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Showing posts with label Galantamine. Show all posts
Showing posts with label Galantamine. Show all posts

Thursday 28 July 2016

Memantine – yet another failed Autism Trial


Memantine (Namenda/ Ebixa) is an Alzheimer’s drug that has been used off-label in autism for many years; but does it actually work?

More than a thousand people with autism have completed clinical trials and yet more trials are in progress. 

A few years ago, at the FDA’s request, the producer of the drug, Forest Laboratories, funded two clinical trials enrolling 903 children with autism.  The results were never fully published because the trials were deemed to have failed to find any positive effect and a note to reflect this is included in each pack of Namenda.

A quick look at ClinicalTrials.gov website shows yet more autism trials in the pipeline.


What is going on?

When Dr Chez made a trial in 2007 he found Memantine to be effective; he has since moved on to stem cell therapy which he also finds to be effective.

The latest study to be published includes Dr Hardan from Stanford, who published that study showing NAC to be effective in autism.  This time his study shows no positive effect.

If you look on the clinical trials site you can see some data for the primary endpoint used in the very big trial funded by Forest Laboratories.  It seems to show 517 responders.







By the time the results were reviewed in detail the conclusion drawn by Forest was “there was no statistically significant difference in the loss of therapeutic response rates between patients randomized to remain on full-dose memantine (n=153) and those randomized to switch to placebo”. 

In other words it does not work.

The drug itself now carries this note:-

8.4 Pediatric Use

The safety and effectiveness of memantine in pediatric patients have not been established.
Memantine failed to demonstrate efficacy in two 12-week controlled clinical studies of 578 pediatric patients aged 6-12 years with autism spectrum disorders (ASD), including autism, Asperger’s disorder, and Pervasive Development Disorder — Not Otherwise Specified (PDD-NOS). Memantine has not been studied in pediatric patients under 6 years of age or over 12 years of age. Memantine treatment was initiated at 3 mg/day and the dose was escalated to the target dose (weight-based) by week 6. Oral doses of memantine 3, 6, 9, or 15 mg extended-release capsules were administered once daily to patients with weights < 20 kg, 20-39 kg, 40-59 kg and ≥ 60 kg, respectively.
In a randomized, 12-week double-blind, placebo-controlled parallel study (Study A) in patients with autism, there was no statistically significant difference in the Social Responsiveness Scale (SRS) total raw score between patients randomized to memantine (n=54) and those randomized to placebo (n=53). In a 12-week responder-enriched randomized withdrawal study (Study B) in 471 patients with ASD, there was no statistically significant difference in the loss of therapeutic response rates between patients randomized to remain on full-dose memantine (n=153) and those randomized to switch to placebo (n=158).


So if it does not work, why do researchers continue to carry out further trials, like the recent one below, including Hardan?



OBJECTIVE:

Abnormal glutamatergic neurotransmission is implicated in the pathophysiology of autism spectrum disorder (ASD). In this study, the safety, tolerability, and efficacy of the glutamatergic N-methyl-d-aspartate (NMDA) receptor antagonist memantine (once-daily extended-release [ER]) were investigated in children with autism in a randomized, placebo-controlled, 12 week trial and a 48 week open-label extension.

METHODS:

A total of 121 children 6-12 years of age with Diagnostic and Statistical Manual of Mental Disorders, 4th ed., Text Revision (DSM-IV-TR)-defined autistic disorder were randomized (1:1) to placebo or memantine ER for 12 weeks; 104 children entered the subsequent extension trial. Maximum memantine doses were determined by body weight and ranged from 3 to 15 mg/day.

RESULTS:

There was one serious adverse event (SAE) (affective disorder, with memantine) in the 12 week study and one SAE (lobar pneumonia) in the 48 week extension; both were deemed unrelated to treatment. Other AEs were considered mild or moderate and most were deemed not related to treatment. No clinically significant changes occurred in clinical laboratory values, vital signs, or electrocardiogram (ECG). There was no significant between-group difference on the primary efficacy outcome of caregiver/parent ratings on the Social Responsiveness Scale (SRS), although an improvement over baseline at Week 12 was observed in both groups. A trend for improvement at the end of the 48 week extension was observed. No improvements in the active group were observed on any of the secondary end-points, with one communication measure showing significant worsening with memantine compared with placebo (p = 0.02) after 12 weeks.

CONCLUSIONS:

This trial did not demonstrate clinical efficacy of memantine ER in autism; however, the tolerability and safety data were reassuring. Our results could inform future trial design in this population and may facilitate the investigation of memantine ER for other clinical applications.
  
Dr Chez? 

So how reliable then are Dr Chez’s other findings?  He is a "big name" in autism research.

Back in 2007 Dr Chez published a very positive study on the use of Memantine in autism. 

Memantine as adjunctive therapy in children diagnosed with autistic spectrum disorders: an observationof initial clinical response and maintenance tolerability.

 

Abstract

Autism and Pervasive Developmental Disorder Not Otherwise Specified are common developmental problems often seen by child neurologists. There are currently no cures for these lifelong and socially impairing conditions that affect core domains of human behavior such as language, social interaction, and social awareness. The etiology may be multifactorial and may include autoimmune, genetic, neuroanatomic, and possibly excessive glutaminergic mechanisms. Because memantine is a moderate affinity antagonist of the N-methylD-aspartic acid (NMDA) glutamate receptor, this drug was hypothesized to potentially modulate learning, block excessive glutamate effects that can include neuroinflammatory activity, and influence neuroglial activity in autism and Pervasive Developmental Disorder Not Otherwise Specified. Open-label add-on therapy was offered to 151 patients with prior diagnoses of autism or Pervasive Developmental Disorder Not Otherwise Specified over a 21-month period. To generate a clinician-derived Clinical Global Impression Improvement score for language, behavior, and self-stimulatory behaviors, the primary author observed the subjects and questioned their caretakers within 4 to 8 weeks of the initiation of therapy. Chronic maintenance therapy with the drug was continued if there were no negative side effects. Results showed significant improvements in open-label use for language function, social behavior, and self-stimulatory behaviors, although self-stimulatory behaviors comparatively improved to a lesser degree. Chronic use so far appears to have no serious side effects.


Making sense of Memantine

Personally, I think it likely that Memantine may indeed have a positive effect in some people with autism.  For most people it probably does no good, but no harm, so it is a harmless placebo that may make the parents feel better and gives the doctor something to prescribe.

Memantine and the very similar Galantamine probably do deserve a place in the long list of drugs and supplements that may be effective in some people.  But how great is that “effect”?  I suspect this is the problem; it is big enough for Dr Chez but not big enough for the others.

I suspect this will be a recurring problem in almost all future autism drug trials.  What is a responder?  How big an effect is a worthwhile effect?

I think a better approach would be to focus on the so-called responders identified by Dr Chez and others.  Document the claimed positive effects and then see if these effects continue when the responders are given a dummy placebo.

This is the approach I use in my trials; when I stop a therapy, I look to see if there is a change.  When you suspend an effective therapy things should get worse.

The hundreds or thousands of kids currently on Memantine should do the same; take a break and see if there is any change, be it positive or negative. 

Many people believe no valid treatments for autism exist and that those thinking otherwise are all deluded.

I think that many people are giving their kids drugs and supplements of no therapeutic value and in some cases are making the situation worse.

However, effective therapies do exist for many people with autism and they stand up to scrutiny.  The effect is apparent to third parties, like teachers and therapists, and when you stop the therapy the positive effect is lost and people notice, only to return when it is restarted.  Then you know it is not wishful thinking and at that point what the FDA says does not really matter and you do not need bother with what subsequent trials say.

So when a reader asked me what I thought about the recent “failed” trial of NAC, to treat social impairment in autism, I took a very relaxed view.  If they had identified 50 kids with classic autism and stereotypy and looked at whether NAC reduced this, I would take note.  They choose the wrong primary endpoint, social impairment, and wasted a lot of money.


A randomized placebo-controlled pilot study of N-acetylcysteine in youth with autism spectrum disorder

Conclusions
The results of this trial indicate that NAC treatment was well tolerated, had the expected effect of boosting GSH production, but had no significant impact on social impairment in youth with ASD
.
      
I only wait to see what happens when Ben Ari publishes the results of his large trial on Bumetanide.  Whatever data they choose to collect, is it going to convince the European Medicines Agency that it is an effective therapy?  I hope so, but nothing would surprise me.

I would love to know how Dr Chez rationalizes the fact that so many others cannot replicate his positive research findings.  But he keeps on going.

Rather off-topic, a recent comment on my post on Clonidine, informed us that this drug, often prescribed off-label in autism and ADHD, really is acting as a sedative to calm the person down. So no effect on core autism.  Sedation does have a role to play in some people’s disorders.  Very low doses of Mirtazapine (Remeron) are also sedating via its effect of central H1 receptors; it occurred to me that this might be a safe long term therapy for some "out of control" people with severe autism; likely safer than the usual antipsychotics. 







Thursday 17 April 2014

Ketamine, Memantine, D-Cycloserin, Magnesium, Fenobam and yet more as Glutamatergic Modulators in Autism (and Fragile X)





 
Much of this blog to date has been connected with aspects related to the neurotransmitter GABA.  It did get rather complicated, but at least for me, it has been highly rewarding. I have identified treatable dysfunctions in Monty, aged 10 with ASD, using Bumetanide and now Clonazepam.

It is also clear that a group of people with autism also benefit from treatment with R-baclofen, a potent GABAB receptor agonist. R-baclofen/Arbaclofen and Arbaclofen Placarbil are not commercially available.  The commercially available drug Baclofen contains R-Baclofen and another substance that, in-effect, works to oppose it and so may be much less effective.

Based on the successful results of this investigation into GABA-related interventions, it would therefore make sense to look in detail at Glutamate, the other neurotransmitter that appears to be dysfunctional in many types of autism.

As with GABA dysfunctions, there are already are some existing treatments for glutamate dysfunctions.

While many researchers have concluded that glutamate is implicated in autism, some think, in effect, there is too much and some think there is too little.  Since we have learnt that in fact within “autism” are many discrete diseases, both groups of researchers might be right. 

In other types of neurological disorders glutamatergic modulators are an emerging therapy and there are many ongoing clinical trials.  Off-label, some of these therapies have been used for decades.  In autism there have been some trials over the years, but as seems to be often the case, they are not followed up to a final undisputed conclusion.  This may be about to change.

Yet again, the mineral Magnesium appears and there is yet another possible explanation for its apparent positive impact, in some cases of autism. 
I imagine that under the umbrella diagnosis of autism, there are those who have a GABA dysfunction and there are those that have a Glutamate dysfunction.  Just to complicate matters, if there is Serotonin dysfunction, this will affect both GABA and Glutamate.  So everything is inter-related and nothing is simple. Fortunately, in medicine, trial and error is a long trusted technique and “stumbled upon” is still a satisfactory explanation; we do not need to understand things 100%.

First we have to look at the terminology and in doing so we stumble upon a novel hypothesis as to what caused autism in the first place, which occurred to me today, but back in 2007 at the University of Mississippi.


Glutamate
Glutamate is the most abundant excitatory neurotransmitter. Glutamate is involved in cognitive functions like learning and memory in the brain.  Too much glutamate can be extremely bad for you and research shows it leads to neuronal death, mental retardation and indeed autism. 

So called Glutamate transporters remove glutamate from the extracellular space. In brain injury or disease, they can work in reverse, and excess glutamate can accumulate outside cells. This process causes calcium ions to enter cells via NMDA receptor channels, leading to neuronal damage and eventual cell death;  this is called excitotoxicity.



So it is plausible that the root cause of the autism is actually a dysfunction of one of the glumate transporters.  The calcium ions are just the messenger.


There are 4 types of glutamate transporter. When there is a dysfunction the following is known to happen:-



·        Over activity of glutamate transporters may result in inadequate synaptic glutamate and may be involved in schizophrenia and other mental illnesses

·        During injury processes such as ischemia and traumatic brain injury, the action of glutamate transporters may fail, leading to toxic buildup of glutamate. 

·        Loss of the Na+-dependent glutamate transporter EAAT2 is suspected to be associated with neurodegenerative diseases such as Alzheimer's disease



Excessive glumate release

Excitotoxicity due to excessive glutamate release and impaired uptake occurs as part of the ischemic cascade and is associated with stroke, autism, some forms of intellectual disability, and diseases like Alzheimer's disease.



Epilepsy and Calcium Channels

Glutamic acid has been implicated in epileptic seizures. Microinjection of glutamic acid into neurons produces spontaneous depolarisations around one second apart, and this firing pattern is similar to what is known as paroxysmal depolarizing shift in epileptic attacks. This change in the resting membrane potential at seizure foci could cause spontaneous opening of voltage-activated calcium channels, leading to glutamic acid release and further depolarization


Too much or too little Glutamate Activity?
Studies propose both hyper-and hypoglutamatergic ideologies for autism.






You may be thinking that somebody is clearly wrong here, but it is not so simple.  We will see later, when we get to the clever people at MIT, that in fact both views may be correct; in some people their autism is improved by inhibiting the specific receptor (mGluR5) and in other people by exciting the same receptor.

GABA & GAD

Glutamate also serves as the precursor for the synthesis of the inhibitory gamma-aminobutyric acid (GABA) in GABA-ergic neurons. This reaction is catalyzed by glutamate decarboxylase (GAD), which is most abundant in the cerebellum and pancreas.

GAD is interesting in itself.  There are two types, GAD67 and GAD65
It appears that anti-GAD antibodies are the trigger that leads to diabetes.  Since the pancreas has abundant GAD, a direct immunological destruction occurs in the pancreas and the patients will have developed diabetes.

Diabetes

Both GAD67 and GAD65 are targets of autoantibodies in people who later develop type 1 diabetes or latent autoimmune diabetes. Injections with GAD65 has been shown to preserve some insulin production for 30 months in humans with type 1 diabetes

Schizophrenia and bipolar disorder

Substantial dysregulation of GAD mRNA expression, coupled with down regulation of reelin, is observed in schizophrenia and bipolar disorder. The most pronounced down regulation of GAD67 was found in hippocampal stratum oriens layer in both disorders.

Parkinson disease

The bilateral delivery of GAD by an adeno-associated viral vector into the subthalamic nucleus of patients between 30 and 75 years of age with advanced, progressive, levodopa-responsive Parkinson disease resulted in significant improvement over baseline during the course of a six-month study

Cerebellar disorders

Intracerebellar administration of GAD autoantibodies to animals increase the excitability of motoneurons and impairs the production of nitric oxide (NO), a molecule involved in learning. Epitope recognition contributes to cerebellar involvement

Stiff Person Syndrome

Anti-GAD antibodies are associated with Stiff-person syndrome but their causal role is not yet established.

We have seen before that comorbidities of autism can point us in the right direction and also that many mental health / neurological disorders are overlapping.
So is not a surprise that a GAD dysfunction also exists in autism:-




“This suggests a disturbance in the intrinsic cerebellar circuitry in the autism group potentially interfering with the synchronous firing of inferior olivary neurons, and the timing of Purkinje cell firing and inputs to the dentate nuclei. Disturbances in critical neural substrates within these key circuits could disrupt afferents to motor and/or cognitive cerebral association areas in the autistic brain likely contributing to the marked behavioral consequences characteristic of autism.
Both GAD isoforms have been shown to be affected in a variety of psychiatric and developmental disorders. GAD67 has been implicated in schizophrenia, bipolar disorder, major depression disorder, and autism.
In animal studies, GAD65 is strongly implicated in anxiety.
Clinical research indicates that discrete cerebellar lesions, in otherwise healthy children, cause behavioral and/or cognitive impairments. In autism, however, cerebellar pathology is likely acquired during critical developmental period(s) when the brain is capable of constructing alternate innervation patterns. It is thus possible that there is a “miswiring” of key circuits in the autistic cerebellum with a developmental basis persisting into adulthood


We see again a form of self-destruction.  With arthritis the body destroys its joints and with diabetes, the pancreas is (partially) destroyed.
From the research it would appear that low levels of GAD67 and GAD65 played a critical role in the process that initiated the brain damage that led to autism.  Perhaps the low levels are the result of GAD antibodies.


GAD antibodies test as a predictor
There is a widely available of a GAD antibodies test.  Because diabetes is so common, it is also well researched.





So now back to autism.  Now, I am thinking that maybe pregnant mothers might have high levels of GAD antibodies and this might be passed on to the developing fetus, potentially causing brain damage (autism) or perhaps diabetes later in life.  Well, somebody has already come to the same conclusion.



“Conclusions

Studies of serum GAD-Abs in autism are warranted but have not been done so far. Positive findings would stimulate the development of specific prenatal diagnostic markers and therapeutics that may involve maternal administration of immunosuppressants to prevent the development of
autism or intravenous immunoglobulins therapy in children with emerging autistic symptoms.”

This again points towards immunomodulation as a therapy, this time for the mother.  Such treatment, in mothers with high GAD-Abs (GAB antibodies) might lead to a reduction is in cases of autism and indeed diabetes (type 1).

In the case of children and adults with autism, treatment with GAD65 or GAD67 might be effective, or it might just be too late to do any good.  This would be worthy of study.




Glutamate receptors

Glutamate receptors are responsible for the glutamate-mediated excitation of neural cells, and are important for neural communication, memory formation, learning, and regulation.
Glutamate receptors are implicated in a number of neurological conditions. Their central role in excitotoxicity and prevalence in the central nervous system has been linked or speculated to be linked to many neurodegenerative diseases, and several other conditions have been further linked to glutamate receptor gene mutations.

There are four types of glumate receptors.

The first three types are Ionotropic, and by definition, are ligand-gated nonselective cation channels that allow the flow of K+, Na+ and sometimes Ca2+ in response to glutamate binding.  Upon binding, the agonist will stimulate direct action of the central pore of the receptor, an ion channel, allowing ion flow and causing excitatory postsynaptic current (EPSC). This current is depolarizing and, if enough glutamate receptors are activated, may trigger an action potential in the postsynaptic neuron


AMPA receptor
 
The fourth type is:_
 
These receptors are involved in Ca2+  and K+  ion channels and varying the concentration of Ca2+  and K+  
Glutamate binding to the extracellular region of an mGluR causes G proteins bound to the intracellular region to be phosphorylated, affecting multiple biochemical pathways and ion channels in the cell. Because of this, mGluRs can both increase or decrease the exitability of the postsynaptic cell, thereby causing a wide range of physiological effects.
 


Selected Conditions associated with Glumate Receptors (source Wikipedia)

Attention deficit hyperactivity disorder (ADHD)

In 2006 the glutamate receptor subunit gene GRIN2B (responsible for key functions in memory and learning) was associated with ADHD.  This followed earlier studies showing a link between glutamate modulation and hyperactivity.

Further mutations to four different metabotropic glutamate receptor genes were identified in a study of 1013 paediatric ADHD patients compared to 4105 non-ADHD controls, replicated in a subsequent study of 2500 more patients. Deletions and duplications affected GRM1, GRM5, GRM7 and GRM8. The study concluded that "CNVs affecting metabotropic glutamate receptor genes were enriched across all cohorts (P = 2.1 × 10−9)", "over 200 genes interacting with glutamate receptors were collectively affected by CNVs", "major hubs of the (affected genes') network include TNIK50, GNAQ51, and CALM", and "the fact that children with ADHD are more likely to have alterations in these genes reinforces previous evidence that the GRM pathway is important in ADHD".


In 2012 UPenn and MIT teams have independently converged on mGluRs as players in ADHD and autism. The findings suggest agonizing mGluRs in patients with ADHD or certain forms of autism and antagonizing the targets in other forms of autism

 
Although the precise molecular basis of the interaction remains to be determined, the data show unambiguously that mGluR5 and FMRP act as an opponent pair in several functional contexts, and support the theory that many CNS symptoms in fragile X are accounted for by unbalanced activation of Gp1 mGluRs. These findings have major therapeutic implications for fragile X syndrome and autism.



Autism

The etiology of autism may include excessive glutaminergic mechanisms.
A link between glutamate receptors and autism was also identified via the structural protein ProSAP1/SHANK2 and potentially ProSAP2/SHANK3. The study authors concluded that the study "illustrates the significant role glutamatergic systems play in autism" and "By comparing the data on ProSAP1/Shank2−/− mutants with ProSAP2/Shank3αβ−/− mice, we show that different abnormalities in synaptic glutamate receptor expression can cause alterations in social interactions and communication. Accordingly, we propose that appropriate therapies for autism spectrum disorders are to be carefully matched to the underlying synaptopathic phenotype.

Seizures

Glutamate receptors have been discovered to have a role in the onset of epilepsy. NMDA and metabotropic types have been found to induce epileptic convulsions. Using rodent models, labs have found that the introduction of antagonists to these glutamate receptors helps counteract the epileptic symptoms.  Since glutamate is a ligand for ligand-gated ion channels, the binding of this neurotransmitter will open gates and increase sodium and calcium conductance. These ions play an integral part in the causes of seizures. Group 1 metabotropic glutamate receptors (mGlu1 and mGlu5) are the primary cause of seizing, so applying an antagonist to these receptors helps in preventing convulsions.




 Current and Future interventions


 
The possible interventions that follow from what we have learnt would appear to be:-
1.     Targeting NMDA glutamate receptor function
2.     Targeting mGluRs (metabotropic glutamate receptors)
3.     Targeting glutamate transporters
4.     GAD therapy

There would seem to be four possible areas of intervention.  The first one is to target the NMDA glutamate receptors using existing drugs and other three are cleverer, but only possible using experimental drugs. 
Very few pharmacological tools are currently available to investigate glumate transporter (EAAT) function and to then consider these transporters  as therapeutic targets, but even that is beginning to change.  Here is a Glutamate Transporter Inhibitor:-
 



I do like the idea of targeting GAD. It is possible to do it and the idea is being developed by a company called Neurologix as a treatment for Parkinson’s Disease (PD).  There are also working on epilepsy treatment.
 


"Neurologix's gene therapy approach to PD aims to reset the overactive brain cells to inhibit electrical activity and return brain network activity to more normal levels. The strategy involves restoring GABA and thus improving the patient's motor control by using an AAV vector (a disabled, non-pathogenic virus) to deliver the GAD gene back into the STN (subthalamic nucleus). Increasing GAD causes more GABA to be synthesized, thus helping to calm the STN over-activity."
 
They are calling it gene therapy for PD; I would call it GAD therapy.  I think GAD therapy might well be effective in some types of autism.
 

mGluRs

 
Targeting mGluRs is very much associated with a researcher called Mark Bear at MIT.  We came across him earlier in this blog, since he is also the man behind Arbaclofen, at Seaside Therapeutics.
 
This research is very recent and is linked to Fragile X.  Here is a PhD thesis written in 2013 by one of Mark Bear’s students, which seems to sum things up.
 



If you can follow my blog, you can definitely follow his thesis.  In effect, what he is saying is that errors in synaptic protein synthesis are behind several types of autism and that these errors can be corrected using either positive or negative stimulators of the receptor mGluR5.  It is clear that at Bear Lab, they view all autisms as part of a family, rather than discrete disorders.
 



















This would imply that positive allosteric modulators and negative allosteric modulators of MGluR5 are potentially effective autism treatments.  Another name would be MGluR5 agonist/antagonist.  Such drugs are already under study in both autism and other conditions.  Here are two examples.
 






Seaside Therapeutics, Roche and Novartis have each developed therapeutic compounds targeting the mGluR5 pathway.


Roche is developing RG7090, an inhibitor of mGluR5 that is currently in clinical trials. CTEP is a mouse version of RG7090.  One dose of CTEP, which can be taken orally, deactivates most mGLuR5 receptors in the brain for about 48 hours.


It took four weeks of continued treatment to see improvements in the behavioral features of the syndrome, including sensory sensitivities and problems with learning and memory.

 

Fenobam

 
Fenobam is an existing inhibitor of mGluR5, developed in the 1970s.  It was trialed in Fragile X in 2009 with good results using just a single dose.
 


“In summary, this trial did not find major safety concerns to a single administration of fenobam in FXS, and suggested that clinical improvements in behaviour and PPI may be seen even after a single dose. This would indicate that placebo controlled trials of fenobam and other mGluR5 antagonists involving longer term treatment of individuals with FXS should be considered to investigate whether rescue of the FXS phenotype observed in animal models can be extended to humans.”

Fenobam is being trialed byWashington University, but not for autism.
 



Current interventions

 
The current interventions are mainly NDMA receptor antagonists and are based on that trusted medical approach called trial and error, rather than the Bear Lab approach .  The drugs are:-

·        Ketamine
·        Memantine,
·        D-Cycloserine
·        Magnesium
·        Fenobam (mGluR5 inhibitor – see above, not FDA approved)
 


Chemicals that deactivate the NMDA receptor are called antagonists. NMDAR antagonists fall into four categories: 

  1. Competitive antagonists, which bind to and block the binding site of the neurotransmitter glutamate
  2. noncompetitive antagonists, which inhibit NMDARs by binding to allosteric sites
  3. Uncompetitive antagonists, which block the ion channel by binding to a site within it
  4. glycine antagonists, which bind to and block the glycine site







    Ketamine is a non-competitive antagonist.  It has recently been in the headlines for having a remarkable effect in some cases of depression.
    In large doses it is used as an anaesthetic particularly in children and pet animals.  It is also used as a recreational drug “Special K”, which is why it is a controlled substance.
    In small doses the intra-nasal route is favoured.  In effect the vial of ketamine normally administered by injection is diluted with a saline solution and put in a standard metered dose nasal spray.  It is also possible to make eye drops the same way.  The nasal/eye route is effective since the drug can enter the bloodstream without the need for an injection or a very ineffective oral tablet.
    A study is underway in Cincinnati to test intranasal ketamine on adults with autism.

    Dr. Logan Wink, Cincinnati Children's Hospital
    Start Date: 11/2013
    In a human clinical trial with 24 adults with Autism, researchers at the Cincinnati Children’s Hospital will conduct a pilot double-blind placebo controlled study of intranasal ketamine in adults with ASD using novel quantitative outcome measures of social and communication impairment.
    Ketamine has a unique drug profile clearly differentiated from other glutamatergic modulators (drugs that support the glutamate receptors) studied in ASD to date. This profile, coupled with ketamine’s long safety track record and novel intranasal (IN) delivery system, make ketamine worthy of drug investigation for treatment of the core features of ASD. As a generically available inexpensive drug, ketamine holds significant promise to widely treat the core social and communication impairments that are the hallmark of ASD. The results of this study, if positive, would support the use of a drug with a demonstrated safety profile that is cost-effective to use.
    If this pilot project demonstrates efficacy and tolerability of IN ketamine, the next steps will include the following. 1) Design and obtain funding for a large phase II placebo controlled trial of ketamine in adults with ASD. 2) Design a pilot study of ketamine in children with ASD. 3) Publish the data on the pilot study for other researchers and clinicians to use to support patients with ASD.

    Memantine is an uncompetitive agonist.  It has a modest effect in moderate-to-severe Alzheimer's disease.  It has been around for a long time, having been first synthesized in 1968.
    There are two other Alzheimer’s drugs that seem to be helpful in some types of autism.  They are Donepezil (Aricept) and  Galantamine   They are both centrally acting reversible acetylcholinesterase inhibitors.  So they work in an entirely different way to Memantine.
    There have been several trials of Memantine in autism over the years.  Recently the producer, Forest Laboratories have been intensive trials to show its effectiveness and safety in childhood autism.
    In 2007 Michael Chez carried out a study:- 
                                 
    Open-label add-on therapy was offered to 151 patients with prior diagnoses of autism or Pervasive Developmental Disorder Not Otherwise Specified over a 21-month period. To generate a clinician-derived Clinical Global Impression Improvement score for language, behavior, and self-stimulatory behaviors, the primary author observed the subjects and questioned their caretakers within 4 to 8 weeks of the initiation of therapy. Chronic maintenance therapy with the drug was continued if there were no negative side effects. Results showed significant improvements in open-label use for language function, social behavior, and self-stimulatory behaviors, although self-stimulatory behaviors comparatively improved to a lesser degree. Chronic use so far appears to have no serious side effects.
     Autism speaks have funded studies:-
     

    Even the Iranians have been trialing it, but as usual as an adjunct therapy.


    Forest Laboratories have a series of trials underway of Memantine in autism
    The full list is here
    It appears that Forest have terminated what was to be a two year study.  Here is a blog post by one of the parents:-
     
    D-Cycloserine is a glycine antagonist.  Its main use is as an antibiotic for treating drug resistant TB.  It is also used to treat drug addiction and social anxiety disorder.
    It has been investigated in both mouse models of autism and in humans.

    Abstract
    OBJECTIVE: The authors assessed the effects of d-cycloserine on the core symptom of social impairment in subjects with autism. METHOD: Following a 2-week, single-blind placebo lead-in phase, drug-free subjects with autistic disorder were administered three different doses of d-cycloserine during each of three 2-week periods. Measures used for subject ratings included the Clinical Global Impression (CGI) scale and Aberrant Behavior Checklist. RESULTS: Significant improvement was found on the CGI and social withdrawal subscale of the Aberrant Behavior Checklist. d-Cycloserine was well tolerated at most of the doses used in this study. CONCLUSIONS: In this pilot study, d-cycloserine treatment resulted in significant improvement in social withdrawal. Further controlled studies of d-cycloserine in autism appear warranted.
    Direct stimulation of NMDARs with D-cycloserine, a partial agonist of NMDARs, normalizes NMDAR function and improves social interaction in Shank22/2 mice.

    These results suggest that reduced NMDAR function may contribute to the development of ASD-like phenotypes in Shank22/2 mice, and mGluR modulation of NMDARs offers a potential strategy to treat ASD.
     
    Magnesium
    Magnesium is an uncompetitive NMDA channel blocker.  As you can see below on the diagram of the NMDA receptor site  (source Wikipedia)
     
    1. Cell membrane
    2. Channel blocked by Mg2+ at the block site (3)
    3. Block site by Mg2+
    4. Hallucinogen compounds binding site
    5. Binding site for Zn2+
    6. Binding site for agonists(glutamate) and/or antagonist ligands(APV)
    7. Glycosilation sites
    8. Proton biding sites
    9. Glycine binding sites
    10. Polyamines binding site
    11. Extracellular space
    12. Intracellular space

    Magnesium seems to have a therapeutic effect in some types of autism.  There are several possible reasons why this might be and these have been covered in earlier posts.  The idea of using magnesium to block dysfunctional NMDA receptors is intriguing.  It is clear from the graphic that the receptor has evolved with this specifically in mind.
    There are two simple ways to raise the concentration of magnesium, one is orally and the other is trans-dermally.  A problem with the oral route is that magnesium tends to upset the stomach and that is why it is used as laxative.
    The clever transdermal route is take a bath in Epsom salts (MgSO4) this will raise the level of magnesium (also sulphate).
    Many people take such baths to feel better and look better, but be aware they also will reduce your blood pressure.  Some celebrities claim to take a daily bath in Epsom salts.
    While some parents report that their child with ASD has behavioral improvements after an Epsom salt bath, in Monty, aged 10 with ASD, the reverse is true.  It does not make him calm, it agitates him.
    Since it is cheap and widely available, an Epsom salt bath is not a bad thing to try.  Maybe it helps and maybe it will not; you will only know by trying.
     
    Conclusion
    Most likely in some subtypes of autism there is too much (hyper-function) glutamate activity, in some subtypes there is too little (hypo-function) and in other sub-types glutamate function is not impaired at all.  This is again saying that sub-types are different diseases.
    For the time being, the only therapy would be one of trial and error with existing drugs.
    Intranasal ketamine therapy is intriguing, but this might be hard to get hold of unless you are in a clinical trial, or your neighbour is a vet.
     I have had very good success using ketamine eye drops in varying dilutions from 1:100 down to 1:5. Some of the responses have been quite remarkable. I also make ketamine nasal spray 1:25 and 1:10 and monitor its use because of a slight potential for abuse.”   Dr Jay Goldstein, treating various neurological disorders
    Memantine has now been trialed in over 1,000 children.  If it was highly effective in a large percentage of people, I think we would have heard about it.  It looks to be the "wrong" Alzheimer's drug , the other two, Donepezil and Galantamine seem more beneficial for ASD.


    One long-existing mGluR5 inhibitor, Fenebam, has already been trialed on people with Fragile X.  Until other drugs are developed, I wonder why this drug has been forgotten.
    In the medium term, the new mGluR5 positive and negative modulators look like they may be able to address core defects in some sub-types of autism.  This would be a case where hard science and medicine really did work as they should (i.e. together).  I would put my money on this being the most effective Glutamate-related therapy. 
    I personally like to look for the route cause, as far back up the chain of events as possible, to where the trouble began, and that might point to GAD therapy, but that is far in the future.