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Date Time Issuer Part Headline Market Flag 09/05/02 N/A PRR N/A Human Trial In Cancer Demonstrates Immune Responses -Tumours N/A
PRIMA BIOMED LTD
Prima Biomed's (ASX: PRR) subsidiary Cancer Vac Limited today announced successful interim results of its Phase I human trial conducted in Melbourne. Patients have shown production of specific immune cells (T cells) that will make the body recognise the cancer cells as foreign and lead to attack. This was demonstrated after immunising cancer patients and was not associated with any toxic side effects.
This technology relies on boosting a patient's immune system to fight cancer. The novel approach involves extracting patients' blood cells, manipulating the immune cells and reinjecting the cells into the patient. This technology has been developed by scientists at the Austin Research Institute (ARI) over the last 10 years and has been the subject of intense research.
"We are attempting to help the body's own immune system fight cancerous tumours by developing both a product (an immune stimulant) and a process (immune system manipulation) that will make the body recognise cancer cells as foreign and thus lead an attack to kill them." said Mr Marcus Clark, Chief Executive Officer of Prima Biomed.
"These immune cells (T cells) can move through the tissues and can destroy solid tumours embedded in organs and tissues.
"So far the production of tumour specific T cells has been technically difficult. Cancer Vac has licensed a pivotal immune system stimulant that has been demonstrated to preferentially produce such cells.
The phase I trial in 10 cancer patients is ongoing with the analysis of the first 8 patients now completed. The final 2 patients are still undergoing treatment. The treatment was shown to produce the tumour specific immune response in 100% of patients analysed and who had completed three cycles of treatment. To date, there was no treatment-related toxicity, which is a critical issue in the development of human therapeutic agents.
Patients who have participated in the trial will continue to be monitored for up to 9 months post treatment. These patients are monitored for sustained T cell responses, presence of measurable tumour markers in the patients' blood and effect of therapy on tumour and metastasis size and number. Results from this follow-up will become available towards the end of this year.
"The results that have been recorded in this trial are the best we have seen in terms of immune system response. The significance of these results in the context of developments in cancer immunotherapy is very high. The preliminary results have been accepted for publication at the American Society of Clinical Oncology Meeting in the USA later this month and I am sure they will be of great interest to oncologists and pharmaceutical companies from around the world.
"However, we must now show that this immune boost translates into clinical activity, ie the regression or stabilisation of cancer," said Mr Clark. "We are now in the process of designing a further phase I/II study in a larger patient group to demonstrate such activity. It is anticipated this should begin in the 3 rd quarter of this year."
TECHNICAL BACKGROUND INFORMATION
It is believed that one of the reasons why cancers become established in the body is a result of failure by the patient's immune system to recognise tumour cells at an early stage. By re-exposing molecules produced by the cancer cells to the patient's immune system, immune based destruction of tumour cells can be facilitated. Certainly this has been the case in pre-trial animal models, particularly in mouse experiments conducted to date.
OBJECTIVES MET
The objectives of the Cancer Vac Ltd human clinical trial were two fold:
1. To establish if the process of cell extraction, (ex vivo) manipulation and re-injection of these cells could be tolerated by the patients; ie a toxicity study and;
2. To determine whether the ex-vivo manipulation of the patient's immune cells and their exposure to Mannan-Mucin 1 (MUC 1, a tumour specific molecule), would elicit a specific T cell immune response measured by the release of the immune hormone, gamma-interferon.
Interim analysis of the first 8 patients has been completed with no apparent toxicity/side effects experienced.
Immune monitoring techniques have demonstrated the generation of a selective T cell immune response against the tumour molecule MUC1 in 100% of patients analysed. The final 2 patients are still undergoing treatment with the trial due to be completed in July 2002.
THE IMMUNE PRIMING PROCEDURE
Mucin 1 is a glycoprotein frequently expressed in increased quantities by a range of cancers including breast, bowel, ovary, pancreas and lung. Consequently this molecule is a potential target antigen for immunotherapy.
Mannan is a complex of mannose sugar molecules and is Cancer Vac's proprietary immune stimulant. Recombinant MUC1 is chemically linked to Mannan to create the "product". Dendritic Cells (cells that enable the body to recognise foreign proteins) carry a mannose receptor to which the Mannan will bind, carrying the MUC1 in to the interior of the antigen presenting cell and then resulting in the stimulation of T cells specific for MUC1.
In the current trial, the patient's own isolated dendritic cells were cultured and stimulated with the Mannan-MUC1 ex-vivo and then re-introduced into the patient.
Patients with MUC1 expressing tumours were selected as trial participants. Leukopheresis (extraction of immune stimulating cells) was conducted on 3 separate occasions in order to collect more than a billion peripheral blood mononuclear cells (PBMC). A subpopulation of plastic adherent PBMC were cultured with the immune hormones Interleukin 4 (IL-4) and Granulocyte Macrophage Colony Stimulating Factor (GM-CSF) for a number of days to generate the dendritic cells (DC). The DC were then exposed to the Mannan-MUC1 and re-injected intradermally and subcutaneously back into the patient.
Ten patients have entered the study and the first eight have been evaluated for immune responses. All patients showed significant levels of gamma Interferon producing tumour MUC1 specific lymphocytes. A subcutaneous delayed hypersensitivity also occurred in all patients who had completed three cycles of treatment, which corroborated the gamma interferon result showing the production of specific immune cells.
ONGOING DEVELOPMENT
Patients who have participated in the trial will continue to be monitored for up to 9 months post treatment. These patients are monitored for sustained T cell responses to MUC1, presence of measurable tumour markers in the patient's blood and effect of therapy on tumour and metastasis size and number. Results from this follow-up will become available towards the end of this year.
In July 2002, the design of an expanded Phase I/II study will be finalised. Such a study will be designed to investigate the potential clinical efficacy of the immune stimulant and the immunizing process.
Inquiries: Marcus Clark CHIEF EXECUTIVE OFFICER 03 9287 0637 Rudi Michelson (Monsoon Communications) 03 9620 3199
ends - AAP
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