Interview with Linda Greensmith – A motor neuron expert

Linda Greensmith is a Professor at the Institute of Neurology (IoN), University College London (UCL) and a leading expert for motorneurons.  She did her undergraduate degree in Physiology and PhD in Neuroscience at UCL, and post-doctoral positions at UCL, Imperial College London, in France, and in Boston.

The research of her lab focuses on motorneuron dysfunction and degeneration in neuromuscular disorders, including motor neuron disease (MND, also known as ALS), inclusion body myositis (IBM), spinal bulbar muscular atrophy (SBMA), and Charcot-Marie Tooth Disease (CMT).

Research background: Studying the Motorneuron

So you initially moved to the IoN to accept the Graham Watts Senior Research Fellowship. 

Yes.  The Graham Watts Senior Research fellowship is funded by a bequest from a woman called Eileen Watts, in memory of her brother, Graham Watts, who died, unfortunately, of Motor Neuron Disease (MND) here in our partner Hospital, The National Hospital for Neurology and Neurosurgery.  [She] wanted to set up a bequest which would support research into the underlying causes of MND, also known as ALS.  It established these laboratories, which were the first basic laboratories really focused on MND in the Institute.

It began to expand to a critical mass of people: I’ve had 26 PhD students, numerous post-docs, and now with a number of additional Investigators in the Institute, we form one of the biggest groups in the UK and Europe working on MND with expertise ranging from MND genetics to animal models, to cell and molecular biology to therapy development; the Institute now really has a world class group of people working in MND.

What first led you to study neuromuscular disorders?

I did my PhD at UCL it was very much a developmental project, about how motorneurons first interact with their targets, the muscle, and how that influences how they develop and mature, and how this interaction ensures they survive.  It was mainly focused on understanding the factors that are important for motor neuron survival during a critical period of early development, which may also have relevance for understanding why they may die in adult MND.

Arimoclomol as a potential therapeutic in neuromuscular disease

A long term project you have worked on during your time at the IoN is the therapeutic potential of a novel drug called Arimoclomol.  Arimoclomol seems to be widely applicable to many diseases – you’ve done studies with it in the MNDs ALS and SBMA, and most recently in the muscle disorder IBM.  Can you tell me why this is so widely applicable? 

Diseases are really characterized by their clinical manifestation, and how clinicians define them. IBM, FTD and ALS have been previously considered to be completely different diseases.  However, that doesn’t mean that the underlying pathological mechanisms or causes are in fact completely different.  For example, multisystem proteinopathy is a disease caused by mutations on one gene, VCP, but the disease can manifest as IBM in the muscle, ALS in the CNS or FTD in the brain- or indeed a combination of all three “diseases”, but in each of the specific tissues affected, a common pathological characteristic is protein mishandling – and this is precisely the process that Arimoclomol targets.

So this common feature of protein mishandling means that one drug can target many diseases, in different cells?

For any cell, really.  Its not targeting the upstream cause of any of these disorders.  Most cells will respond to stress of any kind by upregulating this endogenous protective pathway called the heat shock response (HSR).  When you’ve got cells that are under stress, you get protein conformation changes which makes them more likely to misfold and aggregate.  The HSR tries to refold them into usable proteins, and if it can’t do that, it will send them to the cell’s disposal pathways so they don’t aggregate. In many diseases, particularly neurodegenerative diseases such as MND, there may be defects in either the HSR or these degradative pathways, which may contribute to the build up of aggregated, toxic proteins.

So how is Arimoclomol involved in this?

Our protocol is to see whether treatment with Arimoclomol can help the cells to help themselves, by upregulating their endogenous HSR. Although several drugs, and indeed insults, can upregulate the HSR (it’s a normal response to most cell stressors) Arimoclomol acts like a smart drug, in that it only co-induces this HSR in cells that are already under stress.  This is important as it results in a very targeted effect and as a consequence will have fewer off-target, non-specific side effects than drugs that induce the HSR indiscriminately.

How can it identify cells under stress?

Because there are key cellular changes when cells are under stress. For example, the main transcription factor (HSF-1) that regulates the expression of the proteins that are induced in the HSR (called heat shock proteins) becomes activated in conditions of cell stress, and Arimoclomol prolongs this activation, or hyperphosphorylation of HSP-1, which results in the transcription of increased levels of heat shock proteins.

Can you tell me where your Arimoclomol work currently stands?

When we started looking to see whether or not [Arimoclomol] would work in a model of neurodegeneration, we chose ALS.  We found that if we treated a particular mouse model of ALS, the SOD-1 mouse model, we could really alter the disease progression in that mouse: they lived longer, they had better functioning muscles, it was quite an impactful paper that we published in Nature Medicine in 2004.

On the back of this work, Biorex, the Hungarian company which owned Arimoclomol sold it to Cytrx, an American biotech who carried out a safety and tolerability trial in ALS patients, before selling it to a Danish company called Orphazyme.  A phase II/III trial is now just closing in SOD-1 patients, but the outcome is not yet published.  The SOD mutation is incredibly rare, so its taken about 6 or 7 years to recruit enough patients to do a trial.

It was quite clear that a far less challenging disease might be a slowly progressing debilitating muscle disorder called Inclusion Body Myositis (IBM). As the name suggests, formation of inclusion bodies, or aggregates, in muscle is a defining characteristic of the disease. So a number of years ago, we started collaborating here at ION with Professor Mike Hanna, who is the Director of the Institute and also the Director of the MRC Centre for Neuromuscular Diseases, who specializes in treating IBM patients.

In order to test the potential of Arimoclomol in IBM, we first had to develop a muscle model in culture […] that would mirror the key characteristics of the human disease- both the inflammatory components of that disease, as well as the degenerative and protein misfolding components.  We were able to induce muscle cells in a dish to display a very similar pathology to what you see in IBM patients’ muscle biopsies.  Once we had a good model, we then we started treating these cells in a dish with Arimoclomol, and found it could prevent the appearance of all the IBM-like pathology – including the formation of inclusions, resulting in an increase in muscle cell survival, and improvement in functional deficits that go in parallel with the formation of the inclusions, such as ER stress. So we were super keen at that point to move forward to a more clinically relevant model.

Mike Hanna and our clinical colleagues started doing all the horrific paperwork to try to set up a phase IIa safety and tolerability trial in IBM patients using Arimoclomol.  Around the same time, in the US a colleague called Paul Taylor produced an interesting mouse, which has a very complicated disease, in which one of the features is an inclusion body myopathy.  That disease is called Inclusion Body Myopathy with Pagets Disease and Frontotemporal Dementia (IBMPFTD) and is caused by mutations in VCP. Importantly for our IBM study, the muscles of these mice manifested several of the key features of IBM. So we started an efficacy trial of Arimoclomol in these mice whilst Mike was setting up the clinical trial, so he would be ready to move forward into patients if we saw any efficacy in the mice.  And fortunately we did; we saw an improvement in muscle force, and pathologically, we saw an amelioration of all the histopathology that you normally would see in those mice.

This study of arimoclomol in OBM- from cells in a dish through to mice and now the first phase of testing in patients has taken about ten years start to finish. This illustrates the effort that is required if you want to undertake a truly translational study, as it goes from cells, to mice, to patients.  In fact, it has taken three people’s PhDs, two people’s post-docs, several clinical fellows, as well as all the people running the trial to get this study finished.  Fortunately, we have just heard that it has been accepted for publication in Science Translational Medicine.

We’ve also just received funding from the FDA in the US, who are going to support an investigator-led efficacy trial in IBM, led by Mike Hanna here, and colleagues in Kansas University, USA called Rick Barohn and Mazden Dimachkie. Since this trial will be powered for efficacy, we will be able to see if it really does improve symptoms in patients; it will be great to see if our results in cell and animal models translates into benefit for patients.

Improving early diagnosis of neuromuscular disease

That sounds like a very promising potential treatment.  What do you think are the biggest challenges for finding treatments for neuromuscular diseases?

Identifying it early enough.  An early diagnosis is absolutely critical, because most people are already so sick when they come – in ALS by the time the patient first manifests with a deficit, they’ve probably lost the majority, 50-70%, of their motorneurons […] you’re really pushing the chances of actually doing anything.  You’re fighting a losing battle.

What is being done to improve the early diagnosis of these diseases? 

There are lots of people involved in imaging the brain, imaging the spinal cord tracts […] We’re heavily involved in looking for wet biomarkers – biomarkers from the cerebrospinal fluid and blood.  We think we’ve got a very good one, we’ve got a paper out on neurofilament light chain recently, and the results are very convincing.  Its not really a diagnostic biomarker, but may help to predict patient progression, whether they’re going to be fast progressors or slow progressors […] which is particularly important for stratification of patients […] for clinical trials.

We’re also involved in MRI imaging of the muscles: Mike Hanna had a paper out in Lancet Neurology, in which he very convincingly showed that MRI of muscle was effective at quantifying changes in muscles of IBM patients over a 12 moth period. IBM is a slowly progressive disease in which it is hard to quantify changes in muscle function over relatively short periods of 12 months or so, using clinical assessment of the patients. However, with imaging techniques, Mike and his colleagues were able to clearly quantify muscle loss by assessing the accumulation of muscle fat.  They could detect clear changes in those patients that were not detectable by other means.

So that’s a really important outcome which means you can use this approach in a clinical trial to quantify the effects of a given drug in a give patient. We now want to see if we can use this approach in patients with MND.

You clearly work on a lot of different approaches, the in vitro models, the mice, developing biomarkers, and clinical trials.  Do you think any one area of this research is the most crucial?

No, I think that it all needs to be done.  We started working on mouse models which were very homogeneous […]  when we went into patients we found it was much more complicated as the patients were very heterogeneous, despite having the “same” disease –  that has been quite informative.  Patients […] are all very very different; they have different mutations, different causes of disease, they have different rates of disease progression, they have different genders, and different ages when the disease appears.

Finally, last year there was a lot of controversy when Tim Hunt made some remarks about women in science.  Do you think that being a woman has impacted your career?

No, it hasn’t impacted my career.  I think its been a benefit […]  I’ve had three children, and science is really good career if you’re having children, for example it can offer flexible working hours. However, you do need to be very organized and be able to compartmentalize: this is work time and this, e.g. the weekend is not!

That’s very promising to hear, as a young female scientist.  Your lab has made some wonderful progress in this field; I imagine Eileen Watts must be very happy with everything her donation has achieved. 

Unfortunately she died before the labs really got established.  But it made a huge difference to MND research at ION, the money she decided to leave in memory of her brother, a huge difference.