June 23 (Reuters) - Compass Pathways ( CMPS ) said on

Monday its experimental psilocybin-based therapy helped

significantly reduce the symptoms of difficult-to-treat

depression in a late-stage study.

The study, involving patients with treatment-resistant

depression who did not respond to at least two types of

antidepressants, opens a potential avenue for treating a

condition that is notoriously difficult to manage.

The company said a 25 milligram dose of COMP360,

combined with psychological support, enabled patients to achieve

statistically significant reductions in depressive symptoms or

remission.

This was measured on a standardized depression scale

after six weeks of treatment, compared with a placebo.

Shares of Compass fell 24% to $3.50 in premarket trade.

(Reporting by Mariam Sunny and Christy Santhosh in Bengaluru;

Editing by Mrigank Dhaniwala and Anil D'Silva)