Friday, 28 October 2016

Needles, haystacks, and primary progressive MS: big data debunks big headlines

Our understanding of how genes influence disease is better than ever, and increasing at an incredible rate. While some diseases like Huntington’s disease are caused by mutations in a single gene, most diseases are influenced by a huge number of variants across the genome. Multiple sclerosis, diabetes, and cardiovascular disease are examples of conditions which are not caused by a single gene problem, but nonetheless are influenced by various genetic risk ‘hotspots’ (also called loci).

A recent study blew this paradigm to bits by suggesting that certain cases of MS might be attributable to mutations in a single gene. Wang et al found that a mutation in the NR1H3 gene was present in 7 people with primary progressive MS from two separate families with a significant family history of the disease. This variant was present in 1 out of a further 2053 people with MS who they studied. They concluded that this mutation might be a cause of primary progressive MS in certain people.

This finding was big news – it had massive implications for both our understanding of MS pathogenesis and for the care of people with MS. What role could this gene have? How could its dysfunction be sufficient to cause such a complex disease? Why would it only cause PPMS and not RRMS? Did this mean that these diseases were even more distinct than we thought? In terms of real-life implications, did this mean that people with lots of affected family members should be routinely offered genetic testing, and even assisted reproduction?

But while revolutionary discoveries do happen, they are rare. The big players in international MS genetics sought to replicate Wang et al’s findings in bigger cohorts to check that their incredible result was genuine. The exome aggregation consortium (ExAC) has a database of pooled genetic data from over 60,000 people. They found that the ostensibly disease-causing variant in NR1H3 detected by Wang et al was present in 21 of their healthy controls (0.031%). This frequency is very similar to the frequency of 0.049% reported by Wang et al in their cohort of people with MS. If this variant does cause MS, you would expect its frequency to be much higher in the MS cohort. The possible explanations for similar frequencies between people with MS and controls are:
-                       1. That there is no association between this variant and disease risk, or
-                       2. That there is an association between this variant and disease risk but…
o   Some people in the control group have MS, or
o   The variant has a low penetrance (i.e. it confers an increased risk of disease, but does not always cause disease), or
o   The sample sizes are too small to detect a statistically significant difference.

The International MS genetics consortium (IMSGC) has another huge database of genetic information. They looked at data from 32000 people with MS and 36500 controls. The ostensibly disease-causing variant in NR1H3 was present in 31 people in each cohort. There was no association with disease risk or with disease sub-type.

This disagreement highlights a few important issues surrounding the way MS genetics research is both done and reported. It emphasises that reporting of these kinds of discoveries should be circumspect, and should clearly distinguish between fact and hypothesis. Second, it highlights the merits and weakness of two very different approaches to discovering disease-associated gene variants: big data vs small data. Big, international consortia like ExAC and IMSGC have vast swathes of genetic data at their disposal and can work in a data-driven way to discover associations. Family-based case-control studies, on the other hand, try to work the other way up, in a hypothesis-driven way. The problem is that rare variants with a low penetrance are incredibly difficult to detect and validate using either of these approaches. Broadly speaking, small case-control studies are likely to yield false positive results, as people who are closely related will share rare genetic variants that may or may not be associated with disease risk. Using larger, international cohorts is more likely to yield false negatives, as it is impossible to have up-to-date clinical information on tens of thousands of people, and so lots of people in the apparently healthy control group may have various undiagnosed or undocumented medical problems. This makes it tricky to detect small associations between risk variants and disease.

So neither massive genome-wide association studies nor small case-control studies are perfect for elucidating the genetics of MS. In this case, the evidence seems to support a lack of association between NR1H3 mutations and MS. However, this does not mean that the Wang et al paper is dishonest in any way – it merely reflects how difficult it is to show associations between rare gene variants and disease. There is an outside chance that future studies with more multiply-affected families might put this issue to bed. For now though, I don’t think we can say that NR1H3 mutations are a monogenic cause of MS in anyone.

CoI: none
The Paper
Multiple sclerosis (MS) is an inflammatory disease characterized by myelin loss and neuronal dysfunction. Despite the aggregation observed in some families, pathogenic mutations have remained elusive. In this study, we describe the identification of NR1H3 p.Arg415Gln in seven MS patients from two multi-incident families presenting severe and progressive disease, with an average age at onset of 34 years. Additionally, association analysis of common variants in NR1H3identified rs2279238 conferring a 1.35-fold increased risk of developing progressive MS. The p.Arg415Gln position is highly conserved in orthologs and paralogs, and disrupts NR1H3 heterodimerization and transcriptional activation of target genes. Protein expression analysis revealed that mutant NR1H3 (LXRA) alters gene expression profiles, suggesting a disruption in transcriptional regulation as one of the mechanisms underlying MS pathogenesis. Our study indicates that pharmacological activation of LXRA or its targets may lead to effective treatments for the highly debilitating and currently untreatable progressive phase of MS.

Exercise can't be associated with reduced risk

Dorans KS, Massa J, Chitnis T, Ascherio A, Munger KL.Physical activity and the incidence of multiple sclerosis. Neurology. 2016 Sep 28. pii: 10.1212/WNL.0000000000003260. [Epub ahead of print]

OBJECTIVE:To study whether physical activity during adulthood or early life is associated with multiple sclerosis (MS) incidence in 2 prospective cohorts of women.
METHODS:Women in the Nurses' Health Study (NHS) (n = 81,723; 1986-2004) and NHS II (n = 111,804; 1989-2009) reported recent physical activity at baseline and in selected follow-up questionnaires. Using this information, we calculated total metabolic equivalent hours of physical activity per week, a measure of energy expenditure. There were 341 confirmed MS cases with first symptoms after baseline. Participants also reported early-life activity. To estimate relative rates (RRs) and 95% confidence intervals (CIs), we used Cox proportional hazards models, adjusting for age, latitude of residence at age 15, ethnicity, smoking, supplemental vitamin D, and body mass index at age 18.
RESULTS:Compared with women in the lowest baseline physical activity quartile, women in the highest quartile had a 27% reduced rate of MS (RRpooled = 0.73, 95% CI 0.55-0.98; p-trend 0.08); this trend was not present in 6-year lagged analyses. Change in physical activity analyses suggested that women reduced activity before onset of MS symptoms. In NHS and NHS II, higher strenuous activity at ages 18-22 years was weakly associated with a decreased MS rate. However, in NHS II, total early-life activity at ages 12-22 was not associated with MS.
CONCLUSIONS:Though higher physical activity at baseline was weakly associated with lower MS risk, this may have been due to women reducing physical activity in response to subclinical MS

Exercise is good for health, but does it affect MS?

There have been loads of posts on this and in this study just fails impress that exercise has an effect.

Thursday, 27 October 2016

#ClinicSpeak: What about PPMS?

Do you have PPMS? This post is for you. #MSBlog #ClinicSpeak

Primary progressive MS (PPMS) = relapse-onset MS = MS 

A lot of assumptions about PPMS have crept into the field and have become entrenched; we call these dogmas. We need to challenge the dogma; in particular that (1) PPMS in non-inflammatory, (2) PPMSers don't have relapses and (3) PPMS is a different disease to relapse-onset MS.

Dogma 1: PPMS in non-inflammatory - WRONG!

This pathology study done at Queen Square from the early 1990s clearly shows that PPMS is inflammatory, albeit at a slightly lower level than relapse-onset MS. The dogma has crept in because PPMSers have fewer focal lesions on MRI. This however does not mean that there is no inflammation; focal inflammation is simply occurring below the threshold of the MRI. What MRI sees in relation to focal lesions is simply the tip of the iceberg. The PPMS iceberg simply looks different with less above the surface. The positive ocrelizumab PPMS, or Oratorio, study supports PPMS as being inflammatory. 

Revesz et al. A comparison of the pathology of primary and secondary progressive multiple sclerosis. Brain. 1994 Aug;117 ( Pt 4):759-65.

Background: The dynamics of primary progressive multiple sclerosis differ from those of the more common secondary progressive form. The observation by MRI that the frequency of enhancement with gadolinium-DTPA, a marker for blood-brain barrier dysfunction, is significantly less in the primary progressive form, has led to the hypothesis that inflammation is less intense in this group. 

Aims: To test this, we have studied postmortem material from 9 cases judged from a retrospective analysis of case notes to show clear clinical evidence of either primary progressive or secondary progressive disease. 

Methods: 578 lesions were analysed. 

Results: There was significantly more inflammation in secondary progressive multiple sclerosis (as judged by the frequency of perivascular cuffing and cellularity of the parenchyma) than in primary progressive disease. 

Conclusions: These observations have implications for therapeutic strategies in progressive multiple sclerosis.

Dogma 2: PPMSers don't have relapses WRONG!

In almost all PPMS trials done to date a proportion, albeit a small proportion, of PPMSers go onto have relapses. For example in the Rituximab trial in PPMS (Olympus Trial), 11 out of 439 (2.5%) of study subjects had a relapse during the 96 weeks of the trial.

Hawker et al. Rituximab in patients with primary progressive multiple sclerosis: results of a randomized double-blind placebo-controlled multicenter trial. Ann Neurol. 2009 Oct;66(4):460-71.

Similarly, about 5% of study subjects in the glatiramer acetate PPMS, or PROMISE, trial had relapses. Unfortunately, the exact number of relapses is not reported in the main manuscript. What is reported is MRI activity; 14% of 938 study subjects had Gd-enhancing lesions on MRI during the study. The latter is the MRI equivalent of relapses. Can we say therefore make the claim that PPMS is non-relapsing? 

Wolinsky et al. Glatiramer acetate in primary progressive multiple sclerosis: results of a multinational, multicenter, double-blind, placebo-controlled trial. Ann Neurol. 2007 Jan;61(1):14-24.

Dogma 3: PPMS is a different disease to SPMS WRONG!

Did you know that it is not that uncommon in siblings pairs with MS for one to have relapse-onset disease and the other to have PPMS? The figure from the UK sibling study is in fact 23% (please see article and table below). This indicates to me that relapse onset and PPMS are the same disease.

Chataway et al. Multiple sclerosis in sibling pairs: an analysis of 250 families. J Neurol Neurosurg Psychiatry. 2001 Dec;71(6):757-61.
(33.7+27) / (84+68.3+33.7+39.3+27+9.7) x 100 = 23%

Other arguments in favour of PPMS and relapse-onset MS being the same disease relates to genetic and natural history studies. PPMSers and relapse-onset MSers have the same genetic background. Once relapse-onset MSers enter the clinical apparent phase of SPMS they progress at exactly the same rate as PPMSers.

It is for the reasons above that there is a strong argument for doing trials on combined populations of progressive MSers. In other words we should combine PPMS and SPMS populations into one study. The latter will simply be going back to chronic progressive MS classification that existed before we split MS in different subtypes. I am aware that  this is a controversial topic but it needs debate. If we don't do this then treatments will only be licensed for one subtype of progressive MS, and not the other clinical subtype, until additional trials are done. Additional trials cost money and time. Time is not a something people with progressive MS have on their side. 5-years in the life of someone with clinically-apparent progressive MSers may be the difference between using a walking-stick and being bed-ridden.

In short, pwPPMS have unfortunately missed out in the relapsing phase of the disease. They are simply unlucky that a new lesion did not occur in a clinically-eloquent site to cause a relapse and bring them to the attention of a neurologist earlier in the course of their disease. They only present when they have lost their reserve capacity. The good news is we now have a positive trial of ocrelizumab. Let's hope the regulators and payer allow pwPPMS access to ocrelizumab. 

Stop Smoking

O'Gorman CM, Broadley SA. Smoking increases the risk of progression in multiple sclerosis: A cohort study in Queensland, Australia. J Neurol Sci. 2016 ;370:219-223.

BACKGROUND:Cigarette smoking has been associated with increased risk of progressive multiple sclerosis (MS). The effect of smoking status on risk and timing of disease progression in patients with MS in Queensland, Australia has not been established.
METHODS:A clinical cohort of 646 cases (531 females, 115 males) were followed from first clinic attendance to onset of clinically determined progressive disease. Progression risk was analysed with gender, age, age of onset, exposure to disease modifying therapy, and smoking status as covariates
RESULTS: There were significantly higher risks of secondary progressive disease in males (Hazard Ratio, HR 1.83, 95% CI: 1.3-2.7) and in ever smokers (HR 1.4, 95% CI: 1.0-2.0). Progressive disease occurred approximately 4years earlier in ever smokers. Smoking did not affect age of onset of primary progressive disease.
CONCLUSIONS: Cigarette smoking was associated with earlier onset of progressive disease in this large clinical cohort. For patients with relapsing-remitting disease, smoking cessation should be encouraged.

You know this... but if you can stop the ciggies.

To stop you have to want to do it

Yes there are many people who have never smoked who have progressive MS, this suggests that you are more likely to progress if you have smoked.

Wednesday, 26 October 2016

#ClinicSpeak: what's in a name?

Why have we turned MS into two diseases instead of one? #ClinicSpeak #MSBlog

I was a meeting this weekend and presented a talk in which I discussed MS being a length-dependent axonopathy. I made the case why progressive MS is modifiable and presented the positive results of the oral low dose methotrexate and ASCEND (natalizumab) trials and said that we had thrown the baby out with the bathwater. If we had interpreted the results of the oral low-dose methotrexate progressive trial from over 20 years ago correctly we would have had licensed therapies for progressive MS decades ago. 

I was then told by one of the participants at the meeting that the parcelling up of MS into relapsing and non-relapsing forms, and of chronic progressive MS into primary and secondary progressive MS, was driven by money. When the interferon trials started it was important to make MS an orphan disease, i.e. to having fewer than 200,000 patients classified as having the disease. Being an orphan disease allowed Pharma to access the market with one pivotal trial, gave them market exclusivity and allowed them to charge much more for their drugs. The consequences of this is that we have divided MS into being many diseases, which is to the detriment of people with MS. The consequences of this are not trivial. Being diagnosed as having MS is bad enough, but then being diagnosed as having secondary progressive disease is worse. The latter is interpreted by most people that their disease is not modifiable and that they are not eligible for DMTs. This is incorrect; remember #ThinkHand. In England we are meant to stop DMTs in the SPMS phase. There are also many other reasons to avoid the diagnosis of SPMS. 

An analogy to the RRMS vs. SPMS dichotomy is being diagnosed with a low-grade tumour, that on average is quite indolent and slow growing, however, after time the tumour mutates to become highly-malignant and terminal. Just as people fear their tumour mutating, and becoming 'terminal', people with relapsing MS live in fear of developing progressive MS. 

Two diseases-in-one.

Our PROXIMUS trial, which is now over a year behind in recruitment, has been a victim of MS being two and not one disease. We made the mistake of calling it a secondary progressive trial. Very few of my colleagues have referred patients for this trial simply because it means diagnosing their patients as having early SPMS. Almost every neurologist I know avoids making a diagnosis of SPMS as long as possible because of the repercussions it has for their patients. 

I think we need to turn the clock back and get rid of arbitrary, non-science, based definitions of MS. They don't help us clinically. I recently wrote a short commentary for MSARDs arguing the MS begins long before the first clinical attack, I plan to write a piece on the observations that progressive MS is present from the start of the disease. There is simply no magic point in time when you become SPMS. Dividing MS into relapsing and progressive phases may have helped Pharma get interferons licensed under the orphan-drug act, made them lots of money, but it has done the field of MS a major disservice