GABRA5 - Too much, or too little in Autism and Down Syndrome?

 

It is easy to get things the wrong way round.

This applies to science and to some people getting dressed

 

Today’s post was prompted by a reader updating me about Roche’s autism drug RO7017773, which targets the alpha 5 sub-unit of GABA_A receptors, encoded by the gene GABRA5.

Enrollment opens in phase II study of RO-7017773 for autism spectrum disorder

A 12-Week Placebo-Controlled Study to Investigate the Efficacy, Safety, and Tolerability of RO7017773 in Participants Aged 15-45 Years With Autism Spectrum Disorder (ASD)

 

Some people with severe autism, or just plain old ID/MR, which has gone out of fashion as a diagnosis these days, struggle to dress themselves because they do not notice what is inside out, or back to front.  I recall reading a few years ago about one autism parent who started a clothing company to get round this problem.

 

ADAPTIVE CLOTHING with no front/back and reversible so cannot be inside out.

 

I must say that writing this blog I am often left wondering which way round things are.  Do we want an agonist or an antagonist, a positive allosteric modulator or a negative one.  Many times things do seem to work backwards.

If you follow the research you will see that researchers often get things mixed up, with one group trying one strategy and yet another group of Ivy league bright-sparks doing exactly the opposite. The Vasopressin research is a good example.

Are they dyslexic? Perhaps dyspraxic?

Today it is the turn of GABRA5: do we want to upregulate it, or downregulate it?

GABRA5 is the gene that encodes the alpha 5 sub-unit of GABAa receptors.

A few years ago, the drug firm Roche spent a lot of money developing a negative modulator of these receptors.  That did not work and Basmisanil  (developmental codes RG-1662 and RO5186582) was abandoned as a treatment to raise cognition in Down syndrome.

Roche are now trialing the opposite therapy, a positive allosteric modulator of alpha 5 sub-unit of GABAa receptors, this time to treat autism.

 

Targeting GABA to treat autism

GABA is an important neurotransmitter and it seems to be dysfunctional in many types of autism, as well as other neurological conditions.

Both the A-type and the B-type of GABA receptors can respond to treatment.

When it comes to the A-type, we can be very clever and target specific sub-units of the receptor to achieve different goals.

 

Each receptor is made up of two α subunits, two βs and one γ.

In humans, the possibilities are made up of :

·         six types of α subunits (GABRA1, GABRA2, GABRA3, GABRA4, GABRA5, GABRA6)

·         three βs (GABRB1, GABRB2, GABRB3)

·         three γs (GABRG1, GABRG2, GABRG3)

 

What is particularly interesting is that the make up these receptors is not fixed, it is changing all the time and you can influence it with therapy.

It looks like you might even be able to treat alcohol addiction by targeting one of the sub-units.

In the world of autism it is more anxiety and cognition that we are targeting, but some types of seizure may also be targeted.

In previous posts I identified alpha 3 (GABRA3)  and alpha 5 (GABRA5) as subunits that I felt were the interesting ones to improve cognition in autism.  Alpha 3 is the target of the low dose clonazepam therapy.

Alpha 5 also fits in with my experience of inflammation-induced reduction in cognitive function.

 

α5 GABAA Receptors Regulate Inflammation-Induced Impairment of Long-Term Potentiation 

these results show that α5GABA_A receptor activity increases during inflammation and that this increase is critical for inflammation-induced memory deficits.

 

We know that female hormones modulate subunit expression, today we see that oxytocin also does this. So, yet another possible effect of a little more oxytocin.

 

Oxytocin modulates GABA_AR subunits to confer neuroprotection in stroke in vitro

Before I forget, I should add that that the nootropic herb Bacopa affects GABRA5 (in rats):-

https://www.sciencedirect.com/science/article/pii/S0753332218383914

“BME (Bacopa monnieri) significantly reversed the down-regulated Gabra1, Gabra4, Gabra5 gene expression of GABAA receptors subunits”

 

The following paper has been published since I wrote my earlier posts on GABRA5 and is very thorough.

 

Neurobiology and Therapeutic Potential of α5-GABA Type A Receptors

α5 subunit containing GABA type A receptors (GABA_ARs) have long been an enigmatic receptor subtype of interest due to their specific brain distribution, unusual surface localization and key role in synaptic plasticity, cognition and memory. These receptors are uniquely positioned to sculpt both the developing and mature hippocampal circuitry due to high overall expression and a distinct peak within the critical synapse formation period during the second postnatal week. Unlike the majority of other GABA_ARs, they exhibit both receptor clustering at extrasynaptic sites via interactions with the radixin scaffold as well as synaptic sites via gephyrin, thus contributing respectively to tonic currents and synaptic GABAergic neurotransmission. α5 GABA_AR signaling can be altered in neurodevelopmental disorders including autism and mental retardation and by inflammation in CNS injury and disease. Due to the unique physiology and pharmacology of α5 GABA_ARs, drugs targeting these receptors are being developed and tested as treatments for neurodevelopmental disorders, depression, schizophrenia, and mild cognitive impairment. This review article focuses on advances in understanding how the α5 subunit contributes to GABA_AR neurobiology. In particular, I discuss both recent insights and remaining knowledge gaps for the functional role of these receptors, pathologies associated with α5 GABA_AR dysfunction, and the effects and potential therapeutic uses of α5 receptor subtype targeted drugs.

 

Genetic Disorders with Altered α5 GABA_AR Neurotransmission

While acute reduction in α5 GABA_ARs has shown potential for improving cognition and memory, further studies both in mouse models and human patients link long term reduction with significant pathologies. Reduced α5 GABA_AR levels, function or protein interactions have been observed in patients with neurodevelopmental disorders including intellectual disability, epilepsy and autism. Common conditions among these disorders include cognitive impairments, increased anxiety, autism-related behaviors, sleep disorders and epilepsy susceptibility

 

α5 GABA_AR Therapeutics

NAMs that selectively reduce α5 GABA_AR function have been heavily pursued for the potential development of cognitive enhancing or “smart” drugs. The following are a selection of α5 GABA_AR NAMs: L-655,708, α5IA, Ro15-4513, MRK-016, RO4938581, and RY-80 Importantly, α5 NAMs did not exhibit the convulsant or pro-convulsant activity of more general alpha subunit NAMs, had good oral bioavailability and easily crossed the blood brain barrierIn contrast to NAMs which act via the GABA_AR benzodiazepine binding site, S44819 was recently identified as a competitive antagonist of GABA at α5 GABA_AR and showed similar pro-cognitive effects as NAMs: blocking α5-GABA_AR tonic current, enhancing LTP, reversing scopolamine-induced impairment of spatial working memory and enhancing object recognition memory). Finally, recent evidence for beneficial effects of positive allosteric modulators (PAMs) in aged brain cognition, autism, depression and schizophrenia has bolstered α5 PAM drug development. A selection of α5 preferring PAMs includes SH-053-R-CH3-2′F, MP-III-022, and GL-II-73. Potential therapeutic applications for α5 preferring NAMs and PAMs are discussed below with a focus on CNS specific uses (Table 1).

 

NAM α5 GABA_AR Therapeutic Applications

Pro-cognition

Developmental Disorders

Although these pharmacological successes led to a Phase II clinical trial for a related compound RG1662 (Hoffman-La Roche) in Down syndrome patients, the trial did not meet the primary and secondary endpoints of improved cognition and function.

Inflammation Induced Mild Cognitive Impairment and Post Anesthesia Memory Blockade

 

 

PAM α5 GABA_AR Therapeutic Applications

Neurodevelopmental Disorders

Mouse models of neurodevelopmental disorders that present with insufficient inhibitory tone show improvement with positive modulators of GABA_AR signaling. In the Scn1a+/− mouse model of Dravet syndrome, a severe childhood epileptic encephalopathy syndrome with hyperactivity and autism behaviors, abnormal social behaviors and fear memory deficits were rescued following treatment with a benzodiazepine, clonazepam. In an ASD mouse model with reduced GABA_AR-mediated inhibition, the BTBR T+tf/J mouse, the α2,3 and 5 PAM L-838,417, improved deficits in social interaction, repetitive behaviors, and spatial learning.

 

Mild Cognitive Impairment in Aging

Although α5 GABA_AR NAMs enhance memory in young rodents, it appears positive modulation may be more therapeutic in aging brains impaired by excess activity. Particularly in disorders such as Alzheimer’s which are hallmarked by overexcitation 

 

Depression and Schizophrenia

Another important unmet need where α5 GABA_ARs PAM pharmacotherapy may be applicable is in the development of new fast-acting anti-depressant drugs

  

 

Roche

Roche did develop a (NAM) drug to target the alpha 5 sub-unit in order to improve cognition in Down Syndrome. 

 

The GABA _A α5-selective Modulator, RO4938581, Rescues Protein Anomalies in the Ts65Dn Mouse Model of Down Syndrome

 

RG1662, a Selective GABAA α5 Receptor Negative Allosteric Modulator, Increases Gamma Power in Young Adults with Down Syndrome.

 

Basmisanil ( RG-1662 and RO5186582) is a highly selective inverse agonist/negative allosteric modulator of α₅ subunit-containing GABA_A receptors which is under development by Roche for the treatment of cognitive impairment associated with Down syndrome. As of June 2016, it is no longer studied.

 

Then came the opposite strategy, a PAM (positive allosteric modulator):-

 

RG 7816

Alternative Names: RG-7816; RO-7017773

 

Mechanism of Action  GABA A alpha 5 receptor modulators

Orphan Drug Status  No

New Molecular Entity  Yes

Highest Development Phases

Phase II  Pervasive child development disorders

Most Recent Events

·         23 Feb 2021Phase-II clinical trials in Pervasive child development disorders (In adolescents, In adults) in Canada (PO) (NCT04299464)

·         12 Mar 2020Hoffmann-La Roche plans a phase II trial for Pervasive child development disorders (Autism Spectrum Disorder) in USA (PO) (NCT04299464) (EudraCT2019-003524-20)

·         22 Apr 2019Roche completes a phase I trial in Pervasive child development disorders (In volunteers) in USA (PO, Capsule, Tablet) (NCT03847987)

 

RG7816 GABA-Aa5 PAM

autism spectrum disorder

4. Phase 1

Description/Summary:

RG7816 is a small molecule highly selective positive allosteric modulator of the GABAA α5 receptor, which is expressed in key brain regions for autism spectrum disorder. Two phase I clinical trial is evaluating RG7816 for the treatment of patients with autism spectrum disorder.

 

Conclusion

Modifying the response specific to sub-units of GABA_A receptors is a really nuanced therapy.

In a way I am not surprised that there is, as yet, no one size fits all therapy.

Will Roche’s trial of a drug to increase the effect of GABRA5 (a PAM) be more successful than their drug to reduce the effect of GABRA5 a (NAM)?

I do not know, but in the perfect world you would have both drugs and then see if fine-tuning GABRA5 ( + or -), on a case by case basis, was therapeutic. That would be personalized medicine.

At least we can modify GABRA3 extremely cheaply with Professor Catterall’s low dose clonazepam.

Note that we saw in my original posts that the Japanese attribute the benefit of low dose clonazepam to the γ2 subunit of GABAa receptors, which is encoded by GABRG2, for those who don’t speak Greek.

 

PX-RICS-deficient mice mimic autism spectrum disorder in Jacobsen syndrome through impaired GABAA receptor trafficking  

A curative effect of clonazepam on autistic-like behaviour

 

These results demonstrate that ASD-like behaviour in PX-RICS^−/− mice is caused by impaired postsynaptic GABA signalling and that GABA_AR agonists have the potential to treat ASD-like behaviour in JBS patients and possibly non-syndromic ASD individuals.

 

Jacobsen syndrome is a condition mainly found in girls and it is one of those more rare small-headed conditions (microcephaly). It features MR/ID and often an autism diagnosis.  It is caused by missing part of chromosome 11, apparently one of the most disease-rich chromosomes.

The fact that low-dose (sub-anxiolytic) clonazepam rescued the autistic behavior in mice does not mean that anyone has tried it in little girls with Jacobsen syndrome; that would require too much common sense.

Pentoxifylline – Clearly an Effective add-on Autism Therapy for some

 

They also had Pentoxifylline for autism back in the 1970s – time for a revival?

 

Pentoxifylline and other more modern PDE inhibitors have been mentioned many times in this blog.

https://epiphanyasd.blogspot.com/search/label/PDE4

https://epiphanyasd.blogspot.com/search/label/Pentoxifylline

Pentoxifylline has been used in autism clinical trials dating back almost 50 years. A casual observer would naturally assume it cannot possibly be effective, or else surely its use would have caught on by now.

Some readers have long been using a PDE inhibitor as part of their child’s autism polytherapy. People have been asking me to let them know my thoughts on Pentoxifylline, the most accessible PDE inhibitor.

I think the key is that we are talking about an add-on, or adjunct, therapy.  We are no longer talking about pentoxifylline therapy vs no therapy, as they were in the 1970s.  Even in those decades-old studies there was a sub group of “super responders”.  Either the percentage of such responders, or the “super-response” itself was just too small to create waves leading to wider adoption.

In my autism world, I had been trying to develop more expressive language using sulforaphane and calcium folinate (leucovorin). A comment from Valentina prompted me to finally start my trial of Pentoxifylline.  It became apparent that the amount of expressive language was increasing, but the major factor was the Pentoxifylline not the calcium folinate (leucovorin).  To avoid GI side effects, I give Pentoxifylline after meals, which means it does sometimes get omitted/forgotten. It emerged that expressive language was clearly correlated to whether Pentoxifylline was taken or forgotten.

Reviewing the old studies, increased use of language does get a mention as an effect of Pentoxifylline.

 

What is the biological effect of Pentoxifylline?

Pentoxifylline is a non-selective PDE inhibitor, which you might think is a bad thing, since it looks like is it just PDE4 that we want to inhibit.

Pentoxifylline is also a non-selective antagonist of adenosine receptors A₁ and A_2A that are located in both the heart and brain.  These two adenosine receptors have important roles in the brain, regulating the release of other neurotransmitters such as dopamine and glutamate.

Pentoxifylline is normally prescribed because of its effects on your blood.  It improves red blood cell deformability, reduces blood viscosity and decreases the potential for platelet aggregation and blood clot formation.  So not a bad potential drug for the effects of severe Covid (which causes "sticky" blood), or indeed the extremely rare negative reaction to Astra Zeneca’s vaccine reported in Norway.  I had my Astra Zeneca Covid shot last week and Monty will be having his. Even young children with severe autism have been vaccinated where we live, at the parents' insistence. It looks like crossing international borders is going to to be much easier with proof of vaccination, so even if you had the virus the vaccine is useful.  Most people we know have had the virus, since where we live public policy was more towards protecting livelihoods than lives.  A lack of obesity and very old people kept the death rate quite low.  Now we seem to have more vaccines than demand for them.

Studies show that Pentoxifylline increases blood flow to the brain.  We know that blood flow to the brain in autism is impaired; the research describes it as unstable rather than just weak.

It sounds like Pentoxifylline is a polytherapy in itself, it has so many effects possibly relevant to autism.

 

Are Ibudilast and Roflumilast/Daxas an alternative to Pentoxifylline?

This question has come up already in the comments section.

We know that Ibudilast and Roflumilast are much more selective for PDE4 than Pentoxifylline.  We know that both Ibudilast and Roflumilast have interesting effects on the brain.

Pentoxifylline has some potentially beneficial effects that are not shared by Ibudilast or Roflumilast.  Pentoxifylline is cheap and proven safe in a series of trials in young children. 

I think that the typical autism dose of Pentoxifylline, 200mg twice a day, likely does not provide the effect on PDE4 provided by the small dose of Roflumilast/Daxas used in trials to improve cognition and sensory gating.

I think you would need to trial the drugs separately and, if they indeed provide a benefit, find the effective combination.  

So far I have trialed the 100 mcg dose of Roflumilast/Daxas on myself to check for GI side effects and see if it affects how thoughts and sensory inputs are processed, as the research suggests it does. I think it does indeed have the cognitive effects, but in me personally the GI effects also appear.  Some readers have told me this 100 mcg dose works for Aspies, and without side effects.

Some readers have tried Ibudilast.

Ling favours Pterostilbene, a natural PDE4 inhibitor. Pterostilbene has many other modes of action, including relating to inflammation, diabetes, aging and even cancer.

  

Conclusion 

Polytherapy is becoming fashionable these days and it is about time too.  Here it is all about MS (Multiple Sclerosis):-

 

UK to test existing drugs as treatment for MS in world-first trial

“Ultimately, MS will be treated with a combination of drugs,” said Gray. “You’ll have immunomodulatory drugs and anti-inflammatory drugs that stop the immune attacks, and they will be combined with treatments that can protect nerves from damage, and treatments that can repair the damaged myelin. That should stop MS.”

 

Each drug, given individually, will not deliver a dramatic result, but in combination the effective can be substantial.

Autism also requires polytherapy.  A few small steps can take you a large stride forwards. 

I did once consider using the analogy of fixing an old car, but I thought people might not like it and also autism develops very early in life not at the end; but Professor Ramaekers used the analogy on me, so I will follow suit.

You may need to fix many things on an old car, to get it back to its former glory.  The more problems you fix, the better the result will be.  You just have to start and keep on going.

In autism, and car restoration, the order in which you fix things does matter.  You probably need to learn this the hard way.

In a near perfect car (Asperger’s) really small issues, like faulty electric windows or squeaky suspension, can be extremely annoying, though the car remains perfectly functional; it gets you from A to B.

Pentoxifylline, by itself, is not going to “cure” anyone’s autism, but for some people it will be another step in that direction.

 

Another old idea has resurfaced - sodium phenylbutyrate (shortened to NaPB).

I think this drug was used for completely the wrong reasons, by a tiny number of people, a decade ago, but now common mouse models of autism are showing that this pan-HDAC inhibitor and ER-stress inhibitor has potent beneficial effects.  It is changing gene expression via an epigenetic mechanism.

If you look on Google, it appears as another quack therapy.

Four autism treatments that worry physicians – LA Times in 2009

Four that worry physicians. The Chicago Tribune examined four treatments in depth. Medical experts said that the therapies have not been proved to help children with autism and that each also carries risks. 

#4 Phenylbutyrate

Kennedy Krieger Institute: “No research conducted into use for autism.” -- Trine Tsouderos and Patricia Callahan

 

https://www.chicagotribune.com/lifestyles/ct-xpm-2009-11-23-chi-autism-science-nov23-story.html

Patricia Kane, who calls herself "the queen of fatty acid therapy," initially sounds like a skeptic of alternative autism treatments. She distances herself from the Defeat Autism Now! approach and says hyperbaric oxygen therapy, IVIG and chelation drugs all can be harmful.

"If you could see what happens to children when they're given some of these crazy interventions that ruin their life, and it's so painful," said Kane, whose office is in New Jersey. "Parents say, 'Patricia Kane will tell us the truth,' and I believe parents deserve the medical truth when it comes to their children."

One of her fans is Kent Heckenlively, a California science teacher who writes for ageofautism.com, self-described as the "daily web newspaper of the autism epidemic." After spending "a couple of hundred thousands" on treatments, from chelation to stem cell therapy, for his daughter with autism, Heckenlively said Kane appealed to him in part because her protocol includes lab tests run by the prestigious Kennedy Krieger Institute.

"I can trust them, I think," Heckenlively said.

Kane, who points to neuroinflammation as a feature of autism, discusses Pardo's study in a chapter she co-wrote on autism treatments for the book "Food and Nutrients in Disease Management."

Kane says many children with autism have a buildup in their brains of a substance called very-long-chain fatty acids. Her "PK Protocol" -- named after her initials -- is aimed at burning them off with a prescription drug, phenylbutyrate, that is normally used to treat extremely rare genetic disorders in which ammonia builds up in the body.

Side effects of phenylbutyrate include vomiting, rectal bleeding, peptic ulcer disease, irregular heartbeat and depression. No clinical trials have evaluated this drug as an autism therapy, and the idea that very-long-chain fatty acids have a role in autism is not proven by science.

Kane is not a medical doctor. When treating children with autism, she says, she works in concert with the child's physician, who supervises treatment.

She said she holds a doctorate in nutrition that was issued by Columbia Pacific University, an unaccredited institution that was shut down after a lengthy court battle with the state of California. An administrative law judge in 1997 found that the school awarded excessive credit for prior experiential learning, failed to employ qualified faculty and didn't meet requirements for issuing degrees.

Kane said Columbia Pacific granted her a doctorate after the school "consolidated my work," which Kane described as "clinical work" and continuing medical education courses for doctors. Her doctorate is valid, she said, because it was issued before the university ran into problems with the state.

Last year she was the subject of a television news investigation about her work with patients with ALS, also known as Lou Gehrig's disease. The disease, which affects motor neurons, is a death sentence.

but now in 2021, things have changed:-

 

Sodium phenylbutyrate reduces repetitive self-grooming behavior and rescues social and cognitive deficits in mouse models of autism

We found that acute and chronic treatment of NaPB remarkably improved, not only core ASD symptoms, including repetitive behaviors and sociability deficit, but also cognitive impairment in the BTBR mice. NaPB substantially induced histone acetylation in the brain of the BTBR mice. Intriguingly, the therapeutic effects of NaPB on autistic-like behaviors, such as repetitive behaviors, impaired sociability, and cognitive deficit also showed in the valproic acid (VPA)–induced mouse model of autism

These findings suggest that NaPB may provide a novel therapeutic approach for the treatment of patients with ASD.

Correcting miss-expressed genes is the holy grail for the treatment of many diseases and in particular for all those parents whose child has a single gene type of autism.  In this blog I also call them DEGs (differentially expressed genes); everyone with autism has some DEGs. There is a lot in this blog about HDAC inhibitors, these can modify gene expression via the epigenome.  HDAC inhitors therefore can potentially fix DEGs.  NaPB was approved 25 years ago by the FDA to treat urea cycle disorders and is used in children over 20 kg.  It is not cheap and as usual it is much more expensive in the United States, at a high dose it is crazily expensive like cancer drugs, many of which are also HDAC inhibitors.  NaPB is another bulk chemical they put in tablets and multiply that cost by whatever they feel like. There is a reaction against this trend in some countries, for example using cheap generic Potassium Bromide for Dravet syndrome, instead of the overly expensive tablets. 

NaPB is used off-label to treat ALS/motor neuron disease.

 

Ski Weekend

 

Monty has been skiing for many years, after a shaky start when he was 5 years old.  He went to a small ski school in Austria where they only teach kids with special needs. The Porsche family own the ski lifts in Zell am See and give the school free tickets, so at least you don’t have to pay for that part.  Skiing is never cheap, but our local slopes are less than four hours drive away and those one-to-one lessons are a fading memory.

Big brother had gone for a week skiing with his friends and he stayed on so he could accompany Monty for 3 days of skiing.

Even though Monty is actual a very safe skier, people tend not to believe it and they think he must have constant supervision.  In reality, he goes up the ski lift with his brother and he can make his way down entirely by himself.  His brother takes him to all the slopes but mainly the black ones (the hardest), far out of sight of their parents.

This year Monty was on skis and his brother was learning snowboarding; Monty was the one arriving first at the bottom.

To be honest, years ago it was really difficult to ski - the boots, the helmet and all the different kinds of ski lift to get used to.  Some people thought I was mad to be encouraging it.  Now skiing is all instinctive, no need for lessons or even reminders.  The myelin is well and truly doing its job.