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Letter from Ionis Pharmaceuticals & Biogen
to the MDF Community

Dear Members of the Myotonic Dystrophy Community,

Our Recent Clinical Trial Announcement

Over the past several years we have gotten to know many families living with myotonic dystrophy and have been deeply affected by their experiences. With the recent data announcement on the IONIS-DMPKRx safety study, we understand that there is much disappointment within the community, and we feel it is important to follow up and address some of your concerns.

What the Trial Was Designed to Do

The IONIS-DMPKRx study was designed as a dose escalation study to assess drug safety, but also included a number of exploratory endpoints, such as strength evaluations and the collection of muscle biopsies. IONIS-DMPKRx is designed to target the toxic DMPK RNA in muscle that is responsible for myotonia or muscle dysfunction in DM1 patients. The analysis of muscle biopsies had 2 objectives; the first was to analyze the RNA for effects of the drug on the DMPK target and other biomarkers involved in DM1, and the second was to measure actual drug levels achieved in the target tissue, muscle. Those exploratory endpoints provided an opportunity to evaluate if IONIS-DMPKRx was reducing the toxic DMPK RNA in muscle tissue.  

What We Learned

The good news was that we were able to observe some changes in biomarkers such as RNA splicing and could detect low levels of the drug in muscle tissue. While we gained important learnings from this study, based on our experience we feel that these changes were not large enough to produce the level of clinical benefit we hope to achieve. These data, combined with advances in our antisense technology that have allowed us to further improve delivery and potency in muscle tissues using our LICA technology, led to our decision not to advance IONIS-DMPKRx.

Improving the Chemistry for Our Next DM Therapy Development Effort

In addition to improving the chemical foundation of our drugs, we designed our LICA technology to enhance the delivery of our drugs to particular tissues. This technology adds specific chemical structures or molecules called ‘conjugates’ onto antisense drugs to increase the efficiency of drug uptake and delivery to a particular tissue. We have demonstrated that our LICA technology can further enhance the potency of our drugs. And although IONIS-DMPKRx is not moving forward, importantly, the study provided a much better understanding for how future studies and improved clinical endpoints may be used.

Committed to Developing Therapies for Myotonic Dystrophy

Ionis and Biogen are still committed to the DM patient community and are already working to advance the development of a new investigational compound to target DMPK for the treatment of myotonic dystrophy type 1. We are dedicated to working on advances in a new muscle-targeting LICA chemistry to increase potency and hope to advance an investigational compound into development. Our intention is to identify a new compound as soon as possible and, while it’s early to say exactly when the new compound would be ready for clinical trial, we are optimistic and we are pursuing this with urgency.  

Thank You!

Lastly and most importantly, we know that we would not be here without the support of the families participating in our clinical studies, the study doctors and clinicians who provide exceptional care for these families and the entire patient community who inspire us to be at our best each and every day. Thank you all for your unwavering support!


Ionis and Biogen


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