Scientists want to see if the drug degarelix can help the volunteers keep their sexual urges in check without causing unacceptable side effects
Belfast - Paedophiles not convicted of any crime are being recruited for a new research project aiming to show that men at risk of sexually abusing children can be identified and treated before they target a victim.
A clinical trial looking at the effectiveness of a "chemical castration" therapy that cuts levels of the male hormone testosterone is already under way in Sweden.
Around the world, drugs are widely used to suppress the urges of sex offenders and one pilot scheme in Nottinghamshire is now being rolled out across the country, co-managed by NHS England.
But the Swedish scientists are taking the controversial further step of looking at whether men in the general population who are worried about their sexual urges can successfully be treated to prevent them committing crimes.
They also hope to pinpoint "biomarkers" - tell-tale substances in the blood or brain wiring patterns - that mark out individuals who could pose a danger to children.
The researchers stress that if such biomarkers are found, there is no question of them being used to conduct population screening for paedophiles.
However they could help psychiatrists or prison governors decide if certain individuals can safely be allowed near children, or who might benefit from a drug treatment.
Dr Christoffer Rahm, from the Karolinska Institute in Stockholm, who heads the "Priotab" project, said: "One in 10 boys and one in 20 girls is sexually abused during childhood. This issue is hard to deal with but we must, because it affects all of us.
"Child sexual abuse causes a lot of suffering for the victims and their relatives ... it also has negative consequences for the perpetrator, who risks becoming totally isolated, depressed and sentenced to imprisonment.
"Up until now most of the attention has been on how to deal with perpetrators while they're protected by the police or by the authorities, but by this stage children have already been harmed.
"With this research project, I want to shift focus and explore methods of preventing child sexual abuse from happening in the first place."
Paedophilia also incurred a high financial cost, he stressed. According to Home Office figures, a single offence of sexual child abuse cost an estimated £37,000 taking into account the police investigation, legal proceedings, and victim support.
Dr Rahm said a "handful" of men with paedophilic tendencies - none of whom had been convicted of any offence - had already been recruited by his team through a Swedish help line for people who fear their sexual appetites are out of control.
They were taking part in a study testing the effectiveness of degarelix, a prostate cancer drug that blocks signals from the brain that switch on production of testosterone. The male hormone is known to fuel the disease.
The aim is to compare 30 men receiving the drug with 30 others given a "dummy" placebo treatment.
The scientists want to see if the drug can help the volunteers keep their sexual urges in check without causing unacceptable side effects.
Three days after receiving an injection of degarelix, 97% of treated men have almost no detectable levels of testosterone in their blood. Unlike some other hormone treatments, the drug does not cause an initial "flare" that actually boosts levels of testosterone.
"The hypothesis we are testing is that this medicine has a clinically significant risk-reducing effect," said Dr Rahm.
The biomarker study, which was still at a "very early phase", would find out whether men who sexually abused children have any measurable traits that distinguish them from members of the general population.
These could include molecules in the blood, or specific patterns of brain structure or activity.
Part of the research will involve showing participants pictures of adults and children in swim suits while they undergo functional magnetic resonance imaging (fMRI) brain scans, said Dr Rahm.
Demons don't generally show up in MRIs.
"In clinical cases where the interview-based risk assessment is deemed unreliable, a supplement with a biological marker for risk would be desirable, even if it only increases accuracy by a few per cent," he said.
The goal of Priotab was to establish an "evidence-based preventive treatment programme" that could be employed "before the damage is done", Dr Rahm added.
In 2008 a pilot project was established at Whatton Prison in Nottinghamshire which saw more than 100 convicted sex offenders receive medication to reduce their sex drive.
The scheme, co-funded and managed by NHS England and the National Offender Management System, is now in the process of being rolled out nationally.
Forensic psychiatrist Professor Donald Grubin, from the University of Newcastle, who is involved in the programme, said: "Typically we come in after an offence has been committed, and we try to pick up the pieces.
"It would be great if we could do something before that."
The Swedish scientists, who are in the UK to promote crowdfunding support for their work, acknowledge that the research involves serious ethical issues which will be explored as part of the project.
A UK organisation based in Wales, StopSO, already offers psychological therapy to paedophiles before they offend.
It has won the support of the father of murdered five-year-old April Jones, whose killer Mark Bridger is serving a life sentence.
Paul Jones, from Machynlleth, Powys, told the BBC's Eye On Wales programme: "It's a glimmer of hope in the future.
"They're trying to offer help to paedophiles before they become offenders - it's the way forward. Prevention has to be the key."