LYOPHILIZATION - Lyophilization Cycle Development: Lessons Learned & Pitfalls to Avoid

INTRODUCTION

The global lyophilization market for pharmaceutical and biotechnology products, valued at $1.97 billion in 2014, is expected to increase to $2.66 billion by 2019, with a compound annual growth rate (CAGR) of 6.2%.¹ About 25% of new injectable drugs, vaccines, and biological products are formulated in a lyophilized form, and for many proteins, peptides, and vaccines, this represents the preferred way to produce stable, biologically active products with a long shelf-life.²

Lyophilization involves manipulating the temperature and pressure of the solution so that the phase of the solution can move directly from the frozen state to the gaseous state without moving through the liquid phase/state. This is achieved by cooling the solution and lowering the pressure to below the triple point of water (the temperature and pressure at which water can exist in equilibrium in the liquid, solid, and gaseous states – which is 0.01°C (Figure 1). This allows for the removal of the solvent from the product without subjecting the product to intense heat.

There are four steps in the lyophilization cycle:⁴

Freezing: Creates the ice matrix that holds the drug substance and other excipients. On the triple point graph (Figure 1), the product is in the liquid phase, the temperature is lowered, and the product is frozen.
Evacuation: Reduces pressure below the vapor pressure of ice. A vacuum is used to reduce the pressure in the lyophilizer to below the triple point of water.
Primary Drying: Adds heat to drive the sublimation of water vapor from the ice onto the freeze dryer condenser coils. The addition of heat moves the product from the frozen or solid state to the gaseous state, therefore removing “free ice.”
Secondary Drying: Adds heat to drive off unfrozen water that is bound to the interstitial surface area of the cake.

BENEFITS, EXAMPLES & HISTORY

The advantages of lyophilization include:⁵

-Enhanced product stability in a dry state
-Enhanced stability of a dry powder
-Ease of processing a liquid as opposed to a powder fill, which simplifies aseptic handling
-Removal of water without excessive heating of the product
-Rapid and easy dissolution of reconstituted product

Examples of products made using lyophilization include coffee, ice cream, camping foods, dried flowers, and pharmaceuticals. Many parenteral products, including anti-infectives and biotechnology-derived products, and in vitro diagnostics, are manufactured as lyophilized products.⁶ Drugs must typically be stable for more than 2 years on the shelf; however, some programs need shelf-lives of 10 years or more for products intended for strategic stockpiles.

DEFINING THE DESIGN SPACE

A representation of a design space is provided in Figure 2. Here, all the parameters that define the manufacturing process (compounding, filling, lyophilization, capping, inspection, packaging, and product elegance) are encompassed in the blue, which shows the conditions where the product will meet the release specifications. The ideal target, shown as a black circle, is the area that gives the most leeway to account for any process variability. In contrast, the white circle represents a design space that allows little leeway. Here, there is the risk that nuanced differences between manufacturing sites or between scale-up activities could take the process outside of the acceptable design space, resulting in a potential failure or lost batch.

Patheon uses a series of six lyophilization runs to help define the design space. The first lyophilization run cycle parameters are based on initial input from the client, and this run is designed to evaluate how the lyophilization cycle works within the Patheon systems. The next four runs are used to examine various combinations of high and low temperatures and pressures. The evaluation of the data collected from the lyophilization runs, and the supporting analytical data define the ranges of the lyophilization cycle parameters.

Data from the lyophilization run can include:

-Thermocouple data on shelf temperature versus product cake temperature
-Pirani gauge data, measuring the vapor pressure of the sublimation process
-Pressure rise testing, used to indicate the amount of remaining unsublimated water

The data gathered are evaluated to demonstrate there is no change in the assay, the impurity profile, the residual moisture in the cake, and the reconstitution properties.

One of the lyophilization runs incorporates a Pmax test, where pressure is increased so that sublimation is no longer the driving force. This test provides evidence that even if a pressure excursion occurs during the manufacturing process, there will be data to support the fact that there is no impact on the batch.

Based on the data from these first runs, a final run is designed to evaluate the scale up of the cycle and to run the largest batch possible in the development area, prior to transferring this to the manufacturing facility. The product from this final run should represent the same operating parameters as the good manufacturing practice (GMP) or scale-up lyophilization product. The parameters of manufacturing for this final batch should also represent the manufacturing parameters for the GMP batch manufacturing.

A ROADMAP TO GMP MANUFACTURING

Key factors for pharma companies to take into account for successfully transferring development-scale projects into GMP production include the need for:

1.  A thorough understanding of the active pharmaceutical ingredient (API), including factors such as the density, viscosity, moisture load, form (for example, amorphous or crystal), particle size, solubility, stability, and any available differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) data and material interaction studies. If the product is being supplied as a bulk drug substance, product solution handling characteristics to consider include: viscosity, solution appearance, and the possibility of solution foaming or bubbling during the filling process in manufacturing. An additional question is whether the analytical methods have been validated or only qualified, and whether they are appropriate for the goals of the program.

2.  Information on the development and clinical programs for the product. To anticipate program supply needs, it is important to account for samples for test validation, stability programs, and clinical needs. Details of whether a placebo is needed, and if so, whether this has to be blinded, are also important to consider in the decision-making process for the development or transfer of a product or process.

3.  Confirmation of whether non-GMP API is being used to start development activities, and if so, whether major changes are expected to the synthesis route. Such changes could impact the characteristics of the API. These differences could include polymorph differences, particle size, or moisture content, for example.

4.  If the lyophilization cycle is appropriate for the product’s phase of development. For early phase products, a more conservative approach is acceptable, and because API is often extremely expensive and in short supply, a more conservative lyophilization cycle can mitigate the risk in production. In later development, life cycle optimization studies are carried out to develop well-characterized and robust approaches, including a more detailed design of experiments (DOE) studies. In some cases, a hybrid of the two approaches may be appropriate.

5.  A suitable design space, with the target close to the center of the blue circle in Figure 2, providing some flexibility to account for process variations.

6.  The need for product elegance, which may not be an issue for Phase 1 studies in one region, for example, but may be a major factor if the product is to be used in another region. Understanding these nuances can impact the development plan for a product.

7.  An experienced contract development and manufacturing organization (CDMO) partner with the ability to handle a product from the earliest stages of development through to commercialization, based on a wide range of lyophilization capacities at a single physical location. The ability to transfer projects internally from small scale to commercial manufacturing minimizes the risk to the technical transfer of the program.

SUMMARY

Based on Patheon’s experience with more than 300 client development projects, of which approximately half were lyophilization development programs, it is clear that success in lyophilization transfer and scale-up projects depends on a structured approach to information sharing between a pharma company and its CDMO partner. For both small and large molecule biopharmaceutical products, this should include extensive details about the APIs or bulk drug substance characteristics and planned development and clinical programs. The lyophilization program should also define an appropriate cycle and suitable design space for each product. Using this transparent and well-defined approach to the development, scale-up, or technical transfer of the project will mitigate risk, minimize re-working costs, and optimize the results of the transfer process.

REFERENCES

1. Markets and Markets press release: Freeze Drying Market worth $2,655.9 Million by 2019. September 2014. Website visited: http://www.marketsandmarkets.com/PressReleases/freeze-drying-lyophilization-equipment.asp.
2. Website visited: http://www.purdue.edu/newsroom/releases/2015/Q3/purdue-to-advancefreeze-drying-technology-through-rocket-science.html.
3. Website visited: https://www.fda.gov/iceci/inspections/inspectionguides/ucm074909.htm.
4. Website visited: http://images.info.patheon.com/Web/Patheon-Inc/%7B00312410-dc85-4850-8b12-81e302aef362%7D_Cycle-Development-Basic-Concepts-and-Optimizing-the-Process.pdf.
5. Website visited: https://www.fda.gov/iceci/inspections/inspectionguides/ucm074909.htm.
6. Website visited: https://www.fda.gov/iceci/inspections/inspectionguides/ucm074909.htm.
7. Website visited: http://serc.carleton.edu/research_education/equilibria/phaserule.html.
8. Website visited: https://www.youtube.com/watch?v=vFa2J9V2gE.
9. Website visited: https://www.youtube.com/watch?v=vFB

John W. Burke is Manager, Pharmaceutical Process Technologies – Steriles (PPT), at Patheon. Here, he leads a group of eight scientists at Patheon’s Greenville, NC, site, facilitating the development and technical transfer of pharmaceuticals through all phases of development. He has more than 23 years of experience in the pharmaceutical industry, and started his pharmaceutical career in the analytical laboratory, supporting a wide range of products and testing techniques. His laboratory experience includes raw material testing, flame atomic adsorption, GC, and HPLC. He then transitioned into formulation development, supporting both NDA and ANDA programs for parenteral and lyophilized products. Mr. Burke successfully transferred multiple projects to both internal and external manufacturing facilities. He earned his Bachelor of Science in Chemistry from Pfeiffer College, now Pfeiffer University, and earned a Master of Science in Chemistry at the University of North Carolina – Wilmington, where he synthesized multiple salts using a model drug and evaluated the effects of the new salts on lyophilization cake characteristics.