Using Hansen Solubility Parameters to predict excipient impacts on drug packaging and delivery devices
The drug and packaging industries have always been extremely conscientious to ensure that anything added to a delivery device to improve performance (e.g., silicone oil used to coat the inner surface of a syringe barrel), does not affect a drug’s efficacy or safety. But what about the converse? How do we make sure that the drug, or more specifically its added excipients, does not affect the delivery system’s performance? The term excipient refers to any member of a broad group of surfactants, preservatives, tonicity agents, and buffers which formulation scientists take great care to balance in order to provide the drug, such as a therapeutic protein, in its most effective and deliverable state.
Theoretical calculations based on Hansen Solubility Parameters (HSP) can provide insight into how much an excipient will interact with delivery system materials such as silicone oil. Using the principle that “like dissolves like”, HSP calculations determine how “alike” two materials are, and by extension, how likely an excipient, or combination of excipients, will be to interact with (and potentially remove) a coating such as silicone oil.
West’s Scientific Insights Lab (SIL) has demonstrated that comparing HSP calculations, in addition to data from experimental methods such as contact angle and interfacial tension, finds a strong correlation with excipients which have a shorter HSP distance from silicone oil (and as such would be more likely to interact) with those contained in syringes which showed inconsistent break-loose and glide forces. This indicates that HSP analysis can be employed proactively to predict and avoid potential issues, and further promote more effective use of experimental resources.
Besides the physical interactions between the excipients and silicone oil, the degradation of excipients due to the chemical interactions between the excipients such as histidine and polysorbate could also impact syringe functionality. Thus, physicochemical excipient-container interactions in prefilled syringes need to be understood to have a holistic view of their impact on syringe functionality. The details of the above discoveries can be found in a recently published journal paper by Dr. Liang Fang and his coauthors in the PDA Journal of Pharmaceutical Science and Technology, titled “Physicochemical Excipient-Container Interactions in Prefilled Syringes and Their Impact on Syringe Functionality”.
Dr. Fang and the scientists in the SIL have been developing applications using HSP calculations for over four years. The ability to predict the interactions between excipients, and even the drugs themselves, and any component with which they come into contact, means that formulation and packaging scientists can more quickly narrow down what will or will not work for their drug. This can both expedite the development phase and cut down on resources needed to find a successful formulation. It can also enable an easier transition from vial system to PFS, since knowing whether or not a drug requires an excipient which is incompatible with, for example, silicone oil, will enable decisions on what type of syringe to use. We are just beginning to understand the implications this could have for de-risking a drug as it begins these parts of its lifecycle. For a deeper dive into what West has been doing in this area, see below a list of related works, both published in peer-reviewed journals and presented as part of West’s extensive engagement with the industry.
*Compatibility Risk of Drug Formulation and Syringe/Autoinjector Functionality
In an investigation presented at the 2018 PDA Universe of Pre-Filled Syringes (Risk of Drug Formulation and Syringe / Autoinjector Functionality) it was demonstrated using HSP calculations, along with experimental methods such as contact angle and interfacial tension, that there was a correlation between observed inconsistencies observed in syringe glide forces and excipients that were predicted to have a higher likelihood to interact with silicone oil.
For the link to the full presentation, please click here.
*Protein Adsorption Explained by Hansen Solubility Parameters
In a poster presented at PepTalk 2018 conference, it was demonstrated that the amount of bovine serum albumin (BSA) protein adsorption on different polymer surfaces can also be predicted by HSP. Interestingly, the calculated HSP of the adsorbed BSA is different than that of native BSA and indicates that adsorbed BSA is more hydrophobic. This observation suggests that BSA molecules which are adsorbed may be partially denatured, exposing their hydrophobic core toward polymer surfaces. The model in this study could be used to predict the amount of protein adsorption on a polymer or any other solid surface if the HSP of that surface is known.
Click here for the full poster.
This work was also peer-reviewed and published the Journal of Pharmaceutical Sciences (Model Protein Adsorption on Polymers Explained by Hansen Solubility Parameters. January 2019, v. 108, Issue 1, p 187-192) Click here for the free full-length text.
Modeling the Permeation Rates of Organic Migrants Through a Fluoropolymer Film. PDA Journal of Pharmaceutical Science and Technology. August 29, 2018
The work presented here uses HSP to better understand the barrier properties of a model ETFE fluoropolymer film. This model may be used to facilitate expedited screening of potential leachables, allowing for experimental focus on higher-risk leachables and ultimately enabling more rapid combination drug product development.
Click here to be redirected to the abstract on the PDA journal site (Requires PDA login for full article)
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