Measuring the specific surface area (SSA) of freeze-dried biologics using inverse gas chromatography

Enhanced Stability of Vegetal Diamine Oxidase with Trehalose and Sucrose as Cryoprotectants: Mechanistic Insights

Enteric dysfunctions are common for various histamine-related intestinal disorders. Vegetal diamine oxidase (vDAO), an enzyme able to decompose histamine and thus alleviate histamine-related dysfunctions, was formulated in gastro-resistant tablet forms for oral administration as a food supplement and possible therapeutic agent. A major challenge for the use of proteins in the pharmaceutical field is their poor stability. In this study, vDAO was freeze-dried in the absence or in the presence of sucrose or trehalose as cryoprotectants and then formulated as tablets by direct compression. The stability of the obtained preparations was followed during storage at 4 °C and -20 °C for 18 months. In vitro dissolution tests with the vDAO powders formulated as tablets were performed in simulated gastric and in simulated intestinal fluids. The tablets obtained with the powder of the vDAO lyophilized with sucrose or trehalose cryoprotectants offered better protection for enzyme activity. Furthermore, the release of the vDAO lyophilized with the cryoprotectants was around 80% of the total loaded activity (enzyme units) compared to 20% for the control (vDAO powder prepared without cryoprotectants). This report revealed the potential of sucrose and trehalose as cryoprotectants to protect vDAO from freeze-drying stress and during storage, and also to markedly improve the vDAO release performance of tablets obtained with vDAO powders.

Determination of BET Specific Surface Area of Hydrate-Anhydrate Systems Susceptible to Phase Transformation Using Inverse Gas Chromatography

Specific surface area (SSA) is an important parameter in drug development that affects other downstream pharmaceutical properties of interest such as reactivity, stability, dissolution, and ultimately bioavailability. Traditionally, the Brunauer-Emmett-Teller (BET) SSA of pharmaceutical powders is measured via gas adsorption (nitrogen or krypton) that is preceded by a prolonged degassing step under low pressure. This degassing step may not be suitable for certain pharmaceutical hydrates that are susceptible to dehydration and phase transformation under reduced pressure and humidity conditions. Therefore, inverse gas chromatography (IGC) was explored as a reliable alternate technique for determining the SSA of model anhydrate-hydrate systems (trehalose and thiamine hydrochloride) that are prone to such phase transformation during SSA measurement. Both trehalose dihydrate and thiamine HCl non-stoichiometric hydrate were found to undergo partial phase transformation to anhydrous forms during BET analysis via degassing and gas adsorption. In contrast, these hydrates remained stable during surface area analysis using IGC owing to measurements under controlled relative humidity. Thus, IGC proved to be a viable technique for SSA measurement of pharmaceutical hydrates without compromising their physical stability.

The Influence of Moisture Content and Temperature on the Long-Term Storage Stability of Freeze-Dried High Concentration Immunoglobulin G (IgG)

High protein concentration products for targeted therapeutic use are often freeze-dried to enhance stability. The long-term storage stability of freeze-dried (FD) plasma-derived Immunoglobulin G (IgG) from moderate to high concentrations (10-200 mg/mL) was assessed. Monomer content, binding activity and reconstitution times were evaluated over a 12-month period under accelerated and real-term storage conditions. In the first case study it was shown that FD IgG from 10 to 200 mg/mL had minimal monomer/activity losses at up to ambient temperature after 12 months of storage. However, at 45 °C the sucrose-to-protein ratio played a significant impact on IgG stability above 50 mg/mL. All IgG concentrations witnessed moisture ingress over a 12-month period. The impact of moisture ingress from environmental exposure (between 0.1% and 5% w/w moisture) for IgG 50 mg/mL was assessed, being generated by exposing low moisture batches to an atmospheric environment for fixed time periods. Results showed that at -20 °C and 20 °C there was no significant difference in terms of monomer or antigen-binding activity losses over 6 months. However, at 45 °C, there were losses in monomer content, seemingly worse for higher moisture content samples although model binding activity indicated no losses. Finally, the difference between a low moisture product (0.1-1% w/w) and a moderately high moisture (3% w/w) product generated by alternative freeze-drying cycles, both stoppered under low oxygen headspace conditions, was evaluated. Results showed that at -20 °C and 20 °C there was no difference in terms of binding activity or monomer content. However, at 45 °C, the low moisture samples had greater monomer and binding activity losses than samples from the highest moisture cycle batch, indicating that over-drying can be an issue.