How the ICR is pioneering virus-based cancer therapies through clinical trials

Clinical trials are an essential to part of cancer research. They allow researchers to test and refine promising treatments in people and potentially get them approved for wider use, to save lives. Without them, there would be no new drugs, no evidence-based care and no improvement in outcomes for people with cancer.

Clinical trials are an essential to part of cancer research. They allow researchers to test and refine promising treatments in people and potentially get them approved for wider use, to save lives. Without them, there would be no new drugs, no evidence-based care and no improvement in outcomes for people with cancer. 

Each year, 20 May marks International Clinical Trials Day, when in 1747, a ship’s surgeon James Lind led what is considered the world’s first randomised clinical trial to study the effects of differing treatments for scurvy – a disease caused by the deficiency of vitamin C and common for sailors on long voyages.

At The Institute of Cancer Research, London, clinical trials are central to our mission of making the discoveries that defeat cancer. Over the past two decades, The Institute of Cancer Research (ICR) has led, managed or collaborated on numerous trials – including many of the world’s most significant studies on targeted therapies, radiotherapy, immunotherapies and personalised medicine – contributing to a number of approved cancer drugs and changes in treatment guidelines around the world.

Professor Kevin Harrington, Professor in Biological Cancer Therapies at the ICR and Consultant Clinical Oncologist at The Royal Marsden NHS Foundation Trust, has been instrumental in developing and delivering novel cancer therapies.

In a recent episode of the podcast Trials & Tribulations | Oncology Trials, hosted by Professor Nick James and Dr Hoda Abdel-Aty, both also researchers at the ICR and The Royal Marsden, Professor Harrington discussed the complex realities of taking new treatments from bench to bedside. The conversation focused on an exciting type of cancer therapy called oncolytic virotherapy, which is also known as viral immunotherapy, in which genetically engineered viruses – oncolytic viruses – are used to infect and kill cancer cells.

ICR at the heart of innovation

Globally recognised for its ability to turn fundamental discoveries into patient benefit, the ICR, in collaboration with The Royal Marsden, enables clinicians and researchers to drive the entire pipeline, from drug discovery and development through to clinical trials and regulatory approval. Professor Harrington’s team, working with the Centre for Immunotherapy of Cancer, a collaboration between the ICR and The Royal Marsden, has led some of the UK’s most ambitious trials of new therapies.

For example, they have led pioneering trials using a genetically manipulated herpes simplex virus – the same virus that causes cold sores – to treat head and neck cancer and melanoma.

In these early trials, patients received direct injections of the virus into their tumours, followed by careful monitoring to track its spread and effect. By engineering the virus to selectively infect and destroy cancer cells, the ICR laid the groundwork for a new generation of cancer immunotherapies, such as the viral therapy talimogene laherparepvec (T-VEC), which are now showing real promise in the clinic. 

Professor Harrington said: “We’ve probably run more first-in-human trials with oncolytic viruses than anyone else. The ICR provides the perfect environment – world-class science, close clinical partnerships and the infrastructure to handle risk safely.”

As well as establishing safety, ICR-led trials in oncolytic virotherapy incorporate detailed clinical endpoints to track how the virus behaves in the body – i.e., how long it stays in circulation, whether it spreads and how the immune system responds. Patients are monitored for the development of antibodies, and biopsies can reveal how the immune landscape inside tumours changes after treatment. These insights help researchers fine-tune trial designs and guide how and when viruses are used as a form of immunotherapy.

Trials challenging the status quo

Progress in cancer research not only depends on scientific rigour but also on the willingness to challenge outdated systems and navigating regulatory caution with care. Professor James, who specialises in prostate and bladder cancer research, recalls the early days of viral therapy, when unfamiliarity with live virus treatments made trial design and regulatory approval extremely difficult, especially in regard to safety containment.

For example, Professor James, before working at the ICR and The Royal Marsden, led the UK’s first trial using a virus to activate a cancer-killing drug inside the body for prostate cancer – a strategy known as virus-directed enzyme prodrug therapy. The concept involves delivering a harmless virus into the tumour, which would ‘switch on’ a specially designed drug and activate it precisely where needed, while minimising damage to healthy tissue. Due to initial uncertainty, Professor James recalled that the host hospital insisted the clinical trial were carried out in containment rooms similar to those used to treat patients with life-threatening viruses, such as Ebola.

Again, at an FDA meeting more than 25 years ago, the US drug regulator were so concerned about the risks of injecting a live measles virus (Edmonston) into lymphoma patients, that they only approved a single virus particle as the first dose.

“That first dose most likely didn’t contain a fully active virus. It’s incredible to see how far we’ve come,” said Professor Harrington. “Thanks in part to research led by the ICR and The Royal Marsden, viral therapies are now far better understood and have become increasingly explored in combination with radiotherapies, chemotherapies and immunotherapies to hopefully enhance treatment effectiveness.”

When side effects signal success

Professor Harrington went onto explain how immune responses — such as cytokine release — can be both a challenge to manage and an encouraging sign that the virus is engaging with the tumour. While these immune responses can cause unwanted side effects, they are also a sign that the treatment is working. ICR-designed trials are structured to balance patient safety while preserving the immune system’s therapeutic role. Suppressing these responses too aggressively could halt the very inflammation that helps the immune system fight the tumour.

These insights directly inform ICR-designed protocols, which are built around biological understanding and extensive patient monitoring — from tracking viral spread and antibody response to studying immune activation inside the tumour microenvironment.

Research with real-world impact

The ICR’s long-standing collaborative partnership with The Royal Marsden ensures that discoveries made in the lab can be translated into clinical practice. This bench to bedside approach is central to how new treatments reach patients.

One example is the ICR’s role in the clinical development of T-VEC, the first oncolytic virus therapy approved for melanoma. The therapy was originally developed by Dr Rob Coffin at BioVex Inc and trialled at Hammersmith Hospital, part of Imperial College NHS Foundation Trust, for inflammatory breast cancer. Yet, due to challenges in recruiting patient volunteers for breast cancer, the ICR and The Royal Marsden stepped in to lead its application in melanoma and head and neck cancers.

Professor Harrington and his team helped guide the trial through late-stage development, collaborating with international centres. They also supported the regulatory discussions with NICE to ensure that patients were able to benefit from the therapy.

The ICR and The Royal Marsden continue to work on next-generation viral therapies, collaborating with various external partners – including biotechnology and pharmaceutical companies – to lead first-in-human studies that shape the future direction of oncology.

The ICR has an unrivalled track record at discovering new cancer drugs and medical technologies. We’re convinced that working in close partnership with industry is essential to take results into the clinic as soon as possible, and make sure our research delivers maximum benefit for cancer patients.

Read more about industry partnerships

Shaping the future of cancer research

From first-in-human virus trials to next-generation immunotherapies, the ICR and The Royal Marsden lead research that has consistently pushed the boundaries of what’s possible to make real progress against cancer.

Professor Harrington said: “Clinical trials aren’t just academic exercises – they’re the bridge between discovery and impact. They require time, expertise, careful design and collaboration between researchers, clinicians and patients.

“The ICR and The Royal Marsden remain committed to leading this charge – not only by conducting world-class trials but also by shaping the next generation of researchers who will take these advances even further.”

As cancer continues to evolve, so must the science that confronts it. While International Clinical Trials Day reminds us why this work matters, the ICR reminds us how it happens – through vision, evidence and determination to move cancer research and clinical trials forward.

Episodes of Trials & Tribulations | Oncology Trials Podcast can be found on all streaming platforms.