Oxford BioMedica released additional data from its Phase I/II clinical trial of TroVax at the Society for Cancer Gene Therapy Conference in London in July 2002
The data, presented by Miles Carroll, vice president of immunotherapy at Oxford Biomedica, is from colorectal cancer patients at the Christie Hospital in Manchester receiving medium and high doses and shows that they tolerated the product well with no adverse reactions being observed.
In addition, the results demonstrate that TroVax is extremely efficient at inducing the appropriate immune response with all of the ten immunocompetent patients analysed to date in the trial mounting a specific response against the tumour antigen OBA1, the active component of TroVax, and some patients showing reductions in levels of circulating tumour marker proteins that are used as indicators of tumour load.
The new data reinforces the observations previously reported for the low dose group.
The trial has been a complete success and TroVax will proceed to the next stage of clinical development.
TroVax is a gene-based therapeutic vaccine that is designed to stimulate the patient's immune system to recognise and destroy cancer cells.
The product is based on a gene that encodes a protein, OBA1, that exists on the surface of tumour cells and not on normal cells - such proteins are known as Tumour Associated Antigens (TAAs).
When the OBA1 gene is expressed by Oxford BioMedica's highly engineered virus-based delivery system, it induces an anti-tumour response.
OBA1 is present on a wide range of tumours, thus while the first clinical trials of TroVax have been conducted in colorectal cancer patients, TroVax is also expected to be applicable to many other solid tumours.
The Phase I/II study described was designed primarily to assess safety and immunogenicity of TroVax in 12 patients.
As is the case with all early stage cancer trials, the patients were at a relatively advanced stage in the disease.
All 12 patients have been recruited and treated with TroVax.
As reported previously, one of the patients in the low dose group was unable to mount an immune response to any test antigen during the study and so was not included in the immunological evaluation of TroVax.
One other patient is part-way through their treatment and their immune responses have not been analysed fully to date.
The remaining ten patients all responded to TroVax by mounting an immune response to the tumour protein OBA1.
It is this response that is anticipated to have a beneficial effect.
In several patients the induction of the immune response was correlated with reductions in circulating markers of tumour load.
In the current trial patients were recruited after they had completed chemotherapy treatment.
In the next trial it is likely that the product will be tested on patients who are at a somewhat earlier stage in the disease process.
Although still in the planning stage, it is likely that the next trial will be a phase II study, in which TroVax will be assessed in colorectal cancer patients while they are undergoing chemotherapy.
This patient group would be the first target market for TroVax.
Subsequently the therapy may be used in other tumours and at an earlier stage.
The market potential for TroVax is substantial as an addition to existing cancer treatment regimens.
Approved drugs such as irinotecan, which have been shown to extend survival by a few months, have achieved global sales in excess of $500 million as an addition to standard 5-FU chemotherapy.
Commenting on the results presented today Oxford BioMedica's chief executive, professor Alan Kingsman said: "We are delighted that the TroVax trials have been so successful with such encouraging results.
"It is unusual for a vaccine, particularly a cancer vaccine, to elicit an immune response in all patients.
"We believe that we have achieved a significant step towards TroVax progressing successfully to the market".
