MADRID, Sept 28 (Reuters) - Using vaccines to fight cancer is a field littered with failures but experts believe it is possible the approach could get a new lease of life if such shots are combined with a new class of drugs called checkpoint inhibitors.
Unlike traditional preventative vaccines, therapeutic cancer vaccines are designed for people with established disease and are supposed to boost the patient's immune system to keep tumours at bay.
Unfortunately, the theory has not worked out in practice because, while the vaccines are successful at triggering a response from the "foot soldiers" of the immune system, cancer cells still manage to escape detection.
The result has been a series of failures with high-profile experimental cancer vaccines such as Merck KGaA's Stimuvax and GlaxoSmithKline's MAGE-A3.
GSK threw in the towel on its vaccine in April, dashing hopes for a project that was once seen as a potential multibillion-dollar sales opportunity in lung cancer and melanoma.
Johan Vansteenkiste of Belgium's University Hospitals Leuven, who led research into use of MAGE-A3 in lung cancer, reported full results of the failure at a medical meeting on Sunday and said the setback was a clear disappointment.
But he thinks the new checkpoint inhibitors, which are designed to stop the molecular trickery that is used by tumour cells to escape detection by the immune system, could finally unlock the value of such vaccines.
"For future progress, I think a combination of vaccination and checkpoint inhibition may be of major interest," he told the European Society of Medical Oncology annual congress in Madrid.
Advances with checkpoint inhibitors - particularly so-called PD-1 and PD-L1 drugs being developed by Bristol-Myers Squibb , Merck & Co, Roche and AstraZeneca - is dominating discussion at this year's ESMO meeting.
The new drugs are generating promising results in a growing range of tumour types and scientists are now casting around for novel ways to combine them with other therapies to get even better outcomes.
Therapeutic vaccines could be one such promising avenue, since they have very few side effects compared to many harsh cancer treatments.
Roche Chief Executive Severin Schwan said earlier this month that the Swiss drugmaker - the world's largest maker of cancer drugs - was already exploring ways of combining its checkpoint inhibitors with vaccines that had failed in tests when given on their own. (Editing by William Hardy)