Cryoconcentration effects during freeze/thaw processing of bulk protein, and possible consequences of frozen storage on protein aggregation

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1 Cryoconcentration effects during freeze/thaw processing of bulk protein, and possible consequences of frozen storage on protein aggregation Satish K Singh 20 July 2010

2 Abstract Frozen storage of proteins is an important unit operation. The state of the protein and solute in the frozen state determine the outcome of this process. Frozen state mapping of a large-scale system is described. A case study about the impact of frozen storage on the aggregation state of a monoclonal antibody is used to illustrate the complex interplay between storage temperature, mobility and solubility. Finally, an example of the use of hydrogen-deuterium exchange mass spectrometry in understanding the aggregation process in the frozen state is provided. 1

3 Freezing Biologics: Advantages and Associated Challenges Advantages of freezing protein bulk: Minimization of risk of microbial growth Increased product stability with extended shelf life Elimination of agitation and foaming during transportation Flexibility for manufacturing process Outcome: Long-term stability under frozen storage Freeze concentration (Cryoconcentration) Protein denaturation on ice-liquid interface Tg vs Storage temperature 2

4 Large Scale Freeze Thaw Systems Active Freeze/Thaw Passive Freeze/Thaw Celsius System Cryovessel Plastic Bottles Adapted from Adapted from 3

5 Outline of presentation Cryowedge System Mapping the solute distribution Stability during frozen storage How does the cryoconcentration and frozen storage condition impact frozen state stability HDX to Probe Aggregation in Frozen State 4

6 Texture in frozen mass is dependent on freezing conditions Photographs of ice slices (7mm thick). Stained BSA solutions were frozen at - 20 C in a stagnant air freezer or immersed in a liquid coolant, each ice block was sliced with a band-saw. Rodrigues et al, JPS Submitted 5

7 Cryovessel Understanding freezing in a scaled-down model Adapted from 6

8 Study Design Part Part I I :: Cryowedge mapping during freezing How does the of rate of freeze/thaw (Fast Freeze Fast Thaw, Slow Freeze Slow Thaw, Gold Freeze Thaw) affect physical properties, protein concentration and soluble aggregates? Part Part II II :: Cryowedge mapping under frozen condition Does the mapping look different in frozen condition? What is the fraction of protein is affected due to cryoconcentration? 7

9 Frozen State Mapping : Formulation Buffer Solution 20 mm Histidine buffer, 84 mg/ml Trehalose Dihydrate, 0.2 mg/ml PS 80, ph Top Portion 0 Bottom Portion Osmolality (mmol/kg) Cryowedge Position Significant increase in osmolality in the bottom layer Top portion Bottom Portion Approx 1 inch 6 2 8

10 Frozen State Mapping : mab Solution (Osmolality) Top Half of frozen solution in Cryowedge Melted portion of frozen mab solution Significantly lower osmolality values for the top half Highest osmolality observed was between for the position 3 and 5 which represent the greatest distance from active heat transfer surfaces 20 mg/ml mab in 20 mm Histidine buffer, 84 mg/ml Trehalose Dihydrate, 0.2 mg/ml PS 80, ph 5.5 9

11 Frozen State Mapping : mab Solution (Conc) Top Half of frozen solution in Cryowedge Melted portion of frozen mab solution Significantly low protein concentration values for the top half for the cores Highest conc observed was between 19.5 to 23 mg/ml for the position 3 and 5 which represent the greatest distance from active heat transfer surfaces 10

12 Frozen State Mapping : mab Solution (Osmolality) Bottom Half of frozen solution in Cryowedge Melted portion of frozen mab solution Considerably higher osmolality values for the bottom half for the cores Highest osmolality observed was for the position 3 and 5 which represent the greatest distance from active heat transfer surfaces Approximately more than 4 fold cryoconcentration from osmolality values 11

13 Frozen State Mapping : mab Solution (Conc) Bottom Half of frozen solution in Cryowedge Melted portion of frozen mab solution Considerably higher protein concentration values for the bottom half for the cores Highest concentration observed was for the position 3 and 5 which represent the greatest distance from active heat transfer surfaces Approximately more than 3 fold cryoconcentration 12

14 Fraction Analysis of Protein Concentrations in Cryowedge in Frozen State Osmolality Top Protein Concentration mosm/kg, mg/ml, 1.83% 16.51% 0-10 mg/ml, 36.70% mosm/kg, 83.49% 10-20mg/mL, 61.47% Bottom mosm/kg; 3.13% mosm/kg; 7.29% mosm/kg; 2.08% mosm/kg; 10.42% mg/ml; 31.25% mg/ml; 15.63% mg/ml; 5.21% mosm/kg; 18.75% mosm/kg; 58.33% 10-20mg/mL; 46.88% 0-10 mg/ml; 0.00% mg/ml; 0.00% mg/ml; 1.04% 13

15 Density Gradient Analysis for mab solution in Frozen State Top Level Cryowedge Depth Density of 1.06 g/cm3 corresponds to approximately 3X sugar conc Bottom Level Cryowedge Position Significant increase in in density density for for the the material in in bottom bottom half half 14

16 Density gradients drive convective concentration distribution Schematic representation of natural convection as a result of temperature difference induced density gradients. 15

17 Cryoconcentration? Kolhe et al, BioPharm Intnl, June, July

18 Stability during frozen storage How does the cryoconcentration and frozen storage condition impacts frozen stability? 17

19 Frozen Stability Study Design Based on mapping information, the frozen cryowedge sections were divided into 6 different sections as indicated below: Top Centre Top Radial Top Periphery Bottom Centre Bottom Below Centre Bottom Radial Bottom periphery The frozen cores were obtained and placed on stability at -10, -20, and -40C. The stability samples were analyzed for conc and soluble aggregates 18

20 Stability of protein in cores in frozen Stability Under Frozen Conditions storage (-10, -20, -40C) (SEC data) Soluble Aggregates (%) C Initial 3 month 6 month 12 month Soluble Aggregates (%) C Protein Conc (mg/ml) Protein Conc (mg/ml) Soluble Aggregates (%) 5-40 C Protein Conc (mg/ml) -20 C frozen condition is detrimental to protein from aggregates perspective At -10 and -40 C, no significant increase in aggregates compared to -20 C 19

21 Trehalose Crystallization from Frozen State 20

22 Trehalose Crystallization from Frozen State 21

23 Viscosity and the Glass transition temperature (WLF relationship) 22

24 - 40 C No crystals seen. (The white regions is frost on the bottom of the petri dish). 0 day 3 days 7 days - 20 C Trehalose crystals visible in 3 days BioTx 0 daypharmaceutical Sciences 3 days 7 days

25 - 40 C No crystals seen. (The white regions is frost on the bottom of the petri dish). 0 day 3 days 7 days - 10 C Trehalose crystals visible in 3 days 0 day 3 days 7 days

26 Protein Stored in the Frozen State Protein Unfolded at Ice interface Temperature of storage Stasis Aggregation / Intrxn w Neighbour Refold Frozen State: High concentration Unfolding at ice surface Mobility Nearest neighbour interaction / Aggregation or Refolding 25

27 Mobility and Aggregation in the Frozen State Trehalose Crystallization 1 Protein Refolding Normalized Rate Protein Aggregation / Nearest neighbor interaction 0-40C -30C -20C -10C Tg 26

28 Conclusions 1 Trehalose crystallization at -20 C results in loss of cryoprotectant and aggregation over time Protein denaturation/unfolding at the ice interface probably contributes to this effect Mobility at -20 C allows the crystallization and the aggregation to occur Prevented by -40 C storage Storage at -10 C likely allows trehalose to crystallize but also allows protein to refold and thus preventing aggregation fr0m occuring Sucrose unlikely to crystallize out Could aggregation still occur due to mobility in the denatured protein? 27

29 HX-MS to probe mechanism of FT aggregation and structure (courtesy Aming Zhang, Erik Fernandez, U Va) Zhang et al, Poster ACS

30 Studying Protein Aggregates Aggregation mechanism Kinetics Increasing resolution, but also technically complicated Morphology and structure Macrostructure, or morphology Molecular-level structure Peptide-level structure Thermodynamics EM, AFM CD, FTIR, Fluorescence HX-MS Atomic-level structure X-ray, NMR 29 29

31 Hydrogen/deuterium exchange mass spectrometry (HX-MS) Native monomer Protein aggregate D 2 O buffer Label Quench Digest LC-MS Native H/D exchange pattern Aggregate 30

32 HX-MS Experiments to Study Aggregates resulting from Freezing 31

33 LDH-freeze-labeling-denaturation Freezing induced LDH denaturation detected by HX-MS HX-MS protocol Native LDH Flash freeze in Liquid N 2 D 2 O buffer Freezing induced LDH denaturation Partially unfold Inverse dependence on LDH concentration N Label at -10ºC Fast thaw Quenching buffer N P LC-MS U 32 32

34 Local structural perturbations with partially denatured LDH species 43 reporter peptides, four classes of HX behavior Native-like Partially unfold Fully unfold Bimodal HX 33 33

35 Structural Perturbations correlate with Local mobility Inverse dependence on protein concentration Unfolded regions on protein surface Correspond to high(er) b-factor regions b-factor is an indicator of degree of uncertainty in assignment of position 34

36 Freeze-thaw induced LDH aggregation LDH: 35.6 kda, labile to F/T stress F/T protocol: 5 min in liquid N 2 5 min in water bath repeat for multiple cycles LDH Aggregation is inversely dependent on protein concentration

37 LDH Aggregate Structure probed by Fluorescence A: Signal increase and blue shift: exposure of more hydrophobic residues in aggregates. B: Lack of apparent ThT emission peak: absence of ordered amyloid-like structure in aggregates

38 LDH aggregate structure by intact molecule HX-MS 0.1 mg/ml Fully labeled More solvent accessible to LDH aggregates molecular unfolding during aggregation. Consistent with Bis-ANS binding assay HX protected structure exists in LDH aggregates 37 37

39 LDH aggregate structure by intact molecule HX-MS LDH in the aggregates lose native structure and solvent protection - consistent with the increased binding of ANS to the aggregates, and - show a protein concentration-dependence in the freeze-thaw induced aggregation that is similar to that in the freezing-induced denaturation 38

40 LDH aggregate structure by peptide-level HX-MS 45 reporter peptide, one HX behavior Fully labeled Fully labeled 39 39

41 LDH Aggregates probed by HX-MS 40

42 Identification of intermolecular contact regions in LDH aggregates HX to native LDH HX to LDH aggregates Solvent accessibility Pep % 25-50% 50-75% % 41 Pep Pep

43 Aggregation predictions for disordered (or afibrillar) LDH aggregates Experiments: No amyloid-like structure Segments 13-31, and indicated as molecular contact regions Predictions: Correlated with all three HX identified contact regions Two false positive 42 42

44 Conclusions 2 HX-MS technique can successfully distinguish the regions of unfolding and molecular interactions during aggregation, 43

45 Acknowledgements Pfizer StL Parag Kolhe, Steve Chico, Alanta Lary, Anjali Mehta Univ. of Virginia Erik Fernandez, Aming Zhang, Wei Qi Univ of Texas, Austin Keith Johnston, Andrea Miller, Miguel Rodrigues (Lisbon) 44