CHM trial enrolment complete

October 2019: Biogen announced the successful enrolment of 170 patients to their phase 3 clinical study assessing gene therapy product, timrepigene emparvovec (BIIB111/ NSR-REP1), marking a significant milestone in the treatment of choroideremia. Read their community statement and listen to their recording below to learn more about what this means for the choroideremia community.


Dear members of the choroideremia community,

We’re excited to share with you that we have achieved a critical step in the development of a potential treatment option for individuals with choroideremia (CHM).

The last patient has been enrolled in our pivotal Phase 3 clinical study STAR (NCT03496012) evaluating timrepigene emparvovec (BIIB111/ NSR-REP1), an investigational gene therapy product, for the treatment of CHM. We’re incredibly grateful for the 170 individuals who chose to participate in this global clinical trial.

If the results of this study are positive and a favorable safety profile is demonstrated, we hope to submit marketing applications (BLA) to global regulatory agencies, including the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA). Typically, it takes regulatory agencies approximately one year to evaluate a marketing application once it’s been submitted and accepted for review before they will make an approval decision. In consideration of the existing unmet medical need for this rare genetic condition, Biogen will utilize accelerated regulatory pathways where permissible and as appropriate to potentially expedite review.

For those who may be unfamiliar, timrepigene emparvovec is designed to deliver healthy copies of the REP-1 gene to affected cells within a portion the retina. This therapeutic approach is thought to result in the slowing of the progression or further advancement of CHM and the associated decline in vision.

The STAR study was initiated based on compelling early stage studies, which showed a trend at 24-months in increased maintenance of visual acuity compared to a decline in best corrected visual acuity (BCVA), which is expected in this degenerative disease. A subset of patients also achieved a clinically meaningful improvement in BCVA, warranting further investigation of timrepigene emparvovec in this disease.

Again, we extend our appreciation to those who trusted the science behind this potential therapy and elected to participate in this trial.

As part of our commitment to people living with rare, inherited retinal disorders, we will continue to provide regular updates on the progress of our ophthalmology clinical development programs.

For more information or resources, please reach out to



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