Low dose suramin and autism: a small RCT with potentially big results

'Low dose' has been a feature of my autism research reading this week; first starting with the results from Dan Quintana and colleagues [1] talking about some important effects following intranasal delivery of low dose oxytocin and then moving on to the primary reason for this entry with results from Robert Naviaux and colleagues [2] (open-access) continuing a research theme looking at suramin and autism (see here for some background).

For those interested in the oxytocin-autism research base, I can recommend following Dr Quintana on Twitter (find him here).

In relation to the Naviaux findings  - the "Suramin Autism Treatment-1 (SAT-1) trial" - well, they are open-access but I want to provide some overview and then a little bit of discussion. I might add that this research team are making research waves in several areas of medical science as per their research foray into chronic fatigue syndrome (CFS) recently (see here). Such 'metabolomic' research is pertinent to their autism research too.

This time around as on previous research occasions, the focus was on suramin - the "century-old sleeping sickness drug" - and, as far as I can see, the first time said drug has been tested experimentally with children diagnosed with an autism spectrum disorder (ASD). The accompanying ClinicalTrials.gov trial entry is here.

As per the title to this blog entry, this was a small trial including only 10 participants, all male, aged between 5-14 years old. This was a randomised-controlled trial (RCT) with a placebo element to it too, so half of the participants got suramin - "a single, intravenous infusion of suramin (20 mg/kg)" - and half got saline as a control. Alongside looking at behaviour and functioning, researchers also took blood and urine samples "for safety and toxicity monitoring at 5 times throughout the study." This was accompanied by quite a bit of effort to look at the possibility of adverse events related to suramin or placebo administration.

Results: "A single intravenous dose of suramin was associated with improved scores for language, social interaction, and decreased restricted or repetitive behaviors measured by ADOS, ABC, ATEC, and CGI scores. None of these improvements occurred in the five children who received placebo." The authors also do the right thing by stating: "The generalizability of these findings is unknown." I'm particularly impressed that the ATEC gets a showing given the rise and rise of this autism research tool (see here) in various placebo-controlled contexts (see here).

In relation to the safety aspect to suramin, well, it seemed to do alright. We are told that: "Extensive monitoring revealed no serious toxicities" so one can assume that the 'first, do no harm' tenet was upheld in this trial. But there was one important side-effect noted: "Five children who received suramin developed a self-limited, evanescent, asymptomatic, fine macular, patchy, morbilliform rash over 1–20% of their body." The rash was short-lived and did not require specific attention/intervention but it's worthwhile noting it especially when nothing similar was reported in the placebo group.

Going back to the mention of this research group delving into CFS with metabolomics in mind, so similar results are reported on the basis of examination of plasma samples from participants. Various biological pathways seemed to be affected by the infusion of suramin, not least "the importance of the cell danger response (CDR) [3]... and purinergic signaling." Interestingly, authors also noted effects in relation to "1-carbon, folate, methionine, and cysteine metabolism" too, potentially linked to other findings independently reported in relation to autism (see here for example).

Reiterating again that this was a small study (albeit using the gold-standard in scientific methodologies) these results are rather interesting and potentially quite important. They most definitely point to the requirement for further large-scale studies to look at any effects in a larger participant group and to 'zoom in' on potential best-responders to this type of intervention. I end with an important conclusion from the authors who again, have not over-stated their findings:

"Suramin is not approved for the treatment of autism. Like many intravenous drugs, when administered improperly by untrained personnel, at the wrong dose and schedule, without careful measurement of drug levels and monitoring for toxicity, suramin can cause harm. Careful clinical trials will be needed over several years at several sites to learn how to use low-dose suramin safely in autism, and to identify drug–drug interactions and rare side effects that cannot currently be predicted. We strongly caution against the unauthorized use of suramin."

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[1] Quintana DS. et al. Dose-dependent social-cognitive effects of intranasal oxytocin delivered with novel Breath Powered device in adults with autism spectrum disorder: a randomized placebo-controlled double-blind crossover trial. Transl Psychiatry. 2017 May 23;7(5):e1136.

[2] Naviaux RK. et al. Low-dose suramin in autism spectrum disorder: a small, phase I/II, randomized clinical trial. Annals of Clinical & Translational Neurology. 2017. 26 May.

[3] Naviaux RK. Metabolic features of the cell danger response. Mitochondrion. 2014; 16: 7-17.

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Naviaux, R., Curtis, B., Li, K., Naviaux, J., Bright, A., Reiner, G., Westerfield, M., Goh, S., Alaynick, W., Wang, L., Capparelli, E., Adams, C., Sun, J., Jain, S., He, F., Arellano, D., Mash, L., Chukoskie, L., Lincoln, A., & Townsend, J. (2017). Low-dose suramin in autism spectrum disorder: a small, phase I/II, randomized clinical trial Annals of Clinical and Translational Neurology DOI: 10.1002/acn3.424

Suramin and the Fragile X (Fmr1 knockout) mouse model (and autism)

Fancy some weekend reading? Well, you could do a lot worse than having a gander through the paper by Jane Naviaux and colleagues [1] (open-access) discussing the results of a whole host of analyses following the use of the antipurinergic agent suramin on a mouse model of Fragile X syndrome.

Overprotective mother, forbidden road trip...

Regular readers might remember some previous discussions about suramin - a pharmaceutic designed to treat African sleeping sickness - and autism which have graced this blog (see here and see here). Following a series of studies which looked at the physiological and behavioural effects of suramin administration on a mouse model trying to recreate conditions of maternal immune activation (MIA (which itself has some autism research history), authors this time turned their attention to a mouse model of Fragile X syndrome, a condition which can in humans manifest with autistic traits (sometimes).

The Naviaux paper is a whopper in terms of data accumulated and results so I'm not going to even try and summarise the findings aside from quoting the authors that their: "results support the novel conclusion that antipurinergic therapy is operating by a mechanism that lies close to the root cause of the core behaviors and development in both the environmental MIA, and the genetic Fragile X models of ASD [autism spectrum disorder]. This mechanism appears to be traceable to mitochondria and regulated by purinergic signaling." Both mitochondrial and purinergic issues have featured in the autism research historical tapestry before (see here and see here respectively).

Just before anyone makes a run on suramin, I might however point out a few things: (a) the current and previous results are based on mouse studies and mice are mice not humans, and (b) suramin, whilst indicated for sleeping sickness, is not without the possibility of some pretty important side-effects (see here).

Still, this latest paper again potentially opens up a number of promising lines of inquiry in need of further investigation. And the added bonus is to see some more metabolomics included in their results!

To close: INXS and Mystify.

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[1] Naviaux JC. et al. Antipurinergic therapy corrects the autism-like features in the fragile X (Fmr1 knockout) mouse model. Molecular Autism 2015, 6:1

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Jane C Naviaux, Lin Wang, Kefeng Li, A Taylor Bright, William A Alaynick, Kenneth R Williams, Susan B Powell, & Robert K Naviaux (2015). Antipurinergic therapy corrects the autism-like features in the fragile X (Fmr1 knockout) mouse model Molecular Autism : 1186/2040-2392-6-1

More suramin and autism [mouse] findings

The headline: 'Century-old drug reverses signs of autism in mice' brought the paper by Jane Naviaux and colleagues [1] (open-access) to my attention and some slightly familiar work (see here) on the use of suramin in a mouse model of autism, or rather a mouse model of maternal immune activation. Indeed, I seem to remember that the previous study by this group [2] courted similar publicity, with some familiar headlines...

Not lecturing... @ Wikipedia 

The latest offering from Naviaux et al is not so dissimilar from their previous work on that mouse model of autism, this time testing "the hypothesis that the behavioral manifestations of the MIA [maternal immune activation] model are a consequence of pathological persistence of the evolutionarily conserved CDR [cell danger response]... and that the CDR is maintained by dysregulated purine metabolism and secondary abnormalities in purinergic signaling". The press release about the study can be viewed here.

What this all translates into is that a state of immune arousal above and beyond what would be typically expected during pregnancy is somehow impacting on offspring development pertinent to an elevated risk of conditions like autism or schizophrenia. There is quite a bit of literature on this topic from the autism perspective (see here) and based on animal models other than just rodents (see here). The cell danger response (CDR) described by Naviaux (Robert that is) [3] represents "the evolutionarily conserved metabolic response that protects cells and hosts from harm". Indeed that last reference [3] contains just about every biological link known to autism science at the current time... including mitochondria. The idea is that triggering immune activation activates "a conserved cellular response to stress" called the CDR and the proposed master regulator of the CDR is purinergic signalling [4] - "purine nucleotides and nucleosides as extracellular messengers". ATP (adenosine triphosphate) as well as being quite an important molecular fuel source, is suggested to be one of the nucleotides which "can bind to cell surface receptors and act as signaling molecules and neuromodulators that are important in inflammation.. neurotransmission.. and many other biological processes".

A few basic points about the Naviaux study:

• Mice were the lucky volunteers for this study, and again the 'good breeder' that is the C57BL/6J variety. As per their previous trial, pregnant female mice were given something to artificially stimulate their immune system and "initiate the MIA model" or a saline control and then their offspring were the study focus.
• Suramin or saline (as a control) was then administered to 6-month old offspring mice and thereafter "behaviors were evaluated". Suramin levels were also examined, as were a broad range of metabolites as part of some metabolomic analysis based on the use of triple quad mass spectrometry.
• Results: "MIA animals showed social deficits from an early age". Nothing too novel there bearing in mind previous observations in this area of research. But... "Single-dose APT [antipurinergic therapy] with suramin completely reversed the social abnormalities in 6.5-month-old adults". Social behaviour by the way, was quantified as "time spent interacting with a novel ("stranger") mouse".
• The benefit of suramin also lasted for quite a while: "a small residual benefit to social behavior was still detectable" even after 5 weeks following the intervention. There is some discussion by the authors about this effect; noted to be potentially "due to the development of metabolic memory and/or somatic epigenetic DNA changes that lasted longer than the physical presence of the drug".
• Then the biochemistry. Suramin seemed to by-pass that very important gateway, the blood-brain barrier (BBB) and end up in the brainstem following some analysis of sacrificed offspring mice: "consistent with the notion that nuclei in brainstem, or their projection targets in distant sites of the brain, may mediate the dramatic behavioral effects of acute and chronic APT in this model".
• And more: "Comprehensive metabolomic analysis revealed disturbances in several other metabolic pathways relevant to children with ASDs. These included disturbances in microbiome, phospholipid, cholesterol/sterol, sphingolipid, glycolytic and bile salt metabolism". This bearing in mind that only "male animals that had been behaviorally evaluated were tested". Purine metabolism and the gut microbiome seemed to be quite important to the author's results. At this point I'll refer you back to the work by Elaine Hsiao and colleagues... 
• Moreover: "The top, non-microbiome-associated metabolite was quinolinic acid... which was decreased in the MIA model". Quinolinic acid implies the involvement of one of those aromatic amino acids, tryptophan, which is an autism research favourite [5]. More than that is the literature on the intersecting kynurenine pathway and how that might relate to a condition like schizophrenia (see here).
• The authors caution that their results are (a) mouse based and (b) "suramin is a poor drug choice for chronic use because of potentially toxic side effects that can occur with prolonged treatment". That being said, they do suggest that "new drugs might be given only once, or intermittently, during sensitive windows to unblock metabolism, restore more normal neural network function, improve resilience and plasticity, and permit improved development in response to behavioral and interdisciplinary therapies, and to natural play". Just in case you'd like an alternative reading of this study, have a look at this write-up too.

I do apologise for all the quotes taken from the Naviaux paper and used in this post, but when the authors say it better than I could, why would I try and complicate things any further? Indeed, the more I read the paper by Naviaux and colleagues, the more I see what a potential gem it actually is. I say this based on the pretty comprehensive way that the authors went about looking at the MIA model and the effect of their intervention, crossing behavioural (mouse behavioural) and biochemical fields. Mention of the words 'microbiome' and 'metabolome' are also guaranteed to perk my interest. All that enthusiasm is however tempered dependent on the work being replicated and not just in a mouse model either.

A few closing comments are all that are required. Looking at the list of biochemical pathways altered in the MIA model of autism (see Table 1 here) we see lots of familiar names too numerous to mention. Outside of looking at the effect of suramin on these pathways, I'm minded to suggest that other interventions might also benefit from some similar inspection of their effects on said pathways. Even as one commentator has already noted: "[The findings] are valuable, but the main problem is that they rely on a model of immune infection, not a genuine model of autism... They should have tested one of the classical models of autism... meaning genetic models of autism — to see whether suramin indeed corrects autistic behaviors".

I've also not really gone into the detail when it comes to the cell danger response (CDR) in this post because it is a complicated area and seems to tie into various issues which are slightly beyond my level of expertise. I would like to bring in the letter by Theoharides [6] at this point however, and his discussion linking "extracellular mitochondrial material" to mast cell activation (see here) on the back of the previous study by this authorship group, as another area crying out for further investigation.

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[1] Naviaux JC. et al. Reversal of autism-like behaviors and metabolism in adult mice with single-dose antipurinergic therapy. Translational Psychiatry. 2014; 4: e400; doi:10.1038/tp.2014.33

[2] Naviaux RK. et al. Antipurinergic therapy corrects the autism-like features in the poly(IC) mouse model. PLoS One. 2013;8(3):e57380.

[3] Naviaux RK. Metabolic features of the cell danger response. Mitochondrion. 2014 May;16:7-17.

[4] Burnstock G. Pathophysiology and therapeutic potential of purinergic signaling. Pharmacol Rev. 2006 Mar;58(1):58-86.

[5] Boccuto L. et al. Decreased tryptophan metabolism in patients with autism spectrum disorders. Mol Autism. 2013 Jun 3;4(1):16.

[6] Theoharides TC. Extracellular Mitochondrial ATP, Suramin, and Autism? Clinical Therapeutics. 2013; 35: 1454-1456.

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Naviaux JC, Schuchbauer MA, Li K, Wang L, Risbrough VB, Powell SB, & Naviaux RK (2014). Reversal of autism-like behaviors and metabolism in adult mice with single-dose antipurinergic therapy. Translational psychiatry, 4 PMID: 24937094

Autism, maternal immune activated mice and suramin

Avid followers of the autism research circuit must have noticed the increasing tide of studies looking at a possible role for maternal immune activation (MIA) in relation to risk of offspring autism spectrum disorder (ASD). It's a topic I've covered more than once on this blog; predominantly in relation to the work of people like Paul Patterson and his colleagues (see here), observations on things like C-reactive protein (see here) and the various ways to experimentally mimic such MIA in the mouse model of autism / schizophrenia / other for example (see here).

Squeakers @ Wikipedia  

So it is in this post that I'm serving a double helping of the MIA model of autism as per the publication of studies from Jared Schwartzer and colleagues from the MIND Institute* (open-access) and Robert Naviaux and colleagues** (open-access).

Both studies looked at the effects of artificial induction of MIA in the mouse model following poly I:C use as an immunostimulant. Thereafter the two studies went their separate ways as Schwartzer looked at the variable of mouse strain on the after-effects of MIA on offspring and Naviaux looked at the role of purinergic signaling.

I'll say right now that I am neither qualified nor experienced enough to go into these papers with any great detail. So I won't; instead a brief overview of each - bearing in mind their open-access status - and some interesting factoids which have already been mentioned in the autism research peer-reviewed domain which might tie into results.

The work of Schwartzer and colleagues basically "indicate[s] the need to consider how genetic predisposition may exacerbate or protect against the effects of environmental insults in the etiology of ASD". In other words, based on a mouse model looking at different strains of mouse, the specific genetic make-up of that mouse model might impact on offspring presentation after an artificial MIA event.

In their case they looked at the C57BL/6J and BTBR T+tf/J inbred mouse strains and concluded that the dangermouse that is the BTBR strain combined with the poly I:C stressor seemed to "be synergistic resulting in greater behavioral impairment than from either factor alone" when compared with the C57BL/6J mouse strain. Some interesting variables are noted including elevations in cytokines like IL-6 (see here) and IL-17 (see here) in the BTBR offspring mice compared to C57BL/6J mice alongside some sex specific behavioural differences. All in all, some very interesting observations; and on that sex-specific notion, not completely at odds with other work in this area (see here).

The work of Naviaux and colleagues - summarised quite well here - has definitely taken the interest of the media as per headlines such as 'New drug that may help reverse autism' or should that be 'Century old drug could beat autism'. I'm confused. The long-and-short of it is that based on the analysis of the MIA mouse model - C57BL/6J mice - there was a suggestion that "hyperpurinergia is a fundamental and treatable feature of the multisystem abnormalities in the poly(IC) mouse model of autism spectrum disorders". Treatable via "antipurinergic therapy (APT)" which in this study was via the drug suramin. The observant reader should immediately be comparing Schwartzer and Naviaux and the MIA mouse models chosen and results obtained.

Anyhow, Naviaux et al continue in their observations on how MIA affected offspring mice and how the administration of suramin seemed to have some pretty wide-ranging effects on offspring mice. Alongside various behavioural effects on social and coordination issues, suramin administration was reported to show important effects such as "the preservation of cerebellar Purkinje cells", which as I discussed in a recent post, have more than a token link to cases of autism. "Suramin treatment strongly increased the expression of the nicotinic acetylcholine receptor subunit α7 (nAchRα7) in cerebral synaptosomes of MIA animals" was another potentially important finding in view of other work in this area. In all, "16 multisystem features of this model were either corrected or improved by suramin treatment".

Impressive stuff I hear you say. Indeed all the more impressive given that the authors on purpose did not start suramin treatment until 6 weeks because they "wished to test the hypothesis that many of the autism-like features of the MIA model were treatable after they appear". And apparently there is more to come according to the authors, with the promise of human trials of suramin...

But just before you pop down to your local doctor or pharmacist to ask for suramin (off-label), it might be worth pointing out a few things. Mice. Yep, this was a study of mice and as per the Schwartzer study, not necessarily the best and only mouse model of autism from an MIA point of view. Indeed if I needed to go back to the BTBR mouse and its overlap with autism, I might also recall some work looking at that most forgotten of autism research parameters, sulphate (sulfate) and findings related to the BTBR model (see here). Mice are not humans and suramin is to be added to a growing list of mouse findings with an autism slant (see here and here).

That the US National Cancer Institute holds an entry for suramin should also give you some idea as to what uses the drug has and why bearing in mind it was injected into the study mice. Alongside its anti-parasitic effects related to things like sleeping sickness, the activity of suramin has been linked to its blocking of various growth factor binding which might yet hold some clue to other effects of the drug outside of competitive inhibiting of purinergic signalling (see here and here). As with most medicines, there are other effects to keep in mind which might also tie into results. And then there are the reported side-effects...

I'm not by any means trying to belittle the Naviaux results of suramin in the MIA mouse model of autism so please do not take this post as such. I am very keen to see some replication studies done in other mouse and other animal models, just to see if the results stack up before progressing to human trials with the all-important focus on 'first do no harm' and whether other meds have similar actions. As such I'll keep my eye open for suramin and autism and perhaps post some updates.

In the meantime, the maternal immune activated hypothesis grinds forward...

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* Schwartzer JJ. et al. Maternal immune activation and strain specific interactions in the development of autism-like behaviors in mice. Translational Psychiatry. 2013; 3: e240.

** Naviaux RK. et al. Antipurinergic therapy corrects the autism-like features in the poly(IC) mouse model. PLoS ONE. 2013; 8: e57380.

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Schwartzer JJ, Careaga M, Onore CE, Rushakoff JA, Berman RF, & Ashwood P (2013). Maternal immune activation and strain specific interactions in the development of autism-like behaviors in mice. Translational psychiatry, 3 PMID: 23481627

Naviaux, R., Zolkipli, Z., Wang, L., Nakayama, T., Naviaux, J., Le, T., Schuchbauer, M., Rogac, M., Tang, Q., Dugan, L., & Powell, S. (2013). Antipurinergic Therapy Corrects the Autism-Like Features in the Poly(IC) Mouse Model PLoS ONE, 8 (3) DOI: 10.1371/journal.pone.0057380