Cassava Sciences — the clinical reality underneath the stock gyrations.

The stock of Cassava Sciences (symbol SAVA) has undergone some wild gyrations this year.  On 14 September it traded at 41.70, today just two weeks later it is trading in the upper 60s.

The important thing to keep in mind, is that 1 year out on treatment with SAVA’s drug Simufilam 50 patients with mild Alzheimer disease were (as a group) slightly improved.  This is absolutely unprecedented.  The best that previous therapy could accomplish was a slightly slower rate of decline — see arshttps://science.sciencemag.org/content/sci/373/6555/624.full.pdf — for a recent review of other therapy attempts.  So Cassava’s results are unprecedented.   While Alzheimer (and other dementia) patients fluctuate from day to day (like the tides from minute to minute) at the end of a year they are all worse.

These results have not been attacked, unlike their data on the effect of Simufilam on biomarkers which has been criticized by a person of standing — Elizabeth Bik — https://scienceintegritydigest.com/2021/08/27/cassava-sciences-of-stocks-and-blots/#more-2692.

But that’s irrelevant and guilt by association at best.  As a clinical neurologist, no one was ever brought to see me because of their biomarkers.

They have released part of their 1 year results — https://www.cassavasciences.com/news-releases/news-release-details/cassava-sciences-announces-top-line-results-12-month-interim.  There is a lot more that I’d like to know, but a press release is not a detailed scientific paper.

What follows is a lot of commentary and speculation about the 1 year data which we haven’t seen yet.

The results concern the first 50 patients to complete one year on the drug.  The dropout rate is stated to be under 10%.  Presumably this includes death, in a cohort (presently at around 200) with a significant mortality.  It would be interesting to know how many patients on entry made it to one year.

As a clinical neurologist I was particularly impressed with part of their data at 9 months.  Here’s a link — keep it handy — https://www.cassavasciences.com/static-files/13794384-53b3-452c-ae6c-7a09828ad389.

They measured cognitive changes by something called ADAS-Cog — a full description can be found in the following post — https://luysii.wordpress.com/2021/08/25/cassava-sciences-9-month-data-is-probably-better-than-they-realize/

ADAS-Cog score counts errors, so a perfect score would be 0, and a terrible score would be 70.  The range of deficit on entry was 16 – 26 (but possibly on something else called the MMSE) — this is what the 1 year results used.  The 9 month results used ADAS-Cog.  Perhaps they are actually the same thing — I don’t know.

On the link — https://www.cassavasciences.com/static-files/13794384-53b3-452c-ae6c-7a09828ad389 — look at the diagram titled “Individual Patient Changes in ADAS-Cog (N = 50).

There were 5 patients out of 50 at 9 months with improvements of 11 – 14, which would mean that they were pretty close to normal if their entry score was 16 and 50% improved if their score was 26.  From here out I’m just calling them ‘the 5’.

The 9 month report doesn’t discuss this, and only a clinician would know, but this is the way neurologic patients respond to treatment.  Some do extremely well while others have no effect.  Why?  It’s probably because not really understanding causation, we classify patients clinically (it’s all docs have after all).

I ran a Muscular Dystrophy Clinic for 15 years back in the day.  The Muscular Dystrophy Association was founded by parents of weak kids.  They didn’t know that some weakness was due to the muscle itself (what we’re now calling muscular dystrophy), some was due to disease affected the nerves from the spinal cord to the muscle (what we call a neuropathy now) and others were due to disease of the cells in the spinal cord giving rise to the nerves to the muscle (motor neuron disease).  That all came later.

It is quite presumptuous to say that Alzheimer’s disease is just one thing.  Perhaps the 5 patients doing so very well had it from a different (as yet unknown) cause than the other 45.  Even so such a treatment would be worth having.

So here are a few questions for the folks at Cassava about their data

l. Some 16 different sites were involved in the open label study.  Were all of ‘the 5’  from the same site (doubtful — but if true, perhaps they tested ADAS-Cog differently, casting doubt on these results).

2. What were the ADAS-Cog scores initially on ‘the 5’.

3. What happened to ‘the 5’ in the past 3 months (did they maintain improvement, slide back, or improve further?)

4. We must have lots more people passing the 3, 6, 9 month markers.  Have their results paralleled that of the first 50 reaching the mileposts?   It would be very useful to know if there are now more than 5 with improvements over 10 in ADAS-Cog at 9 months.

The slightly slowing of improvement at 1 year relative to 9 months is typical of neurologic disease.  When L-DOPA was first available in the USA in 1970, some patients because so normal that you couldn’t tell they had Parkinson’s disease, and for a few years, neurologists (myself included) thought we were actually curing the disease.  Of course we weren’t and the underlying pathology of Parkinsonism (death of neurons using dopamine) continued unabated.  The L-DOPA just helped the surviving neurons function more efficiently.  Something similar may be going on with Simufilam and Alzheimer’s.

Now for some blue sky about Simufilam. Just as the gray hair on the head of an 80 year old looks the same under the microscope as one from a prematurely gray 30 year old, the brain changes of Alzheimer’s disease (the senile plaque)  are the same regardless of the age of onset.  Assuming that the senile plaque is in someway related to dementia (despite the lack of effect of therapies trying to remove it) and given that we all accumulate a few as we age, could Simufilam improve cognition in the elderly?   Would it then be intellectual viagra and the blockbuster drug of all blockbuster drugs.

 

Cassava Sciences 9 month data is probably better than they realize

My own analysis of the Cassava Sciences 9 month data shows that it is probably even better than they realize.

Here is a link to what they released — keep it handy https://www.cassavasciences.com/static-files/13794384-53b3-452c-ae6c-7a09828ad389.

I was unable to listen to Lindsay Burn’s presentation at the Alzheimer Association International Conference in July as I wasn’t signed up.  I have been unable to find either a video or a transcript, so perhaps Lindsay did realize what I’m about to say.

Apparently today 25 August there was another bear attack on the company and its data.  I’ve not read it or even seen what the stock did.  In what follows I am assuming that everything they’ve said about their data is true and that their data is what they say it is.

So the other day I had a look at what Cassava released at the time of Lindsay’s talk.

First some background on their study.  It is a report on the first 50 patients who had received Simulfilam for 9 months.  It is very important to understand how they were measuring cognition.  It is something called ADAS-Cog11

Here it is and how it is scored and my source — https://www.verywellhealth.com/alzheimers-disease-assessment-scale-98625

The original version of the ADAS-Cog consists of 11 items, including:1

1. Word Recall Task: You are given three chances to recall as many words as possible from a list of 10 words that you were shown. This tests short-term memory.

2. Naming Objects and Fingers: Several real objects are shown to you, such as a flower, pencil and a comb, and you are asked to name them. You then have to state the name of each of the fingers on the hand, such as pinky, thumb, etc. This is similar to the Boston Naming Test in that it tests for naming ability, although the BNT uses pictures instead of real objects, to prompt a reply.

3. Following Commands: You are asked to follow a series of simple but sometimes multi-step directions, such as, “Make a fist” and “Place the pencil on top of the card.”

4. Constructional Praxis: This task involves showing you four different shapes, progressively more difficult such as overlapping rectangles, and then you will be asked to draw each one. Visuospatial abilities become impaired as dementia progresses and this task can help measure these skills.

5. Ideational Praxis: In this section, the test administrator asks you to pretend you have written a letter to yourself, fold it, place it in the envelope, seal the envelope, address it and demonstrate where to place the stamp. (While this task is still appropriate now, this could become less relevant as people write and send fewer letters through the mail.)

6. Orientation: Your orientation is measured by asking you what your first and last name are, the day of the week, date, month, year, season, time of day, and location. This will determine whether you are oriented x 1, 2, 3 or 4.

7. Word Recognition Task: In this section, you are asked to read and try to remember a list of twelve words. You are then presented with those words along with several other words and asked if each word is one that you saw earlier or not. This task is similar to the first task, with the exception that it measures your ability to recognize information, instead of recall it.

8. Remembering Test Directions: Your ability to remember directions without reminders or with a limited amount of reminders is assessed.

9. Spoken Language: The ability to use language to make yourself understood is evaluated throughout the duration of the test.

10. Comprehension: Your ability to understand the meaning of words and language over the course of the test is assessed by the test administrator.

11. Word-Finding Difficulty: Throughout the test, the test administrator assesses your word-finding ability throughout spontaneous conversation.

What the ADAS-Cog Assesses

The ADAS-Cog helps evaluate cognition and differentiates between normal cognitive functioning and impaired cognitive functioning. It is especially useful for determining the extent of cognitive decline and can help evaluate which stage of Alzheimer’s disease a person is in, based on his answers and score. The ADAS-Cog is often used in clinical trials because it can determine incremental improvements or declines in cognitive functioning.2

Scoring

The test administrator adds up points for the errors in each task of the ADAS-Cog for a total score ranging from 0 to 70. The greater the dysfunction, the greater the score. A score of 70 represents the most severe impairment and 0 represents the least impairment.

The average score of the 50 individuals entering was 17 with a standard deviation of 8, meaning that about 2/3 of the group entering had scores of 9 to 25 and that 96% had scores of 1 to 32 (but I doubt that anyone would have entered the study with a score of 1 — so I’m assuming that the lowest score on entry was 9 and the highest was 25).  Cassava Sciences has this data but I don’t know what it is.

Now follow the link to Individual Patient Changes in ADAS-Cog (N = 50) and you will see 50 dots, some red, some yellow, some green.

Look at the 5 individuals who fall between -10 and – 15 and think about what this means.  -10 means that an individual made 10 fewer errors at 9 months than on entry into the study.  Again, I have no idea what the scores of the 5 were on entry.

So assume the worst and that the 5 all had scores of 25 on entry.  The group still showed a 50% improvement from baseline as they look like they either made 12, 13, or 14 fewer errors.  If you assume that the 5 had the average impairment of 17 on entry, they were nearly normal after 9 months of treatment.  That doesn’t happen in Alzheimer’s and is a tremendous result.   Lindsay may have pointed this out in her talk, but I don’t know although I’ve tried to find out.

Is there another neurologic disease with responses like this.  Yes there is, and I’ve seen it.

I was one of the first neurologists in the USA to use L-DOPA for Parkinsonism.  All patients improved, and I actually saw one or two wheelchair bound Parkinsonians walk again (without going to Lourdes).  They were far from normal, but ever so much better.

However,  treated mildly impaired Parkinsonians became indistinguishable from normal, to the extent that I wondered if I’d misdiagnosed them.

12 to 14 fewer errors is a big deal, an average decrease of 3 errors, not so much, but still unprecedented in Alzheimer’s disease.   Whether this is clinically meaningful is hard to tell.  However, 12 month data on the 50 will be available in the fourth quarter of ’21, and if the group as a whole continues to improve over baseline it will be a very big deal as it will tell us a lot about Alzheimer’s.

Cassava Sciences has all sorts of data we’ve not seen (not that they are hiding it).  Each of the 50 has 4 data points (entry, 3, 6 and 9 months) and it would be interesting to see the actual scores rather than the changes between them in all 50.  Were the 5 patients with the 12 – 14 fewer errors more impaired (high ADAS-Cog11 score in entry) or less.

Was the marked improvement in the 5 slow and steady or sudden?   Ditto for the ones who deteriorated or who got much worse or who slightly improved.

Even if such dramatic improvement is confined to 10% of those receiving therapy it is worth a shot to give it to all.  Immune checkpoint blockade has dramatically helped some patients with cancer  (far from all), yet it is tried in many.

Disclaimer:  My wife and I have known Lindsay since she was a teenager and we were friendly with her parents.  However, everything in this post is on the basis of public information available to anyone (and of course my decades of experience as a clinical neurologist)

 

What Cassava Sciences should do now

Apparently someone important didn’t like the way Cassava Sciences analyzed their data and their stock tanked again today..  Unfortunately all of this seems to be behind a paywall, and the someone important isn’t named.  I’d love a link if any reader knows of one — just put it in as a  comment below.

I’m not important, but I thought Cassava’s results were quite impressive.  They had enough cases and enough time for the results to be statistically significant

For one thing,  Cassava dealt with severely impaired people (see below) who would be expected to show greater neuronal dropout, senile plaques and neurofibrillary tangles, than recently diagnosed patients.   Neuronal loss is not reversible in man, despite hoards of papers showing the opposite in animals.

Since everything turns on ADAS-CoG, here is a link to a complete description along with some discussion — https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5929311/

On a slide from Cassava’s presentation yesterday the ADAS-CoG average of the 50 patients on entry 9 months ago was 16.6.  With a perfect score of 70, it’s clear that these people were significantly impaired (please look at the test items to see how simple the tasks in ADAS-CoG actually are).    So an improvement of 3 points at 9 months  is significant, particularly since a drop of 5 points is expected each year — yes I’ve seen plenty of Alzheimer patients with ADAS-CoG scores of zero or close to it.

So an increase of 3 points in this group is about a16% improvement.

Here’s what Cassava should do now.  Their data should be re-examined as follows.  Split the ADAS-CoG scores into 3 groups: highest middle and lowest. Quartiles are usually used, but I don’t think 50 patients is enough to do this.  Then examine the median improvement in each of the three.  I’d use median rather than average as with small numbers in each group, a single outlier can seriously distort things — think of the survival of Stephen Hawking in a group of 12 ALS patients.

If the patients with the highest ADAS-CoG scores have the highest median improvement, there is no reason mildly impaired individuals should have a less than 16% improvement in their scores.  This means that a person with ADAS-CoG of 60 should achieve a perfect score of 70,  e.g. return to normal.

This would be incredibly useful for early Alzheimer’s disease.

There is a precedent for this.  Again it’s Parkinson’s disease.

As I mentioned in an earlier post, I was one of the first neurologists in the USA to use L-DOPA for Parkinsonism.  All patients improved, and I actually saw one or two wheelchair bound Parkinsonians walk again (without going to Lourdes).  They were far from normal, but ever so much better.

However,  treated mildly impaired Parkinsonians became indistinguishable from normal, to the extent that I wondered if I’d misdiagnosed them. These results were typical.   For a time, in the early 70s neurologists thought that we’d actually cured the disease.  It was a very heady time.  We were masters of the neurologic universe — schizophrenia was too much dopamine, Parkinsonism not enough. Bring on the next neurotransmitter, bring on the next disease.

We hadn’t cured anything of course, and the underlying loss of dopamine neurons in the substantia nigra continued.  Reality intruded for me with one such extremely normal appearing individual I’d diagnosed with Parkinsonism a few years earlier. He needed surgery, meaning that he couldn’t take anything by mouth for a while.  L-DOPA could only be given orally, and he looked quite Parkinsonian in a day or two.

If reanalysis of the existing data shows what I hope, Cassava Sciences should start another study in Alzheimer patients with ADAS-CoG scores of over 50.  If I’m right the results should be spectacular (and lead to immediate approval of the drug).

A little blue sky.  Sumafilam will then come to be known as intellectual Viagra, as all sorts of oldsters (such as yrs trly) will try to get it Alzheimer’s or no Alzheimer’s.

If you decided to buy Cassava Sciences yesterday everything went perfectly (except the price)

Yesterday I laid out the pros and cons of buying Cassava Sciences that day.  The post is reproduced below the ***

Everything I hoped for came true.  The 50 patients on Sumafilam were followed for 9 months and their ADAS-CoG score improved by 3 points.  This is unprecedented for any Alzheimer’s drug.  Historical controls show that Alzheimer patients lost 5 points a year on ADAS-CoG.  So this is a potential net gain with therapy vs. no therapyof  6 – 7 ADAS-CoG points.  Recall that a perfect ADAS-CoG score is 70.  I’ve been unable to find what the average score of 50 patients was on entry.  The paper isn’t published, but is public record results having been presented at conferences (such as today).  Recall that historical controls must be used as the study was open label (e.g. no concurrent controls).

Addendum 30 July:  Since everything turns on ADAS-CoG, here is a link to a complete description along with some discussion — https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5929311/

On a slide from Cassava’s presentation yesterday the ADAS-CoG average of the 50 patients on entry 9 months ago was 16.6.  With a perfect score of 70, it’s clear that these people were significantly impaired (please look at the test items to see how simple the tasks in ADAS-CoG actually are).    So an improvement of 3 points at 9 months is significant, particularly since a drop of 5 points is expected each year — yes I’ve seen plenty of Alzheimer patients with ADAS-CoG scores of zero or close to it. 

However using historical controls is a no no particularly in neurology and cardiology.

Why?

From an old post “MDs gradually woke up to the fallacy of using historical rather than concurrent controls particularly in studies of therapies to prevent heart attack and stroke, as the rates of both dropped significantly in the past 50 years, and survival from individual heart attacks and strokes also improved.”

 

However, I think using ADAS-CoG is OK in Alzheimer’s as we’re  talking about a disorder with no useful therapy.

 

I’m pleased that I saw the possibility of continued improvement in cognition in yesterday’s post.

 

So all my hopes for the drug came true, yet the stock tanked, closing at 103 down 32 points (down 24%) !

 

Why?  Well, in the past few months, all companies with drugs for Alzheimer’s disease have been fluctuating in price together, and one of them (to remain nameless to protect the innocent) had the temerity to release a 25 day study today on their drug based on 14 patients.  The stock was down 60%.

 

So Cassava got tarred with this brush.

 

Another likely reason is that the rise in Cassava was fueled by very small investors.  If you watched the transactions on a day SAVA was soaring, the purchases were rarely over 200.  So many of them were likely buying because others were.  So they sold when others were.  Lemmings anyone?

 

Nonetheless, SAVA’s data is much better than Biogen’s awful (and expensive) Aduhelm, so that Sumafilam is almost certain to be approved (1) if the data continue to be good (2) if a controlled trial controlled underway produces the same result.

 

So I think, in the long run, that the stock has a bright future, but as John Keynes said “In the long run we are all dead”

 

*** Yesterday’s post

 

Should you buy Cassava Sciences today?

Tomorrow Cassava Sciences will announce the interim results of an open label trial of its Alzheimer drug Sumafilam in 50 patients receiving the drug for 9 months. Should you buy the stock today?

The stock (symbol SAVA) has had a huge run this year starting at 7 and closing yesterday 27 July ’21 at 127.50.

I’ve been interested in the stock for several reasons

l. As a neurologist, I’ve watched patients, family members and friends deteriorate and die, being totally unable to help them.

2. I’ve known one of the principals in the company since she was a teenager in Montana — Lindsay Burns https://luysii.wordpress.com/2021/02/02/montana-girl-does-good-real-good/

3. Sumafilam is thought to work by a completely different mechanism of action than previous approaches (all of which have failed to produce a useful drug)– https://luysii.wordpress.com/2021/03/25/the-science-behind-cassava-sciences-sava/

In fact some of these therapies have actually made Alzheimer’s worse [ Nature Reviews Drug Discovery vol. 18 p. 327 ’19 ]

Tomorrow’s results should move the stock significantly.  If there is no improvement in cognition the stock will plummet.  If there is improvement the stock should soar, at least double again.  Why? Because we have no useful therapy.  Forget Biogen’s drug Aduhelm — the FDA advisory committee resigned in protest after the drug was approved, as the evidence for help was minimal at best.

Of course I’m rooting for the drug as a clinician and as a friend of Lindsay.

There is some evidence that the results tomorrow will show that the drug helps

 https://finance.yahoo.com/news/cassava-sciences-seat-top-charts-142318201.html

“A prior analysis after six months showed patients taking Cassava’s medication had a 10% improvement on cognition and 29% improvement on an inventory of dementia-related behavior, like delusions and anxiety.

 

The author of the article didn’t realize just how unprecedented these results are.  The numbers of patients (50) and the time (6 months) are long enough to make statistical fluke unlikely.

 

It is even possible that the patients will continue to improve — from the 6 month results, in which case the stock will go bananas.

 

Here’s why.

This isn’t in the books, but there is a precedent for continued improvement on Sumafilam based on my clinical experience with Parkinson’s disease.

 

I was one of the first docs able to prescribe L-DOPA for Parkinsonism in 9/70.  L-DOPA was released in the USA that month, after unconsciounable delay by the FDA.  I’d just left the Air Force and was starting to finish up my neurology residency at the University of Colorado.  The chief (James Austin) called me in and tasked me with setting up the brand new L-DOPA clinic.

 

 

We didn’t know what the drug would do, so we proceeded very cautiously.  Giving a little, watching, waiting, giving a little more, watching, waiting.  Wash rinse repeat.  The results were dramatic, as (like current therapy for Alzheimer’s disease), previous therapy was lousy. 

 

What became apparent to me, was that patients continued to improve ON THE SAME DOSE.   One of the mistakes GPs would make in subsequent years was increasing the dose quickly, since improvement was continuing (on the theory that if a little is good more would be better).  This pushed patients into toxicity (reversible fortunately). 

 

Something similar happens with all the antidepressants we have (except the ketamine derivatives).  You almost never see improvement in the first week or two. 

 

Do I know what tomorrow’s results will be?  Do I have inside information?  No.  Both my wife’s parents had decades long careers at the Securities and Exchange Commission (SEC), and I well know how they regard trading on inside information.

 

So these thoughts are just educated guesses.  If you are trying to decide whether or not to buy the stock, I hope they will be helpful to you.  Full disclosure: I do have a small position in the stock and am anxiously awaiting tomorrow’s results.

Should you buy Cassava Sciences today?

Tomorrow Cassava Sciences will announce the interim results of an open label trial of its Alzheimer drug Sumafilam in 50 patients receiving the drug for 9 months. Should you buy the stock today?

The stock (symbol SAVA) has had a huge run this year starting at 7 and closing yesterday 27 July ’21 at 127.50.

I’ve been interested in the stock for several reasons

l. As a neurologist, I’ve watched patients, family members and friends deteriorate and die, being totally unable to help them.

2. I’ve known one of the principals in the company since she was a teenager in Montana — Lindsay Burns https://luysii.wordpress.com/2021/02/02/montana-girl-does-good-real-good/

3. Sumafilam is thought to work by a completely different mechanism of action than previous approaches (all of which have failed to produce a useful drug)– https://luysii.wordpress.com/2021/03/25/the-science-behind-cassava-sciences-sava/

In fact some of these therapies have actually made Alzheimer’s worse [ Nature Reviews Drug Discovery vol. 18 p. 327 ’19 ]

Tomorrow’s results should move the stock significantly.  If there is no improvement in cognition the stock will plummet.  If there is improvement the stock should soar, at least double again.  Why? Because we have no useful therapy.  Forget Biogen’s drug Aduhelm — the FDA advisory committee resigned in protest after the drug was approved, as the evidence for help was minimal at best.

Of course I’m rooting for the drug as a clinician and as a friend of Lindsay.

There is some evidence that the results tomorrow will show that the drug helps

 https://finance.yahoo.com/news/cassava-sciences-seat-top-charts-142318201.html

“A prior analysis after six months showed patients taking Cassava’s medication had a 10% improvement on cognition and 29% improvement on an inventory of dementia-related behavior, like delusions and anxiety.

 

The author of the article didn’t realize just how unprecedented these results are.  The numbers of patients (50) and the time (6 months) are long enough to make statistical fluke unlikely.

 

It is even possible that the patients will continue to improve — from the 6 month results, in which case the stock will go bananas.

 

Here’s why.

This isn’t in the books, but there is a precedent for continued improvement on Sumafilam based on my clinical experience with Parkinson’s disease.

 

I was one of the first docs able to prescribe L-DOPA for Parkinsonism in 9/70.  L-DOPA was released in the USA that month, after unconsciounable delay by the FDA.  I’d just left the Air Force and was starting to finish up my neurology residency at the University of Colorado.  The chief (James Austin) called me in and tasked me with setting up the brand new L-DOPA clinic.

 

 

We didn’t know what the drug would do, so we proceeded very cautiously.  Giving a little, watching, waiting, giving a little more, watching, waiting.  Wash rinse repeat.  The results were dramatic, as (like current therapy for Alzheimer’s disease), previous therapy was lousy. 

 

What became apparent to me, was that patients continued to improve ON THE SAME DOSE.   One of the mistakes GPs would make in subsequent years was increasing the dose quickly, since improvement was continuing (on the theory that if a little is good more would be better).  This pushed patients into toxicity (reversible fortunately). 

 

Something similar happens with all the antidepressants we have (except the ketamine derivatives).  You almost never see improvement in the first week or two. 

 

Do I know what tomorrow’s results will be?  Do I have inside information?  No.  Both my wife’s parents had decades long careers at the Securities and Exchange Commission (SEC), and I well know how they regard trading on inside information.

 

So these thoughts are just educated guesses.  If you are trying to decide whether or not to buy the stock, I hope they will be helpful to you.  Full disclosure: I do have a small position in the stock and am anxiously awaiting tomorrow’s results.

A possible new way to attack Parkinson’s disease

Alpha-synuclein is the main component of the Lewy body of Parkinson’s disease.  It contains 140 amino acids, and is ‘natively unfolded’ in that it has no apparent ordered secondary structure (alpha helices, beta pleated sheets) detectable by a variety of methods — far ultraviolet circular dichroism, Fourier transform infrared spectroscopy or NMR spectroscopy. When the protein binds to artificial membranes half of it forms alpha helices.   Amazingly, after a huge amount of work we don’t know what alpha-Synuclein actually does.  Knockouts have only minor CNS abnormalities.

However, alpha synuclein forms fibrils which bind to cell surface receptors with internalization and transmission to other cells, just like prions.   Two such receptors for alpha-synuclein fibrils are Lymphocyte Activation Gene E (LAG3) and Amyloid PrecursorLike Protein 1 (ALPL1).

LAG3 has 4 immunoglobulin like domains (D1 – D4).  It uses D1 to capture the carboxy terminus which is exposed and concentrated on the surface of the alpha-synuclein fibrils.

Interestingly the monomers are said to adopt a self-shielded conformation which impedes the exposure of the carboxy terminus.  Phosphorylation of serine #129 enhances the binding of alpha-synuclein preformed fibrils to LAG3 and APLP1.  So the carboxy terminus of alpha-synuclein is a promising traget to block Parkinson’s disease progression.

To understand anything in the cell you need to understand nearly everything in the cell

Understanding how variants in one protein can either increase or decrease the risk of Parkinson’s disease requires understanding of the following: the lysosome, TMEM175, Protein kinase B, protein moonlighting, ion channel lysoK_GF, dopamine neurons among other things. So get ready for a deep dive into molecular and cellular biology.

It is now 50 years and 6 months since L-DOPA was released in the USA for Parkinson’s disease, and I was tasked as a resident by the chief with running the first L-DOPA clinic at the University of Colorado.  We are still learning about the disease as the following paper Nature vol. 591 pp. 431 – 437 ’21 will show. 

The paper describes an potassium conducting ion channel in the lysosomal membrane called LysoK_GF.  The channel is made from two proteins TMEM175 and protein kinase B (also known as AKT).

TMEM175 is an ion channel conducting potassium.  It is unlike any of the 80 or so known potassium channels.  It  contains two repeats of 6 transmembrane helices (rather than 4) and no pore loop containing the GYG potassium channel signature sequence. Lysosomes lacking it aren’t as acidic as they should be (enzymes inside the lysosome work best at acid pH).  Why loss of a potassium channel show affect lysosomal pH is a mystery (to me at least).

Genome Wide Association Studies (GWAS) have pointed to the genomic region containing TMEM175 as having risk factors for Parkinsonism.  Some variants in TMEM175 are associated with increased risk of the disease and others are associated with decreased risk — something fascinating as knowledge here should certainly tell us something about Parkinsonism.  

The other protein making up LysoK_GF is protein kinase B (also known as AKT). It is found inside the cell, sometimes associated with membranes, sometimes free in the cytoplasm. It is big containing 481 amino acids. Control of its activity is important, and Cell vol. 169 pp. 381 – 405 ’17 lists 21 separate amino acids which can be modified by such things as acetylation, phosphorylation, sumoylation, Nacetyl glucosamine, proline hydroxylation.  Well 2^21 is 2,097,152, so this should keep cell biologists busy for some time. Not only that some 100 different proteins AKT phosphorylates were known as 2017.  

TMEM175 is opened by conformational changes in AKT.  Normally the enzyme is inactive because the pleckstrin homology domain binds to the catalytic domain inhibiting enzyme activity as the substrate can’t get in.

Remarkably you can make a catalytically dead AKT, and it still works as a controller of TMEM175 activity — this is an example of a moonlighting molecule — for more please see — https://luysii.wordpress.com/2021/01/11/moonlighting-molecules/.

Normally the activity and conformation of AKT is controlled by the metabolic state of the cell (with 21 different molecular knob sites on the protein this shouldn’t be hard).  So the fact that AKT conformation controls TMEM175 conductivity which controls lysosome activity gives the metabolic state of the cell a way to control lysosomal function.  

Notice how to understand anything in the cell you must ask ‘what’s it for’, thinking that is inherently teleological. 

Now on to the two risk factors for Parkinsonism in TMEM175.  The methionine –> threonine mutation at amino acid #393 reduces the lysoK_GF current and is associated with an increased risk of parkinsonism, while the glutamine –> proline mutation at amino acid position #65 gives a channel which remains functional under conditions of nutrient starvation. 

The authors cultured dopamine neurons and found out that the full blooded channel LysoK_GF (TMEM175 + AKT) protected neurons against a variety of insults (MPTP — a known dopamine neuron toxin, hydrogen peroxide, nutrient starvation). 

TMEM175 knockout neurons accumulate more alpha-synuclein — the main constituent of the Lewy body of Parkinsonism.

So it’s all one glorious tangle, but it isn’t just molecular biological navel gazing, because it is getting close to one cause (and hopefully a treatment) of Parkinson’s disease.  

Why don’t serotonin neurons die like dopamine neurons do in Parkinson’s disease

Say what ?  “This proportion will likely be higher in rat dopaminergic neurons, which have even larger axonal arbors with ~500,000 presynapses, or in human serotonergic neurons, which are estimated to extend axons for 350 meters” – from [ Science vol. 366 3aaw9997 p. 4 ’19 ]

I thought I was reasonably well informed but I found these numbers astounding, so I looked up the papers.  Here is how such statement can be made with chapter and verse.

“The validity of the single-cell axon length measurements for dopaminergic and cholinergic neurons can be independently checked with calculations based on the total volume of the target territory, the density of the particular type of axon (axon length per volume of target territory), and the number of neuronal cell bodies giving rise to that type of axonThese population analyses are made possible by the availability of antibodies that localize to different types of axons: anti-ChAT for cholinergic axons (also visualized with acetylcholine esterase histochemistry), anti-tyrosine hydroxylase for striatal dopaminergic axons, and anti-serotonin for serotonergic axons.

The human data for axon density and neuron counts have been published for forebrain cholinergic neurons and for serotonergic neurons projecting from the dorsal raphe nucleus to the cortex, and cortical volume estimates for humans are available from MRI analyses; forebrain cholinergic neuron data is also available for chimpanzees. These calculations lead to axon length estimates of 107 m and 31 m, respectively, for human and chimpanzee forebrain cholinergic neurons, and an axon length estimate of 170–348 meters for human serotonergic neurons.”

H. Wu, J. Williams, J. Nathans, Complete morphologies of basal forebrain cholinergic neurons in the mouse. eLife 3, e02444 (2014). doi: 10.7554/eLife.02444; pmid: 24894464

How in the world can these neurons survive as long as they do?

Not all of them do–  At birth there are 450,000 neurons in the substantia nigra (one side or both sides?), declining to 275 by age 60.  Patients with Parkinsonism all had cell counts below 140,000 [  Ann. Neurol. vol. 24 pp. 574 – 576 ’88 ]. Catecholamines such as dopamine and norepinephrine are easily oxidized to quinones, and this may be the ‘black stuff’ in the substantia nigra (which is latin for black stuff).

Here are the numbers for serotonin neurons in the few brain nuclei (dorsal raphe nucleus) in which they are found.  Less than dopamine.  A mere 165,000 +/- 34,000 — https://www.ncbi.nlm.nih.gov › pubmed

So being too small to be seen with a total axon length of a football field, they appear to last as long as we do.  Have we missed a neurological disease due to loss of serotonin neurons?

Why should the axons of dopamine, serotonin and norepinephrine neurons be so long and branch so widely?  Because they release their transmitters diffusely in the brain, and diffusion is too slow, so the axonal apparatus must get it there and release it locally into the brain’s extracellular space, no postsynaptic specializations are present in volume neurotransmission — that’s the point.  This is one of the reasons that a wiring diagram of the brain isn’t enough — https://luysii.wordpress.com/2011/04/10/would-a-wiring-diagram-of-the-brain-help-you-understand-it/.

Just think of that dopamine neuron with 500,000 presynapses.  Synthesis and release must be general, as the neuron couldn’t possibly address an individual synapse.

The more we know the more remarkable the brain becomes.

 

Progress has been slow but not for want of trying

Progress in the sense of therapy for Alzheimer’s disease and Glioblastoma multiforme is essentially nonexistent, and we could use better therapy for Parkinsonism. This doesn’t mean that researchers have given up. Far from it. Three papers all in last week’s issue of PNAS came up with new understanding and possibly new therapeutic approaches for all three.

You’ll need some serious molecular biological and cell physiological chops to get through the following.

l. Glioblastoma multiforme — they aren’t living much longer than they were when I started pracice 45 years ago (about 2 years — although of course there are exceptions).

The human ZBTB family of genes consists of 49 members coding for transcription factors. BCL6 is also known as ZBTB27 and is a master regulator of lymph node germinal responses. To execute its transcriptional activity, BCL6 requires homodimerization and formation of a complex with a variety of cofactors including BCL6 corerpressor (BCoR), nuclear receptor corepressor 1 (NCoR) and Silencing Mediator of Retinoic acid and Thyroid hormone receptor (SMRT). BCL6 inhibitors block the interaction between BCL6 and its friends, selectively killing BCL6 addicted cancer cells.

The present paper [ Proc. Natl. Acad. Sci. vol. 114 pp. 3981 – 3986 ’17 ] shows that BCL6 is required for glioblastoma cell viability. One transcriptional target of BCL6 is AXL, a tyrosine kinase. Depletion of AXL also decreases proliferation of glioblastoma cells in vitro and in vivo (in a mouse model of course).

So here are two new lines of attack on a very bad disease.

2. Alzheimer’s disease — the best we can do is slow it down, certainly not improve mental function and not keep mental function from getting worse. ErbB2 is a member of the Epidermal Growth Factor Receptor (EGFR) family. It is tightly associated with neuritic plaques in Alzheimer’s. Ras GTPase activation mediates EGF induced stimulation of gamma secretase to increase the nuclear function of the amyloid precursor protein (APP) intracellular domain (AICD). ErbB2 suppresses the autophagic destruction of AICD, physically dissociating Beclin1 vrom the VPS34/VPS15 complex independently of its kinase activity.

So the following paper [ Proc. Natl. Acad. Sci. vol. 114 pp. E3129 – E3138 ’17 ] Used a compound downregulating ErbB2 function (CL-387,785) in mouse models of Alzheimer’s (which have notoriously NOT led to useful therapy). Levels of AICD declined along with beta amyloid, and the animals appeared smarter (but how smart can a mouse be?).

3.Parkinson’s disease — here we really thought we had a cure back in 1972 when L-DOPA was first released for use in the USA. Some patients looked so good that it was impossible to tell if they had the disease. Unfortunately, the basic problem (death of dopaminergic neurons) continued despite L-DOPA pills supplying what they no longer could.

Nurr1 is a protein which causes the development of dopamine neurons in the embryo. Expression of Nurr1 continues throughout life. Nurr1 appears to be a constitutively active nuclear hormone receptor. Why? Because the place where ligands (such as thyroid hormone, steroid hormones) bind to the protein is closed. A few mutations in the Nurr1 gene have been associated with familial parkinsonism.

Nurr1 functions by forming a heterodimer with the Retinoid X Receptor alpha (RXRalpha), another nuclear hormone receptor, but one which does have an open binding pocket. A compound called BRF110 was shown by the following paper [ Proc. Natl. Acad. Sci. vol. 114 pp. 3795 – 3797, 3999 – 4004 ’17 ] to bind to the ligand pocked of RXRalpha increasing its activity. The net effect is to enhance expression of dopamine neuron specific genes.

More to the point MPP+ is a toxin pretty selective for dopamine neurons (it kills them). BRF110 helps survival against MPP+ (but only if given before toxin administration). This wouldn’t be so bad because something is causing dopamine neurons to die (perhaps its a toxin), so BRF110 may fight the decline in dopamine neuron numbers, rather than treating the symptoms of dopamine deficiency.

So there you have it 3 possible new approaches to therapy for 3 bad disease all in one weeks issue of PNAS. Not easy reading, perhaps, but this is where therapy is going to come from (hopefully soon).

Hillary’s health — you can see a lot by looking

Last night’s debates should put two suggestions about Hillary’s health to rest and gives some evidence for two others. First, she does not have Parkinson’s disease. Second, she does not have epilepsy. Third, her eye movements still show some residua from the stroke of December 2012. Fourth, she may have a mild proximal myopathy.

Now to elaborate.

Parkinson’s disease: Two great things happened in September 1970 — I finished my two years in the Air Force and L – DOPA was released for use in the USA. American neurologists had been reading about the great things it was doing for the disease in Europe for almost 10 years. So when I went back to complete the last two years of my residency, the chief put me in charge of the L – DOPA clinic he’d just set up. So until retirement in 2000, I treated lots of people with it.

As the chief said — Parkinson’s disease is a Yellow Cab disease. If you see a Yellow Cab on the street, you don’t write down the license number, go down to city hall and find that it was registered as a Yellow Cab. You look at it and say “that’s a Yellow Cab”.

Parkinsonians have a rather immobile face (masklike) — Hillary’s face is quite mobile. Their speech lacks the normal musicality of speech (prosody), Hillary’s speech has normal inflection. Parkinsonians have a slow, stiff gait with difficulty initiating it. Hillary has none of this. Finally there is no sign of any tremor.

Epilepsy: Videos of purported seizures are out and about on the internet, particularly one during an interview. I thought that the ones I saw looked rather edited, as though some individual frames had been deleted from the videos. Fortunately last night we had an opportunity to see for ourselves. Toward the end of the debate, she had another episode, during which she shook her head and her shoulders for a few seconds. This happened in real time, so we could run the video recording backwards and forwards. At no time did she appear to be out of contact, and she then continued on with what she was saying without pause. So it’s just something she voluntarily does. It isn’t epilepsy.

Eye movements: Recall that after the stroke in December 2012, Hillary had double vision and had to wear Fresnel lenses to correct it for a few weeks afterwards — pictures of her testifying in congress January 2013 show this. So last night there was a 90 minute opportunity to watch the way her eyes move. They aren’t quite normal – on looking to her left the right eye lags and doesn’t bury the white. Even though Trump was to her right, she turned her head rather than her eyes to look at him, so I only saw her look to her right on a few occasions, but when she did her eyes appeared to move together. No other residua of a brainstem stroke were present such as slurred speech (dysarthria), facial weakness, facial asymmetry.

Proximal muscle weakness: The internist referred to in a previous post noted the following:

“There were shots a month or so ago of her needing help to get up outdoor stairs and also needing a small step-stool to get up into a Secret Service Suburban. My wife and I hop in and out of a Yukon and do not need any step device (they are of comparable age). After a photo of her doing that was published, she started getting in and out of vehicles on the side away from cameras and was also switched to a taller van with a step mounted on the vehicle. In February, press was forbidden by her staff from filming her climbing the stairs to board her private jet.”

He wondered if she could have something like limb girdle dystrophy.

Well, such a dystrophy is certainly possible. Although Hillary  had no difficulty standing for 90 minutes, at the end, she appeared to waddle as she walked toward the moderator.. There wasn’t really enough time to definitely say that she waddled.  It’s worth carefully watching the way she walks in the future.

Why is waddling a sign of mild weakness of the muscles of the pelvic girdle? Believe it or not the buttocks are not a secondary sexual characteristic. The main buttock muscle (gluteus maximus) is so big because it has so much work to do.

Think about what you do when you take a step forward with your right foot. To remain stable, your entire upper body weight must  be strongly plastered to your left hip. You need a strong, large muscle to do this (the gluteus maximus). What happens if the muscle is weak? Your upper body would fall to the right. How would you prevent this? By throwing your upper body to the left, putting its center of gravity there, so it presses on the left hip with greater force. A similar thing happens when stepping forward with the left foot. The net effect is that you waddle, which is what Hillary appeared to do.

It’s worth watching her walk in the future.

Stamina: she was under 90 minutes of stress, and showed no sign of fatigue.

Now, hopefully, back to the science, with a very long (over 1,000 Angstroms) allosteric effect.