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Other names | CERC-301; MK-0657 |
Routes of administration | By mouth |
Drug class | Selective NMDA receptor antagonist |
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Chemical and physical data | |
Formula | C19H23FN4O2 |
Molar mass | 358.417 g·mol−1 |
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Rislenemdaz (developmental code names CERC-301, MK-0657) is an orally active, selective NMDA receptor subunit 2B (NR2B) antagonist which is under development by Cerecor in the United States as an adjunctive therapy for treatment-resistant depression (TRD). [1] In November 2013, phase II clinical trials were initiated, [2] and in the same month, rislenemdaz received Fast Track Designation from the Food and Drug Administration for TRD. [3]
A pilot study was published in 2012, [1] and a phase II trial was completed in 2014, but was deemed insufficient. [4] A second attempt at a phase II trial in 2016 also found that the drug failed to demonstrate efficacy against depression. [5]
Rislenemdaz is a small-molecule antagonist of the NMDA receptor. The NMDA receptor is composed of several subunits, but rislenemdaz is specific for the GluN2B subunits which are only seen in the spinal cord and forebrain. Rislenemdaz binds specifically to the GluN2B subunit in order to prevent endogenous glutamate from acting on it. It is considered to be a novel drug for the treatment of MDD and TRD for its immediate onset of efficacy in an oral dosage form. [6] Rislenemdaz and its active metabolite have been shown to have an onset of action of about 1 hour and half-lives of 12–17 h and 21–26 h, respectively. [1] [7] It has been proven to have a very high binding affinity for its target (Ki = 8.1 nM). [1] This specificity allows rislenemdaz to mitigate the symptoms of depression without having many adverse effects due to off-target binding. [7]
Cerecor acquired the exclusive rights from Merck in 2013 to develop an NMDA receptor antagonist for the treatment of major depressive disorder (MDD). This compound acquired from Merck would eventually become rislenemdaz. [8] Funds generated through the IPO of Cerecor in 2015 and a common stock purchase agreement with Aspire Capital Fund in 2016 are being used to further develop the molecule. [9] [10] Cerecor currently holds three families of patents regarding rislenemdaz in the United States as well as several other countries. These patents cover composition of matter, methods of manufacture, methods of use, as well as picture claims to rislenemdaz and any pharmaceutical salts of it. These patents will being to expire in 2022 but some will not expire until 2035. [11]
Commercial competitors of the drug include Naurex's apimostinel (NRX-1074) and 4-chlorokynurenine (AV-101) from VistaGen Therapeutics. [12]
Research into the use of ketamine to treat MDD had already determined that the drug could have effectiveness in rapidly reducing the symptoms of depression. [13] Unfortunately ketamine has powerful dissociative effects, leaving patients in a trance-like state after administration and lending itself to recreational abuse. In 2008 a proof of concept study was conducted by Pfizer using the NR2B antagonist traxoprodil, which proved that drugs similar to ketamine could be used to treat depressive symptoms without causing the dissociative effect seen in that drug. [14] Traxoprodil was eventually dropped from development due to bioavailability issues and the possibility of it causing QT prolongation.
The first preclinical study of rislenemdaz was conducted in 2015 and was primarily geared towards assessing the molecule's safety and pharmacokinetic profile in rats and a small group of men. The study showed that rislenemdaz was very orally bioavailable, rapid acting, and that it was safe compared to other similar molecules which had caused neurodegenerative problems in rats. [7] A clinical trial with 135 subjects revealed that rislenemdaz does not have any influence on ECG in humans as is seen in traxoprodil. [15]
Rislenemdaz initiated its first phase II randomized double blind clinical trial (NCT01941043) in November, 2013. This study was funded through a $32 million Series B Financing tranche led by venture capital companies such as New Enterprise Associates (NEA), Apple Tree Partners (ATP) and MPM Capital. [16] The trial consisted of 135 patients diagnosed with MDD who were resistant to SSRI/SNRI treatment. The study lasted 28 days and saw patients receiving 8 mg/day doses of rislenemdaz in order to see a change in the Hamilton Depression Rating Scale (HDRS) of the patient by day 7, but no significant changes were noted. [15] [6]
However, in March 2015, Cerecor announced that the 8 mg dose for the study did not meet the primary objective for the study, although the study showed the safety and tolerance of rislenemdaz. The company also announced that in a separate study, higher daily doses of drug were able to safely treat patients, indicating that higher doses of drug could be used in future clinical trials. [6]
Cerecor conducted a second double blind, randomized, placebo controlled phase II clinical trial (NCT02459236) studying the effects of 12 mg/day and 20 mg/day doses of rislenemdaz on patients with MDD. Numerous changes were made to the study in order to achieve a great likelihood of success and new top-line data from this study in November 2016. [6] However, the study reported in November 2016 that the drug failed to demonstrate efficacy. [5]
Ketamine is a dissociative anesthetic used medically for induction and maintenance of anesthesia. It is also used as a treatment for depression and in pain management. Ketamine is an NMDA receptor antagonist which accounts for most of its psychoactive effects.
The N-methyl-D-aspartatereceptor (also known as the NMDA receptor or NMDAR), is a glutamate receptor and predominantly Ca2+ ion channel found in neurons. The NMDA receptor is one of three types of ionotropic glutamate receptors, the other two being AMPA and kainate receptors. Depending on its subunit composition, its ligands are glutamate and glycine (or D-serine). However, the binding of the ligands is typically not sufficient to open the channel as it may be blocked by Mg2+ ions which are only removed when the neuron is sufficiently depolarized. Thus, the channel acts as a "coincidence detector" and only once both of these conditions are met, the channel opens and it allows positively charged ions (cations) to flow through the cell membrane. The NMDA receptor is thought to be very important for controlling synaptic plasticity and mediating learning and memory functions.
Esketamine, sold under the brand names Spravato and Ketanest among others, is the S(+) enantiomer of ketamine. It is a dissociative hallucinogen drug used as a general anesthetic and as an antidepressant for treatment of depression. Esketamine is the active enantiomer of ketamine in terms of NMDA receptor antagonism and is more potent than racemic ketamine.
Levomilnacipran is an antidepressant which was approved in the United States in 2013 for the treatment of major depressive disorder (MDD) in adults. It is the levorotatory enantiomer of milnacipran, and has similar effects and pharmacology, acting as a serotonin–norepinephrine reuptake inhibitor (SNRI).
Traxoprodil is a drug developed by Pfizer which acts as an NMDA antagonist, selective for the NR2B subunit. It has neuroprotective, analgesic, and anti-Parkinsonian effects in animal studies. Traxoprodil has been researched in humans as a potential treatment to lessen the damage to the brain after stroke, but results from clinical trials showed only modest benefit. The drug was found to cause EKG abnormalities and its clinical development was stopped. More recent animal studies have suggested traxoprodil may exhibit rapid-acting antidepressant effects similar to those of ketamine, although there is some evidence for similar psychoactive side effects and abuse potential at higher doses, which might limit clinical acceptance of traxoprodil for this application.
Rapastinel is a novel antidepressant that was under development by Allergan as an adjunctive therapy for the treatment of treatment-resistant depression. It is a centrally active, intravenously administered amidated tetrapeptide that acts as a novel and selective modulator of the NMDA receptor. The drug is a rapid-acting and long-lasting antidepressant as well as robust cognitive enhancer by virtue of its ability to enhance NMDA receptor-mediated signal transduction and synaptic plasticity.
ALTO-100, previously known as NSI-189, is a drug described as a hippocampal neurogenesis stimulant and indirect brain-derived neurotrophic factor (BDNF) modulator which is under development for the treatment of major depressive disorder (MDD), bipolar depression, and post-traumatic stress disorder (PTSD). There has also been interest in ALTO-100 for possible treatment of cognitive impairment and neurodegeneration. It is taken by mouth.
7-Chlorokynurenic acid (7-CKA) is a tool compound that acts as a potent and selective competitive antagonist of the glycine site of the NMDA receptor. It produces ketamine-like rapid antidepressant effects in animal models of depression. However, 7-CKA is unable to cross the blood-brain-barrier, and for this reason, is unsuitable for clinical use. As a result, a centrally-penetrant prodrug of 7-CKA, 4-chlorokynurenine (AV-101), has been developed for use in humans, and is being studied in clinical trials as a potential treatment for major depressive disorder, and anti-nociception. In addition to antagonizing the NMDA receptor, 7-CKA also acts as a potent inhibitor of the reuptake of glutamate into synaptic vesicles, an action that it mediates via competitive blockade of vesicular glutamate transporters.
Apimostinel is an investigational antidepressant, acting as a novel and selective modulator of the NMDA receptor. It is currently under development for the acute treatment of major depressive disorder (MDD) by Gate Neurosciences, and previously by Naurex and Allergan. As of February 2015, an intravenous formulation of apimostinel has completed a phase IIa clinical trial for MDD.
Basimglurant (INN) is a negative allosteric modulator of the mGlu5 receptor which is under development by Roche and Chugai Pharmaceutical for the treatment of treatment-resistant depression and fragile X syndrome. As of November 2016, it has undergone phase II clinical trials for both of these indications.
Hydroxynorketamine (HNK), or 6-hydroxynorketamine, is a minor metabolite of the anesthetic, dissociative, and antidepressant drug ketamine. It is formed by hydroxylation of the intermediate norketamine, another metabolite of ketamine. As of late 2019, (2R,6R)-HNK is in clinical trials for the treatment of depression.
L-4-Chlorokynurenine is an orally active small molecule prodrug of 7-chlorokynurenic acid, a NMDA receptor antagonist. It was investigated as a potential rapid-acting antidepressant.
Cycloserine/lurasidone, developmental code name NRX-101 and tentative brand name Cyclurad, is a combination formulation of the antibiotic D-cycloserine, an antagonist of the glycine site of the NMDA receptor, and lurasidone, an atypical antipsychotic, which is under development by NeuroRx for the treatment of acute suicidal ideation/behavior (ASIB). As of May 2016, it has completed a phase II clinical trial for bipolar depression. In September 2017, the drug received fast track designation for bipolar depression from the United States Food and Drug Administration.
Dextromethorphan/bupropion (DXM/BUP), sold under the brand name Auvelity, is a combination medication for the treatment of major depressive disorder (MDD). Its active components are dextromethorphan (DXM) and bupropion. Patients who stayed on the medication had an average of 11% greater reduction in depressive symptoms than placebo in an FDA approval trial. It is taken as a tablet by mouth.
Tulrampator is a positive allosteric modulator (PAM) of the AMPA receptor (AMPAR), an ionotropic glutamate receptor, which is under development by RespireRx Pharmaceuticals and Servier for the treatment of major depressive disorder, Alzheimer's disease, dementia, and mild cognitive impairment. Tulrampator was in phase II clinical trial for depression, but failed to show superiority over placebo. There are also phase II clinical trials for Alzheimer's disease and phase I trials for dementia and mild cognitive impairment.
EVT-103, also known as ENS-103, is an experimental medication which originated from Roche and is under development by Evotec AG for the treatment of major depressive disorder. It acts as an NMDA receptor subunit 2B (NR2B) antagonist. As of November 2017, no recent reports of development for major depressive disorder have been identified. The drug was developed as a follow-up compound to EVT-101. The chemical structure of EVT-103 has not been released.
NV-5138 is an orally and centrally active small-molecule drug which is under development by Navitor Pharmaceuticals for the treatment of major depressive disorder (MDD). It directly and selectively activates the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway by binding to and modulating sestrin2, a leucine amino acid sensor and upstream regulatory pathway. The mTORC1 pathway is the same signaling pathway that the NMDA receptor antagonist ketamine activates in the medial prefrontal cortex (mPFC) to mediate its rapid-acting antidepressant effects. A single oral dose of NV-5138 has been found to increase mTORC1 signaling and produce synaptogenesis in the mPFC and to induce rapid antidepressant effects in multiple animal models of depression. Like those of ketamine, these actions require the signaling of brain-derived neurotrophic factor (BDNF). The antidepressant effects following a single dose of NV-5138 are long-lasting, with a duration of up to 7 days, and are similar to those of ketamine. Based on these promising preclinical findings, efforts are underway to assess NV-5138 in clinical trials with human subjects. By November 2019, NV-5138 had completed three phase I studies for the treatment of MDD. In these studies, preliminary evidence of efficacy, tolerability, safety, and pharmacokinetics was observed, and as of 2021 it was into Phase II trials.
Psychoplastogens are a group of small molecule drugs that produce rapid and sustained effects on neuronal structure and function, intended to manifest therapeutic benefit after a single administration. Several existing psychoplastogens have been identified and their therapeutic effects demonstrated; several are presently at various stages of development as medications including ketamine, MDMA, scopolamine, and the serotonergic psychedelics, including LSD, psilocin, DMT, and 5-MeO-DMT. Compounds of this sort are being explored as therapeutics for a variety of brain disorders including depression, addiction, and PTSD. The ability to rapidly promote neuronal changes via mechanisms of neuroplasticity was recently discovered as the common therapeutic activity and mechanism of action.
Ketamine-assisted psychotherapy(KAP) is the use of prescribed doses of ketamine as an adjunct to psychotherapy sessions. KAP shows significant potential in treating mental disorders such as treatment-resistant depression (TRD), anxiety, obsessive–compulsive disorders (OCD), post-traumatic stress disorders (PTSD), and other conditions. It can also be used for those experiencing substance abuse and physical pain. While it is primarily used as a veterinary anaesthetic, ketamine has also been found to have rapid analgesic and hallucinogenic effects, which has sparked interest in its use as an antidepressant. Despite initial trials of its use in the treatment of mental disorders focussing primarily on its antidepressant effects, newer studies are attempting to harness its psychedelic effects to bring about altered states of consciousness, which will augment the adjunct psychotherapy. Ketamine's neuroplasticity-promoting effects strengthen the cognitive restructuring that takes place through traditional psychotherapy, thereby leading to long-lasting behavioural change. KAP offers promising directions for research on new antidepressant alternatives, but is still not sufficiently defined or evaluated as a treatment combination.