Learning Objectives

Major Problems of Protein Drugs

• High Molecular Weight:

  • Large molecules increase difficulty in cellular uptake.

• Poor Stability:

  • Native biologically active structure maintained by weak noncovalent forces; easily disturbed by mild manufacturing or storage conditions.

• Factors Affecting Stability:

  • Temperature

  • pH

  • Humidity

  • Ionic Strength

  • Enzymes

  • Mechanical Forces: pressure, shearing, and shaking.

Protein Folding

• Definition:

  • Physical process where linear polypeptides fold into their 3D structure.

• Initial State:

  • Proteins start as unfolded polypeptides (random coils) post translation from mRNA.

• Folding Process:

  • Amino acids interact to produce a well-defined native state.

• Importance of 3D Structure:

  • Correct folding is essential for functionality; improper folding leads to inactive proteins.

Physical & Chemical Instability of Protein Products

• Physical Instability:

  • Changes in secondary, tertiary, or quaternary structures.

• Chemical Instability:

  • Formation of new chemical entities via bond cleavage or formation.

• Examples of Instability:

  • Aggregation, hydrolysis, surface adsorption, oxidation, precipitation, deamidation, and disulfide exchange.

How to Stabilize Protein Formulations?

• Avoid Degradation Factors:

  • Physical and chemical factors that lead to instability (e.g., pH, temperature, enzyme activity).

• Natural Conditions:

  • Proteins stabilize better in environments resembling their natural habitats.

• Additives:

  • Use stabilizers to maintain native protein structure, reducing aggregation risk.

• PEGylation:

  • Addition of polyethylene glycol (PEG) to improve stability.

• Nanotechnology Formulation:

  • Use of nanoparticles for stabilization.

  • Examples include protein encapsulation and adsorption on nanoparticles.

Storage of Protein Drugs

• Solution State:

  • Unstable and requires storage at -30°C to -80°C (-22F to -112F), complicating handling and transportation.

• Dried Form Advantages:

  • Stable even at room temperature, easier for transportation, and more cost-effective.

How to Get Dried Form of a Protein Product?

• Need for Dry Formulation:

  • Aqueous liquid forms are unstable and have limited shelf life, often requiring freezer storage.

• Drying Methods:

  • Spray Drying

  • Freeze Drying (Lyophilization)

The Spray Drying Process

1. Solution Feed:

   • Pumped as a fine droplet mist into drying chamber via an atomizer.

2. Droplet Drying:

   • Liquid evaporates rapidly after atomization.

3. Dry Powder Formation:

   • Formed in the drying chamber by heated gas; particles fall for collection.

4. Cyclone Separator:

   • Induces separation of powder from air, collecting the final powder product.