OXFORD BIOMEDICA PRESENTS UPDATED AND ENCOURAGING TROVAX^® PHASE II RESULTS IN COLORECTAL CANCER AT THE 2005 ASCO ANNUAL MEETING

Oxford BioMedica (LSE: OXB), the leading gene therapy company, today announced that new and encouraging data were presented from the Phase II trials of TroVax, its cancer immunotherapy, in colorectal cancer at the 2005 American Society of Clinical Oncology (ASCO) Annual Meeting, in Orlando, Florida, USA, on Sunday, 15 May 2005.

The presentation included data reported in March 2005 from the two Phase II trials in first line treatment of metastatic colorectal cancer alongside irinotecan-based (IFL) and oxaliplatin-based (FOLFOX) chemotherapy. In addition, further immune response data were presented. These show that the maximum antibody levels (titres) targeted against the 5T4 tumour antigen in the Phase II studies are significantly higher than in the Phase I/II trial in post-chemotherapy patients. Peak titres reached levels of 5,000 in the TroVax+IFL trial and 1,200 in the TroVax+FOLFOX trial. These are four- to ten-fold higher than in the Phase I/II study. This may be important because, in that earlier study, there was a highly significant (p<0.0001) correlation between antibody titre and time to disease progression amongst responders.

Additional new data include analysis of the anti-5T4 killer T-cell (CD8) response following immunisation with TroVax. Killer T-cells are widely believed to be important antitumour cells. Encouragingly, 83% of patients in the TroVax+IFL study and 71% in the TroVax+FOLFOX trial developed anti-5T4 killer T-cells, reaching levels as high as 1 in 1,000 white blood cells. This level is comparable with those seen in viral infections that are cleared by circulating antiviral killer cells. Interestingly, in the TroVax+FOLFOX trial, the two patients that showed complete tumour responses (tumour clearance) had the highest antibody and killer T-cells levels. This links, as in the Phase I/II trial, the anticancer immunological effect of TroVax immunisation to clinical benefit.

As previously reported, the primary endpoints in the two trials of safety and immunological responses were achieved. All 25 patients that have reached the interim stage of the trial have shown an immune response to the 5T4 tumour antigen. In addition, the secondary endpoint of clinical benefit exceeded expectation. Eighteen of 19 evaluable patients responded to treatment. Whilst five patients had disease stabilisation following treatment, 13 of the 19 patients (68%) were defined as clinical responders according to industry standard criteria, comprising three complete and ten partial responses.

Two independent studies of the chemotherapy regimens alone reported clinical response rates in evaluable patients of 41% and 50% respectively (Douillard et al., The Lancet 2000, vol 355, pp 1041-1047; de Gramont et al., Journal of Clinical Immunology 2000, vol 18, pp2938 –2947). However, a precise comparison with the TroVax trials is not possible owing to differences in the trial protocols and patient numbers.

Enrolment in the trials was completed in September 2004 with 36 patients recruited. The trials are on track to report full safety and immunological data as well as final audited tumour response statistics in the second half of 2005. Patient survival, which can be compared to historical controls, will be reported once the median survival has been reached in the two trials. This is anticipated in early 2006.

This ASCO abstract on the TroVax Phase II results may be accessed online at http://www.asco.org at the conclusion of the meeting on 17 May. The abstract title is as follows:

“An Open Label Phase II Study of MVA Expressing the Tumour Antigen 5T4 Given in Conjunction with Chemotherapy: Safety and Immunogenicity Before, During and After Chemotherapy.” (Abstract #30642)

Commenting on the ASCO presentation of TroVax Phase II results, Oxford BioMedica’s Chief Scientific Officer, Dr Sue Kingsman, said: “We are very pleased with the new data from the TroVax Phase II trials. Given what we know from the previous colorectal cancer trial, we are hopeful that the stronger anti-5T4 responses in the first line treatment setting will lead to a corresponding extension of time to disease progression and survival. Based on current data, we are optimistic that TroVax will have a role to play in the treatment of colorectal cancer and we look forward to this being evaluated in pivotal clinical studies”.

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