Modern biotechnology is increasingly creating new medicines that are large molecules (e.g. peptides, proteins). Often these biomolecules are sensitive to heat, requiring refrigeration which limits widespread availability and use outside of a hospital setting. In addition, many of these agents can only be delivered by injection, yet do not dissolve easily.
For ease of preparation, cost containment by the manufacturer and ease of handling for the end user an aqueous protein formulation in solution is often preferred. However, transportation costs for these liquid formulations are high and proteins are readily denatured (often irreversibly) if they are not transported by cold chain (i.e. refrigerated). This is because denaturation is also caused by agitation, freezing, pH changes and exposure at interfaces. The practical solution to this dilemma is to remove water and there are numerous drying technologies that can be used to prepare dehydrated biopharmaceuticals. Each has advantages and disadvantages, which are summarised in the table below.
Currently, the most commonly used drying technology is freeze drying (also known as lyophilisation). However, the shear forces and temperatures used in the system, as well as the long and complex cycle times, mean that fragile biomolecules are often damaged and irreversibly denatured as a result of the process itself. Ultimately, the result is a decreased level of activity retained after processing, and sometimes a complete loss of activity because the molecule is unable to reconstitute to its natural state. This compromises clinical efficacy and increases the risk of adverse side effects. Even if physical stability is maintained, a protein can degrade by chemical reactions (e.g. hydrolysis, deamination), which can be mediated by the presence of water.
Crystec mSAS supercritical fluid (SCF) technology offers a viable, single-step alternative to lyophilisation and other conventional drying processes. The mSAS technology employs mild processing conditions such as low process temperatures (40°C) and has no shear forces or interfacial stress. In addition, the pressure and contact time with organic solvent typically used in the system, has been proven to not be damaging to many biopharmaceutical products. Furthermore, the mSAS process facilitates the use of stabilising, buffering and bulking agents to aid ‘in process’ and ‘post process’ stability.
Key areas where mSAS can add value to biopharmaceutical product development:
- • Enhanced levels of retained activity
- • Improved ease of reconstitution
- • Ability to ‘tune’ the percentage of water remaining in the dry powder
- • Room temperature stable powder formulations
- • Opportunities for new routes of administration (e.g. nasal or inhaled)
mSAS Case Studies
The example case studies below demonstrate some of the key areas where mSAS drying technology can be applied to overcome the challenges associated with biomolecule processing.
Target Product Profile: An inhalable formulation of leuprolide suitable for use in a metered dose inhaler.
Outcome: The resulting inhaled particles showed a similar pharmacokinetic profile to that of an intravenous bolus injection in a non-optimised system. Bioavailability achieved was 17% +/- 3%, compared to 8% for an equivalent conventionally prepared product.
Buffer Stabilisation of Plasmid DNA
Target Product Profile: Retain the supercoiled structure of plasmid DNA after mSAS processing.
Outcome: For some biopharmaceutics, low pH can be detrimental, and plasmid DNA is one such molecule. The data below shows that pH can be controlled within the SCF system, minimising damage to pH sensitive biomolecules. The use of a pH buffer system led to an increase of the recovery of the active supercoiled proportion of DNA from 7% to 80%
Stable insulin particles produced by mSAS
Target Product Profile: Stable insulin particles with an acceptable level of retained activity
Outcome: Insulin particles were successfully processed by mSAS whilst retaining activity. The data below demonstrates that SCF processed insulin remained stable for >12 months and had acceptable potency, high molecular weight protein aggregates (%HMWP) and oligomer (%).