U.S. patent application number 15/652138 was filed with the patent office on 2018-01-04 for methods for increasing mannose content of recombinant proteins.
This patent application is currently assigned to Amgen Inc.. The applicant listed for this patent is AMGEN INC.. Invention is credited to Michael Charles BRANDENSTEIN, Sean DAVERN, Shawn Erik LILLIE, Katherine Rose LINDAHL, Simina Crina PETROVAN, Jian WU.
Application Number | 20180002733 15/652138 |
Document ID | / |
Family ID | 50397323 |
Filed Date | 2018-01-04 |
United States Patent
Application |
20180002733 |
Kind Code |
A1 |
WU; Jian ; et al. |
January 4, 2018 |
METHODS FOR INCREASING MANNOSE CONTENT OF RECOMBINANT PROTEINS
Abstract
The present invention relates to methods of modulating the
mannose content of recombinant proteins.
Inventors: |
WU; Jian; (Acton, MA)
; DAVERN; Sean; (Seattle, WA) ; PETROVAN; Simina
Crina; (Wakefield, MA) ; BRANDENSTEIN; Michael
Charles; (Woodinville, WA) ; LINDAHL; Katherine
Rose; (Somerville, MA) ; LILLIE; Shawn Erik;
(Puyallup, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AMGEN INC. |
Thousand Oaks |
CA |
US |
|
|
Assignee: |
Amgen Inc.
Thousand Oaks
CA
|
Family ID: |
50397323 |
Appl. No.: |
15/652138 |
Filed: |
July 17, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14776404 |
Sep 14, 2015 |
9822388 |
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PCT/US2014/022738 |
Mar 10, 2014 |
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15652138 |
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61784639 |
Mar 14, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C12N 2500/34 20130101;
C12P 21/005 20130101; C07K 16/00 20130101; C12N 5/0037 20130101;
C07K 2317/41 20130101; C12N 2510/02 20130101; C12N 1/38 20130101;
C12N 2500/32 20130101; C07K 2317/14 20130101 |
International
Class: |
C12P 21/00 20060101
C12P021/00; C12N 1/38 20060101 C12N001/38; C07K 16/00 20060101
C07K016/00; C12N 5/00 20060101 C12N005/00 |
Claims
1. A method for modulating mannose 5 on a recombinant protein
during a mammalian cell culture process comprising limiting the
amount of glucose in the cell culture medium, wherein the
concentration of the glucose is from about 0 to 6 g/L, and
supplementing the cell culture medium with galactose or sucrose,
wherein the concentration of galactose is from 6-13 g/L or the
concentration of sucrose is from about 16-24 g/L.
2. The method according to claim 1, wherein the glucose
concentration in the cell culture medium is sufficient to result in
a concentration of glucose in the spent medium at about 0 g/L.
3. (canceled)
4. A method according the claim 1, wherein the concentration of
glucose in the cell culture medium is from 4 to 6 g/L.
5. The method according to claim 1, wherein the concentration of
glucose in the cell culture medium is from 1 to 3 g/L.
6. The method according to claim 1, wherein the concentration of
glucose in the cell culture medium is from 2 to 3 g/L.
7. The method according the claim 1, wherein the concentration of
glucose in the cell culture medium is 2.5 g/L.
8. The method according the claim 1, wherein the concentration of
glucose in the cell culture medium is 0 g/L.
9. (canceled)
10. The method according to claim 1, wherein the concentration of
galactose is from 10 to 13 g/L.
11. The method according to claim 1, wherein the concentration of
galactose in the cell culture medium is from 10 to 12 g/L.
12. The method according to claim 1, wherein the concentration of
galactose in the cell culture medium is 11.5 g/L.
13. (canceled)
14. (canceled)
15. The method according to claim 1, wherein the limiting amount of
glucose is added during a production phase.
16. (canceled)
17. The method according the claim 1, wherein the cell culture
process is a perfusion process.
18.-63. (canceled)
64. The method according to claim 1, wherein the mammalian cells
are Chinese Hamster Ovary (CHO) cells.
65. The method of claim 1, wherein the recombinant protein is
selected from the group consisting of a human antibody, a humanized
antibody, a chimeric antibody, a recombinant fusion protein, or a
cytokine.
66. The method according to claim 1, further comprising a step of
harvesting the recombinant protein produced by the cell
culture.
67. The method of claim 1, wherein the recombinant protein produced
by the cell culture is purified and formulated in a
pharmaceutically acceptable formulation.
68. The method of claim 1, wherein recombinant protein production
in the high mannose glycan species are increased compared to a
culture where the cells are not subjected to limited glucose in
combination with galactose.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/784,639 filed Mar. 14, 2013, which is
incorporated herein by reference in its entirety.
BACKGROUND OF INVENTION
[0002] IgG antibodies produced in mammalian cell cultures may
contain varied levels of high mannose (HM) glycoforms such as
Mannose5 (Man5), Mannose6 (Man6), Mannose7 (Man7), Mannose8 (Man8)
and Mannose9 (Man9). High mannose glycoform content of therapeutic
proteins and antibodies is a critical quality attribute that has
been found to affect pharmacokinetic properties of certain
therapeutic antibodies (Goetze, et al., (2011) Glycobiology 21,
949-59; Yu, et al., (2012) MAbs 4, 475-87).
[0003] Glycoforms of an antibody expressed by Chinese hamster ovary
(CHO) host cell are largely determined during cell line generation
and clone selection. However, HM content can also be affected by
cell culture conditions (Pacis, et al., (2011) Biotechnol Bioeng
108, 2348-2358). It is common in therapeutic antibody industry to
seek a desired range of HM content for an antibody product due to
process changes, scale-up, improvements or the need to match
existing antibody quality attributes. So far, methods applied for
manipulating HM content of an antibody in cell culture include
changes in media compositions, osmolality, pH, temperature, etc
(Yu, et al., supra, Pacis et al., supra, Chee Furng Wong et al.,
(2005) Biotechnol Bioeng 89, 164-177; Ahn, et al., (2008)
Biotechnol Bioeng 101, 1234-44). The effectiveness of these methods
is specific to cell lines, molecule types and media environment.
Additionally these methods tend to also alter antibody
productivity, cell culture behavior and other antibody quality
attributes. The effectiveness of these methods is obtained
empirically.
[0004] Therefore, there is a need for a method to modulate the high
mannose glycoform content of therapeutic proteins and antibodies.
The invention provides a method for increasing the high mannose
glycoform content through limited glucose in combination with an
alternative carbon source.
SUMMARY OF THE INVENTION
[0005] The invention provides a method for modulating one or more
high mannose glycan species on a recombinant protein during a
mammalian cell culture process comprising limiting the amount of
glucose in the cell culture medium and supplementing the cell
culture medium with galactose or sucrose.
[0006] In one embodiment the glucose concentration in the cell
culture medium is sufficient to result in a concentration of
glucose in the spent medium at or about 0 g/L.
[0007] In one embodiment the concentration of glucose in the cell
culture medium is from 0 to 8 g/L. In related embodiments the
concentration of glucose in the cell culture medium is from 4 to 6
g/L; 1 to 3 g/L; 2 to 3 g/L; 2.5 g/L or 0 g/L.
[0008] In one embodiment the concentration of galactose in the cell
culture medium is from 10 to 20 g/L. In related embodiments the
concentration of galactose is from 10 to 15 g/L; 10 to 12 g/L or
11.5 g/L.
[0009] In one embodiment the concentration of sucrose in the cell
culture medium is from 1 to 48 g/L. In a related embodiment the
concentration of sucrose in the cell culture medium is from 16 to
24 g/L.
[0010] In one embodiment the limiting amount of glucose is added
during a production phase.
[0011] In one embodiment the high mannose glycan species is mannose
5.
[0012] In one embodiment the cell culture process is a perfusion
process.
[0013] The invention also provides a method for modulating one or
more high mannose glycan species on a recombinant protein during
mammalian cell culture comprising; establishing a mammalian cell
culture in a bioreactor with a serum-free defined culture medium
containing 5-8 g/L glucose; growing the mammalian cells during a
growth phase and supplementing the culture medium with bolus feeds
of a serum-free defined feed medium having from 5-8 g/L glucose;
initiating a production phase in the cell culture by perfusion with
a serum-free perfusion medium having 5-15 g/L glucose; at a
predetermined time point, perfusing the cell culture with a low
glucose perfusion medium containing or supplemented with a
decreased amount of glucose, wherein said perfusion medium further
contains or is supplemented with galactose.
[0014] In one embodiment the decreased amount of glucose is
sufficient to result in a concentration of glucose in the spent
medium of at or about 0 g/L.
[0015] In one embodiment the concentration of the decreased amount
of glucose in the low glucose perfusion medium is from 0 to 3 g/L.
In related embodiments the concentration of the decreased amount of
glucose in the low glucose perfusion medium is from 2 to 3 g/L; 2.5
g/L or 0 g/L.
[0016] In one embodiment the concentration of galactose in the
perfusion medium is from 10 to 20 g/L. In related embodiments the
concentration of galactose in the low glucose perfusion medium is
from 10 to 15 g/L; 10 to 12 g/L or 11.5 g/L.
[0017] In one embodiment perfusion begins on or about day 5 to on
or about day 9 of the cell culture. In a related embodiment
perfusion begins on or about day 5 to on or about day 7 of the cell
culture. In another related embodiment perfusion begins when the
cells have reached a production phase.
[0018] In another embodiment perfusion comprises continuous
perfusion. In a related embodiment the rate of perfusion is
constant.
[0019] In one embodiment perfusion is performed at a rate of less
than or equal to 1.0 working volumes per day. In a related
embodiment perfusion is performed at a rate that increases during
the production phase from 0.25 working volume per day to 1.0
working volume per day during the cell culture. In another related
embodiment perfusion is performed at a rate that reaches 1.0
working volume per day on day 9 to day 11 of the cell culture. In
another related embodiment perfusion is performed at a rate that
reaches 1.0 working volume per day on day 10 of the cell
culture.
[0020] In one embodiment the bolus feeds of serum-free feed medium
begin on day 3 or day 4 of the cell culture.
[0021] In one embodiment the mammalian cell culture is established
by inoculating the bioreactor with at least 0.5.times.10.sup.6 to
3.0.times.10.sup.6 cells/mL in a serum-free culture medium.
[0022] In a related embodiment the mammalian cell culture is
established by inoculating the bioreactor with at least
0.5.times.10.sup.6 to 1.5.times.10.sup.6 cells/mL in a serum-free
culture medium.
[0023] In one embodiment the high mannose glycan species is Mannose
5.
[0024] In one embodiment the method described above further
comprises temperature shift from 36.degree. C. to 31.degree. C.
[0025] In one embodiment the method described above further
comprises a temperature shift from 36.degree. C. to 33.degree. C.
In a related embodiment the temperature shift occurs at the
transition between the growth phase and production phase. In a
related embodiment the temperature shift occurs during the
production phase.
[0026] In one embodiment the method above further comprising
inducing cell growth-arrest by L-asparagine starvation followed by
perfusion with a serum-free perfusion medium having an L-asparagine
concentration of 5 mM or less. In a related embodiment the
concentration of L-asparagine in the serum-free perfusion medium is
less than or equal to 5 mM. In a related embodiment the
concentration of L-asparagine in the serum-free perfusion medium is
less than or equal to 4.0 mM. In another related embodiment the
concentration of L-asparagine in the serum-free perfusion medium is
less than or equal to 3.0 mM. In another related embodiment the
concentration of L-asparagine in the serum-free perfusion medium is
less than or equal to 2.0 mM. In another related embodiment the
concentration of L-asparagine in the serum-free perfusion medium is
less than or equal to 1.0 mM. In yet another related embodiment the
concentration of L-asparagine in the serum-free perfusion medium is
0 mM. In yet another related embodiment the L-asparagine
concentration of the cell culture medium is monitored prior to and
during L-asparagine starvation.
[0027] In one embodiment the method above, further comprises that
the packed cell volume during a production phase is less than or
equal to 35%. In a related embodiment the packed cell volume is
less than or equal to 35%. In a related embodiment the packed cell
volume is less than or equal to 30%.
[0028] In one embodiment the viable cell density of the mammalian
cell culture at a packed cell volume less than or equal to 35% is
10.times.10.sup.6 viable cells/ml to 80.times.10.sup.6 viable
cells/ml. In a related embodiment the viable cell density of the
mammalian cell culture is 20.times.10.sup.6 viable cells/ml to
30.times.10.sup.6 viable cells/ml.
[0029] In one embodiment the perfusion is accomplished by
alternating tangential flow.
[0030] In a related embodiment the perfusion is accomplished by
alternating tangential flow using an ultrafilter or a
microfilter.
[0031] In one embodiment the bioreactor has a capacity of at least
500L. In a related embodiment the bioreactor has a capacity of at
least 500L to 2000L. In a related embodiment the bioreactor has a
capacity of at least 1000L to 2000L.
[0032] In one embodiment the mammalian cells are Chinese Hamster
Ovary (CHO) cells.
[0033] In one embodiment the recombinant protein is selected from
the group consisting of a human antibody, a humanized antibody, a
chimeric antibody, a recombinant fusion protein, or a cytokine.
[0034] In one embodiment the method above further comprises a step
of harvesting the recombinant protein produced by the cell
culture.
[0035] In one embodiment the recombinant protein produced by the
cell culture is purified and formulated in a pharmaceutically
acceptable formulation.
[0036] In one embodiment the recombinant protein production in the
high mannose glycan species are increased compared to a culture
where the cells are not subjected to limited glucose in combination
with galactose.
[0037] In one embodiment the concentration of the perfusion medium
is 15 g/L.
BRIEF DESCRIPTION OF THE FIGURES
[0038] FIGS. 1A-1F. Cell culture and Man5 profiles in a fed-batch
process. FIG. 1A: Glucose concentration g/L in culture supernatant.
FIG. 1B: Galactose concentration g/L in culture supernatant. FIG.
1C: Viable Cell Density. FIG. 1D: Viability. FIG. 1E: Titer. FIG.
1F: Man5. Glucose 1 g/L, galactose 0 g/L (open triangle). Glucose 1
g/L, galactose 4 g/L (solid triangle). Glucose 2 g/L, galactose 0
g/L (open circle). Glucose 2 g/L, galactose 4 g/L (solid triangle).
Glucose 3 g/L, galactose 0 g/L (open square). Glucose 3 g/L,
galactose 4 g/L (solid square).
[0039] FIGS. 2A-2F. Cell culture and amino acid profiles in
perfusion process. FIG. 2A: Viable Cell Density FIG. 2B: Viability,
FIG. 2C: Gln (glutamine) concentration g/L in spent media analysis,
FIG. 2D: Packed Cell Volume Adjusted Titer, FIG. 2E: Glc (glucose)
concentration g/L in spent media analysis, FIG. 2F: galactose
concentration g/L in spent media analysis. Glucose 2 g/L, galactose
6 g/L and glutamine 10 mM (solid triangle). Glucose 4 g/L,
galactose 6 g/L and glutamine 10 mM (solid circle). Glucose 4 g/L,
galactose 6 g/L and glutamine 5 mM (open circle).
[0040] FIGS. 3A-3G. Cell culture profiles in perfusion process.
FIG. 3A: Glu (glucose) concentration g/L in spent media analysis,
FIG. 3B: Gal (galactose) concentration g/L in spent media analysis,
FIG. 3C: Lactate concentration, FIG. 3D: Ammonia concentration FIG.
3E: Viable cell density, FIG. 3F: Viability, FIG. 3G: Packed cell
volume adjusted titer. Glucose 3 g/L, galactose 13 g/L (solid
square). Glucose 0 g/L, galactose 10 g/L (open circle). Glucose 0
g/L, galactose 13 g/L (solid circle). Glucose 1.5 g/L, galactose
11.5 g/L (star). Glucose 3 g/L, galactose 10 g/L, (open
square).
[0041] FIGS. 4A-4B. JMP statistical analysis of perfusion process.
FIG. 4A: Packed Cell Volume Adjusted Titer, FIG. 3B: Man5.
[0042] FIG. 5. Time course data showing increase in percent of Man5
species. - 0 g/L glucose 10 g/L galactose; -+0 g/L glucose 13 g/L
galactose; +13 g/L glucose 10 g/L galactose; ++3 g/L glucose 13 g/L
galactose; OO 1.5 g/L glucose 11.5 galactose.
[0043] FIGS. 6A-6G. Cell culture profiles in perfusion process.
FIG. 6A: Glu (glucose) concentration g/L in spent media analysis,
FIG. 6B: Sucrose concentration g/L in spent media analysis, FIG.
6C: Viable Cell Density, FIG. 6D: Lactate concentration g/L, FIG.
6E: Ammonium concentration mM, FIG. 6F: Viability, FIG. 6G: Packed
Cell Volume Adjusted titer. Glucose 6 g/L, sucrose 24 g/L (solid
square). Glucose 2 g/L, sucrose 16 g/L (open square). Glucose 2
g/L, sucrose 24 g/L (solid circle). Glucose 4 g/L, sucrose 20 g/L
(star). Glucose 2 g/L, sucrose 16 g/L (open circle).
[0044] FIGS. 7A-7B. JMP statistical analysis of perfusion process.
FIG. 7A: Packed Cell Volume Adjusted Titer, FIG. 7B: Man5, FIG. 7C:
Viability.
DETAILED DESCRIPTION OF THE INVENTION
[0045] Production of consistent and reproducible recombinant
glycoprotein glycoform profiles remains a considerable challenge to
the biopharmaceutical industry. Variations in cell culture
processes play a significant role in antibody glycosylation
profiles. Potential variability in the cell culture process
physicochemical environment including pH, temperature, cell culture
media composition, raw material lot-to-lot variation, medium
filtration material, bioreactor scale difference, gassing strategy
(air, oxygen, carbon dioxide) are just a few examples that can
potentially alter glycosylation profiles.
[0046] It was observed that under conditions of low or limited
glucose, the high mannose glycoform content of the recombinant
protein increased, however, attributes of the cell culture, such as
volumetric productivity, cell viability, and/or density,
diminished. Increasing the glucose concentration improved the
culture attributes, but decreased the high mannose glycoform
content.
[0047] The invention provides a method for increasing high mannose
glycoforms, in particular, Mannose5 (Man5), to achieve desired
product quality attributes while maintaining desirable levels of
certain cell culture parameters such as volumetric productivity,
cell viability, and/or density, through the use of low or limited
concentrations of glucose in combination with an alternate carbon
source, in particular, galactose or sucrose. As described herein,
culturing cells in a cell culture medium where glucose is limited
by lowering the concentration of glucose in the cell culture
medium, in combination with an alternative carbon source, resulted
in a recombinant protein having am increased concentration of high
mannose glucoforms, while maintaining cell growth, viability and
titer at acceptable levels.
[0048] During the production phase of a cell culture, desirable
culture parameters, such as viable cell density, cell viability,
percent packed cell volume, titer and/or packed cell volume
adjusted titer can be established by feeding the cell culture a
cell culture medium containing sufficient glucose (from 5 g/L to 15
g/L or more) to establish and maintain these parameters. At such
time during the cell culture production run, when it is desirable
to increase the high mannose glycoform content of the recombinant
protein being produced, the cell culture is then fed with a cell
culture medium wherein the concentration of glucose is reduced such
that will result in the desired increase in high mannose content.
Such a cell culture medium is characterized by a lower
concentration of glucose (0-8 g/L) in combination an alternative
carbon source, such as galactose or sucrose.
[0049] Factors that determine the degree to which the glucose
concentration will need to be lowered include which alternate
carbon source used and how much is used; the cell culture
production process; the cell type and mass and the glucose
consumption. The greater the cell mass in the bioreactor, the
greater the glucose consumption by the cell culture and hence the
greater the amount of glucose that can be fed while still
maintaining a limited glucose state that will produce the desired
increase Man5 glycoform concentration. The manner in which the
glucose is fed to the cell culture can also influence the amount of
glucose necessary to maintain a limited glucose state that will
produce the desired increase Man5 glycoform concentration. For
example, in a fed-batch cell culture, glucose can be formulated
into the cell culture medium and supplemented by bolus feeds. In a
perfusion cell culture process, glucose concentration will depend
on the feed rate (g/L/day) of the perfusion medium. Examples of
both are provided herein. In addition, the amount of glucose in the
culture medium during production can be measured, such as by spent
media analysis for perfusion cultures. It was observed that Man5
levels increased when the amount of glucose in the spent medium was
at or nearly 0 g/L.
[0050] High mannose glycoform production was increased when
situations where glucose concentrations were decreased. However,
low levels of glucose can impact the production of recombinant
proteins in cell culture systems. Volumetric production, cell
viability and viable cell density can all be negatively impacted in
situations when glucose is limited. It was found that the addition
of an alternate carbon source, such as galactose, to cell culture
during a period of low or limited glucose was not slowed or
stabilized the decreases in volumetric production, cell viability
and viable cell density, while preserving the increased Man5
glycoforms. Alternatively, during a period of low or limited
glucose, sucrose was also able to promote high mannose glycoform
production, freeing some glucose to maintain volumetric production,
cell viability and viable cell density. While cells could consume
galactose, they did not consume sucrose in a limited glucose
situation. It is believed that sucrose has an osmolality-related
effect on cell metabolism and glycosylation of the molecule. Having
the ability to manipulate and maintain the high mannose glycoform
content of a recombinant protein during cell culture while
minimizing product titer loss and maintaining cell viability
represents a valuable and easily-implemented method for commercial
therapeutic protein production.
[0051] Provided herein is a method of culturing mammalian cells
that is useful for increasing high mannose glycoforms, in
particular, Man 5, to achieve desired product quality attributes
while maintaining acceptable product titer and cell viability by
making use of a limiting amount of glucose in combination with an
alternate carbon source, in particular, galactose or sucrose. The
method provides culturing mammalian cells during growth and/or
production phases in a cell culture medium having a high,
non-limiting glucose concentration, from 5 to 15 g/L glucose,
either compounded into the medium formulation, supplemented through
bolus or continuous feeds or both. When viable cell density, cell
viability and/or titer reach desired levels, the amount of glucose
in the cell culture medium is lowered to a limiting amount, such
that in the perfusion medium feed for example, the amount of
glucose measured in spent medium is at or just above 0 g/L. The
rate of glucose consumption is determined by the rate of glucose
addition and/or the mass of the cell culture. Glucose can be fed at
up to 8 g/L. In one embodiment, glucose is fed up to 6 g/L. In
another embodiment glucose is fed up to 4 g/L. In another
embodiment, glucose is fed up to 3 g/L. In another embodiment
glucose is fed up to 2-3 g/L. In yet another embodiment glucose is
fed up to 2.5 g/L. In another embodiment, glucose is 0 g/L.
[0052] In combination with the lowered glucose concentration, the
cell culture medium contains or is supplemented with galactose, at
a concentration up to 20 g/L. In one embodiment the concentration
of galactose is from 10 to 15 g/L. In another embodiment the
concentration of galactose is 11.5 g/L.
[0053] In another embodiment, in combination with the lowered
glucose concentration, the cell culture medium contains or is
supplemented with sucrose, at a concentration up to 48 g/L. In one
embodiment the concentration of sucrose is 16 to 24 g/L.
[0054] Carbohydrate moieties are described herein with reference to
commonly used nomenclature for oligosaccharides. A review of
carbohydrate chemistry which uses this nomenclature can be found,
for example, in Hubbard and Ivatt, Ann. Rev. Biochem. 50:555-583
(1981). This nomenclature includes, for instance, Man, which
represents mannose; Gal which represents galactose; and Glc, which
represents glucose.
[0055] By "cell culture" or "culture" is meant the growth and
propagation of cells outside of a multicellular organism or tissue.
Suitable culture conditions for mammalian cells are known in the
art. See e.g. Animal cell culture: A Practical Approach, D.
Rickwood, ed., Oxford University Press, New York (1992). Mammalian
cells may be cultured in suspension or while attached to a solid
substrate. Fluidized bed bioreactors, hollow fiber bioreactors,
roller bottles, shake flasks, or stirred tank bioreactors, with or
without microcarriers, can be used.
[0056] The mammalian cell culture is grown in a bioreactor. In one
embodiment 500L to 20000L bioreactors are used. In a preferred
embodiment, 1000L to 2000L bioreactors are used.
[0057] The bioreactor is inoculated with at least
0.5.times.10.sup.6 up to and beyond 3.0.times.10.sup.6 viable
cells/mL in a serum-free culture medium. In a preferred embodiment
the inoculation is 1.0.times.10.sup.6 viable cells/mL.
[0058] Once inoculated into the production bioreactor the mammalian
cells undergo an exponential growth phase. The growth phase can be
maintained using a fed-batch process with bolus feeds of a
serum-free feed medium having from 5 to 8 g/L glucose. These
supplemental bolus feeds typically begin shortly after the cells
are inoculated into the bioreactor, at a time when it is
anticipated or determined that the cell culture needs feeding. For
example, supplemental feeds can begin on or about day 3 or 4 of the
culture or a day or two earlier or later. The culture may receive
two, three, or more bolus feeds during the growth phase. Neither
the basal cell culture medium nor the bolus feed medium contain
galactose or sucrose.
[0059] When the cells enter the stationary or production phase, or
the cell culture has achieved a desired viable cell density and/or
cell titer, the fed batch bolus feeds are discontinued and
perfusion is started. Perfusion culture is one in which the cell
culture receives fresh perfusion feed medium while simultaneously
removing spent medium. Perfusion can be continuous, step-wise,
intermittent, or a combination of any or all of any of these.
Perfusion rates can be less than a working volume to many working
volumes per day. Preferably the cells are retained in the culture
and the spent medium that is removed is substantially free of cells
or has significantly fewer cells than the culture. Perfusion can be
accomplished by a number of means including centrifugation,
sedimentation, or filtration, See e.g. Voisard et al., (2003),
Biotechnology and Bioengineering 82:751-65. A preferred filtration
method is alternating tangential flow filtration. Alternating
tangential flow is maintained by pumping medium through
hollow-fiber filter modules. See e.g. U.S. Pat. No. 6,544,424. The
hollow-fiber modules can be microfilters or ultrafilters.
[0060] When the fed-batch culture reaches a predetermined trigger
point, such as desired cell viability, cell density, percent packed
cell volume, titer, packed cell volume adjusted titer, age or the
like, a switch between fed-batch and perfusion can take place. For
example, this switch can take place on or about day 7 of the
culture, but may take place a day or two earlier or later. The
perfusion feed formulation contains glucose at a concentration of
up to 15 g/L or more, but does not contain galactose or sucrose. In
one embodiment, the perfusion medium contains 15 g/L glucose.
[0061] When the perfusion culture reaches a predetermined trigger
point, such as desired cell viability, cell density, percent packed
cell volume, titer, packed cell volume adjusted titer, age or the
like, the glucose concentration in the cell culture medium is
lowered. For example, this shift may be initiated on day 11 of the
culture, but may take place a day or two earlier or later. At that
time the cell culture is perfused with cell culture medium
containing a lower concentration of glucose. Such a lower
concentration of glucose will result in a lower concentration of
glucose measured in the spent media of at or nearly 0 g/L. Glucose
can be feed at up to 8 g/L. In one embodiment, glucose is fed up to
6 g/L. In another embodiment glucose is fed up to 4 g/L. In another
embodiment, glucose is fed up to 3 g/L. In another embodiment
glucose is 2-3 g/L. In yet another embodiment, glucose is 2.5 g/L.
In another embodiment, glucose is 0 g/L.
[0062] The limited glucose state in the cell culture is maintained
by monitoring the concentration of glucose in the cell culture,
such as by measuring glucose concentration in the spent medium, and
adjusting the glucose concentration in the perfusion medium
formulation to maintain a level of at or nearly 0 g/L in the spent
medium.
[0063] The cell culture medium containing the lower concentration
of glucose may also be supplemented with galactose at a
concentration of up to 20 g/L. In one embodiment the concentration
of galactose is from 10 to 15 g/L. In another embodiment the
concentration of galactose is 11.5 g/L.
[0064] Alternatively, the lower glucose cell culture medium may be
supplemented with sucrose at a concentration of 1 to 48 g/L. In one
embodiment the sucrose concentration is 16 to 24 g/L.
[0065] The cell culture can be continuously maintained in a limited
glucose state supplemented with galactose or sucrose. The cell
culture can be maintained in a limited glucose state supplemented
with galactose or sucrose until harvest. The cell culture can be
restored to a non-glucose limited state without galactose or
sucrose supplements and the entire process begun again.
[0066] The cell culture could also be maintained in a perfusion
culture system for both the growth and production phases. Once
inoculated into the production bioreactor the mammalian cells
undergo an exponential growth phase during which time the cell
culture is perfused with serum-free and/or chemically defined cell
culture medium supplemented with 5 to 15 g/L glucose. The cell
culture medium does not contain galactose or sucrose. The culture
is maintained until a desired trigger point is achieved, for
example desired viable cell density, cell viability, percent packed
cell volume, titer, packed cell adjusted volume titer, age or the
like. At that time the cell culture is perfused with a cell culture
medium containing a limiting concentration of glucose. Such a
limiting concentration of glucose will result in a concentration of
glucose in the spent media of at or nearly 0 g/L glucose. Glucose
can be feed at up to 8 g/L. In one embodiment, glucose is fed up to
6 g/L. In another embodiment glucose is fed up to 4 g/L. In another
embodiment, glucose is fed up to 3 g/L. In another embodiment
glucose is 2-3 g/L. In yet another embodiment, glucose is 2.5 g/L.
In another embodiment, glucose is 0 g/L.
[0067] The cell culture medium containing the limiting amount of
glucose may also contain galactose at a concentration of up to 20
g/L. In one embodiment the concentration of galactose is from 10 to
15 g/L. In another embodiment the concentration of galactose is
11.5 g/L.
[0068] Alternatively, the cell culture medium containing the
limiting amount of glucose may contain sucrose at a concentration
from 1 to 48 g/L. One embodiment of the sucrose concentration is 16
to 24 g/L.
[0069] In addition, the cell culture medium containing the limiting
amount of glucose may also contain glutamine in addition to
galactose or sucrose. Glutamine is at a concentration of 1 to 20 mM
in combination with either galactose or sucrose. In one embodiment
the concentration of glutamine is from 5 to 10 mM.
[0070] Viable cell density may be a signal for transition to the
production phase or to lower the glucose concentration in the cell
culture medium. It may also be desirable to maintain a certain
range or level of viable cell density during the production phase.
In one embodiment the viable cell density is 10.times.10.sup.6
viable cells/mL to at least about 60.times.10.sup.6 viable
cells/mL. In another embodiment the viable cell density is
10.times.10.sup.6 viable cells/mL to 50.times.10.sup.6 viable
cells/mL. In another embodiment the viable cell density is
10.times.10.sup.6 viable cells/mL to 40.times.10.sup.6 viable
cells/mL. In a preferred embodiment the viable cell density is
10.times.10.sup.6 viable cells/mL to 30.times.10.sup.6 viable
cells/mL. In another preferred embodiment the viable cell density
is 10.times.10.sup.6 viable cells/mL to 20.times.10.sup.6 viable
cells/mL. In another preferred embodiment the viable cell density
is 20.times.10.sup.6 viable cells/mL to 30.times.10.sup.6 viable
cells/mL. In yet another preferred embodiment the viable cell
density is 20.times.10.sup.6 viable cells/mL to 25.times.10.sup.6
viable cells/mL. In an even more preferred embodiment the viable
cell density is at least about 20.times.10.sup.6 viable
cells/mL.
[0071] The percent packed cell volume (% PCV) may also be used as a
signal for transition to the production phase or to begin feeding
the cell culture with a cell culture medium containing a limiting
amount of glucose. The cell culture may also be maintained at a
desired packed cell volume during the production phase. In one
embodiment the packed cell volume is equal to or less than 30%. In
a preferred embodiment the packed cell volume is at least about
15-30%. In a preferred embodiment the packed cell volume is at
least about 20-25%. In another preferred embodiment the packed cell
volume is equal to or less than 25%. In another preferred
embodiment the packed cell volume is equal to or less than 15%. In
another preferred embodiment the packed cell volume is equal to or
less than 20%. In yet another preferred embodiment the packed cell
volume is equal to or less than 15%.
[0072] A perfusion cell culture medium having a reduced
concentration of asparagine can be used to arrest cell growth while
maintaining productivity and viability during the production phase.
In a preferred embodiment the concentration of asparagine is at
least about 0 mM to at least about 5 mM asparagine, see WIPO
Publication No. WO 2013/006479.
[0073] As used herein, "perfusion flow rate" is the amount of media
that is passed through (added and removed) from a bioreactor,
typically expressed as some portion or multiple of the working
volume, in a given time. "Working volume" refers to the amount of
bioreactor volume used for cell culture. In one embodiment the
perfusion flow rate is one working volume or less per day.
Perfusion feed medium can be formulated to maximize perfusion
nutrient concentration to minimize perfusion rate.
[0074] As used herein, "cell density" refers to the number of cells
in a given volume of culture medium. "Viable cell density" refers
to the number of live cells in a given volume of culture medium, as
determined by standard viability assays (such as trypan blue dye
exclusion method).
[0075] As used herein, "packed cell volume" (PCV), also referred to
as "percent packed cell volume" (% PCV), is the ratio of the volume
occupied by the cells, to the total volume of cell culture,
expressed as a percentage (see Stettler, wt al., (2006) Biotechnol
Bioeng. December 20:95(6): 1228-33). Packed cell volume is a
function of cell density and cell diameter; increases in packed
cell volume could arise from increases in either cell density or
cell diameter or both. Packed cell volume is a measure of the solid
content in the cell culture. Solids are removed during harvest and
downstream purification. More solids mean more effort to separate
the solid material from the desired product during harvest and
downstream purification steps. Also, the desired product can become
trapped in the solids and lost during the harvest process,
resulting in a decreased product yield. Since host cells vary in
size and cell cultures also contain dead and dying cells and other
cellular debris, packed cell volume is a more accurate way to
describe the solid content within a cell culture than cell density
or viable cell density.
[0076] For the purposes of this invention, cell culture medium is a
medium suitable for growth of animal cells, such as mammalian
cells, in in vitro cell culture. Cell culture media formulations
are well known in the art. Typically, cell culture media are
comprised of buffers, salts, carbohydrates, amino acids, vitamins
and trace essential elements. "Serum-free" applies to a cell
culture medium that does not contain animal sera, such as fetal
bovine serum. Various tissue culture media, including defined
culture media, are commercially available, for example, any one or
a combination of the following cell culture media can be used:
RPMI-1640 Medium, RPMI-1641 Medium, Dulbecco's Modified Eagle's
Medium (DMEM), Minimum Essential Medium Eagle, F-12K Medium, Ham's
F12 Medium, Iscove's Modified Dulbecco's Medium, McCoy's 5A Medium,
Leibovitz's L-15 Medium, and serum-free media such as EX-CELL.TM.
300 Series (JRH Biosciences, Lenexa, Kans.), among others.
Serum-free versions of such culture media are also available. Cell
culture media may be supplemented with additional or increased
concentrations of components such as amino acids, salts, sugars,
vitamins, hormones, growth factors, buffers, antibiotics, lipids,
trace elements and the like, depending on the requirements of the
cells to be cultured and/or the desired cell culture
parameters.
[0077] Cell culture media may be serum-free, protein-free, and/or
peptone-free. "Serum-free" applies to a cell culture medium that
does not contain animal sera, such as fetal bovine serum.
"Protein-free" applies to cell culture media free from exogenously
added protein, such as transferrin, protein growth factors IGF-1,
or insulin. Protein-free media may or may not contain peptones.
"Peptone-free" applies to cell culture media which contains no
exogenous protein hydrolysates such as animal and/or plant protein
hydrolysates. Cell culture broth or like terminology refers to the
cell culture media that contains, among other things, viable and
non-viable mammalian cells, cell metabolites and cellular debris
such as nucleic acids, proteins and liposomes.
[0078] Cell cultures can also be supplemented with concentrated
feed medium containing components, such as nutrients and amino
acids, which are consumed during the course of the production phase
of the cell culture. Concentrated feed medium may be based on just
about any cell culture media formulation. Such a concentrated feed
medium can contain anywhere from a single or nearly almost all of
the components of the cell culture medium at, for example, about
5.times., 6.times., 7.times., 8.times., 9.times., 10.times.,
12.times., 14.times., 16.times., 20.times., 30.times., 50.times.,
100.times., 200.times., 400.times., 600.times., 800.times., or even
about 1000.times. of their normal amount, see for example WIPO
Publication No WO2012/145682.
[0079] The method according to the present invention may be used to
improve the production of recombinant proteins in multiple phase
culture processes. In a multiple stage process, cells are cultured
in two or more distinct phases. For example cells may be cultured
first in one or more growth phases, under environmental conditions
that maximize cell proliferation and viability, then transferred to
a production phase, under conditions that maximize protein
production. In a commercial process for production of a protein by
mammalian cells, there are commonly multiple, for example, at least
about 2, 3, 4, 5, 6, 7, 8, 9, or 10 growth phases that occur in
different culture vessels preceding a final production culture. The
growth and production phases may be preceded by, or separated by,
one or more transition phases. In multiple phase processes, the
method according to the present invention can be employed at least
during the growth and production phase of the final production
phase of a commercial cell culture, although it may also be
employed in a preceding growth phase. A production phase can be
conducted at large scale. A large scale process can be conducted in
a volume of at least about 100, 500, 1000, 2000, 3000, 5000, 7000,
8000, 10,000, 15,000, 20,000 liters. In a preferred embodiment
production is conducted in 500L, 1000L and/or 2000L bioreactors. A
growth phase may occur at a higher temperature than a production
phase. For example, a growth phase may occur at a first temperature
from about 35.degree. C. to about 38.degree. C., and a production
phase may occur at a second temperature from about 29.degree. C. to
about 37.degree. C., optionally from about 30.degree. C. to about
36.degree. C. or from about 30.degree. C. to about 34.degree. C. In
addition, chemical inducers of protein production, such as, for
example, caffeine, butyrate, and hexamethylene bisacetamide (HMBA),
may be added at the same time as, before, and/or after a
temperature shift. If inducers are added after a temperature shift,
they can be added from one hour to five days after the temperature
shift, optionally from one to two days after the temperature shift.
The cell cultures can be maintained for days or even weeks while
the cells produce the desired protein(s).
[0080] Typically the cell cultures that precede the final
production culture (N-x to N-1) are used to generate the seed cells
that will be used to inoculate the production bioreactor, the N-1
culture. The seed cell density can have a positive impact on the
level of recombinant protein produced. Product levels tend to
increase with increasing seed density. Improvement in titer is tied
not only to higher seed density, but is likely to be influenced by
the metabolic and cell cycle state of the cells that are placed
into production.
[0081] Seed cells can be produced by any culture method. A
preferred method is a perfusion culture using alternating
tangential flow filtration. An N-1 bioreactor can be run using
alternating tangential flow filtration to provide cells at high
density to inoculate a production bioreactor. The N-1 stage may be
used to grow cells to densities of >90.times.10.sup.6 cells/mL.
The N-1 bioreactor can be used to generate bolus seed cultures or
can be used as a rolling seed stock culture that could be
maintained to seed multiple production bioreactors at high seed
cell density. The duration of the growth stage of production can
range from 7 to 14 days and can be designed so as to maintain cells
in exponential growth prior to inoculation of the production
bioreactor. Perfusion rates, medium formulation and timing are
optimized to grow cells and deliver them to the production
bioreactor in a state that is most conducive to optimizing their
production. Seed cell densities of >15.times.10.sup.6 cells/mL
can be achieved for seeding production bioreactors.
[0082] The cell lines (also referred to as "host cells") used in
the invention are genetically engineered to express a polypeptide
of commercial or scientific interest. Cell lines are typically
derived from a lineage arising from a primary culture that can be
maintained in culture for an unlimited time. Genetically
engineering the cell line involves transfecting, transforming or
transducing the cells with a recombinant polynucleotide molecule,
and/or otherwise altering (e.g., by homologous recombination and
gene activation or fusion of a recombinant cell with a
non-recombinant cell) so as to cause the host cell to express a
desired recombinant polypeptide. Methods and vectors for
genetically engineering cells and/or cell lines to express a
polypeptide of interest are well known to those of skill in the
art; for example, various techniques are illustrated in Current
Protocols in Molecular Biology, Ausubel et al., eds. (Wiley &
Sons, New York, 1988, and quarterly updates); Sambrook et al.,
Molecular Cloning: A Laboratory Manual (Cold Spring Laboratory
Press, 1989); Kaufman, R. J., Large Scale Mammalian Cell Culture,
1990, pp. 15-69.
[0083] Animal cell lines are derived from cells whose progenitors
were derived from a multi-cellular animal. One type of animal cell
line is a mammalian cell line. A wide variety of mammalian cell
lines suitable for growth in culture are available from the
American Type Culture Collection (Manassas, Va.) and commercial
vendors. Examples of cell lines commonly used in the industry
include VERO, BHK, HeLa, CV1 (including Cos), MDCK, 293, 3T3,
myeloma cell lines (e.g., NS0, NS1), PC12, WI38 cells, and Chinese
hamster ovary (CHO) cells. CHO cells are widely used for the
production of complex recombinant proteins, e.g. cytokines,
clotting factors, and antibodies (Brasel et al. (1996), Blood
88:2004-2012; Kaufman et al. (1988), J. Biol Chem 263:6352-6362;
McKinnon et al. (1991), J. Mol Endocrinol 6:231-239; Wood et al.
(1990), J. Immunol. 145:3011-3016). The dihydrofolate reductase
(DHFR)-deficient mutant cell lines (Urlaub et al. (1980), Proc Natl
Acad Sci USA 77: 4216-4220), DXB11 and DG-44, are desirable CHO
host cell lines because the efficient DHFR selectable and
amplifiable gene expression system allows high level recombinant
protein expression in these cells (Kaufman R. J. (1990), Meth
Enzymol 185:537-566). In addition, these cells are easy to
manipulate as adherent or suspension cultures and exhibit
relatively good genetic stability. CHO cells and proteins
recombinantly expressed in them have been extensively characterized
and have been approved for use in clinical commercial manufacturing
by regulatory agencies.
[0084] The methods of the invention can be used to culture cells
that express recombinant proteins of interest. The expressed
recombinant proteins may be secreted into the culture medium from
which they can be recovered and/or collected. In addition, the
proteins can be purified, or partially purified, from such culture
or component (e.g., from culture medium) using known processes and
products available from commercial vendors. The purified proteins
can then be "formulated", meaning buffer exchanged, sterilized,
bulk-packaged, and/or packaged for a final user. Suitable
formulations for pharmaceutical compositions include those
described in Remington's Pharmaceutical Sciences, 18th ed. 1995,
Mack Publishing Company, Easton, Pa.
[0085] As used herein "peptide," "polypeptide" and "protein" are
used interchangeably throughout and refer to a molecule comprising
two or more amino acid residues joined to each other by peptide
bonds. Peptides, polypeptides and proteins are also inclusive of
modifications including, but not limited to, glycosylation, lipid
attachment, sulfation, gamma-carboxylation of glutamic acid
residues, hydroxylation and ADP-ribosylation. "Glycoprotein" refers
to peptides, polypeptides and proteins, having at least one
oligosaccharide side chain including mannose residues.
Glycoproteins may be homologous to the host cell, or may be
heterologous, i.e., foreign, to the host cell being utilized, such
as, for example, a human glycoprotein produced by a Chinese hamster
ovary (CHO) host-cell. Polypeptides can be of scientific or
commercial interest, including protein-based drugs. Polypeptides
include, among other things, antibodies, fusion proteins, and
cytokines. Peptides, polypeptides and proteins are produced by
recombinant animal cell lines using cell culture methods and may be
referred to as "recombinant peptide", "recombinant polypeptide" and
"recombinant protein". The expressed protein(s) may be produced
intracellularly or secreted into the culture medium from which it
can be recovered and/or collected.
[0086] Examples of polypeptides that can be produced with the
methods of the invention include proteins comprising amino acid
sequences identical to or substantially similar to all or part of
one of the following proteins: tumor necrosis factor (TNF), flt3
ligand (WO 94/28391), erythropoeitin, thrombopoeitin, calcitonin,
IL-2, angiopoietin-2 (Maisonpierre et al. (1997), Science
277(5322): 55-60), ligand for receptor activator of NF-kappa B
(RANKL, WO 01/36637), tumor necrosis factor (TNF)-related
apoptosis-inducing ligand (TRAIL, WO 97/01633), thymic
stroma-derived lymphopoietin, granulocyte colony stimulating
factor, granulocyte-macrophage colony stimulating factor (GM-CSF,
Australian Patent No. 588819), mast cell growth factor, stem cell
growth factor (U.S. Pat. No. 6,204,363), epidermal growth factor,
keratinocyte growth factor, megakaryote growth and development
factor, RANTES, human fibrinogen-like 2 protein (FGL2; NCBI
accession no. NM_00682; Ruegg and Pytela (1995), Gene 160:257-62)
growth hormone, insulin, insulinotropin, insulin-like growth
factors, parathyroid hormone, interferons including
.alpha.-interferons, .gamma.-interferon, and consensus interferons
(U.S. Pat. Nos. 4,695,623 and 4,897,471), nerve growth factor,
brain-derived neurotrophic factor, synaptotagmin-like proteins (SLP
1-5), neurotrophin-3, glucagon, interleukins, colony stimulating
factors, lymphotoxin-.beta., leukemia inhibitory factor, and
oncostatin-M. Descriptions of other glycoproteins may be found in,
for example, Human Cytokines: Handbook for Basic and Clinical
Research, all volumes (Aggarwal and Gutterman, eds. Blackwell
Sciences, Cambridge, Mass., 1998); Growth Factors: A Practical
Approach (McKay and Leigh, eds., Oxford University Press Inc., New
York, 1993); and The Cytokine Handbook, Vols. 1 and 2 (Thompson and
Lotze eds., Academic Press, San Diego, Calif., 2003).
[0087] Additionally the methods of the invention would be useful to
produce proteins comprising all or part of the amino acid sequence
of a receptor for any of the above-mentioned proteins, an
antagonist to such a receptor or any of the above-mentioned
proteins, and/or proteins substantially similar to such receptors
or antagonists. These receptors and antagonists include: both forms
of tumor necrosis factor receptor (TNFR, referred to as p55 and
p75, U.S. Pat. No. 5,395,760 and U.S. Pat. No. 5,610,279),
Interleukin-1 (IL-1) receptors (types I and II; EP Patent No.
0460846, U.S. Pat. No. 4,968,607, and U.S. Pat. No. 5,767,064),
IL-1 receptor antagonists (U.S. Pat. No. 6,337,072), IL-1
antagonists or inhibitors (U.S. Pat. Nos. 5,981,713, 6,096,728, and
5,075,222) IL-2 receptors, IL-4 receptors (EP Patent No. 0 367 566
and U.S. Pat. No. 5,856,296), IL-15 receptors, IL-17 receptors,
IL-18 receptors, Fc receptors, granulocyte-macrophage colony
stimulating factor receptor, granulocyte colony stimulating factor
receptor, receptors for oncostatin-M and leukemia inhibitory
factor, receptor activator of NF-kappa B (RANK, WO 01/36637 and
U.S. Pat. No. 6,271,349), osteoprotegerin (U.S. Pat. No.
6,015,938), receptors for TRAIL (including TRAIL receptors 1, 2, 3,
and 4), and receptors that comprise death domains, such as Fas or
Apoptosis-Inducing Receptor (AIR).
[0088] Other proteins that can be produced using the invention
include proteins comprising all or part of the amino acid sequences
of differentiation antigens (referred to as CD proteins) or their
ligands or proteins substantially similar to either of these. Such
antigens are disclosed in Leukocyte Typing VI (Proceedings of the
VIth International Workshop and Conference, Kishimoto, Kikutani et
al., eds., Kobe, Japan, 1996). Similar CD proteins are disclosed in
subsequent workshops. Examples of such antigens include CD22, CD27,
CD30, CD39, CD40, and ligands thereto (CD27 ligand, CD30 ligand,
etc.). Several of the CD antigens are members of the TNF receptor
family, which also includes 41BB and OX40. The ligands are often
members of the TNF family, as are 41BB ligand and OX40 ligand.
[0089] Enzymatically active proteins or their ligands can also be
produced by the invention. Examples include proteins comprising all
or part of one of the following proteins or their ligands or a
protein substantially similar to one of these: a disintegrin and
metalloproteinase domain family members including TNF-alpha
Converting Enzyme, various kinases, glucocerebrosidase, superoxide
dismutase, tissue plasminogen activator, Factor VIII, Factor IX,
apolipoprotein E, apolipoprotein A-I, globins, an IL-2 antagonist,
alpha-1 antitrypsin, ligands for any of the above-mentioned
enzymes, and numerous other enzymes and their ligands.
[0090] The term "antibody" includes reference to immunoglobulins of
any isotype or subclass or to an antigen-binding region thereof
that competes with the intact antibody for specific binding, unless
otherwise specified, including human, humanized, chimeric,
multi-specific, monoclonal, polyclonal, and oligomers or antigen
binding fragments thereof. Also included are proteins having an
antigen binding fragment or region such as Fab, Fab', F(ab').sub.2,
Fv, diabodies, Fd, dAb, maxibodies, single chain antibody
molecules, complementarity determining region (CDR) fragments,
scFv, diabodies, triabodies, tetrabodies and polypeptides that
contain at least a portion of an immunoglobulin that is sufficient
to confer specific antigen binding to a target polypeptide. The
term "antibody" is inclusive of, but not limited to, those that are
prepared, expressed, created or isolated by recombinant means, such
as antibodies isolated from a host cell transfected to express the
antibody.
[0091] Examples of antibodies include, but are not limited to,
those that recognize any one or a combination of proteins
including, but not limited to, the above-mentioned proteins and/or
the following antigens: CD2, CD3, CD4, CD8, CD11a, CD14, CD18,
CD20, CD22, CD23, CD25, CD33, CD40, CD44, CD52, CD80 (B7.1), CD86
(B7.2), CD147, IL-1.alpha., IL-1.beta., IL-2, IL-3, IL-7, IL-4,
IL-5, IL-8, IL-10, IL-2 receptor, IL-4 receptor, IL-6 receptor,
IL-13 receptor, IL-18 receptor subunits, FGL2, PDGF-.beta. and
analogs thereof (see U.S. Pat. Nos. 5,272,064 and 5,149,792), VEGF,
TGF, TGF-.beta.2, TGF-.beta.1, EGF receptor (see U.S. Pat. No.
6,235,883) VEGF receptor, hepatocyte growth factor, osteoprotegerin
ligand, interferon gamma, B lymphocyte stimulator (BlyS, also known
as BAFF, THANK, TALL-1, and zTNF4; see Do and Chen-Kiang (2002),
Cytokine Growth Factor Rev. 13(1): 19-25), C5 complement, IgE,
tumor antigen CA125, tumor antigen MUC1, PEM antigen, LCG (which is
a gene product that is expressed in association with lung cancer),
HER-2, HER-3, a tumor-associated glycoprotein TAG-72, the SK-1
antigen, tumor-associated epitopes that are present in elevated
levels in the sera of patients with colon and/or pancreatic cancer,
cancer-associated epitopes or proteins expressed on breast, colon,
squamous cell, prostate, pancreatic, lung, and/or kidney cancer
cells and/or on melanoma, glioma, or neuroblastoma cells, the
necrotic core of a tumor, integrin alpha 4 beta 7, the integrin
VLA-4, B2 integrins, TRAIL receptors 1, 2, 3, and 4, RANK, RANK
ligand, TNF-.alpha., the adhesion molecule VAP-1, epithelial cell
adhesion molecule (EpCAM), intercellular adhesion molecule-3
(ICAM-3), leukointegrin adhesin, the platelet glycoprotein gp
IIb/IIIa, cardiac myosin heavy chain, parathyroid hormone, rNAPc2
(which is an inhibitor of factor VIIa-tissue factor), MHC I,
carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), tumor
necrosis factor (TNF), CTLA-4 (which is a cytotoxic T
lymphocyte-associated antigen), Fc-.gamma.-1 receptor, HLA-DR 10
beta, HLA-DR antigen, sclerostin, L-selectin, Respiratory Syncitial
Virus, human immunodeficiency virus (HIV), hepatitis B virus (HBV),
Streptococcus mutans, and Staphlycoccus aureus. Specific examples
of known antibodies which can be produced using the methods of the
invention include but are not limited to adalimumab, bevacizumab,
infliximab, abciximab, alemtuzumab, bapineuzumab, basiliximab,
belimumab, briakinumab, canakinumab, certolizumab pegol, cetuximab,
conatumumab, denosumab, eculizumab, gemtuzumab ozogamicin,
golimumab, ibritumomab tiuxetan, labetuzumab, mapatumumab,
matuzumab, mepolizumab, motavizumab, muromonab-CD3, natalizumab,
nimotuzumab, ofatumumab, omalizumab, oregovomab, palivizumab,
panitumumab, pemtumomab, pertuzumab, ranibizumab, rituximab,
rovelizumab, tocilizumab, tositumomab, trastuzumab, ustekinumab,
vedolizomab, zalutumumab, and zanolimumab.
[0092] The invention can be used to produce recombinant fusion
proteins comprising, for example, any of the above-mentioned
proteins. For example, recombinant fusion proteins comprising one
of the above-mentioned proteins plus a multimerization domain, such
as a leucine zipper, a coiled coil, an Fc portion of an
immunoglobulin, or a substantially similar protein, can be produced
using the methods of the invention. See e.g. WO94/10308; Lovejoy et
al. (1993), Science 259:1288-1293; Harbury et al. (1993), Science
262:1401-05; Harbury et al. (1994), Nature 371:80-83; Hikansson et
al. (1999), Structure 7:255-64. Specifically included among such
recombinant fusion proteins are proteins in which a portion of a
receptor is fused to an Fc portion of an antibody such as
etanercept (a p75 TNFR:Fc), and belatacept (CTLA4:Fc). In another
embodiment are antibody-drug conjugates.
[0093] While the terminology used in this application is standard
within the art, definitions of certain terms are provided herein to
assure clarity and definiteness to the meaning of the claims.
Units, prefixes, and symbols may be denoted in their SI accepted
form. Numeric ranges recited herein are inclusive of the numbers
defining the range and include and are supportive of each integer
within the defined range. Unless otherwise noted, the terms "a" or
"an" are to be construed as meaning "at least one of". The section
headings used herein are for organizational purposes only and are
not to be construed as limiting the subject matter described. The
methods and techniques described herein are generally performed
according to conventional methods well known in the art and as
described in various general and more specific references that are
cited and discussed throughout the present specification unless
otherwise indicated. See, e.g., Sambrook et al. Molecular Cloning:
A Laboratory Manual, 3rd ed., Cold Spring Harbor Laboratory Press,
Cold Spring Harbor, N.Y. (2001) and Ausubel et al., Current
Protocols in Molecular Biology, Greene Publishing Associates
(1992), and Harlow and Lane Antibodies: A Laboratory Manual Cold
Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y. (1990).
All documents, or portions of documents, cited in this application,
including but not limited to patents, patent applications,
articles, books, and treatises, are hereby expressly incorporated
by reference.
[0094] The present invention is not to be limited in scope by the
specific embodiments described herein that are intended as single
illustrations of individual aspects of the invention, and
functionally equivalent methods and components are within the scope
of the invention. Indeed, various modifications of the invention,
in addition to those shown and described herein will become
apparent to those skilled in the art from the foregoing description
and accompanying drawings. Such modifications are intended to fall
within the scope of the appended claims.
[0095] The following examples demonstrate embodiments and aspects
of the disclosed methods and are not intended to be limiting.
EXAMPLES
[0096] The substitution of alternative carbohydrate species for
glucose within a bioreactor system for the purposes of manipulating
high mannose glycoform content and overall protein quality is
addressed.
Example 1
Fed-Batch Culture with Continuous Glucose Feed and Bolus Galactose
Feed
[0097] The effects of reduced glucose and an alternative carbon
source on cell culture growth, titer and product quality,
particularly the Man5 levels, was evaluated by testing different
glucose and galactose concentrations using a fed-batch process. The
goal of the experimental was to reduce the amount of glucose
available in the cell culture medium, while providing a different
carbon source through a galactose feed.
[0098] Twelve 2L Applikon bioreactors were inoculated with CHO
cells expressing a recombinant IgG2 antibody at 20e5 viable
cells/mL in a working volume of 1L of a serum free cell culture
medium. Cultures were maintained at 36.degree. C., 30% dissolved
oxygen (DO), 290 rpm agitation, and pH of 6.95. A tyrosine-cystine
supplement was fed on days 2 and 5, volumetrically at 0.36% based
on the initial volume. CO.sub.2 and 1M sodium carbonate base were
added as needed for pH control.
[0099] Bolus feeding of culture media was on days 2, 5 at 9,
volumetrically based on 9% of the initial volume.
[0100] A two-factor experiment design was chosen to evaluate cell
culture performance and product quality attributes with varying
amounts of glucose and galactose in the cell culture medium. The
experiment design consisted of 6 treatments, duplicate bioreactors
for each treatment as shown in Table 1. The first factor was
continuous glucose feeding (continuous glucose) to deliver 3, 2, or
1 g/day of glucose starting from day 2. The treatments with 3 g/day
glucose also received additional bolus glucose feeds to maintain
the glucose concentration at 3 g/L. The purpose was to ensure that
3 g/day treatments were maintained as positive controls, never
having a glucose limitation.
[0101] The second factor was bolus feeds with (1+, 2+, 3+) and
without (1-, 2-, 3-) galactose (bolus galactose). The objective was
to maintain the concentration of galactose in the cell culture
media above 4 g/L starting on day 2.
TABLE-US-00001 TABLE 1 The 2-factor experimental design for the
fed-batch experiment Continuous Bolus Run Glucose, g/day Galactose,
g/L 719 2 0 720 3 + bolus glu 0 721 3 + bolus glu 4 722 1 0 723 1 4
724 2 0 725 2 4 726 3 + bolus glu 0 727 2 4 728 1 0 729 3 + bolus
glu 4 730 1 4
[0102] During the culture run, daily samples were taken to assess
the culture. Viable cell density (VCD) and viability were
determined bench scale using Vi-Cell (Beckman Coulter, Brea,
Calif.). Packed cell volume was determined using VoluPAC
(Sartorius, Goettingen, Germany). pH, dissolved carbon dioxide
(pCO2), and dissolved oxygen (pO2) were determined using a Siemens
248 blood gas analyzer (BGA) (Chiron Diagnostics, CA. Galactose
concentration was obtained using a YSI Model 2700 Select
Biochemistry Analyzer (YSI Incorporated, Yellow Springs, Ohio).
Metabolite data (glucose, lactate, and ammonia) was obtained using
Polymedco Polychem Analyzer (Polymedco Inc., Cortland Manor, N.Y.).
Osmolality was determined using an Advanced Instruments model 2020
micro osmometer (Advanced Instruments, Norwood, Mass.). Supernatant
samples were stored at -80.degree. C. At the end of experiments,
frozen cell-free supernatant samples were thawed and collectively
submitted for titer and glycan analysis.
[0103] Titer was determined using HPLC analysis. Cell culture
supernatant samples from different time points were thawed and
re-filtered in a 96 well plate with 0.2 .mu.m membrane. The samples
were injected to a HPLC system (Hewlett Packard 1100) equipped with
UV detection at 280 nm using Poros.RTM. A/20 2.1 mm D.times.30 mm L
column (Applied Biosystems, Foster City, Calif.) at a flow rate of
2 mL/min. Gradient method using mobile phase 100 mM sodium
phosphate/250 mM sodium chlorite and 2% Acetic acid/100 mM glycine
were used to elute each protein sample for every 5 min.
[0104] For glycan analysis, cell culture supernatant samples were
collected and purified by Protein A. The purified samples were
treated with PNGase-F and incubated at 37.degree. C. for 2 hours to
release the N-linked glycans. The enzymatically released glycans
were labeled with 2-aminobenzoic acid (2-AA) at 80.degree. C. for
75 minutes. Excess 2-AA label was then removed with a Glycoclean S
cartridge. The samples were evaporated overnight and the resulting
dry pellet was reconstituted with water for subsequent HILIC
(hydrophilic interaction liquid chromatography) analysis. The
glycans were injected and bound to the column in high organic
conditions and eluted with an increasing gradient of an aqueous
ammonium formate buffer. Fluorescence detection was used to monitor
the glycan elution and the relative percentage of the major and
minor glycan species were calculated.
Results from Fed-Batch Process with Continuous Glucose Feed and
Bolus Galactose Feed
[0105] The cell culture treatments that received 3 g/day of
continuous glucose feed (Runs 720, 721, 726, and 729), also
received bolus glucose feed to keep their level above 3 g/L.
[0106] Runs 720 and 726, which received no bolus galactose feed,
routinely required bolus feeds of glucose, while the runs receiving
galactose (runs 721 and 729) did not require bolus glucose feeds as
often. The cell cultures receiving 1 or 2 g/day of continuous
glucose feed, did not receive any additional bolus glucose feeds.
The spent media analysis of these cultures showed the glucose
concentration was 0 g/L on day 4 regardless of whether or not the
culture received bolus galactose feeds. (FIG. 1A).
[0107] The cell cultures receiving bolus galactose feeds (Runs 721,
723, 725, 727, 729, and 730), maintained galactose levels above 2.5
g/L although the original target was above 4 g/L. (FIG. 1B) When
the galactose consumption numbers were analyzed, it was found that
there was a statistically significant difference in how much
galactose the cultures consumed for the cultures with limited
glucose (Runs receiving 2 g/day or 1 g/day continuous glucose feed)
or without limited glucose (Runs receiving 3 g/day continuous
glucose feed plus bolus glucose feed). The cultures with limited
glucose consumed an average of 4.60 grams of galactose total, while
those without a limitation on glucose consumed an average of 3.81
grams.
[0108] The continuous glucose feeds and bolus galactose feeds had
significant impact on viable cell density and viability. The
cultures with limited glucose (Runs receiving 2 g/day or 1 g/day
continuous glucose feed), along with a bolus galactose feed,
maintained good viable cell density and viability. However, the
cultures with limited glucose (Runs receiving 2 g/day or 1 g/day
continuous glucose feed) that did not receive bolus galactose feeds
could not maintain viable cell density and viability once the
glucose reached a limitation on day 4. (FIGS. 1C and 1D)
[0109] The above data indicated that galactose could be used as an
alternative carbon source when glucose was limited in the cell
culture medium. Although the cultures with limited glucose (Runs
receiving 2 g/day or 1 g/day continuous glucose feed), along with
bolus galactose feed, maintained good viable cell density and
viability, the titer was reduced significantly compared to those
cultures with no glucose limitation (Runs receiving 3 g/day
continuous glucose feed), see FIG. 1E. Statistical analysis showed
that the continuous glucose feed level had the greatest effect on
titer; the bolus galactose feed was also significant, but to a
lesser degree.
[0110] The Man5 levels in the day 7 samples were reduced in
proportion to the increase of glucose feed from 1 g/day to 3 g/day
regardless of whether there was a galactose feed. Limited glucose
was the only statistically significant factor that resulted in Man5
increase in culture. (FIG. 1F)
Example 2
Perfusion Process with Limited Glucose, Galactose as Alternative
Carbon Source and the Addition of Glutamine
[0111] The above fed-batch study showed that limiting glucose was
the only factor that resulted in Man5 increase; however cultures
with limited glucose could not maintain viable cell density or cell
viability. The alternative carbon source, galactose, did not result
in Man5 increase, but was catabolized by the CHO cells and
maintained good viable cell density and cell viability in those
cultures where it was added. However, titer was reduced
significantly with limited glucose levels even with alternative
carbon source present. Achieving desirable product quality without
significant improvement in titer is not commercially viable, which
is the same case as achieving significant improvement in titer
without comparable product quality.
[0112] In order to achieve the goals of maintaining or improving
titer and achieving desirable product quality, the effects of low
glucose and an alternative carbon source on cell culture
performance and Man5 levels were tested in a perfusion cell
culture. The experiment design consisted of 3 treatments, duplicate
bioreactors for each treatment.
[0113] On day 0, CHO cells expressing a recombinant IgG2 antibody
were inoculated into 3L production bioreactors at 1.times.10.sup.6
viable cells/mL in a working volume of 1300 ml of a serum-free
defined cell culture medium containing 5-8 g/L glucose. Cultures
were maintained at 36.degree. C., dissolved oxygen at 30%,
agitation at 400 RPM. The culture was grown in batch mode for three
days. The concentration of glucose in spent medium analysis ranged
from 1-8 g/L.
[0114] On days 3 and 6 the culture received bolus feeds of a
concentrated serum-free defined feed media, 8% initial working
volume on day 3 and 8% initial working volume on day 6. Bolus
glucose feeds were done on days 3, 4, 5, 6, 7 to maintain a target
concentration of 8 g/L glucose in the culture. Glucose in spent
medium analysis ranged from 1-8 g/L.
[0115] Perfusion was started on day 7 at a perfusion rate of 0.48
Vol/day. Perfusion was accomplished using an alternating tangential
flow perfusion and filtration system (Refine Technologies, Hanover,
N.J.) with a 30 kDa hollow fiber filter (GE Healthcare, Uppsala,
Sweden). The serum free defined perfusion medium, pH 7.0, contained
15 g/L glucose. Glucose in spent medium analysis ranged from 3-8
g/L.
[0116] On day 11 the switch was made to a serum free, defined
perfusion medium now containing galactose and having a reduced
amount of glucose, see Table 2a. The concentration of glucose in
the perfusion medium was decreased to 2 g/L or 4 g/L. Galactose was
compounded into the medium at 6 g/L. Bolus feeds of a 30% galactose
stock solution were used as needed to maintain galactose at a
concentration of 4 g/L or above in the cell culture.
[0117] For this experiment, the perfusion culture medium also
included glutamine at 5 or 10 mM to determine if glutamine, like
glucose, had any effect on viable cell density, cell viability,
titer and/or Man5 levels in a situation of glutamine limitation.
The literature suggested that low glutamine concentrations could
have a negative impact on cell culture. The cultures were perfused
with this cell culture medium until harvest on day 17.
TABLE-US-00002 TABLE 2a Concentration of glucose, galactose and
glutamine in the day 11 serum free defined perfusion culture medium
(pH 7.0) Galactose Glutamine Run Glucose g/L g/L mM 79 2 6 10 81 2
6 10 82 4 6 10 83 4 6 10 88 4 6 5 89 4 6 5
[0118] Cell culture profiles are shown in FIG. 2. The viable cell
density and viability profiles show comparable trends (FIGS. 2 A
and 2B). The viability of the low glucose (2 g/L) and the low
glutamine (5 mM) conditions showed a downward trend between day 15
and 17. However, the concentration of glutamine in the spent media
analysis indicated that glutamine was not limited under any of the
conditions tested (FIG. 2C)
[0119] The surprising finding was that the packed cell volume
adjusted Titer (PCV Titer) shown in FIG. 2D was close to the values
seen for a perfusion process that was not glucose limited. The
titer from the perfusion experiments in this example was much
greater that that seen in the fed-batch process of Example 1 which
only yielded a 50% titer. These data indicate that the cells
exhibit a different physiological state when glucose limited in a
perfusion process than they do in a fed batch process.
[0120] Spent media analysis show that the glucose concentration in
culture supernatants treated with 2 g/L glucose in the perfusion
medium reached zero on day 12 and the glucose concentration in
culture supernatants treated with 4 g/L glucose reached zero on day
13, except for Run 83 (FIG. 2E). The spend media analysis confirmed
that the cultures were in a limited glucose state.
[0121] In general, the concentration of galactose in culture
determined by spent media analysis remained above 4 g/L (FIG.
2F).
[0122] Table 2b shows that Man5 species increased when the glucose
concentration in the perfusion medium was lowered to 2 g/L. The
time course data shows that the Man5 species increased with an
increase in culture duration (Day 15 to Day 17). All things being
equal, when the concentration of glucose in the perfusion medium
was increased to 4 g/L, the Man5 species decreased accordingly.
These results indicate that limiting glucose resulted in an
increase in Man5 levels and that the limited state could be
initiated by reducing glucose concentration in the perfusion cell
culture medium to 2 g/L or lower and confirming with spent media
analysis. However, process variation and cell mass can impact
glucose limitation and the modification in Man5 species. Run 83,
showed a higher Man5 value than any other run receiving glucose at
4 g/L. In this case Run 83 had a higher viable cell density and
packed cell volume adjusted titer (FIGS. 2A and 2D) than any of the
cultures receiving 2 g/L glucose (Runs 79 and 81) but like Runs 79
and 81, it reached a lower glucose concentration as measured by
spent medium analysis on day 12. This was earlier than any culture
receiving glucose at 4 g/L (FIG. 2E). Therefore, factors such as
cell mass and/or process variation can impact the glucose feed
concentration resulting in a limited glucose situation. In this
case where cell density was higher on day 12 (FIG. 2A) leading to a
near 0 g/L concentration of glucose in the spent medium, a limited
glucose state was initiated even though the cell culture was fed
with a high glucose (4 g/L) perfusion feed medium. Once glucose was
limited, Man5 levels increased.
TABLE-US-00003 TABLE 2b Man5 % at day 15 and 17 following the
change in perfusion medium formulation at day 11 Galactose
Glutamine Day 15 Day 17 Run Glucose g/L g/L mM Man5 % Man5 % 79 2 6
10 9.29 9.84 81 2 6 10 9.28 9.49 82 4 6 10 4.64 5.62 83 4 6 10 7.56
8.91 88 4 6 5 5.19 5.65 89 4 6 5 5.09 5.63
Example 3
Perfusion Process with a Combination of Reduced Glucose and High
Galactose
[0123] An experiment was performed with a serum free defined
perfusion medium (pH 7.0) formulated with glucose at concentrations
of 0, 1.5 or 3 g/L. Galactose was added at 10, 11.5 or 13 g/L,
based on the total consumption rate of experiment described
above.
[0124] Both glucose and galactose were compounded into perfusion
media so the culture could be maintained without bolus feeds of
either glucose or galactose. Compounding reduced the complexity of
the process and improved consistency. The experiment was performed
as described above; using the same feeding strategies on days 0 to
10. Table 3 provides the combinations of perfusion medium
formulations used on days 11 through 17.
TABLE-US-00004 TABLE 3 Experiment design of glucose and galactose
in perfusion media. Run Glucose g/L Galactose g/L 103 3 13 104 0 10
105 0 13 106 0 10 107 1.5 11.5 108 0 13 109* 3 10 111 3 13 112 3 10
113 1.5 11.5 *Run 109 was excluded from ihe figures due to
bioreactor operational failure.
[0125] The cell culture profiles in FIG. 3 show that all cell
culture conditions tested were glucose limited following the day 11
switch (FIG. 3A) and the galactose concentrations measured in the
spent medium assay was maintained between 4 to 8 g/L (FIG. 3B)
which was proportional to the galactose concentrations compounded
in perfusion medium. The lactate level dipped to zero once glucose
reached a limitation on day 12 (FIG. 3C). The ammonia level
increased starting on day 10, before glucose reached a limitation
(FIG. 3D). It was very interesting to see that lowering glucose
concentration starting on day 11 resulted in lower growth,
viability, and titer (FIGS. 3E-3G). These results indicate that the
limited glucose, not glutamine limitation, causes titer reduction
in a perfusion process as well as the fed-batch process in Example
1. Also, since glucose levels of 2-3 g/L, and even up to 4 g/L,
resulted in the increase in Man5 levels, the glucose levels also
provided some help in maintaining higher titer levels.
[0126] Statistical analysis using JMP software (JMP Inc. Cary,
N.C.) revealed that glucose concentration was the only
statistically significant (p value=0.032) factor that impacted
titer. The galactose was not statistically significant factor for
titer (FIG. 4A). On the other hand, both glucose and galactose were
not statistically significant factors that impacted Man5 species,
but the interaction between glucose and galactose was statistically
significant (p value=0.0613). (FIG. 4B). The higher the galactose
concentration the greater the effect of the limited glucose on Man5
species.
[0127] Overall the Man5 levels increased and leveled off when
glucose ranged from 0 to 3 g/L and decreased when the glucose
levels were 4 g/L or greater. FIG. 5 shows the increase in percent
of Man5 species on day 11, 13, 15, and 17. For all culture
conditions, percent Man5 species started at about 2% on day 11 and
then gradually increased to over 10% on day 17. The most
significant increase in percent Man5 species was on days 11 to 13
when glucose became limited.
[0128] Since glucose impacts titer, glucose should be fed at the
highest concentration that will still support an increase in Man5
while maintaining cell viability, density and titer at an
acceptable level, based on the conditions of the cell culture, such
as cell mass, the cell culture process and the alternate carbon
source used. For example, for a perfusion cell culture having from
15 to 25.times.10.sup.6 cells/ml, glucose concentrations of 0-4 g/L
in combination with galactose at 10-13 g/L, resulted in an increase
of Man5.
Example 4
Perfusion Process with Limited Glucose and Sucrose as Alternative
Carbon Source
[0129] Sucrose was identified as another carbon source associated
with an increase in Man5 levels. In this experiment, the same
culture conditions as described in Example 3 were used, except on
day 11, glucose concentrations were 2, 4, and 6 g/L and sucrose was
used in place of galactose at concentrations of 16, 20, and 24 g/L.
Both glucose and sucrose were compounded into perfusion media
without additional bolus feeds of either sugar after day 11, see
Table 4.
TABLE-US-00005 TABLE 4 Experiment design of glucose and sucrose in
perfusion media. Run Glucose g/L Sucrose g/L 153 6 24 164 2 16 155
2 24 156 2 24 157 4 20 158 6 16 159* 2 16 160 6 24 162 6 16 163 4
20 *Run 159 was excluded from JMP analysis due to bioreactor
operational failure on day 14
[0130] FIG. 6A shows all cell cultures conditions achieved a
limited glucose state on day 12. The sucrose levels determined by
spent media assay showed that sucrose was essentially unchanged
from the concentration in the cell culture medium (FIG. 6B). The 1
g/L difference between the concentration of sucrose in the
perfusion medium and in the spent medium was derived from sucrose
assay variability and dilution effect. This data indicated that
sucrose was not catabolized by CHO cells. Sucrose functions as a
hyperosmomatic stress in cell culture that could impact protein
glycosylation, see Schmelzer and Miller, Biotechnol. Prog. (2002)
18:346-353; Schmelzer and Miller Biotechnol. Bioeng (2002) 77 (4)
February 15; U.S. Pat. No. 8,354,105.
[0131] The slight increase in viable cell density, viability and
titer resulted from the increase in glucose concentration from 2 to
6 g/L in perfusion medium (FIGS. 6C, 6D and 6F). Lactate levels
dipped to zero once the glucose reached limitation on day 12 (FIG.
6G). The ammonia level increased starting on day 11 after glucose
reached limitation and sucrose was added (FIG. 6E).
[0132] The statistical analysis using JMP software (JMP Inc. Cary,
N.C.) revealed that both glucose concentration (p value=0.0021) and
sucrose (p value=0.0823) were statistically significant factors
that impacted titer (FIG. 7A). The impact of glucose was most
significant (FIG. 7B); the impact of sucrose on titer could be as a
result of osmolality stress (Schmelzer and Miller, supra; U.S. Pat.
No. 8,354,105).
[0133] Both glucose concentration (p value=0.001) and sucrose (p
value=0.0012) were statistically significant factors that impacted
viability (FIG. 7C). Higher glucose concentrations improved
viability while higher sucrose concentrations reduced
viability.
[0134] Glucose was the only statistically significant factor that
impacted Man5 species (p value=0.019). Overall the Man5 levels were
increased when the glucose concentration in the cell culture medium
ranged from 2 to 6 g/L.
* * * * *