A novel ovarian cancer drug developed at the Institute of Cancer Research (ICR) in London has shown efficacy at shrinking tumours in some women with the disease.
The drug, known as ONX-0801, inhibits the enzyme thymidylate synthase, which is critical for DNA and cell replication. It selectively enters cancer cells by mimicking the folic acid receptor, which is commonly overexpressed on cancer cells.
The researchers tested the drug in 21 women with either weekly or bi-weekly dosing for six four-week cycles using a dose-escalation design.
They found no grade 3–4 diarrhoea, mucositis or neutropenia, which are common side effects of chemotherapy, in patients on either dosing schedule. There was evidence of dose-limiting toxicity and drug-related respiratory changes in the weekly dosing cohort, but these were not seen in the bi-weekly treated patients.
The phase I trial
, which was not intended to establish the drug’s efficacy, found that 5 out of 11 patients with high grade serous ovarian cancer showed a partial response to the drug. And sample analysis in eight patients showed that all those who tested positive for folic acid-receptor overexpression had a partial response compared with none of the patients who tested negative for overexpression.
“The results we have seen in this trial are very promising,” says study leader Udai Banerji, deputy director of the drug development unit at the ICR and The Royal Marsden. “It is rare to see such clear evidence of reproducible responses in these early stages of drug development.”
He adds that the targeted nature of the drug means that it should have fewer side effects for women with ovarian cancer.
“It’s early days of course, but I’m keen to see this treatment assessed in later-stage clinical trials as soon as possible,” says Banerji.
 Banerji U, Ingles Garces AH, Michalarea V et al. An investigator-initiated phase I study of ONX-0801, a first-in-class alpha folate receptor targeted, small molecule thymidylate synthase inhibitor in solid tumors. Presented at ASCO Annual Meeting; 2-6 June 2017; Chicago, Illinois