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Announcements


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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