluid 426 enters the filter body 520 and flows in the direction indicated by the arrow in FIG. 5. A portion of the fluid 426 passes through the filter member 504 and exits through the outlet 430 as a product stream. The remaining fluid 426 exits as a residue and enters the conduit 408, where it is recirculated by a pump (e.g., pump 410).

[0080] In a dead-end filter unit (e.g., as shown in FIG. 1), the fluid pressure within the filter unit that drives the fluid flow through the filter also compresses solid material against the front of the filter, thereby reducing the open volume within the filter member and thus reducing throughput. In fluids where solids are fairly suspended, fouling of the filter member can occur relatively quickly.

[0081] The filter unit 406 has several advantages compared to such dead-end filter units. Since the fluid 426 flows tangentially to the side walls of the filter body 502 and the filter member 504, the cross-flow of the fluid 426 helps to "wash away" solid particles from the surface of the filter member 504, which helps to reduce the rate at which the surface of the filter member becomes fouled.

[0082] Furthermore, both the flow rate of fluid 426 across the surface of filter member 504 (referred to as the "cross-flow rate") and the fluid pressure within filter member 504 are adjusted by respectively adjusting the pump 410 and the internal pressure of supply container 402. When fluid 426 flows through filter member 504 and filter body 502, an intermembrane pressure (TMP) is applied across the thickness of filter member 504. The TMP is adjusted by changing the cross-flow rate (e.g., with pump 410) and / or by changing the fluid pressure within container 402. The TMP pressure drives a portion of fluid 426 through filter member 504, filtering virus particles from the fluid to produce product stream 428. Due to the cross-flow cleaning action of fluid 426 and the adjustability of the cross-flow rate and TMP, filter unit 406 can typically operate for a significantly longer period until fouling occurs and replacement is required compared to an equivalent dead-end filter unit.

[0083] Typically, virus filter members are not used in tangential flow filtration systems, but rather in dead-end filtration systems such as shown in FIG. 1. In virus filtration of dead-end systems, virus filter members are typically relatively thin to ensure a high flow rate (e.g., high flux) of fluid through the filter member. As discussed above, such virus filter members tend to foul relatively quickly and are thus not well-suited for continuous filtration operations over periods of days or weeks.

[0084] Continuous Virus Filtration To continuously perform virus filtration on a process fluid directly extracted from a bioreactor or a process fluid extracted from an intermediate purification stage of a biomanufacturing system, the inventors implemented a tangential flow virus filtration subsystem shown in FIGS. 4 and 5. Furthermore, the inventors discovered that such a subsystem, particularly the virus filter member, can be configured in various ways to reduce the rate at which the filter member fouls, potentially allowing for an extended period of continuous operation.

[0085] In some embodiments, the tangential flow virus filtration subsystem is configured such that the lateral fluid pressure (i.e., transmembrane pressure) applied to the filter member is between 0 psi and 50 psi (e.g., between 0 psi and 45 psi, between 0 psi and 40 psi, between 0 psi and 35 psi, between 0 psi and 30 psi, between 0 psi and 25 psi, between 0 psi and 20 psi, between 0 psi and 15 psi, between 0 psi and 10 psi, between 5 psi and 50 psi, between 5 psi and 40 psi, between 5 psi and 30 psi, between 5 psi and 20 psi, between 10 psi and 50 psi, between 10 psi and 40 psi, between 10 psi and 30 psi, between 10 psi and 20 psi, between 15 psi and 50 psi, between 15 psi and 40 psi, between 15 psi and 30 psi, between 20 psi and 50 psi, between 20 psi and 40 psi, between 25 psi and 50 psi, or any pressure range between 0 psi and 50 psi). In some embodiments, the lateral fluid pressure applied to the filter member is 50 psi or less (e.g., 45 psi or less, 40 psi or less, 35 psi or less, 30 psi or less, 25 psi or less, 20 psi or less, 15 psi or less, 10 psi or less, 5 psi or less, 4 psi or less, 3 psi or less, 2 psi or less, 1 psi or less, 0.5 psi or less, 0.25 psi or less, or even less).

[0086] Generally, by selecting a low lateral fluid pressure, the flux across the filter member is reduced, thereby reducing the rate at which the product stream is produced. However, it has been observed by the inventors that when the lateral fluid pressure is low, the useful life of the virus filter member is increased by increasing the elapsed time until virus breakthrough on the outer surface of the filter member.

[0087] FIG. 6 is a schematic cross-sectional view of the virus filter member 602. The filter member 602 includes a first surface 604 and a second surface 606. A plurality of channels 612 extend through the filter member from the first surface 604 to the second surface 606. A fluid 608 containing virus particles 610 encounters the first surface 604 of the filter member and flows through the channels 612 from the first surface 604 to the second surface 606. As the fluid 608 flows through the channels 612, the virus particles 610 adsorb to the channel walls where they are retained, so that the product stream emerging from the second surface 606 is substantially free of virus particles before the filter member becomes contaminated.

[0088] Although not wishing to be bound by theory, if virus particles are within the channels 612, it is believed that fluid transport will carry the virus particles towards the second surface 606. Further, even adsorbed virus particles can desorb by Brownian motion or fluid transport and propagate towards the second surface 606. By reducing the lateral fluid pressure applied to the filter member, the fluid flow rate through the membrane is reduced, thereby reducing the rate at which virus particles are transported towards the second surface 606 and extending the life of the filter member until virus breakthrough at the second surface.

[0089] In some embodiments, the thickness of the filter member (shown as "d" between the first and second faces of the filter member in FIG. 6) is considerably thicker than the thickness of a standard tangential direction filter membrane. For example, conventional filter membranes for use in tangential direction filtration operations have a thickness in the range of about 20 micrometers to 140 micrometers. The filter member 602 used in the tangential flow virus filtration subsystem described herein can have a thickness d of 150 micrometers or more (e.g., 160 micrometers or more, 170 micrometers or more, 180 micrometers or more, 190 micrometers or more, 200 micrometers or more, 220 micrometers or more, 240 micrometers or more, 260 micrometers or more, 280 micrometers or more, 300 micrometers or more, 320 micrometers or more, 340 micrometers or more, 350 micrometers or more, 370 micrometers or more, 400 micrometers or more, 450 micrometers or more, and even more).

[0090] In some embodiments, the thickness of the filter member between the first surface and the second surface is different. For example, the minimum thickness of the filter member between each surface can be 50 micrometers or more (e.g., 60 micrometers or more, 70 micrometers or more, 80 micrometers or more, 90 micrometers or more, 100 micrometers or more, 110 micrometers or more, 120 micrometers or more, 130 micrometers or more, 140 micrometers or more, 150 micrometers or more, 160 micrometers or more, 170 micrometers or more, 180 micrometers or more, 190 micrometers or more, 200 micrometers or more), and the maximum thickness of the filter member between each surface can be 1000 micrometers or less (e.g., 900 micrometers or less, 800 micrometers or less, 700 micrometers or less, 600 micrometers or less, 500 micrometers or less, 475 micrometers or less, 450 micrometers or less, 425 micrometers or less, 400 micrometers or less, 375 micrometers or less, 350 micrometers or less, 325 micrometers or less, 300 micrometers or less, or even less).

[0091] The thickness of the filter member between the first surface and the second surface may vary randomly or regularly. FIGS. 7A - 7E are schematic views showing examples of the filter member 602 having different thicknesses between the first surface 604 and the second surface 606. In FIG. 7A, the thickness of the filter member changes irregularly along the length of the member. In FIG. 7B, the thickness of the filter member changes regularly, and the second surface 606 has undulations, vibrations, or a sine wave pattern of mountains and valleys. In FIG. 7C, the thickness of the filter member changes regularly, the second surface has a sawtooth shape to form a pattern of mountains and valleys, and the thickness of the member changes linearly between the mountains and valleys. In FIG. 7D, the thickness of the filter member changes monotonically along the length of the member. The thickness can change linearly or non - linearly along the length of the member. In FIG. 7E, the thickness of the filter member changes step - wise.

[0092] Generally, during the tangential flow virus filtration operation, the flow rate of the fluid passing through the filter member is selected such that the flux of the product stream is high enough to ensure maintaining the continuous manufacturing operation, while at the same time being low enough to ensure that virus particles do not break through the filter member and appear in the product stream. For example, per unit area of the filter member, the flow rate can be at least 0.5 L / m 2 / h (e.g., at least 1.0 L / m 2 / h, at least 2.0 L / m 2 / h, at least 5.0 L / m 2 / h, at least 10.0 L / m 2 / h, at least 15.0 L / m 2 / h, at least 20.0 L / m 2 / h, at least 30.0 L / m 2 / h, at least 40.0 L / m 2 / h). The flow rate can further or alternatively be 100 L / m 2 / h or less (e.g., 90 L / m 2 / h or less, 80 L / m 2 / h or less, 70 L / m 2 / h or less, 60 L / m 2 / h or less).

[0093] The bulk porosity of the filter member is generally selected to balance the flow rate of the fluid passing through the member, the virus particle retention capacity of the member, and the mechanical strength of the member. In some embodiments, the porosity of the filter member (i.e., the pore volume fraction of the filter member) is 0.05 or more (e.g., 0.10 or more, 0.15 or more, 0.20 or more, 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, 0.50 or more, 0.55 or more, 0.60 or more, or even more). In some embodiments, the porosity of the filter member is 0.90 or less (e.g., 0.88 or less, 0.86 or less, 0.84 or less, 0.82 or less, 0.80 or less, 0.78 or less, 0.76 or less, 0.74 or less, 0.72 or less, 0.70 or less, or even less). The porosity of the filter member can be, for example, between 0.30 and 0.90, or any narrower range within this range.

[0094] In some embodiments, the thickness of the filter member may be small compared to the lateral dimension of the filter member. For example, the filter member can have a maximum lateral dimension when spread out in a plane, and the ratio of the maximum lateral dimension of the filter member to the thickness of the filter member can be 5 or more (e.g., 10 or more, 15 or more, 20 or more, 30 or more, 40 or more, 50 or more, 75 or more, 100 or more).

[0095] The filter member is generally formed from a wide variety of materials. Examples of suitable materials include, but are not limited to, polyvinylidene fluoride (PVDF), hydrophilic PVDF, regenerated cellulose, and other materials used to construct chemically synthesized membranes. Filter manufacturing methods generally known in the art can be used and / or modified to manufacture the filter members described herein.

[0096] Channel structure The filter member includes pores or channels extending between a first face and a second face of the member, enabling fluid to pass through the filter member. At the same time, virus particles are captured within the pores (e.g., by adsorption), thereby preventing them from appearing in the product stream. In the following discussion, reference is made to "channels" in the filter member, but it should be understood that the term "pores" is also used to describe the same function.

[0097] FIG. 8A is a schematic cross-sectional view of a filter member 602 including a channel 802. The number density of channels per unit of the first face 604 of the filter member 602 can be, for example, between 100 / cm 2 and 10000 / cm 2 . That is, the number density of channels can be 100 / cm 2 or more (e.g., 200 / cm 2 or more, 300 / cm 2 or more, 400 / cm 2 or more, 500 / cm 2 or more, 600 / cm 2 or more, 700 / cm 2 or more, 800 / cm 2 or more, 900 / cm 2 or more, 1000 / cm 2 or more, 1500 / cm 2 or more, 2000 / cm 2 or more, 2500 / cm 2 or more, 3000 / cm 2 or more, 3500 / cm 2 or more, 4000 / cm 2 or more, 4500 / cm 2 or more, and even more). The number density of channels can be 10000 / cm 2 or less (e.g., 9500 / cm 2 or less, 9000 / cm 2 or less, 8500 / cm 2 or less, 8000 / cm 2 or less, 7500 / cm 2 or less, 7000 / cm 2 or less, 6500 / cm 2 or less, 6000 / cm 2Hereinafter, 5500 / cm 2 hereinafter, and even less).

[0098] In some embodiments, the size of one or more of the openings of the channels formed in the filter member 602 on the first and second surfaces 604 and 606 is substantially the same (i.e., the cross-sectional area of each opening on these surfaces is within ±10% and the same). However, in some embodiments, the sizes of the openings are different. In particular, the filter member 602 is fabricated such that for each individual channel, the cross-sectional area of the channel opening on the first surface 604 is larger than the cross-sectional area of the channel opening on the second surface, so that the effective diameter of the channel becomes thinner through the body of the filter member. It has been discovered that using such tapered channels prevents the breakthrough of virus particles on the second surface 606. Without wishing to be bound by theory, this is thought to be due to the small size of the channel openings and also due to the reduction in the flow rate of the fluid through the channels.

[0099] FIG. 8B is a schematic view of a filter member 602 including a plurality of tapered channels 808 (for clarity, only one channel is shown in FIG. 8B). The opening 806 of the channel 804 on the first surface 604 of the filter member has a larger cross-sectional area than the opening of the channel 804 on the second surface 606 of the filter member. The cross-sectional area A1 of the opening 806 can generally be between 0.1 μm 2 and 10 μm 2 . For example, the cross-sectional area can be 0.1 μm 2 or more (e.g., 0.2 μm 2 or more, 0.3 μm 2 or more, 0.4 μm 2 or more, 0.5 μm 2 or more, 0.6 μm 2 or more, 0.7 μm 2 or more, 0.8 μm 2 or more, 0.9 μm 2 or more, 1.0 μm 2 or more, 2.0 μm 2 or more, 3.0 μm 2 or more, 4.0 μm2 5.0 μm or more 2 or more, and even more). Alternatively, or in addition, the cross-sectional area may be 10 μm 2 or less (for example, 9.5 μm 2 or less, 9.0 μm 2 or less, 8.5 μm 2 or less, 8.0 μm 2 or less, 7.5 μm 2 or less, 7.0 μm 2 or less, 6.5 μm 2 or less, 6.0 μm 2 or less, and even less).

[0100] The cross-sectional area of the opening 808 of the channel 804 is A2. Generally, the ratio A2 / A1 can be 1.0 or less (for example, 0.95 or less, 0.90 or less, 0.85 or less, 0.80 or less, 0.75 or less, 0.70 or less, 0.65 or less, 0.60 or less, 0.55 or less, 0.50 or less, 0.45 or less, 0.40 or less, 0.35 or less, 0.30 or less, and even less). Also, among the plurality of channels of the filter member 602, any of the channels can have the cross-sectional areas A1 and A2 as discussed above. Further, within one filter member, the cross-sectional areas A1 and / or A2 of the plurality of channels may be the same, or the cross-sectional areas A1 and / or A2 may be different.

[0101] Regarding the filter member 602 having a plurality of channels 804, the channels can have a cross-sectional area A1 with a certain distribution. The distribution of the average value of the cross-sectional area A1 can be between 0.1 μm 2 and 10 μm 2 . For example, the average value of the cross-sectional area can be 0.1 μm 2 or more (for example, 0.2 μm 2 or more, 0.3 μm 2 or more, 0.4 μm 2 or more, 0.5 μm 2 or more, 0.6 μm 2 or more, 0.7 μm 2 or more, 0.8 μm 2 or more, 0.9 μm 2 or more, 1.0 μm2 Above, 2.0 μm 2 Above, 3.0 μm 2 Above, 4.0 μm 2 Above, 5.0 μm 2 Above, or even more). Alternatively, or in addition, the average value of the cross-sectional area is 10 μm 2 Or less (for example, 9.5 μm 2 Or less, 9.0 μm 2 Or less, 8.5 μm 2 Or less, 8.0 μm 2 Or less, 7.5 μm 2 Or less, 7.0 μm 2 Or less, 6.5 μm 2 Or less, 6.0 μm 2 Or less, or even less).

[0102] The full width at half maximum (FWHM) value of the distribution of the cross-sectional area A1 is from 0.05 μm 2 To 5.0 μm 2 And can be between. For example, the FWHM value of the distribution is 0.05 μm 2 Or more (0.1 μm 2 Or more, 0.2 μm 2 Or more, 0.3 μm 2 Or more, 0.5 μm 2 Or more, 1.0 μm 2 Or more, 2.0 μm 2 Or more, or even more) and / or 5.0 μm 2 Or less (for example, 4.5 μm 2 Or less, 4.0 μm 2 Or less, 3.5 μm 2 Or less, 3.0 μm 2 Or less, or even less) and can be set as such.

[0103] The opening 806 of each channel 804 on the first surface 604 has a minimum opening dimension corresponding to the shortest distance passing through the mass center of the opening across the opening. For each opening 806, the minimum opening dimension can be 20 nm or more (e.g., 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, 45 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, 100 nm or more, 120 nm or more, 140 nm or more, 160 nm or more, 180 nm or more, 200 nm or more, 250 nm or more, and even more). For each opening 806, the minimum opening dimension can be 1 micrometer or less (e.g., 900 nm or less, 850 nm or less, 800 nm or less, 750 nm or less, 700 nm or less, 650 nm or less, 600 nm or less, 550 nm or less, 500 nm or less, 450 nm or less, 400 nm or less, and even less).

[0104] The distribution of the minimum opening dimensions between the openings 806 can have a full width at half maximum (FWHM) value of 500 nm or less (e.g., 450 nm or less, 400 nm or less, 350 nm or less, 300 nm or less, 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, 75 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nm or less, 15 nm or less, 10 nm or less, and even less).

[0105] Generally, the opening 808 of each channel 804 on the second surface 606 has a minimum opening dimension corresponding to the shortest distance passing through the mass center of the opening across the opening. For each opening 808, the minimum opening dimension can be either within the limits and ranges described above in relation to the opening 806. Similarly, the distribution of the minimum opening dimensions between the openings 808 can have a full width at half maximum (FWHM) value within either the limits or ranges described above in relation to the opening 806.

[0106] In some embodiments, the openings 806 of the channels 804 of the filter member 602 are irregularly distributed on the first surface 604 of the filter member 602. In some embodiments, the openings 806 are more regularly distributed. For example, the openings 806 can be distributed according to a regular pattern, and a rectangular array, a hexagonal array, or any other type of array pattern can be formed on the first surface 604. In some embodiments, the average distance between the centers of mass of the openings 806 on the first surface 604 is between 20 nm and 5 micrometers (e.g., between 30 nm and 5 micrometers, between 40 nm and 5 micrometers, between 50 nm and 5 micrometers, between 75 nm and 5 micrometers, between 100 nm and 5 micrometers, between 50 nm and 4 micrometers, between 50 nm and 3 micrometers, between 50 nm and 2 micrometers, between 100 nm and 4 micrometers, between 100 nm and 3 micrometers, between 100 nm and 2 micrometers, between 250 nm and 4 micrometers, between 250 nm and 3 micrometers, between 250 nm and 2 micrometers, between 250 nm and 1 micrometer, between 500 nm and 4 micrometers, between 500 nm and 3 micrometers, between 500 nm and 2 micrometers, between 1 micrometer and 4 micrometers, between 1 micrometer and 3 micrometers, or any other range within the aforementioned ranges).

[0107] FIG. 8C is a schematic view showing a portion of the first surface 604 including the openings 806 of the plurality of channels 804 formed in the filter member. The openings 806 are grouped as a plurality of groups 820, each of which is indicated by a dashed line surrounding the components of the group. On the first surface 604 where there are a plurality of openings 806, each opening has a minimum opening dimension corresponding to the shortest distance passing through the center of mass of the opening across the opening. For the plurality of openings 806 on the first surface 604, there is an average value of the minimum opening dimensions.

[0108] Generally, a given aperture 806 is part of a group if the distance between the centroid of that aperture and the centroid of another aperture within the group is less than twice the value of the average minimum aperture dimension of the first surface 604. For a group 820 of apertures 806 on the first surface 604, the center of each group is defined as the point where the sum of the distances to the centroid of each aperture within the group is minimized. Among the groups 820, the average center-to-center spacing between the closest groups can be made greater than 2.5 times (e.g., 3.0 times or more, 3.5 times or more, 4.0 times or more, 4.5 times or more, 5.0 times or more, 5.5 times or more, 6.0 times or more, 7.0 times or more, 8.0 times or more, 8.5 times or more, 9.0 times or more, 10.0 times or more, 12.0 times or more, 15.0 times or more, and even more) the average minimum aperture dimension of the first surface 604.

[0109] In some embodiments, as shown, for example, in FIG. 8B, one or more channels 804 are oriented such that the axis of the channel 804 is substantially parallel to the direction of fluid flow through the filter member 602. However, by orienting at least some of the channels 804 such that their respective channel axes are inclined with respect to the bulk direction of the fluid passing through the filter member 602, it has been found that the rate at which the filter member becomes dirty is significantly reduced, and thus the elapsed time until the filter member needs to be replaced can be significantly extended. Without wishing to be bound by theory, it is believed that by inclining the channel axis with respect to the bulk direction of the fluid flow, the interaction with virus particles along the length of the channel is increased, thereby enhancing the capture of virus particles.

[0110] FIG. 9A is a schematic view of a filter member 602 including inclined channels. In FIG. 9A, the cross-flow direction (i.e., within the filter unit) is indicated by arrow 902, and the direction of the bulk fluid flow within the filter member 602 (the tangential direction to the cross-flow direction 902) is indicated by arrow 904. The direction of the bulk fluid flow is nominally orthogonal to the first surface 604 and the second surface 606 of the filter member 602.

[0111] Channel 906 is formed in filter member 602 and has openings 910 and 912 in surfaces 604 and 606 respectively. Channel axis 908 extends between the respective centers of mass of openings 910 and 912. Channel axis 908 is inclined at an angle α with respect to the direction of bulk fluid flow 904.

[0112] In some embodiments, the percentage of channels in filter member 602 that are inclined with respect to the direction of bulk fluid flow is 20% or more (e.g., 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, 97% or more, 98% or more, 99% or more, and even 100%). For a given channel 906, the angle α can be 5 degrees or more (e.g., 10 degrees or more, 15 degrees or more, 20 degrees or more, 25 degrees or more, 30 degrees or more, 35 degrees or more, 40 degrees or more, 45 degrees or more, 50 degrees or more, and even more). Alternatively, or in addition, the angle α can be 90 degrees or less (e.g., 89 degrees or less, 88 degrees or less, 87 degrees or less, 86 degrees or less, 85 degrees or less, 80 degrees or less, 75 degrees or less, 70 degrees or less, 65 degrees or less, 60 degrees or less, and even less). The angle α can be between 1 degree and 90 degrees (or any narrower range within this range).

[0113] In some embodiments, among channels 906 in the filter member, the average value of the inclination angle α of the channels with respect to the direction 904 of bulk fluid flow is 5 degrees or more (e.g., 10 degrees or more, 15 degrees or more, 20 degrees or more, 25 degrees or more, 30 degrees or more, 35 degrees or more, 40 degrees or more, 45 degrees or more, 50 degrees or more, and even more). Alternatively, or in addition, the angle α can be 90 degrees or less (e.g., 89 degrees or less, 88 degrees or less, 87 degrees or less, 86 degrees or less, 85 degrees or less, 80 degrees or less, 75 degrees or less, 70 degrees or less, 65 degrees or less, 60 degrees or less, and even less). The angle α can be from 1 degree to 90 degrees (or any narrower range within this range).

[0114] In some embodiments, for channels 906 that are inclined with respect to the direction 904 of the bulk fluid flow, the full width at half maximum (FWHM) of the distribution of the angle α can be between 0 degrees and 60 degrees. For example, the FWHM of this distribution can be 60 degrees or less (e.g., 50 degrees or less, 40 degrees or less, 30 degrees or less, 20 degrees or less, 15 degrees or less, 10 degrees or less, 5 degrees or less).

[0115] In FIG. 9A, the channel 906 is inclined toward the cross-flow direction 902. However, in some embodiments, one or more of the channels formed in the filter member 602 are inclined away from the cross-flow direction 902 with respect to the bulk fluid flow direction 904 (i.e., in the counterclockwise direction in FIG. 9A). FIG. 9B is a schematic view showing the filter member 602 in which the channel 906 is inclined away from the cross-flow direction 902. The included angle between the bulk fluid flow direction 904 and the channel axis 908 is α. The various features described above in connection with FIG. 9A also apply to the channel 906 in FIG. 9B.

[0116] In some embodiments, the proportion of the channels in the filter member 602 that are inclined away from the cross-flow direction is 20% or more (e.g., 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, 97% or more, 98% or more, 99% or more, and even more). In some embodiments, when the filter member 602 is oriented such that some or all of the channels are inclined away from the cross-flow direction, it has been found that the useful life of the filter member can be further extended by reducing the rate at which virus particles desorb from internal bonding sites within the channels and break through the second surface 606 of the filter member.

[0117] Note that in FIG. 9A, channel 906 does not undulate or meander back and forth through filter member 602. However, in some embodiments, the channels in the filter member may extend in multiple directions with respect to the direction of the bulk fluid flow, for example, by undulating back and forth. However, the foregoing considerations also apply to such channels where the channel axis and the tilt angle are defined in the same way.

[0118] In some embodiments, for certain channels having a channel axis that is tilted or parallel with respect to the direction of the bulk fluid flow, the channel is partially covered or blocked at or near the channel opening. FIG. 10 is a schematic view of filter member 602 including channel 1006. Channel 1006 has a maximum cross-sectional dimension w as shown in the figure. However, at opening 1010, the maximum cross-sectional dimension is w0, which is smaller than w. The ratio w0 / w is generally selected such that a covered channel 1006 is obtained as needed. In some embodiments, for example, the ratio w0 / w is 0.98 or less (e.g., 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, 0.90 or less, 0.85 or less, 0.80 or less, 0.75 or less, 0.70 or less, 0.65 or less, 0.60 or less, 0.55 or less, 0.50 or less, 0.45 or less, 0.40 or less, 0.35 or less, 0.30 or less, 0.25 or less, 0.20 or less, and even less).

[0119] In some embodiments, the covering of the channel opening on the first surface 604 is measured with respect to a position immediately below the first surface 604. For example, referring again to FIG. 10, w n is the maximum cross-sectional dimension of channel 1006 at a position that is 10% of the distance between the first surface 604 and the second surface 606. For the partially covered channel 1006, w n can be greater than w0. In some embodiments, for example, the ratio w0 / w nis 0.99 or less (for example, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, 0.90 or less, 0.85 or less, 0.80 or less, 0.75 or less, 0.70 or less, 0.65 or less, 0.60 or less, 0.55 or less, 0.50 or less, 0.45 or less, 0.40 or less, 0.35 or less, 0.30 or less, 0.25 or less, 0.20 or less, and even less).

[0120] To improve the retention of virus particles, the inner surface of the channel is structured so that its surface area increases, and adsorption sites for virus particles are provided. It has been discovered that the ratio of the average cross-sectional area of the openings to the average surface area of the inner surface of the channel can be an important factor in reducing the likelihood of virus breakthrough at the second surface 606, thereby extending the life of the filter member 602. In some embodiments, for example, the average cross-sectional area ratio of the openings of the channel on the first surface 604 to the average surface area of the inner surface of the channel can be 0.05 or less (for example, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less, 0.005 or less, 0.003 or less, 0.001 or less, 0.0005 or less, 0.0001 or less, 0.00001 or less, 0.000001 or less, 0.0000001 or less, and even less).

[0121] In some embodiments, to further increase the surface area of the inner surface of the channel, a part or all of the channel may include lateral protrusions. FIG. 11 is a schematic view of a filter member 602 including a channel 1102 having openings 1104 and 1106 on the first and second surfaces 604 and 606, respectively, and six lateral protrusions 1108. The channel 1102 has a channel axis 1110 that connects the mass centers of the openings 1104 and 1106. The length of the channel axis 1110 is L measured between the respective mass centers of the openings 1104 and 1106.

[0122] The extension or protrusion of the channel 1102, when the extension or protrusion does not reach the second surface 606, and the perpendicular distance w from the axis 1110 to the farthest point of the extension or protrusion away from the axis 1110p When it is 0.05L or more, for the purposes of the present disclosure, it is defined as a "lateral protrusion". The vertical distance w p is shown for each of the lateral protrusions in FIG. 11.

[0123] Generally, for a given lateral protrusion, w p can be 0.05L or more (for example, 0.10L or more, 0.20L or more, 0.30L or more, 0.40L or more, 0.50L or more, 0.75L or more, 1.0L or more, 1.25L or more, 1.5L or more, 2.0L or more, 2.5L or more, 3.0L or more, 3.5L or more, 4.0L or more, 5.0L or more, and even more).

[0124] A given channel 1102 can include any number of lateral protrusions (for example, none, one or more, two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, and even more). The primary protrusions extending from the channel axis 1110 can also include secondary protrusions extending from the primary protrusions such that the individual channels have a branched "tree-like" structure. Among the filter members 602, the average number of lateral protrusions per channel 1102 can be none, or 0.25 or more (for example, 0.50 or more, 1.0 or more, 1.5 or more, 2.0 or more, 2.5 or more, 3.0 or more, 3.5 or more, 4.0 or more, 4.5 or more, 5.0 or more, 5.5 or more, 6.0 or more, 6.5 or more, 7.0 or more, 7.5 or more, 8.0 or more, and even more).

[0125] In some embodiments, the channels of the filter member may include one or more coating materials. The coating materials are used, for example, to enhance the adsorption of virus particles and to facilitate the fluid flow through the member. The coating is also used to adjust the hydrophobicity or hydrophilicity of the member and / or to adjust the ionic properties of the member. Generally, the individual channels of the filter member may or may not include a coating layer, or may include a single coating layer or multiple (e.g., two or more, three or more, four or more, five or more, even more) coating layers. FIG. 12 is a schematic diagram showing a filter member 602 including a channel 1202 with two coating layers 1204 and 1206. Each of the coating layers conforms to the inner surface of the channel in FIG. 12. A variety of different coating materials are used. Examples of such materials include, but are not limited to, cellulose and regenerated cellulose, hydrophilic polymers (e.g., polyethersulfone, polyethylene glycol), hydrophobic polymers (i.e., polyethylene, polypropylene, polyvinylbenzene), polypropylene glycol, other polyols, polyurethane, polymethylmethacrylate, and polyacrylic acid.

[0126] Typically, the coating layer adhered to the walls of the channels of the filter member is relatively thin. For example, in a filter member having a plurality of channels, each channel has a maximum cross-sectional dimension measured in a plane orthogonal to the direction of fluid flow within the filter member, and the filter member has an average maximum cross-sectional dimension among all such channels. In some embodiments, the ratio of the average thickness of the coating material adhered to the inner surface of the channel to the average maximum cross-sectional dimension of the channel is 0.2 or less (e.g., 0.15 or less, 0.10 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less, 0.005 or less, 0.004 or less, 0.003 or less, 0.002 or less, 0.001 or less).

[0127] Multilayer filter In some embodiments, the filter member 602 is multi-layered and is effectively formed from two or more contacting filter members. FIG. 13 is a schematic view showing a filter member 602 formed by three layers 602a-c. Although three layers are shown in FIG. 13, more generally, the filter member 602 is formed of two or more (e.g., three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, ten or more, or more) layers.

[0128] Each of the layers 602a-c can have any of the above-described properties. In other words, any of the thicknesses, layer and channel geometries, and other attributes discussed herein can be present in any one or more of the layers 602a-c. Between any two of the layers 602a-c, one or more of the channels formed in the upstream layer can be in direct fluid communication with one or more of the channels in the downstream layer. This is what is meant by "direct fluid communication" herein.

[0129] The multi-layered filter member can provide advantages in several different operating environments. For example, in some embodiments, the first layer 602a can have a relatively small number of openings per unit area and a relatively smooth surface feel. This configuration allows fluid moving in the cross-flow direction across the surface of the first layer 602a to effectively "sweep" the surface clean, preventing the accumulation of solids on the surface that would otherwise impede effective filtration. In some embodiments, the second layer 602b can be relatively porous and have a relatively large number of channels for capturing virus particles, resulting in a relatively rough feel. In some embodiments, the third layer 602c can have relatively small openings (e.g., openings with a maximum cross-sectional dimension between about 20 nm and 30 nm) in the second surface, whereby the third layer functions effectively as a size exclusion filter for particles in the fluid.

[0130] Geometric shape of the fiber As discussed above, the filter member 602 is typically implemented as a layer that contacts the hollow fibers through which the process fluid flows. Generally, the outer diameter of the combination of the hollow fibers and the filter member 602 is usually selected as needed to ensure appropriate cross-flow and tangential flow through the filter unit. In some embodiments, for example, the outer diameter can be 0.3 mm or more (e.g., 0.4 mm or more, 0.5 mm or more, 0.6 mm or more, 0.7 mm or more, 0.8 mm or more, 0.9 mm or more, 1.0 mm or more, 1.1 mm or more, 1.2 mm or more, 1.3 mm or more, 1.4 mm or more, 1.5 mm or more).

[0131] The inner diameter of the hollow fibers is also selected as needed. In some embodiments, for example, the inner diameter of the hollow fibers is 0.1 mm or more (e.g., 0.2 mm or more, 0.3 mm or more, 0.4 mm or more, 0.5 mm or more, 0.6 mm or more, 0.7 mm or more, 0.8 mm or more, 0.9 mm or more, 1.0 mm or more, and even more). The inner diameter of the hollow fibers can be 0.001 mm or more smaller than the outer diameter of the combination of the hollow fibers and the filter member 602 (e.g., 0.005 mm or more, 0.01 mm or more, 0.012 mm or more, 0.014 mm or more, 0.016 mm or more, 0.018 mm or more, 0.020 mm or more, 0.022 mm or more, 0.024 mm or more, 0.026 mm or more, 0.028 mm or more, 0.030 mm or more, 0.032 mm or more, 0.034 mm or more, 0.036 mm or more, 0.038 mm or more, 0.040 mm or more, 0.042 mm or more, 0.044 mm or more, 0.046 mm or more, 0.048 mm or more, 0.05 mm or more, 0.055 mm or more, 0.060 mm or more, 0.065 mm or more, 0.070 mm or more, 0.075 mm or more, 0.080 mm or more, 0.085 mm or more, 0.090 mm or more, 0.10 mm or more, and even more).

[0132] Layer tangential flow virus filtration In the foregoing discussion, tangential flow virus filtration has been carried out using a hollow fiber-based filter unit. Commercially available virus filters are thus implemented and used in non-circulating filtration assemblies. However, the filter members described herein are also used in a layer tangential flow filtration subsystem to perform tangential flow virus filtration. Such a subsystem has several advantages compared to fiber-based filtration. First, layered filter members are generally easier to fabricate than tubular filter members. Second, layered filter members can be produced with a relatively large surface area and can thus handle a larger flux of process fluid than fiber-based filter members. Third, a layered filter unit can include a turbulence promoter (such as a screen) that creates a turbulent fluid flow across the filter member, thereby assisting the cross-flowing process fluid to "sweep" the surface of the filter member.

[0133] FIG. 14 is a schematic diagram showing an example of a layer tangential flow virus filtration unit 1402. The unit 1402 includes an inlet 1404, an outlet 1406, a filter member 1410, a product stream outlet 1412, and a screen 1414 that functions as a turbulence promoter. During operation, the process fluid enters the inlet 1404 and flows in the direction indicated by the arrow 1408 towards the outlet 1406. When the cross-flowing process fluid interacts with the screen 1414, turbulence is created in the flowing process fluid, which helps to remove solid matter from the surface of the filter member 1410.

[0134] The transmembrane pressure within the unit drives a portion of the process fluid through the filter member 1410, and a product stream that exits the filter member from the product stream outlet 1412 is generated. The product stream is generally free of virus particles, and the virus particles remain trapped within the filter member 1410.

[0135] Generally, the filter member 1410 can have any of the features described above in connection with the filter member 602. That is, any of the thicknesses, layer and channel geometries, and other attributes discussed herein can be present in the filter member 1410.

[0136] Other embodiments The foregoing description is illustrative of the scope of the present disclosure and not restrictive, and it should be understood that embodiments other than those explicitly described are within the scope of the present disclosure.

Claims

1. A virus filter comprising: A filter member including a first outer surface and a second outer surface, the filter member having a thickness extending in a first direction between the first and second outer surfaces; A plurality of channels formed in the filter member, each channel extending through the thickness of the filter member from an opening in the first outer surface that is not shared with other channels to an opening in the second outer surface that is not shared with other channels, each of the channels including a channel axis, and a tangential flow direction being defined along the channel axis from the first outer surface to the second outer surface; Wherein, during use, a solution holding a virus load flows in a direction parallel to the first outer surface, at least a portion of the virus load enters the filter member from the first outer surface and propagates along the tangential flow direction; The virus filter according to claim 1, wherein for at least 50% of the channels in the filter member, the channel axis is oriented at an angle between 5 degrees and 85 degrees with respect to the first direction.

2. The filter according to claim 1, wherein the channel axis is oriented at an angle between 5 degrees and 75 degrees with respect to the first direction.

3. The filter according to claim 1, wherein the channel axis is oriented at an angle between 10 degrees and 60 degrees with respect to the first direction.

4. The filter according to claim 1, wherein for at least 70% of the channels in the filter member, the channel axis is oriented at an angle between 5 degrees and 85 degrees with respect to the first direction.

5. The filter according to claim 1, wherein for at least 90% of the channels in the filter member, the channel axis is oriented at an angle between 5 degrees and 85 degrees with respect to the first direction.

6. The filter according to claim 1, wherein the thickness of the filter member is 150 micrometers or more.

7. The filter according to claim 1, wherein the thickness of the filter member is 300 micrometers or more.

8. The filter according to claim 1, wherein the thickness of the filter member is 500 micrometers or more.

9. The filter according to claim 1, wherein each channel of the plurality of channels includes an opening in the first outer surface, and the ratio of the total area of the openings to the total area of the first outer surface is 0.10 or more.

10. The filter according to claim 9, wherein the ratio of the total area of the openings to the total area of the first outer surface is 0.20 or more.

11. The filter according to claim 9, wherein the ratio of the total area of the openings to the total area of the first outer surface is 0.30 or more.

12. For each channel of the plurality of channels, the channel has a certain volume, and the ratio of the total volume of the channels to the total volume of the member is 0.05 or more. The filter according to claim 1.

13. The ratio of the total volume of the channels to the total volume of the member is 0.10 or more. The filter according to claim 12.

14. The ratio of the total volume of the channels to the total volume of the member is 0.20 or more. The filter according to claim 12.

15. For each of at least some of the plurality of channels, the channel includes an opening having a first cross-sectional area on a first outer surface, and the first cross-sectional area is smaller than a second cross-sectional area at one position between the first and second outer surfaces of the channel. The filter according to claim 1.

16. The ratio of the first cross-sectional area to the second cross-sectional area is 0.95 or less. The filter according to claim 15.

17. The ratio of the first cross-sectional area to the second cross-sectional area is 0.85 or less. The filter according to claim 15.

18. The ratio of the first cross-sectional area to the second cross-sectional area is 0.75 or less. The filter according to claim 15.

19. At least some of the channels include at least 40% of the plurality of channels. The filter according to claim 15.

20. At least some of the channels include at least 60% of the plurality of channels. The filter according to claim 15.

21. At least some of the channels include all of the plurality of channels. The filter according to claim 15.

22. The channel axes of the plurality of channels include a distribution of orientations with respect to a first direction. The filter according to claim 1.

23. The distribution of the average orientation is between 10 degrees and 30 degrees with respect to the first direction. The filter according to claim 22.

24. The distribution of the average orientation is between 30 degrees and 50 degrees with respect to the first direction. The filter according to claim 22.

25. The distribution of the average orientation is between 50 degrees and 80 degrees with respect to the first direction. The filter according to claim 22.

26. The full width at half maximum (FWHM) value of the distribution of the orientation is 60 degrees or less. The filter according to claim 22.

27. The FWHM value of the distribution is 40 degrees or less. The filter according to claim 26.

28. The FWHM value of the distribution is 15 degrees or less. The filter according to claim 26.

29. For each of at least some of the plurality of channels, the channel includes one or more secondary channels extending from the channel axis, the filter according to claim 1.

30. The one or more secondary channels extend along a secondary axis from the channel axis at an angle between 10 degrees and 80 degrees with respect to the channel axis, the filter according to claim 29.

31. The one or more secondary channels extend along a secondary axis from the channel axis at an angle between 50 degrees and 90 degrees with respect to the channel axis, the filter according to claim 29.

32. One or more of at least some of the channels include three or more secondary channels, the filter according to claim 29.

33. One or more of at least some of the channels include five or more secondary channels, the filter according to claim 29.

34. At least some of the channels include an average of five or more secondary channels, the filter according to claim 29.

35. At least some of the channels include an average of seven or more secondary channels, the filter according to claim 34.

36. For each of at least some of the plurality of channels, the channel includes an opening having a first cross-sectional area on a first outer surface and a maximum cross-sectional area different from the first cross-sectional area at a position between the first and second outer surfaces on the first outer surface, the filter according to claim 1.

37. The ratio of the first cross-sectional area to the maximum cross-sectional area is 0.50 or less, the filter according to claim 36.

38. The ratio of the first cross-sectional area to the maximum cross-sectional area is 0.30 or less, the filter according to claim 37.

39. The ratio of the first cross-sectional area to the maximum cross-sectional area is 0.10 or less, the fil ter.

40. At least some of the plurality of channels include 50% or more of the plurality of channels, the filter according to claim 36.

41. At least some of the plurality of channels include 80% or more of the plurality of channels, the filter according to claim 40.

42. For each of at least some of the plurality of channels, the channel includes a maximum cross-sectional area and a minimum cross-sectional area at different positions along the channel axis, and the ratio of the minimum cross-sectional area to the maximum cross-sectional area is 0.75 or less. The filter according to claim 1.

43. The filter according to claim 42, wherein the ratio of the minimum cross-sectional area to the maximum cross-sectional area is 0.50 or less.

44. The filter according to claim 42, wherein the ratio of the minimum cross-sectional area to the maximum cross-sectional area is 0.30 or less.

45. The first outer surface is a plane, has a maximum dimension measured in the plane, and the ratio of the maximum dimension to the thickness is 10 or more. The filter according to claim 1.

46. The filter according to claim 45, wherein the ratio of the maximum dimension to the thickness is 20 or more.

47. The porosity of the member is between 0.3 and 0.

9. The filter according to claim 1.

48. The filter member is formed from a first material, and each of at least some of the plurality of channels includes a second material located on the inner surface of the channel. The filter according to claim 1.

49. The first material is selected from the group consisting of polyvinylidene fluoride (PVDF), hydrophilic PVDF, and regenerated cellulose. The filter according to claim 48.

50. The second material is selected from the group consisting of cellulose, polyethersulfone, and polyethylene glycol. The filter according to claim 48.

51. For the filter according to claim 48, the ratio of the average thickness of the second material on the inner surface of each of at least some of the channels to the maximum cross-sectional dimension of the channel is 0.2 or less.

52. For the filter according to claim 51, the ratio of the average thickness of the second material on the inner surface of each of at least some of the channels to the maximum cross-sectional dimension of the channel is 0.1 or less.

53. For the filter according to claim 48, the ratio of the average thickness of the second material on the inner surface of each of at least some of the channels to the thickness of the filter member is 0.05 or less.

54. For the filter according to claim 53, the ratio of the average thickness of the second material on the inner surface of each of at least some of the channels to the thickness of the filter member is 0.02 or less.

55. The plurality of channels are a first plurality of channels, and the filter member is: A first layer including the first plurality of channels; The filter according to claim 1, comprising a second layer including a second plurality of channels.

56. The filter according to claim 55, wherein the second layer is in contact with the first layer.

57. The filter according to claim 55, wherein at least some of the first plurality of channels are in fluid communication with at least some of the second plurality of channels at the interface between the first and second layers.

58. The filter according to claim 55, wherein each of the channels of the second plurality of channels includes a channel axis, and for at least 50% of the second plurality of channels of the second layer, the channel axis is oriented at an angle between 5 degrees and 90 degrees with respect to the first direction.

59. The filter according to claim 58, wherein the average orientation of the first plurality of channels with respect to the first direction is different from the average orientation of the second plurality of channels with respect to the first direction.

60. The filter according to claim 59, wherein the average angle between the channel axis and the first direction for the second plurality of channels is greater than the average angle between the channel axis and the first direction for the first plurality of channels.

61. The filter according to claim 59, wherein the average angle between the channel axis and the first direction for the second plurality of channels is smaller than the average angle between the channel axis and the first direction for the first plurality of channels.

62. The first layer is formed of a first material selected from the group consisting of polyvinylidene fluoride (PVDF), hydrophilized PVDF, and regenerated cellulose, and the second layer is formed of a second material selected from the group consisting of cellulose and regenerated cellulose, polyethersulfone, polyethylene glycol, polyethylene, polypropylene, polyvinylbenzene, polypropylene glycol, polyurethane, polymethylmethacrylate, and polyacrylic acid. The filter according to claim 55.

63. The filter according to claim 62, wherein the first material and the second material are different.

64. The filter according to claim 55, wherein at least some of the first plurality of channels include a coating material on the inner surface of the at least some channels.

65. The filter according to claim 64, wherein the coating material is selected from the group consisting of cellulose, polyethersulfone, and polyethylene glycol.

66. The filter according to claim 55, wherein at least some of the second plurality of channels include a coating material on the inner surface of the at least some of the channels.

67. The filter according to claim 64, wherein the coating material is selected from the group consisting of cellulose, polyethersulfone, and polyethylene glycol.

68. The filter according to claim 55, wherein at least some of the first plurality of channels include a first coating material on the inner surface of the at least some of the first plurality of channels, and at least some of the second plurality of channels include a second coating material on the inner surface of the at least some of the second plurality of channels.

69. Each channel of the first plurality of channels includes an opening on a first outer surface, and each channel of the second plurality of channels includes an opening at an interface between the first and second layers. The average cross-sectional area of the openings of the first plurality of channels is different from the average cross-sectional area of the openings of the second plurality of channels. The filter according to claim 55. The filter according to claim 55, wherein the average cross-sectional area of the openings of the first plurality of channels is larger than the average cross-sectional area of the openings of the second plurality of channels.

70. The filter according to claim 69, wherein the average cross-sectional area of the openings of the first plurality of channels is larger than the average cross-sectional area of the openings of the second plurality of channels.

71. The filter according to claim 69, wherein the ratio of the total area of the openings of the first plurality of channels on the first outer surface to the area of the first outer surface is larger than the ratio of the total area of the openings of the second plurality of channels on the interface surface to the area of the interface surface.

72. Each channel of the first plurality of channels has a certain volume in the first layer, and each channel of the second plurality of channels has a certain volume in the second layer. The ratio of the total volume of the first plurality of channels in the first layer to the volume of the first layer is larger than the ratio of the total volume of the second plurality of channels in the second layer to the volume of the second layer. The filter according to claim 55.

73. For each of at least some of the second plurality of channels, the channel has an opening having a first cross-sectional area at the interface between the first and second layers and a second cross-sectional area at a position displaced from the interface along the channel axis, and the first cross-sectional area is smaller than the second cross-sectional area. The filter according to claim 55.

74. The filter according to claim 73, wherein the ratio of the first cross-sectional area to the second cross-sectional area is 0.85 or less.

75. The filter according to claim 74, wherein the ratio of the first cross-sectional area to the second cross-sectional area is 0.50 or less. **Claim 76** The filter according to claim 55, wherein each channel of the second plurality of channels is oriented with respect to a first direction defined by a channel axis of the channel, and a full width at half maximum (FWHM) of a distribution of orientations of the second plurality of channels is 20 degrees or less. **Claim 77** The filter according to claim 76, wherein the FWHM of the distribution of orientations of the second plurality of channels is 10 degrees or less.

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