Gene Editing

The basic science discovery of an adaptive immunity system that evolved in bacteria as a DNA-targeting viral defense mechanism was so revolutionary that early manuscripts from three independent labs were rejected by multiple journals. From that inauspicious beginning, CRISPR/Cas9 technology is rapidly advancing toward clinical trials in multiple disease indications. 

Even that renowned purveyor of scientific knowledge, The New Yorker, has touted the therapeutic potential of CRISPR/Cas9 gene editing (see "The Gene Hackers").

Gene editing is rapidly moving toward clinical trials, indeed ex vivo editing of T-cells in order to target tumors was approved by the National Institutes of Health’s (NIH) Recombinant DNA Advisory Committee (RAC) and trials are anticipated to start in early 2017. By design, the oncology clinical trial largely avoids many potential barriers to CRISPR/Cas9-based therapies—efficiency of gene editing, safety, delivery and ethics. It is not surprising that a disease where ex vivo gene editing is a plausible therapeutic strategy is the first to reach clinical trials.

Possibilities for DM

For myotonic dystrophy (DM), gene editing is an attractive, but currently theoretical strategy for directly addressing the primary genetic defect by excising pathogenic expanded CTG or CTTG repeats. Recognizing that expanded repeats are present in every cell, thereby requiring in vivo gene editing, the DM field must address all of the barriers noted above if clinical trials are to become a reality.

A recent publication from Dr. Bé Wieringa and colleagues takes an important step in assessing the feasibility of CRISPR/Cas9-mediated somatic gene editing for DM. In studies of myoblasts from normal subjects, DM1 patients, and immortalized mouse myoblasts (DM500), the research team explored ways of modulating efficacy of expanded repeat excision. They evaluated both unilateral (from one side of the repeat tract) and dual CRISPR cleavage strategies. 

The group’s findings show specificity in removal of normal and expanded CTG repeats from the DMPK locus. Their dual CRISPR editing approach resulted in unusually large deletions (kilobase size, encompassing the entire expanded repeat) with no adverse biologic consequences for gene expression, DMPK mRNA localization, MBNL distribution or myogenesis. Unilateral cleavage of an unstable genomic repeat was viewed as unadvised, since the ensuing recombination repair may produce unpredictable genomic changes.

The promise of gene editing lies in its objective of stopping downstream pathogenic mechanisms via correction of the primary DNA defect. The challenges lie in establishing safety (putative off-target editing), further optimization of editing efficacy/efficiency, and ensuring bioavailability of CRISPR/Cas9 reagents to tissues impacted by DM. These are not trivial barriers, but the latest findings by Dr. Wieringa and colleagues provide important in vitro proof of concept and thereby represent an important step.

Reference:

CRISPR/Cas9-Induced (CTG⋅CAG)n Repeat Instability in the Myotonic Dystrophy Type 1 Locus: Implications for Therapeutic Genome Editing
van Agtmaal EL, André LM, Willemse M, Cumming SA, van Kessel ID, van den Broek WJ, Gourdon G, Furling D, Mouly V, Monckton DG, Wansink DG, Wieringa B.
Mol Ther. 2017 Jan 4;25(1):24-43. doi: 10.1016/j.ymthe. 2016.10.014.

When Dr. Thurman Wheeler was a resident in neurology, he remembers a senior physician telling him that myotonic dystrophy would probably be one of the most difficult diseases to treat because it involves so many body systems. But thanks to unprecedented advances in laboratory and clinical research since then, “it looks like it might turn out to be fairly straightforward,” Dr. Wheeler says. Now an assistant professor of neurology at Harvard Medical School and a clinical neurologist at Massachusetts General Hospital, Wheeler has spent more than a decade caring for patients with myotonic dystrophy (DM) and conducting lab-based DM studies using mouse models.

Dr. Wheeler recently received a one-year grant through MDF to develop new serum-based biomarkers in adults and children with type 1 and 2 myotonic dystrophy (DM1 and DM2) for use in therapeutic trials. (For more about MDF grants, see Fellows & Grant Recipients. Additionally, information about the Wyck Foundation and its related grantees is available).

Searching for DM Biomarkers in Body Fluids

Dr. Wheeler’s grant, which runs from November 2016 through October 2017, will allow him and his team to begin initial exploration of the viability of developing DM biomarkers that can be measured in blood and urine, reducing or avoiding the need for muscle biopsies – which are invasive and risky – to support data collection in clinical studies and trials.

Dr. Wheeler will examine differences in extracellular RNA that are associated with DM1 and DM2 compared with healthy controls, and look for possible changes in these RNA forms and levels that correlate with disease activity or treatment response.

"We’re looking for extracellular RNA in blood and urine," Wheeler says. "A few years ago, a colleague here found that blood has extracellular RNAs that can serve as biomarkers for brain tumors," Wheeler says. "We’re going to be adapting the approach of the study that looked for markers of brain tumors and use that for myotonic dystrophy. We’re examining gene expression, splicing, microRNAs, and things like that."

Dr. Wheeler and colleagues will be studying extracellular RNA in adults and children with DM1 and DM2, in collaboration with neurologist Basil Darras at Boston Children’s Hospital.

The collaboration with Dr. Darras, who sees more pediatric patients than does Dr. Wheeler, is important, Wheeler says, “because this enables us to expand the study in children. Muscle biopsies in children require general anesthesia, he notes, “and that’s something you want to avoid in myotonic dystrophy, because patients can have a difficult time coming out of it. So, if we’re successful, we may be able to include children [in clinical trials] much earlier than originally thought.”

Early Years in the Clinic and Lab

Wheeler, who graduated from the University of Washington School of Medicine in 1995 and then completed a neurology residency at that institution, first became interested in muscular dystrophy research during a fellowship in neuromuscular medicine at Johns Hopkins University.

He then moved to Stanford University to work with Tom Rando, M.D., Ph.D., on developing nonviral gene therapy for Duchenne muscular dystrophy. Then, as now, the potential for unwanted effects associated with using viral vectors as gene delivery vehicles was well understood, and the Rando lab was looking to reduce this downside.

"We were doing plasmid and oligo work," Wheeler recalls. "[Dr. Rando] was using a type of non-viral gene therapy called antisense for gene correction of point mutations in a mouse model of Duchenne muscular dystrophy.  It involves using an oligo that’s complementary to the region across the point mutation except it has the correct base."

After three years at Stanford, Wheeler took advantage of an opening at the University of Rochester (N.Y.) to switch gears and study DM. “I knew what myotonic dystrophy was," he says, “but I had never done any research on it. I moved to Rochester, took what I learned about nonviral gene therapy from Tom, and applied it to myotonic dystrophy.”

"We ended up getting antisense to work for exon skipping to eliminate myotonia [in a DM mouse model]. The chloride channel RNA is misspliced in myotonic dystrophy. There’s an exon included aberrantly in the disease state. So if you use antisense to induce skipping of that exon, that can potentially rescue the myotonia, because you’d be restoring the normal chloride channel RNA, and that leads to a normal chloride channel protein. We did that in mice, and it worked beautifully.”

Correction of chloride channel splicing wasn’t taken forward into drug development, Wheeler says, "because there’s much more to myotonic dystrophy than myotonia. You’d eliminate the myotonia, but ultimately you’d be doing nothing for the rest of the symptoms."

It did, however, provide evidence that antisense could be an effective therapy, setting the stage for therapy development to target the fundamental DM1 RNA defect – expanded CUG repeats in the DMPK gene. “In parallel, we were working on CUG targeting,” Wheeler says of his Rochester work. “We were doing them both at the same time, and we finished the chloride channel work first. But we knew that the CUG targeting was working in the mice and that that could be a long-term answer.”

Developing Antisense for DM1 Treatment 

At first, the Rochester team’s goal was to develop antisense against the CUG repeat expansion in the DMPK gene. "We originally were using antisense that was targeting the repeat expansion directly," Wheeler recalls, "and the concern was that there are other genes that have shorter CUG repeats where that could interfere. We didn’t really find that in mice, but it was a theoretical concern."

Then came involvement with Ionis Pharmaceuticals, a Carlsbad, CA-based biotechnology company specializing in RNA-targeted drug discovery and development. 

"We tried some of the Ionis drugs that they developed earlier, but they didn’t really work very well," Wheeler says. "Then Ionis suggested we try their gapmer approach, and that worked incredibly well." A gapmer, he explains, refers to the design of the antisense. “The antisense has modified RNA at the 3-prime and 5-prime ends, separated by a central gap of DNA. When the oligo binds to the target RNA, you get a DNA-RNA heteroduplex that is recognized by RNAse H, which cleaves it. When the cleavage happens, the rest of the transcript is degraded by exonucleases." Non-gapmer antisense compounds, he explains, "just bind to the target and kind of sit there."

Unlike earlier antisense approaches for DM1, the Ionis gapmer approach did not directly target the CUG repeat expansion. "It targets outside the repeats," Wheeler says, thus removing the risk of inadvertent binding to CUG repeats in other genes. And, since RNAse H is located in the nucleus, the strategy preferentially targets aberrant DMPK RNA transcripts, which get stuck in that location, while normal DMPK RNA quickly leaves the area. "Transcripts that have a prolonged dwell time in the nucleus appear to be more susceptible,” he notes, although “potentially, the gapmer still could target the pre-messenger RNA of DMPK alleles with non-expanded repeats [normal alleles], so that is one of the things we’ll be watching in the clinical trials."

A phase 1-2 trial of IONIS-DMPKRx-2.5 in adults with DM1, testing the gapmer antisense against DMPK RNA at multiple U.S. centers, opened in 2014. It ended in late 2016, with results reported in January 2017. “I know that Ionis has taken great steps to test the safety ahead of time, and it’s been very effective in mice and other preclinical models of DM1,” Wheeler says. While the Ionis clinical trial did not achieve sufficient drug levels in skeletal muscle, they are exploring two other antisense oligonucleotide molecules that show promise of greater potency.

Move to Harvard

As fruitful and exciting as his time at the University of Rochester was, Wheeler was eager to expand his lab-based research and begin clinical work in DM and other muscular dystrophies. With that in mind, in 2013, he relocated to Massachusetts General Hospital and Harvard Medical School.  “It was just a great professional opportunity,” he says. “It was a natural step. In Rochester, I was doing no clinical work. Here I have a research lab that focuses on developing new biomarkers, including this new clinical project [for biomarker identification], as well as studying the factors that make muscles weaker and identifying new treatments for myotonic dystrophy. I also have an all-ages clinic every week and a pediatric clinic twice a month where I see patients with both types of myotonic dystrophy and all other forms of muscular dystrophy.”

Improving and Expanding Clinical Trials

“I’m optimistic that [antisense oligonucleotide therapies] will be safe and have some therapeutic effects,” Wheeler says. “I guess the question is to what extent the knockdown of the expanded repeat RNA will reverse the symptoms. In someone with mild symptoms, the drug may have a tremendous effect and slow progression.  But how will it work for patients who have a greater degree of weakness, more muscle atrophy, or problems walking?  Will the drug be able to improve their function at all? Or will we need to develop second-line therapies, the way the Duchenne dystrophy field is doing?”

Downstream effects of the expanded CUG repeats that appear to contribute significantly to disease symptoms include functionally low levels of the MBNL proteins and abnormally high levels of the CELF1 protein. Increasing MBNL activity and reducing total CELF1, preferably with small molecules, might add a lot to antisense therapy, Wheeler notes. “A small molecule that you could take by mouth would be ideal,” he says. “Until we have something that is proven to be highly effective, I think we should continue developing new therapies that target the disease from different angles.”

Continuing clinical trials of new DM therapies, including those for children, will require reliable biomarkers of disease activity, preferably markers accessible in blood or urine rather than muscle markers that require biopsies. 

“The plan is to begin the process of identifying biomarkers,” Wheeler says of his new grant. “That was one of the goals described by MDF. They want to find a project that is working toward biomarkers that will be on track to get qualified by the Food and Drug Administration (FDA).  

“The goal that I have is to try and reduce the need for muscle biopsies by looking at biofluids, so that there’s no anesthesia, no incision, no scarring, and no bleeding risk. This would allow monitoring during the treatment trial instead of waiting until the end.

“We had our first contact with the FDA back when the grant was submitted, which was in June [2016]. I think that no one expects that we’re going to have a biomarker or a group of biomarkers by the end of the year, but we’re going to be working toward that goal.”

For more about Dr. Wheeler’s MGH-based research, see Wheeler Muscular Dystrophy Research Lab. For information about muscular dystrophy clinics for adults, call (617) 726-3642; for children, call (617) 643-4645. Recruitment for the biomarker study is being done through the clinics.

Patient-reported data from MDF’s Myotonic Dystrophy Family Registry (MDFR) indicate that impaired sleep or daytime sleepiness are among the most prevalent symptoms of DM1, experienced by over 76% of patients. Despite the prevalence and substantial burden imposed by sleep disorders, studies report that many patients do not receive treatment.

Dr. Sophie West and colleagues at the Newcastle Regional Sleep Service and Institute of Genetic Medicine, Newcastle University have evaluated a large cohort of patients with daytime sleepiness and assessed the effectiveness of a variety of treatment strategies. Since many DM1 patients do not have immediate access to facilities providing optimized and integrated care, it is important to understand and disseminate best care practices among their physicians.

In a prospective study of 120 DM1 individuals presenting with daytime sleepiness, the Newcastle group used thorough overnight sleep studies to stratify patients into treatment regimens that are commonly used for sleep disorders but not yet rigorously validated for DM. Obstructive sleep apnea, respiratory failure, and sleepiness accompanied by a normal sleep study were prevalent among the DM1 study patients. Four treatment regimens were evaluated: (a) those with hypercapnia were offered non-invasive ventilation (NIV); (b) obstructive sleep apnea patients offered continuous positive airway pressure (CPAP); (c) those with daytime sleepiness and no underlying disorder detected from sleep studies were offered modafinil; and (d) a non-treatment group with normal sleep studies or with disorders but declined the interventions.

Those receiving each intervention and, parenthetically, the percentage deriving benefit were as follows: NIV for respiratory failure (37%), CPAP for obstructive sleep apnea (33%), and modafinil for daytime sleepiness with no sleep disorder (33%). Overall, 29% of patients studied derived benefit from interventions that are in general use for more common disorders. Differences in Epworth Sleepiness Score distinguished responders (ESS = 15.9) from non-responders (ESS = 11.9) across all interventions. The authors point to the need for either a meta-analysis of published studies or a randomized controlled trial in order to better understand the features of modafinil non-responders.

Report Findings

Dr. West and colleagues conclude that comprehensive diagnosis of sleep disorders in DM1 is essential in directing patients toward specific, most-effective interventions. They point to the diverse causes of sleep and breathing disorders in DM and advocate for this tailored approach to treatment. Taken together, the authors view a detailed, diagnostic approach as superior, both in treatment efficacy and overall costs, to simply using the predominant symptomatology at presentation as a guide to improving patient care. These findings also provide a strong argument for comprehensive care guidelines, readily available to both physicians and patients, to ensure optimum quality of care for all living with DM.

Reference:

Sleepiness and Sleep-related Breathing Disorders in Myotonic Dystrophy and Responses to Treatment: A Prospective Cohort Study.
West SD, Lochmüller H, Hughes J, Atalaia A, Marini-Bettolo C, Baudouin SV, Anderson KN.
J Neuromuscul Dis. 2016 Nov 29;3(4):529-537

Construction of a conceptual framework that integrates phenotypic, cellular and molecular data in DM is a critical step in developing a robust and diverse pipeline of candidate therapies. Although basic science has mechanistically linked the inherited repeat expansions to DM1 and DM2 phenotypes, there are critical gaps in understanding of disease mechanisms. A recent publication extends our understanding.

Dr. Perrine Castets, Prof. Michael Sinnreich and colleagues at the University of Basel recently studied the notion that perturbation of skeletal muscle metabolic pathways, including those responsible for protein degradation (ubiquitin-proteasome system and autophagy), plays an important role in DM. Their results, published in the Journal of Clinical Investigation, establish that (a) DM1 muscle is characterized by an altered response to energy/nutrient deprivation and that (b) dysregulation of AMPK/mTORC1 signaling, at least in part, underlies the altered metabolic state and its role in the pathogenesis of DM1 skeletal muscle. Importantly, these findings suggest new targets for drug discovery and development.

In studies of the HSALR mouse model of DM1, the investigators showed that a normal molecular response to fasting, AMPK activation and mTORC1 inhibition, is compromised in HSALR mice. Consistent with these findings and the interrelated role of AMPK and mTORC1 in autophagy, experimentally induced autophagy was disrupted in HSALR muscle. Deprivation of energy and nutrient supply in DM1 patient myotubes also produced data consistent with dysregulated autophagy. Finally, targeting either AMPK (with AICAR) or mTORC1 (with rapamycin) signaling improved muscle strength, splicing and/or myotonia in HSALR mice.

While the AMPK agonist, AICAR, disrupted nuclear foci and reduced myotonia, along with partial normalization of splicing (correction of Clcn1, but not Atp2a1 and Camk2b) in HSALR mice, rapamycin’s, an mTORC1 inhibitor, normalization of muscle function was not accompanied by correction of mis-splicing.

Many of the therapeutic strategies under development for DM are based on restoration of dysregulated alternative splicing. The study by the University of Basel group further supports those strategies, but also characterizes a key metabolic defect in DM1 muscle and identifies the mTORC1 pathway as an alternative, splicing-independent target for therapy development.

Thus far, nearly all of the therapy development programs in DM address the muscle phenotype. Recent studies show that the mTOR pathway may be an important target in developmental intellectual disorders, and two mTOR inhibitors have regulatory approval for other indications (Novartis' Everolimus and Wyeth's Sirolimus (rapamycin)). Drugs targeting mTORC1 then may have efficacy for both the skeletal muscle and cognitive symptoms of DM1 and thus their potential should be explored via rigorous efficacy studies in appropriate preclinical models.

Reference:

Targeting deregulated AMPK/mTORC1 pathways improves muscle function in myotonic dystrophy type I.
Brockhoff M, Rion N, Chojnowska K, Wiktorowicz T, Eickhorst C, Erne B, Frank S, Angelini C, Furling D, Rüegg MA, Sinnreich M, Castets P.
J Clin Invest. 2017 Jan 9. pii: 89616. doi: 10.1172/JCI89616. [Epub ahead of print

Biomarkers are a major interest for myotonic dystrophy (DM), but understanding of their utility (Context of Use) in clinical trials can be elusive. The ‘flavors’ of biomarkers relate to the ways they are utilized: diagnostic, prognostic, predictive, pharmacodynamics (PD) and pharmacokinetic (PK). The right biomarkers are invaluable in selecting/stratifying patients, determining on-target activity, and dosing and assessing efficacy and safety of candidate therapies. Arriving at the “right” biomarkers to minimize uncertainty and aid decision-making is essential, but nontrivial, as experiences in Duchenne have so clearly shown.

A simplistic view is that a molecular endpoint identified in a laboratory study can be a panacea in accelerating drug approval. The reality is that, in moving beyond the discovery phase, a range of questions, from methodological to interpretive, must be answered before a biomarker has validity.

Given the high bar for regulatory qualification, biomarker studies ultimately must reside within collaborative networks that recognize that no one gets to the solution alone. A key barrier to overcome is that biomarker qualification is uncharted territory for most academic researchers.

Two recent initiatives, the BEST Resource (Biomarkers, EndpointS, and other Tools) and the Framework for Defining Evidentiary Criteria for Biomarker Qualification, are aimed at clarifying terminology and process with all stakeholders, and thereby accelerating qualification and use of biomarkers in therapy development programs.

The FDA-NIH Joint Leadership Council, dedicated to improving regulatory science, developed the BEST Resource. BEST initially focused on harmonizing the terminology of translational science and biomedical project development. The intent is to provide clarity and consistency in communications among all stakeholders. The BEST glossary is an invaluable resource, going well beyond biomarker and endpoint terminology to provide a wealth of examples and informational links.

The Framework for Defining Evidentiary Criteria for Biomarker Qualification, a partnership led by the Foundation for the NIH that includes NIH, FDA, PhRMA, the Critical Path Institute and pharmaceutical companies, provides “a general framework to assist the development of biomarkers for qualification, to improve upon the quality of submissions to the FDA and to clarify the evidentiary criteria needed to support the biomarker’s "Context Of Use" (pdf). The ready availability of these criteria increases transparency of the qualification process and thereby facilitates interactions between biomarker developers and FDA.

What opportunities exist to exploit these new tools in biomarker development for DM? In a recent DM Research News, MDF highlighted the potential for FDA biomarker qualification of a panel of splicing events identified with the Myotonic Dystrophy Clinical Research Network (DMCRN). The recent clarification of evidentiary standards will markedly aid this effort. In addition, the Wyck Foundation and MDF recently funded Dr. Thurman Wheeler (Massachusetts General Hospital) to explore miRNAs in serum and urine as DM1 biomarkers. While this is a discovery-phase project, it’s important that the new qualification guidance is taken into account even by studies at such an early stage.

A recent publication by Ms. Alessandra Perfetti, Dr. Fabio Martelli and colleagues (IRCCS Policlinico San Donato) piloted circulating miRNAs as putative biomarkers for DM1. Dysregulated miRNAs included miR-1, miR-27b, miR-133a/-133b, miR-140-3p, miR-206, miR-454 and miR-574. Elevated miRNAs correlated with impaired muscle strength and elevated MCK, and could readily distinguish DM1 (103 subjects) from controls (111). Some of the miRNAs identified in DM1 patient samples are non-specific in that they also are dysregulated in Duchenne (miR-1, mIR-206 and miR-133a/-133b), but that does not preclude their potential value as prognostic, predictive, PD or PK biomarkers in DM1. Before a biomarker can be qualified, more extensive studies must assess how this miRNA profile links to pathogenic or regenerative processes across multiple organ systems, and show if these miRNAs are suitable in tracking disease progression and/or drug efficacy.

To achieve qualified DM biomarkers, we all must speak the same “BEST” language and assimilate, rather than silo, lessons learned from each study. But most of all, the DM research community must adopt a highly collaborative culture (valuing community needs over individual publications), since validated, quantitative assays, well-powered and phenotypically rich data sets and inter-site validation are essential in navigating the pathway to effective drug development tools.

Reference:

BEST (Biomarkers, EndpointS, and other Tools) Resource
FDA-NIH Biomarker Working Group.

Framework for Defining Evidentiary Criteria for Biomarker Qualification: Final Version. Evidentiary Criteria Writing Group

Validation of Plasma MicroRNAs as Biomarkers for Myotonic Dystrophy Type 1.
Perfetti A, Greco S, Cardani R, Fossati B, Cuomo G, Valaperta R, Ambrogi F, Cortese A, Botta A, Mignarri A, Santoro M, Gaetano C, Costa E, Dotti MT, Silvestri G, Massa R, Meola G, Martelli F.
Sci Rep. 2016 Dec 1;6:38174. doi: 10.1038/srep38174.

Cognitive impairment is a characteristic feature of adult-onset myotonic dystrophy type 1 (DM1). While some progress has been made in understanding the molecular mechanisms underlying the CNS changes, it has been more difficult to assess DM1-associated cognitive deficits. Barriers to clarifying the patient cognitive profile include disease heterogeneity, difficulties in assembling a sufficiently powered cohort, uncertainty about optimal endpoint selection, and the little information available on the temporal window required to detect meaningful change. Key unresolved questions in DM1 include (a) is the cognitive impairment stable or progressive and (b) if progressive, is impairment restricted to specific functional domains or is there a more global pattern of decline?

The prominence of neuromuscular symptoms, and the accessibility of muscle for molecular, cellular, and functional evaluations, has focused DM1 therapy development on skeletal muscle endpoints. Yet pharmaceutical and biotechnology companies are now recognizing that cognitive changes represent substantial burden of disease, and thus are essential endpoints for patient-focused drug development. Just as was the case for skeletal muscle-focused efforts, a better understanding of the nature, variability, and progression of cognitive impairment in DM1 is needed to facilitate clinical assessment of CNS-targeted candidate therapies and improved patient care.

Cognitive Longitudinal Study

Dr. Benjamin Gallais, a Wyck Foundation/MDF Postdoctoral Research Fellowship recipient, and his colleagues at the University of Sherbrooke and University of Quebec at Chicoutimi have reported a 9-year longitudinal natural history study of cognitive function in a cohort of genetically confirmed, adult- (90 subjects) and late-onset (25 subjects) DM1 patients. The study assessed a battery of neuropsychological tests, including cognition (language, memory, visual attention, processing speed, visuoconstructive abilities, and executive functions) and intellect (WAIS-R 7) at two time points. Careful steps were taken to avoid or minimize unintended bias from subject selection, subjects lost to follow-up, and data collection and analysis.

The overall group of adult- and late-onset DM1 subjects showed major (significant in ≥ 2/3 of subjects) declines over the study period in verbal memory, visual attention, and processing speed, while improvement was noted in verbal fluencies and global intelligence. In addition, the percentage of all subjects with cognitive impairment increased between the initial and final evaluations. Both age and duration of disease at time of study entry negatively correlated with all cognitive domains studied. By contrast, the number of CTG repeats, degree of skeletal muscle impairment (MIRS), and education level all poorly correlated with cognitive and intellect scores. Finally, the rate of cognitive decline over the 9-year period was higher in late- than adult-onset subjects, although overall cognitive performance level at study end was worse for the adult-onset group.

Study Results

Gallais and colleagues concluded that cognitive impairment in adult- and late-onset DM1 is prevalent, moderate in severity, progressive, and global in the range of functions impacted. They suggest that the CNS phenotype seen in this DM1 cohort can be interpreted, at least in part, as an acceleration of normal aging, a hypothesis they support with reference to neuronal accumulation of a neurodegenerative protein (tau), white matter changes, and occurrence of aging-linked signs and symptoms in other organ systems (e.g., cataracts, baldness, erectile dysfunction, and endocrine dysfunction) in DM1.

These findings are important from the perspectives of size of and care in cohort selection, thoroughness of evaluations, and length of study. A caveat is that two time points, 9 years apart, do not provide sufficient resolution of the natural history of CNS impairment to guide clinical trial design. The authors do indicate that the study is continuing with shorter intervals between assessments. While recognizing the value that CNS imaging would have added, the authors note the challenges of including MRI measures in studies of cohorts that are adequately powered for neuropsychological assessments.

The lessons learned here must not be lost, but rather used to impact subsequent natural history studies of cognitive function in DM1. Taken together, the results from this study better characterize the disease and represent an important step forward for the design and selection of DM1 clinical trial endpoints to assess cognition, as well as for further guidance in recognizing and managing cognitive symptoms in patients with adult- and late-onset DM1.

Reference:

Cognitive Decline Over Time in Adults with Myotonic Dystrophy Type 1: A 9-year Longitudinal Study.
Gallais B, Gagnon C, Mathieu J, Richer L.
Neuromuscul Disord. 2016 Oct 14. pii: S0960-8966(16)30846-X. doi: 10.1016/j.nmd.2016.10.003. [Epub ahead of print]

In November, MDF staff met with the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) and the National Institute of Neurological Disorders and Stroke (NINDS) senior leadership and program/policy staff to discuss research opportunities and federal support for myotonic dystrophy (DM). Discussions focused on two areas: the scientific workforce and biomarker and registration endpoint development.

MDF reviewed efforts to support the scientific workforce through the MDF Postdoctoral Research Fellowship program and expressed support for NIAMS and NINDS efforts to extend their R01 paylines for new investigators. Dr. Steve Katz, Director, NIAMS, noted that 58% of K award recipients successfully transition to R type awards and encouraged clinical researchers in DM to utilize the K award mechanism. Dr. Walter Koroshetz, Director, NINDS, noted that 22 academic medical centers currently held NINDS R25 awards to support resident’s research in neurology; he encouraged faculty working on DM at these medical centers to take full advantage of the R25 awards.

MDF also encouraged NIAMS and NINDS to consider mechanisms to support young faculty seeking to renew their initial R01 awards. This is often a critical stage for young investigators (and NIH data bear that out), as they have had to set up their lab, produce on proposed projects, and gather preliminary data for specific aims of the renewal within the initial five or fewer years of funding. The NIAMS and NINDS directors indicated that they were sensitive to the issue. Dr. Katz noted the NIAMS STAR Program (Supplements to Advance Research from Projects to Programs). This program provides up to $150,000 per award in administrative supplements to young faculty on their initial R01 who need additional time and data to obtain either a renewal or a new R01 award. Young faculty with an initial R01 from NIAMS should review the program announcement.

MDF staff also reviewed the Foundation’s role in addressing opportunities and challenges along the entire therapeutic development pipeline. The potential for development and qualification of biomarkers for use in early phase clinical development was highlighted as a timely opportunity in DM. Likewise, overcoming the challenges in developing registration endpoints for drugs and biologics under development for DM were identified as a critical need.

NIAMS Staff pointed to RFA-AR-17-009, Research Innovations for Scientific Knowledge (RISK) for Musculoskeletal Diseases (R61/R33), a program designed for high-risk projects, as a potential means of funding biomarkers and clinical endpoints in DM. NINDS has a continuing program targeted at clinical trial readiness (including biomarker and endpoint development): PAR-16-020, Clinical Trial Readiness for Rare Neurological and Neuromuscular Diseases (U01).

Since the NIAMS initiative has only one application date, and the NINDS initiative is intended for mature projects, such as biomarker qualification efforts, MDF staff strongly encouraged both institutes to consider an initiative to facilitate early discovery and development of biomarkers and endpoint measures for DM. MDF believes the existing funding opportunities are important, and should be considered by investigators, but noted that early stage discovery projects in these areas may not compete well with hypothesis-driven applications and that a targeted initiative is a critical need for the DM field.

Taken together, MDF will remain engaged with the NIH, meeting on a regular basis to ensure that opportunities and critical needs in the DM field receive attention. DM researchers are encouraged to make opportunities and needs known to MDF staff so they can be incorporated into discussions with NIH leadership and program staff.

The multi-system involvement and heterogeneity that characterize myotonic dystrophy (DM) have fostered several efforts to design patient-reported outcome measures (PROMs) for clinical studies and trials. The intent of PROMs is to use patient feedback in design and implementation of validated questionnaires that can simultaneously capture changes across the challenging symptomology of DM while obtaining clinically meaningful information to support regulatory approval. While PROMs can prove insightful as an analytic tool for complex disorders, the potential barriers to PROM design, development, and interpretation are such that the Food and Drug Administration (FDA) developed a Guidance for Industry document (pdf) to aid in development of PROMs. Choice of PROMs for use in interventional trials must then be carefully informed.

Dr. Tara Symonds and her colleagues at Clinical Outcomes Solutions (COS) recently reported out a literature review of available PROMs that focus on type 1 myotonic dystrophy (DM1). COS a is health economics and outcomes research consulting group with considerable experience in understanding PROM design and implementation in clinical studies. Disclosure: The COS project was funded by Biogen, a company engaged in therapy development in DM1.

Dr. Symonds and her group evaluated a health status measure (MDHI), three activities of daily living scales (DM1-Activ, DM-Activc, and Life-H), two health related quality of life measures (INQoL & INQoL Serbian), and five sleep and fatigue measures (ESS, DSS, CFS, FSS, and FDSS) comparing their validity, reliability, and ability to detect change of each to guide choice of PROMs for use in DM1 studies.

MDHI was viewed as the only measure that attempted to capture all aspects of a DM1 patient's life that were impacted. Design of MDHI specifically for DM, internal consistency of the tool across domains assessed, test-retest reliability, and design in compliance with FDA’s Guidance for Industry were viewed as favorable traits. It was also noted that construct validity had been established for MDHI via comparison with a variety of existing functional measures (e.g., MMT, grip testing, and timed function tests).

DM1-Activ also was considered to have good validity and reliability and showed construct validity when compared to various manual testing measures and the Muscular Impairment Rating Scale (MIRS).

Most other PROMs assessed by the authors were viewed as more limited in capability and performance, and all PROMs were thought to require further assessment of responsiveness and meaningful change thresholds in interventional clinical trials. Dr. Symonds and team concluded that MDHI is arguably the best measure for use in clinical studies and trials provided that the critical areas of responsiveness and definition of meaningful change to patient are addressed. DM1-Activ also was deemed to have potential as a PROM in interventional trials, as long as content validity is explored further and the issues of responsiveness and meaningful change prove acceptable. Other measures were considered acceptable in evaluation of specific domains of the symptomatology of DM1.

FDA’s Guidance for Industry supports the use of well-designed and implemented PROMs as putative primary endpoint measures for clinical trials. Even as a secondary measure, a carefully selected PROM can bring considerable value to clinical trials, not the least is insight into meaningful benefit to the patient. The publication by Dr. Symonds and colleagues provides an evaluation of currently available tools by experts outside of the DM community. While current drug discovery and development efforts have focused on skeletal muscle function, desired treatments for DM will have to address a much wider disease burden. Validated and reliable PROMs with an ability to capture changes in multiple symptoms important to DM1 patients may prove to be a valuable tool in natural history studies and definitive clinical trials.

Reference:

A Review of Patient Reported Outcome Measures for Use in DM1 Patients
Symonds T, Randall JA, Campbell P.
Muscle Nerve. 2016 Nov 11. doi: 10.1002/mus.25469.

To date, technological hurdles have been a barrier to creating a mouse model for type 2 myotonic dystrophy (DM2), hindering understanding and treatment development for this disorder. But that’s about to change, thanks in part to the work of Łukasz Sznajder, Ph.D., a recipient of a 2016-2017 research fellowship grant from MDF.

"Currently, there are only cellular and fruit fly models available," says Dr. Sznajder, "and they’re not sufficient to understand the complex nature of DM2. A mouse model is urgently necessary to break this barrier."

Without mouse models it would have been impossible to develop the drugs now being tested to treat most neuromuscular disorders, including type 1 myotonic dystrophy (DM1).

A DM2 mouse model “will provide an excellent platform to evaluate DM2 phenotypes,” Dr. Sznajder says.

It would also allow researchers to study tissues that are hard to obtain from patients, such as those from the cardiac muscle and brain, and it would shed light on the differences between DM1 and DM2.

"My proposed model represents a unique opportunity to distinguish the differences between DM1 and DM2," Sznajder says. "We expect to answer puzzling questions, such as why there is no congenital-onset form of DM2," which is caused by several thousand CCTG repeats in the first intron of the CNBP gene.

"It is worth mentioning that the size of this mutation is several times that of the expansion that leads to DM1," Sznajder says. That, he notes, poses some challenges in developing a DM2 mouse model. "First, the amplification of even a few hundred repeats is not possible using conventional strategies. Second, the precise insertion of these repeats into the mouse CNBP gene is a highly inefficient process," he says.

"New technologies have remarkably improved the efficiency of genome engineering, and we hope to use these technologies to overcome the current challenges in DM2 modeling," he says.

Moving Toward DM2 Therapies

A mouse model will also allow Dr. Sznajder and his team to test therapeutic strategies for DM2 like antisense oligonucleotides and small molecules.

The antisense oligonucleotide-based drug IONIS-DMPKRx, designed to block harmful interactions between expanded RNA repeats and cellular proteins in DM1, is now in a phase 1-2 trial. Dr. Sznajder and his colleagues hope to develop a similar molecule to treat DM2.

"It is scientifically possible to adjust the oligonucleotide sequence to make it useful for DM2," Sznajder says. "However, a good mouse model of the disease is needed to test the efficiency of this or other approaches." His new DM2 mouse is expected to provide this vital tool.

A Passion for DM Research

Dr. Sznajder recently moved from his native Poland to realize his dream of working with a renowned DM researcher in the United States.

Coming of age in Poland in the 2000s, Sznajder decided to become a biomedical scientist, ultimately earning his doctorate in biotechnology and molecular biology from the Adam Mickiewicz University in Poznań in December 2015.

"For some time," he says, "I had dreamed about working at a prestigious university in the United States under the supervision of someone who would enable me to develop my scientific career while following my passion for research in myotonic dystrophy."

During his graduate studies, Sznajder was fortunate enough to work under Dr. Krzysztof Sobczak, who had been a postdoc in the laboratory of Dr. Charles Thornton, a DM researcher at the University of Rochester in New York state and a colleague of Dr. Maurice Swanson.

Under the mentorship of Dr. Sobczak, Sznajder started working on RNA toxicity and MBNL proteins, which he describes as "critical players in the molecular cascade of DM."

Dr. Sznajder is continuing his vital DM research under Dr. Maurice Swanson at the University of Florida.

Patient compliance with prescribed medicine has been the subject of many studies in common and rare diseases—as many as 50% of patients with chronic diseases do not follow the directions provided by their physicians or pharmacists regarding their medications. Compliance with instructions for prescribed medicines does lead to better health outcomes. Unfortunately, only limited information is currently available regarding which medications myotonic dystrophy (DM) patients take, and there is little understanding of barriers that may prevent better DM patients from complying more diligently with the prescriptions provided by their doctors.

In a recent study by Dr. Richard Moxley, III, MD, and colleagues at the University of Rochester, researchers assessed disease manifestations and adherence to medications for DM1 and DM2 patients. The study, titled “Medication adherence in patients with myotonic dystrophy and facioscapulohumeral muscular dystrophy,” was motivated in part by the fact that DM patients need to take multiple prescriptions to manage disease symptoms associated with a number of different body systems. The study also sought to understand how difficulty in swallowing, limited mobility, and reduced employment may impact DM and facioscapulohumeral muscular dystrophy (FSHD) patient compliance with prescribed medicines.

The researchers surveyed adult DM1 and DM2 patients enrolled in the National Registry of Myotonic Dystrophy and Facioscapulohumeral Muscular Dystrophy Patients and Family Members at the University of Rochester. For both DM1 and DM2, muscle weakness was the symptom that patients most commonly viewed as an unmet treatment need, and for which they wanted new therapies to be developed. Patients also cited the need for treatments to improve mobility and reduce fatigue as high-priority issues in DM1, while DM2 patients reported pain as an unmet need. Many patients surveyed took six or more medications. Improved access to physical therapy, exercise, and mobility devices may help reduce reliance on some medications.

Most DM patients reported a good understanding of both their disease and the reasons that they were taking specific medications. Most participants in the study (93% of DM1, 88% of DM2 patients) reported that cost/insurance coverage was not a barrier to compliance with medications prescribed for their DM symptoms. Side effects of one or more medications were important compliance factors for a significant number of DM patients (35% in DM1, 49% in DM2), and were a factor that led to many patients discontinuing a medication (37% in DM1, 60% in DM2). Patients also identified difficulty in swallowing medicines in tablet or capsule form as a barrier to compliance with prescribed medication (33% in DM1, 21% in DM2).

Dr. Moxley and colleagues concluded that the symptoms of DM did not significantly impair patient adherence to medications prescribed for their multi-system disease. DM1 patients identified more of a need for new medications to manage their disease symptoms than patients with DM2. DM patient compliance with medications was, overall, better than literature reports for other chronic diseases, and participants in the study felt that their medications did not negatively impact their social or work lives. Finally, the authors of the study noted that community pharmacists can be an excellent source of advice when taking multiple medications and in overcoming barriers to compliance. Going forward, there is a need to identity and evaluate the effectiveness of specific medications that are used in DM, and to identify strategies to address barriers such as difficulty in swallowing, to help ensure optimal care for patients living with DM.