Swedish researchers have started a clinical trial to assess whether a prostate cancer drug could help prevent pedophilic behavior—and they're counting on online donations to help finish it.

The team is reaching out to the public to collect £38,000 ($53,000) through a campaign launched today on Walacea, a U.K. crowdfunding website for scientific research. They hope to show that the drug, which lowers testosterone levels in the body, will reduce the pedophilic impulses that might cause people to abuse a child. So far, the researchers have recruited “four or five” participants, but they ultimately aim to enroll 60 men, the trial's principal investigator, Christoffer Rahm, said at a press briefing to announce the campaign in London on Wednesday.

The trial will not enroll sex offenders, said Rahm, a psychiatric researcher at the Karolinska Institute (KI) near Stockholm; on the contrary, the project “wants to shift the focus [to] preventing child sexual abuse from happening in the first place” by targeting men who have sought help to deal with their pedophilic impulses.

The trial participants are recruited through Preventell, a Swedish “helpline for unwanted sexuality” run by the Centre for Andrology and Sexual Medicine at the Karolinska University Hospital. Since it was set up in 2012, the helpline has received about 1500 phone calls from men seeking such help, said the center's director, Stefan Arver. This proves that “people with these thoughts really want help,” he said.

The drug that the team will test is called Firmagon, also known as Degarelix in its injectable form. It belongs to a class called Gonadotropin-releasing hormone (GnRH) antagonists, meaning that the drug competes with the body's natural GnRH and binds to its receptors in the brain, which ultimately blocks the production of testosterone in the testes. Currently, the drug—a form of "chemical castration"—is approved only to treat prostate cancer.

Other types of medicines are already prescribed—and sometimes mandated by law—to treat sexual offenders, including other drugs that change testosterone levels and selective serotonin reuptake inhibitors, a class of antidepressants. But some of these drugs are only effective after several months, and their use is “based on very weak evidence,” Niklas Långström, a psychiatric epidemiologist at KI, said at the press conference.

This is in part because research in this area is rife with complex ethical issues. Doctors who discover that patients have committed a criminal offense, such as downloading child pornography, must often report them to the police, so “few people will come forward” to seek help, said forensic psychiatrist Donald Grubin from Newcastle University in the United Kingdom. The use of placebos in randomized controlled trials, the gold standard in drug testing, raises questions as well. “Ethics committees don’t look kindly on giving sugar pills to potential offenders,” Grubin said.

Swedish regulators did sign off on a controlled study, however; the KI team plans to give half of the participants a placebo, whereas the other half will receive the drug. To assess its effect, potentially “just 2 weeks after injection and lasting 3 months,” the team will use a series of existing tests to measure three parameters: high sexual arousal, self-regulation, and empathy. Testosterone is involved in regulating these three “most important risk factors for committing repeated sexual abuse,” Rahm said. The study will not measure possible long-term effects on actual criminal offending.

Rahm says he opted for crowdfunding because public funding and a contribution from a private foundation fell short, while the team wanted to remain independent from the drug's manufacturer, Ferring Pharmaceuticals. The funds collected will help pay for the drugs, the salary of a research nurse, and functional magnetic resonance imaging experiments.

The trial is part of a broader project that will also search for genetic, neurological, and hormonal markers linked with a risk of acting on pedophilic impulses. Any markers the team may find would likely not be used to screen potential abusers, Rahm says, but rather to identify people most likely to respond well to treatment, or to confirm a psychiatric assessment.

Most currently used testosterone regulators are GnRH agonists, which stimulate GnRH receptors rather than blocking them, causing an initial surge in testosterone production before lowering the hormone's levels in the body. They are often used to treat prostate cancer in men or to suppress spontaneous ovulation in women undergoing fertility treatment. These drugs “take months to have any effect and the initial flare […] is not something you want in the acute phase”—the period when a person with pedophilic disorder is most at risk to act on his impulses, Rahm says. As a GnRH antagonist, Firmagon doesn't have these downsides.