Why spray dry a protein ? The spray drying process: machines & process conditions

1. STABILISING PROTEINS BY SPRAYDRYING WITH ADJUVENTSGeoffrey LeeFriedrich Alexander University, Erlangen • Why spray dry a protein ? • The spray drying process: machines & process conditions • Two examples of spray-dried pharmaceutical proteins • Sources of damage to proteins during spray drying • Formulation measures to stabilize proteins carbohydrates, surfactants • Single droplet drying via levitation • Is spray drying a potentially useful process for my product ?

2. Why Use Spray Drying for Proteins ? • Spray drying (SD) of protein-containing systems is not new ! • Advantages: robust, standard equipment, process development straightforward, relatively inexpensive, scale up; Disadvantages: needs exact in-process control, yield optimization required, minimization of deposit formation, 'continuous' process. • Applications of SD proteins in pharmacy: - inhaleable powders; - injectable powders; - stable, flowable storage-form for bulk protein.

3. The Spray Drying Process

4. Process Variables Control Product Quality •Independent process variables: - Drying Air Inlet Temperature, Tinlet - Drying Air Relative Humidity, % RH - Drying Air Flow Rate, vda - Liquid Feed Flow Rate, Vlf- Atomising Air Flow rate, vaa • Dependent variable: - Outlet Air Temperature, Toutlet

5. Laboratory Scale Spray Dryer: Niro Mobile Minor Drying Capacity up to 7 kg/hr; Maximum Tinlet 350°C; 3' x 6' x 6' high

6. Pilot Scale Spray Dryer: Niro P6.3 Drying capacity up to 60 kg/hr; Chamber 1.6 m x 0.8 m x 60°; Size 11.5' x 9' x 15'

7. Micro Spray Dryer: Büchi B-290 Drying capacity up to 1.5 kg/h; size 500 x 600 x 1000 mm

8. Feasibility of spray drying a protein • Product quality (peptide/protein) investigated by: - activity loss (enzymes) - change in aggregation status (HPLC, SEC) - gel electrophoresis: eg, isoelectric focussing - alteration in FT-IR amide bands • Example: model protein trypsinogen (Tzannis & Prestrelski, 1999) - ca 15 % activity loss on SD at Tin/Tout = 110oC/70oC - ca 20% loss of monomer (SEC) • 2 further examples of pharmaceutical proteins illustrate use of analytical techniques…

9. Example I: A low molecular weight peptide • Substance: Peptide with 20 amino acids = ca. 2.5 kDa • SD conditions: - Büchi 191 Micro Spray Dryer • Liquid Feed: - 2 mg/mL peptide (very low !)

10. Example I: SEM Appearance Residual Moisture = 2.85 % w/w

11. Example I: Aggregation status: HPLC of liquid feed

12. Example I: Aggregation status: HPLC of Product

13. Example I: Secondary structure evaluation with FT-IR

14. Example II: A high molecular weight protein • Substance: IgG (AMG 162) with MWt ca. 150 kDa • SD conditions: - Büchi 191 Micro Spray Dryer • Liquid Feed: - 115 mg/mL IgG  Sorbitol

15. Example II: SEM appearance Residual moisture = 4.4/5.0 % w/w

16. Example II: Aggregation status: SEC of liquid feed

17. Example II: Aggregation status: SEC of product

18. Example II: Aggregation status: SEC of formulated product

19. Potential sources of protein damage Drying air 2. Shearing forces Nozzle Atomizing air 1. Adsorption Liquid feed 3. Liquid/air interface expansion 4. Thermal stress Drying tower

20. The 2 periods of droplet drying Various morpholgies Critical point Constant-rate phaseT = approx. Twetbulb Falling-rate phase T  Toutlet Residence time: 1s – 25s eg, Tinlet/Toutlet = 130oC/90oC

21. Thermal inactivation of catalase

22. Primary formulation measure to reduce protein damage • Glass-forming carbohydrates or amino acids can reduce level of protein damage - prevent unfolding & aggregation - which carbohydrate/protein mass ratio ? during SD: water replacement mechanism after SD: glassy immobilisation ? • Low residual moisture content ensures high glass transition temperature, Tg important for protein storage stability • Sufficient storage stability of carrier ? amorphous systems are hygroscopic  must prevent moisture uptake & crystallisation also deterioration in powder properties

23. Stabilizing effects of trehalose on catalase

24. Secondary formulation measures • Addition of surfactant to liquid feed can reduce protein surface excess at water/air interface of atomised liquid feed • Use of non-aqueous solvents for peptides with low aqueous solubility higher w/v improves particle formation • Polymers to taylor particle morphology eg, dextrans or hydroxy ethyl starches eg, surfactants

25. Thermal inactivation of lactate dehydrogenase (LDH) in trehalose

26. Process & storage stabilities of LDH in trehalose

27. Improvement of process stability of LDH in trehalose + 0.1 % g/g Polysorbat 80

28. Development of a spray drying process for a protein • Laboratory scale SD of protein solution: - sufficient water solubility = alternative solvent - does damage to protein occur ? (aggregation) - residual moisture content OK ? - which process conditions give best result ? • Which formulation measures are necessary ? - do I need a carbohydrate ? Probably yes. - which protein/carbohydrate weight ratio ? (maximize) - adjustment of required particle size = useage ? • 2. Move to pilot scale machine: - depends on required process throughput (kg of powder per h) - upscale increases residence time in chamber - can I use the same nozzle setup ?

29. Single droplet drying levitator

30. Single droplet drying levitator

31. Single-droplet drying kinetics of carbohydate solution I II III IV

32. Single-droplet drying kinetics of maltodextrin (20%)

33. Single-droplet drying kinetics of catalase/trehalose

34. Final Particles Removed from Levitator catalase/trehalose (6:4) catalase

35. Summary & Conclusions • Spray drying is one of a number of processes that canbe used for the production of fine particles. • It is an established technique where much expertise andexperience is available. • Development can be performed under GMP conditions. • The selection of a suitable machine & process conditionshas a (fairly) sound scientific basis. • The product capacity can be adjusted within wide boundaries. • The powder properties can also be taylored by processor formulation. • Potential problems: some questions need to be addressed: - how do I obtain a high product yield ? - how do I minimize protein damage ? - how much stabilizing adjuvent do I need, and which one is the best for my protein ? - what is the patent situation ?