Prima's CancerVac begins ovarian cancer trial

Prima Biomed (ASX: PRR) subsidiary CancerVac began a Phase IIa clinical trial today to evaluate its immunotherapy in patients with ovarian cancer.

In the Phase IIa trial commencing at Melbourne's Austin Hospital, 20 patients with ovarian cancer will receive the therapy over a 12 month period. The trial will be run in conjunction with scientists from the Austin Research Institute, and is expected to take upwards of 18 months, although the company expects to release interim results in late 2005.

"There are two reasons we've focused on ovarian cancer," said Prima's business development manager Vanessa Waddell. "One of the patients from the initial trial, who was not expected to live for much longer, exceeded all expectations of survival and 2.5 years later is still alive with stable disease.

"Another factor is that there is a blood marker for ovarian cancer, CA-125, which can be used to measure the progress of the disease post-surgery and post-chemotherapy. It's a fairly simple way of measuring tumour activity."

CancerVac's immunotherapy works by teaching the immune system to recognise the tumour cells as foreign. Dendritic cells are removed from the patient and stimulated with mannan fusion protein (MFP), consisting of the antigenic portion of the tumour antigen mucin-1 (MUC-1) fused to the immune-enhancing sugar mannan. The cells are then reinfused back into the patient to generate primarily a T-cell-based immune response against the MUC-1-expressing tumour.

In the Phase I clinical trials, advanced cancer patients with a variety of tumour types including breast, colon, ovarian and prostate cancer were treated with the therapy, and all showed a positive response to the treatment.

"Due to the nature of the therapy we believe there is no reason why it cannot be continued indefinitely as long as proving beneficial to the patient. Two patients from the Phase I trial - in which 10 patients were initially treated - have remained on treatment for over two and a half years and both are doing very well," said Dr Paul Mitchell, the principle investigator for the trials.

In March this year, CancerVac entered into an agreement with Biomira, which gives the Canadian biotech company the right to commercialise the MFP technology for cancer immunotherapy. Biomira has also taken a 10 per cent equity stake in CancerVac.

Waddell said Biomira would decide whether to take up its rights to commercialise the immunotherapy after results were available from the Phase IIa trial. If Biomira takes up the option, CancerVac stands to receive up to $20 million in upfront milestone payments, as well as royalties if the product goes to market.

"A kidney cancer trial is on the table, but this will be dependent on funding and will probably be triggered by good interim results from the ovarian cancer trial," Waddell said. "It's possible that a kidney trial will be funded by Biomira."