1. PDA: A Global
Association
Analysis of Controlled
Nucleation
Technologies
Jim Searles, Ph.D.
Director, Pharmaceutical Development
Hospira, Inc.
McPherson, KS, USA
james.searles@hospira.com
PDA Europe Pharmaceutical Freeze Drying Conference, 16 September 2014, Brussels Belgium
6. Nucleation is not all of freezing
• Only a fraction of the
water crystallizes
during the initial
nucleation event
• The remainder
crystallizes during
“solidification”
• “Slushy” phase
• Lots of changes can
occur during this time
6
Searles, Carpenter & Randolph 2001
J. Pharm. Sci.
90(7):860
7. Effect of Nucleation T
7
R2
= 0.6037
50
70
90
110
130
150
-18 -12 -6 0
Nucleation Temperature, °C
PrimaryDryingRate,mg/hr
P. Syringae
AgI
High-
Particulate
Pre-
Cooled
Shelf
Scored Vial
Low-Particulate
Searles et al. 2001 J Pharm Sci 90(7):860
9. Types Covered
Rapid depressurization Praxair & SP
Scientific ControLyoTM
Starts with Gasteyer et al. patent
app filed in 2007
Ice
fog
Pikal cold N2 introduction
Rambhatla et al. 2004,
Patel et al. 2009
IMA Life & Linde Veriseq® ice
crystal injection
Chakravarty et al. 2012
Rapid re-pressurization from
vacuum
Geidobler et al. 2012 & 2013,
Izutsu et al. 2014
Millrock FreezeBoosterTM ice
crystal injection
Thompson 2013,
Ling 2014 patent app
Ultrasound
Nakagawa et al. 2006, Hottot et al.
2008, Passot et al. 2009 (Telstar)
9
10. Also of Interest
10
Electrical, magnetic field
Peterson et al. 2006 (2),
Woo & Mujumdar 2010
Gap-freezing
Kuu et al. 2013 J. Pharm. Sci
102(8):2572
Vacuum-induced surface freezing Kramer et al. 2002, Liu et al. 2005
Physical movement / disturbance
Done manually in the early days,
mechanical method the subject of
Hof 1998 patent EP 0777092 B1
SynchroFreeze – Hof Sonderlanlagen <in development>
12. Effects / Opportunities
• Larger ice crystals
– Lower water vapor flow resistance
• Faster drying & lower product T’s
– Ability to reduce lyophilization cycle times by further
optimization
– Lower specific surface area
• Less damage to proteins
– Faster reconstitution
• Anhydrous mannitol crystals (Mehta et al. 2013)
• Ability to use previously-unavailable thermal
history post-nucleation for additional benefits
and innovations
12
14. 1. Cool to desired temperature (below
freezing point), and
pressurize the chamber (at least 7 psig)
2. Rapidly depressurize
14
15. Postulated Mechanisms
15
•Gas Bubbles: “An initial elevated pressure increases the concentration
of dissolved gas in the solution. The rapid decrease in pressure after
cooling reduces the gas solubility, and the subsequent release of gas
from the sub-cooled solution triggers nucleation of the phase transition.”
•Gas Cooling Freezes Liquid: “the temperature decrease of the gas
proximate the material during depressurization causes a cold spot on
the surface of the material that initiates nucleation.”
•Evaporative Cooling: “the depressurization causes evaporation of
some liquid in the material and the resultant cooling from the
endothermic evaporation process may initiate the nucleation.”
•Ice Fog: “the depressurized cold gas proximate the material freezes
some vapor either in equilibrium with the material prior to
depressurization or liberated from the material by evaporation during
depressurization; the resultant solid particles re-enter the material and
act as seeds or surfaces to initiate nucleation.”
17. 17
“Three anhydrous polymorphs (-, -, and -mannitol) and mannitol
hemihydrate (MHH; C6H14O6·0.5H2O) have been observed in freeze-dried
formulations”
“The existence of MHH in the final lyophile is undesirable – the water released
by MHH dehydration during storage has the potential to cause undesirable
physical and chemical changes in other formulation components”
High protein concentrations and other excipients can inhibit the formation of
MHH.
19. 19
“MHH formation was completely prevented when crystallization
occurred at temperatures ≥-10 ºC. This can be practically challenging,
since supercooling of solutions is commonly encountered during
freeze-drying. Thus, the use of a freeze-dryer with controlled ice
nucleation can be an effective strategy to cause ice crystallization at
elevated temperatures (i.e. prevent pronounced supercooling) and
consistently yield anhydrous mannitol.”
“once anhydrous mannitol crystallized in the frozen solutions, it did not
transform to MHH during freeze-drying and vice versa.”
34. 34
FreezeBoosterTM by Millrock Technologies
1. Product is maintained at a predetermined temperature and pressure in a
chamber of the freeze dryer, and
2. A predetermined volume of condensed frost is created on an inner surface of a
condenser chamber separate from the product chamber and connected thereto
by a vapor port.
3. The opening of the vapor port into the product chamber when the condenser
chamber has a pressure that is greater than that of the product chamber
creates gas turbulence that breaks down the condensed frost into ice crystals
4. (The ice crystals) rapidly enter the product chamber for even distribution therein
to
5. (which) creates uniform and rapid nucleation of the product in different areas of
the product chamber.
36. 36
1. The shelves of the lyophilizer are cooled and the product is
equilibrated to the desired product temperature.
2. The freeze-dryer is then depressurized to a specified
vacuum set point (3.7 mbar, 2.8 Torr) and immediately
brought to atmospheric pressure via the cold condenser.
3. During the repressurization, almost instant nucleation of the
product takes place.
37. 37
To increase water vapor amount in the chamber and condenser coils, a tray of 100 mL high-purified water was placed into
the lyophilizer, and in addition, 10 mL of water was sprayed on the condenser coils before triggering nucleation at a
product temperature of −5◦C. After nucleation, the samples were thermally treated at −5◦C for 120 min. Complete
solidification was achieved by ramping down to −60◦C with a ramp of 1◦C/min.
2013
38. 38
"Evaporation-induced cooling of the solution surface and induction of small
ice crystals that are blown from the condenser by the nitrogen gas flow are
considered to trigger the simultaneous freezing in many tubes."
For this study, a modified controlled ice nucleation method based on the one
reported by Geidobler et al. was also applied in the freezing step of some
protein solutions (18). For the controlled nucleation, the sample-loaded
lyophilizer shelf was cooled from room temperature to −5°C and maintained at
that temperature for 1 h. Ice nucleation was triggered by a quick release of
the vacuum after the chamber pressure was reduced to 4 mbar. Visual
observation indicated simultaneous ice formation from the top of all solutions
upon introduction of nitrogen gas through the drain. Primary drying was started
after the shelf was cooled to −32°C (0.5°C/min).
43. Conclusions
• There are controlled nucleation technologies
that are close to commercialization
• Benefits
– Less vial-to-vial heterogeneity
– Shorter primary drying at lower product temperatures
– Lower specific surface area of lyophilized cake
– Improved product appearance
– Shorter reconstitution time
– Expansion of the design space for achieving
anhydrous mannitol crytallization
– Improved protein recovery
43
