Commercial Viral Filters: Viresolve®

See also Purification of plasma proteins, particularly virus inactivation. 

Operating Conditions

Addition of Amino Acids:

Hongo (US 13/260419) discloses a method of removing viruses from monoclonal antiboides uisng a virus removing membrane by adding a basic amino acid such as arginine, histidine, lysine or a derivative thereof. 

Lengsfeld (US 2003/0232969) disclsoes a method for separating viruses from a proteins such as fibrinogen and factor VIII by nanofiltration by adding to the protein solution chatropic substances choses from arginine, guanidine, citrulline, urea and derviatives and salts thereof or order to decrease or prevent aggregation of the protein molecules and then filtering the solution through a filter having a pore size ranging from 15-35 nm. The addition of the chatropic substances is disclosed as overcoming the protein of using nanofilters having a pore size of 15-35 nm which is regarded as too small to free larger proteins such as fibrinogen, von Willebrand factor and Factor VIII from viruses. 

Yamaguchi (US8741600) discloses a method of separating an immunoglobulin monomer comprising filtering an immunoglobulin solution containing the monomer and an aggregate having an immunoglobuiolin concentration of 1 to 150 g/L with cross-flow filtration using an UF membrane have a MWCO of 100k or more and less than 500k and further comprising a surfactant selected from the group of lysine, alanine, cysteine, glycine, serine, proline, arginine and derviatives thereof. 

Yang (WO2004/001007) discloses a method for producing a concentrated antibody preparation that includes adding a histidine or acetate buffer at a concentraiton in the range of from about 2-48 mM and then subjecting the antibody preparation to membrane filtration, which improves filtraiton flow rate. 

Addition of surfactant:

Surfactants are a class of industrially important amphiphilic substances (possess both hydrophilic and hydrophobic parts at the same time (i.e., water attracting and water repelling parts, respectively). One of the characteristic properties of amphiphilic substances is that they tend to assemble at interfaces. They are thus often referred to as surface active agents. A surfactant molecule consists normally of an alkyl chain and a hydrophilic head group. Surfactns are categoried into 4 groups depending on the charge of the head-group: nonionic (0), anionic (-), cationic (+) and zwitterionic (+). Ann-Sofi Jonsson (J. Membrane Science, 56 (1991) 49-76)

Ultrafiltration is a very efficient process for the separation of macromolecules such as proteins. A common problem in the application of UF membranes in separations is the decline of permeate flux. Fouling phenomena frequenly are observed due to solute accumulation at the membrane solution interfact and solute adsorption onto membrane pores. The use of surfactants such as nionic, anionic and their combinations has been proved very successful for membrane pretreatment. For example, fouling is reduced in UF of BSA using membranes pretreated with anionic and mixed anionic-nonionic surfactant solutions. Xiarchos “Polymeric ultrafiltration membranes and surfactants” Separation & amp; Purification Reviews, 2003. 

Ann-Sofi Jonsson (J. Membrane Science, 56 (1991) 49-76) discloses the influence of a nonionic (Tri-Ton X-100), two anionic (potassium oleate and sodium dodecylbenzensulphonate) and a cationic (hexadecyltrimethylammonium bromide) surfactant on untrafiltraiton membranes with respect to commercial membranes of polysulphone, poly(vinylidene fluoride) and cellulose acetate. The flu reductions of the hydrophobic membranes were found to be much more pronounced that the flux variations of the hydrophilic membranes. Both the material and the MWCO were found to influence the performance of the hydrophobic membranes. 

Brown, (US 14/007,610, published as US 2014/0309403) discloses a method of reducing fouling of an UF in the purification of a protein from virus particles by adding a non-ionic sufactant such as polysorbate 20, Triton X-100, Triton X-405, lauromacrogol and polysorbate or a surfantant such as polysorbate or a non-ionic agent such as polyethylene glycol, a cellulose derivative, arginine and a dextran.

Chugai (WO2002/013859 (in Chinese) discloses a method of inhibiting an antibody containing solution during UF from coagulating or becoming turbid by ading to the antibody containing solution a surfactant such as polysorbate 20/80. 

Rosenblatt US6,773,600 see also US 2003/0230532) discloses using a non-ionic surfacant during viral reduction using size exclusion nanofiltration for purificaiton of large proteinaceous biomolecules such as antibodies which allows efficient flowthorugh, minimal yield loss and no significant change in the immunoglobulin characterization aggregate level or stability.

Van Holten (US6,096,872) discloses purificaiton of immunoglobulins such as anti-D immunoglobulin substantially free of vrius using nanofiltration in a high ionic strenght buffer with an excipient such as nonionic detergents with polyoxyethlene or sugar head groups, lysopholipids and bile salts. Most preferred are nonionic polyoxyethlene detgernts such as polysorbates, PLURONICS, polyoxyethylene-polypropylene polymers or co-polymers, Brij, Sterox-AJ, Tritons and Tweens. Most preferred is polysorbate 80. 

Low concentration of acetate or histidine buffer (of from about 2 MM to about 48 mM) shown to stabilize antibody preparation during concentration by membrane filtration, lowering the viscosity of the antibody solution and suppressing aggregation (WO 2004/001007). 

 Ph and Conductivity

Takeda (US2006/0142549A1) discloses a method for removing impurities from a protein such as an antibody by forming the protein-containing sample into an aqueous solution of low conducitvity and a pH equal to or lower than the isoelectric poit of the protein and then removing the impurities by filtration. In some embodiments the low conductivity has an ionic strenght of 0 to 0.2 mM and a pH equal or greater than 2.0. 

Transmembrane pressure (TMP) or UF Pressure 

The term “transmembrane pressure (TMP)) denotes the pressure which drives the fluid to filtrate accross an ultrafiltration membrane. The value of TMP can be calculated as: TMP=Pfee + Pretentate)/2-permeate where the “feed pressure” denotes the pressue applied to the inlet of an UF, “retentate pressure” denotes the pressure applied to teh outlet of an UF and “permeate pressure” denotes the pressure applied to the permeate side of the UF. TMP is an average of the feed pressure and the retentate pressure in the case where the permeate side is open in the TFF equipment. The value of pressure is sually given in terms of “bar” or “MPa” or “psi”. Lau (US14/241567). 

In TFF, the driving force (transmembrane pressure or TMP) is the difference between the average of the membrane feed pressure (P1) and the retentate pressure (P2) minus the permeate pressure (P3).  TMP=(P1 + P2)/2 – P3. Schick (WO02/00331)

–Typical TMPs:

Antoniou discloses a process for removing protein aggregates using TFF at TMP of about 1 and about 10 psi, preferably between about 1 and about 4 psi (US 6,365,395 B1).

Couto (WO 2004/076695A1) discloses a method for separating molecules of interest such as antibodies using TFF. In a preferred embodiment, fat, casein miscelles and bacteria are removed from a transgenic milk feedstream. Couto further teaches that two important variable involved in TFF are TMP and CF.

Cui discloses using TFF with 0.3 bar (“removal of protein aggregates by ultrafiltration, Z.F. Cui).

–Devices for monitoring optimal TMP

Schick (WO02/00331) discloses a dvice that can be used to maintin a substantially constant TMP by varying filter inlet pressure in accordance with varying level of resistance to flow (increase in fluid viscosity). This is done using pressure sensors which read inlet pressure )P1 membrane feed pressure) , retentate outlet pressure (P2 retentate pressure) and filtrate pressure (P3 permeate pressure). Given that the TMP=(P1+P2)/2-P3, appropriate adjustments can be made using valves which are associated with each pressure sensor. For example, modifications can be made to modify pump speed and/or to modify the size of the vale openings so as to modify the TMP. P1 (inlet pressure) is a variable that is preimarily dependnt on the pump rate, viscosity of the lquid being pumped and the physical dimensions of the device. 

Schilog (WO 02/00331) discloses a filtration device which contain maintain a substantially constant trans-membrane pressure which includes pressure sensors to read the pressure at the inelt, retentate outlet and filtrate outlet. 

Temperature: 

–Variable TMPs and CFF:

—-Variable depending on Protein Concentration or Feed Pressure:

Bolton (WO2010/111378) discloses a method of generating a highly concentrated protein solution using an initial feed pressure at least about 5 psig and the maximum feed pressure limit of the device and recirculating the first protein solution thorugh the UF device. When oeprating at a fixed feed flow rate, the viscosity and feed pressure will increase as the proten concenrates. When the feed pressure reaches the limit of the device, the feed flow rate can be decreased to maintain the feed pressure near the maxium value. (#68). 

Hepbildikler discloses a method for removing immunoglobulin aggregates using TFF at constant delta p of 3.0 bar and constant TMP of 0.6 bar (US 12/744089). Hepbildikler also teaches a method for concentrating an immunoglobulin solution by TFF in that the transmembrane pressure and the cross-flow are variable and changed during the filtration process accoding to the concentration of the immunoglobulin. In some embodiments the transmembrane pressure and cross-flow are 1.5 bar and 80 m./min, 0.85 bar and 150 ml/min and 0.85 bar and 130 ml/min (US Patent application 12/668,661).

Hepbildikler also discloses a method for the concentration of solutions containing recombinantly produced immunoglobulins where the TMP and cross-flow vary based on the concentration of the antibody (WO 2009/010269A1).

Lau (US14/241567, published as US Patent 9630988; see also 15/461,874, published as US 2017/0204435) discloses a method where a feed flow rate is maintained at a high flow rate until an optimal protein concentration and is then reduced to a lower value to continue further concentration. For example, concentration is performed at a feed flow rate equal or greater than 200 LMH until the retentate solution is concentration to a protein concentration greater than 200 g/L, where a feed pressure builds up to 85-100% of the specified maximum feed pressure of an UF, then further concentration is continued at a feed flow rate equal or less than 120 LMH. 

(Rosenberg, J. Membrane Science 342 (2009) 50-59) discloses an optimized UF concentration method for the production of highly concentrated mAb solutions up to 140 mg/ml by varying TMP and cross-flow conditions systematically depending on the concentration in the retentate.

Schick (EP1623752) discloses a method and system for spearation of pharmaceutical liquies which involves automatically increasing pump rate over time until a maximum selected parameter such as pressure is achieved at which time the system automatically switches to for example a constant pressure filtration mode. For example, a constant pump rate of 15 ml/min was implemented until a backpressure of 20 psi was reached at which point the processor controlled pump unit switched automatically to a constant pressure delivery by modulating the pump ouput in order ot maintain the 20 psi pressure level. 

Winter (US2006/0051347, see also WO2006/031560A2) discloses a process for concentrating proteins including an ultrafiltering, diafiltering and second ultrafiltering sequence at elevated temperature such as above about 30C.