A panel of advisers to the U.S. Food and Drug Administration will meet on Tuesday to discuss a therapy based on the psychedelic drug MDMA for patients with post-traumatic stress disorder (PTSD).

The meeting by the agency’s independent experts is the farthest that a drug based on MDMA, commonly known as ecstasy or molly, has ever reached in the FDA regulatory process for approval.

It follows a decades-long push by advocates who say drugs like MDMA can treat mental health disorders and have therapeutic applications beyond their illicit use.

The treatment is a capsule form of MDMA made by the public-benefit corporation Lykos Therapeutics and is intended to be administered along with sessions of talk therapy by a licensed mental health provider.

In clinical trials in over 190 patients, those who received doses of MDMA in addition to therapy showed a significant reduction in PTSD scores compared to placebo.

However, the FDA’s staff reviewers on Friday raised concerns that patients in the trials were aware of whether they were given MDMA or a placebo due to its psychedelic effects, clouding how well the drug worked.

“I don’t think that is as much of a concern because even if it is an enhanced placebo effect, people are still getting better,” said David Olson, director of the UC Davis Institute for Psychedelics and Neurotherapeutics.

“But the bigger question is what is the risk to those individuals?”

PTSD affects 13 million Americans and is especially common among war veterans. There remains a large unmet need for new treatments for PTSD as existing drugs do not work on all patients.

The Lykos treatment is one among several psychedelic drugs being tested in patients with hard to treat mental health conditions such as Compass Pathways’ drug, which uses the same component as magic mushrooms.

The FDA’s staff proposed restrictions around its use and monitoring in their briefing documents on Friday. The FDA also flagged a rise in blood pressure and pulse in the trials and cases of liver toxicity.

The approval could offer “a new avenue of treatment, but itself is not going to make a big dent”, due to costs and complexities associated with it, said Olson.

“It’s important because it would be the first in this class of molecules, but I don’t think it will be the last, it will be replaced by compounds that have superior properties to MDMA.”

—Sriparna Roy and Pratik Jain, Reuters