Thursday 4 June 2026

Results from a global clinical trial show that using a brand-new drug – currently called GRWD5769 – with an existing type of immunotherapy called cemiplimab[1] can shrink tumours or keep them stable in people with six different advanced and hard-to-treat cancers.[2]

Every patient who responded in the Phase 1/2 EMITT-1 trial had already failed treatment, and most had no conventional treatment options left after multiple lines. Crucially, immunotherapy hadn’t worked – or had stopped working.

Unlike many cancer treatments, GRWD5769 was well tolerated by patients meaning that they could stay on the drug and have a better quality-of-life.

The results, which were generated between March 2023 and March 2026, were presented at this year’s ASCO Annual Meeting in May by Professor Fiona Thistlethwaite, Consultant Medical Oncologist at The Christie NHS Foundation Trust and Principal Investigator of the trial. Fiona is Medical Director of the National Institute for Health and Care Research Manchester Clinical Research Facility (CRF) at The Christie, one of the sites where the study was delivered.

The pill, which has been developed by Oxford-based company Greywolf Therapeutics and can be taken at home, has the potential to make immunotherapy effective where it hasn’t been.

Summary of the data to be presented at ASCO 2026:

  • Responses where the tumour has shrunk by at least 30% were achieved across all six tumour types, and deep responses of up to 95% were
  • The combination was most effective in the cohort of patients with bladder cancer and, critically, showed promise in those with microsatellite stable (MSS) colorectal cancer who did not have liver metastases – a tumor type where immunotherapy has shown no meaningful benefit and remains unlicensed.
  • Responding to immunotherapy after having already failed it before is very rare, but the overall response rate observed across the six tumour types was between 13% and 36%.
  • Durable clinical benefit – where the patient is living without disease progression for at least six months – ranged from 18% to 55%.
  • In a striking difference to many experimental cancer treatments, this new drug is well tolerated with a favourable safety profile across all six cancers.

 

200 people are taking part in the trial at 28 cancer centres in four countries[3], including six in the UK[4]. The trial is still ongoing, with a larger study already in planning.

Professor Fiona Thistlethwaite, Consultant Medical Oncologist at The Christie NHS Foundation Trust and Medical Director of the National Institute for Health and Care Research (NIHR) Manchester Clinical Research Facility (CRF) at The Christie, one of the sites where the study was delivered, said:

“Immunotherapy has been a gamechanger in the way we treat cancer, but the number of people that can benefit is still relatively low.

“What excites me about this trial is the combination of what we’re seeing – strong signals of efficacy across six tumour types that have shown great resistance to immunotherapy, with very few side effects. That’s unusual at such an early stage when we’re usually just looking at how safe it is.

“There’s a lot more work to be done before it reaches the clinic, but for a brand-new drug to show that kind of profile so early, and in so many different types of hard-to-treat cancers, gives me genuine optimism.”

How GRWD5769 works

Immunotherapy works by enlisting T cells — the cells of the immune system that attack infections — to hunt and destroy cancer. It’s been a gamechanger for cancer treatment, but it fails in around two thirds of patients.

This is because immunotherapy struggles when tumours hide from the immune system, or when T cells become exhausted fighting the same cancer target repeatedly. These are two of the biggest challenges facing immunotherapy researchers.

GRWD5769 aims to tackle these problems by both making the tumour cells visible to the T cells that couldn’t previously find them and by periodically changing which T cells attack to prevent them from burning out.

It does this by inhibiting an enzyme called endoplasmic reticulum aminopeptidase 1 (ERAP1), which helps the immune system to recognise the cancer and attack it. A drug has never been clinically tested with this target before.

When used in combination with cemiplimab – which works by blocking a protein called PD-1 which stops the immune system from fighting tumours – this creates a two-pronged approach to attacking the cancer.

In terms of how treatment works, patients take two GRWD5769 capsules a day for three weeks and have one intravenous dose of cemiplimab over that period.

Then, over the next three weeks, they just have one intravenous dose of cemiplimab. Treatment continues in this way – three weeks on both treatments followed three weeks just on cemiplimab. The dose cycling aims to continuously refresh the pool of T cells attacking the tumour, preventing them from burning out.

The UK Chief Investigator is Professor Stefan Symeonides, Consultant Medical Oncologist at the Edinburgh Cancer Centre, NHS Lothian, and Professor of Experimental Cancer Medicine at the Institute of Genetics and Cancer, University of Edinburgh, who said:

“This exciting new type of immunotherapy reveals hidden aspects of the cancer to the immune system to renew the immune response and then keep it refreshed and active.

It is fantastic to have been able to bring this promising new immunotherapy approach through to clinical trials and to see our patients benefiting.”

Professor Thistlethwaite is also Co-Director of the NIHR Manchester CRF.

[1] Cemiplimab is an anti-PD-1 treatment and type of immunotherapy

[2] The types of cancer included in the trial are cervical, bladder, liver, non-small cell lung cancer, squamous cell carcinoma of the head and neck and a type of bowel cancer called microsatellite stable bowel cancer.

[3] The countries are Australia, France, Spain and the UK

[4] The UK sites are The Christie NHS Foundation Trust, The Clatterbridge Cancer Centre NHS Foundation Trust, Royal Free London NHS Foundation Trust, Hammersmith Hospital (Imperial Colleague Healthcare NHS Trust), Newcastle Hospitals NHS Foundation Trust and Western General Hospital (NHS Lothian).