dctag vaccine against formation of tumours in mice

COMPANY ANNOUNCEMENT
Prima BioMed’s DCtag vaccine effective against formation of tumours in mice
Melbourne, Australia. 18 November, 2004: A paper published in the scientific journal Vaccine reports that one
injection of a novel vaccine (using DCtag adjuvant technology under development by Panvax Ltd, a subsidiary of
Prima BioMed, ASX:PRR) protected mice from challenge with a growing tumour and caused the eradication of a
pre-existent tumour mass.
The single injection of vaccine, based on proprietary DCtag technology, produced a strong immune response and
prevented the formation of tumours when mice were injected with thymoma cancer cells as well as causing the
erradication of a pre-existing tumor mass made of these cells . These same cells are commonly used to test the
effectiveness of vaccines under development.
The DCtag vaccine formulation consisted of a peptide epitope (the small region of a protein that causes an
immune response) attached to modified nanobeads. The inability of peptides on their own to cause a substantial
immune response poses a number of challenges to groups around the world seeking to develop peptide based
vaccines.
"This effective use of a peptide to prevent or treat cancer in a mouse model extends the range of possibilities for
the use of DCtag technology. We recently published results in the Journal of Immunology showing that a single
dose of vaccine incorporating a whole protein attached to beads both prevented the growth of tumours in mice
and cleared established tumors,” said Associate Professor Magdalena Plebanski, the senior author on the paper.
"We now know that peptides together with the modified nanobeads are also a very effective combination, capable
of inducing both CD8 T cells (cells with the capacity to target tumour cells for killing) and antibodies, to peptides
with corresponding target regions”.
Peptides have the potential benefit of giving the immune system a very precise target. A potential disadvantage of
classical vaccines is that they contain a lot of biological material that can fail to produce an immune response,
and may weaken the effect of the vaccine against its target disease.
Another significant finding of the Vaccine paper is that it shows the potential for DCtag-based vaccines to achieve
a strong CD8 T cell immune response by stimulation with a minimal peptide to stimulate this cell type. Usually,
vaccines able to induce CD8 T cells require also the co-joint activation of helper CD4 T cells, and thus the
inclusion of additional peptides to activate this additional cell type, in more complex formulations.
"This paper validates the potential of DCtag technology as the basis of products for treating a range of diseases,"
said Marcus Clark, Chief Executive Officer of Prima BioMed. Prima BioMed is in the process of completing the
preclinical development requirements for submitting a phase 1 clinical trial application to regulatory authorities
next year. This will determine the safety and immunogenicity in humans. If successful, the plan is to develop
DCtag as an immunotherapy product for the treatment of cancer. As we enter into this phase of DCtag’s
development its particularly reassuring to once again see peer group endorsement of the underlying science
through these publications in significant journals.
About Prima BioMed Ltd
Prima BioMed (ASX: PRR) is a biotechnology company based in Melbourne and is developing technologies in the
fields of immunology and cancer immunotherapy originating from the Austin Research Institute, in Melbourne,
Australia.
Company Contacts:
Company Inquiries: Marcus Clark, Chief Executive Officer 03 9854 5700
Media Enquiries: Rebecca Christie, Buchan Consulting 0417382391
This release may contain forward-looking statements. Various factors could cause actual results to differ materially from those projected in
forward-looking statements, including those predicting the timing and results of clinical trials, interpretation and implications of such results,
availability or adequacy of financing, the sales and marketing of commercial products or the efficacy of products. Although the Company
believes that the forward - looking statements contained herein are reasonable, it can give no assurance that the Company’s expectations
are correct. All forward - looking statements are expressly qualified in their entirety by this cautionary statement.