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.
Chemiotics II 