Cell culture methods

1. A process for producing a recombinant protein comprising:

a) culturing host cells capable of producing a recombinant protein in a medium free of animal-derived products, wherein the host cells are CHO cells;

b) supplementing the culture during production phase with

cysteine or cystine in a total amount of from wt %12 wt % to 28 wt % of the expected total amount of recombinant protein produced; and

tryptophan in a total amount of from 8 wt % to 30 wt % of the expected total amount of recombinant protein produced,

c) and, optionally, recovering the recombinant protein from the cell culture medium wherein the recombinant protein is an antibody or an antigen-binding fragment thereof, wherein the recombinant protein is produced by the cells during said production phase, and wherein one or more initial experiments are performed to determine the expected total amount of recombinant protein produced.

2. The process according to claim 1 , wherein the culture is supplemented with cysteine or cystine in a total amount of from 12 wt % to 25 wt % of the expected total amount of recombinant protein produced.

3. The process according to claim 1 , wherein the culture is supplemented with tryptophan in a total amount of from 8 wt % to 25 wt % of the expected total amount of recombinant protein produced.

4. The process according to claim 1 , wherein the total amount of cysteine or cystine and tryptophan in the culture is reached by adding cysteine or cystine and tryptophan to the cell culture medium:

a) at the beginning of the production phase,

b) once or multiple times at any time point during the production phase,

c) through continuous addition during the production phase, or

d) in any combination of a), b) and c).

5. The process according to claim 1 , wherein the process is a batch process or a fed-batch process.

6. The process according to claim 1 , wherein cysteine or cystine and tryptophan are provided through daily addition during the production phase.

7. The process according to claim 1 , wherein the production phase is performed for at least 7 days.

8. The process according to claim 1 , wherein the antibody or antigen-binding fragment thereof is:

1) an antibody or antigen-binding fragment thereof which

a) comprises CDR-H1 having the sequence as defined in SEQ ID NO: 1; CDR-H2 having the sequence as defined in SEQ ID NO: 2; CDR-H3 having the sequence as defined in SEQ ID NO: 3; CDR-L1 having the sequence as defined in SEQ ID NO: 4; CDR-L2 having the sequence as defined in SEQ ID NO: 5 and CDR-L3 having the sequence as defined in SEQ ID NO: 6; or

b) comprises a light variable region having the sequence as defined in SEQ ID NO: 7 and a heavy variable region having the sequence as defined in SEQ ID NO: 8; or

c) comprises a light variable region having at least 80% identity or similarity to the sequence as defined in SEQ ID NO: 7 and a heavy variable region having at least 80% identity or similarity to the sequence as defined in SEQ ID NO: 8; or

d) comprises a light variable region having the sequence as defined in SEQ ID NO: 7 and a heavy chain having the sequence as defined in SEQ ID NO: 11; or

e) comprises a light variable region having at least 80% identity or similarity to the sequence as defined in SEQ ID NO: 7 and a heavy chain having at least 80% identity or similarity to the sequence as defined in SEQ ID NO: 11; or

2) an antibody which comprises a light chain having the sequence as defined in SEQ ID NO: 9 and a heavy chain having the sequence as defined in SEQ ID NO: 10; or

3) an antibody which comprises a light chain having at least 80% identity or similarity to the sequence as defined in SEQ ID NO: 9 and a heavy chain having at least 80% identity or similarity to the sequence as defined in SEQ ID NO: 10.

9. The process according to claim 1 , wherein the production phase is carried out in a bioreactor with a volume of equal or more than 50 L.

10. The process according to claim 1 , wherein the process comprises the step of recovering the recombinant protein from the cell culture medium and a further step of purifying the recombinant protein.

11. The process according to claim 10 , wherein the purification comprises Protein A chromatography.

12. The process according to claim 10 , further comprising the step of formulating the purified recombinant protein.

13. The process according to claim 10 , wherein the recombinant protein is formulated in a liquid formulation comprising one or more amino acids and a surfactant.

14. The process according to claim 13 , wherein the formulation comprises histidine and/or proline.

15. The process according to claim 14 , wherein the formulation is at a pH of between 5 and 7.4 and comprises histidine in a concentration of 5 mM to 100 mM, and/or proline in a concentration of 100 mM to 500 mM.

16. The process according to claim 15 , wherein the formulation comprises histidine in a concentration of 30 mM and proline in a concentration of 250 mM and is at a pH between 5.2 and 6.0.

17. The process according to claim 13 , wherein the surfactant is polysorbate 80 in a concentration of 0.001% to 0.1% (w/v).

18. The process according to claim 13 , wherein the recombinant protein is an antibody and the antibody is formulated at a concentration of 10 mg/ml to 250 mg/ml.

19. The process according to claim 1 , wherein the process reduces the heterogeneity of the recombinant proteins produced, wherein said reduction of heterogeneity comprises reducing:

a) charge heterogeneity; and/or

b) amino acid oxidation, isomerization, fragmentation, other covalent adducts, glycation, deamidation, cysteinylation; and/or

c) colour or intensity of colour between different batches of the recombinant protein;

and/or d) high molecular weight species (HMWS); and/or

e) recombinant protein instability.

20. The method according to claim 1 , said one or more initial experiments comprising culturing the host cells of step a) under conditions allowing for the production of recombinant protein and determining the expected total amount of recombinant protein produced by the cultured cells.