Prima boosted by Cancer Vac trial results

Prima BioMed subsidiary Cancer Vac has announced positive results from the Phase Ib clinical trial of its cancer vaccine immunotherapy.

The patients in the study -- all with advanced cancer -- have now been on the treatment for up to 18 months, with no significant side-effects. All patients have demonstrated an appropriate anti-tumour immune response, while in two patients, the therapy has stabilised the tumour, with no progression of the disease since the treatment started.

Cancer Vac's therapy 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 (M-FP), 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.

But in the initial trial, the patients had to visit the clinic as often as every four weeks for blood collection prior to each treatment. Now the researchers, led by Cancer Vac's chief scientific officer Dr Bruce Loveland at the Austin Research Institute, have developed methods to freeze and store the patients' cells, meaning that patients would only have to undergo the blood collection process once or twice a year.

"[The trial] has continued to progress in the right way," said Prima CEO Marcus Clark. "We have immunogenicity, and we've been able to develop the therapy into a more practical process."

Clark emphasised that at this point, the Phase I trial is designed primarily to look at safety and the ability of the therapy to generate an appropriate tumour-targeted immune response.

"It's not intended to show efficacy, but the outcome is particularly useful for the next phase," he said. "Some tumour types have responded better than others."

Now the company is planning its Phase II trial, which is expected to start at the end of this year or early next year. The study, planned to involve 50 patients with ovarian and kidney cancer, will run for 18 months, and will look at both clinical endpoints and optimisation of the dosing regime. According to Clark, one area of interest, which will be addressed in the trial, is how long the immune system remembers the tumour vaccine.

And rather than treating patients with advanced cancer, the Phase II trial will involve patients who have just undergone surgery to remove a solid tumour, or who have just completed treatment with cytotoxic drugs, to see if the immunotherapy can prevent the patients from relapsing.

Clark said that Prima did not plan to license out or partner the Cancer Vac technology until it had completed the Phase II trial, believing that positive outcomes will significantly add value to the intellectual property. The company has instead been in discussion with potential co-investors for the project.

Prima has an 85 per cent interest in Cancer Vac. The company's share price (ASX:PRR) had increased by almost 25 per cent to AUD$0.38 at the time of writing.