By Emmett Berg

SAN FRANCISCO (Reuters) - California scientists are testing whether the illegal psychoactive drug commonly known as Ecstasy could help alleviate anxiety for terminally ill patients, the trial's principal funder said on Tuesday.

At least a dozen subjects with life-threatening diseases like cancer, and who are expected to live at least 9 months, will participate in the double-blind trial over the next year in Marin County, said Brad Burge, spokesman for the Multidisciplinary Association for Psychedelic Studies.

Each subject will be randomly given either a full dose - 125 milligrams of MDMA followed up later by a supplemental dose - or a placebo with none of the drug, Burge said.

Burge said the goal is to test whether gravely ill patients suffering from debilitating anxiety, fear or depression due to their diagnoses can find a measure of peace during the extended Ecstasy-influenced psychotherapy sessions.

The trial's principal investigator, Dr. Philip Wolfson, told the San Francisco Chronicle newspaper that the MDMA experience, lasting four or five hours, can be "transformationally potent" under controlled settings with a pair of trained therapists.

"It's a substance that supports deep, meaningful and rapidly effective psychotherapy," Wolfson told the Chronicle.

MDMA, sometimes known as Molly, is a psychoactive drug that has been banned under federal law for decades.

While the Drug Enforcement Administration declined to comment, Burge said the federal agency has certified the security infrastructure of the clinic.

The Food and Drug Administration said U.S. law and FDA regulations prohibit the agency from disclosing information about drugs that are being developed and studied, said spokeswoman Sandy Walsh.

Results were expected within 12 to 15 months.

"Our hypothesis is that something is happening with MDMA that makes psychotherapy easier," Burge said.

Those receiving the full dose have an option later to take another 62.5 milligram dose as part of the same session, and those receiving the placebo can later re-enter the trial, he said.

(Corrects study location to Marin County in paragraph 2; corrects to show placebo has none of the drug in paragraph 3))

(Reporting by Emmett Berg in San Francisco; Editing by Michael Perry and Eric Walsh)