In vivo models to target respiratory diseases


Envigo’s Steve Jordan offers intuitive analysis and insights into methods of optimising in vivo efficacy studies and predicts what developments might be coming to fruition in the future

Scientists involved in biopharmaceutical and biomedical research seek to generate the highest quality data for their studies by employing an optimal combination of in vivo and ex vivo models. Regarding the use of animals in research, the 3Rs principle of replacement, reduction and refinement is guiding the scientific community and has helped to drive the development of innovative new tools for researchers.

Today, complex, three-dimensional models of a living, breathing human lung are being used for efficacy and safety assessment in combination with in vivo studies, which enables the translation of science from bench to human. It’s an exciting time to be a researcher, with new technologies emerging that have the potential to change how we understand and treat disease.

This article, which is based on practical experience at a contract research organisation (CRO), will provide an inside look at how our scientists employ leading ex vivo and in vivo tools to deliver high quality data to our customers. Envigo’s work takes place in a context in which our customers have been reducing the size of in-house in vivo teams and placing a greater reliance on partnering with external organisations. They seek help to derisk the failure of compounds in good laboratory practice (GLP) studies by including early functional and safety biomarker screens in the discovery phase of drug development — with the goal of trying to reduce compound attrition in later stages of development.

And, they seek to drive innovation in the research process to deliver safer, more effective treatments to patients at a reasonable cost. Hence, they focus on improving the productivity of drug development in as many ways as possible.

At Envigo, our customers require us to continuously improve validated in vivo models to identify ways to incorporate more clinically relevant biomarker and functional endpoints into study designs, test the most clinically relevant positive controls, and include more safety endpoints in each study — all with the goal of reducing the numbers of animals used while maximising the outcomes from each animal.

Owing to the volume of studies conducted at our facilities for decades, Envigo has a number of core validated in vivo models to target respiratory diseases. Some are pharmacokinetic/ pharmacodynamic (PK/PD) models targeting specific mechanisms involved in lung inflammation, such as our lipopolysaccharide (LPS)-induced non-allergic pulmonary inflammation model, ovalbumin sensitised and challenged rodent models, and the acute cigarette smoke model. Some are disease state models, mimicking multiple chronic inflammatory processes such as the murine house dust mite model of allergic inflammation and viral and bacterial lung infection/exacerbation models. Other models are designed to test the in vivo potency and duration of action of novel bronchodilators or antitussives designed to relieve the symptoms of asthma, COPD and lung infection. We have also seen great demand for models of lung fibrosis and pulmonary artery hypertension, which reflects the unmet needs in these disease areas and the research efforts being expended by pharmaceutical companies.

Lung fibrosis: an area of new in vivo developments

Lung fibrosis is not a single disease but an umbrella term for a variety of interstitial lung diseases that are characterised clinically by progressive dyspnea, cough, restrictive physiology and impaired gas exchange caused by scarring of the connective tissue of the lung. Lung fibrosis can have a variety of aetiologies, including

  • occupational or medical exposure to substances such as asbestos or the antibiotic bleomycin
  • genetic defects, in which mutations in a number of genes have been implicated in the development of familial interstitial pneumonia, a form of fibrosis
  • after trauma or acute lung injury (ALI) leading to fibroproliferative acute respiratory distress syndrome (ARDS)
  • idiopathic origin, referred to as idiopathic pulmonary fibrosis (IPF).

The heterogeneous nature of lung fibrosis, its myriad causes and phenotypes, and its increasing incidence worldwide have made it a priority area for research activity. However, medications to treat these conditions have been slow to emerge through the drug development process. There are currently two medicines marketed for lung fibrosis: pirfenidone (Esbriet) and nintedanib (Ofev), which are indicated only for IPF, leaving a clear gap in the management of other interstitial lung diseases.

These medications came to market after more than 10 years of research activity on a number of drug candidates. The reasons that some of those candidates for lung fibrosis failed to make it to market has been attributed to the heterogeneity of the disease process, inappropriate in vivo models, less than desirable clinical study designs and endpoints, and weak drug candidates.

As a result, there has been a real focus among our customers to develop a variety of in vivo models of lung fibrosis using various techniques to induce the disease state. These include models in which disease is induced by direct lung injury or through genetic alteration. Each model has its own strengths and weaknesses, and although none truly reflects the full pathogenesis of IPF, the diversity of models enables the study of specific aspects of the disease.

The most widely used in vivo model for lung fibrosis remains the single dose bleomycin model, despite challenges relating to the validity of the clinical translation of this model.

At Envigo, we are currently developing a low-dose repeat systemic bleomycin model of lung fibrosis, mimicking the progression of the disease seen in the clinic whilst reducing the burden on the animals involved in non-clinical testing. We foresee that the in vivo requirements for lung fibrosis models will continue to grow as new drugs are developed in this area of unmet need. This can be partly evidenced by the fact that, currently, the European Medicines Agency (EMA) has given 15 medicines rare disease (orphan) designations for pulmonary fibrosis. An orphan designation allows a pharmaceutical company to benefit from incentives granted by the European Union to develop medicines for rare diseases. Incentives can include reduced fees and protection from competition once the medicine is marketed.

And although predicting the future is certainly challenging, especially in dynamic disciplines such as biomedical and biopharmaceutical research, it is clear there will be an ever greater use of transgenic animals that have been optimised for specific disease phenotypes, as well as biomarkers for lung fibrosis and other conditions resembling the personalised medicine approach in the clinic. Such advances will increasingly be augmented or replaced with in vitro tools that improve research and reduce the number of animals used in the scientific research community.

The prerequisites for enhanced in vivo models

In our experience, the success of in vivo studies requires integrated work between CRO scientists and the study sponsor, as well as a range of internal disciplines — including pathology, formulation chemistry, bioanalysis, toxicology and dedicated biomarkers scientists. For respiratory studies, we also include inhalation scientists who can help to support the study design for drugs intended to be administered by the inhaled route. By working together, these disciplines devise robust study designs and testing regimens that maximise the value of each in vivo experiment.

With this approach, Envigo has the flexibility to adjust and refine existing in vivo models, incorporate additional clinically relevant endpoints and validate these endpoints. Building bespoke studies is essential because, as Jeffery Everitt from GSK put it: “Optimal study design is not a one-size-fits-all proposition.”

Towards multiplex, clinically relevant endpoints

Having the appropriate validated in vivo models is essential to improve the effectiveness of preclinical work, as is designing studies that include multiple endpoints that are of clinical relevance. This trend towards multiplex, clinically relevant endpoints allows scientists to continue maximising the information we can gain from fewer animals.

Envigo employs a variety of pharmacological and functional endpoints that we incorporate into existing in vivo models as needed. Clinically relevant functional endpoints for in vivo respiratory studies include rodent non-invasive and invasive lung function testing that allows the assessment of measures such as forced expiratory volume (FEV), forced vital capacity (FVC) and peak expiratory flow (PEF). Plus, techniques such as bronchoalveolar lavage (BAL) enable the assessment of biomarkers such as total and differential cell counts and inflammatory cytokines.

In vivo models of disease states are evolving, with more robust and complex study designs allowing the gathering of data for multiplex, clinically relevant endpoints. Such models are increasingly being deployed alongside ex vivo testing tools. This empowers scientists in CROs and elsewhere to maximise the results we gain from each animal experiment, thus helping us to reduce animal usage while generating higher quality data for our studies.