Major Depressive Disorder

Depression is a Global Public Health Concern

Depression is a serious medical illness and a global public health concern. The World Health Organization (WHO) estimates that “depression is the leading cause of disability worldwide, and is a major contributor to the global burden of disease,” affecting 350 million people globally. The National Institutes of Mental Health (NIMH) reported that, in 2014, an estimated 15.7 million adults aged 18 or older in the U.S. had at least one major depressive episode in the past year, which represented 6.7 percent of all U.S. adults. According to the U.S. Center for Disease Control and Prevention (CDC), “about one in 10 Americans aged 12 and over takes antidepressant medication.” 

While most people will experience depressed mood at some point during their lifetime, Major Depressive Disorder (MDD) is different. MDD is the chronic, pervasive feeling of utter unhappiness and suffering, which impairs daily functioning. Symptoms of MDD include diminished pleasure in activities, changes in appetite that result in weight changes, insomnia or oversleeping, psychomotor agitation, loss of energy or increased fatigue, feelings of worthlessness or inappropriate guilt, difficulty thinking, concentrating or making decisions, and thoughts of death or suicide and attempts at suicide. Suicide is estimated to be the cause of death in up to 15% individuals with MDD. 

For many people, depression cannot be controlled for any length of time without treatment. Standard medications available in the multi-billion dollar global antidepressant market, including commonly prescribed selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs), have limited effectiveness, and because of their mechanism of action, must be taken for several weeks or months before patients experience any significant therapeutic benefit. In addition, most standard antidepressants have an FDA-required “Black Box” safety warning due to a risk, in certain groups, of worsening depression and an increased risk of suicidal thoughts and behaviors during treatment, a property not expected to occur with AV-101. About two out of every three people that suffer from depression, including an estimated 6.9 million drug-treated MDD patients in the U.S., do not receive adequate therapeutic benefits from their initial treatment with a standard antidepressant and the likelihood of achieving remission of depressive symptoms declines with each successive treatment attempt. Even after multiple treatment attempts, approximately one out of every three depression sufferers still fails to find an effective standard antidepressant. In addition, this trial and error process and the systemic effects of the various antidepressants involved increases the risks of patient tolerability issues and serious side effects, including suicidal thoughts and behaviors in certain groups.

Ketamine Catalyzes New Treatment Paradigm

Ketamine hydrochloride (ketamine) is an FDA-approved, rapid-acting general anesthetic administered intravenously. The use of ketamine (an NMDA receptor (NMDAR) antagonist which acts as an NMDA channel blocker) to treat MDD has been studied in several clinical trials conducted by depression experts at the U.S. National Institute of Mental Health (NIMH), including Dr. Carlos Zarate, Jr., the NIMH’s Chief of Experimental Therapeutics & Pathophysiology Branch and of the Section on Neurobiology and Treatment of Mood and Anxiety Disorders. In randomized, placebo-controlled, double blind clinical trials reported by Dr. Zarate and others at the NIMH, a single intravenous (I.V.) low dose of ketamine (0.5 mg/kg over 40 minutes) produced robust and rapid antidepressant effects in MDD patients who had not responded to standard anti-depressants. These results were in contrast to the very slow onset of SSRIs and SNRIs that usually require many weeks or months of chronic usage to achieve similar antidepressant effects. The potential for widespread therapeutic use of current FDA-approved ketamine, a Schedule III drug, for the treatment of MDD is limited by its potential for abuse, dissociative and psychosis-like side effects, and by practical challenges associated with the necessity of I.V. administration in a medical center. Notwithstanding these limitations, however, the discovery of ketamine’s fast-acting antidepressant effects revolutionized thinking about the current MDD treatment paradigm and increased interest in the development of a new generation of antidepressants with a fast-acting mechanism of action similar to ketamine’s. Our orally available AV-101 is among the next generation of antidepressants with potential to deliver fast-onset ketamine-like antidepressant effects, without ketamine’s side effects or required I.V. administration in a medical setting.

AV-101: A Potential Breakthrough in Depression Treatment and Major Depressive Disorder

AV-101 is an orally available prodrug candidate that produces, in the brain, 7-Cl-KYNA, one of the most potent and selective antagonists of the GlyB site of the NMDAR, resulting in the down-regulation of NMDAR signaling. Growing evidence suggests that the glutamatergic system is central to the neurobiology and treatment of MDD and other mood disorders. 

AV-101’s mechanism of action is fundamentally differentiated from all standard antidepressants and all atypical antipsychotics often used to augment inadequate response with standard antidepressants, placing it among a new generation of glutamatergic antidepressants with potential to treat millions of MDD sufferers worldwide who are poorly served by SSRIs, SNRIs and other current depression therapies. AV-101 is functionally similar to ketamine in that both are NMDAR antagonists. However, AV-101 modulates (down-regulates) NMDAR channel activity and ketamine blocks it. AV-101 accomplishes this NMDAR modulation by selectively binding to the functionally required GlyB site of the NMDAR, thus down-regulating the NMDAR in a dose-dependent manner. We believe targeting the GlyB site of the NMDAR and modulating NMDAR activity rather than blocking it can bypass adverse effects that result when ketamine blocks the NMDA ion channel, without affecting the robust efficacy observed in previous clinical studies conducted by the NIH and others using ketamine to treat MDD. This NMDAR modulation by AV-101 may then result in the “glutamate surge” and the increase in neuronal connections that has been associated with the fast-acting antidepressant effects of ketamine. 

In recently published preclinical studies, AV-101 has demonstrated the antidepressant-like activity of ketamine, including rapid onset and long duration of effect, without causing ketamine’s serious side effects. In two NIH-funded randomized, double blind, placebo-controlled Phase 1 safety studies, AV-101 was safe, well-tolerated and not associated with any severe adverse events. There were no signs of sedation, hallucinations or schizophrenia-like side effects often associated with ketamine and traditional NMDAR channel blockers.

AV-101 Clinical Development

The safety data from two NIH-funded AV-101 Phase 1 clinical safety studies indicate that AV-101 was safe and well tolerated in healthy subjects at all doses tested. 

Although the Phase 1 safety and pharmacokinetic studies were not designed to measure or evaluate the potential antidepressant effects of AV-101, approximately 9% (5/54) of the subjects receiving AV-101 and 0% of the 30 subjects receiving placebo reported “feelings of well-being” similar to the fast-acting antidepressant effects reported in the literature with ketamine. 

Building on over $8.8 million of prior grant award funding from the NIH for preclinical and Phase 1 clinical development of AV-101, in February 2015, we entered into our CRADA with the NIMH. Under the CRADA, we are collaborating with Dr. Carlos Zarate and the NIMH on a Phase 2a clinical study of AV-101 in subjects with treatment-resistant MDD. Pursuant to the CRADA, this study is being conducted at the NIMH by Dr. Zarate and being fully-sponsored by the NIMH. The primary objective of the NIMH-funded Phase 2a study will be to evaluate the ability of AV-101 to improve overall depressive symptomatology in subjects with MDD, specifically whether subjects with MDD have a greater and more rapid decrease in depressive symptoms when treated with AV-101 than with placebo. The first patient in this Phase 2a study was dosed in November 2015. We anticipate top line results in this study in the second quarter of 2017. 

We are currently preparing to launch our Phase 2b clinical study of AV-101 for the adjunctive treatment of MDD in patients with an inadequate response to standard antidepressants. We anticipate the launch of this potentially pivotal multi-center, multi-dose, double blind, placebo-controlled Phase 2b efficacy and safety study, which is expected to enroll approximately 315 patients, in the fourth quarter of 2016. The Principal Investigator of the study will be Dr. Maurizio Fava of Harvard Medical School. Dr. Fava was the co-Principal Investigator with Dr. A. John Rush of the largest clinical trial ever conducted in depression, STAR*D, whose findings were published in journals such the New England Journal of Medicine (NEJM) and the Journal of the American Medical Association (JAMA). 

To Learn more about our ongoing clinical trial, please click the below link or visit 

  1. Antidepressant Effects of the Glycine Receptor Antagonist AV-101 (4-chlorokynurenine) in Major Depressive Disorder

To review key facts and a comprehensive overview on depression, visit the following link: World Health Organization Depression Fact Sheet.