A vaccine which can help cocaine addicts break their addiction has been developed by a UK pharmaceutical company.
The vaccine blocks cocaine's 'high'
Trials carried out in the US showed almost half of those given the TA-CD vaccine, developed by Xenova, were able to stay off the drug for six months.
The vaccine does not stop the craving for cocaine, but will stop addicts experiencing a high when they take it.
The company says this prevents the people becoming re-addicted.
In the study, the TA-CD vaccine was compared with a dummy version.
David Oxlade, chief executive of Xenova, told BBC Radio 4's Today programme: "This is the third study in the US that we are reporting on today, and it shows that almost half the addicts were able to stay cocaine-free for six
"That is a quite remarkable position."
Mr Oxlade added: "The vaccine for cocaine addicts works in very much the same way a regular vaccine works.
"The reason cocaine addicts can take the drug for years without mounting any sort of immune response is because the drug has very small molecules."
He explained that the vaccine is created by attaching the cocaine to a large protein molecule which is used to stimulate the body's immune system to produce antibodies that recognise the drug.
Mr Oxlade added: "It stops the cocaine from being able to get across from the blood into the brain, which is where you get the high and, of course, where you get the
"If somebody takes the vaccine as part of a programme in a drug centre and after a month or so is out and takes another dose of cocaine, they won't get the high and they won't get the re-addiction."
He said it was possible that addicts would simply switch to another drug, but said evidence from three US trials showed that only happened in a small number of cases.
A spokeswoman for Drugscope told BBC News Online: "This is a really interesting study. It's clear that the vaccine seems to be working well for some cocaine addicts.
"But we have to remember that not everyone reacts in the same way to treatments.
"A lot of cocaine addicts have complex social and psychological issues. Once one drug stops working, if these underlying issues aren't addressed, people may move on to another drug that does."
Lesley King-Lewis, chief executive of Action on Addiction, said: "The first priority would be to give it to cocaine users who have already given up, because they are in danger of relapse, and then move on to those who are still using."
"There is no substitute drug available to use in treatment for cocaine addicts, so any extra help is vital in helping them to lead normal lives again."
But she added: "However, the vaccine must stimulate a very strong immune response so that every single cocaine molecule is mopped up if someone uses again. Otherwise a small number could get through and act like a teaser, causing the person to take even more to satisfy their cravings completely.
"Other forms of support would also be necessary for cocaine addicts giving up, as it is more than just the physiological addiction that causes people to use again. Craving is a very complex issue that won't necessarily be solved with a pharmacological intervention.
She added: "There are also ethical issues around when and how this vaccine is used."