Pregnant women who face losing their unborn babies to a so-far incurable growth disorder are to be offered a pioneering gene therapy that could treat the condition in the womb, The Times has learnt.

The world’s first patient study of a gene-based drug designed for use in pregnancy could begin this year, after groundbreaking research by British scientists.

The treatment could offer hope to thousands of couples who lose their babies to stillbirth, miscarriage and enforced abortions because they stop growing in the womb.

The condition, known as severe foetal growth restriction (SFGR), occurs because of reduced blood flow to the placenta, and affects about 1 in 500 pregnancies, or more than 1,000 in Britain each year.

Doctors can attempt to prevent it but only when women know they are susceptible because they have lost a pregnancy before. Less serious forms affect one pregnancy in twenty, and can lead to prematurity, lifelong illness and learning difficulties.

The therapy, developed by researchers at University College London Hospitals and Ark Therapeutics, a biotechnology company, uses a genetically engineered virus to deliver extra copies of a gene that promotes blood flow to the mother’s uterine arteries.

The goal is to ensure that more blood reaches the placenta and the foetus, so it gets the nutrients it requires to start growing again and survives.

Experiments with pregnant sheep have had encouraging results, showing that the drug significantly increases blood flow to the placenta. The research team is conducting fresh studies with guinea pigs and expects to start patient trials at the end of this year or early in 2010.

Regulators have already indicated that an initial safety study should be cleared quickly. The viral vector that conveys the gene therapy is already approved for human use and, as the disorder has such a poor prognosis, the research does not raise serious issues about risk to the foetus.

Anna David, Senior Lecturer in Obstetrics and Maternal and Foetal Medicine at University College London Hospitals and the lead researcher, said that SGFR was among the most intractable and distressing conditions that affects pregnancy. “The mother seems fit and healthy, and the foetus has no chromosomal problems or structural abnormalities, like a heart defect, yet it stops growing around the mid-point of pregnancy,” she said.

“Once it’s detected, there is nothing very much you can do about it. At the moment the only options we can offer parents are to terminate the pregnancy, or to continue in the hope that the baby gets to 600g or 27 weeks, in which case it might just have a chance. But most babies don’t get that far and die.”

The drug was expected to improve blood flow only for a few weeks, but this could make all the difference, Dr David said. “At this stage of gestation, survival goes up by 2 per cent a day. A week of growth can improve survival by 15 per cent. When we’re talking about a baby that has only a small chance, that’s huge.”

She said that women who have experienced SFGR before can be given aspirin in subsequent pregnancies to improve blood flow. This must be done before 16 weeks, however, and it is not possible when a woman does not know she is at risk.

The patient study will be a new departure for gene therapy, which uses viruses to ferry new copies of genes into cells to improve their function, as it is the first such treatment targeted at pregnant women.

Gene therapy has already been used successfully against several serious conditions, including childhood immune deficiencies that are fatal if untreated, and a cause of blindness called Leber’s congenital amaurosis. Despite its promise, however, it is controversial because the viral vectors that are required have sometimes had fatal side-effects. The gene delivery system that is being used in the SFGR treatment is much safer than some methods. The vector is an adenovirus like the one that causes the common cold, which is not considered dangerous, and it is already being used safely in Cerepro, a drug developed by Ark Therapeutics to treat brain cancer.

The virus is engineered to carry a gene called VEGF-D, which is involved in blood vessel growth and blood flow, to the uterine arteries that supply the placenta with blood.

Nigel Parker, chief executive of Ark Therapeutics, said: “It’s a vector system that has already been through regulatory review. We think we’re getting close to the natural molecular biology of pregnancy and tuning it up, getting the blood vessels to expand and take more blood through to the placenta.

“This is a gene that is naturally there in the mother and the baby. It’s a virus that all pregnant women already get: the common cold virus. I can see a whole gene therapy world opening up.”

Dr David said that it remains important to complete animal studies to show that the drug is unlikely to be toxic to mothers, and that it does not appear to cross the placenta. The guinea pig experiments, which are funded by Action Research, should achieve this by the end of the year.

The initial clinical study will investigate whether the gene therapy is safe. If it succeeds, Dr David plans to conduct a larger trial to evaluate the effectiveness of the drug.

Janet Scott, of Sands, the stillbirth and neonatal death charity, said: “Foetal growth restriction is a very ignored area . . . It is very welcome that these scientists are paying attention to this problem: an in-utero treatment that improves growth would be a big advance.

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