The urgency to protect vulnerable populations such as the immunocompromised from viral respiratory diseases like influenza and COVID-19 is driving the need for novel approaches to new medicine development
To keep pace with the rapidly evolving variants of concern in the current pandemic and to be prepared for future pandemics, rapid clinical development and approval pathways are needed to respond in a timely manner. One way that researchers and health authorities are expediting the process is through immunobridging trials, a scientific approach that has paved the way for vaccine approvals across numerous infectious diseases.1–4
What is immunobridging?
Immunobridging is an approach to a clinical trial used to infer effectiveness of a new drug or vaccine candidate through an accepted surrogate measure for efficacy.2
Immunobridging trials are designed to demonstrate equivalent activity for an investigational therapy to a similar existing therapy (control).2 One example is to compare the ability of an investigational therapy to neutralise current versions of a virus (the immune response) with the relevant immune response data for a control therapy that has clinical data showing it prevents or treats disease. “Bridging” the data allows researchers to extrapolate anticipated efficacy for the investigational therapy.
What are the advantages of immunobridging trials?
Immunobridging trials can help reduce development time and accelerate access to important new therapies, without compromising tolerability.5,6 Given the rapid evolution of many viruses such as COVID-19 and the need to quickly recruit trial patients, collect data and report results, immunobridging provides an important avenue to enable inference of protection while results are still clinically relevant.
When would immunobridging trials be used?
Immunobridging trials are often used when full-scale efficacy trials may not be feasible or conducted under a fast enough timeline. This type of trial is well established for testing vaccines and has been used to develop and authorise COVID-19 booster shots, yearly influenza vaccine updates, HPV and pneumococcal vaccines.1–4
Immunobridging trials are also used to evaluate tolerability of the candidate therapeutic compared to the control. Health authorities and regulators agree that demonstrating tolerability of potential new products based on immunobridging is essential as well as the value in conducting post-marketing authorisation studies to further support safety profile and effectiveness.5,6
How has immunobridging been used in COVID-19 so far?
In COVID-19, global medicines regulators support the need for immunobridging trials as effective forms of evidence of efficacy, to help meet the urgent need to provide vulnerable populations with protection in a rapidly evolving variant landscape.5,6
Evidence from studies with authorised vaccinations for COVID-19 was sufficient to support using neutralising antibody titers as a primary endpoint in cross-platform immunobridging trials.5
How are we using immunobridging?
At AstraZeneca, we are committed to developing and delivering transformative vaccines and antibodies, providing long-lasting immunity for millions of people where the burden of disease is greatest. Our company is helping to lead the way with innovative immunobridging trials to accelerate access to next-generation medicines for COVID-19, where alternatives to running large efficacy trials are especially important given the rapid pace of viral evolution and the need to protect those at highest risk for severe disease.
We also work closely with global regulators and health authorities to agree upon the best and most efficient pathways and processes to support any potential authorisations of new therapies.
