Dear Patient Group Representative,
We are writing as we would like to share with you that as of January 12, 2014, Prosensa has regained
the rights to drisapersen from GSK and retained the rights to the other DMD programs.
Prosensa and GSK have issued a press release to announce this news, and I have attached the
release for your reference. Study investigators have also been notified of these changes and are
recommending that boys and their families currently participating in drisapersen clinical studies
contact their local clinical study team.
Prosensa is now in a position to decide on the best path forward for drisapersen, based on the
results of the analysis of the drisapersen studies, which is still ongoing. Prosensa will be receiving
the full drisapersen data set under the terms and conditions of the agreement, and we will work
continuously to make an assessment on these data internally and determine a path forward for
drisapersen in a timely manner. We will continue to work closely with patient groups, investigators,
academia and regulators to ensure an optimal outcome for all of our DMD programs. As soon as we
have additional clarity on the dataset and the path forward for drisapersen, we will communicate
this. The work that we do and will continue to do will hopefully bring us one step closer to finding
the right treatment options and bring these to patients.
Prosensa will be hosting a patient focused webinar at 8 AM ET/2 PM CET on Tuesday January 21,
2014 to discuss the data we have seen thus far. Details of the webinar can be found in the
“Investors & Media” Section of the Prosensa website under “Events.”
Your selfless contribution to the study of DMD has enabled us to cultivate the largest global dataset
to date for DMD, which will hopefully assist in expediting drug development for this disease. With no
disease modifying therapies currently available for patients with DMD, it is of critical importance to
work to advance possible treatment options for these courageous boys and their families. We
remain committed to working with experts in the field to accomplish this essential goal. Our primary
focus remains with these patients and their families and we will continue to work on ways to enable
them a brighter future.
We are humbled by the overwhelming support we have received from the patient community at large and express our sincerest gratitude for all of the encouragement and assistance your organization has provided to families.
Giles Campion, MD – Chief Medical Officer and SVP Research &DevelopmentClaire Leyten, PharmD – Manager Patient Group Relations