Doctors have developed a cocktail of two drugs which can reverse diabetes.

Scientists described the discovery yesterday as "an important step towards a potential cure". It could mean an end to the daily insulin injections and rigid dietary restrictions suffered by millions worldwide.

The drugs cocktail has so far only been tested on animals but each of its constituents is already being tested individually in human clinical trials. The treatment is for Type 1 diabetes, which usually starts in childhood. It occurs when the immune system turns on itself and attacks the insulin-producing cells of the pancreas.

The cocktail, developed by scientists at La Jolla Institute for Allergy and Immunology in San Diego, California, combines a monoclonal antibody which calms the immune system with a peptide that acts like a vaccine to protect the insulin-producing cells.

In laboratory mice given the cocktail, it was more effective, had longer-lasting results and fewer side effects than either therapy had shown alone in the human studies. In most of the animals tested, diabetes was reversed.

Trials of the monoclonal antibody in humans have already shown it can reverse Type 1 diabetes but although the effect lasted for more than a year, the diabetes returned. The results suggest that when combined with the peptide, the two drugs act together to produce a greater effect than either individually.

Richard Insel, executive vice president for research at the US Juvenile Diabetes Foundation, said it was "an exciting and important finding". "This combination approach is worth evaluating in human type 1 diabetes to increase both the overall efficacy of the treatment and the duration of the beneficial effect," he said.

George Eisenbath, executive director of the Barbara Davis Centre for Childhood Diabetes in Colorado, said it was "a very important discovery demonstrating synergistic efficacy of two therapies". The research team, led by Matthias von Herrath, said it hoped to begin human trials of the combination therapy later this year but was awaiting approval from drugs safety regulators.

The antibody is taken orally and the peptide by nasal spray, avoiding the need for injections. The approach focuses on teaching the immune system to tolerate, rather than attack, the insulin-producing cells of the pancreas.

The danger of suppressing the immune system is that it puts patients at increased risk of cancers or viral infections. But by combining drugs, a lower dose of the immuno-suppressant antibody is required, with a lower risk of side effects.

Dr von Herrath, an expert in the molecular basis of diabetes, said it was the first time a vaccine strategy had been tried in Type 1 diabetes. He said: "The combinatorial approach doubled the efficacy in laboratory mice - with fewer side effects than using either one alone. The diabetes never recurred in the lifespan of the mice."

Diabetics inject insulin to control their blood-sugar levels but complete control is difficult to achieve. Complications can lead to kidney failure, blindness and amputations.