An experimental targeted treatment for ovarian cancer has shown promise in early clinical trials shrinking tumours in half of women with the disease.

Researchers from The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust tested the drug - known in the study as ONX-0801 - in 15 women with ovarian cancer as part of a wider Phase I clinical trial.

The aim was to actually to assess the drug’s safety, but ONX-0801 was also seen to significantly shrink tumours in seven of the 15 ovarian cancer patients, in what researchers are heralding as “very promising” results.

Furthermore, in those whose tumours had the particular molecular target for the drug, the results were even better – with seven of 10 responding, show the findings, which were presented at this year’s American Society of Clinical Oncology meeting in Chicago.

ONX-0801/BTG945 is the first in a new class of drugs, discovered at The Institute of Cancer Research (ICR), which attacks ovarian cancer by mimicking folic acid to enter cancer cells and then block a molecule called thymidylate synthase to cause irreparable DNA damage.

Ovarian cancer cells carry a large number of receptors for folic acid so are particularly targeted by the treatment, while healthy cells are left unharmed. This also means that it can avoid the side-effects often seen with traditional chemotherapy.

“It’s early days of course, but I’m keen to see this treatment assessed in later-stage clinical trials as soon as possible,” said study leader Dr Udai Banerji, deputy director of the Drug Development Unit at The ICR and The Royal Marsden NHS Foundation Trust.

“We have also developed tests to pick out the women who are likely to respond to the drug, making the treatment potentially more cost-effective, and ensuring other patients can receive alternative treatment.”

The ICR and Royal Marsden team, alongside partners at specialist healthcare company BTG, is now looking for partners to fund next-stage clinical trials as soon as possible.