Modeling critical parameters of the intramuscular injection site
Lead Research Organisation:
University of Bath
Department Name: Pharmacy and Pharmacology
Abstract
Novel parenteral delivery technologies including long acting injection depots and intradermal devices have become
increasingly important to formulation strategies to optimize drug efficacy while minimizing injection frequency. At
present, in vitro tools fail to accurately model in vivo performance for these various parenteral routes, particularly for
intra-muscular (IM) injections. Such bio-predictive tools would help guide scientists towards optimal formulation
preparation and would help reduce reliance on preclinical in vivo data which is costly to generate, delays the product
development cycle, and too often, is not predictive of clinical results. Studies in the laboratory of Professor Mrsny at
the University of Bath have led to the development of a novel method (Scissor) to simulate physiological dynamics of
the hypodermis, the site of subcutaneous injections. GSK has funded a PhD studentship for me, Adam McCartan, to
support the identification of parameters that control drug fate at an IM injection site with the goal of setting up a tool
similar to the Scissor system. I will receive multi-disciplinary training in a highly-applied environment, and be actively
involved in knowledge transfer between the University of Bath and GSK.
increasingly important to formulation strategies to optimize drug efficacy while minimizing injection frequency. At
present, in vitro tools fail to accurately model in vivo performance for these various parenteral routes, particularly for
intra-muscular (IM) injections. Such bio-predictive tools would help guide scientists towards optimal formulation
preparation and would help reduce reliance on preclinical in vivo data which is costly to generate, delays the product
development cycle, and too often, is not predictive of clinical results. Studies in the laboratory of Professor Mrsny at
the University of Bath have led to the development of a novel method (Scissor) to simulate physiological dynamics of
the hypodermis, the site of subcutaneous injections. GSK has funded a PhD studentship for me, Adam McCartan, to
support the identification of parameters that control drug fate at an IM injection site with the goal of setting up a tool
similar to the Scissor system. I will receive multi-disciplinary training in a highly-applied environment, and be actively
involved in knowledge transfer between the University of Bath and GSK.
| Description | ECM-modelling hydrogel The goal of my project is to develop a hydrogel (a liquid-based gel) with physicochemical properties that are sufficiently similar to the extracellular matrix (ECM; a structural network that supports the physical arrangement of tissues) of the skeletal muscle tissue to provide an "in vitro" system (i.e. an artificial environment) to model the "fate" of drugs administered by intramuscular (IM) injection (injections into skeletal muscle tissue). Such a system can be used to model potential interactions between an injected drug and this ECM to predict the "fate" of an injected medicine (whether a drug diffuses into the body rapidly or slowly, for example). As such, we have designed our IM/ECM-mimicking hydrogels to incorporate structural protein elements present in the ECM of the IM injection site to make them bio-relevant. We also have considered practical aspects of such an IM/ECM-mimicking hydrogel, selecting materials and processes that will allow for their long-term storage and ease of use by researchers and that only requires equipment commonly found in pharmaceutical research laboratories. Hydrogel design In modelling human tissue structures relevant to the IM injection site, it would be considered sensible to use human-origin materials in the IM/ECM-mimicking hydrogel. However, human tissues incur significant ethical, health & safety and financial implications. Through computer-based analysis methods, we have found that highly similar structural proteins of animal origin (which are readily available commercially) are suitable alternatives. We will be testing these materials in the IM/ECM hydrogel format "in vitro". Raman probe for drug monitoring All drugs administered by injection involve a formulation designed to stabilise and ultimately release that molecule into the body via the bloodstream. There are currently no defined methods to follow the "fate" of these drugs after IM injection. The IM/ECM-mimicking hydrogel will provide an important "in vitro" tool to follow the "fate" of a drug in a format that models injection of a drug formulation. The physicochemical properties of the IM/ECM-mimicking hydrogel limit the value of potential "monitoring" methods such as light absorbance measurements and other methods that have been used in a comparable "in vitro" model to assess subcutaneous injections (injections below the skin). We have demonstrated that Raman spectroscopy (a laser-based technology) can be used to specifically detect a drug in the complex and opaque environment of our IM/ECM-mimicking hydrogel. More detailed experiments would optimise Raman spectroscopic methods to quantitatively measure changes in drug concentration over time, allowing modelling of drug "fate" within the IM/ECM-mimicking hydrogel. However, due to difficulties associated with the COVID pandemic, this area of research was unable to proceed beyond early stages. However, the little work we were able to accomplish indeed demonstrated that Raman spectroscopy would be suitable for the "in vitro" tool, provided future work in e.g. post-doc positions could be undertaken. New knowledge of drug "fate" Drug "fate" following injection is controlled by potential interactions with the IM/ECM environment and the properties of the formulation that has been injected. The "in vitro" IM injection model being developed will have immediate applications to explore novel formulation approaches to improve the "fate" of drugs that are currently approved for IM injection. Therefore, we sought to effectively demonstrate how this novel testing could be applied in developing novel formulations. To this end, have studied the impact of drug electrostatic charge and formulation components on drug fate. A simplistic testing system was developed around a 5mL hydrogel (consisting of either positively-charged collagen type 1 (Col1) and negatively-charged hyaluronic acid (HYA), or Col1 only) submerged within a physiological salt buffer solution. Any materials injected into the hydrogel must diffuse through the gel matrix before being released into the buffer solution, thereby modelling drug release from the IM injection site into the systemic circulation. Green fluorescent protein (GFP) is bright green molecule that is easily visible to the naked eye, allowing simple visual assessment of the drug after injection. Furthermore, it is simple to generate "supercharged" versions that are either strongly positively charged or strongly negatively charged. GFP, therefore, was an ideal research tool to study how injected materials interact with the hydrogel environment. It was observed that the positively-charged GFP diffused through the matrix at a markedly reduced rate compared to negatively -charged GFP and non-modified GFP. This shows the potential impact that charged drugs may have after injection, affecting the rate of release into the human bloodstream. Such an outcome as for positively charged-GFP would be suitable for highly concentrated drug doses meant for once-monthly administration, for example. Furthermore, removing negatively-charged HYA from the hydrogel resulted in further modification of the GFP diffusion rates. This type of data demonstrates how specific questions about the IM injection site can be addressed; this has begun to unveil potential HYA-specific effects on drug fate in human skeletal muscle. Then, we combined the GFP variants with histidine, acetate or polysorbate 20 (PS20). Histidine is a positively charged component used in medicines to maintain correct pH during storage. Acetate, a negatively charged component, performs a similar role. PS20, known as a "surfactant", is commonly used to prevent drug degradation events at air-liquid and glass-glass interfaces in storage vials. The data from these GFP "formulation" experiments was compared to the "GFP-only" experiment data. It was found that the "formulations" further modified the diffusion of the GFP variants in both Col1/HYA and Col1-only hydrogels. Such data indicates how the parameters of electrostatic charge and formulation components can affect drug fate after injection into patients. We then challenged the in vitro tool with a clinically approved, hydrophobic pharmaceutical, provided by our industrial partners. We have been provided with three distinct formulations of the same drug, each with a distinct rate of release. The in vitro tool could discriminate between the three formulations, in terms of rate of drug release into the sink environment surrounding the hydrogel injection site. This assay was also performed with the addition of bovine serum albumin (BSA) to the hydrogel and buffer systems. BSA is akin to albumin found in human tissue fluids, including interstitial fluid. BSA can aid transport of hydrophobic drugs, such as our model drug. These experiments determined that the inclusion of a model soluble lipoprotein indeed affected drug release outcomes, when compared to data generated in the absence of BSA. The findings we generated indicated the value that this kind of tractable in vitro tool can bring to pharmaceutical research. By better understanding the relationship between a drug/formulation and the IM environment, this permits researchers to make better, informed decisions during research programmes. This can then lead to better chances of successful drug development in shorter timescales, expediting research and reducing the current dependence on in vivo testing. The corporate sponsor was satisfied with our end-results, and approved my transfer from active lab work to "writing up", in order to complete, and subsequently defend, my thesis. |
| Exploitation Route | Our laboratory previously developed an "in vitro" model of the subcutaneous site, known as the SCISSOR, to assess injected drug formulations. The SCISSOR, commercialised by Pion Inc, has been adopted into industry, being used by both industrial and academic labs interested in pharmaceutical development. We were approached by industry, with the request to develop a similar tool to assess IM injectables and model pharmacokinetic outcomes. Based upon enthusiasm and feedback from industrial collaborators, there is continued and expanding interest in this approach. We believe additional development for this technology will be supported through a combination of funding strategies. Industrial partnerships will likely be used to expand our understanding and extent of opportunities for the technology in the context of pharmaceutically relevant drugs. We also believe future funding will come from sources designated to reduce animal testing (e.g. NC3Rs), which actively support such "in vitro" model development. Finally, we have had discussions with Pion, the company that commercialised the SCISSOR system, regarding the development of a similar commercial system that would utilise the IM/ECM-mimicking hydrogel model. They continue to be interested as a potential commercialisation partner, with our immediate goal being to acquire more data using this model to enhance the nature and expanse of this relationship. The previous experience in our group from commercialising the SCISSOR system puts us in a good position to know how to successfully work with a commercial partner and to understand their motivations in the identification of a commercially viable approach that can be marketed as a cost-effective, user-friendly product. Although the system we desired to develop has not been fully realised, a grant is in preparation to continue this work as a Post-doc programme at the University of Geneva, Switzerland. Pion have expressed their continued interest and, pending the results of the post-doc programme, are willing to commercialise the in vitro tool. Overall, the work that has been conducted with e.g. GFP can be applied in research settings to better anticipate/predict drug performance prior to clinical trials, streamlining the research process and increasing the rate of successful drug development. |
| Sectors | Healthcare,Pharmaceuticals and Medical Biotechnology |
| Title | Dataset for "Modelling intramuscular drug fate in vitro with tissue-relevant biomimetic hydrogels" |
| Description | Data associated with the article "Modelling intramuscular drug fate in vitro with tissue-relevant biomimetic hydrogels", published in the International Journal of Pharmaceutics: X. |
| Type Of Material | Database/Collection of data |
| Year Produced | 2022 |
| Provided To Others? | Yes |
| Impact | N/A |
| Description | Controlled Release Society conference, Montreal, Canada, 2022 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | International conference in Canada, presenting my work using GFP as a model macromolecule, to the international pharmaceutics community. Garnering interest from industrial figures/representatives. |
| Year(s) Of Engagement Activity | 2022 |
| Description | Presentation for the Controlled Release Society |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | I was invited to present my work as a video powerpoint presentation at the online conference of the Controlled Release Society. |
| Year(s) Of Engagement Activity | 2020 |
| Description | Presentation to GSK Research Group |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | The purpose was to inform a wider industrial audience about the progress made in developing "in vitro" alternatives to typical "in vivo" testing methods for novel therapeutics. |
| Year(s) Of Engagement Activity | 2020 |
| Description | Presentation to wider scientific community of PhD students at the University of Bath |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | Local |
| Primary Audience | Postgraduate students |
| Results and Impact | The purpose of this presentation was to introduce the doctoral student community at Bath to the work I have been doing. The "in vitro" system was discussed in the context of reducing animal work in research, better understanding how drugs interact with the human skeletal environment and subsequently improving successful drug development. |
| Year(s) Of Engagement Activity | 2021 |