LYOPHILIZATION METHODS AND APPARATUSES
Field of the Invention
[0001] The invention relates to the field of lyophilization or freeze-drying for the
preservation of biological and pharmaceutical materials. In particular, the invention
relates to a method of lyophilization in which a desired product temperature is
maintained during the primary drying step of the lyophilization method by
modifying the shelf temperature and/or the chamber pressure of the lyophilization
chamber.
Background of the Invention
[0002] Lyophilization or freeze-drying is a process widely used in the
pharmaceutical industry for the preservation of biological and pharmaceutical
materials. In lyophilization, water present in a material is converted to ice during a
freezing step and then removed from the material by direct sublimation under low-
pressure conditions during a primary drying step. During freezing, however, not all
of the water is transformed to ice. Some portion of the water is trapped in a matrix
of solids containing, for example, formulation components and/or the active
ingredient. The excess bound water within the matrix can be reduced to a desired
level of residual moisture during a secondary drying step.
[0003] All lyophilization steps, freezing, primary drying and secondary drying,
are determinative of the final product properties. However, the primary drying step
is typically the longest and most expensive step in the process. Therefore,

optimization of the primary drying step significantly improves both the economics
and efficiency of the lyophilization process.
Summary of the Invention
[0004] Lyophilization is a very efficient but also a very expensive process for
the preservation of biological and pharmaceutical materials. Lyophilization includes
the sequential steps of freezing, primary drying, and secondary drying. The primary
drying step is not only the longest step of the lyophilization process, but it is also the
most sensitive to deviations in process parameters, including the process parameters
of shelf temperature and chamber pressure.
[000S] Current lyophilization methods for biological and pharmaceutical
materials maintain a constant shelf temperature and a constant chamber pressure
throughout the primary drying step. Operation of laboratory-scale lyophilizers,
pilot-scale lyophilizers and commercial-scale lyophilizers is simplified when a
constant shelf temperature and a constant chamber pressure are maintained
throughout the primary drying step.
[0006] It is desirable to decrease the length, and therefore the expense, of the
primary drying step. According to various embodiments of the invention, the length
' of the primary drying step is decreased by maintaining the product temperature of
the material at or just below the target temperature of the material.
[0007] In one aspect, the invention is a method for lyophilizing a material. The
method comprises the step of modifying both a chamber pressure and a shelf
temperature according to a designed primary drying cycle during a primary drying
step.

[0008] In one embodiment, the method further comprises the step of generating
a designed primary drying cycle for a material based on a product temperature
profile for the material. In another embodiment, the method further comprises the
step of calculating the product temperature profile for the material based on the cake
resistance of the material. In a further embodiment, the method further comprises
the step of calculating the product temperature profile for the material based on a
vial heat transfer coefficient. In another embodiment, the product temperature
profile is calculated using product temperature data obtained during a primary
drying step conducted in a laboratory, pilot or commercial lyophilizer.
[0009] In one embodiment, the designed primary drying cycle maintains a
temperature of the material at or below a target temperature of the material. In
another embodiment, the designed primary drying cycle maintains the temperature
of the material within about 15°C of the target temperature of the material. In a
further embodiment, the designed primary drying cycle maintains the temperature of
the material within about 5°C of the target temperature of the material. In another
embodiment, the chamber pressure and the shelf temperature are modified
simultaneously.
[0010] In additional embodiments, the material undergoing the designed primary
drying cycle includes a biological agent, a pharmaceutical agent, a solute having a
concentration of protein in solution in the range of about 1 mg/ml to 150 mg/ml, a
solute having a concentration of protein in solution in the range of about 1 mg/ml to
50 mg/ml, a bulking agent selected from the group consisting of sucrose, glycine,
sodium chloride, lactose and mannitol, a stabilizer selected from the group

consisting of sucrose, trehalose, arginine, and sorbitol, and/or a buffer selected from
the group consisting of tris, histidine, citrate, acetate, phosphate and succinate.
[0011] In further embodiments, the primary drying step of the designed primary
drying cycle is conducted in a commercial-scale lyophilizer, a pilot-scale
lyophilizer, or a laboratory-scale lyophilizer.
[0012] • In another aspect, the invention is an apparatus for lyophilizing a material
comprising a computer-readable medium adapted to record a designed primary
drying cycle, a processor in electrical communication with the computer-readable
medium and adapted to execute the designed primary drying cycle, a chamber
pressure module in electrical communication with the processor and adapted to
modify a pressure of a lyophilization chamber in response to an instruction received
from the processor, and a shelf temperature module in electrical communication
with the processor and adapted to modify a shelf temperature of a lyophilization
chamber in response to an instruction received from the processor.
Brief Description of the Drawings
[0013] In the drawings, like reference characters generally refer to the same
parts throughout the different views. The drawings are not necessarily to scale,
emphasis instead generally being placed upon illustrating the principles of the
invention. In the following description, various embodiments of the invention are
described with reference to the following drawings, in which:
[0014] Figure 1 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a 4.5% sucrose solution
wherein the shelf temperature remained constant at about -27°C and the chamber
pressure remained constant at about 53 mTorr.

[0015] Figure 2 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a material with a 10 mg/ml
protein concentration wherein the shelf temperature remained constant at 0°C and
the chamber pressure remained constant at 50 mTorr.
[0016] Figure 3 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a material with a 50 mg/ml
protein concentration at laboratory scale wherein the chamber pressure remained
constant at about 50 mTorr and the shelf temperature was adjusted during the
primary drying step in order to maintain a product temperature below the critical
value.
[0017] Figure 4 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a material with a 10 mg/ml
protein concentration wherein the chamber pressure remained constant at about 50
mTorr and the shelf temperature was adjusted during the primary drying step in
order to maintain a product temperature below the critical value. A two-step shelf
temperature program is designed for implementation of the lyophilization cycle at
the commercial scale.
[0018] Figure 5 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a material with a 25 mg/ml
protein concentration wherein the shelf temperature remained constant at about
-25°C and the chamber pressure was adjusted during the primary drying step.

[0019] Figure 6 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a material with a 10 mg/ml
protein concentration wherein both the shelf temperature and the chamber pressure
were adjusted during the primary drying step.
[0020] Figure 7 is a graphical illustration of exemplary vial heat transfer
coefficients as a function of the chamber pressure in an exemplary pilot lyophilizer.
[0021] Figure 8 is a graphical illustration of an exemplary designed primary
drying cycle.
[0022] Figure 9 is a graphical illustration of exemplary effects of process
variations on an estimated product temperature profile for a 5% sucrose solution in a
commercial-scale pilot lyophilizer.
[0023] Figure 10 illustrates exemplary data of the effects of process variations
for the 5% sucrose solution in a commercial-scale pilot lyophilizer illustrated
graphically in Figure 9.
[0024] Figure 11 is a schematic representation of a lyophilization apparatus
according to an illustrative embodiment of the invention.
Detailed Description of the Invention
[0025] Lyophilization includes the sequential steps of freezing, primary drying,
and secondary drying. The primary drying step, the longest and therefore most
expensive step of the lyophilization process, is very sensitive to deviations in
process parameters, including the process parameters of shelf temperature and
chamber pressure.

[0026] Current lyophilization methods for biological and pharmaceutical
materials maintain a constant shelf temperature and a constant chamber pressure
throughout the primary drying step, which simplifies the primary drying step of the
lyophilization process. However, constant process parameters of shelf temperature
and chamber pressure throughout the duration of the primary drying step decrease
the efficiency of the primary drying step and increase the cost of the primary drying
step.
[0027] It is desirable to decrease the length, and therefore the expense, of the
primary drying step. According to various embodiments of the invention, the length
of the primary drying step is decreased by modifying the process parameters of shelf
temperature and chamber pressure to maintain the product temperature of the
material at or just below the target temperature of the material throughout the
primary drying step. The product temperature of a material is the temperature of the
material at any given time point during lyophilization. When measured in-time
using a pilot-scale lyophilizer or a laboratory-scale lyophilizer, the product
temperature of a material is often measured at a position within the material just
above the bottom of the vial. The target temperature of a material is the desired
temperature of the material at any given time point during lyophilization and is
about 2-3°C below the collapse temperature of the material. The collapse
temperature of a material is the temperature during freezing resulting in the collapse
of the structural integrity of the material.
[0028] The relationship between heat and mass balance during the primary
drying step are described by the following equation:


[0029] During the primary drying step, the specific heat of sublimation (ΔHs),
the external surface of the vial (Sout), the internal surface of the vial (Sin), and the vial
heat transfer coefficient (Kv) remain relatively constant. However, as water is
removed from the material and as the sublimation front moves gradually from the
top of the vial to the bottom of the vial, the total cake resistance gradually increases
due to the development of a dry layer within the material.
[0030] Cake resistance is the resistance of dry porous material to the flow of
water vapor generated during sublimation. In general, cake resistance depends on
the concentration of solids in the material and the nature of the material undergoing

lyophilization. Cake resistance increases as the concentration of solids in the
material increases.
[0031] However, the solids concentration is not the only factor affecting cake
resistance. Materials subject to lyophilization, including, for example, biological
agents (e.g., proteins, peptides and nucleic acids) and pharmaceutical agents (e.g.,
small molecules), often include bulking agents, stabilizers, buffers and other product
formulation components in addition to a solvent. Exemplary bulking agents include
sucrose, glycine, sodium chloride, lactose and mannitol. Exemplary stabilizers
include sucrose, trehalose, arginine and sorbitol. Exemplary buffers include tris,
histidine, citrate, acetate, phosphate and succinate. Exemplary additional
formulation components include antioxidants, surface active agents and tonicity
components. Formulation components can affect the cake resistance of a material
and, therefore, the process parameters necessary to efficiently lyophilize a selected
material. Exemplary solvents include water, organic solvents and inorganic
solvents. An exemplary material, a 5% sucrose solution, has a lower relative cake
resistance than a mannitol-sucrose buffer having the same solids concentration.
Sucrose is susceptible to partial collapse at temperatures close to -32°C, resulting in
the formation of larger pores and, therefore, less resistance to water vapor flow.
This may account for the relatively small cake resistance of a 5% sucrose solution as
compared to a mannitol-based formulation. As a result, the product temperature of a
5% sucrose solution does not increase more than 5°C during the primary drying step
of lyophilization.

[0032] Figure 1 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a 4.5% sucrose solution
wherein the shelf temperature remained constant at -27°C and the chamber pressure
remained constant at 53 mTorr. According to the.exemplary primary drying step
illustrated in Figure 1, the product temperature of the material in the vial positioned
in the center of the shelf increased from -44°C to -39°C and the product temperature
of the material in the vial positioned at the edge of the shelf increased from -42°C to
-39°C. The exemplary 5°C increase in product temperature is considered small. In
the case of the exemplary 5°C increase in product temperature, the increased
complexity of modifying the shelf temperature and/or the chamber pressure of the
lyophilizer may outweigh the benefits of decreasing the duration of the primary
drying step. Therefore, the process parameters of constant shelf temperature and
constant chamber pressure are reasonable for this material.
[0033] In practice, a 5°C increase in product temperature during the primary
drying step of lyophilization is exemplary of a reasonable rise in temperature.
Therefore, in the case of a 5% sucrose solution, for example, it is not necessary to
change the shelf temperature and/or chamber pressure process parameters during the
primary drying step of lyophilization. Similarly, it is not necessary to change the
shelf temperature and/or chamber pressure process parameters during the primary
drying stage of similar materials with similarly low protein concentration and
relatively small, for example less than 5%, solids concentration.
[0034] However, as the solids concentration in a material increases, for example,
as the protein concentration increases, the cake resistance of the material also
increases. A higher solids concentration also results in a greater increase in product

temperature during a primary drying step wherein the shelf temperature and the
chamber pressure remain constant.
[0035] Figure 2 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a material with a 10 mg/ml
protein concentration wherein the shelf temperature remained constant at 0°C and
the chamber pressure remained constant at 50 mTorr. According to the exemplary
primary drying step of the higher protein concentration material, the product
temperature of the material increased from -40°C to -18°C. The exemplary 22°C
increase in product temperature is considered rather large and economically
unacceptable. Moreover, the product temperature of the material increased above its
target temperature of-20°C. Therefore, maintaining the chosen process parameters
at constant values is considered economically unacceptable for this high protein
concentration material.
[0036] The product temperature of the exemplary higher protein concentration
material illustrated in Figure 2 can be maintained below the target temperature of
-20°C during the primary drying step of lyophilization by resetting the shelf
temperature and/or the chamber pressure process parameters to constant, but
relatively lower, values. Constant process parameters of shelf temperature and
chamber pressure can be calculated using Equation 1 such that the product
temperature never exceeds the target temperature at the end of the primary drying
step. Although selecting a constant shelf temperature and a constant chamber
pressure for lyophilization of higher protein concentration materials or higher cake
resistance materials is a safe and simple solution from a manufacturing perspective,
this method results in a very long and therefore very expensive primary drying step.

[0037] Analysis of Equation 1 suggests, however, that maintaining a constant
shelf temperature and a constant chamber pressure is not the most economical
method of conducting the primary drying step for higher protein concentration
materials or higher cake resistance materials. Alternatively, either and/or both of the
process parameters of shelf temperature and chamber pressure can be modified
during the course of the primary drying step to maintain an optimal product
temperature of a material during the primary drying step.
[0038] A mathematical model can be constructed based on Equation 1. An
exemplary mathematical model describes the relationship between the process
parameters of chamber pressure and shelf temperature, the dry product cake
resistance, the vial heat transfer coefficient, and the product temperature. The
mathematical model can be utilized to calculate a product temperature profile for a
selected material. First, the mathematical model can be used to estimate the product
temperature of a specific material with known product properties at each time point
measurement of the process parameters during the primary drying step. Following
estimation of the product temperature, the sublimation rate at each time point of the
primary drying step can be calculated using the mathematical model and plotted as a
function of time. The total sublimated mass of water at each point of the process can
be estimated by integrating the sublimation rate profile until the calculated value of
sublimated water reaches the total water content of the material. The optimal
product temperature profile can be maintained throughout the course of the primary
drying step for a specific material by manipulating the process parameters of shelf
temperature and/or chamber pressure during the primary drying step.

[0039] According to a preferred embodiment, the mathematical model based on
Equation 1 described above is used to calculate a product temperature profile for a
selected material. Any mathematical model which sufficiently describes the product
temperature profile during the primary drying step can be used to generate the
designed primary drying cycle. A preferred mathematical model calculates a
product temperature profile within 1°C of the actual product temperature and at or
within 2°C below the target temperature of the material during the course of the
primary drying step.
[0040] The product temperature profile obtained in the laboratory, pilot or
commercial primary drying cycle is used to generate a designed primary drying
cycle (based on calculated cake resistance and vial heat transfer coefficients)
wherein the product temperature of the material is maintained at a substantially
constant temperature and at or just below the target temperature of the selected
material during the course of the primary drying step. According to a preferred
embodiment, the designed primary drying cycle maintains the product temperature
of the material within about 1°C of the target temperature during the course of the
primary drying step. According to another embodiment, the designed primary
drying cycle maintains the product temperature of a material with a low collapse
temperature, for example, a collapse temperature of about -30°C, within about 5°C
of the target temperature. An exemplary material with a low collapse temperature is
sucrose. According to another embodiment, the designed primary drying cycle
maintains the product temperature of a material with a relatively higher collapse
temperature, for example, a collapse temperature of about -5°C to -20°C, within
about 15°C of the target temperature.

[0041] The target temperature is also described as the critical temperature of the
material, a temperature about 2-3°C below the collapse temperature of the material.
The critical temperature of a material is the temperature above which distinct liquid
and gas phases do not exist As the critical temperature is approached, the properties
of the gas and liquid phases become the same resulting in only one phase: the
supercritical fluid. Above the critical temperature a liquid cannot be formed by an
increase in pressure, but with enough pressure a solid may be formed. Depending
on the material, the critical temperature of a material can he the same as the collapse
temperature of the material. Maintaining the material at or just below the target
temperature of the material results in the shortest and most efficient primary drying
step.
[0042] According to one embodiment, the product temperature is maintained at'
or just below the target temperature of the material by first increasing the shelf
temperature to the maximum allowed temperature of the lyophilizer. According to
one exemplary embodiment, the maximum allowed temperature of the lyophilizer is
in the range of about -30°C to 6"0°C, more preferably about 0°C to 60°C, and most
preferably about 20°C to 60°C.
[0043] At the initiation of the primary drying step, cake resistance is not a
significant factor in the efficiency of the primary drying rate or sublimation rate; the
product temperature is relatively low; and the product temperature depends, for the
most part, on chamber pressure. As water is removed from the material, product dry
layer begins to form. Beginning at the point when product dry layer begins to form,
the product temperature begins to gradually increase until the product temperature
reaches the target temperature of the material. At the point when the material

reaches its target temperature, either the shelf temperature or the chamber pressure
or both process parameters are simultaneously adjusted to maintain the material at a
temperature at or just below the target temperature of the material.
[0044] Continuing for the remainder of the primary drying step, the shelf
temperature and the chamber pressure are monitored and, optionally and when
necessary, adjusted or modified to maintain the product temperature at or just below
the target temperature of the material. It is understood that the terms adjust or
modify, when applied to a process parameter, contemplate increasing the value of
the parameter and/or decreasing the value of the parameter.
[0045] Figure 3 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a material with a 50 mg/ml
protein concentration wherein the chamber pressure remained constant at about SO
mTorr and the shelf temperature was adjusted during the primary drying step.
According to the exemplary primary drying step wherein the chamber pressure
remained constant and the shelf temperature was modified, the shelf temperature
was gradually increased to about 20°C at a rate of about 1 deg/min. Once the shelf
temperature approached the initial high temperature of about 20°C, the shelf
temperature was maintained at this temperature for about 3 hours. After this period
of drying, the shelf temperature was gradually decreased to maintain the target
temperature of the material at or just below about -10°C.
[0046] Figure 4 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a material with a 10 mg/ml
protein concentration wherein the chamber pressure remained constant at about SO
mTorr and the shelf temperature was adjusted during the primary drying step.

According to the exemplary primary drying step wherein the chamber pressure
remained constant and the shelf temperature was modified, the shelf temperature
was gradually increased to about 0°C. Once the product temperature approached the
target temperature of about -20°C, the shelf temperature was gradually decreased to
about -10°C and maintained at this temperature until the end of the primary drying
step. The product temperature was maintained at or below the target temperature
during the primary drying step.
[0047] Figure 5 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a material with a 25 mg/ml
protein concentration wherein the shelf temperature remained constant at about
-25°C and the chamber pressure was adjusted during the primary drying step.
According to the exemplary primary drying step wherein the shelf temperature
remained constant and the chamber pressure was modified, the chamber pressure
was initially set at a pressure of about 75 mTorr. A chamber pressure higher than
about 50 mTorr was chosen at the beginning of the primary drying step when the
sublimation rate has its highest value. A relatively lower shelf temperature of about
-25°C was chosen at the beginning of the primary drying step, when the cake
resistance is relatively low, to maintain the product temperature below the target
temperature of the material, about -31.4°C. Once the product temperature
approached about -34°C, the chamber pressure was decreased to about 50 mTorr to
maintain the product temperature below the target temperature. During the final
portion of the primary drying step, the chamber pressure was again decreased, to
about 40 mTorr, to maintain the product temperature below the target temperature
for the remainder of the primary drying step.

[0048] Figure 6 is a graphical illustration of the process parameters and material
characteristics of an exemplary primary drying step of a material with a 10 mg/ml
protein concentration wherein both the shelf temperature and the chamber pressure
were adjusted during the primary drying step. According to the exemplary primary
drying step wherein both the shelf temperature and the chamber pressure were
modified, both process parameters were modified simultaneously at three time
points. According to another embodiment, the shelf temperature is modified before
and/or after the chamber pressure is modified.
[0049] Due to sterility requirements and the automation of load and unload
processes in commercial biological and pharmaceutical material lyophilization
facilities, it is not possible to introduce in-time product temperature sensors into
modern commercial-scale lyophilizers. Therefore, it is not possible to monitor the
product temperature and, in response, modify the shelf temperature and/or chamber
pressure to maintain an optimal product temperature profile. However, the
mathematical model can be used to calculate and/or to validate a designed primary
drying cycle for a specific material. A commercial-scale or pilot-scale lyophilizer
then can be programmed according to the designed primary drying cycle to modify
the shelf temperature and/or the chamber pressure by a predetermined change in
value at one or more predetermined time points in the primary drying cycle to
optimize the primary drying step for the selected material.
[0050] During the primary drying cycle, three programmed parameters - shelf
temperature, chamber pressure and time — yield the resulting product temperature
profile. These programmed parameters also affect lyophilizer performance,
including the rate of sublimation and the rate and efficiency of heat transfer from the

shelf to the vial. The optimal process parameters can be measured and/or calculated
using a laboratory-scale lyophilizer with an in-time product temperature sensor to
create a designed primary drying cycle for pilot-scale or commercial-scale
lyophilization of a selected material.
[0051] According to one embodiment, prior to generating in-time process
parameter measurements, product properties of the selected material can be defined.
Exemplary product properties include product water content, liquid product density,
frozen product density, and product cake resistance as a function of dry product
height. Vial properties also can be defined. Exemplary vial properties include vial
filling volume, vial geometry, and vial heat transfer coefficients as a function of
pressure. Lyophilization chamber properties also can be defined. Exemplary
lyophilization chamber properties include the heat radiation from the lyophilizer
walls or door to the product, also known as edge effect.
[0052] Knowing some or all of the above-identified product, vial and/or
chamber properties, additional lyophilization process properties can be calculated
using equations known to one of skill in the art. Exemplary additional properties
that can be calculated include the heat flux through the layer of frozen material at
any given time, the total heat flux for sublimation, the sublimation rate for an
individual vial, the sublimation rate as a function of the primary drying time,
pressure over the sublimation surface, the temperature of the sublimation surface at
various time points in the cycle, the amount of sublimated ice at various time points
in the cycle, the thickness of the frozen layer at the beginning of primary drying and
at various additional time points in the cycle (also described as the cake height), and
the total sublimation cycle time.

[0053] According to a preferred embodiment, a designed primary drying cycle is
created by measuring the process parameters and product properties of a selected
material using an in-time product temperature sensor in a laboratory-scale
lyophilizer over the course of at least one primary drying cycle followed by
optimization of the process parameters according to the mathematical model
described in greater detail above. The primary drying cycle is optimized when the
product temperature of the material is maintained at or just below, within about 1 °C
of, the target temperature of the material during the primary drying step.
[0054] Using the mathematical model, an estimation is created of the product
temperature profile for the subsequent cycles as a function of the process parameters
and product properties throughout the course of the entire primary drying step for
the selected material. Using the product temperature profile estimation and known
characteristics of the pilot-scale or commercial-scale lyophilizer, including vial heat
transfer coefficient and edge effect, a primary drying cycle can be designed for a
pilot-scale or commercial-scale lyophilizer for efficiently lyophilizing a selected
material.
[0055] According to one embodiment, the chamber pressure of a lyophilizer is
adjusted to known values of pressure during the course of at least one primary
drying cycle and a product temperature profile is created by optimizing an
appropriate and optionally adjustable shelf temperature using the mathematical
model. According to another embodiment, the shelf temperature of a lyophilizer is
adjusted to known values of temperature during the course of at least one primary
drying cycle and a product temperature profile is created by optimizing an
appropriate and optionally adjustable chamber pressure using the mathematical

model. According to a further embodiment, a product temperature profile is created
by optimizing an appropriate and optionally adjustable chamber pressure and shelf
temperature using the mathematical model wherein only the product properties of
the material and the vial are known.
[0056] Vial heat transfer coefficients are calculated from the weight loss during
sublimation during a short period of time. Vial heat transfer coefficients can be
calculated using the following equation:

[0057] According to one exemplary lyophilizer, vial heat transfer coefficients as
a function of chamber pressure were measured for three sizes of commonly used
tubing vials, both as vials in the center of the pilot-scale lyophilizer and as vials at
the edge of the lyophilizer. Figure 7 is a graphical illustration of exemplary vial heat
transfer coefficients as a function of the chamber pressure in an exemplary pilot
lyophilizer. In all cases in the exemplary trials, the heat transfer coefficients in the

commercial-scale pilot lyophilizers were lower than the heat transfer coefficients
measured in the laboratory-scale lyophilizers.
[0058] An exemplary designed primary drying cycle was created by inputting
measured values into the mathematical model based on Equation 1, described in
greater detail above. Figure 8 is a graphical illustration of an exemplary designed
primary drying cycle. The predicted product temperature profile based on the
designed primary drying cycle in the commercial-scale pilot lyophilizer was in
agreement with the measured product temperature values during laboratory-scale
lyophilization of the same selected material, validating the designed primary drying
cycle.
[0059] The mathematical model based on Equation 1 was further used to assess
the impact of process deviations on the product temperature profile during the
designed primary drying cycle to assess designed primary drying cycle robustness.
Figure 9 is a graphical illustration of exemplary effects of process variations on an
estimated product temperature profile for a 5% sucrose solution in a pilot-scale
lyophilizer. According to the exemplary embodiments, the heat flux to the edge of
the vials was assumed to be 2-fold higher than for the center vials. Assuming that
the material can tolerate a maximum deviation in shelf temperature of 5°C and a
maximum deviation in chamber pressure of 20 mTorr, two worst case scenarios are
illustrated in Figure 9. The exemplary estimated product temperature profile is
illustrated as the center curve. The upper curve illustrates exemplary edge vials,
which are shown to dry substantially above the target or collapse temperature. The
lower curve illustrates exemplary center vials, which are shown to not complete the
primary drying step at the end of the designed primary drying cycle. Figure 10

illustrates exemplary data of the effects of process variations for the 5% sucrose
solution in a pilot-scale lyophilizer illustrated graphically in Figure 9.
[0060] According to one embodiment, the designed primary drying cycle
modifies shelf temperature at least once during the course of the primary drying
step. According to another embodiment, the designed primary drying cycle modifies
chamber pressure at least once during the course of the primary drying step.
According to a further embodiment, the designed primary drying cycle modifies
each of the shelf temperature and the chamber pressure at least once during the
course of the primary drying step.
[0061] In another aspect, the invention is a commercial-scale lyophilizer, a pilot-
scale lyophilizer, or a laboratory-scale lyophilizer programmed to perform a
designed primary drying cycle for a selected material. Figure 11 is a schematic
representation of a lyophilizer 10 according to an illustrative embodiment of the
invention.
[0062] With reference to Figure 11, according to one embodiment, the
lyophilizer 10 is adapted for lyophilizing a selected biological or pharmaceutical
material (not shown) in a lyophilization chamber 40 and comprises a computer-
readable medium 12, a processor 14, a chamber pressure module 16 and a shelf
temperature module 18. The computer-readable medium 12 is adapted to record a
designed primary drying cycle. The processor 14 is in electrical communication 22
with the computer-readable medium 12 and is adapted to execute the designed
primary drying cycle. The chamber pressure module 16 is in electrical
communication 24 with the processor 14 and is in electrical communication 28 with
the lyophilization chamber 40. The chamber pressure module 16 is adapted to

modify the pressure of the lyophilization chamber 40 in response to an instruction
received from the processor 14. The shelf temperature module 18 is in electrical
communication 26 with the processor 14 and is in electrical communication 30 with
the lyophilization chamber 40. The shelf temperature module 18 is adapted to
modify the shelf temperature of the lyophilization chamber 40 in response to an
instruction received from the processor 14.
[0063] According to one embodiment of the programmed lyophilizer, the
lyophilizer is programmed to modify the shelf temperature at least once during the
primary drying step. According to another embodiment, the lyophilizer is
programmed to modify the chamber pressure at least once during the primary drying
step. According to a further embodiment, the lyophilizer is programmed to modify
each of the shelf temperature and the chamber pressure at least once during the
primary drying step.
[0064] The invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The present
embodiments are therefore to be considered illustrative and not restrictive, the scope
of the invention being indicated by the appended claims rather than by the foregoing
description, and all changes which come within the meaning and range of
equivalency of the claims are therefore intended to be embraced therein.

Claims
1. A method for lyophilizing a material comprising the step of modifying both a
chamber pressure and a shelf temperature according to a designed primary
drying cycle during a primary drying step.
2. The method of claim 1 further comprising the step of generating a designed
primary drying cycle for the material based on a product temperature profile
for the material.
3. The method of claim 2 further comprising the step of calculating the product
temperature profile for the material based on a cake resistance of the
material.
4. The method of claim 2 further comprising the step of calculating the product
temperature profile for the material based on a vial heat transfer coefficient.
5. The method of claim 2 wherein the product temperature profile is calculated
using product temperature data obtained during a primary drying step
conducted in a laboratory, pilot or commercial lyophilizer.
6. The method of any one of claims 1 to 5 wherein the designed primary drying
cycle maintains a temperature of the material at or below a target
temperature of the material.
7. The method of any one of claims 1 to 5 wherein the designed primary drying
cycle maintains a temperature of the material within about 15°C of a target
temperature of the material.
8. The method of claim 7 wherein the designed primary drying cycle maintains
the temperature of the material within about 5°C of the target temperature of
the material.
9. The method of any one of claims 1 to 8 wherein the chamber pressure and
the shelf temperature are modified simultaneously.

10. The method of any one of claims 1 to 9 wherein the material comprises a
biological agent.
11. The method of any one of claims 1 to 10 wherein the material comprises a
pharmaceutical agent.
12. The method of any one of claims 1 to 11 wherein the material comprises a
solute having a concentration of protein in solution in the range of about 1
mg/ml to 150 mg/ml.
13. The method of any one of claims 1 to 12 wherein the material comprises a
solute having a concentration of protein in solution in the range of about 1
mg/ml to 50 mg/ml.
14. The method of any one of claims 1 to 13 wherein the material comprises a
bulking agent selected from the group consisting of sucrose, glycine, sodium
chloride, lactose and mannitol.
15. The method of any one of claims 1 to 14 wherein the material comprises a
stabilizer selected from the group consisting of sucrose, trehalose, arginine
and sorbitol.
16. The method of any one of claims 1 to 15 wherein the material comprises a
buffer selected from the group consisting of tris, histidine, citrate, acetate,
phosphate and succinate.
17. The method of any one of claims 1 to 16 wherein the primary drying step is
conducted in a commercial-scale lyophilizer.
18. The method of any one of claims 1 to 16 wherein the primary drying step is
conducted in a pilot-scale lyophilizer.
19. The method of any one of claims 1 to 16 wherein the primary drying step is
conducted in a laboratory-scale lyophilizer.

20. An apparatus for lyophilizing a material comprising:
a) a computer-readable medium adapted to record a designed primary drying
cycle;
b) a processor in electrical communication with the computer-readable
medium and adapted to execute the designed primary drying cycle;
c) a chamber pressure module in electrical communication with the processor
and adapted to modify a pressure of a lyophilization chamber in response to
an instruction received from the processor; and
d) a shelf temperature module in electrical communication with the processor
and adapted to modify a shelf temperature of a lyophilization chamber in
response to an instruction received from the processor.

A method and apparatus for optimizing the primary drying step of a lyophilization cycle of a biological or pharmaceutical
material. In one aspect, the invention is a method for lyophilizing a material comprising the steps of calculating a designed
primary drying cycle for the material based on a product temperature prOfile for the material and modifying both a chamber pressure
and a shelf temperature according to a designed primary drying cycle during a primary drying step. In another aspect, the invention
is an apparatus (10) for lyophilizing a material according to a designed primary drying cycle comprising a computer-readable
medium (12), a processor (14) in electrical communication with the computer-readable medium (12), a chamber pressure module
(16) in electrical communication with the processor (14), and a shelf temperature module (18) in electrical communication with the
processor (14).