More evidence to support the smouldering MS hypothesis?

Barts-MS rose-tinted-odometer: ★★★★★ (neon tennis ball green #dfff4f)

Yet another study showing that there are abnormalities in the so-called normal-appearing white matter (NAWM) that precede the development of new MS lesions. 

This supports the hypothesis that there is something in the brain tissue that triggers the development of lesions and relapses. Could this be a virus, like an isolated seed or flower in a field of wheat? Why do I say this? Firstly, when pwMS were treated with interferon-gamma, a cytokine that stimulates immune responses, they all had relapses. The interesting thing about these interferon-gamma-induced relapses is that they occurred in sites previously affected by MS. When I discussed this observation with the late Hillel Panitch, who was the principal investigator on the gamma-interferon trial, he thought that this observation was a fundamental observation and was telling us something important about MS. 

Another observation that supports the abnormal field hypothesis is the rebound post-natalizumab. This suggests that whilst you keep T and B cells out of the nervous system with natalizumab the field (brain and spinal cord) becomes more abnormal and when you let these cells back in they detect the abnormal field and run amok trying to clear the field of the offending agent. This is what happens with IRIS (immune reconstitution inflammatory syndrome) and PML. When natalizumab is washed out the immune system finds the JC virus and tries to clear it by initiating an inflammatory process. Some of us think that rebound post natalizumab is simply IRIS in response to the virus that causes MS.

Other serial MRI studies have shown subtle changes in the white matter many weeks or months before a gadolinium-enhancing lesion appears. 

These studies all suggest that the primary pathology is smouldering MS and is due to something in the nervous system that takes weeks or months to trigger a focal inflammatory lesion. The inflammation is secondary to what is causing the disease. The challenge for us all is to find out what the abnormality is that is causing these changes in the NAWM. I think the best chance we have of doing this is to study the brains of pwMS on natalizumab. To do this we will need someone with MS to die whilst on natalizumab treatment and to donate their brain to a unit with the necessary techniques to look for viruses. I think this will work because the viral load is likely to be higher in the absence of inflammation. This is why it is so important for pwMS to donate their brains for medical research.

If you are interested in more musing about the field hypothesis please read a previous post of mine from 2012 on this subject.

Well done to Emma Raducanu, whose US Open victory was a joy to watch. But best of all is her Twitter bio which contains just four words “london|toronto|shenyang|bucharest”. Another example of the pros of diversity, similar to the author list of the paper below “Colm Elliott, Parya Momayyezsiahkal, Douglas L Arnold, Dawei Liu, Jun Ke, Li Zhu, Bing Zhu, Ilena C George, Daniel P Bradley, Elizabeth Fisher, Ellen Cahir-McFarland, Peter K Stys, Jeroen J G Geurts, Nathalie Franchimont, Arie Gafson, Shibeshih Belachew”.

Elliott et al. Abnormalities in normal-appearing white matter from which multiple sclerosis lesions arise

Brain Communications, Volume 3, Issue 3, 2021, fcab176. 

Normal-appearing white matter is far from normal in multiple sclerosis; little is known about the precise pathology or spatial pattern of this alteration and its relation to subsequent lesion formation. This study was undertaken to evaluate normal-appearing white matter abnormalities in brain areas where multiple sclerosis lesions subsequently form, and to investigate the spatial distribution of normal-appearing white matter abnormalities in persons with multiple sclerosis. Brain MRIs of pre-lesion normal-appearing white matter were analysed in participants with new T2 lesions, pooled from three clinical trials: SYNERGY (NCT01864148; n = 85 with relapsing multiple sclerosis) was the test data set; ASCEND (NCT01416181; n = 154 with secondary progressive multiple sclerosis) and ADVANCE (NCT00906399; n = 261 with relapsing-remitting multiple sclerosis) were used as validation data sets. Focal normal-appearing white matter tissue state was analysed prior to lesion formation in areas where new T2 lesions later formed (pre-lesion normal-appearing white matter) using normalized magnetization transfer ratio and T2-weighted (nT2) intensities, and compared with overall normal-appearing white matter and spatially matched contralateral normal-appearing white matter. Each outcome was analysed using linear mixed-effects models. Follow-up time (as a categorical variable), patient-level characteristics (including treatment group) and other baseline variables were treated as fixed effects. In SYNERGY, nT2 intensity was significantly higher, and normalized magnetization transfer ratio was lower in pre-lesion normal-appearing white matter versus overall and contralateral normal-appearing white matter at all time points up to 24 weeks before new T2 lesion onset. In ASCEND and ADVANCE (for which normalized magnetization transfer ratio was not available), nT2 intensity in pre-lesion normal-appearing white matter was significantly higher compared to both overall and contralateral normal-appearing white matter at all pre-lesion time points extending up to 2 years prior to lesion formation. In all trials, nT2 intensity in the contralateral normal-appearing white matter was also significantly higher at all pre-lesion time points compared to overall normal-appearing white matter. Brain atlases of normal-appearing white matter abnormalities were generated using measures of voxel-wise differences in normalized magnetization transfer ratio of normal-appearing white matter in persons with multiple sclerosis compared to scanner-matched healthy controls. We observed that overall spatial distribution of normal-appearing white matter abnormalities in persons with multiple sclerosis largely recapitulated the anatomical distribution of probabilities of T2 hyperintense lesions. Overall, these findings suggest that intrinsic spatial properties and/or longstanding precursory abnormalities of normal-appearing white matter tissue may contribute to the risk of autoimmune acute demyelination in multiple sclerosis.

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General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust and are not meant to be interpreted as personal clinical advice. 

Clash of the Titans: the HILO study

Barts-MS rose-tinted-odometer: ★★★ (I am seeing blue and Spanish yellow today) 
Roche blue (#0066CC) & Novartis Spanish Yellow (#F7B516)

Yes, I really do think that intrathecal (within the meninges that cover the brain and spinal cord) or CNS resident B-cells and plasma cells are pathogenic in MS. In other words, the cytokine or chemicals B-cells and plasma cells produce, in particular their antibodies, are what is driving some of the pathologies of smouldering MS. The evidence to support this hypothesis is well rehearsed on this blog and is the reason why we are testing high-dose ocrelizumab (more CNS penetrant) vs. standard-dose ocrelizumab (less CNS penetrant) against each other in two head-2-head studies. It is also the reason we are testing cladribine’s (CLADRIPLAS and CLAD-B) and ixazomib’s (SIZOMUS) effects in intrathecal B and plasma cell markers. Yes, I really do think we need to scrub the CNS clean of B-cells, plasma cells and their products, in particular the oligoclonal IgG bands. 

I am therefore proposing a new study; the HIgh-dose versus LOw-dose anti-CD20 study or HILO Study. 

In this study, I propose testing high-dose or double-dose ocrelizumab vs. standard or intermediate-dose ocrelizumab vs. low-dose ofatumumab against each other over two years and measure their impact on end-organ damage markers (slowly expanding lesions and brain volume loss) and on CSF markers of B-cell, plasma cell and microglial activity. The latter will include free kappa and lambda immunoglobulin light chains, OCBs, soluble CD14, etc. This will answer at least from a biomarker question whether or not we need CNS penetration of anti-CD20 monoclonal antibodies to target this component of smouldering MS. The following would also answer the question of whether or not you as a person with MS would want to be treated with high-dose or low-dose anti-CD20 therapy? 

Would you want to be randomised into this study?

This study would be a clash of the titans; Roche vs. Novartis. Who would win? It really is not that important as Novartis is a major shareholder in Roche and hence when Roche makes a profit so does Novartis. The real winners will be people with MS, the data will allow them to make an informed decision about whether or not they want to go beyond NEIDA (no evident inflammatory disease activity) and be on a treatment that tackles the smouldering B-cell and plasma-cell driven processes within their brains and spinal cords. 


Conflicts of Interest

MS-Selfie Newsletter  /  MS-Selfie Microsite

Preventive Neurology

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General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust and are not meant to be interpreted as personal clinical advice. 

Smouldering MS – not all bad news

Barts-MS rose-tinted-odometer: ★★★★★ (today’s colour is Delta Red Iron Oxide #9b2f1c)

One of the smouldering MS dogmas that have entered the MS lexicon is that the iron-rimmed slowly expanding MS lesions (SELs) go on enlarging and destroying or shredding the brain tissue around it forever. Another dogma states these SELs don’t respond to current DMTs. The good news is that both of these statements are probably incorrect. 

In the recently published longitudinal MRI study below iron rims around lesions gradually diminished with time. However, having these iron rim lesions is not good news in that they are significantly more destructive than non-iron rimmed MS lesions. The question I have is what drives these lesions to form? Knowing the answer to this question will tell us what is causing MS.

The second study below demonstrates that ocrelizumab significantly reduces the expansion of slowly expanding/evolving lesions. This suggests that these lesions may be driven by intrathecal or CNS-derived immunoglobulins. This is why we are doing the high-dose ocrelizumab, SIZOMUS (ixazomib) and CHARIOT-MS (cladribine) studies to see if reducing intrathecal B and plasma cell activity has an impact on smouldering MS.

If the former studies are positive, who would want to go onto a lower-dose anti-CD20 therapy (standard-dose ocrelizumab, ofatumumab, rituximab, ublituximab)? Please note that although these lower dose anti-CD20 therapies are very effective at stopping relapses and focal MRI activity this is not MS. The real MS is smouldering MS and what we see with end-organ damage markers. This is why if I had MS I would choose a DMT that offered the best chance of normalising my brain volume loss and I would volunteer for the SIZOMUS trial. 

The good news is that these two studies below show that the so-called chronic active lesions or SELs evolve over many years after their initial formation and that they may be modifiable with DMTs. Let’s celebrate these facts. 

Iron-rimmed lesion of SEL expanding over 7 years; image from BRAIN.

Dal-Bianco et al. Long-term evolution of multiple sclerosis iron rim lesions in 7 T MRI. Brain. 2021 Apr 12;144(3):833-847.

Recent data suggest that multiple sclerosis white matter lesions surrounded by a rim of iron containing microglia, termed iron rim lesions, signify patients with more severe disease course and a propensity to develop progressive multiple sclerosis. So far, however, little is known regarding the dynamics of iron rim lesions over long-time follow-up. In a prospective longitudinal cohort study in 33 patients (17 females; 30 relapsing-remitting, three secondary progressive multiple sclerosis; median age 36.6 years (18.6-62.6), we characterized the evolution of iron rim lesions by MRI at 7 T with annual scanning. The longest follow-up was 7 years in a subgroup of eight patients. Median and mean observation periods were 1 (0-7) and 2.9 (±2.6) years, respectively. Images were acquired using a fluid-attenuated inversion recovery sequence fused with iron-sensitive MRI phase data, termed FLAIR-SWI, as well as a magnetization prepared two rapid acquisition gradient echoes, termed MP2RAGE. Volumes and T1 relaxation times of lesions with and without iron rims were assessed by manual segmentation. The pathological substrates of periplaque signal changes outside the iron rims were corroborated by targeted histological analysis on 17 post-mortem cases (10 females; two relapsing-remitting, 13 secondary progressive and two primary progressive multiple sclerosis; median age 66 years (34-88), four of them with available post-mortem 7 T MRI data. We observed 16 nascent iron rim lesions, which mainly formed in relapsing-remitting multiple sclerosis. Iron rim lesion fraction was significantly higher in relapsing-remitting than progressive disease (17.8 versus 7.2%; P < 0.001). In secondary progressive multiple sclerosis only, iron rim lesions showed significantly different volume dynamics (P < 0.034) compared with non-rim lesions, which significantly shrank with time in both relapsing-remitting (P < 0.001) and secondary progressive multiple sclerosis (P < 0.004). The iron rims themselves gradually diminished with time (P < 0.008). Compared with relapsing-remitting multiple sclerosis, iron rim lesions in secondary progressive multiple sclerosis were significantly more destructive than non-iron rim lesions (P < 0.001), reflected by prolonged lesional T1 relaxation times and by progressively increasing changes ascribed to secondary axonal degeneration in the periplaque white matter. Our study for the first time shows that chronic active lesions in multiple sclerosis patients evolve over many years after their initial formation. The dynamics of iron rim lesions thus provide one explanation for progressive brain damage and disability accrual in patients. Their systematic recording might become useful as a tool for predicting disease progression and monitoring treatment in progressive multiple sclerosis.

Ocrelizumab reduces the increase in the volume of SELs compared to placebo; image from BRAIN.

Elliott et al. Chronic white matter lesion activity predicts clinical progression in primary progressive multiple sclerosis. Brain. 2019 Sep 1;142(9):2787-2799.

Chronic active and slowly expanding lesions with smouldering inflammation are neuropathological correlates of progressive multiple sclerosis pathology. T1 hypointense volume and signal intensity on T1-weighted MRI reflect brain tissue damage that may develop within newly formed acute focal inflammatory lesions or in chronic pre-existing lesions without signs of acute inflammation. Using a recently developed method to identify slowly expanding/evolving lesions in vivo from longitudinal conventional T2- and T1-weighted brain MRI scans, we measured the relative amount of chronic lesion activity as measured by change in T1 volume and intensity within slowly expanding/evolving lesions and non-slowly expanding/evolving lesion areas of baseline pre-existing T2 lesions, and assessed the effect of ocrelizumab on this outcome in patients with primary progressive multiple sclerosis participating in the phase III, randomized, placebo-controlled, double-blind ORATORIO study (n = 732, NCT01194570). We also assessed the predictive value of T1-weighted measures of chronic lesion activity for clinical multiple sclerosis progression as reflected by a composite disability measure including the Expanded Disability Status Scale, Timed 25-Foot Walk and 9-Hole Peg Test. We observed in this clinical trial population that most of total brain non-enhancing T1 hypointense lesion volume accumulation was derived from chronic lesion activity within pre-existing T2 lesions rather than new T2 lesion formation. There was a larger decrease in mean normalized T1 signal intensity and greater relative accumulation of T1 hypointense volume in slowly expanding/evolving lesions compared with non-slowly expanding/evolving lesions. Chronic white matter lesion activity measured by longitudinal T1 hypointense lesion volume accumulation in slowly expanding/evolving lesions and in non-slowly expanding/evolving lesion areas of pre-existing lesions predicted subsequent composite disability progression with consistent trends on all components of the composite. In contrast, whole brain volume loss and acute lesion activity measured by longitudinal T1 hypointense lesion volume accumulation in new focal T2 lesions did not predict subsequent composite disability progression in this trial at the population level. Ocrelizumab reduced longitudinal measures of chronic lesion activity such as T1 hypointense lesion volume accumulation and mean normalized T1 signal intensity decrease both within regions of pre-existing T2 lesions identified as slowly expanding/evolving and in non-slowly expanding/evolving lesions. Using conventional brain MRI, T1-weighted intensity-based measures of chronic white matter lesion activity predict clinical progression in primary progressive multiple sclerosis and may qualify as a longitudinal in vivo neuroimaging correlate of smouldering demyelination and axonal loss in chronic active lesions due to CNS-resident inflammation and/or secondary neurodegeneration across the multiple sclerosis disease continuum.

Conflicts of Interest

MS-Selfie Newsletter  /  MS-Selfie Microsite

Preventive Neurology

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General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust and are not meant to be interpreted as personal clinical advice. 

It’s a fine line

Barts-MS rose-tinted-odometer: ★★ (Monday feels like an orange day; an orange cocktail day)

“I can’t wait for the next MS breakthrough; it will take 10-15 years to reach the clinic. I have smouldering MS and I need to do something about it now. Tell me Gavin what would you do if you were in my situation ?” PwMS

I have just had a call with a person with MS who I know very well. This person is not a patient of mine but he was asking me honestly what should he do about maximising his chances of doing well. He has been reading my recent blog posts and feels he needs to do something about his MS. He said he doesn’t want to have any regrets

In summary, he is middle-aged (49 years of age) and was treated with dimethyl fumarate for 6 years and was switched to ocrelizumab shortly after it was licensed. The switch was not because of breakthrough disease activity; he just thought he needed to be treated with a more effective DMT and the private neurologist who he saw recommended against having HSCT or alemtuzumab. He remains relapse and MRI disease activity free but has noticed his left leg dragging after walking long distances. His memory is not as good as it was in the past and he suffers from cognitive fatigue. He just knows he is getting worse regardless of what his EDSS and MRIs are showing. He knows he has early SPMS or smouldering disease.

What should he do? 

In the past I have always told my patients I am an academic and I can’t recommend X or Y because the evidence is just not good enough that they will make a difference. I also don’t want to be viewed as the MS expert who is recommending off-label or unproven therapies. The line between being an evidence-based practitioner and a quack is a fine line

Do I tell him to hang in there and wait for an evidence-based therapy to emerge or do I give advice about things that may make a difference? If I did give him advice would a scientific rationale be enough (preclinical data) to support my position or should my advice be based on data from preliminary trials in people with MS? Do you think it is irresponsible to give generic advice on managing smouldering MS? Finally, do any of you have advice on how you are self-managing your smouldering MS? 

Conflicts of Interest

Preventive Neurology




General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust and are not meant to be interpreted as personal clinical advice. 

Purple haze

Barts-MS rose-tinted-odometer: ★★ (Purple Haze Friday #7D7098; looking forward to the weekend)

It is quite amazing how large and extensive the focal inflammatory lesion blindspot or scotoma is in the field of MS. I was on a call with a few American neurologists last week and they were saying how anti-CD20 therapy has transformed their MS practice. One neurologist claimed that 4 out of 5 of their patients were now going onto ocrelizumab or ofatumumab. He even said that ofatumumab will become the new Copaxone; i.e. no blood monitoring and very safe. Do you agree? When I reminded this neurologist of the end-organ damage data, i.e. brain volume loss, and the progression independent of relapse data in relation to anti-CD20 therapies he dismissed me saying that these patients were free of relapses and their MRI’s were quiet so he had done his job. 

And herein lies the problem, the wider MS community including MS experts are not prepared to look beyond relapses and MRI activity; for them this is MS. In other words, if you render people relapse and MRI activity free then you have treated their MS. However, if you scratch the surface this is clearly not the case. If relapses were MS then they would predict long term outcome, but they don’t except when you are on therapy. According to the Prentice criteria that define a surrogate endpoint for relapses to be MS they need to predict outcome regardless of treatment. This is why relapses cannot be MS; relapses and their MRI equivalent (focal lesions) simply represent the immune system’s response to what is causing the disease or the real MS. 

The data set below from the MS-Base register supports this proposition; i.e. off-therapy relapses do not predict long-term outcome, unlike on-therapy relapses. This point is so fundamental to understanding the real MS that most people can’t get their heads around it. 

So what does this mean to you if you have MS? It means that if you have no evident inflammatory disease activity (NEIDA), and are relapse-free and MRI-activity free, it doesn’t mean your MS is necessarily under control. In other words, you could still be losing brain volume at double the rate of what is expected for your age and you could still be worsening. This is why we mustn’t be lulled into a sense of false security that we have cracked MS with our current therapies, in particular with the anti-CD20 therapies. We really need to go beyond NEIDA and target smouldering MS with new add-on strategies. 

I hope all this makes sense? I have asked you before, would you rather be NEIDA or NEIDA and NEO-EOD (no evident ongoing end-organ damage)? The challenge for the MS community is to shift our focus to the latter target. 

Figure from the Ann Neurol. Contribution of on- and off-therapy annualized relapse rate (ARR) to 10-year median Expanded Disability Status Scale (EDSS) changes (95% confidence interval). Here the ARR is normalized to 1. This figure shows the results of 2 adjusted quantile median regression analyses. All analyses were adjusted for gender, age at baseline, disease duration, the proportion of follow-up on first-line disease-modifying therapy (DMT), pregnancies, first DMT identity, baseline EDSS score, and clinic country. Subanalysis 1 (S1) includes all 2,466 patients from the primary analysis. Subanalysis 2 (S2) only models those patients who were able to contribute to both on-treatment and off-treatment epochs (n = 1,475). This figure demonstrates that on-treatment relapses have a profound effect on long-term EDSS increases, whereas off-treatment relapses have a marginal effect on disability outcomes.

Jokubaitis et al. Predictors of long-term disability accrual in relapse-onset multiple sclerosis. Ann Neurol. 2016 Jul;80(1):89-100. 

Objective: To identify predictors of 10-year Expanded Disability Status Scale (EDSS) change after treatment initiation in patients with relapse-onset multiple sclerosis.

Methods: Using data obtained from MSBase, we defined baseline as the date of first injectable therapy initiation. Patients need only have remained on injectable therapy for 1 day and were monitored on any approved disease-modifying therapy, or no therapy thereafter. Median EDSS score changes over a 10-year period were determined. Predictors of EDSS change were then assessed using median quantile regression analysis. Sensitivity analyses were further performed.

Results: We identified 2,466 patients followed up for at least 10 years reporting post-baseline disability scores. Patients were treated an average 83% of their follow-up time. EDSS scores increased by a median 1 point (interquartile range = 0-2) at 10 years post-baseline. Annualized relapse rate was highly predictive of increases in median EDSS over 10 years (coeff = 1.14, p = 1.9 × 10(-22) ). On-therapy relapses carried greater burden than off-therapy relapses. Cumulative treatment exposure was independently associated with lower EDSS at 10 years (coeff = -0.86, p = 1.3 × 10(-9) ). Furthermore, pregnancies were also independently associated with lower EDSS scores over the 10-year observation period (coeff = -0.36, p = 0.009).

Interpretation: We provide evidence of long-term treatment benefit in a large registry cohort, and provide evidence of long-term protective effects of pregnancy against disability accrual. We demonstrate that high annualized relapse rate, particularly on-treatment relapse, is an indicator of poor prognosis. Ann Neurol 2016;80:89-100.

Conflicts of Interest

Preventive Neurology




General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust and are not meant to be interpreted as personal clinical advice. 

Do you want to be treated with low-dose anti-CD20 therapy?

Barts-MS rose-tinted-odometer: ★★★★★ (rose-red; a climbing rose with thorns)

I have moved my treatment goal beyond NEIDA (no evident inflammatory disease activity) for my patients with MS. The new focus is on preventing end-organ damage. To achieve this we need to take off the blinkers that the Pharma industry has blinded us with. Our treatment target has to be smouldering MS, i.e. stopping disability progression, normalising brain volume loss, flattening neurofilament levels, stop slowly expanding lesions from getting bigger, clearing the CSF of oligoclonal bands and if possible promoting repair and recovery of the nervous system. 

What good is to be free of relapses and focal MRI activity if you are getting worse? This is why the concept of using low dose anti-CD20 therapy is so flawed. It is clear that study subjects exposed to lower doses of ocrelizumab in the phase 3 trials did as well as those exposed to higher doses in relation to relapses and MRI activity, but not in relation to worsening disability (see slideshow below). 

From this post-hoc analysis, it is clear that you need higher, and not lower, doses of anti-CD20 therapy at least initially as an induction strategy to purge the various B-cell compartments. We hypothesise these compartments house memory B-cells, which may be an important sanctuary for latent EBV and/or the highly autoreactive population of B-cells that drive and maintain the MS-state. This population of cells may reside in the deep tissues and/or the central nervous system. This is why we and others are testing CNS penetrant anti-B-cell strategies (ixazomib, cladribine, BTK inhibitors, etc.), i.e. we are going beyond the peripheral B-cell target. 

However, I have hypothesized that once you have purged these compartments, say after 2 years of treatment you may not need to maintain such high doses of anti-CD20 therapy that will then suppress normal B-cell biology and immune responses, which result in long term complications. This is why I have proposed using ocrelizumab as an immune reconstitution therapy, i.e. high-dose upfront followed by no treatment and wait to see if MS remains in remission or disease-activity returns requiring additional courses. The latter is what we are proposing to do in the ADIOS study. 

Even better would be two years of induction therapy with high-dose ocrelizumab followed by a maintenance therapy such as teriflunomide, leflunomide, IMU-838 (vidofludimus) or ASLAN003 (selective second-generation DHODH inhibitors), HAART (highly active antiretrovirals), famciclovir or another anti-EBV viral agent. 

The hypothesis is to allow B-cell reconstitution after anti-CD20 therapy in the presence of an antiviral agent to prevent EBV reactivation and reinfection of new memory B cells. By doing this you will also be derisking the long-term immunosuppression associated with anti-CD20 therapies and prevent the development of hypogammaglobulinemia. This strategy will also allow patients to respond to vaccines.

However, if you want lower dose anti-CD20 therapy you will be able to start Ofatumumab very soon. Please remember ofatumumab was vastly superior to teriflunomide in suppressing relapses and MRI activity (Pharma’s blinkers) but was not superior to  teriflunomide at slowing down brain volume loss in year two of the ASCLEPIOS I and II clinical trials (NCT02792218 and NCT02792231). Why? 

The following is the fundamental question you should ask yourself.

So what would you choose your MS to be treated with; (1) low-dose anti-CD20, (2) high-dose anti-CD20, (3) high-dose anti-CD20 therapy followed by a maintenance treatment or (4) an immune-reconstitution therapy (cladribine, alemtuzumab or AHSCT)?

Sadly we can’t offer all of these choices to all of our patients with MS in the current NHS treatment landscape. 

Figure from the NEJM.

Hauser et al. Ofatumumab versus Teriflunomide in Multiple Sclerosis. N Engl J Med. 2020 Aug 6;383(6):546-557. 

Background: Ofatumumab, a subcutaneous anti-CD20 monoclonal antibody, selectively depletes B cells. Teriflunomide, an oral inhibitor of pyrimidine synthesis, reduces T-cell and B-cell activation. The relative effects of these two drugs in patients with multiple sclerosis are not known.

Methods: In two double-blind, double-dummy, phase 3 trials, we randomly assigned patients with relapsing multiple sclerosis to receive subcutaneous ofatumumab (20 mg every 4 weeks after 20-mg loading doses at days 1, 7, and 14) or oral teriflunomide (14 mg daily) for up to 30 months. The primary end point was the annualized relapse rate. Secondary end points included disability worsening confirmed at 3 months or 6 months, disability improvement confirmed at 6 months, the number of gadolinium-enhancing lesions per T1-weighted magnetic resonance imaging (MRI) scan, the annualized rate of new or enlarging lesions on T2-weighted MRI, serum neurofilament light chain levels at month 3, and change in brain volume.

Results: Overall, 946 patients were assigned to receive ofatumumab and 936 to receive teriflunomide; the median follow-up was 1.6 years. The annualized relapse rates in the ofatumumab and teriflunomide groups were 0.11 and 0.22, respectively, in trial 1 (difference, -0.11; 95% confidence interval [CI], -0.16 to -0.06; P<0.001) and 0.10 and 0.25 in trial 2 (difference, -0.15; 95% CI, -0.20 to -0.09; P<0.001). In the pooled trials, the percentage of patients with disability worsening confirmed at 3 months was 10.9% with ofatumumab and 15.0% with teriflunomide (hazard ratio, 0.66; P = 0.002); the percentage with disability worsening confirmed at 6 months was 8.1% and 12.0%, respectively (hazard ratio, 0.68; P = 0.01); and the percentage with disability improvement confirmed at 6 months was 11.0% and 8.1% (hazard ratio, 1.35; P = 0.09). The number of gadolinium-enhancing lesions per T1-weighted MRI scan, the annualized rate of lesions on T2-weighted MRI, and serum neurofilament light chain levels, but not the change in brain volume, were in the same direction as the primary end point. Injection-related reactions occurred in 20.2% in the ofatumumab group and in 15.0% in the teriflunomide group (placebo injections). Serious infections occurred in 2.5% and 1.8% of the patients in the respective groups.

Conclusions: Among patients with multiple sclerosis, ofatumumab was associated with lower annualized relapse rates than teriflunomide. (Funded by Novartis; ASCLEPIOS I and II numbers, NCT02792218 and NCT02792231.).

Conflicts of Interest

Preventive Neurology




General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust.

Disrupt the Status Quo

Barts-MS rose-tinted-odometer: ★★★★★ (seeing turquoise; creative turquoise Friday)

She was 42 years of age and had had MS for 16 years. After a relapse in 2016, she was switched from interferon-beta to fingolimod. Despite being NEDA-2 ( no relapses or focal MRI activity) since starting fingolimod her disability has worsened with her EDSS going from 4.5 (walking unaided for more than 300m) to 6.0 (needing a walking stick to walk 100m). Clearly, fingolimod is doing what it should do, i.e. keeping relapse and MRI activity at bay. What can we add-on to fingolimod to stop worsening disability? 

To answer this question we need to tackle smouldering MS in a creative way; one way is to use the so-called “Simon 2-stage, single-centre, phase 2, single-arm futility trial”. The Simon design comes from oncology and allows multiple treatment regimens to be compared. The idea is to screen treatments using an initial futility study and if you pass this phase you can then stop for futility but you don’t stop if there is evidence for an overwhelming effect on the outcome. A non-futile treatment can be taken forward for further testing in a phase 2b study. 

The Simon 2-stage design provides initial evidence supporting or opposing a specific treatment, which then requires confirmation. I can see us using this trial design to test the long list of potential repurposed add-on treatments we  have to tackle smouldering MS. I see no reason why we can’t use this trial design in a factorial way to test combination therapies, i.e. to build  a MS-MDT sandwich. 

The study below uses the Simon 2-stage design to test oral domperidone, an anti-nausea drug, in SPMS. The hypothesis was that the increase in the hormone prolactin-induced as a side-effect of domperidone would stimulate remyelination, which will improve or at least slowdown disability progression. Sadly it didn’t but it shows that this route is feasible.

I wonder if we could set up a ‘disruptive Simon-stage-2 trial platform’ for pwMS to run their own trials of over-the-counter medications and/or supplements. The platform will screen patients online and assess trial eligibility using PROMs (patient-related outcomes) and then randomise them to different treatment arms. The trial platform will then follow them up via smartphones using the futility design. The primary and secondary outcomes will all be self-monitored using smartphone technology. Wouldn’t it be cool if patients with progressive MS took control of their own trials and generated the evidence to support taking some of the supplements or medication a lot of pwMS take anyway; an example could be alpha-lipoic acid. 

You may remember that Patients Like-Me did something similar with lithium in motor neuron disease a few years ago. The article by Paul Wicks ‘Patient Study Thyself’ highlighted below explains the process and is really asking people with disease to disrupt the status quo. I would urge you to go for it!  

Koch et al. Repurposing Domperidone in Secondary Progressive Multiple Sclerosis: A Simon 2-Stage Phase 2 Futility Trial. Neurology. 2021 May 4;96(18):e2313-e2322.

Objective: To assess whether treatment with the generic drug domperidone can reduce the progression of disability in secondary progressive multiple sclerosis (SPMS), we conducted a phase 2 futility trial following the Simon 2-stage design.

Methods: We enrolled patients in an open-label, Simon 2-stage, single-center, phase 2, single-arm futility trial at the Calgary Multiple Sclerosis Clinic if they met the following criteria: age of 18 to 60 years, SPMS, screening Expanded Disability Status Scale score of 4.0 to 6.5, and screening timed 25-ft walk (T25FW) of ≥9 seconds. Patients received domperidone 10 mg 4 times daily for 1 year. The primary outcome was worsening of disability, defined as worsening of the T25FW performance by ≥20% at 12 months compared to baseline. This trial is registered with (NCT02308137).

Results: Between February 13, 2015, and January 3, 2020, 110 patients were screened, 81 received treatment, and 64 completed follow-up, of whom 62 were analyzed. The study did not meet its primary endpoint: 22 of 62 (35%) patients experienced significant worsening of disability, which is close to the expected proportion of 40% and above the predefined futility threshold. Patients with higher prolactin levels during the study had a significantly lower risk of disability progression, which may warrant further investigation. Domperidone treatment was reasonably well tolerated, but adverse events occurred in 84% and serious adverse events in 15% of patients.

Conclusions: Domperidone treatment could not reject futility in reducing disability progression in SPMS. The Simon 2-stage trial model may be a useful model for phase 2 studies in progressive MS.

Trial registration information: Identifier: NCT02308137.

Classification of evidence: This study provides Class III evidence that in individuals with SPMS participating in a futility trial, domperidone treatment could not reject futility in reducing disability progression at 12 months.

Paul Wicks. Patient, study thyself. BMC Medicine volume 16, Article number: 217 (2018).

The past 15 years have seen the emergence of a new paradigm in medical research, namely of people living with medical conditions (whether patients, parents, or caregivers) using digital tools to conduct N-of-1 trials and scientifically grounded research on themselves, whilst using the Internet to form communities of like-minded individuals willing to self-experiment. Prominent examples can be found in amyotrophic lateral sclerosis/motor neurone disease (the ‘lithium study’ on PatientsLikeMe), Parkinson’s disease (‘digital patient’ Sara Riggare), and diabetes (the ‘open artificial pancreas’ of the #WeAreNotWaiting movement). Through transparency, data sharing, open source code, and publication in the peer-reviewed scientific literature, such activities conform to expected scientific conventions. However, other conventions, such as ethical oversight, regulation, professionalization, and the ability to translate this new form of relatively biased data into generalizable decisions, remain challenged. While critics worry such participant-led research merely muddies the waters of high-quality medical research and exposes patients to new harms, the potential is there to enroll millions of active minds in unravelling the wicked problems of complex medical disorders that degrade the human health span.

Conflicts of Interest

Preventive Neurology




General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust.

How soon does the shredder begin to shred?

Barts-MS rose-tinted-odometer: zero-★s

She was only 26-years and she couldn’t understand why she was falling behind her peers at work. She started working at an ultra-competitive law firm after finishing as one at the top of her peer group at Oxford. She was clearly the best-performing intern in the 2017 intake, which is why she was kept on after her internship. However, things were now going wrong. She was suffering from chronic fatigue, forgetfulness and she simply couldn’t juggle the complex tasks she was being expected to working for more than one client at a time. This job was a high-octane one and you were expected to perform at the level. Her poor performance and increasing list of mistakes had resulted in one performance review already. What should she do?

The back story to this young lawyer is her identical twin sister had been diagnosed with MS at the age of 18, shortly after completing her A-levels. Her sister had decided to delay going to university because of being diagnosed with MS. The odds are this young lawyer had asymptomatic MS and her fatigue and cognition problems are linked to smouldering MS. Do you think she should seek a neurological opinion? She is aware that her lifetime risk of being diagnosed with MS is about 30%.

Do you think she should seek a neurological opinion?

I have made the case that the real MS is not relapses and/or focal MRI activity, but smouldering MS. The real question is when do the pathological processes that drive smouldering MS begin? In this study on asymptomatic MS (radiologically-isolated syndrome or RIS) a third of them already have cognitive impairment and two-thirds had lesions with paramagnetic rims (PRL), i.e. a rim of hot microglia. These so-called PRLs are the precursor to the dreaded SELs (slowly-expanding lesions) that are so unresponsive to our current treatments and responsible for so much damage in MS. 

So what are the implications of this study for MS? 

  1. MS begins long before your first attack.
  2. Smouldering MS, formerly known as progressive MS, also begins long before your first attack.
  3. PRLs and SELs, one of the substrates for smouldering MS, are part of MS pathology from very early in the disease course; possibly the beginning.
  4. Cognitive impairment and end-organ damage begin very early in the course of MS.
  5. We need to change our diagnostic criteria to allow MS to be diagnosed very early on, in this case in the so-called asymptomatic phase of the disease. By using PRLs and the central vein sign (CVS) we are likely to improve the sensitivity and specificity of the diagnostic criteria. So what are we waiting for?

We clearly need a new treatment paradigm to tackle smouldering MS. The current anti-inflammatory monotherapy model of treating MS is unlikely to work. We need combination therapies ASAP. To achieve the latter we are going to have to get Big Pharma and the regulators to innovate quickly and intelligently. 

Oh et al. Cognitive impairment, the central vein sign, and paramagnetic rim lesions in RIS. Mult Scler. 2021 Mar 23:13524585211002097.

Objective: The central vein sign (CVS) and “paramagnetic rim lesions” (PRL) are emerging imaging biomarkers in multiple sclerosis (MS) reflecting perivenular demyelination and chronic, smoldering inflammation. The objective of this study was to assess relationships between cognitive impairment (CI) and the CVS and PRL in radiologically isolated syndrome (RIS).

Methods: Twenty-seven adults with RIS underwent 3.0 T MRI of the brain and cervical spinal cord (SC) and cognitive assessment using the minimal assessment of cognitive function in MS battery. The CVS and PRL were assessed in white-matter lesions (WMLs) on T2*-weighted segmented echo-planar magnitude and phase images. Multivariable linear regression evaluated relationships between CI and MRI measures.

Results: Global CI was present in 9 (33%) participants with processing speed and visual memory most frequently affected. Most participants (93%) had ⩾ 40% CVS + WML (a threshold distinguishing MS from other WM disorders); 63% demonstrated PRL. Linear regression revealed that CVS + WML predicted performance on verbal memory(β =-0.024, p = 0.03) while PRL predicted performance on verbal memory (β = -0.040, p = 0.04) and processing speed (β = -0.039, p = 0.03).

Conclusions: CI is common in RIS and is associated with markers of perivenular demyelination and chronic inflammation in WML, such as CVS + WML and PRL. A prospective follow-up of this cohort will ascertain the importance of CI, CVS, and PRL as risk factors for conversion from RIS to MS.

CoI: multiple

Twitter: @gavinGiovannoni                                              Medium: @gavin_24211

#Smouldering-MS: the BTK inhibitor race is on

Barts-MS rose-tinted-odometer: ★★★

Mouse Doctor studied zoology and as a result, he tends to use animal analogies to describe various phenomena. In the past, he has been known to use his favourite invertebrates to describe some neurologists or even groups of neurologists. Why invertebrates? If anyone comes up with the correct answer I will send you an MRI scanner lego set as a prize. 

Another animal he loves are lemmings, which he uses to describe the behaviour of pharmaceutical companies, i.e. they tend to follow each other by running off a cliff together. The question on everyone’s mind is how will the BTK (Bruton Tyrosine Kinase) inhibitor MS race turnout; will it be mass suicide with them failing as a class or will they usher in the next generation of innovative MS treatments? 

Our interest with BTK inhibitors started about 5 years ago when the Mouse Doctor and I almost managed to get Abbvie to fund an investigator-led study of Ibrutinib in MS. However, it was not to be as Abbvie’s partner Janssen blocked the grant. Janssen was concerned that it was too risky to test Ibrutinib in MS because of the off-target effects of Ibrutinib and its potential for serious adverse events.  I suspect they were right as Ibrutinib is a dirty drug and not a very selective BTKi as it also inhibits several other kinases.

Our hypothesis was simple; we wanted a CNS penetrant drug to target B-cells and plasma cells in the CNS of pwMS. We were buoyed by the observation that several people with CNS B-cell lymphomas were having dramatic responses to Ibrutinib. Although it was never to be we continued our search for a CNS penetrant anti-B-cell and anti-plasma cell agent and eventually, we managed to convince Takeda to fund a trial of their CNS penetrant second-generation proteasome inhibitor Ixazomib in MS. This study was meant to start earlier this year and has been unfortunately delayed by COVID-19 (we are now recruiting and are due to start very soon). 

Despite our failure to get Ibrutinib, a first-generation BTK-inhibitor, into MS Pharma has taken up the challenge and there are now four companies with BTKi programmes in MS (Merck KGaA, Sanofi-Genzyme, Roche and Biogen). 

BTKi’s will work in MS because they inhibit B-cell activation. There is phase 2 data for two of these agents confirming this (Merck and Sanofi-Genzyme). However, most people are not aware that BTKi also inhibits macrophage and microglial activation via the  Fc receptor (FcR) signalling pathway.  Therefore CNS penetrant BTK inhibitors, which applies to at least three of the four BTKi’s referred to above, will also target the so-called ‘hot’ or activated microglial response and test the hypotheses whether or not this response is favourable in MS.

The problem will be dissecting-out the anti-B-cell response from the anti-microglial response in terms of efficacy. Clearly, this will be important in view of some of the issues I raised yesterday around the ‘hot microglial’ response being potentially beneficial in the pathogenesis of MS. I envisage BTKi being very effective in stopping relapses and focal MRI activity the big question will be about the impact of BTKi on the smouldering component of MS. BTKi’s may have no effect on this component of MS, improve it or even make it worse. 

I note that many of the phase 3 studies will be testing BTKi against teriflunomide. Clearly, BTKi’s are likely to beat Teri in terms of their impact on relapses and focal MRI activity, but Pharma (or the lemmings) may be taking a chance of beating Teri in terms of its impact on the end-organ or the smouldering component of MS. Don’t forget ofatumumab and teriflunomide had the same effect on brain volume loss when they were compared head-2-head in the ASCLEPIOS I and ASCLEPIOS II studies despite ofatumumab being clearly superior to teriflunomide in suppressing relapses and focal MRI activity. 

It is clear to me that BTK is a very important treatment target in MS and the phase 3 trials will provide additional evidence beyond the B-cell on whether or not we should be targeting macrophage and microglial activation via their Fc-receptors. Whether or not this class of treatments will fail, i.e. fall of the cliff waits for the outcomes of the phase 3 trials. 

For once I going to be an optimist and give this new class of treatment a 65% chance of success, mainly due to their anti-B-cell effects, and only a 30% chance of failure, due to their microglial inhibition and yet to be identified off-target effects. What is important is that we are testing a hypothesis about the smouldering component of MS, which I consider to be the real MS and why I am so excited to be part of the story.

CoI: I sit on two BTKi phase-3 trial steering committees.

Twitter: @gavinGiovannoni                  Medium: @gavin_24211

Smouldering MS: Is 20 years a long time?

Barts-MS rose-tinted-odometer: zero stars or one ★ depending on your disposition

I prepared this post not knowing that Prof. Laura Airas has submitted a guest post in response to a request from the Mouse Doctor. Before reading this post please make sure you read her blog post first. It provides an important counterbalance to my contrarian view below. Thank you.

More than 20 years ago, when I was a junior researcher, doing my PhD,  I started a research collaboration with Dr Richard Banati, who worked in the Queen Square Brain Bank and the Imperial College PET imaging unit. Richard was investigating activated microglia in multiple sclerosis. The collaboration was very fruitful and led to the very first study of an imaging molecule called PK11195  that could label activated microglia. 

In the study (see below), we elegantly showed that people with MS (pwMS) had widespread microglial activation in their brains. Their brains, in fact, lit up like Christmas trees with so-called ‘hot’ or activated microglia. The assumption, which is now dogma, from this and other studies is that these microglia must be bad for pwMS. This has led to many research and drug discovery programmes to find treatments to switch off hot microglia.   

PK11195 labelling hot microglia. From Banati et al.

Now dial forward 20 years and finally, a follow-up study from Finland that shows that pwMS with a lit Christmas tree in their heads do worse in the longterm, i.e. pwMS with more microglial activation as determined by PK11195 staining had more disease progression that was independent of relapses. The implication is that PK11195 is a good marker of smouldering MS and if we switch off this marker we will improve long-term outcomes. 

In an email exchange with colleagues, I challenged this thinking. Is the PK11195 signal, or hot microglial response, the chicken or the egg? The microglial response may not be causal but simply associated with a worse outcome in MS. Just maybe the microglia are responding to what is causing MS and are not the primary drivers of the MS pathology. Therefore if you switch off the microglial response you may not improve MS outcomes but actually make them worse. 

I even provided some early odds of this happening. I predicted that a drug that switches off the microglial response had only about a 20% chance of improving MS outcomes. I balanced this by saying that I thought that a microglial inhibitor had about a 60% chance of actually making MS worse. I was then challenged that these odds were simply a guess; like an unskilled poker player. I disagree. Firstly, poker is a game of skill and the most skilled poker players make a relatively decent living from their skills. Secondly, there is a scientific process behind making accurate predictions (see post-script), which I try to apply. Finally, we need to apply science to the microglial prediction at hand. 

The Science: In the smouldering or slowly expanding MS lesion the hot microglia are lined up like soldiers fighting an enemy at the edge of the lesion. They remind me of a Greek phalanx.

A Military Phalanx

These microglia are not malignant cells, which makes me think they are simply doing their job. Now what if these microglia are responding to something in the surrounding tissue, for example, a slow viral infection? Switching them off may actually make the slow viral infection worse. In addition, microglia have very important function clearing up debris in the nervous system and maintaining the health of synapses and neurons in general. 

Figure 1 (from Frischer et al., Ann Neurol 2015): (A, B) Early active plaques (EAL) were defined by macrophages immunoreactive for minor myelin proteins (MOG positive macrophages right insert in A) as well as major myelin proteins (PLP positive macrophages left insert in A). (C, D) Smoldering plaques (also called slowly expanding plaques) typically showed a rather inactive centre with no or few macrophages, surrounded by a rim of activated microglia. Only few of these macrophages or microglia cells contained early myelin degradation products. Inserts depict plaque edge. (E, F) Inactive plaques revealed a sharp plaque border without or only few macrophages or activated microglia (insert). (G, H) Completely remyelinated plaques typically containing few macrophages without early myelin degradation products were classified as shadow plaques. Shadow plaques presented with a sharp plaque edge and were associated with fibrillary gliosis.

More Science: Importantly, defects in the signalling pathway of CSF-1 (colony-stimulating factor 1), which is also known as macrophage colony-stimulating factor (M-CSF), cause progressive dementia and disease of the cerebral white matter called a leukoencephalopathy. CSF-1 is a microglial stimulant. This is a warning that inhibiting microglia indiscriminately is unlikely to be good for the brain and particularly a damaged MS brain. This is why I have given greater odds to a microglial inhibitor making MS worse than making MS better. 

I am also aware that there are different types of microglia, different types of microglial responses and hence we may have to be more selective in how we target microglia in MS. Despite this, I think we as an MS community need to take a step back and challenge the current dogma that the microglial response in MS is necessarily bad. If we don’t we may be unpleasantly surprised and disappointed with the outcome of clinical trials targeting hot microglia and smouldering MS. 

P.S. If you are interested in reading about the science of prediction I would recommend ‘Superforecasting: The Art and Science of Prediction’ by Dan Gardner and Philip Tetlock; a remarkable book that provides important insights and lessons to avoid unconscious biases and it teaches you a little poker as well 😉 

Sucksdorff et al. Brain TSPO-PET predicts later disease progression independent of relapses in multiple sclerosis.  Brain, awaa275, Published: 02 October 2020.

Overactivation of microglia is associated with most neurodegenerative diseases. In this study we examined whether PET-measurable innate immune cell activation predicts multiple sclerosis disease progression. Activation of microglia/macrophages was measured using the 18-kDa translocator protein (TSPO)-binding radioligand 11C-PK11195 and PET imaging in 69 patients with multiple sclerosis and 18 age- and sex-matched healthy controls. Radioligand binding was evaluated as the distribution volume ratio from dynamic PET images. Conventional MRI and disability measurements using the Expanded Disability Status Scale were performed for patients at baseline and 4.1 ± 1.9 (mean ± standard deviation) years later. Fifty-one (74%) of the patients were free of relapses during the follow-up period. Patients had increased activation of innate immune cells in the normal-appearing white matter and in the thalamus compared to the healthy control group (P = 0.033 and P = 0.003, respectively, Wilcoxon). Forward-type stepwise logistic regression was used to assess the best variables predicting disease progression. Baseline innate immune cell activation in the normal-appearing white matter was a significant predictor of later progression when the entire multiple sclerosis cohort was assessed [odds ratio (OR) = 4.26; P = 0.048]. In the patient subgroup free of relapses there was an association between macrophage/microglia activation in the perilesional normal-appearing white matter and disease progression (OR = 4.57; P = 0.013). None of the conventional MRI parameters measured at baseline associated with later progression. Our results strongly suggest that innate immune cell activation contributes to the diffuse neural damage leading to multiple sclerosis disease progression independent of relapses.

Banati, …., Giovannoni,….et al. The peripheral benzodiazepine binding site in the brain in multiple sclerosis: quantitative in vivo imaging of microglia as a measure of disease activity. Brain 2000 Nov;123 ( Pt 11):2321-37. doi: 10.1093/brain/123.11.2321.

This study identifies by microautoradiography activated microglia/macrophages as the main cell type expressing the peripheral benzodiazepine binding site (PBBS) at sites of active CNS pathology. Quantitative measurements of PBBS expression in vivo obtained by PET and [(11)C](R)-PK11195 are shown to correspond to animal experimental and human post-mortem data on the distribution pattern of activated microglia in inflammatory brain disease. Film autoradiography with [(3)H](R)-PK11195, a specific ligand for the PBBS, showed minimal binding in normal control CNS, whereas maximal binding to mononuclear cells was found in multiple sclerosis plaques. However, there was also significantly increased [(3)H](R)-PK11195 binding on activated microglia outside the histopathologically defined borders of multiple sclerosis plaques and in areas, such as the cerebral central grey matter, that are not normally reported as sites of pathology in multiple sclerosis. A similar pattern of [(3)H](R)-PK11195 binding in areas containing activated microglia was seen in the CNS of animals with experimental allergic encephalomyelitis (EAE). In areas without identifiable focal pathology, immunocytochemical staining combined with high-resolution emulsion autoradiography demonstrated that the cellular source of [(3)H](R)-PK11195 binding is activated microglia, which frequently retains a ramified morphology. Furthermore, in vitro radioligand binding studies confirmed that microglial activation leads to a rise in the number of PBBS and not a change in binding affinity. Quantitative [(11)C](R)-PK11195 PET in multiple sclerosis patients demonstrated increased PBBS expression in areas of focal pathology identified by T(1)- and T(2)-weighted MRI and, importantly, also in normal-appearing anatomical structures, including cerebral central grey matter. The additional binding frequently delineated neuronal projection areas, such as the lateral geniculate bodies in patients with a history of optic neuritis. In summary, [(11)C](R)-PK11195 PET provides a cellular marker of disease activity in vivo in the human brain.

CoI: multiple

Twitter: @gavinGiovannoni  Medium: @gavin_24211