UK drugmaker Antisoma was given a boost on news that one of its experimental cancer drugs showed promise in a Phase I study while another performed well in mid-stage trials for acute myeloid leukaemia.

Findings from a Phase I dose-escalation trial of the antibody-cytokine fusion drug AS1409, presented at the American Society of Clinical Oncology meeting in Orlando, showed evidence of clinical improvement and anti-cancer activity in patients with malignant melanoma and renal cell carcinoma. Furthermore, two patients with malignant melanoma exhibited substantial tumour shrinkage, the group said.

AS1409 is designed to combine the anti-tumour cytokine IL-12 with an antibody that specifically targets the tumour, to ensure that the drug is only delivered to the cancer and healthy cells thereby remain unharmed, minimising side-effects.

According to Dr James Spicer of Guys and St Thomas' Hospital, London, UK, a leading investigator in the trial, the findings “provide validation for the idea of targeting the delivery of IL-12 to tumours using an antibody”, particularly as “AS1409 has shown evidence of anti-cancer activity without the serious side-effects seen with untargeted IL-12”.

AS1411 also looking good
Meanwhile, the group says it plans to further develop another cancer candidate, AS1411, in acute myeloid leukaemia following encouraging results from a Phase II study in which patients responded well to the drug.

AS1411 belongs to a new group of drugs called aptamers, which are basically short strands of DNA or RNA that fold into various three-dimensional structures able to target certain proteins on cells, including on tumours.

The Phase II trial of AS1411 - the first randomised controlled assessment of a DNA aptamer in cancer, according to the firm – split patients into three different groups to receive either cytarabine alone (the control) or cytarabine with a high-dose of AS1411.

It was found that 5% of patients responded to treatment with cytarabine alone, but that response rates in those receiving 10 or 40 mg/kg/day of AS1411 with cytarabine were much higher, at 21% and 19%, respectively. In addition, the drug was found to be well-tolerated at both doses, the group said.

“These findings, seen in a very poor prognosis group of leukaemia patients, are very promising, and encourage us to go forward and further define the potential for AS1411 as a new treatment option for patients with AML,” commented Glyn Edwards, Antisoma’s chief executive.

Antisoma says on the back of these findings it plans to carry out a Phase IIb programme with the drug to optimise the choice of patient population and the design of future studies.