Is PSP the route to not just Alzheimer’s but also Parkinson’s?

We’ve known for many years that Parkinson’s disease, which the textbooks call an α-synucleinopathy, has some aggregated tau as well. It appears that each of the two proteins, once misfolded, not only induces its own normal brethren to misfold, it also induces copies of the other to misfold.
The first demonstration of this synergistic misfolding and resulting aggregation came in a series of three papers between 2002 and 2004 from the lab of John Trojanowski and Virginia Lee at Penn. The first authors were John Duda, Bernard Giasson and Paul Kotzbauer. (Disclaimer: I was one of their co-authors on all three.)

Now, Julia Gerson, a grad student in the lab of Rakez Kayed at the University of Texas Galveston, has presented work at the Society for Neuroscience that harnesses that finding of a PD/tauopathy overlap for therapeutic purposes. (Another disclaimer: Kayed has a related grant from CurePSP, where I chair the grant review.)

Gerson and friends created antibodies directed at oligomeric tau, which is tau in small aggregates of maybe 20 or 30 molecules, which are still small enough to remain in solution in the cytoplasm and therefore invisible to light microscopy, unlike mature neurofibrillary tangles. They didn’t want to target normal, non-aggregated tau for fear of disrupting the normal function of that protein, which is to stabilize microtubules.

They injected those anti-tau antibodies into mice that had a copy of a variant of the human gene encoding α-synuclein. The variation was an G209A mutation, producing an A53T alteration in the resulting protein. This is the mutation that my colleagues and I found in 1997 as the cause of PD in a large Italian-American family with autosomal-dominant PD, a finding that first linked PD with α-synuclein. (That’s Disclaimer #3. You’re starting to see why I’m so interested in this new finding.)

The antibody protected the mice against the loss of dopaminergic neurons that the α-synuclein mutation caused in the untreated mutant mice. Mice that received antibody against normal tau did even more poorly than the controls.

So here’s the take-home: Developing an anti-tau antibody for treatment of PSP may also help Parkinson’s. We already expect that it may help Alzheimer’s because that’s clearly a tau disorder. But now, the synergistic toxicity of tau and α-synuclein could also allow a single anti-tau antibody to protect against both Parkinson’s and dementia with Lewy bodies (which also has aggregation of both proteins).

If I were the drug companies, I’d be sitting up and taking notice. Two companies, Bristol-Myers Squibb and AbbVie (licensing an antibody from C2N) have already started anti-tau antibody trials in people with PSP. Others have anti-tau programs in progress.

This new report, which may extend the utility of those products to Parkinson’s, should give that snowball an extra push.

Road test for a Roadmap

This is a request for your suggestions to improve/amend CurePSP’s research plan, which is now two years old.

Here’s a link to the first and current version of our Research Roadmap:  Roadmap for Symposium 2013. You can also find it here.

It was designed as a guide to grant applicants and donors who want to know what CurePSP is interested in funding.  That’s not to say that we wouldn’t fund other things, but proposals that fit into the Roadmap’s model are viewed more favorably in our grant review process.

The elevator explanation of the model is that it uses unbiased gene searches to identify new risk genes, then finds drug targets among the proteins in the related gene products or cellular pathways, then tests those drugs in lab models, then turns to Pharma to develop those drugs clinically.  Along the way, it calls for new models and new clinical markers to assist in the process.

Clearly, The Roadmap ignores important things such as symptomatic treatments, toxic etiologies, clinical characterization, epidemiology and neurophysiologic analysis, not to mention serendipitous neuroprotective treatments with unclear mechanism.  But it provides a focus and an orientation.

So please use the Comments function to leave me your suggestions for improvement.  Keep in mind that the Roadmap should remain relatively simple and generic.  We don’t want to direct research from the top down.  On the other hand, we don’t want the document to be so generic as to be useless.

Obviously, feel free to respond to others’ comments; and have fun!

 

Just a residue full of sugar . . .

I’ve been jolted out of my non-posting torpor by CurePSP’s annual International Research Symposium, held on November 6 in La Jolla. The lecture hall was smack dab on the beach and despite the quality of the presentations, it was easy for the eye to wander from the lectern to the doorway framing a view of swaying palms and the blue Pacific. Thanks to Jeff Friedman for arranging the venue. Anyway, I’ll be describing some of the goings-on in this post and the next few.
Two of the presentations, both from pharma scientists, described drugs in development for PSP that reduce tau aggregation by inhibiting OGA (O-GlcNAcase; pronounced “oh-GLY-na-kaze”). That enzyme removes the sugar N-acetyl-beta-D-glucosamine from either serine or threonine residues of proteins. The opposing reaction, catalyzed by O-GlcNAc transferase, like other post-translational modifications, is a common way for cells to regulate proteins. In the case of tau, having that sugar in place reduces aggregation.
All of the OGA inhibitors being developed are small molecules suitable for oral administration. The smaller company with an OGA inhibitor program is Asceneuron, based in Lausanne, Switzerland. They expect to start a Phase I human trial in 2016 although they are still in an early stage of mouse model trials and they haven’t settled on one lead compound for further development. The larger company, Merck, is at a more advanced stage. Their drug, MK-8719, has shown that it can slow brain degeneration in mice transgenic for one of the FTD MAPT mutations. The drug also inhibits tau aggregation in a human iPSC line and in an early Phase I human trial in healthy volunteers was found to be well-tolerated and to increase O-GlcNAcylation in blood mononuclear cells.
Let’s hope that both companies move their OGA inhibitors to Phase II trials in the next couple of years.

A welcome formality

I see my patients with PSP on special clinic days when I have arranged for specialized professional help and have allotted extra time for the visits. The downside is that that it can be a dispiriting few hours, with little to offer anyone that day beyond symptomatic treatment, information and a pep talk. So I use this blog to accentuate the positive.

In that vein, I’m happy to report the drug/biotech industry’s efforts to develop a therapeutic antibody are proceeding apace. The latest tidbit is that the FDA has granted orphan drug status to the anti-tau antibody designated C2N-8E12 being developed by a joint venture of C2N Diagnostics and Abbvie. A 32-patient Phase I trial headed by Adam Boxer at UCSF will begin sometime soon. Achieving orphan status allows the company certain financial advantages and a longer patent life. Both are critically important for any new treatment for a rare disease, as the potential profits wouldn’t otherwise justify the development cost and risk.
Several other companies are working on anti-tau therapeutic antibodies, many of them aiming initially at PSP. Their ultimate Holy Grail is a treatment for Alzheimer’s, but it’s easier to conduct a clinical trial in PSP, as its progression is more readily predicted and measured. Furthermore, tau is the only protein known to aggregate in PSP, which makes that disease a simpler “model system” than AD, where both tau and beta-amyloid aggregate. The company furthest along this road is Bristol-Myers Squibb, whose tau antibody trial seeks 48 patients with PSP at 12 centers across the US and will start enrolling in a few weeks.
So I’m hoping for sunnier PSP clinic days soon!

Speech therapy in PSP?

The Lee Silverman Voice Training (LSVT) “Loud” program is a popular method used by speech/language clinicians to improve vocal volume and clarity in people with Parkinson’s disease.  I’ve never been all that enthusiastic about it because there is no literature demonstrating superiority to traditional forms of speech therapy for PD.  For another thing, I’m a little suspicious of its proprietary financial model, where a clinician pays anywhere from $300 (for a student) to $990 (for a professional) for a two-day course that yields a certificate permitting them to advertise that they offer LSVT.   The courses and certificates are available only from LSVT Global, Inc.

Potential evils of capitalism aside, it’s good to see someone finally trying to help the dysarthria of PSP.  Our heroes are a group in Rome headed by the well-regarded movement disorders authority Fabrizio Stocchi, MD PhD.  The paper‘s first author is Patrizio Sale, MD PhD. a neuro-rehabilitation specialist.  The work appeared in the European Journal of Physical and Rehabilitation Medicine.

The study compared the benefit of LSVT Loud in 16 patients with PSP to the same four-week course of treatment in 23 patients with PD.  Both groups did improve in most of the measures applied.  Probably the most positive result was in the reading task, where the maximum volume for the patients with PSP improved from an average of 82.5 dB to an average of 87.5 dB. Somewhat more modest benefits accrued for nonverbal phonation and for non-reading speech.

Unfortunately, there were no control patients receiving sham treatment, traditional treatment or no treatment.  We don’t know if the improvement will long persist, but the literature suggests that it does so in PD.  Equally important is that the study did not evaluate articulation — only volume.  Furthermore, the study was quite small, inviting flukey results.  Clearly, more work is needed, but for now, I’ll try sending some of my patients with PSP and hypophonia (low vocal volume) for LSVT.  I’ll let you know what happens.

A new PSP genetic risk factor screener

Genetic screening is emerging as a routine and necessary step in clinical research in the neurodegenerative diseases. If you’re looking for the cause of a family cluster, for example, you have to rule out the genetic variants already known to be associated with that disease. If you’re working up a geographical cluster of PSP, as my colleagues in France and I are, you have to look for a genetic founder effect before embarking on a difficult search for environmental causes, and the place to start is with gene variants already known to increase disease risk.
Pathological overlap among the various neurodegenerative diseases is another major current theme. For example, LRRK2 mutations can cause any of a number of pathologies, including PSP, and the tau H1 haplotype is associated with PSP, CBD and PD. It would therefore be convenient to have a single genetic screening device would allow different labs studying different diseases to compare or merge results.
Such a gizmo is now here. It’s a superset of Illumina’s Infinium HumanExome BeadChip called NeuroX. It tests for not only the standard 242,901 gene variants usable in studying any condition but also an additional 24,706 variants focusing on Alzheimer’s, Parkinson’s, MSA, ALS, FTD, multiple sclerosis, Charcot-Marie-Tooth disease, myasthenia gravis — and PSP. The chip is designed to allow easy substitution of subsequent versions of both the basic Illumina chip and easy addition of new neurological variants.
The first author of the report in Neurobiology of Aging is Mike Nalls and the senior author is Andrew Singleton, both of the NIH. The genetic variants included in the chip were derived from multiple genome-wide analyses over the past 20 years. Disclosure: I’m listed way down on the list of “authors” because I was a leader of “GenePD,” one of the consortia whose findings were used in constructing the new chip.  But I have no financial interest in the invention.
At a cost of $57 per sample plus the cost of the basic machine and technician time, you won’t have to be a drug company or the NIH to afford a statistically meaningful series; genetics core labs will be able to offer this as a routine procedure.

My lecture on the treatment of PSP, MSA and CBD

I’m at the annual meeting of the Movement Disorders Society, now officially the International Parkinson and Movement Disorders Society (why the redundancy?).  I just gave a lecture on the treatment of PSP, MSA and CBD.  My bad – I didn’t get the PowerPoint file to the organizers in time for it to be included as a hard copy in the handout, so here it is: Treatment of PSP and CBD – L Golbe  You can download it even if you didn’t attend the conference.  You’re welcome.