Hypersomnia Research-Where We Are and Where We Are Headed
During the presentation by David Rye, MD, PhD, titled “What are the latest developments in research on idiopathic hypersomnia?” at the Beyond Sleepy in the Mile-High City Hypersomnia Conference, he pointed out that, while on the one hand without a known biological biomarker there is a large unmet clinical need for people with idiopathic hypersomnia, on the other hand a growing awareness garnering increasing interest and recognition within the medical community is gaining momentum.
Following is an abbreviated summary of his talk prepared by Dr. Michelle Emrich. As Dr. Rye had mentioned, this is not an all-inclusive list but specific highlights of recent development in research, collaboration, and treatments of idiopathic hypersomnia:
- In the fall of 2016, the Emory University sleep research team and collaborators anticipate applying for a newly announced FDA orphan products natural history grant that has the possibility to yield $400,000/yr of additional financial support for up to 5 years.
- Nearly half of chronic fatigue syndrome (CFS) patients meet MSLT criteria for IH. Data not yet published. Population based control MSLTs (n=1019) summarized courtesy of E. Mignot vs. CFS (n=46) from Wichita, KS (Reeves WC, et al BMC Neurol (2006); 6:41).
- Studies of non-sleepy controls indicate that nearly ¼ (22%) are asleep by 8 minutes, which demonstrates that MSLT based criteria of ≤ 8 minutes put forward by the International Classification of Sleep Disorders (ICSD) is poor at discriminating IH from controls (i.e., it is a “poor” test in lacking specificity).
- 71% of IH with long sleep have MSLT > 8 min (i.e. considered to be normal), showing that MSLT based criteria also have poor sensitivity for rendering a diagnosis of IH (C Vernet and I Arnulf, Sleep (2009)).
- A “cluster analysis” (i.e., unbiased probing for the degree of commonality of symptoms) by Sonka, Susta and Billiard suggests that IH and Narcolepsy Type 2 (NT-2) share more similarities than differences. (Narcolepsy with and without cataplexy, idiopathic Hypersomnia with and without long sleep time: a cluster analysis. Sleep Medicine 16(2):225-31).
- Dr. David Plante (U. Wisconsin) is continuing his work looking at hypersomnia in affective disorders (e.g., depression and bipolar disease). Sleep propensity in psychiatric hypersomnolence: a systematic review and meta-analysis of MSLT findings. Sleep Medicine Reviews – in press (2016).
- Dr. Plante has a five-year K23 training grant from the National Institutes of Health (NIH). Research
- Aim #1: to probe for deficits in slow wave electroencephalogram (EEG) activity in depression with hypersomnolence as standard sleep variables demonstrate increased sleep duration with normal efficiency in major depressive disorder (MDD) with comorbid hypersomnolence.
- Aim #2: increased EEG slowing during wakefulness. Global reductions in pre/post sleep waking theta frequency band in MDD without hypersomnolence (relative to controls and hypersomnolent group).
- Aim #3: Investigate slow wave induction as a treatment strategy. Subject recruitment is planned for Fall 2016.
- Dr. Plante has also been successful in getting a strategic research award from the American Sleep Medicine Foundation (ASMF) to test the usefulness of a multidimensional assessment in improving the evaluation and treatment of hypersomnolence. Questions he’ll be looking at with this research award:
- Do novel objective hypersomnolence measures incorporated into routine MSLT workflows capture aspects of hypersomnolence not quantified by current standards?
- Is the Hypersomnia Severity Index a valid subjective measure in patients referred for evaluation of suspected CNS disorders of hypersomnolence? This is a new index he’s developed.
- Do novel objective measures of sleepiness and the Hypersomnia Severity Index faithfully capture improvement with treatment?
- Dr. Lynn Marie Trotti (Emory University) also has been awarded a K23 training grant from the NIH relevant to IH and hypersomnia.
- Aim 1: Define functional neuroimaging signatures of pathological sleepiness of different etiologies (IH vs. Narcolepsy Type 1 during WAKE). She anticipates unique signatures by disease state diagnosis in FDG-PET regional hypo- metabolism. She hypothesizes that in the resting state functional magnetic resonance imaging (fMRI) will reveal increased connectivity within what has been termed the brain’s “default mode network” (DMN) whereas portions of this brain circuit will deactivate when subjects perform a simple cognitive task (N-back). Diffusion Tensor Imaging (DTI) – decreased fractional anisotropy will also be explored. Aim 2: Brain circuits underlying the symptoms of sleep drunkenness in IH will be explored with similar imaging modalities.
- Dr. Andy Jenkins’ (Emory University Depts. of Anesthesia and Pharmacology) research continues to move forward. Midazolam and other drugs in the benzodiazepine class exert their sedative actions via gamma-amino-butyric acid (GABA) by binding between the alpha and gamma subunits of the GABA-A receptor. Dr Jenkins and his team are attempting to decipher precisely the presumptive somnogen that contributes to hypersomnia in many IH and NT2 patients that is acting on the GABA-A receptor. They are methodically exploring the % change in small, GABA-mediated current results after making single amino acid substitutions on the alpha2 subunit of the GABA-A receptor. So far they have successfully identified how small changes dramatically influence how well GABA does its job.
- Is somnogen bioactivity specific to IH or might it be a biomarker for other origins of hypersomnia/hypersomnolence? The large NIH R01 grant awarded to Emory University and Dr. Rye supports studying this by comparing IH & NT2 and their spinal fluids with clinical features and spinal fluids collected from sleepy and non-sleepy sleep apnea patients, and non-sleepy controls. They are also anticipating assessing Kleine-Levin-Syndrome (KLS) patients both when in and out of their episodes of hypersomnia.
In order to help discover/define the biological pathways in which the somnogen calls “home” as well as, ultimately, the very nature/structure/chemical identity of the somnogen itself, the Emory University sleep research team is collaborating with:
- Dr. Nicholas Seyfried – Assistant Professor in the Emory Dept. of Biochemistry is the lead investigator applying proteomic methods to spinal fluid samples.
- Dr. Art Edison – A University of Georgia (U) Georgia Research Alliance scholar is the lead investigator applying metabolomics methods to spinal fluid samples.
- Dr. Mark Bouzyk – Founder and Chief Scientific Officer of AKESOgen – is studying genetics
- Dr. Gary Bassell – Chairman of Emory’s Dept. of Cell Biology – is especially interested in studying myotonic dystrophy patients (in whom hypersomnia is a prominent symptom). RNA splicing abnormalities in myotonic dystrophy cause problems with proteins derived from RNA. The GABA 2γ receptor subunit in myotonic dystrophy because of this altered splicing yields a receptor more sensitive to the effects of the sedating benzodiazepine midazolam (see above).
Genetics/Molecular Biology– Daly DD and Yoss RE A family with narcolepsy (Mayo Clinic Proceedings (1959) 34:313-319). Dr Rye spoke about this during this conference as well as at the 2015 Hypersomnia Foundation Conference. Four generations of this family were identified. Narcolepsy Type 1 is now known not to be as heritable as the sleepiness described in this family. Only 3 of 13 (16) of these family members exhibited cataplexy. So hypersomnia/hypersomnolence, not Narcolepsy Type 1, appears to be what’s being inherited in this family. Dr Rye also showed several smaller family trees collected at Emory, in which IH, Narcolepsy Type 2, and long sleepers cluster together in families.
Toward genetic research Dr. Rye/Emory has collected $187,500 in donation commitments to begin studies of the genetic components underlying IH and related disorders. The overall goal is to raise $250,000 to fund these preliminary studies, and using this data to position themselves to apply for larger streams of NIH or foundation funding. They are in the process of collating samples and deciding how to best assign diagnoses given the diagnostic challenges alluded to above (e.g, IH vs. Narcolepsy Type 2 vs. long sleepers). The team is also discussing internally and with external collaborators what best first strategies to employ (Genome Wide Association Studies (GWAS) vs. whole exome sequencing [which would be feasible and possibly more fruitful with larger families inclusive of affected and unaffected individuals]).
Most comparable GWAS studies require ~ 1000 samples. The Emory sleep program has 825 plasma samples, 783+ DNA samples, 473 CSF samples. Including DNA samples collected since November 2015 waiting cataloging into their larger biorepository.
Also, 11 patients with repeat CSF samples have been collected under different clinical conditions, which should be very useful for determining what features are unique to wellness vs. hypersomnia by way of proteomic and metabolomics comparisons.
Very recently skin biopsies h=are being collected to derive fibroblasts from which they are then able to morph into immature brain cells to study more intensively, and in a repeated manner.
Clinical Trials & Treatments: Pentylenetetrazol (PTZ; aka BTD-001). This is an anti-GABA-A receptor study drug with mechanism action similar to that of clarithromycin. It is being further developed/studied by Balance Therapeutics for the treatment of cognition and memory deficits in Down’s Syndrome as well as hypersomnia/hypersomnolence in IH and Narcolepsy Type 2. Interestingly, PTZ is still available as one ingredient (viz., cardiazol) of a cough syrup available in Italy. This is the ongoing clinical trial with the acronym of ARISE. Www.arisestudies.com is the first industry sponsored clinical trial of any treatment seeking FDA approval for treatment of IH. This trial is testing the efficacy of Pentylenetetrazol (PTZ) in a rigorous, controlled, crossover, and blinded design. ARISE is actively enrolling patients at > 20 centers including Emory University (see the website for participating centers). This drug has a long and substantial safety record (i.e,. Phase 1 requirement of safety in humans has already been established). A small, unblinded Phase IIa study – 5 subjects (3 IH and 2 Narcolepsy Type 2) each with hypersomnia responsive to clarithromycin and/or flumazenil demonstrated very promising results. So much so that the much larger Phase IIb study is moving forward necessitating recruitment of 120 subjects (60 each with IH and Narcolepsy Type 2).
Emory’s open label experience with flumazenil continues to be promising and publication of their “open-label” experience in an initial 153 treated patients is forthcoming. The paper was accepted June 27, 2016 publication in the Journal of Clinical Sleep Medicine. Beyond this experience which is limited to those patients seen and treated by Drs. Rye or Trotti prior to January 1, 2015, it is estimated that nearly 300 patients with hypersomnia resistant to traditional treatments with wake promoting drugs have been empirically treated with flumazenil through Emory’s outpatient sleep clinic alone. Many additional physicians outside of Emory are increasingly prescribing flumazenil to their patients.
Much has transpired since the 1950’s when Dr. Bedrich Roth coined the term “idiopathic hypersomnia” and progress will continue as we work together and tease out understanding of the causes of idiopathic hypersomnia.