Developing a new treatment for patients suffering from Major Depressive Disorder


CLE-100 is a tablet being developed as an add-on treatment for patients who do not get enough relief from standard antidepressant therapy. It targets a more rapid antidepressant effect than most current medications.

CLE-100 is a new investigational drug that has not been approved for commercial distribution.

Unmet need in the treatment of depression

Major depression can be devastating for patients and their loved ones.  Episodes of major depression are characterized by depressed mood or loss of interest or pleasure in usual activities that lasts for at least 2 weeks and often much longer. These episodes are accompanied by an array of symptoms including changes in eating or sleeping patterns, fatigue, difficulty concentrating, indecision, thoughts of death or suicide, or feelings of despair. About 20% of the population will experience major depression at some time during their lifetime and major depressive disorder (MDD) is a major public health problem.

While many treatments are available, they are often not effective enough.  The National Institute of Mental Health-funded Sequenced Treatment Alternatives to Relieve Depression (STAR*D), the most comprehensive and largest clinical study of MDD, showed that remission of depressive symptoms is achieved in only one-third of patients after their first antidepressant treatment trial with an established antidepressant medication and 33% of patients did not reach remission even after treatment with 4 different medications (Rush et al. 2006). Since most antidepressant medications generally take 4- 6 weeks to relieve depression, patients who required multiple medication trials spent months waiting for relief to come.

Our program

Scientific aspects

CLE-100 targets blockade of the NMDA receptor, with high affinity to PCP site of the receptor.

Clinical aspects

CLE-100 is currently being tested in Major Depressive Disorder (MDD) patients in the CLEO study, a two-part randomized, double-blind, placebo-controlled, Phase 2 study conducted in the US.

  • Part A of the CLEO Phase 2 study: assessed the safety, tolerability and full pharmacokinetic profile of CLE-100 given daily for one week in subjects suffering from Major Depressive Disorder.
  • Part B of the CLEO Phase 2 study: assessing the efficacy and safety profile of CLE-100 in subjects with Major Depressive Disorder who have had inadequate response to standard antidepressant therapies. Subjects were randomized in a 1:1 ratio to receive CLE-100 or placebo once daily for 4 weeks, followed by 2 weeks post-treatment follow-up. The primary end point of this study is the reduction of symptoms of depression measured by the MADRS (Montgomery-Åsberg Depression Rating Scale) from baseline to week 4.
    We have completed enrollment for this study and presented the results at American Society of Clinical Psychopharmacology (ASCP) 2023 – Details on our poster in the Publications & Presentations section.

You can find more information on Clexio’s clinical trials at:

* Patient voices throughout this website are paraphrased examples of typical experiences of people suffering from this disease.
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