阅读说明：本技术 用于培养哺乳动物细胞的工艺 (Process for culturing mammalian cells ) 是由 K·格雷普迈尔 T·林克 邵志新 于 2018-11-29 设计创作，主要内容包括：提供了用于培养哺乳动物细胞和用于生产由哺乳动物细胞表达的重组产物的工艺,其牵涉pH上移。该工艺特别适合于产业规模细胞培养和生成治疗性产品的细胞的培养。该工艺包含于第一pH进行的第一培养阶段和于比第一pH要高的第二pH进行的第二培养阶段。(Processes for culturing mammalian cells and for producing recombinant products expressed by mammalian cells involving pH upshifting are provided. The process is particularly suitable for industrial scale cell culture and for the culture of cells producing therapeutic products. The process comprises a first culturing phase carried out at a first pH and a second culturing phase carried out at a second pH higher than the first pH.)

1. A fed-batch process for culturing mammalian cells comprising controlling pH using a pH set point, the process comprising

A first culture stage comprising inoculating mammalian cells into a culture medium at a first pH and culturing the cells at the first pH, wherein the pH set point is maintained at the first pH in the first culture stage; and

a second culture phase comprising culturing the cells at a second pH higher than the first pH, wherein the set point is maintained at the second pH during the second culture phase;

and wherein the second pH is at least 0.1 pH units higher than the first pH, and wherein the second incubation period has a duration of at least 6 hours.

2. The method according to claim 1, wherein the second culturing period has a duration of at least 3 days.

3. A method according to claim 1 or claim 2, wherein the temperature of the method is maintained within ± 0.5 ℃.

4. The method according to any one of the preceding claims, wherein the first pH is a value in the range of 6.5-7.5 and:

a. the second pH is 0.1 to 0.5 pH units higher than the first pH; or

b. The second pH is 0.2 pH units higher than the first pH.

5. A method according to any preceding claim, wherein

a. The first pH is about 7.0; and is

b. The second pH is about (i) pH 7.1; (ii) pH 7.2; (iii) pH 7.3; (iv) pH 7.4; (v) pH 7.5; or (vi)7.1 to 7.5.

6. The method according to any one of the preceding claims, wherein the set point is either (a) gradually or (b) instantaneously increased from the first pH to the second pH.

7. The method according to any one of the preceding claims, wherein the set point is gradually increased from the first pH to the second pH, and wherein either (a) the set point is continuously increased or (b) the set point is increased in a series of discrete steps.

8. The method according to any one of the preceding claims, wherein the pH is gradually increased from the first pH to the second pH over a period of about 24-72 hours.

9. The method according to any one of the preceding claims, comprising adding a pH-shifting feed medium to the culture medium.

10. The method according to any one of the preceding claims, wherein the set point has a dead zone of ± 0.05 pH units.

11. The method according to any one of the preceding claims, wherein the mammalian cells are CHO cells.

12. The method according to any one of the preceding claims, which is a method for producing a product, wherein the product is expressed by a mammalian cell, wherein optionally the mammalian cell is a recombinant cell, and wherein the product is a recombinant protein.

13. The method according to claim 12, wherein the product is (a) an antibody; (b) vannouxizumab (vanucizumab); or (c) emmetruzumab (emactuzumab).

14. A process according to any one of claims 12 to 13, comprising the step of isolating the product, and optionally preparing a composition comprising the product.

15. A product or composition produced by the method of claim 14.

Use of a pH-up feeding medium or a pH-raising agent in a method for culturing mammalian cells as set forth in any one of the preceding claims

a. Increasing the titer of a product in a mammalian cell culture, wherein the product is expressed in mammalian cells;

b. increasing cell viability in mammalian cell culture;

c. extending the life of mammalian cell cultures;

d. reducing lactate accumulation in mammalian cell culture;

e. reducing ammonium accumulation in mammalian cell culture;

f. improvement of pCO in mammalian cell culture₂An overview;

g. use of reducing osmolality in a mammalian cell culture, wherein a pH-up feed medium or a pH-raising agent is added to the mammalian cell culture to raise the pH from a first pH to a second pH.

Technical Field

The present invention relates to mammalian cell culture. In particular, the invention relates to mammalian cell culture processes for the production of products, such as therapeutic products.

Background

Recombinantly expressed biotherapeutics (including monoclonal antibodies, antigens and other specialized protein modalities) are increasingly being used to treat diseases in areas such as tumors, immune suppression, autoimmune diseases, and inflammatory disorders (L eaderet et al, 2008; Aggarwal,2011) since many of these therapeutics or "biotherapeutics" have recently been approved for the treatment of cancer and autoimmune diseases at high doses, there is a need to produce these biotherapeutics on an industrial scale to meet increasing clinical needs.

Recombinant mammalian cells, particularly Chinese Hamster Ovary (CHO) cells, are widely used in the pharmaceutical and biotechnology industries for the manufacture of recombinant therapeutic agents. Advances have been made in improving mammalian cell culture processes to achieve higher volumetric product yields and optimal product quality (Omasa et al, 2010; Kim et al, 2012; Zhu, 2012). However, the industrial scale production of therapeutic agents in mammalian cells remains challenging.

Many recombinant therapeutic production processes use fed-batch cultures that produce high cell densities and high final product concentrations under typical fed-batch culture conditions, cells consume excess glucose and amino acids to produce biomass and products, which often results in the production of large amounts of inhibitory metabolites (such as lactate and ammonium) and accumulation in the culture medium the presence of high concentrations of these inhibitory metabolites in the culture medium adversely affects cell growth and can result in low cell concentrations and low product titers (Zhou et al, 1995; Ozturk et al, 1992; L ao and Toth, 1997).

The accumulated lactate can acidify the cell culture and affect cell growth, cell productivity and final product quality. Even under controlled pH conditions, the accumulated lactate may be toxic to mammalian cells at sufficiently high concentrations and may inhibit cell growth and protein production during the middle and late stages of the cell culture process. This is particularly true when the cell density is high.

Effective control of cell growth and metabolic activity is important in order to improve the overall productivity of mammalian cell cultures. Great efforts have been made to control the cellular glycolysis process/tricarboxylic acid (TCA) cycle and to reduce lactate accumulation in cultured cells. To this end, various strategies have been adopted, as follows:

1. glucose is used in limited amounts, or is maintained at low levels during the cell culture process to improve glycolysis/TCA cycle efficiency and protein production (Xie and Wang, 1993; Altamirano et al, 2001; Zhang et al, 2004; Maranga and Goochee, 2006). However, Yeo et al (2006) report that low glucose levels can easily lead to glucose depletion, apoptosis, and premature cell death.

2. Alternative sugars, such as fructose, galactose, and/or other glucose analogs, are used in an attempt to reduce excess lactate accumulation (Altamirano et al, 2000; Altamirano et al, 2004; Altamirano et al, 2006; Walschin and Hu, 2007). However, this strategy may also result in lower cell growth rates or reduced cell productivity.

3. A metabolic engineering approach to modulate glycolytic activity. Paredes et al (1999) describe the genetic modification of hybridoma cell lines to reduce the amount of ammonia and lactate produced by the cells. However, one major drawback of this approach is that the transformed cells are unstable.

4. Cellular lactate dehydrogenase activity is regulated by knocking down lactate dehydrogenase (L DH) expression via homologous recombination or siRNA techniques or by using L DH competitive inhibitors such as oxamic acid (Chen et al, 2001; Kim and L ee,2007 a; Zhou et al, 2011).

5. Overexpression of pyruvate decarboxylase or use of Pyruvate Dehydrogenase (PDH) activators to improve flux into the TCA cycle (Irani et al, 1999; Fogolin et al, 2004; Kim and L ee,2007b) these approaches are often time consuming and can lead to unstable cell lines in CHO cell cultures.

6. Divalent transition metal salts (e.g., copper, zinc) are added to reduce lactate accumulation. Copper can be used in Chinese Hamster Ovary (CHO) cells to shift from net lactate production to net lactate consumption and achieve higher cell growth and productivity (Yuk et al, 2014). US20140051124 describes such methods of reducing lactate production in cell culture using divalent transition metal salts.

7. US8470552 describes a method for culturing animal cells in the presence of sufficient concentrations of exogenous lactate to reduce lactate production.

8. The culture conditions, such as temperature and pH, are controlled. Culture pH is one of the key physiological parameters known to have a significant effect on mammalian cell growth and target protein production (Borys et al, 1993; Yoon et al, 2005). Oguchi et al (2006) describe the effect of reduced pH conditions on cell life span and also report that pH has no effect on mRNA stability-a combination of lower pH and lower temperature is required to induce cell life span and improve mRNA stability. Trummer et al (2006) reported a controlled slowing of cell metabolism at reduced temperatures and reported that reduced pH values could significantly improve volumetric productivity in CHO batch cell cultures without affecting the quality of the secreted product.

US8765413 describes a similar approach, in which a pH shift down and a temperature shift down are combined to slow down cell metabolism, thereby reducing lactate formation and improving volumetric productivity in CHO cell culture. US8765413 reports that CHO cells generally produce less lactate at lower pH (e.g., pH 6.8) than at higher values (e.g., pH 7.0), and also suggests that shifting the incubation pH to lower values reduces the concentration of extracellular ammonia.

WO 2008/033517 describes methods and compositions for producing recombinant proteins, particularly anti-TNF α or anti-interleukin-12 antibodies, including the use of a linear pH ramp, starting at a pH of about 7.1 to 7.2 and decreasing to a final pH. of about 6.9 over 24,48, or 72 hours this method reportedly results in increased cell growth and productivity.

In an investigation of the effects of temperature and pH on THIOMAB 3L C formation, Gomez et al (2010) reported that high temperature and high pH conditions increased lactate accumulation, which was associated with low cell viability.

In summary, previous studies have shown that pH downshifting in combination with temperature downshifting positively affects cell viability, cell productivity, and/or final product quality in mammalian cell cultures.

In addition to lactate, it is also known that the accumulation of high levels of ammonia negatively affects cell growth, product titer, and post-translational modification of the product in mammalian cell culture (Hassell et al, 1991; Ozturk et al, 1992).

Reaction of dissolved ammonia in cell culture media in pH-dependent media Is converted to ammonium. The terms "ammonia" and "ammonium" are generally used interchangeably in discussing their role as inhibitory metabolites in cell culture processes.

Ammonia accumulation to more than 14mM has been shown to be detrimental to culture growth (Hayter et al, 1991; L aoand Toth,1997), and high ammonium concentrations have also been shown to adversely affect the glycosylation pattern of recombinant proteins, reducing both galactosylation and sialylation (Andersen and Goochee, 1995; Borys et al, 1994; Gawlitzek et al, 2000).

Yang and Butler (2000) reported that cell density decreased by 10% at 5mM ammonia, and that the glycosylation pattern changed in CHO cell culture at 10mM ammonia.

Nevertheless, few published studies have attempted to address the problem of ammonia accumulation in fed-batch processes.

Elevated levels of dissolved carbon dioxide are also known to affect cell growth and protein production in mammalian cell cultures. For fed-batch processes in bioreactors, pCO₂Levels can rise significantly above normal physiological values. Such high levels of dissolved CO₂Can reduce cell growth and metabolism, decrease productivity, and ultimately cause adverse effects on glycosylation (Mostafa and Gu, 2003; Kimura a)nd Miller,1997；deZengotita et al.,2002；Schmelzerand Miller,2002；Zhu et al.,2005)。

High pCO in fed-batch process₂Concentrations normally derived from cellular metabolism and use of NaHCO₃/Na₂CO₃Both as a buffer in the culture medium. In addition, often additional NaHCO is added₃As a base to neutralize lactate produced by the cells.

Reduce high pCO₂The horizontal approach is to use a bicarbonate-reduced or bicarbonate-free buffer. Goudar et al (2007) used bicarbonate-free buffers in perfusion processes and achieved pCO₂A 70% reduction in the level and a subsequent positive effect on cell growth and specific productivity. Nevertheless, elevated pCO₂The negative effects of (a) are still significant.

Another removal of CO from cell cultures₂Is gas stripping, however, in view of CO₂Relatively high solubility and low henry's law constants, which generally have limited impact in bioreactors. Under normal cell culture operating conditions, sufficient gas dispersion and aeration is required to remove high levels of CO₂. However, as bubble residence time increases with scale, for CO₂The average driving force removed decreases rapidly. Thus, a much higher gas flow rate is sufficient CO₂Necessary for the stripping to be effective. However, the aeration rate is limited in view of the detrimental effect on the cells (Michaels et al, 1995a, b).

Scaling up and transferring between different manufacturing facilities during the cell culture process is also desirable to match pCO₂Level and profile. One key issue here is how to achieve the same or similar pCO across different scales₂Overview. Normally, due to the hydrostatic pressure of the fermenter, mixing, and CO₂Differences in stripping characteristics, larger scale showing higher pCO₂Level (L i et al, 2006; Mostafa and Gu, 2003.) it is possible to have a high pCO₂Horizontal processes can be more challenging at scale-up, as the pCO is further scaled up₂The process is pushed to damaging conditions. Thus, there is also a clear need forImprovement of pCO between scales₂Comparability of profiles to increase the pair pCO₂And to benefit future scale-down models.

Solving pCO in mammalian cell bioreactor₂Few studies of control have focused primarily on reducing CO₂Addition and removal of CO₂. Alternative more efficient approaches are needed.

Osmolality has been found to be detrimental to mammalian cell culture when elevated to high levels (Kim and L ee, 2002; deZengotita et al, 2002; Cherlet and Marc, 1999).

High pCO due to bioreactor pH control at a predefined set point during fed-batch culture₂Resulting in a concomitant increase in the osmolality of the medium due to the increase in HCO added as a base to control pH₃Concentration results (Zanghi et al, 1999; Schmelzer et al, 2000). When osmolality and pCO₂At all high, cell death rates are significantly increased (deZengotita et al, 1998), and can result in a significant reduction in overall productivity.

In view of the above, there is a continuing need for efficient cell culture processes to overcome these deficiencies. The present invention seeks to address this need.

Summary of The Invention

The present invention relates to a process for culturing cells, in particular mammalian cells. In particular, the invention relates to a process for culturing mammalian cells, wherein the process comprises a pH up shift.

In a first aspect, the invention provides a fed-batch process for culturing mammalian cells, the process comprising a first culture phase comprising inoculating mammalian cells into a culture medium at a first pH and culturing the cells at the first pH, and a second culture phase comprising culturing the cells at a second pH higher than the first pH.

The processes disclosed herein advantageously avoid the accumulation of unwanted metabolites. Such unwanted metabolites include lactate, ammonium and CO₂. The process of the invention canResulting in higher cell viability, higher cell concentration and/or higher product titer.

The process comprises a first incubation period at a first pH and a second incubation period at a second pH, wherein the second pH is higher than the first pH. The second pH may be at least 0.10pH units higher than the first pH. The second pH may be about 0.1 to 0.5,0.1 to 0.4, or 0.1 to 0.3 pH units higher than the first pH. The second pH may be about 0.2 pH units higher than the first pH. The first pH may be about 7.0. The first pH may be about 7.0 and the second pH may be about 7.2.

The first pH may be a range having a first lower limit and a first upper limit. The second pH may be a range having a second lower limit and a second upper limit, where the second lower limit is equal to or higher than the first upper limit, or where the second lower limit is higher than the first upper limit.

The process may include controlling the pH using a set point. In this context, the set point may vary. As such, the process may include controlling the pH using a pH set point. The process may further comprise controlling the pH using a dead zone, which may be ± 0.05 pH units with respect to the pH set point.

The process of the present invention involves a pH shift up. The process comprises a first incubation period at a first pH and a second incubation period at a second pH, wherein the second pH is higher than the first pH. The first culture stage can comprise inoculating the mammalian cells into a culture medium at a first pH. The pH up-shift stage is between the first culture stage and the second culture stage. The pH up shift is an increase in pH from a first pH to a second pH. This may be a gradual increase, it may be a continuous increase, or it may comprise discrete steps or increments. The process may be one that does not involve a pH shift down.

The process may be a fed-batch process. A fed-batch process is one in which one or more nutrients are added to the culture vessel during the course of the cultivation. The cells are maintained in the culture vessel throughout the cell culture process. The cells and/or products of the cells are harvested at the end of the process.

The process may comprise inoculating the mammalian cells into a culture medium. The first culturing stage of the process at the first pH may comprise seeding the cells into a culture medium at the first pH. Inoculating a cell into a culture medium refers to adding one or more cells (which may be a population of cells) into a sterile culture medium. Inoculation may also be referred to as seeding. The mammalian cell may be a CHO cell.

The temperature of the process may be maintained at a substantially constant value. The process in which the temperature is maintained at a substantially constant value does not comprise a significant temperature shift between the first and second culture stages. The substantially constant temperature value may be within 0.5 ℃. The substantially constant temperature value may be about 37 ℃. The substantially constant temperature value may be about 36.5 ℃. The substantially constant temperature value may be 36.0-37.0 deg.c.

The process of the invention may comprise culturing a mammalian cell capable of expressing the antibody. The cell may be a recombinant cell. The antibody may be a recombinant antibody. The cell may comprise a nucleic acid encoding the antibody under the control of a promoter, which may be an inducible promoter.

In a second aspect, the invention provides a process for culturing mammalian cells, the process comprising a first culturing stage comprising culturing the cells at a first pH, and a second culturing stage comprising culturing the cells at a second pH, wherein the second pH is higher than the first pH and wherein the temperature of the process is maintained at a substantially constant value.

In a third aspect, the invention provides a process for culturing mammalian cells capable of expressing an antibody, the process comprising a first culture stage comprising inoculating the mammalian cells into a culture medium at a first pH and culturing the cells at the first pH, and a second culture stage comprising culturing the cells at a second pH higher than the first pH.

Brief Description of Drawings

Figure 1 shows an overview of a process for generating an anti-Ang 2/VEGF bispecific antibody, wherein the pH is maintained at 7.00 ± 0.05 for the duration of 14 days of run time.

In each of FIGS. 2A-G,3A-G,4A-G,5A-G,6A-G,7A-G,8A-G,9A-G,10A-F (series of FIGS. 2-10, B-G), the gray diamonds indicate that the process is maintained at 7.00 + -0.05, while the black squares indicate that the process involves a pH shift, as summarized in more detail below. FIGS. 2B,3B,4B,5B,6B,7B,8B,9B,10B (series B) eachThe panels show the average cell viability (in%); fig. 2C,3C,4C,5C,6C,7C,8C,9C,10C (C series) each show lactate concentration (in%); FIGS. 2D,3D,4D,5D,6D,7D,8D,9D,10D (series D) each show ammonium concentration (in%); FIGS. 2E,3E,4E,5E,6E,7E,8E,9E,10E (E series) each show product titers (in%); FIGS. 2F,3F,4F,5F,6F,7F,8F,9F (F series) each show pCO₂Concentration (in%) and FIGS. 2G,3G,4G,5G,6G,7G,8G,9G,10F (series G) each show osmolality (mOsm/kg). FIGS. 2B-G,3B-G,4B-G,5B-G,6B-G,7B-G,8B-G,9B-G (each of FIGS. 2 to 9, series B to G) each depict the average of two 2L bioreactors under identical conditions.

Figures 2A-2G show the effect of pH up-shift (Δ 0.20pH up-down (ramp)) on the process for generating anti-Ang 2/VEGF bispecific antibodies. FIG. 2A shows an overview of the process; the process starts with a pH set point of 7.00 ± 0.05 that rises to 7.20 ± 0.05 in a linear ramp over a period of 144 hours to 192 hours. Thereafter, the pH set point was maintained at 7.20 ± 0.05 for the remainder of the 14 day run time.

Figures 3A-G show the effect of pH up shift (Δ 0.20pH up and down) on the process for generating anti-Ang 2/VEGF bispecific antibodies. FIG. 3A shows an overview of the process; the process starts with a pH set point of 7.00 ± 0.05 that rises to 7.20 ± 0.05 in a linear ramp over a period of 156 hours to 208 hours. Thereafter, the pH was maintained at 7.20 ± 0.05 for the remainder of the 14 day run time.

Figures 4A-G show the effect of pH up shift (Δ 0.30pH up and down) on the process for generating anti-Ang 2/VEGF bispecific antibodies. FIG. 4A shows an overview of the process; the process begins with a pH maintained at a set point of 7.00 ± 0.05, which rises to 7.30 ± 0.05 in a linear ramp over a period of 192 hours to 240 hours. Thereafter, the pH was maintained at 7.30 ± 0.05 for the remainder of the 14 day run time.

Figures 5A-G show the effect of pH up shift (Δ 0.10pH up and down) on the process for generating anti-Ang 2/VEGF bispecific antibodies. FIG. 5A shows an overview of the process; the process starts with a pH set point of 7.00 ± 0.05 that rises to 7.10 ± 0.05 in a linear ramp over a period of 192 hours to 240 hours. Thereafter, the pH was maintained at 7.10 ± 0.05 for the remainder of the 14 day run time.

FIGS. 6A-G show the effect of an immediate pH up shift (. DELTA.0.20) on the process for generating an anti-Ang 2/VEGF bispecific antibody. FIG. 6A shows an overview of the process; the process starts at a pH set point of 7.00 ± 0.05. At 144 hours, the pH set point was immediately (in a single step) raised to 7.20 ± 0.05 and maintained at this level for the remainder of the 14 day run time.

Figures 7A-G show the effect of pH up shift (Δ 0.20 dead zone broadening) on the process for generating anti-Ang 2/VEGF bispecific antibodies. Fig. 7A shows an overview of the process. The process starts at a pH set point of 7.00 ± 0.05. At 144 hours, the pH dead zone widened from 0.05 to 0.25. At 192 hours, the pH set point was raised to pH7.20 and the pH dead band was returned to 0.05. The pH set point was maintained at 7.20 ± 0.05 for the remainder of the 14 day run time.

Figures 8A-G show the effect of pH up-shift (Δ 0.20, increasing with incremental set points of 0.05, from 7.00 to 7.20) on the process for generating anti-Ang 2/VEGF bispecific antibodies. Fig. 8A shows an overview of the process. The process starts at a pH set point of 7.00 ± 0.05. At 156 hours, the pH set point was raised to pH 7.05. + -. 0.05 and maintained for 12 hours. At 168 hours, the pH set point was raised to pH7.10 ± 0.05 and maintained for 12 hours. At 180 hours, the pH set point was raised to pH7.15 ± 0.05 and maintained for 12 hours. Finally, at 192 hours, the pH set point was raised to pH7.20 ± 0.05 and maintained at this level for the remainder of the 14 day run time.

Figures 9A-G show the effect of pH up-shift (Δ 0.20, widening of dead zone in increments of 0.05, from 0.05 to 0.25) on the process for generating anti-Ang 2/VEGF bispecific antibodies. Fig. 9A shows an overview of the process. The process starts at a pH set point of 7.00 ± 0.05. At 152 hours, the pH dead zone was broadened to. + -. 0.10 and maintained for 12 hours. At 164 hours, the pH dead zone was broadened to. + -. 0.15 and maintained for 12 hours. At 176 hours, the pH dead zone was broadened to. + -. 0.20 and maintained for 12 hours. At 188 hours, the pH dead zone was broadened to. + -. 0.25 and maintained for 12 hours. Finally, at 200 hours, the pH set point was raised to a dead zone of pH7.20 and ± 0.05 and maintained at this level for the remainder of the 14 day run time.

Figures 10A-F show the effect of different pH set points and dead zone settings on the process for generating anti-CSF-1R antibodies. Fig. 10A shows an overview of two processes. Process #1 starts with a pH set point of 7.00 ± 0.05 that is raised to 7.20 ± 0.05 in a linear ramp over a period of 144 hours to 192 hours, and then maintained at this level for the remainder of the 14 day run time. Process #2 started at a pH set point of 7.00 ± 0.05, which immediately dropped to 6.80 ± 0.05 at 48 hours and was maintained for 192 hours. Starting at 240 hours, the pH set point was raised from 6.80 ± 0.05 to 7.00 ± 0.05 in a linear ramp over a period of 240 hours to 288 hours, and then maintained at this level for the remainder of the 14 day run time. Figure 10B shows mean cell viability (in%); FIG. 10C shows lactate concentration (in%); figure 10D shows ammonium concentration (in%); figure 10E shows product titer (in%); FIG. 10F shows osmolality (mOsm/kg). Fig. 10B to 10F each depict the values of one bioreactor.

Figures 11A-11G show the effect of temperature downshifting on the process used to generate anti-Ang 2/VEGF bispecific antibodies. Fig. 11A shows an overview of the process. In process a, the temperature was maintained at 36.5 ℃ and the pH set point was maintained at 7.00 ± 0.05 throughout the 14 day run time. Process B begins with maintaining a temperature of 36.5 ℃. The temperature was reduced to 34.0 ℃ after 6/7 days and then maintained at this level for the remainder of the 14 day run time. The pH was always maintained at a constant set point of 7.00 ± 0.05. Figure 11B is a line graph showing the average cell viability (in%) for process a (grey diamonds) and process B (black squares). Fig. 11C is a line graph showing a time course profile of lactate concentration (in%) for process a (grey diamonds) and process B (black squares). Fig. 11D is a line graph showing the time course profile of ammonium concentration (in%) for process a (grey diamonds) and process B (black squares). FIG. 11E is a line graph showing the time course profile of product titer (in%) for Process A (grey diamonds) and Process B (black squares). FIG. 11F is a line graph showing pCO for Process A (grey diamonds) and Process B (black squares)₂Time course profile of concentration (in%) fig. 11G is a line graph showing the time course profile of osmolality for process a (grey diamonds) and process B (black squares) each of the graphs in fig. 11B to 11F is the average of two 2L bioreactors under the same conditions.

Figure 12 shows the relevant glycosylation structures of proteins produced in the processes disclosed herein.

Detailed Description

The present invention provides processes for culturing mammalian cells. The process of the present invention involves a pH shift up. In particular, the process of the present invention involves a continuous pH shift up. This reduces the accumulation of unwanted metabolites, such as lactate and ammonium. The process disclosed herein can improve moderate pCO₂Maintenance of levels and/or lower osmolality of the culture. Thus, the process may result in higher cell viability, higher cell concentration, higher cell productivity, higher product titer, and/or improved product quality.

The process comprising a pH up-shift may be improved relative to a control process in which the pH is the same throughout the process (same pH set point in the first and second incubation periods). These improvements are illustrated in FIGS. 2A-G through 9A-G, which show cell viability (series B), lactate levels (panel C), ammonium levels (panel D), product titer (panel E), pCO₂Improvement in profile (graph F) and osmolality (graph G). The process disclosed herein may advantageously avoid excessive lactate accumulation, especially at the late stages of the process and at the end of the process. The process may advantageously reduce ammonia production, and/or reduce excess ammonia build-up, particularly late in the process and at the end of the process.

The process is particularly suitable for industrial scale cell culture and culture of cells producing therapeutic products the culture vessel for such cell culture may be referred to as a bioreactor the industrial scale process may be a process wherein the volume of the culture medium is at least about 50L, 100L, 500L 0,1000L, or 10000L the industrial scale process may be a process wherein the volume of the culture medium is at least about 20L, 30L or 40L the industrial scale process may be a process wherein the volume of the culture medium is about 20-100L, 20-500L, 20-1000L, 50-100L, 50-500L, 50-1000L, 50-5000L, 50-10000L, 50-20000L, 100- -1000L, 100- -L, 100- > 10000L, 100- > 20000L, 500- > 5000L, 500- > L, 500- > 10000L.

The process of the present invention involves a pH shift up. More specifically, the process of the invention comprises a first incubation period at a first pH and a second incubation period at a second pH, wherein the second pH is higher than the first pH. The first culture stage can comprise inoculating the mammalian cells into a culture medium at a first pH. The first culturing period may begin on day 0 of the process. The first culture stage is the initial culture stage. The first culturing stage may be a stage in which seeding and lag phase growth of cells occurs. The first cultivation phase may be directly followed by a pH shift-up, which is directly followed by the second cultivation phase. The second culturing stage may comprise harvesting the cells and/or products produced by the cells. The process may be terminated at the termination of the second culturing stage.

The process is particularly suitable for industrial scale cell culture and for the culture of cells producing therapeutic products. The process comprises a first culturing phase carried out at a first pH and a second culturing phase carried out at a second pH higher than the first pH.

Disclosed herein is a fed-batch process for culturing mammalian cells, the process comprising a first culture phase comprising inoculating mammalian cells into a culture medium at a first pH and culturing the cells at the first pH, and a second culture phase comprising culturing the cells at a second pH higher than the first pH.

Disclosed herein is a fed-batch process for culturing CHO cells expressing an antibody, such as, for example, pannouperhaps mab, comprising a first culturing stage comprising inoculating mammalian cells into a culture medium at a first pH and culturing the cells at the first pH, and a second culturing stage comprising culturing the cells at a second pH higher than the first pH, wherein the first pH is about 7.0 and wherein the second pH is about 0.1,0.2,0.3,0.4,0.5, or 0.1-0.5 units higher than the first pH.

The first pH may be a value in the range of 6.5-7.5,6.6-7.4,6.7-7.3,6.8-7.2, or 6.9-7.1. The first pH may be about 7.0. The first pH may be about 7.0 and the second pH may be about 7.2.

The first pH may have a value of about pH 6.5,6.6,6.7,6.8,6.9,7.0,7.1,7.2,7.3,7.4, or 7.5. The second pH may have a value of about pH6.6, 6.7,6.8,6.9,7.0,7.1,7.2,7.3,7.4,7.5, or 7.6. The first pH may have a value of about pH 6.5 to 7.5. The second pH may have a value of about pH6.6 to 7.6, wherein the second pH is higher than the first pH.

The first pH may have a value of pH 6.5 ± 0.05,6.6 ± 0.05,6.7 ± 0.05,6.8 ± 0.05,6.9 ± 0.05,7.0 ± 0.05,7.1 ± 0.05,7.2 ± 0.05,7.3 ± 0.05,7.4 ± 0.05, or 7.5 ± 0.05. The second pH can have a value of pH6.6 + -0.05, 6.7 + -0.05, 6.8 + -0.05, 6.9 + -0.05, 7.0 + -0.05, 7.1 + -0.05, 7.2 + -0.05, 7.3 + -0.05, 7.4 + -0.05, 7.5 + -0.05, or 7.6 + -0.05. The first pH may have a value of pH 6.5 ± 0.05 to 7.5 ± 0.05. The second pH may have a value of pH6.6 ± 0.05 to 7.6 ± 0.05, wherein the second pH is higher than the first pH. The second pH may be about 0.1 pH units, or at least about 0.1 pH units, higher than the first pH. A second pH that is about 0.1 pH units higher than the first pH may be referred to herein as a pH Δ 0.1. The second pH may be about 0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9, or 1.0 pH unit higher than the first pH, or at least about 0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9, or 1.0 pH unit. The second pH may be about 0.1 to 0.5 pH units higher than the first pH, about 0.1 to 0.4 units higher than the first pH, or about 0.1 to 0.3 pH units higher than the first pH. The first pH may be about 7.0. The second pH may be about 7.1-7.4,7.1-7.5,7.2-7.4, or about 7.2-7.5.

The first pH may be a value in the range of 6.50-7.50,6.60-7.40,6.70-7.30,6.80-7.20, or 6.90-7.10. The first pH may be about 7.00. The first pH may be about 7.00 and the second pH may be about 7.20.

The first pH may have a value of about pH 6.50,6.60,6.70,6.80,6.90,7.00,7.10,7.20,7.30,7.40, or 7.50. The second pH may have a value of about pH 6.60,6.70,6.80,6.90,7.00,7.10,7.20,7.30,7.40,7.50, or 7.60. The first pH may have a value of about pH 6.5 to 7.5. The second pH may have a value of about pH6.6 to 7.6, wherein the second pH is higher than the first pH.

The second pH may be about 0.10pH units, or at least about 0.10pH units, higher than the first pH. A second pH that is about 0.10pH units higher than the first pH may be referred to herein as a pH Δ 0.10. The second pH may be about 0.20,0.30,0.40,0.50,0.60,0.70,0.80,0.90, or 1.00 pH units higher than the first pH, or at least about 0.20,0.30,0.40,0.50,0.60,0.70,0.80,0.90, or 1.00 pH units. The second pH may be about 0.10 to 0.50 pH units higher than the first pH, about 0.10 to 0.40 units higher than the first pH, or about 0.10 to 0.30pH units higher than the first pH. The first pH may be about 7.00. The second pH may be about 7.10-7.40,7.10-7.50,7.20-7.40, or about 7.20-7.50.

The processes disclosed herein can include controlling pH using a pH set point. The set point is a desired or target pH value. The process may be in a bioreactor or other controlled culture facility that can be programmed to adjust pH using a pH set point. In this context, the bioreactor contains at least one pH probe to monitor culture pH. Deviation of the culture pH from its set point may trigger a pH corrective action (or pH adjustment action) to bring the pH closer to the set point. The pH corrective action may include the addition of an agent that lowers the pH (such as CO)₂HCl or any other suitable acid) or adding an agent that raises the pH (such as NaOH or any other suitable base). The pH corrective action may include removing agents that lower the pH (e.g., removing CO)₂Known as CO₂Stripping). The pH corrective action may comprise reducing the addition of an agent that reduces or increases the pH, thereby increasing or decreasing the pH, respectively, e.g., reducing the addition of CO₂To maintain a relatively high pH.

The process may include controlling the pH using a dead zone. The dead zone defines the zone in which no pH remediation action is triggered. The pH corrective action is triggered only when the pH drifts outside the zone defined by the dead zone. The pH set point may have a dead zone. The dead zone may be ± 0.05, i.e., the dead zone may be ± 0.05 pH units with respect to the pH set point.

The process disclosed herein can comprise controlling the pH using a pH set point, wherein the set point is set to a first pH in a first incubation period and is set to a second pH in a second incubation period. The set point may be maintained at a first pH during the first incubation period. The set point may be maintained at the second pH during the second culturing period. The set point may be maintained at a first pH in the first incubation period and at a second pH in the second incubation period. The maintenance of the set-point in the first and second cultivation phases may have a duration as listed below with respect to the duration of the first and second cultivation phases, respectively. The set point for the first culture stage, or the second culture stage, or both, can be maintained for at least 2,4,6,8,12, or 18 hours; or 3 to 10 days, 4 to 8 days, or 4 to 6 days; or at least 1,2,3,4,5,6,7,8,9,10,11,12,13, or 14 days. The set point may be set to pH 6.50,6.60,6.70,6.80,6.90,7.00,7.10,7.20,7.30,7.40, or 7.50 in the first cultivation stage. The set point may be set to pH 6.60,6.70,6.80,6.90,7.00,7.10,7.20,7.30,7.40,7.50, or 7.60 in the second incubation period, wherein the pH set point of the second incubation period is higher than the pH set point of the first incubation period. The pH set point of the second culture stage can be about 0.10pH units, or at least about 0.10pH units, higher than the pH set point of the first culture stage. A second pH that is about 0.10pH units higher than the first pH may be referred to herein as a pH Δ 0.10. The second pH set point may be about 0.20,0.30,0.40,0.50,0.60,0.70,0.80,0.90, or 1.00 pH units, or at least about 0.20,0.30,0.40,0.50,0.60,0.70,0.80,0.90, or 1.00 pH units higher than the first pH set point. The second pH set point may be about 0.10-0.50 pH units higher than the first pH set point, about 0.10-0.40 units higher than the first pH set point, or about 0.10-0.30 pH units higher than the first pH set point. The first pH set point may be about 7.00. The first pH set point may be a value in the range 6.50-7.50,6.60-7.40,6.70-7.30,6.80-7.20, or 6.90-7.10. The pH set point may have the same dead zone throughout the process, i.e., the dead zone may have a constant value. The pH set point in the first cultivation phase may have the same dead zone as the dead zone of the pH set point in the second cultivation phase. Alternatively, the pH set point in the first culture phase and the pH set point in the second culture phase may have different dead zones from each other.

The pH set point in the first culture phase and/or the second culture phase may have a dead zone of + -0.50, a dead zone of + -0.25, a dead zone of + -0.10, a dead zone of + -0.05, a dead zone of + -0.01, or a dead zone of + -0.005 pH units.

The pH set point in the first culture stage may be 7.00 ± 0.05. The pH set point in the second culturing phase may be from 7.10. + -. 0.05 to 7.40. + -. 0.05. The pH set point in the first culture stage may be 7.00. + -. 0.05 and the pH set point in the second culture stage may be 7.10. + -. 0.05 to 7.40. + -. 0.05. The pH set point in the first culture stage may be 7.00. + -. 0.05 and the pH set point in the second culture stage may be 7.10. + -. 0.05. The pH set point in the first culture stage may be 7.00. + -. 0.05 and the pH set point in the second culture stage may be 7.20. + -. 0.05. The pH set point in the first culture stage may be 7.00. + -. 0.05 and the pH set point in the second culture stage may be 7.30. + -. 0.05. The pH set point in the first culture stage may be 7.00. + -. 0.05 and the pH set point in the second culture stage may be 7.40. + -. 0.05.

The first pH may be a range having a first lower limit and a first upper limit. The second pH may be a range having a second lower limit and a second upper limit. The second lower limit may be equal to or higher than (≧) the first upper limit of the first pH, or higher than (>) the first upper limit of the first pH. In the process of the invention, the first culture stage comprises culturing the cells in a range having a first lower limit and a first upper limit, and the second culture stage comprises culturing the cells in a range having a second lower limit and a second upper limit.

The second lower limit may be equal to the first upper limit of the first pH. For example, the first pH may be a range having a first lower limit of 6.95 and a first upper limit of 7.05. For example, the second pH may be a range having a second lower limit of 7.05 and a second upper limit of 7.15. The second lower limit may be greater than the first upper limit of the first pH. For example, the first pH may be a range having a first lower limit of 6.95 and a first upper limit of 7.05. For example, the second pH may be a range having a second lower limit higher than 7.05 and a second upper limit higher than 7.15.

The second lower limit may be at least 0.10pH units higher than the first upper limit. For example, the first pH may be a range having a first lower limit of 6.95 and a first upper limit of 7.05, and the second pH may be a range having a second lower limit of 7.15 and a second upper limit of 7.25.

The second lower limit may be at least 0.20pH units higher than the first upper limit. For example, the first pH may be a range having a first lower limit of 6.95 and a first upper limit of 7.05, and the second pH may be a range having a second lower limit of 7.25 and a second upper limit of 7.35.

The second lower limit may be 0.10pH units, or at least 0.10pH units, higher than the first upper limit. The second lower limit may be 0.20,0.30,0.40,0.50,0.60,0.70,0.80,0.90, or 1.00 pH units higher than the first upper limit, or at least 0.20,0.30,0.40,0.50,0.60,0.70,0.80,0.90, or 1.00 pH units.

The first pH and/or the second pH may be a range having a width of 1.00,0.50,0.20,0.10,0.02, or 0.01 pH units. The first pH may be a range having a midpoint value of pH 6.50,6.60,6.70,6.80,6.90,7.00,7.10,7.20,7.30,7.40, or 7.50. The second pH may be a range having a midpoint value of pH 6.60,6.70,6.80,6.90,7.00,7.10,7.20,7.30,7.40,7.50, or 7.60. For example, the first pH may be a range having a midpoint value of pH7.00 and a width of 0.10, which is a range of pH 6.95 to 7.05. The second pH may be a range having a midpoint value of pH7.20 and a width of 0.10, which is a range of pH7.15 to 7.25.

The process may be a process that does not involve a pH shift down (negative shift). That is, the process may be one that does not include any significant pH reduction. A significant pH reduction may be a reduction of at least 0.10,0.20,0.30,0.40,0.50,0.60,0.70,0.80,0.90, or 1.00 pH units, which may last for at least 1,5, or 30 minutes. The process may be a process that does not involve culturing the cells at any pH lower than the first pH.

The process of the present invention involves a pH shift up. The pH is shifted up between the first and second cultivation stages. The pH up-shift is a positive shift or a basic shift, i.e. the pH up-shift is a pH increase. The pH up shift is an increase in pH from a first pH to a second pH.

The pH shift up may be gradual. That is, the pH up shift may comprise a gradual rise in pH over time. The pH may be gradually raised from the first pH to the second pH, for example over a period of 24-72 hours. The time period may be 24-72 hours, 36-60 hours, or about 48 hours. The time period may be 6,12,24,36 or 48 hours, or at least 6,12,24,36 or 48 hours. The gradual increase in pH may increase the pH by about 0.001,0.002,0.003,0.004,0.005,0.006,0.007,0.008,0.009,0.01, or 0.05 pH units per hour, or less than about 0.001,0.002,0.003,0.004,0.005,0.006,0.007,0.008,0.009,0.01, or 0.05 pH units per hour. The gradual increase in pH may increase the pH by about 0.001 to 0.05,0.001 to 0.01,0.001 to 0.005, or 0.002 to 0.008 pH units per hour.

Alternatively, the pH shift up may be "non-gradual". Such pH upshifts can have a duration of less than 2 hours, or less than 1 hour, or less than 30,20,10,9,8,7,6,5,4,3,2, or 1 minute. The non-gradual increase in pH may increase the pH by about 0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0,1.5,2.0,2.5, or 3.0 pH units per hour, or at least about 0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0,1.5,2.0,2.5, or 3.0 pH units per hour.

Gradually increasing the pH can advantageously minimize deleterious effects on mammalian cells. The detrimental effect may be associated with an immediate or sudden increase in the pH of the culture medium, which effect is avoided by a gradual increase in pH. The process of the invention in which the pH is gradually increased may have improved product titer and/or product quality compared to a process in which the pH is not gradually increased, or in which the pH set point is increased in a single step as discussed below.

The process of the present invention comprising controlling pH using a pH set point may comprise a pH up shift, wherein the set point is either (a) gradually or (b) immediately increased from a first pH to a second pH.

As the pH set point is gradually increased, this may include the set point being continuously increased from the first pH to the second pH over a period of time. Alternatively, this may comprise a step-wise increase of the set point from the first pH to the second pH over a period of time. This period of time may be 24-72 hours, 36-60 hours or about 48 hours. This period of time may be at least 6,12,24,36 or 48 hours.

The gradual continuous increase in the pH set point may be referred to as a pH increase or decrease, or a pH linear increase or decrease. As such, the process of the present invention may comprise a pH upshifting as a pH increase or decrease, wherein the setpoint is continuously increased from the first pH to the second pH.

The gradual stepwise increase in the pH set point may comprise discrete steps or increments. This may be referred to as a gradual increase. Each discrete step may raise the pH set point by at least about 0.05 pH units. Each discrete step may increase the pH set point by at least about 0.01,0.05,0.10,0.15,0.20, or 0.25 pH units. Each discrete step may be maintained for a period of at least about 12 hours. Each discrete step may be maintained for a period of at least about 1,2,4,6,8,12,18,24, or 36 hours, or at least about 1-24 or 6-18 hours.

The gradual stepwise increase in the pH set point may be performed by repeatedly increasing the pH set point until the pH set point reaches the second pH. The stepwise increase may be repeated in a series of discrete steps, or increments, to increase the pH set point.

For example, the gradual stepwise increase in the pH set point may be performed as follows:

a) incrementally increasing the pH set point from the first pH to an intermediate pH set point and maintaining the culture at this intermediate pH set point for a period of time;

b) incrementally increasing the pH set point to a higher intermediate pH set point and maintaining the culture at this higher intermediate pH set point for a period of time; and

c) repeating step b) until the pH set point reaches a second pH.

Incrementally increasing the pH set point can comprise increasing the pH set point by 0.05 pH units or increments of at least 0.05 pH units. The increment can be about 0.01,0.05,0.10,0.15,0.20, or 0.25 pH units or at least about 0.01,0.05,0.10,0.15,0.20, or 0.25 pH units. The intermediate pH set point may be maintained for a period of at least about 12 hours. Each discrete step or increment may be maintained for a period of at least about 1,2,4,6,8,12,18,24, or 36 hours, or at least 1-24 or 6-18 hours. Each discrete step may be about 0.05 pH units maintained for about 12 hours.

A gradual increase in pH set point as a stepwise increase in pH set point may be preferred in some circumstances. For example, when the technical limitations mean that the bioreactor cannot be programmed to gradually increase the pH set point with a continuous increase.

For example, example 6 below involves an immediate increase in the pH set point, and the time it takes for fermentation to increase from the first pH to the second pH is about 10 minutes for a 2L fermentation and 1-2 hours for a 1000L fermentation.

The dead zone may be maintained at a constant value throughout the process. For example, the dead zone may be ± 0.05 pH units around the set point throughout the process. In embodiments where the pH set point is gradually increased, the dead zone may be maintained at a constant value during the first incubation period, the pH shift up, and the second incubation period. Embodiments of processes in which the dead zone is maintained at a constant value are shown in fig. 2A,3A,4A,5A,6A,8A, and 10A.

Alternatively, the dead zone may be widened. In particular, the pH shift up may comprise dead zone broadening. The dead zone may widen instantaneously, i.e., the dead zone may widen in a single step. One embodiment of a process in which the dead zone is widened in a single step is shown in fig. 7A. Alternatively, the dead zone may be gradually widened, for example, the dead zone may be widened in a series of discrete steps or increments. One embodiment of a process in which the dead zone widens in a series of increments is shown in fig. 9A.

The pH up-shift may comprise a single step, or an immediate widening of the dead zone. The shifting up the pH may comprise widening the dead zone in a single step from an initial value around a set point set to a first pH to a wider value around the set point set to the first pH such that it encompasses a second pH, and then increasing the pH set point to the second pH. Concurrently with the increase of the pH set point to the second pH, the dead zone may be restored to its initial value around the pH set point. Alternatively, the dead zone may be restored to a value different from its initial value. The dead zone may be restored to a value that does not encompass the first pH.

For example, the process may comprise a first incubation period at pH7.00 and a second incubation period at pH 7.20; the pH set point in the first and second culturing phases may have a dead zone of ± 0.05; the shifting up the pH may comprise widening the dead zone around the set point set to the first pH from ± 0.05 to ± 0.25 (from pH7.00 ± 0.05 to pH7.00 ± 0.25) in a single step such that it encompasses the second pH, and then increasing the pH set point to the second pH. Simultaneously with the increase of the pH set point to the second pH, the dead zone may be restored to ± 0.05(pH 7.20 ± 0.05) around the pH set point set to the second pH. Fig. 7A shows a process according to this embodiment.

The pH shift up may comprise widening the dead zone from ± 0.05 to ± 0.25 in a single step. The shifting up the pH may comprise broadening the dead zone from ± 0.01 to ± 0.05, from ± 0.05 to ± 0.25, from ± 0.05 to ± 0.50, or from ± 0.10 to ± 0.50 in a single step.

The dead zone may widen in a single step and the widened dead zone may be maintained for about 12,18,24,36,48,60, or 72 hours or at least 12,18,24,36,48,60, or 72 hours. The widened dead zone may be maintained for 36-60,40-56 or 44-52 hours, or about 48 hours. The widened dead zone may be maintained until the pH reaches the second pH.

The pH up shift may comprise a gradual widening of the dead zone. The pH up-shift may comprise repeatedly widening the dead zone in a series of discrete steps or increments. The pH up-shifting may comprise repeatedly widening the dead zone in a series of discrete steps or increments from an initial value around a pH set point set to a first pH until the dead zone encompasses a second pH, and then raising the pH set point to the second pH. Concurrently with the increase of the pH set point to the second pH, the dead zone may be restored to its initial value around the set point set to the second pH. Alternatively, the dead zone may be restored to a value different from its initial value. The dead zone may be restored to a value that does not encompass the first pH.

For example, the process may comprise a first incubation period at pH7.00 and a second incubation period at pH 7.20; the pH set point in the first and second culturing phases may have a dead zone of ± 0.05; the upward shift in pH may comprise incrementally widening the dead zone around the set point set to the first pH from ± 0.05 in a series of increments, for example four increments, to a value encompassing pH 7.20. The dead zone may then be restored to ± 0.05(pH 7.20 ± 0.05) around the pH set point set to the second pH simultaneously with the pH being raised to the second pH. Fig. 9A shows a process according to this embodiment.

The pH shift up may comprise widening the dead zone in a series of increments or discrete steps. The increment may be 0.05 pH units. The incremental or discrete step may be 0.01,0.02,0.03,0.04, or 0.05 pH units or less than 0.01,0.02,0.03,0.04, or 0.05 pH units. There may be at least two, three, four or five increments. The increments may be the same size as one another or different sizes. For example, a dead zone of 0.05 can be widened to 0.25 in a series of four 0.05 pH unit increments, such as 0.10, ± 0.15, ± 0.20, ± 0.25.

The dead zone may widen in a series of increments or discrete steps, and each increment or discrete step may last for about 12 hours or at least 12 hours. Each incremental or discrete step may be maintained for about 2,4,6,8,12,18, or 24 hours or at least 2,4,6,8,12,18, or 24 hours. The increments may have the same duration as one another, or different durations.

The pH shift may comprise a continuous gradual widening of the dead zone over a period of time. The pH up-shift may comprise continuously widening the dead zone from an initial value around a pH set point set to a first pH until the dead zone encompasses a second pH, and then increasing the pH set point to the second pH. Concurrently with the increase of the pH set point to the second pH, the dead zone may be restored to its initial value around the set point set to the second pH. Alternatively, the dead zone may be restored to a value different from its initial value. The dead zone may be restored to a value that does not encompass the first pH.

For example, the process may comprise a first incubation period at pH7.00 and a second incubation period at pH 7.20; the pH set point in the first and second culturing phases may have a dead zone of ± 0.05; the upward pH shift may comprise continuously widening the dead zone around the set point set to the first pH from + 0.05 to a value encompassing pH 7.20. The dead zone may then be restored to ± 0.05(pH 7.20 ± 0.05) around the pH set point set to the second pH simultaneously with the pH being raised to the second pH.

The period of time for which the dead zone continuously widens may be 24-72 hours, 36-60 hours, or about 48 hours. This period of time may be at least 6,12,24,36 or 48 hours.

The dead zone incremental increase may be preferred in some situations. For example, when the technical limit means that the bioreactor cannot be programmed to gradually increase the pH set point with a continuous increase or when the technical limit means that the bioreactor cannot be programmed to continuously widen the dead zone.

The pH up shift may comprise an increase in the set point and a widening of the dead zone in any operable combination as described above. In some cases, combinations of the embodiments shown in fig. 2A to 9A may be preferred, for example, to minimize fluctuations in pH (pH perturbations).

The pH can be measured online or offline. The pH values discussed herein refer to on-line values unless otherwise indicated. The pH can be measured at 37.0. + -. 1.0 ℃. The pH can be measured at 36.5. + -. 1.0 ℃. The pH can be used in the bioreactor for temperature measurement of the production fermentation. For on-line measurements, the pH is measured by a probe in the bioreactor. Suitable pH probes for on-line measurements include Mettler-Toledo InPro pH sensors. For off-line measurements, the pH is measured by a probe in the sample from the bioreactor, for example in a temperature controlled sample container. Suitable equipment for off-line measurements include a Knick Portavo 907 pH meter, a pH 3310 WTW, and a Mettler-Toledo InPro Semi-Micro pH electrode. Suitable sampling devices include9mL(Sarstedt)。

The protocol for off-line pH measurement may be as follows, pre-warming the benchtop pH electrode to a measurement temperature (e.g., 37.0 + -1.0 deg.C) by immersion in a water bath or aluminum block at the measurement temperature; the sample is then heated to a measurement temperature (e.g. 37.0 ± 1.0 ℃) and the pH is measured as soon as the sample reaches the measurement temperature (e.g. after 3 minutes); then wait until a stable pH is reached (e.g., less than 1 minute); the stable pH was used as an off-line measurement. The pH measuring device can be calibrated using a calibration buffer, such as Duracal buffer (Hamilton).

The online measurement can be recalibrated if it deviates significantly from the offline measurement. For example, if the on-line measurements differ by more than 0.05 pH units. The recalibration procedure may comprise taking a second sample from the bioreactor if the first sample is measured as having an offline pH value that differs from the online value by more than 0.05 pH units. The online (internal) pH probe is recalibrated by setting the pH value determined by the offline (external) pH probe if the second sample is also measured as having an offline pH value that differs from the online value by more than 0.05 pH units.

The process of the invention may comprise adding a pH-up feed medium to the culture medium. pH up-shift feed medium may have a basic pH relative to the culture medium. Alternatively, or in addition, the pH-up feed medium may contain factors, such as nutrients, that increase the pH of the culture medium when metabolized by the cells. For example, certain amino acids, such as glutamate, aspartate, and alanine, are metabolized by cells to produce ammonium. The pH-up-shift feed medium may contain glutamate, aspartate and/or alanine.

Alternatively, or in addition, the pH shift may comprise the addition of an alkaline agent (base), such as NaOH, Na₂CO₃Or NaHCO₃Added to the culture medium. Basic agents may be referred to as bases and base salts.

Alternatively, or in addition, the pH shift up may comprise allowing the cell culture to accumulate cell metabolites that increase the pH of the culture medium.

Alternatively, or additionally, the pH shift up may comprise removal of dissolved CO from the culture medium₂For example byStripping CO from a bioreactor₂. Stripping CO from a bioreactor₂Cause dissolution of CO₂Leaving the culture medium. Since the pH of the culture medium depends on dissolved CO₂And bicarbonate (HCO)₃ ^-) Thus removing dissolved CO from the culture medium₂The pH of the culture medium is changed.

In some embodiments comprising adding a pH up-shifting feed medium and/or allowing the cell culture to accumulate metabolites that increase the pH of the culture medium, the process does not comprise a pH increase at a rate faster than 0.15,0.20,0.25, or 0.5 pH units per 24 hours.

In some embodiments comprising adding a pH up-shift feed medium and/or allowing the cell culture to accumulate metabolites that raise the pH of the culture medium, the process also does not comprise adding an alkaline agent (base), such as NaOH, Na₂CO₃,NaHCO₃The concentrated solution of (2) is added to the culture medium. Concentrated solutions of alkaline agents (bases) are those having a concentration higher than, for example, 0.5,0.6,0.7,0.8,0.9, or 1.0M. A process in which the pH is shifted up without involving the addition of a concentrated solution of base can advantageously minimize the increase in osmolality of the culture.

The addition of a pH-up shift feed medium is advantageous for the fed-batch process of the invention, as it effectively achieves both feeding and increasing the pH of the cell culture in a single process step. Adding the pH up-shift feed medium over a period of time also pushes the pH up gradually over a period of time, which may be advantageous, as discussed above.

The process of the invention comprises inoculating the cells into a culture medium. Inoculating a cell into a culture medium refers to adding one or more cells, or a population of cells, into a sterile culture medium. Inoculation may also be referred to as seeding. Inoculation of cells into culture medium defines day 0 of the process in the context of the duration and timing of the culture process.

The process of the invention may be a fed-batch process (whiteford, 2006). A fed-batch process is a cell culture process or fermentation process in which cells are cultured in a culture vessel or bioreactor, and one or more nutrients necessary for cell growth or product formation are added to the bioreactor during the culturing process. The nutrients may be added to the culture vessel either continuously or intermittently. The nutrients may be added in the form of a feed medium. Nutrients include sugars and amino acids, as well as vitamins, nucleosides, organic chemical compounds, and inorganic metal salts. The feed medium may comprise sugars (mono-or disaccharides), amino acids, vitamins, nucleosides, organic chemical compounds, and inorganic metal salts. The cells are maintained in the bioreactor throughout the cell culture process until the cells and or cell products are harvested.

In contrast, a batch process is a cell culture process in which the cells and all essential medium components are added to the culture vessel at the beginning of the fermentation process and then no nutrients are added to the culture vessel. Unlike fed-batch processes, no feed medium is added to the culture in batch processes. For example, no sugar (e.g., glucose) and/or no amino acid is added in a batch process.

The fed-batch process of the present invention is not a batch process. The fed-batch process of the invention may comprise the addition of a sugar to the culture medium. The fed-batch process of the invention may comprise adding a feed medium to the culture medium.

Cells were inoculated into culture medium. The culture medium may be a commercial culture medium. The culture medium may be chemically defined and protein and serum free, e.g. CD CHO AGT^TMCulture medium (Thermo FisherScientific, recipe No. a 15649).

In the fed-batch process of the invention a feed medium ("feed 1") is added to the culture medium. In this context, the initial culture medium may be referred to as a basal medium, which is supplemented with a feed medium during a fed-batch cultivation process. The basal medium may be chemically defined and protein and serum free, e.g. CD CHO AGT^TMCulture medium (ThermoFisher Scientific, formulation No. A15649). The base medium can be any suitable commercial medium, including a custom-made medium, used according to the supplier's or manufacturer's instructions.

The feed medium may comprise further methionine, threonine, serine, tyrosine and glycine. The feed medium may comprise further methionine, threonine, serine, tyrosine and glycine at respective concentrations in the range of about 0.5g/l to about 1.5 g/l.

Feed medium in the range of about 2.0 to about 3.0 wt% of the initial culture weight per day may be added to the culture medium.

The feed medium may, for example, be a medium containing feed base 5 medium (Thermo Fisher Scientific, Cat. No. 074-91011DW), feed base 2 medium (Thermo Fisher Scientific, Cat. No. 074-91007MV), feed base 6 medium (Thermo Fisher Scientific, Cat. No. 074-91012MW), minimal essential medium vitamins (MEM100X, Thermo Fisher Scientific, Cat. No. 074-91008BX), CD CHO AGT^TMThe feed medium may be a medium containing specific ratios of feed base 5 medium, feed base 2 medium, feed base 6 medium, minimal essential medium vitamins, SPE and CD CHO AGT medium the feed medium may be prepared by combining feed base 5 medium, feed base 2 medium, and feed base 6 medium to provide a feed medium, which may also include any minimal essential medium vitamins, SPE and CD CHO AGT medium.

The fed-batch process of the invention may further comprise the addition of a pH-shift-up feed medium ("feed 2"). The pH-up feed medium may comprise nutrients that increase the pH when metabolized by the cells. The pH-shifting feed medium may comprise elevated levels of glutamate, aspartate, and/or alanine relative to the feed medium. The pH-shifting feed medium may comprise additional lysine, threonine, serine, valine, leucine, and tryptophan. The pH-shifting feed medium may comprise additional lysine, threonine, serine, valine, leucine, and tryptophan at respective concentrations in the range of about 0.5g/l to about 6.0 g/l.

The pH-shifted feed medium may be, for example, a feed medium containing a feed base 8 medium (Thermo Fisher Scientific, catalog No. 074-91013RW) and a feed base 9 medium (Thermo Fisher Scientific, catalog No. 074-91014 EW). The pH-up feed medium can be prepared by combining feed base 8 medium and feed base 9 medium to provide a pH-up medium. The pH upshifting medium can have a pH of about 10-11. The relative proportions of feed base 8 medium and feed base 9 medium can be adjusted and tested for effectiveness in achieving the desired pH shift-up in any cell culture using conventional techniques, for example in a preparative design of the experimental process.

pH up-shifting feed medium can have a pH that is basic relative to the culture medium. The pH-up feed medium may have a pH of 10.0 or more. The pH-up medium may have a pH of 8.0,9.0, or above 10.0. The pH-shifting medium can have a pH of about 8.0-12.0, about 10.0-11.0, or about 10-11. The pH up-shifting feed medium may have a pH of about 10.0,10.5, or 11.0. The pH up-shifting feed medium can have a pH of about 10 or about 11.

An upward shift feed medium in the range of about 0.5 to about 1.5 wt% of the initial culture weight per day may be added to the culture medium.

The fed-batch process of the invention may comprise the addition of a feed medium to the culture medium during the first cultivation phase, followed by the addition of a pH-shifting medium to the culture medium. As discussed below, the feed medium may be replaced with a pH-up medium after a certain number of days. As discussed below, the addition of pH-shift medium to the culture may be several days before the pH-shift.

Additional glucose feed solutions may be added to the culture to maintain a suitable glucose concentration, e.g.. gtoreq.3 g/l.

The experimental examples below demonstrate that pH-up itself causes a favourable effect in the process performed according to the invention (rather than pH-up of the components of the medium). This is because each example of a process according to the invention was compared to a control process, in which a pH-shifting medium was added to the fermentation but by adding CO₂To resist any pH increase (see for example the recipe described in example 1)Case). This means that the advantageous effect observed in examples 2 to 9 and example 10 process #1 is directly attributable to the pH up-shift of the process according to the invention. The pH shift up of the process according to the invention can be carried out using any suitable culture medium.

Example 10 also demonstrates that the pH up-shift according to the invention (process #1, wherein the pH up-shift is followed by a second cultivation phase at a higher pH than the first cultivation phase) is advantageous compared to a process (process #2) in which there is a pH up-shift but no cultivation phase at a higher pH than the first cultivation phase (cultivation phase in which the cells are inoculated into the medium or the cultivation phase starting at day 0).

Inoculation of cells into culture medium defines day 0 of the process in the context of the duration and timing of the culture process.

The process of the invention may comprise a first culturing period having a duration of 3,4,5 or 6 days or at least 3,4,5 or 6 days. The first culturing stage may have a duration of 1,2,4,6,8,12, or 18 hours or at least 1,2,4,6,8,12, or 18 hours. The first culturing period may have a duration of 3 to 10 days, 4 to 8 days, or 4 to 6 days. The first culturing stage can have a duration of 1,2,3,4,5,6,7,8,9,10,11,12,13, or 14 days or at least 1,2,3,4,5,6,7,8,9,10,11,12,13, or 14 days. The first culturing stage may begin with seeding of the cells into a cell culture medium. When the mammalian cells are CHO cells, the first culturing stage may have a duration of 6,7,8 or 9 days. Reference to a first culturing phase having a certain duration may in particular mean that the culture is at or maintained at a first pH for that duration. In this context, "maintained at" may mean "continuously maintained at". That is, the process of the invention may comprise a first culturing stage comprising culturing the cells at a first pH, or maintaining the first pH, or maintaining a set point set to the first pH for 1,2,4,6,8,12, or 18 hours or at least 1,2,4,6,8,12, or 18 hours; or 3 to 10 days, 4 to 8 days, or 4 to 6 days; or 1,2,3,4,5,6,7,8,9,10,11,12,13, or 14 days or at least 1,2,3,4,5,6,7,8,9,10,11,12,13, or 14 days.

The process of the present invention involves a continuous pH shift up. A sustained pH up-shift is a pH up-shift that is maintained for a certain duration of time. For example, a sustained pH up-shift may be a pH up-shift that is maintained for at least 1 hour or for a duration disclosed herein as the duration of the first and/or second incubation periods. The process of the invention may comprise a second culturing period having a duration of 4,5, or 6 days or at least 4,5, or 6 days. The second culturing period may have a duration of 1,2,4,6,8,12, or 18 hours or at least 1,2,4,6,8,12, or 18 hours. The second culturing period may have a duration of 3 to 10 days, 4 to 8 days, or 4 to 6 days. The second culturing period may have a duration of 1,2,3,4,5,6,7,8,9,10,11,12,13, or 14 days or at least 1,2,3,4,5,6,7,8,9,10,11,12,13, or 14 days. The second culturing stage may continue until the process is complete. The second culturing stage may be terminated by harvesting the cells and/or the products expressed by the cells. When the mammalian cells are CHO cells, the second culturing stage may have a duration of 6,7,8 or 9 days. Reference to a second culturing phase having a certain duration may in particular mean that the culture is at or maintained at a second pH for that duration. In this context, "maintained at" may mean "continuously maintained at". That is, the process of the invention may comprise a second culturing stage comprising culturing the cells at a second pH, or maintaining the set point set to the second pH for 1,2,4,6,8,12, or 18 hours or at least 1,2,4,6,8,12, or 18 hours; or 3 to 10 days, 4 to 8 days, or 4 to 6 days; or 1,2,3,4,5,6,7,8,9,10,11,12,13, or 14 days or at least 1,2,3,4,5,6,7,8,9,10,11,12,13, or 14 days.

The process of the invention may be a process for culturing mammalian cells, the process comprising a first culture stage and a second culture stage, wherein the first culture stage is at or maintained at a first pH and the second culture stage is at or maintained at a second pH higher than the first pH. The first culture stage can comprise inoculating the mammalian cells into a culture medium at a first pH. The process may be a fed-batch process. The process may be one in which the temperature is maintained at a substantially constant value. The process may be one in which the mammalian cell is capable of expressing the antibody.

The process of the invention may comprise controlling the pH using a pH set point, the process comprising a first incubation period, wherein the set point is set to a first pH, and a second incubation period, wherein the set point is set to a second pH. The first culture stage can comprise inoculating the mammalian cells into a culture medium at a first pH. The first incubation period may have a particular duration as listed above, with the set point maintained at the first pH for that duration. The second incubation period may have a particular duration as listed above, wherein the set point is maintained at the second pH for that duration.

In the context of the present disclosure, "culturing cells" may refer to culturing cells at a particular pH for a particular duration. This may more specifically refer to culturing cells at a particular pH for a particular duration. This may refer to culturing cells using a particular pH set point for a particular duration. For example, reference to a second culture phase comprising "culturing cells at a second pH" can refer to culturing cells at the second pH for a particular duration of time using a set point set to the second pH.

The process of the present invention may comprise a pH shift up at or from day 6-8 (144-192 hours). The process of the invention may comprise a pH shift up on days 5-9 or days 4-10. The process may comprise a pH shift on day 4,5,6,7,8,9 or 10, or after day 4,5,6,7,8,9 or 10. When the mammalian cell is a CHO cell, the process may comprise a pH shift up at day 6 (144 hours), 156 hours, day 7 (168 hours), or day 8 (192 hours).

The optimal timing of the pH up shift can be determined in a series of preparative, experimental design, and processes. For example, the timing of the pH up shift can be selected to maximize the final product titer while maintaining the key product quality parameter within a desired range (e.g., maintaining the key quality attribute within a specific range specified by the FDA or EMEA in its kit of therapeutic products, see below). The timing of the pH up shift can be determined by measuring the final product titer in a series of preparative, experimental design, process to determine the timing of the pH up shift that yields the maximum product titer and a product quality profile suitable for clinical use. In such cases, product titer and quality can be measured in a series of preparative processes (which can be scaled-down versions of the process), where the timing of the pH up-shift is varied and selected to occur on the day of the process determined to provide a product quality profile that yields the maximum product titer and is suitable for clinical use. The product mass profile can be determined by measuring glycosylation, IEC patterns, electrophoresis patterns, mass spectrometry, chromatography, or caliper data.

For example, an approved product may require certain attributes for any or all of size-related variants, charge-related variants, trisulfide content, Fc glycosylation, microheterogeneity, glycation, action pattern-related biological functions, sequence variants, cell age-related product modifications, and process-related impurities.

Certain attributes may have the potential to affect product safety or efficacy and are thus classified as key quality attributes (CQAs) that should be controlled during production and storage. Manufacturing therapeutic proteins, such as therapeutic antibodies, is designed to control the desired level of CQA within defined limits to provide consistent product quality.

In the processes disclosed herein, variables such as timing of pH upshifts, appropriate total process duration, or time to harvest can be determined by the maximum final product titer and criteria for an acceptable product quality profile for clinical use.

The fed-batch process of the invention may comprise adding a feed medium to the culture. The feed medium may be added on days 1-3. The feed medium may be added on days 1-3,1-4,1-5, or 1-6. The feed medium is referred to as "feed 1" in the figure.

The fed-batch process of the invention may comprise adding a pH-up-shifting feed medium to the culture. The feed medium may be added at a pH of up-shift on days 4-14. The medium can be fed on day 4,5,6, or 7 of the process and added at pH on each subsequent day. The feed medium may be replaced with a pH-up feed medium from day 4,5,6, or 7 of the process. Feeding medium at pH-up in the figure is referred to as "feed 2". pH up-shifting the feed medium may prevent the pH of the cell culture medium from shifting down, for example by neutralizing acidic metabolites produced by the cells. Alternatively, pH shifting up the feed medium may increase the pH of the cell culture medium.

The fed-batch process of the invention may comprise supplementing the culture with a glucose solution on the day of adding the pH-shifted medium to the culture to maintain the appropriate glucose concentration.

The process of the invention may have a duration of at least 6 days, or at least 7,8,9,10,11,12,13,14,15,16,17 or 18 days. The total duration may be the duration from the day of inoculation (day 0) to the day of harvesting the cells and/or the products expressed by the cells. When the mammalian cells are CHO cells, the process may have a duration of 14 days. The total number of days of the process may also be referred to as "run time". The run time for the process can be selected for maximum product titer, or maximum product titer with a constant product quality profile. A product quality profile may be predefined for clinical use. The product mass profile can be determined by measuring glycosylation and/or Ion Exchange Chromatography (IEC) patterns.

The first culturing period may have a duration of 1-5,1-4 or 1-3 days. The pH up-shift may have a duration of about 10 or 30 minutes, or about 1,2,3,4,5,6,7,8,12,24,36,48,52, or 60 hours, or may have a duration of about 2-72,2-60,2-52,2-48,8-52,12-52,12-48,24-52, or 24-48 hours. The pH ramp-up may have a duration of at least about 10 or 30 minutes, or at least about 1,2,3,4,5,6,7,8,12,24,36,48,52, or 60 hours, or may have a duration of at least about 2-72,2-60,2-52,2-48,8-52,12-52,12-48,24-52, or 24-48 hours. The second culturing period may have a duration of about 4,5,6,7,8,9,10,11,12,13, or 14 days, or about 4-14,5-14,6-14,7-14, or 8-14 days.

The process may comprise a harvesting step. The cells and/or products are harvested in a harvesting step. The harvesting step terminates the process. The harvesting step may be on days 10-18, for example on day 14.

The timing of the harvesting step can be determined by measuring cell viability on a daily basis. The harvesting step may be performed on the first day of the process where cell viability is less than 85%, 80%, 75% or 70%.

The timing of the harvesting step in the process of the invention can be determined by measuring lactate accumulation in the control process. The control process is identical to the process of the invention, except that the first pH is maintained throughout the process (throughout both the first and second incubation periods). Lactate was measured daily in the control process. The harvesting step may be performed on days corresponding to the first day on which at least 4, at least 5, or at least 6 consecutive daily lactate increases are measured after in the second incubation period of the control process. Additional criteria may be applied such that the harvesting step may only be performed on days where no lactate elevation is measured in the process of the present invention relative to the previous day.

The timing of the harvesting step can be determined by measuring the product titer. The timing of the harvesting step can be determined by measuring the final product titer in a series of preparative, experimental design, process to determine the timing that yields the maximum product titer and a product quality profile suitable for clinical use. In such cases, product titer and quality can be measured daily in a preparative process (which can be a scaled-down version of the process of the invention, or can be the same as the process of the invention) and the harvesting step selected to occur on the day with the highest product titer and a product quality profile suitable for clinical use.

The timing of the harvesting step can be determined by measuring the product mass. Product quality can be measured in terms of glycosylation (e.g. galactosylation, high mannose structures) or in terms of in vitro or in vivo activity with a product after exceeding a threshold that is not optimal. In such cases, product quality may be measured daily in a preparative process (which may be a scaled-down version of the process of the invention, or may be the same as the process of the invention), and the harvesting step occurs on a day prior to the day in the preparative process on which the product quality is determined to be suboptimal.

The temperature of the process of the present invention can be maintained at a substantially constant value.

There is no significant temperature shift when the temperature is maintained at a substantially constant value. A significant temperature shift may be defined as a shift of about 0.5,1.0,1.5,2.0,3.0,4.0, or 5.0 ℃ or more. Substantially constant values may be within + -0.1 deg.C, + -0.2 deg.C, + -0.3 deg.C, + -0.4 deg.C, + -0.5 deg.C, + -1.0 deg.C, + -1.5 deg.C, or + -2.0 deg.C of the target value. The target value may be 35.0,35.5,36.0,36.5,37.0, or 37.5 ℃.

The temperature of the substantially constant value may be 36.0-37.0 ℃. That is, the temperature may be maintained between the values of 36.0 ℃ and 37.0 ℃. Similarly, the temperature of a substantially constant value may be 36.4-36.6 ℃. The temperature of the substantially constant value may be 36.5 ℃. The temperature may be measured using an in-line temperature sensor in the bioreactor.

Maintaining the temperature of the process at a substantially constant value may advantageously avoid problems caused by significant temperature shifts during the process. Lowering the temperature in the cell culture process used to produce recombinant proteins can cause changes in the quality of the unwanted product (e.g., changes in glycosylation) or can cause a loss in cellular productivity. Lowering the temperature may reduce the integral viable cell density, which is an indicator of cell productivity and therefore generally related to final product titer.

The mammalian cell may be a recombinant cell. The recombinant cell may comprise a nucleic acid sequence encoding a heterologous protein. The mammalian cell may be a CHO cell, more particularly a recombinant CHO cell. The mammalian cell may be CHO K1. The mammalian cell may be CHO K1 SV. The mammalian cell may be a BHK cell, more particularly a recombinant BHK cell. The mammalian cell may be a BHK-21 cell. C6 cells. The mammalian cells may be from a myeloma cell line. The mammalian cell may be a human cell line such as HEK293 and its derivatives and per. The mammalian cell may be capable of expressing the antibody. The mammalian cell may comprise a nucleic acid encoding an antibody. The nucleic acid encoding the antibody may be operably linked to a constitutive promoter or an inducible promoter. The antibody may be a multispecific antibody, antibody fragment with multispecific function, fused antibody, or fused antibody fragment. The antibody may be a monoclonal antibody. The antibody may be a therapeutic antibody. The antibody may be a bispecific antibody. The antibody may be a humanized antibody. The antibody may be anti-Ang 2/VEGF-CrossMab (Schaefer 2011; Fenn 2013).

The process can be a process for producing a product, wherein the product is expressed by a mammalian cell.

Expression systems, methods, and vectors for genetically engineering cells to express a protein of interest are well known to those skilled in the art, e.g., various techniques are described in Sambrook et al, Molecular Cloning: A L biology Manual 3ed. (2001). mammalian cells can be engineered to express products using the GS gene expression system (L onza Biologics plc, Slough UK).

The product may be a recombinant protein. The product may be an antibody. The antibody may be a multispecific antibody, antibody fragment with multispecific function, fused antibody, or fused antibody fragment. The antibody may be a monoclonal antibody. The antibody may be a therapeutic antibody. The antibody may be a bispecific antibody. The antibody can be a bivalent, bispecific antibody, such as a crossMAb antibody (Schaefer et al, 2011; Fenn et al, 2013). The antibody may be a biologically functional fragment of the antibody. Antibody fragments include Fab, Fab ', F (ab')₂scFv, dAb, Complementarity Determining Region (CDR) fragments, linear antibodies, single chain antibody molecules, minibodies (minibodies), diabodies (diabodies) and multispecific antibodies formed from antibody fragments.

The product may be an anti-Ang 2/VEGF-crossspmab antibody (Schaefer et al, 2011; Fenn et al, 2013). the product may be an anti-Ang 2/VEGF-crossspmab antibody with INN munuzumab (vanucizumab), or may be a heavy and light chain CDR amino acid sequence with the first and second antigen binding sites of anti-Ang CSF 2/VEGF-crossspmab described in WO2011/117329, or may be an antibody with the amino acid sequence of anti-Ang CSF 45/VEGF-crossspmab, or may be an antibody with the amino acid sequence of VH and V L domains, or an antibody with the amino acid sequence of anti-Ang CSF 2/VEGF-crossspmab described in WO2011/117329, or may be a heavy and light chain CDR amino acid sequence with the first and second antigen binding sites of anti-Ang CSF 8237/VEGF-crossspmab, or may be a heavy and light chain CDR amino acid sequence of anti-anzu-cd-CSF mab with the amino acid sequence of anti-Ang CSF 70/VEGF-crossspmab, or may be a heavy and heavy chain CDR amino acid sequence of anti-antibody with the amino acid sequence of anti-tnuzumab antibody with the amino acid sequence described in WO2011/117329, or anti-TNF-trastuzumab, or may be a heavy and anti-antibody with the amino acid sequence of anti-trastuzumab antibody with the sequence described in WO2011/117329, or anti-TNF-trastuzumab, or anti-antibody with the sequence described in WO-anti-trastuzumab process for the production process, or anti-TNF-anti-TNF-antibody with the sequence of the production process, or anti-antibody with the sequence of anti-antibody with the sequence of the antibody with the.

Therapeutic antibodies include, but are not limited to, anti-VEGF antibodies, anti-Ang 2 antibodies, anti-CSF-1R antibodies, anti-HER 2 antibodies, anti-CD 20 antibodies, anti-I L-8 antibodies, anti-CD 40 antibodies, anti-CD 11A antibodies, anti-CD 11b antibodies, anti-CD b antibodies, anti-lgE antibodies, anti-Apo-2 receptor antibodies, anti-Apo b:/TRAI b antibodies, anti-Tissue Factor (TF) antibodies, anti-human b 4b integrin antibodies, anti-EGFR antibodies, anti-CD b antibodies, anti-Fc receptor antibodies, anti-oncofetal antigen (CEA) antibodies, anti-mammary epithelial cell antibodies, anti-colon cancer antibody binding anti-CD b antibodies, anti-CD b antibody, anti-human-HCV anti-HCV antibody, anti-human-HCV antibody b antibody, anti-human-HCV antibody, anti-human-mouse antibody, anti-human-mouse antibody, anti-human mouse antibody, anti-mouse antibody, anti.

The product may be a protein, or an antibody, which is not Epo-Fc.

The process of the invention may further comprise the step of isolating the product or purifying the product. The step of isolating or purifying the product may comprise ion exchange chromatography. The step of isolating or purifying the product may comprise loading a composition comprising the product onto the ion exchange chromatography material, optionally washing the ion exchange chromatography material, and eluting the product from the ion exchange chromatography material. The product-containing composition may comprise culture medium from a cell culture, and/or may comprise mammalian cells, which may be lysed mammalian cells. The method of isolating or purifying the product may comprise the step of preparing a composition comprising the product. The step of preparing a composition comprising the product may comprise harvesting the cells, and/or lysing the cells, and/or harvesting the cell culture medium. The step of preparing a composition comprising the product may comprise protein a chromatography. The step of preparing the composition may comprise lyophilizing the product. The step of preparing the composition can comprise formulating the product in a pharmaceutically acceptable carrier (e.g., physiological saline) and/or in a solution comprising one or more pharmaceutical excipients.

The invention further provides products and compositions produced by the process of the invention.

The process of the invention avoids excessive accumulation of unwanted metabolites such as lactate and ammonium. The process of the invention can improve the maintenance of proper pCO₂Levels and/or lower osmolality of the culture.

The process of the invention may be a process having improved parameters relative to a control process, wherein the control process is the same as the process of the invention except that the first pH is maintained throughout the process (throughout both the first and second incubation periods). For example, the control process may be a process wherein the pH in the first incubation period is 7.00 and the pH in the second incubation period is 7.00.

The parameters may be measured at the harvesting step or on the day of the harvesting step. The parameters can be determined on day 14 when the mammalian cells are CHO cells.

The process of the invention may be one in which cell viability is at least 10%, 15% or 20% higher than the control process.

The process of the present invention may be a process wherein the lactate level is at least 10%, 20%, 30%, 40%, or 50% lower than the control process.

The process of the invention may be one in which the ammonium level is at least 10%, 20%, 30%, 40%, 50%, 60%, 70% or 80% lower than the control process.

The process of the invention may be one in which the product titer is at least 5%, 10% or 15% higher than the control process.

The process of the present invention may be a process in which the osmolality is at least 5% lower than in the control process. The process of the invention may be one in which the osmolality at the harvesting step is less than 500 Osm/kg.

As shown by examples 2 to 9 and the figure, the process of the present invention is improved compared to a process in which the pH is maintained at the same value throughout the process (as in example 1).

As shown by example 10 processes #1 and #2, the process of the present invention is also improved compared to a process comprising a downward shift in pH from the initial value, followed by an upward shift in pH towards the initial value. A process comprising a downward shift of the pH from an initial value followed by an upward shift of the pH towards the initial value is disclosed in US8,765,413.

The present invention further provides a method of extending the lifespan of a mammalian cell culture, the method comprising the process of the invention as described above. The present invention provides a method of increasing cell viability in mammalian cell culture, the method comprising the process of the invention as described above. The present invention provides a method of increasing Integrated Viable Cell Density (IVCD) in mammalian cell culture, the method comprising the process of the invention as described above. The present invention provides a method of reducing lactate accumulation in a mammalian cell culture, the method comprising the process of the invention as described above. The present invention provides a method of reducing ammonium accumulation in mammalian cell culture, the method comprising the process of the invention as described above. The invention provides an improved food feedpCO in milk animal cell culture₂The method of general outline, which comprises the process of the invention as described above. The present invention provides a method of reducing osmolality in a mammalian cell culture, the method comprising the process of the invention as disclosed above.

The present invention further provides a pH-up feeding medium or a pH-raising agent (e.g., an alkaline agent or a base) for extending the lifespan of a mammalian cell culture; increasing cell viability in mammalian cell culture; increasing IVCD in mammalian cell culture; reducing lactate accumulation in mammalian cell culture; reducing ammonium accumulation in mammalian cell culture; improvement of pCO in mammalian cell culture₂An overview; or reducing osmolality in a mammalian cell culture by performing the methods or processes of the invention as disclosed above. The process comprises adding a pH-raising medium or pH-raising agent to the mammalian cell culture to raise the pH from a first pH to a second pH. That is, in the case of the present invention which is the use of a pH-shifting medium or pH-raising agent for achieving a specific purpose, the use involves adding the pH-shifting medium or pH-raising agent to the culture medium of a mammalian cell culture to achieve a pH-shifting that occurs between the first and second culture stages. The invention further provides the use of a pH-up feeding medium or a pH-raising agent (e.g., an alkaline agent or a base) to increase product titer in a mammalian cell culture. For example, the present invention provides the use of a pH raising agent for increasing the titer of a product, wherein the product is expressed by a mammalian cell, e.g., a recombinant protein, such as an antibody, in a process for culturing mammalian cells disclosed herein. The increase in product titer is relative to a mammalian cell culture in which the pH raising agent is not added to the mammalian cell culture. The present invention provides the use of a pH raising agent for increasing the titer of a product in a process for producing a product (such as a recombinant protein product) disclosed herein. In a second aspect, the invention provides a process for culturing mammalian cells, the process comprising a first culturing stage comprising culturing the cells at a first pH, and a second culturing stage comprising culturing at a second pHA cell culture wherein the second pH is higher than the first pH and wherein the temperature of the process is maintained at a substantially constant value.

In a third aspect, the invention provides a process for culturing mammalian cells capable of expressing an antibody, the process comprising a first culture stage comprising inoculating the mammalian cells into a culture medium at a first pH and culturing the cells at the first pH, and a second culture stage comprising culturing the cells at a second pH higher than the first pH.

The second and third aspects of the invention may comprise any of the features of the process of the invention discussed above in relation to the first aspect of the invention.

Each and every compatible combination of the above-described embodiments is disclosed herein, as if each and every combination were individually and explicitly recited, except where such combinations are explicitly not allowed or explicitly avoided.

The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

Various other aspects and embodiments of the invention will be apparent to those skilled in the art in view of this disclosure.

Throughout this specification, including the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. "and/or" as used herein is to be understood as specifically disclosing each of the two specified features or ingredients, with or without the other. For example, "a and/or B" is to be understood as specifically disclosing each of (i) a, (ii) B and (iii) a and B, as if each were individually listed herein.

It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. For example, a pH of about 7.2 may be a pH of 7.2.

A pH value of "about" a certain value can be read in terms of the degree of accuracy with which it is expressed. For example, a pH of "about 7.0" may refer to a pH of 6.95-7.05, while a pH of "about 10" may refer to a pH of 9.5-10.5.

Relatively high pH values are relatively basic on the pH scale, while relatively low pH values are relatively acidic. As such, higher pH refers to a more basic pH in the context of this disclosure.

Unless the context indicates otherwise, the description and definitions of features listed above are not limited to any particular aspect or embodiment of the invention and apply equally to all aspects and embodiments described.

Certain aspects and embodiments of the present invention will now be illustrated by way of example and with reference to the figures described above. The examples should not be construed as limiting the scope of the invention. The examples are included for illustrative purposes and the invention is limited only by the claims. Other aspects and embodiments will be apparent to those skilled in the art. All documents mentioned herein are incorporated herein by reference.