Every once in a while as a PhD student you get the chance to be involved in a major project. Spanning years of work and generations of PhD and postdoc contracts these behemoths of science are the sorts of studies that you can really celebrate. Yesterday our paper on boron-based inhibitors of the NLRP3 inflammasome was published in the journal Cell Chemical Biology. This project, culminating 10 years of work, 20 authors, over 100 pages of supplementary information was a quite frankly mammoth effort by my supervisor Dr David Brough, Dr Sally Freeman and all those involved over the last decade. I thought if such a mega study doesn’t deserve a short blog to summarise in a page or so (yeah good luck) then what will??

Why are we doing this??

So, let’s set the scene. Why are we even doing this? Our lab work on inflammatory disease, with a specific focus on stroke and on Alzheimer’s disease. These are absolutely devastating conditions. Stroke is a leading cause of disability in the UK (2/3 stroke survivors eave hospital with a disability) and Alzheimer’s (now ranked the most feared disease) costs the UK economy $26 billion annually. Part of the reason these diseases are so devastating is the lack of effective treatments. The only effective treatment for ischemic stroke (the most common type of stroke) is useless if given after a ~4 hour window (think about how likely you are to notice, call an ambulance, correctly diagnose then administer treatment in that time) and there is currently no disease modifying treatment for Alzheimer’s with current drugs only really taming the symptoms.

This is where we come in. There’s a huge amount of evidence that an overactive immune system can be involved in a vast array of diseases that you wouldn’t usually associate with immune activation, Alzheimer’s, stroke, atherosclerosis, diabetes, schizophrenia to name just a few. We call this phenomenon ‘sterile inflammation’. The process of sterile inflammation is initiated by factors called cytokines, these small, soluble proteins send signals to the cells of the immune system that your body is under attack and it needs action, fast. The immune system responds by sending in cells that try to destroy the suspected invaders, often by secreting bleach. As you can imagine, bleach in the brain is not the best idea and we believe that this aberrant immune reaction is at least partially responsible for the irreparable brain damage that occurs in diseases such as Alzheimer’s and stroke. Our aim is to prevent this response and save those brains! The way we are doing this is by trying to find/develop drugs that prevent production of one of the major culprits of the cytokine family, interleukin(IL)-1β. We’re pretty sure that IL-1β can be a bad guy in disease; a recent clinical trial in the US (the CANTOS study) showed that a drug against IL-1β massively cut the risk of a 2^nd heart complication and, astonishingly cut cancer fatalities in half! We’re trying to stop the production of IL-1β by inhibiting a complex called an inflammasome (I know what a name right). We’re previously shown that mefenamic acid, a drug used for period pain, can inhibit the inflammasome and may be effective in Alzheimer’s  but we need more potent therapies – so here we got down and dirty and started making our own!

What did we do?

The project started with a molecule called 2-APB (see fig). This non-specific, dirty compound hits a lot of stuff – mainly affecting calcium signalling. It’s been known for a while that 2-APB also inhibits the inflammasome (along with a million other things) so we used this as our starting compound and began the process of experimental chemistry to see if we could ramp up the effect on the inflammasome at the same time as getting rid of all the nasty off-target effects.

Now here I’ll try and cut down a bit on the 100-odd pages of supplementary figures in the paper and I’ll have to apologise to master chemists Dr Alex Baldwin and Dr Sally Freeman as this summary really does not do enough justice to all the work they did making these drugs. The gist is that through multiple iterations of taking a carbon off here and swapping a nitrogen there we steadily improved our molecule until we ended up with something that was over 100 times more potent at inhibiting the inflammasome and, crucially, no longer had any effects on calcium signalling (which is super important in cells). This process was described as both ‘intelligent design’ and ‘like evolution’ by 2^nd author and staunch atheist Dr. Jack Rivers-Auty and I kinda get what he means. We’ve intelligently designed a molecule that has evolved to become better and better at a specific task, inhibiting the inflammasome. I suppose the evolutionary pressure of us chucking a vial of drug (and months’ worth of work by some very talented chemists) in the bin is fairly strong!

Anyway over a (relatively) fast-forwarded process of intelligently designed evolution we’ve ended up with a molecule called ‘novel boron compound 6’ or NBC6. We’ve tested this drug in a basic model of inflammatory disease in mice and it seems effective. But there’s still a very long way to go!

Graphical abstract – We started with 2-APB (left) and ended up with a much better compound NBC6 (right)

What next?

So what next? Well there’s a huge amount of development still to go. For a start we need to see if this compound (or more likely a version of this compound) is safe long term in animals, then see if it gets to the right bits of the body and isn’t broken down (this stage kills A LOT of potential drugs in drug discovery), then see of it has any effect in animal models of Alzheimer’s and stroke (even if it does that says very little about how good it will be in people) and THEN we can maybe think about getting it into a form that we can give it to people and test it. I can’t really stress enough how far away this is from a therapy for anything – but that’s not the point. These chemicals are a new class of anti-inflammatory compounds and that is really exciting. What’s more is that we can use these drugs as tools in cells to investigate the role of the inflammasome in other diseases and to understand more about how the inflammasome functions. We still don’t know how the drug actually works – so there’s an exciting project to keep an eye out for in the future!

The important thing is that the paper is out and now the scientific community can kick into gear and use this knowledge to work together on developing new treatments for diseases like Alzheimer’s and stroke. It’s been a huge project lasting 10 years and the paper is finally out, the funny thing is though, we’ve really only just started.

Paper links:

http://dx.doi.org/10.1016/j.chembiol.2017.08.011 

https://www.nature.com/articles/ncomms12504