Definium Therapeutics said a single dose of its LSD-based experimental pill significantly reduced symptoms of major depression in patients in a late-stage trial, sending its shares soaring 55% to a more than four-year high on Monday.

The experimental drug helped patients record significantly lower scores on a standard depression scale than those on placebo after six weeks, with an 8.1-point difference, meeting the trial’s main goal, the company said.

The pill, DT120, belongs to a class of drugs known as classic psychedelics, which temporarily alter perception, mood and thinking. It is a pharmaceutical formulation of lysergide, better known as LSD, and works by activating serotonin receptors in the brain.

In April, President Trump signed an executive order to speed up access to psychedelic-based treatments.

Definium shares, which have gained about 174% so far this year, were trading up 52% at $37.23.

Needham analyst Ami Fadia called the results “unprecedented in the depression space,” adding the drug showed greater reductions in scores at six weeks than Johnson & Johnson’s Spravato and Compass Pathways’ COMP360 achieved at week four.

Axsome Therapeutics’ Auvelity and Sage Therapeutics’ Zurzuvae are some of the other treatments for major depressive disorder (MDD).

“DT120 could emerge as a worthy competitor in the MDD / TRD space with a strong clinical profile,” Fadia added.

Definium said the data brings it closer to a Food and Drug Administration submission, and it was running a second late-stage depression trial.

The drug was generally well-tolerated, with 99% of adverse events mild to moderate, occurring mainly on the day of dosing, and no serious safety issues or increase in suicidal thoughts observed.

The trial enrolled 149 participants aged 18-74 years with MDD, the second-most common mental health disorder in the US, with more than 21 million adults experiencing a major depressive episode each year.