A panel of independent advisers for the U.S. Food and Drug Administration voted against recommending approval of psychedelic treatment -- along with therapy -- to treat post-traumatic stress disorder (PTSD) during a meeting on Tuesday.
The treatment, developed by Lykos Therapeutics, is a pharmaceutical version of midomafetamine, better known as MDMA and sometimes referred to as ecstasy.
The Psychopharmacologic Drugs Advisory Committee appeared to have serious doubts about the safety and efficacy of the treatment.
On the question of whether the available data shows that the drug is effective in patients with PTSD, nine of the advisers voted no and two voted yes. On the question of whether the benefits of MDMA outweigh the risks for the treatment of patients with PTSD, 10 advisers voted no and just one voted yes.
MORE: How MDMA-assisted therapy could treat PTSD in ways current therapy can'tThe FDA is expected to make a decision by Aug. 11, according to Lykos Therapeutics. The FDA usually follows the recommendations of the advisory panel, although the recommendations are not binding.
PTSD is a disorder that develops in some people after experiencing or witnessing a traumatic event, according to the National Institute of Mental Health.
People can experience a range of symptoms including nightmares, unwanted memories, anxiety, depression or heightened reactions, and the conditions can last for months or years.
A multitude of studies have suggested that psychoactive drugs, including cannabis, ketamine magic mushrooms and MDMA, may help treat PTSD and other mental health disorders.
Some psychiatrists began using MDMA for treatment in the late 1970s and early 1980s with claims that it helped promote trust and improved communication between doctors and patients, according to the National Institute on Drug Abuse.
MDMA was classified as a Schedule I drug, meaning it has "no currently accepted medical use and a high potential for abuse," by the Drug Enforcement Administration in 1985.
In the 1990s, the FDA approved the first human trial examining use of MDMA to relieve pain in terminally ill patients as well as being used in combination with psychotherapy.
The company said it conducted two late-stage randomized placebo-controlled trials to evaluate the safety and efficacy of MDMA when used in combination with psychological intervention, such as talk therapy.
MORE: A form of 'ecstasy' could be a new treatment for post-traumatic stress"This will be the first MDMA-assisted therapy and psychedelic-assisted therapy to be reviewed by the Psychopharmacologic Drugs Advisory Committee, a significant milestone in the field of psychedelic medicine, resulting from decades of clinical research and advocacy," Amy Emerson, CEO of Lykos Therapeutics, said in a press release.
"We look forward to the opportunity to discuss the comprehensive data package of investigational MDMA and how, if approved, it may be used as a prescription treatment in combination with psychological intervention in adults with PTSD," the statement continued
In briefing documents released on Friday, the FDA said that based on the clinical trial data submitted by Lykos Therapeutics, "participants appear to experience rapid, clinically meaningful, durable improvement in their PTSD symptoms."
However, the federal health agency also noted concerns that the drug has the risk of causing "patient impairment" and the potential for "serious harm" as a result of impairment.
In the documents, the FDA said that if the drug is approved, there must be safeguards in place to monitor patients such as seen during the clinical trial, in which participants were monitored by two therapists for eight hours in a controlled setting and had to agree to not drive until the following day.
The FDA proposed further precautions, including enrolling patients in a registry to track side effects and progress.
Additionally, the FDA raised concerns about how the studies were conducted. Although designed to be double-blind -- meaning neither the participants nor the researchers know who is receiving MDMA and who is not -- the drug produces such "profound alterations" that the vast majority of participants were able to guess whether they received MDMA or a placebo, the agency wrote.
Nicholas Nissen, M.D., is an author, host of the Brain Health with Dr. Nissen Podcast and a contributor for the ABC News Medical Unit.
ABC News' Sony Salzman contributed to this report.