The parents of Stanley Barnes have been dealt a devastating blow as an American pharmaceutical company ended, without notice, a revolutionary drug trial which they believe had been keeping the youngster's condition under control.

Stanley, aged three, suffers from Sanfilippo type A, a rare and terminal illness. Almost two years ago he was accepted onto a trial for enzyme replacement therapy which has meant fortnightly trips to Great Ormond Street Hospital for treatment.

The hope was the trial would slow down the effects of the condition and this has appeared to be the case which makes the news from America even more traumatic for his parents, Ross and Mari.

"The first we knew was when we had a call from Great Ormond Street Hospital (GOSH) and they were as shocked as we were," said Ross. "They didn't see it coming at all - no-one saw it coming. It was like receiving the news (of his diagnosis) all over again. Mari was deeply saddened by it.

"We now have a mixture of anger and sadness at the same time. We have this feeling that we had hope and that has now gone. Without that hope to cling to we feel powerless."

Ross added: "We all feel it (the trial) has definitely been beneficial for Stanley. We feel, looking back at photographs of him, that it has benefited him physically - his stomach is less distended - and facially some of the ridges you would expect to see have not formed on Stanley.

"We just don't know how to start a fight back or whether to try to continue. There is nowhere else to get the enzyme from, they were the only people to produce it."

Ross and Mari, of Mawnan Smith, have been reaching out to other companies who are carrying out clinical trials for gene therapy in America, Spain and Australia. "It is possible that he will not be considered for another trial, but we will keep trying," said Ross.

"We can perhaps show that he is in good form and is well and perhaps they will look at that and say this is a child we want on the trial."

The family have been enjoying a holiday and were this week celebrating little brother, Orson's first birthday. "We are looking at the positives - that we can be around the home more and can concentrate on Stanley's schooling and his physical abilities," said Ross, who starts his new job at Mawnan School next month when he will be teaching daughter, Willow, five. "We are desperate to try to create as many positive memories as we can and we are enjoying our time with him."

The family have to return to GOSH to have Stanley's port removed and will then be keeping a close eye on any deterioration of his condition. "The not knowing is the frightening thing," said Ross. "How quickly will the build up of enzyme leave his body, how quickly will he go down hill, how quickly will things decline for him? He does have Sanfilippo Type A which is the most aggressive of the three types."

In the meantime, supporters are continuing to raise money for Stanley's Friends, the charity set up to provide financial help for the family. The group's treasurer, Geraint Elvans, has pledged to give up alcohol for a year, starting on September 1, and is inviting donations, and Donna Harvey is organising a three-legged walk from The Moor to Penryn Quay this weekend. The walkers will head off at 10am on Sunday and Donna is inviting other pairs to join her in this sponsored event.