WASHINGTON, United States (AFP) – Experimental tailor-made vaccines targeting melanoma patients’ individual genetic mutations have given encouraging preliminary results, researchers have said.

The clinical test on three patients with this form of aggressive skin cancer, in an advanced stage, is unprecedented in the United States.

The vaccines appear to boost the number and diversity of T-cells, which are key to the human immune system and attack tumours, researchers said in a report published last Thursday in the journal Science.

Melanoma accounts for around five per cent of all new cancer cases diagnosed in the United States, but that proportion is rising.

Last year 76,000 Americans were diagnosed with melanoma and nearly 10,000 died of it, according to the National Cancer Institute.

The vaccines were developed by sequencing the genomes of the three patients’ tumours and comparing them to samples of healthy tissue to identify proteins that had mutated. These are known as neoantigens, and are unique to cancer cells.  

The researchers then used computer programmes and laboratory trials to predict and test the neoantigens most likely to trigger a strong immune response, and thus be added to the vaccine.

The vaccine was administered to patients whose tumours had been removed, but without preventing cancer cells from spreading to the lymph nodes, which is an indication that the melanoma is going to reappear.

The initial clinical results have been good enough to start a phase one clinical trial approved by the US Food and Drug Administration on six patients.

If this broader test proves the vaccines work, it would pave the way for immunotherapy that prevents melanoma from resurfacing in patients.

The study was led by Gerald Linette, an oncologist at the University of Washington in St Louis, Missouri.

Although the test was preliminary, it was based on the breadth and diversity of the T-cells, meaning these vaccines are promising as a therapy, he said.

But the researchers cautioned that it was too early to say if these vaccines would continue to work long term.

None of the three patients tested so far have suffered major negative side effects.

Immunotherapy, already used with success against melanoma, is a promising new strategy against very aggressive cancer cells for which there is currently no effective treatment.